CHAPTER 12 PRODUCTIVITY - Bryophyte Ecology - Michigan ...

CHAPTER 12 

PRODUCTIVITY 

Figure 1. Pohlia wahlenbergii var. glacialis, a wetland moss that is among the more productive of the acrocarpous mosses. Photo 

by Michael Lüth. 

Productivity 

It is within the framework of productivity that 

bryophytes are often considered unimportant as 

components of the ecosystem. As Martin and Adamson 

(2001) have pointed out, the photosynthetic capacity of 

mosses is generally considered to be much lower than that 

of the tracheophytes. However, they contend that this may 

be a misleading conclusion based on the method of 

calculating rates of net CO2 uptake. Rather, they 

demonstrate that when productivity of bryophytes is 

calculated on the basis of chlorophyll, differences in rate 

disappear. It is only when dry mass is used to calculate 

productivity that bryophytes appear to have a much lower 

productivity rate than that of tracheophytes. 

Ecological Factors 

Ability to Invade 

There are so many ways in which to measure 

productivity that one must be careful to consider the 

purpose for which it is being measured. If it is measured to 

determine how soon it will grow enough to overtake the 

pebble path through the garden, a consideration of the 

linear growth of the stem pointed in that direction is most 

relevant. But if it is to determine what that particular 

species is capable of doing, in its own right, we would look 

at it quite differently, most likely at its biomass gain or CO2 

fixed on an hourly or annual basis. And if we want to 

know how soon it will fill in as ground cover, we need to 

know its lateral growth – the growth of its branches as well 

as its main stem. But it is even more complex than that. 

New plants could arise from gemmae or fragments, 

requiring yet other measurements. 

These measures are not easily convertible. For 

example, Gerdol (1996) expressed the linear growth of 

Sphagnum magellanicum as 28-31 mm during the growing 

season, giving a sense of its ability to add to the depth of 

the peatland. Its dry matter production, however, was 12- 

13 mg per plant, giving us less of a mental picture of what 

effect it has on the ecosystem appearance. Does this latter 

measure reflect new capitula? How much has it increased 

the mat vertically? Despite these questions, for a peatland 

harvester, the biomass increase is of more value than the 

height of the plant. 

1

2 Chapter 12: Productivity 

Niche Differences 

Conditions that favor one species of bryophyte may be 

detrimental to another. This permits the slow-growing 

bryophytes to co-exist for a long time, with one species 

advancing more in one year and the other advancing more 

in another (Zhang . Arscott et al. (2000) demonstrated this 

with their 13-year experiment in two Arctic streams. An 

increase in phosphorus caused little difference in the 

clump-forming Schistidium agassizii (Figure 2), whereas 

the formerly rare mat-forming species of Hygrohypnum 

(Figure 2) increased rapidly. Furthermore, Hygrohypnum 

species had greater tolerance to elevated temperatures 

(>20ºC) than did S. agassizii, whereas the latter recovered 

easily from desiccation, while Hygrohypnum was 

susceptible to damage. 

Figure 2. Upper: Hygrohypnum ochraceum forming mats. 

Lower: Schistidium agassizii forming clumps. Photos by 

Michael Lüth. 

Growth 

Growth is one measure of productivity, but it has two 

components: biomass gain and increase in length 

(including branches). As Schwinning (1993) pointed out, 

unequal growth rates within a species can result from 

environmental and other factors independent of the 

productivity. She attributed these unequal rates to genetic 

differences, site differences, and competition (both infraand 

interspecies). 

Growth Measurements 

Growth measurement is never easy in a non-linear 

subject such as a pleurocarpous moss. For example, 

several authors (Rincon & Grime 1989; Zechmeister 1995; 

Stark et al. 2001) have concluded that measuring stem 

elongation only may provide an inaccurate picture of true 

productivity. In fact, biomass accumulation and shoot 

elongation are uncoupled events and biomass is a better 

predictor of productivity than is elongation (Stark 2002). 

As a result, the methods used for measuring bryophyte 

growth are varied, each having its own purpose for a 

particular growth habit. 

In larger, perennial mosses it is possible to determine 

growth because the plant provides natural markers (innate 

markers of Russell 1988; Figure 3). In their seminal papers 

on phenology of bryophytes, Longton and Greene (1969a, 

b) estimated annual growth rates using attached cotton 

markers to measure each stem, measuring distances 

between innate markers (inflorescence position), and 

measuring the length of the green apical portion of the 

stem. Hagerup (1935) used the alternating leaf sizes of 

taxa such as Ceratodon purpureus to measure annual 

growth. 

Figure 3. Left: Alternating regions of large and small 

leaves illustrating natural markers of growth on a species of 

Bryum, based on Hagerup (1935). Right: Hylocomium splendens 

– arrows indicate region markers for a new season of growth. 

Drawings by Margaret Minahan. 

In others, such as Philonotis fontana (Figure 4) and 

Aulacomnium palustre, innovations (new branches just 

below the apex) often mark new growth, but the first leaves 

of new growth also cause a constriction compared to the 

smaller (or larger) leaves ending the previous growing 

season. In other taxa, there is a wider spacing of the leaves 

at the beginning of each new season, again causing a clear 

demarcation between years. 

Figure 4. Philonotis calcarea showing multiple innovations 

just beneath the antheridial splash cup. Photo by Michael Lüth. 

In males of Polytrichaceae and others, new growth can 

arise from a splash cup so that one can trace back through a

series of splash cups to measure growth (Figure 5). These 

various interruptions are useful in many of the acrocarpous 

moss taxa and at least some leafy liverworts. In 

pleurocarpous taxa, a new set of branches may arise, 

providing a marker, as is most exquisitely exhibited in the 

stair-step moss, Hylocomium splendens (Figure 3). But 

these markers tell us only the total growth for the year, and 

not the season of growth, and in many pleurocarpous 

mosses, more than one set of branches can arise in a single 

year, as in Fontinalis (Glime 1982). 

Figure 5. Polytrichastrum showing new growth from splash 

cups (arrows). Photo by Michael Lüth. 

Changes in color can demarcate the growth of the 

current season, but these are difficult to discern for more 

than one year (Figure 6). 

Figure 6. Polytrichum commune showing change in color 

from dark green to light green where the current year's growth 

begins. Photo by Michael Lüth. 

Hawes et al. (2002) determined the ages of mosses in a 

lake bed of the Canadian High Arctic by using annual 

growth bands. These bands were 10-30 mm in length and 

were apparent due to changes in leaf density and size. The 

most recent growth provided four - five bands with 

recognizable leaves and measurable concentrations of 

chlorophyll a. Another twelve bands were recognizable 

from leaf scars. However, their attempt to correlate effects 

of ice cover with growth in a given year failed, and they 

suggested that the relationship of ice cover to growth (and 

growth bands) was more complex. 

Russell (1988) described eight methods for measuring 

growth (Figure 7), including innate markers. The cranked 

Chapter 12: Productivity 3 

wire technique is commonly employed for Sphagnum, but 

suffers from the problem of compaction of the mat, 

particularly as a result of snow, thus underestimating 

growth, particularly for more than one year. Tags can be 

used to mark a specific point on the moss from which 

future measurements are taken, but one must be careful not 

to injure the stem or interfere with water movement. A 

modification of this method works well for Fontinalis and 

other aquatics (Glime 1980, 1982); narrow strips of white 

velcro are placed around the stem as markers (black velcro 

seems to have a toxic dye); for terrestrial mosses, the velcro 

may interfere with water transport, spacing, and drying. 

Figure 7. Methods usable for measuring bryophyte shoot 

extension growth. Left figure of each pair represents the starting 

condition and time; right figure represents end of measuring 

period. Modified from Russell (1988). 

Nets placed over the mosses (Figure 7) likewise 

provide a starting point for measurements but suffer 

problems similar to the compaction problems with the 

cranked wire, although generally it is the older parts that 

get compacted most. Vital stains that are not water soluble 

can serve as markers, including fluorescent dyes and 

powders; these must be selected not to interfere with 

photosynthesis or alter nutrient concentrations. Bags 

constructed of nylon mesh can be used to mark a starting 

point, with an initial measurement of the protruding stems. 

Russell (1988) recommends cutting the stems to a known 

length and putting them in the bag, neatly arranged upright; 

note that this is a flat bag, and the growing tip should not 

be removed. Gremmen et al. (1975) and Russell (1984) 

used a coring method in which they cut horizontally 

through the soil beneath the bryophytes, then spread small 

pieces of polystyrene pellets or other marker before


replacing the moss, thus providing a marker from which to 

measure. This method could again suffer from compaction 

problems, depending on the species of bryophyte. 

Photography can give rates of advancement of a colony 

but cannot provide details of growth and provides only 

horizontal growth, not vertical assessment. Similarly, 

sheets of clear plastic can be placed over the moss patch 

and outlines drawn for future comparison. Zhang (1998) 

used the latter method to show that location of moss 

patches on the forest floor is quite dynamic. 

Growth rates may include only the dominant stem, or 

the sum of all the branches as well. Smith (1982) found 

that the epiphytic Isothecium myosuroides (Figure 8) in 

England never grew more than 16 mm per year. In an even 

drier habitat, on dry, exposed, granite ledges in 

northwestern Ontario, Vitt (1989) measured a yearly 

growth rate of 2.3-3.1 mm yr -1 for Racomitrium 

microcarpon. Vitt (1990) also measured growth as lateral 

expansion of a clone. In clumps of Pylaisiella polyantha 

on the bases of poplars, the yearly increase was about 6-8 

mm yr -1 . 

Figure 8. Isothecium myosuroides on tree. Photo by 


Biomass measurements for living bryophytes are often 

meaningless because of their tremendous ability to 

sequester water, not only internally but also externally. 

Wet mass can be up to 20 times the dry mass of Sphagnum, 

making any wet mass measure meaningless for comparison 

purposes. Drying the moss, however, creates a new 

variable that necessarily terminates the experiment and may 

therefore not be practical. Furthermore, dry mosses can 

gain sufficient atmospheric moisture to show measurable 

mass gain during the short time required to weigh them 

(personal observation). In cases where light availability is 

the same for all members of a population, biomass and 

growth in length can be correlated and either might be 

chosen as a measure of productivity, depending on the 

goals of the study. 

Annual Length Increase 

Length increase is generally related to growth form, 

with acrocarpous mosses exhibiting slow rates of growth in 

length compared to pleurocarpous mosses (Table 1). The 

pleurocarpous taxa further increase their biomass by 

development of new branches, creating an exponential 

growth pattern. Among these pleurocarpous bryophytes, 

some can become very long and have high growth rates, 

with some Fontinalis (Glime 1987b) and Sphagnum species 

growing 400 mm in a season. Taxiphyllum barbieri (Java 

moss, often mistakenly called Vesicularia dubyana) can 

quickly fill a 50 gallon aquarium through extensive 

branching and length gain. 

On Signy Island in the Antarctic, the upright 

Polytrichum strictum grows 2-5 mm, whereas at Pinawa, 

Manitoba it grows 15-55 mm per year, exhibiting 

differences due to microclimate and habitat (Longton 1974, 

1979). Pitkin (1975) showed wide variation in growth of 

Hypnum cupressiforme, depending on its height on the tree 

trunk, with mm of growth at 30-100 cm above ground 

doubling that at 150-200 cm from 23 May to 6 October. 

Not surprisingly, growth of the upper side of a sloping 

trunk was more than double that on the lower side. 

Table 1. Comparison of growth in length of various mosses from a variety of locations and habitats. 

Species mm yr -1 Location Reference 

Forsstroemia trichomitria 3.85-4.45 Virginia Stark 1986 

Calliergon 10-30 Arctic Hawes et al. 2002 

lake species 10 Canadian Arctic Sand-Jensen et al. 1999 

Leucobryum glaucum 9.1 S. England Bates 1989 

Meesia triquetra 3.7-14.8 Devon Island Vitt & Pakarinen 1977 

Ptilidium pulcherrimum 3.5-6.3 N. Sweden Jonsson & Söderström 1988 

Sphagnum magellanicum 28-31 S. Alps, Italy Gerdol 1996 

Sphagnum papillosum 33 Gaberscik & Martincic 1987 

Sphagnum spp. 4-24 northern Quebec Moore 1989 

Polytrichum strictum 2-5 Antarctic Longton 1979 

Polytrichum strictum 15-55 1 Pinawa, Manitoba, Canada Longton 1979 

Fontinalis duriaei 400 (incl branches) N. Michigan Glime 1987a 

Rhynchostegium riparioides 33.4-73.3 streams, Northern Pennines, England Kelly & Whitton 1987 

Racomitrium lanuginosum 5.4-6.7 Marion Island Russell 1984 

Racomitrium lanuginosum 2.3 Mt Fuji Nakatsubo 1990 

Racomitrium lanuginosum 5-15 England Tallis 1959, 1964 

Racomitrium microcarpon 2.3-3.1 NW Ontario Vitt 1989

Uncoupling 

In bryophytes, as in some other plants, the increase in 

height/length may not be well correlated with increase in 

biomass. For example, in loblolly pine, branching becomes 

denser in low-density populations, but in high-density 

populations the trees grow taller. Likewise, self shading or 

other causes of low light cause elongation without a 

concomitant gain in biomass, as illustrated by grass 

elongation under a board on your lawn. A more interesting 

phenomenon is that biomass increases and elongation may 

not occur at the same time. Rincon and Grime (1989) 

showed very clearly that growth in length and increase in 

biomass of Brachythecium rutabulum, Thuidium 

tamariscinum, and Lophocolea bidentata may be almost 

inverse relationships. When dry matter production 

declined, there was an increase in length, causing a 

negative biomass production (Figure 9). This, however, is 

not true for all species, as seen by Plagiomnium undulatum 

and Pseudoscleropodium purum (Figure 9). 

The uncoupling of growth in length with that of 

branches is not surprising. As branches elongate, more 

distance is available for branch buds to form. In 

Leptodictyum riparium, total growth and growth of 

branches increase together (Sanford 1979). The rate of 

main axis growth, on the other hand, decreases as the rate 

of branch growth increases. 

Figure 9. Comparison of relative growth rates in length and 

dry matter production in five bryophytes from calcareous 

grasslands. Redrawn from Rincon & Grime (1989). 

At least in Sphagnum, this uncoupling seems to be 

reflected in seasonal carbohydrate content as well 

(Shiraishi et al. 1996). In the Hakkoda Mountains of 


Japan, the glucose content of three Sphagnum species was 

highest in summer. Shiraishi et al. (1996) attributed this to 

an uncoupling between the active periods of matter 

production and growth. Sucrose, however, peaked in 

autumn in S. papillosum and S. nemoreum, presumably in 

preparation for winter, and the seasonal changes were 

different between these two hummock species and S. 

tenellum, a hollow species. 

Gaberscik and Martincic (1987) likewise found that 

net photosynthesis did not correlate with growth. In 

August, when photosynthesis was maximal, biomass 

accumulation actually decreased. Chlorophyll content 

correlated positively with this period of high net 

photosynthesis, and consequently did not correlate with 

growth. Rather, the most intensive dry mass increase was 

at the beginning of the growing season. Winter was a low 

period for both photosynthesis and growth. 

Seasonal Differences 

We have assumed maximum growth of most temperate 

bryophytes to be in the spring when moisture is usually 

abundant and temperatures are cool. In their study of 

standing crops, Al-Mufti et al. (1977) supported this 

premise, showing that the peak standing crop in bryophytes 

occurred in May, the culmination of spring growth, and 

again in December, following cooler and more moist 

weather of autumn. The lowest biomass was in August 

when bryophytes would have suffered respiratory loss in 

the heat of summer. Zotz and Rottenberger (2001) likewise 

found this for three moss species [Grimmia pulvinata 

(Figure 10), Schistidium apocarpum, Syntrichia ruralis] on 

an exposed limestone wall in temperate Europe, with a 

strong seasonal pattern showing highest carbon fixation in 

autumn and near zero in summer. 

Figure 10. Grimmia pulvinata showing white awns that are 

common among xerophytic bryophytes. Photo by Michael Lüth. 

However, we need more field studies to corroborate 

this assumption of spring growth on a broad scale. Growth 

in bryophytes has been difficult to measure because it is 

slow and increments are small, with yearly increments 

measuring in mm in many taxa. 

Kershaw and Webber (1986) approached the seasonal 

behavior from a different angle, showing that in a forest 

habitat, chlorophyll was highest in Brachythecium 

rutabulum in summer when light intensity was lowest.


Low light, coupled with high temperatures, contributes to 

low summer productivity. 

In a temperate, semi-arid, sandy grassland, Syntrichia 

ruralis was strongly dependent on its microclimatic 

conditions and followed the same general principles I have 

suggested (Juhász et al. 2002). Its highest productivity, 

however, was in December and January, with carbon gain 

beginning in October. It was dormant throughout the hot, 

dry summer. In a different study where the temperate 

grassland had cover provided by Juniperus communis 

shrubs, those species that occurred in the open exhibited a 

decline in photosynthetic efficiency from the humid spring 

to the hot, dry summer and exhibited lower efficiency 

(Fv/Fm) than those bryophytes growing in the shade of the 

shrubs (Kalapos & Mázsa 2001). 

But not all habitats create such pronounced seasonal 

differences. In the subarctic, Dicranum fuscescens 

exhibited no clear seasonal differences in daily CO2 uptake, 

nor were there any apparent differences between lowland 

and highland sites (Hicklenton & Oechel 1977). Melick 

and Seppelt (1994) found no seasonal differences in 

carbohydrates levels in continental Antarctica, although 

chlorophyll levels did decrease during winter. One reason 

for this apparent lack of seasonality is the high degree of 

daily variation that is experienced by bryophytes in Arctic 

and Antarctic areas. 

Nevertheless, seasonal water availability can impose 

seasonal differences, even in these northern regions. In 

peatland habitats, productivity may respond to greater 

water availability in summer, but decrease if the moss 

becomes submerged (Suyker et al. 1997), increasing again 

as they achieve greater CO2 exchange with receding water. 

Skré and Oechel (1981) demonstrated, in their two years of 

study of the Alaskan taiga, that increased amounts of 

young, photosynthetically active tissue near the end of the 

growing season in the mosses Polytrichum commune, 

Pleurozium schreberi, Hylocomium splendens, and 

Sphagnum subsecundum accounted for their highest 

maximum net photosynthesis occurring in August. 

Williams and Flanagan (1998) reported maximum 

photosynthetic rates of Sphagnum in summer (14 µmol m -2 

s -1 ) compared to spring (5 µmol m -2 s -1 ) and autumn (6 

µmol m -2 s -1 ). In the same habitat, however, Pleurozium 

schreberi had no seasonal variation, with mean rates of 7, 

5, and 7 µmol m -2 s -1 during spring, summer, and autumn, 

respectively. 

Asada et al. (2003) showed that winter growth was 

important for the Sphagnum species in the hypermaritime 

coastal peatland of British Columbia, Canada. Position in 

the hummock seemed to be important, with lower 

productivity on the hummocks than in the hollows, again 

emphasizing the importance of water availability. 

In the maritime Antarctic, respiration in 

Brachythecium is highest in summer and lowest in winter, 

regardless of temperature, whereas in Chorisodontium and 

Andreaea, there is little difference, perhaps relating to their 

drier habitats (Davey & Rothery 1996). Photosynthesis 

rates are generally higher in summer. The optimum 

temperature for photosynthesis does not change between 

summer and winter. 

Etiolation 

Elongation can be misleading. Low radiation causes 

greater elongation, with the highest elongation in Dicranum 

majus (Figure 11) from various polluted areas occurring at 

the lowest irradiance (20 µM m -2 s -1 ) (Bakken 1995). 

Etiolation (excessive elongation and loss of chlorophyll 

due to insufficient light) can easily be observed if mosses 

are collected fresh, then put into a sealed plastic bag and 

stored in a nearly dark place. More on this phenomenon is 

discussed in the chapter on light. 

Figure 11. Dicranum majus exhibiting a large plant size 

typical of low light conditions. Photo by Michael Lüth. 

Belowground Productivity 

It is rather presumptuous to title anything related to 

bryophytes as "Belowground Productivity" because data 

reporting such values are woefully lacking. Yet, 

bryophytes have rhizoids, and much of that biomass exists 

below ground, so such a title is not absurd. Furthermore, 

bryophytes have underground rhizomes, particularly in the 

Polytrichaceae. Sveinbjörnsson and Oechel (1981) have 

shown the respiration in the rhizome relative to whole plant 

CO2 gain (Figure 12). Nevertheless, this is but an indirect 

indication that biomass is in place and active there with no 

indication of the carbon needed to put it there. 

Figure 12. Relationship of aboveground and belowground 

CO2 flux in Polytrichastrum alpinum and Polytrichum commune 

in the Alaskan tundra. Redrawn from Sveinbjörnsson & Oechel 

(1981).

Sporophyte Productivity 

A discussion of the ability of the sporophyte to carry 

out photosynthesis is in Chapter 2-7, Bryopsida, and in 

Chapter 5-9, Ecophysiology of Development: Sporophyte. 

We know that bryophyte sporophytes have chlorophyll, 

even in thallose liverworts (Bold 1948), but few 

independent measurements of their rates of productivity 

seem to exist. These are further complicated by the 

photosynthetic capacity of the spores inside. 

Nevertheless, Paolillo and Bazzaz (1968) demonstrated 

in Funaria and Polytrichum that the shape of the light 

saturation curve of the sporophyte is close to that of the 

gametophyte. For Polytrichum, the weight of the 

gametophyte decreases as that of the sporophyte increases 

and there is no net photosynthetic gain by the sporophyte, 

but such is not the case in Funaria. In Funaria, there is a 

net photosynthetic gain. In Funaria the calyptra is perched 

at the end of the capsule and covers little of it, whereas in 

Polytrichum the capsule is completely covered (Figure 13). 

The authors conclude that the seta serves as a reservoir for 

the developing capsule. 

Figure 13. Left: Polytrichum calyptra covering capsule 

completely. Photo by Janice Glime. Right: Funaria calyptra 

covering only the end of the capsule. Photo by Michael Lüth. 

Productivity and Aging 

The current year's tissues seem to be the primary site 

of photosynthesis for most mosses. Collins and Oechel 

(1974) found that early in the season, the photosynthesis of 

Alaskan mosses relied on tissues produced the previous 

year, or even previous two years, but those rates were 

lower than for tissues produced in the current year (75% 

and 40% for 1 and 2 years earlier, respectively). Callaghan 

and coworkers (1978) found an even greater reduction in 

Swedish Lapland mosses. One-year-old tissues had rates 

55% lower in Hylocomium splendens and 58% lower in 

Polytrichum commune than those tissues produced in the 

current year. 

Life Span 

We have expressed productivity in measurements from 

seconds to annual, but in consideration of the ecosystem, it 

is also appropriate to speak in terms of a lifetime. 

Although our knowledge of life spans is still meager, we do 

have indications in some species, although they may be 


minimal rather than maximal ages. For example, Frye 

(1928) found specimens of Stokesiella oregana that were 

up to six years old. Ulychna (1963) reported mean ages for 

Polytrichum commune of 3-4 years, with dead parts of 15- 

17 years age, although if they were not growing in 

hummocks the dead parts seemed to be only 4-5 years old. 

Corollary to the importance of life span is the effect 

that age has on growth rate. Ulychna (1963) found no 

effect in Hylocomium splendens or Polytrichum commune. 

In the same two species, Callaghan et al. (1978) found that 

Hylocomium splendens grows its fronds for two years, then 

produces new segments, a factor that would be misleading 

in determining its age by its branching. Other factors can 

mislead age determinations based on growth markers. 

Polytrichum commune continues to have photosynthesis in 

dry conditions, whereas H. splendens ceases. 

New growth may keep pace with dying portions 

(Callaghan et al. 1978). In Hylocomium splendens, 

normally the new shoot replaces the decomposing distal 

portion, but if the young segment is damaged, the whole 

shoot dies. On the other hand, Polytrichum commune has a 

finite life expectancy which may differ with geographic 

area, but it also has an underground proliferation that can 

give rise to new shoots and compensate for lack of 

branching and death of aboveground parts. 

In the maritime Antarctic, Polytrichum strictum 

(Figure 14) can have the extremely high annual mortality 

rate of 32% in young turfs (Collins 1976). However, in 

pure older turfs it is closer to 13%. 

In the Arctic, longevity may compensate for the slow 

growth rates. Sand-Jensen et al. (1999) found that the 

slow, but steady-growing lake bottom mosses could persist 

for up to 17 years, retaining green leaves for several years, 

and decomposing slowly. Their growth rate, however, was 

only 10 mm per year, a relatively slow rate compared to 

pleurocarpous aquatic mosses elsewhere. 

Figure 14. Polytrichum strictum illustrating the protection 

plants give each other in older tufts. Photo by Michael Lüth. 

Leaf Production and LAI 

Vitt (1990) decided to investigate the number of leaves 

and other leaf parameters that have been ignored for 

bryophytes. He did this to illustrate the complexity of moss 

populations, a fact usually not realized by most ecological 

observers. Using Drummondia prorepens, a small moss 

with large leaves, he found about 90 stems per cm 2 . The


stems averaged ca. 65 leaves each, resulting in 6000 leaves 

per cm 2 . Considering the available leaf for photosynthesis, 

he determined that one cm 2 has ~15 cm 2 of photosynthetic 

moss surface. 

The leaf area index has been used to express the 

relationship of the leaf-to-light interception (Smith 1990). 

It is the ratio of the leaf area to ground area, using the same 

units. Thus, a low LAI indicates wasted sunlight. A value 

of 1 indicates full usage, and a value of greater than 1 

permits maximum usage at more angles of the sun. Since 

bryophyte leaves generally are not perpendicular to the sun, 

a higher LAI is required to obtain the same amount of light. 

Simon (1987) estimated LAI measurements on 

Syntrichia ruralis, with 2030 leaves cm -2 , and Ceratodon 

purpureus, with 27,966 leaves cm -2 . These had leaf area 

indices (LAI) of 44 and 129 respectively. We can state the 

LAI for Drummondia prorepens, based on Vitt's (1990) 

data, as 15, discounting the portion of the leaf that is nonphotosynthetic. 

Vitt (1990) reported a mean leaf area of 

1960 mm 2 cm -2 (LAI = 19.6) for mosses in the boreal 

biome. 

Table 2. Comparison of biomass devoted to photosynthesis vs storage and respiration for plants from major biomes. From Larcher 

(1983) and compiled from many sources. 

Plant Green mass Purely respiratory organs 

(photo- 

synthetically Woody stems Roots and 

active organs) above ground subterranean 

shoots 

Evergreen trees of tropical ca. 2% 80-90% 10-20% 

and subtropical forests 

Deciduous trees of the 1-2% ca. 80% ca. 20% 

temperate zone 

Evergreen conifers of the taiga 4-5% ca. 75% ca. 20% 

and in mountain forests 

Alpine scrubwood ca. 25% ca. 30% ca .45% 

Young conifers 50-60% 40-50% ca. lo% 

Ericaceous dwarf shrubs 10-20% ca. 20% 60-70% 

Grasses 30-50% 50-70% 

Steppe plants 

Wet years ca. 30% ca. 70% 

Dry years ca. 10% ca. 90% 

Desert plants 10-20% 80-90% 

Arctic tundra 

Tracheophytes 15-20% 

Cryptogams (including bryophytes) >95% 

Plants of the high mountains 10-20% 80-90% 

Energy Content 

One distinction among plants is the amount of their 

tissue used for storage vs that used for photosynthesis. In 

this regard, the bryophyte uses nearly all of its tissue for 

photosynthesis, although I question whether it is as high as 

the 95% shown in Table 2. Using the category of 

cryptogams includes the lichens, club mosses, horsetails, 

and ferns, complicating the interpretation of the number. 

Fungal Partners 

Although most bryophytes are self-reliant, 

photosynthetic organisms, some do benefit from fungal 

partners. The achlorophyllous thallose liverwort 

Cryptothallus mirabilis (Figure 15) relies totally on an 

endophytic fungus for its carbon input (Ligrone et al. 

1993). The fungus is associated with the bases of the 

rhizoids and does not penetrate the thallus. There is no 

evidence that a third partner is involved; associated trees 

have a different fungal partner. Rather, it most likely gains 

its carbon from the organic nutrients in the soil and litter. 

Its dependency on this fungal carbon source is supported by 

its failure to develop beyond a few cells in sterile culture. 

Figure 15. Cryptothallus mirabilis, an achlorophyllous 

thallose liverwort. Photo by Michael Lüth. 

In Aneura pinguis (Figure 16; Ligrone et al. 1993), 

Conocephalum conicum (Ligrone & Lopes 1989), and 

Phaeoceros laevis (Ligrone 1988), it appears that it is the 

fungus that benefits, not the liverwort.

Figure 16. Aneura pinguis, a thallose liverwort. Photo by 


Recent History 

Previous conditions have a strong influence on the 

photosynthetic performance of plants, at least among some 

Alaskan mosses (Alpert & Oechel 1987). Assemblages of 

mosses having recent experience with low water 

availability achieved maximum net photosynthesis at lower 

water contents than did those that had remained hydrated. 

Likewise, those mosses that occurred in sites with low light 

availability achieved higher net photosynthesis at lower 

light intensities than mosses that had recent history in high 

light intensities. And a close relationship exists between 

the lower temperature limit for 85% photosynthesis and the 

mean maximum tissue temperature for the previous fiveday 

period (Oechel 1976). 

Recent history most likely accounts for the 

considerably lower productivity in spring, compared to 

summer, in Atrichum undulatum, Plagiomnium affine, and 

Polytrichum formosum (Baló 1967). One reason for this is 

the much higher chlorophyll a content in summer, 

compared to spring. Such previous histories can account 

for much of the variation we see between measurements of 

the same species and even the same individuals. 

Mitotic Activity 

It appears that mitotic activity, the initial step in new 

growth, has its own clock. In a study on Pellia borealis, a 

thallose liverwort, the greatest activity occurs between 

11:00 and 14:00 hours (Szewczyk 1978). However, further 

studies are needed to determine if this is an endogenous 

rhythm or is tied to a daily ecological event in its habitat. 

Respiration 

Nearly every photosynthetic study includes respiration 

measurements. However, these may not be reported 

separately. Net photosynthesis is that incorporated carbon 

that remains after carbon is lost as CO2 in respiration. 

Bryophytes, as C3 plants, exhibit both dark respiration 

and photorespiration. Photorespiration is difficult to 

measure because of the ability of a plant to put that same 

lost CO2 immediately back into carbohydrate through the 

photosynthetic pathway. Photorespiration in C3 plants is 

generally up to three times greater than dark respiration and 

accounts for the loss of energy at high temperatures. But 

even dark respiration increases in summer, as noted in 

Plagiomnium acutum and P. maximoviczii in China (Liu et 

al. 2001). 


Davey and Rothery (1996) found respiration in 

Brachythecium in the maritime Antarctic was highest in 

summer and lowest in winter at all temperatures, whereas 

Chorisodontium and Andreaea exhibited little change. 

Priddle (1980b) found that the dark respiration of two 

Antarctic species of aquatic mosses (Calliergon 

sarmentosum and Drepanocladus sp.) differed little from 

that of the algal communities in the same lake. At normal 

lake temperatures (up to 5ºC), the mosses respired 

approximately 0.3 g mg -1 ash-free dry mass h -1 . 

In the high Arctic Svalbard, Sanionia uncinata exhibits 

a high Q10 (ratio of reaction rates for a 10ºC rise) of 3 for 

respiration in the range of 7-23°C (Uchida et al. 2002). In 

the same range, photosynthesis exhibits very little 

difference, resulting in low temperature optima. 

Habitat and Geographic Comparisons 

Because of the length of the growing season, 

temperatures during the growing season, day length, 

available water, and other geographic and climatic factors, 

productivity in various biomes differs. Table 3 compares 

the various biomes to provide a framework for the 

discussion of habitat differences among bryophytes. Table 

4 and Table 5 compare rates on biomass and area bases, 

respectively. 

Although water may be a good indicator of 

productivity of a habitat, the general water availability of 

the habitat is not a good indicator of the productivity at the 

time that water is available. In fact, the relationship seems 

to be inverse. As can be seen in Table 3, the highest 

productivity seems to be from the driest habitats and from 

the plants adapted to those habitats. On the other hand, 

Suba et al. (1982) found that hygrophytic and mesophytic 

mosses of a beechwood community had more 

photosynthetic intensity than more xerophytic rockinhabiting 

mosses. History is probably important here. 

In the boreal forest, it appears that the light use 

efficiency of Pleurozium schreberi (102 mM CO2 M -1 ) is 

well above that of most of the plants there (70-80 mM CO2 

M -1 ), but its productivity is still lower (1.9 µM m -2 s -1 

(Whitehead & Gower 2001). Other understory shrubs and 

herbaceous plants had productivity mostly between 9 and 

11 µM m -2 s -1 . 

For aquatic bryophytes, depth affects light intensity. 

Growth rates of deepwater mosses can be quite slow (10 

mm per year in Canadian High Arctic lakes), and vary little 

between years (Sand-Jensen et al. 1999). Martínez Abaigar 

et al. (1994) found that Scapania undulata had a leaf 

specific area of 317 cm 2 g -1 DM at 5 cm depth, but at 45 cm 

depth, the LSA increased to 399 cm 2 g -1 DM. 

Concomitantly, the leaf specific weight (mass) was reduced 

from 3.16 mg cm -2 to 2.50 mg cm -2 . These differences can 

be interpreted as a response to the lower light availability at 

45 cm. Canopy leaf fall, on the other hand, caused an 

increase in accessory pigments relative to chlorophyll a. 

Furness and Grime (1982) found that species of 

disturbed habitats (ruderal species) such as Funaria 

hygrometrica had high relative growth rates, as did 

perennial pleurocarpous species such as Brachythecium 

rutabulum from fertile habitats. Most species grew best at 

temperatures of 15-25°C, whereas temperatures above 30ºC 

eventually killed moist mosses.


Rates of Productivity 

Productivity varies with habitat (Table 3). Mosses, 

typically living in shaded habitats, are low in productivity 

compared to other plant groups (Table 6). In the Antarctic, 

Davey and Rothery (1996) found greater seasonal variation 

in bryophytes from hydric habitats than from the less 

hydric sites. 

Probably the highest productivity ever measured for a 

bryophyte is that of Sphagnum, with a productivity of 12 

tons per hectare per year (Schofield 1985). C4 plants 

average a CO2 uptake of up to 80 mg dm -2 hr -1 , whereas C3 

plants seem to have a max of about 45 (Larcher 1983). 

Mosses, on the other hand, have a max of only 3! For some 

reason, perhaps the thick cuticle and other adaptations that 

reduce the light, CAM plants have a maximum of only 20. 

However, since measurement time may not coincide with 

the period of photosynthesis, we may need to interpret 

these numbers somewhat differently. 

Table 3. Comparison of net primary production, biomass, chlorophyll, and leaf surface area in major biomes. From Whittaker et 

al. (1974); Larcher (1983). 

Leaf Surf Area 

Net Primary Production Biomass (dry matter) Chlorophyll LAI 

Normal Mean Total Normal Mean Total Mean Total Mean Total 

Area range g m -2 yr -1 10 9 range kg m -2 10 9 t g m -2 10 6 t m 2 m -2 10 6 km 2 

Ecosystem Type 10 6 km 2 g m -2 yr -1 t yr -1 kg m -2 

Tropical rain forest 17.0 1000-3500 2200 37.4 6-80 45 765 3.0 51.0 8 136 

Tropical seasonal forest 7.5 1000-2500 1600 12.0 6-60 35 260 2.5 18.8 5 38 

Temperate forest: 

Evergreen 5.0 600-2500 1300 6.5 6-200 35 175 3.5 17.5 12 60 

Deciduous 7.0 600-2500 1200 8.4 6-60 30 210 2.0 14.0 5 35 

Boreal forest 12.0 400-2000 800 9.6 6-40 20 240 3.0 36.0 12 144 

Woodland and 8.5 250-1200 700 6.0 2-20 6 50 1.6 13.6 4 34 

shrubland 

Savanna 15.0 200-2000 900 13.5 0.2-15 4 60 1.5 22.5 4 60 

Temperate grassland 9.0 200-1500 600 5.4 0.2-5 1.6 14 1.3 11.7 3.6 32 

Tundra and alpine 8.0 10-400 140 1.1 0.1-3 0.6 5 0.5 4.0 2 16 

Desert and 18.0 10-250 90 1.6 0.1-4 0.7 13 0.5 9.0 1 18 

semidesert scrub 

Extreme desert- 24.0 0-10 3 0.07 0-0.2 0.02 0.5 0.02 0.5 0.05 1.2 

rock, sand, ice 

Cultivated land 14.0 100-4000 650 9.1 0.4-12 1 14 1.5 21.0 4 56 

Swamp and marsh 2.0 800-6000 3000 6.0 3-50 15 30 3.0 6.0 7 14 

Lake and stream 2.0 100-1500 400 0.8 0-0.1 0.02 0.05 0.2 0.5 

Total continental: 149 782 117.5 12.2 1837 1.5 226 4.3 644 

Open ocean 332.0 2-400 125 41.5 0-0.005 0.003 1.0 0.03 10.0 

Upwelling zones 0.4 400-1000 500 0.2 0.005-0.1 0.02 0.008 0.3 0.1 

Continental shelf 26.6 200-600 360 9.6 0.001-0.04 0.001 0.27 0.2 5.3 

Algal beds and reefs 0.6 500-4000 2500 1.6 0.04-4 2 1.2 2.0 1.2 

Estuaries (excluding 1.4 200-4000 1500 2.1 0.01-4 1 1.4 1.0 1.4 

marsh) 

Total marine 361 - 155 55.0 - 0.01 3.9 0.05 18.0 

Full total 510 336 172.5 3.6 1841 0.48 243 

Table 4. Productivity rates for bryophytes based on bryophyte mass, ordered from most productive to least. Values refer to CO 2 

incorporated; dm refers to dry mass – if dm is not indicated, dry or wet mass is not known for certain. 

Species Productivity Value Conditions/Location Reference 

Sphagnum auriculatum 232 mg g -1 h -1 submersed at light compensation point Wetzel et al. 1985 

Rhynchostegium rusciforme 20.24 mg g -1 h -1 max; converted from mM O2 g -1 h -1 Allen & Spence 1981 

Fontinalis antipyretica 15.4 mg g -1 h -1 

max; converted from mM O2 g -1 h -1 Allen & Spence 1981 

Plagiomnium acutum 19.9 mg g -1 h -1 summer; converted from µM kg -1 s -1 Liu et al. 2001 

Plagiomnium maximoviczii 15.0 mg g -1 h -1 summer; converted from µM kg -1 s -1 Liu et al. 2001 

Plagiomnium acutum 9.20 mg g -1 h -1 winter; converted from µM kg -1 s -1 Liu et al. 2001 

Plagiomnium maximoviczii 9.86 mg g -1 h -1 winter; converted from µM kg -1 s -1 Liu et al. 2001 

Hygrohypnum spp. 2.3-8.7 mg g -1 dm h -1 Alaska stream Arscott et al. 2000 

Polytrichum formosum 8 mg g -1 dm h -1 Hungary, summer, light saturation Baló 1967 

Plagiomnium affine 6 mg g -1 dm h -1 Hungary, summer, light saturation Baló 1967 

Atrichum undulatum 5 mg g -1 dm h -1 Hungary, summer, light saturation Baló 1967 

Calliergon sarmentosum 4.4 mg g -1 dm h -1 max, Alaska Arctic tundra Oechel & Sveinbjörnsson 1978 

Polytrichastrum alpinum 4.4 mg g -1 dm h -1 max, Alaska Arctic tundra Oechel & Sveinbjörnsson 1978 

Rhytidiadelphus squarrosus 3.5 mg g -1 dm h -1 max, South Sweden Stǻlfelt 1937 

Ptilium crista-castrensis 3.4 mg g -1 dm h -1 max, South Sweden Stǻlfelt 1937 

Hylocomium splendens 3.2 mg g -1 dm h -1 max, South Sweden Stǻlfelt 1937

Table 4 (cont.). 



Sphagnum girgensohnii 3.0 mg g -1 dm h -1 Polytrichum commune 2.79 mg g 

max, South Sweden Stǻlfelt 1937 

-1 h -1 

Sphagnum balticum 2.7 mg g 

max, mature veg, Fairbanks, Alaska; moist? Skré & Oechel 1981 

-1 dm h -1 

Polytrichum commune 2.65 mg g 

subarctic mire 

Johansson & Linder 1980 

-1 h -1 

Hylocomium splendens 2.5 mg g 


-1 h -1 

Rhytidiadelphus triquetrus 2.5 mg g 

max, subarctic Finland Kallio & Kärenlampi 1975 

-1 h -1 

Sphagnum magellanicum 2.2 mg g 


-1 dm h -1 Pleurozium schreberi 2.0 mg g 

Petersen 1984 

-1 dm h -1 Pohlia drummondii 2.0 mg g 


-1 h -1 

Sphagnum papillosum 1.95 mg g 


-1 dm h -1 Sphagnum fuscum 1.7 mg g 

max, Aug Gaberscik & Martincic 1987 

-1 dm h -1 

Polytrichum juniperinum 1.6 mg g 

subarctic mire 

Johansson & Linder 1980 

-1 h -1 

Schistidium agassizii 0.59-1.6 mg g 


-1 dm h -1 

Dicranum fuscescens 0.1-2 mg g 

Alaska stream, converted from O2 to CO2 Arscott et al. 2000 

-1 dm h -1 Dicranum fuscescens 1.5 mg g 

Arctic, 10 Oct & 7 July, respectively Hicklenton & Oechel 1976 

-1 dm h -1 Pterobryum arbuscula 1.5 mg g 

max, Alaska Arctic tundra Oechel & Sveinbjörnsson 1978 

-1 h -1 

Thuidium kanedae 1.4 mg g 

max, epiphyte, Japan Hosokawa et al. 1964 

-1 h -1 

Leucobryum neilgherrense 1.4 mg g 


-1 h -1 



-1 h -1 Dicranum elongatum 1.3 mg g 


-1 dm h -1 Macromitrium gymnostomum 1.3 mg g 


-1 h -1 

Sphagnum nemoreum 1.2 mg g 


-1 dm h -1 

Ulota crispula 1.2 mg g 

lake, New York, USA 

Titus et al. 1983 

-1 h -1 

Pleurozium schreberi 1.20 mg g 


-1 h -1 1.1 mg g 


-1 h -1 


max, south Finland Kallio & Kärenlampi 1975 

-1 h -1 Dicranum bonjeanii 1.0 mg g 


-1 dm h -1 subsp angustum 


Neckera konoi 1.0 mg g -1 h -1 

Calliergon austrostramineum 1.0 mg g 


-1 h -1 

Sphagnum rubellum 0.9 mg g 

max, Antarctica Rastorfer 1972 

-1 dm h -1 Anomodon giraldii 0.9 mg g 

max, moorland Grace 1970 

-1 h -1 

Macrosporiella scabriseta 0.9 mg g 


-1 h -1 

Boulaya mittenii 0.9 mg g 


-1 h -1 

Pohlia nutans 0.9 mg g 


-1 h -1 

Dicranum elongatum 0.9 mg g 


-1 h -1 

Sanionia uncinata 0.9 mg g 


-1 h -1 

0.9 mg g 


-1 h -1 

Neckera pennata 0.8 mg g 


-1 dm h -1 Racomitrium lanuginosum 0.8 mg g 

May, Adirondack Mt. Forest on tree Tobiessen et al. 1977 

-1 h -1 

Polytrichum strictum 0.7 mg g 

max, Antarctica Kallio & Kärenlampi 1975 

-1 h -1 

Racomitrium lanuginosum 0.6 mg g 


-1 dm h -1 

Thuidium cymbifolium 0.6 mg g 

Fennoscandia tundra 

Kallio & Heinonen 1975 

-1 h -1 

Hylocomium var. brevirostre 0.6 mg g 


-1 h -1 


cavifolium 

Homaliodendron 0.6 mg g -1 h -1 


flabellatum 

Sphagnum subsecundum 0.57 mg g -1 h -1 Pleurozium schreberi 0.46 mg g 


-1 h -1 Sphagnum nemoreum 0.25 mg g 


-1 h -1 Mnium cuspidatum 0.16 mg g 


-1 dm h -1 Anomodon rugelii 

0.00 mg g 

July, Adirondack Mt. Forest on tree Tobiessen et al. 1977 

-1 dm h -1 

July, Adirondack Mt. Forest on tree Tobiessen et al. 1977 

Neckera pennata 

Ulota crispa 

no PS 

no PS 

July, Adirondack Mt. Forest on tree 

July, Adirondack Mt. Forest on tree 

Tobiessen et al. 1977 

Tobiessen et al. 1977 

Calliergon sarmentosum 6 mg g -1 dm d -1 max, Antarctica lake bottoms Priddle 1980a 

& Drepanocladus spp. 

Calliergon giganteum 48.8 mg g -1 dm d -1 

293.0 mg g 

0.03% CO2, Arctic mineral sedge marsh D’Yachenko 1976 

-1 dm d -1 

Lophozia quinquedentata 25.4 mg g 

1% CO2, Arctic mineral sedge marsh D’Yachenko 1976 

-1 dm d -1 155.2 mg g 


-1 dm d -1 

Polytrichum juniperinum 14.5 mg g 


-1 dm d -1 

87.2 mg g 

dry, 0.03% CO2, Arct mineral sedge marsh D’Yachenko 1976 

-1 dm d -1 Sphagnum squarrosum 13.0 mg g 

dry, 1% CO2, Arctic mineral sedge marsh D’Yachenko 1976 

-1 dm d -1 77.8 mg g 


-1 dm d -1 

Dicranum fuscescens 7 mg g 


-1 dm d -1 max, subarctic Hicklenton & Oechel 1977

12 Chapter 12: Productivity 

Table 5. Productivity rates for bryophytes on an area basis. Values refer to CO 2 incorporated. 


Sphagnum spp. 14 µM m -2 s -1 max, summer Williams & Flanagan 1998 

Sphagnum spp. 6 µM m -2 s -1 max, autumn Williams & Flanagan 1998 

Sphagnum spp. 5 µM m -2 s -1 max, spring Williams & Flanagan 1998 

Pleurozium schreberi 1.9 µM m -2 s -1 Canadian boreal forest Whitehead & Gower 2001 

Ceratodon purpureus 4 µM m -2 s -1 max, Langhovde, East Antarctica, 9-17 Jan Ino 1990 

& Bryum pseudotriquetrum 

Hypnum cupressiforme 0.045 g m -2 s -1 Southern Finland, 5°C Kallio & Kärenlampi 1975 

Pleurozium schreberi 0.045 g m -2 s -1 Southern Finland, 15°C (optimum) Kallio & Kärenlampi 1975 

Hydrogonium consanguinium 0.88 g m -2 d -1 July, India Munshi 1974 

Hydrogonium consanguinium 1.05 g m -2 d -1 August, India Munshi 1974 

Hydrogonium consanguinium 1.05 g m -2 d -1 September, India Munshi 1974 

Physcomitrium spp. 0.17 g m -2 d -1 December Munshi 1974 

Physcomitrium spp. 0.08 g m -2 d -1 January Munshi 1974 

Physcomitrium spp. 0.07 g m -2 d -1 February Munshi 1974 

Hydrogonium consanguinium 31.53 g m -2 mo -1 August, India Munshi 1974 

Hydrogonium consanguinium 26.60 g m -2 mo -1 July, India Munshi 1974 

Hydrogonium consanguinium 14.80 g m -2 mo -1 September, India Munshi 1974 

Physcomitrium spp. 5.13 g m -2 mo -1 December Munshi 1974 

Physcomitrium spp. 2.44 g m -2 mo -1 January Munshi 1974 

Physcomitrium spp. 2.10 g m -2 mo -1 February Munshi 1974 

bryophyte cover 754 g m -2 yr -1 Marion Island (45º54'S) drainage line Russell 1985 

Hypnum cupressiforme 188 g m -2 yr -1 Austria Zechmeister 1998 

Pleurozium schreberi 161 g m -2 yr -1 Austria Zechmeister 1998 

Abietinella abietina 144 g m -2 yr -1 Austria Zechmeister 1998 

Hylocomium splendens 129.8 g m -2 yr -1 Tamm 1953 

Hylocomium splendens 127 g m -2 yr -1 Austria Zechmeister 1998 

Sphagnum papillosum 101.0 g m -2 yr -1 moor Newbould 1960 

Hydrogonium consanguinium 

72.93 g m -2 yr -1 net production, India Munshi 1974 

Calliergon sarmentosum 40 g m -2 yr -1 max, Antarctica lake bottoms Priddle 1980a 

& Drepanocladus (sensu lato) spp. 

Sanionia uncinata 30 g m -2 yr -1 max, High Arctic, Svalbard (79°N) Uchida et al. 2002 

bryophyte cover 21 g m -2 yr -1 Marion Island (45º54'S) fellfield Russell 1985 

bryophyte cover 12.8 g m -2 yr -1 max, East Ongul Island, Antarctica Ino 1983 

Physcomitrium spp. 11.30 g m -2 yr -1 Annual net production Munshi 1974 

Polytrichum strictum 2-5 mm yr -1 Antarctic Longton 1974? 

Polytrichum strictum 15-55 mm yr -1 Pinawa, Manitoba Longton 1979?

Table 6. Mean maximum values for photosynthesis (CO 2 

uptake) and biomass (DM) increase at natural CO2 levels, 

saturating light intensity, optimal temperature, and adequate water 

availability. From Larcher (1983). 

Plant group CO2 uptake 

mg dm -2 h -1 mg gDM -1 h -1 

Land Plants 

Phanerogams 

Herbaceous plants 

C4 plants 30-80 (108) 60-140 

C3 plants 

Crop plants 20-45 (60) 30-60 

Plants of sunny habitats 

(heliophytes) 

20-40 (94) 30-60 

Shade plants (sciophytes) 4-20 10-30 

Plants of dry habitats 

(xerophytes) 

20-45 15-33 

Grain and fodder grasses 15-35 (40) 

Wild grasses and sedges 

CAM plants 

8-20 (25) 8-35 

In the light 3-20 0.3-2 

In the dark 

Woody plants 

Tropical and subtropical trees 

10-15 1-1.5 

Fruit trees 18-22 10-25 

Forest canopy trees 12-24 

Understory trees 

Broad-leaved evergreens of the 

5-10 

subtropics and warm-temperate regions 

Sun leaves 10-18 

Shade leaves 

Seasonally deciduous trees 

3-6 

Sun leaves 15-25 (35) 

Shade leaves 

Conifers 

5-10 

Winter-deciduous 10-40 

Evergreen 5-18 4-18 

Mangrove trees 6-12 (20) 

Sclerophylls of periodically 

dry regions 

5-15 3-10 

Bamboos 5-10 

Palms 6-10 (12) 

Desert shrubs (4) 6-20 (30) (2) 5-15 (35) 

Dwarf shrubs of heath and tundra 

Winter- deciduous 10-25 15-30 

Evergreen 

Cryptogams 

5-10(15) 2-10 

Ferns 3-5 

Mosses up to 3 0.6-3.5 

Lichens 

Aquatic Plants 

0.5-2 (6) 0.3-2.5 (4) 

Swamp plants, emersed hydrophytes 20-40 (50) 

Submersed cormophytes 2-6 5-25 

Seaweeds 3-10 1-20 (30) 

Planktonic algae 2-3 

Latitude differences 

It is difficult to determine if responses of populations 

in different parts of the world are the result of genetic 

differences or differences in acclimation history 

(Sveinbjörnsson & Oechel 1983). Polytrichum commune 

from five diverse regions from Alaska (71°N) to Florida 

(29°N) were grown under common garden conditions in 

constant temperature conditions of 5 and 20°C. In this 

common set of conditions, plants from lower latitudes had 

higher photosynthetic rates except for the temperate St. 


Hilaire population. There was a sevenfold difference 

between the extreme values. Populations from the lower 

latitudes had more maximum photosynthetic response to 

the two temperatures than did populations from higher 

latitudes. On the other hand, bryophytes from higher 

latitudes had higher energy contents than those from lower 

latitudes (Russell 1990; Figure 17). 

Figure 17. Comparison of mean energy content of 

bryophytes related to latitude in several tundra sites in Devon 

Island and Point Barrow, Alaska; Hardangervidda, Denmark; Mt. 

Washington, New Hampshire; and Marion Island and South 

Georgia, Antarctica. Reprinted from Russell (1990). 

Antarctic 

Temperatures in the Antarctic have rather large daily 

fluctuations during the growing season. Therefore, it is not 

surprising to find that bryophytes growing there show little 

response to changes in temperature and little acclimation to 

any temperature (Davey & Rothery 1996). Nevertheless, 

the species exhibit summer maxima; no seasonal variation 

existed for optimum temperature of gross or net 

photosynthesis. 

Frigid Antarctic 

The frigid Antarctic, with mean air temperatures 

generally below 0ºC and very dry air, is entirely vegetated 

by cryptogams: Cyanobacteria, algae, lichens, and mosses. 

The most conspicuous vegetation is small turf and cushionforming 

mosses including Bryum and Grimmia species 

(Longton 1979). Standing biomass is similar to the annual 

production of the tundra, reaching 1000 g m -2 , but more 

typically 5-200 g m -2 (Longton 1974, Kappen 1985). 

Annual production seems to be less than 5 g m -2 yr -1 

(Longton 1974, Ino 1983). 

The cold Antarctic, with summer mean air 

temperatures of 0-2ºC, has a production of 200-900 g m -2 in 

the larger moss turfs and carpets (Longton 1970, Davis 

1981), comparable to temperate grassland (Longton 1992)! 

In this area, the biomass is more commonly 300-1000 g m -2 

for green shoots, and reaches 20,000 - 30,000 g m -2 for 

total biomass, including older brown parts (Longton 1992). 

It is interesting that the production here is generally higher 

than in the Arctic tundra (Longton 1988, Russell 1990), 

exceeding 1000 g m -2 yr -1 (Russell 1990), perhaps due to 

greater precipitation and enhanced soil N and P from the 

marine environment (Longton 1992). 

Arctic 

Even in the cold Arctic, water is a major controlling 

factor in photosynthesis. Sanionia uncinata has high 

photosynthetic activity only when water content is high 

during or following rainfall (Uchida et al. 2002). 

Temperature has little effect on net photosynthetic rates in 

this species, being constant in the range of 7-23°C.


Wetlands 

In the Arctic wetlands, mosses account for 91% of the 

above ground biomass (Oechel & Sveinbjörnsson 1978). 

Grasses and sedges usually arise from a bed of mosses, 

including the turf-forming Meesia and Cinclidium and 

carpet-forming Calliergon and Drepanocladus species 

(Longton 1992). The annual production of 100-300 g m -2 

can be 20-45% bryophyte (Longton 1992) and the biomass 

is up to 150 g m -2 (Oechel & Sveinbjörnsson 1978). 

Tundra 

In the tundra, mosses exhibit about 10% of the 

productivity of higher plants, despite occupying 50% of the 

above ground biomass. Whereas Polytrichum strictum can 

have an annual production of 450-500 g m -2 in the cool 

Antarctic grassland, it reaches only 100-150 g m -2 in the 

Arctic spruce woodland (Longton 1979). However, in 

some areas, the production reaches 50-90% of higher plant 

production and values up to 1000 g dry wt m -2 yr -1 can be 

measured (Clarke et al. 1971, Kallio & Kärenlampi 1975, 

Oechel & Sveinbjörnsson 1978, Russell 1990). More 

typical values are 1-50 g dry wt m -2 yr -1 . Ratios of biomass 

to production can be exceedingly high, up to 70:1, 

illustrating the slow growth and the extreme longevity of 

the plants (Longton 1992). In heath communities in the 

tundra of northern Sweden, biomass reaches 156 g m -2 

(Jonasson 1982). However, in below ground biomass, the 

phanerogams far exceed the bryophytes, with underground 

parts contributing more than 50% of the total production of 

all plants (Longton 1984). 

Coxson and Mackey (1990) found that the subalpine 

Pohlia wahlenbergii (Figure 1) exhibited strong diel 

periodicity in midsummer conditions, declining from 8 mg 

CO2 g -1 hr -1 to ~5 mg CO2 g -1 hr -1 . 

Boreal forest 

In the boreal forest, the dominant mosses are feather 

mosses, especially Hylocomium splendens and Pleurozium 

schreberi (Figure 18; Longton 1992). Biomass can reach 

170-290 g m -2 under spruce in Alaska, but only 4-6 g m -2 

under Betula and Populus species. Likewise, production 

was hardly measurable in the Betula and Populus forests, 

but reached 70-150 g m -2 under spruce, often exceeding the 

productivity of the spruce itself (Longton 1992)! Similar 

rates to those under spruce are found for feather mosses in 

other coniferous forests (Tamm 1953, Weetman 1968, 

Pakarinen 1978). Pleurozium schreberi in black spruce 

forests in New Brunswick, Canada, had an annual 

productivity of 44-66 g m -2 (Timmer 1970). Tamm (1953) 

reported 45-60 g m -2 for Hylocomium splendens in a 

Swedish spruce forest and Damman reported 50 g m -2 for it 

in Newfoundland black spruce forests. Van Cleve and 

coworkers (1983), for black spruce forests near Fairbanks, 

Alaska, reported an even higher value of 100 g m -2 . 

Figure 18. Pleurozium schreberi. Photo by Jan-Peter 

Frahm. 

In addition to feather mosses, Sphagnum is a 

prominent member of many boreal communities. In a 

black spruce forest, Swanson and Flanagan (2001) found 

that Sphagnum had higher maximum rates of gross 

photosynthesis than did the feather mosses and exhibited 

distinct seasonal changes in its photosynthetic capacity. 

Several species of Dicranum occur in boreal forests, 

and Kellomäki et al. (1978) found that they differ 

physiologically in their ability to tolerate desiccation and 

photosynthesize. Even within the same species, two 

varieties can differ substantially. For example, the 

photosynthetic rate of D. fuscescens var. congestum 

increases more rapidly at 12.5ºC than at 17.5ºC with 

increasing light than does that of D. fuscescens var. 

flexicaule, in which the rates at the two temperatures are 

essentially identical. In D. fuscescens var. congestum, the 

rate at 12.5ºC is nearly double that at 17.5ºC. However, 

water deficit has a strong effect on the photosynthetic rate. 

The best photosynthesis seems to occur in the morning 

when the plants are able to use morning dew. 

Temperate forest 

Ground cover of bryophytes in temperate forests varies 

widely. In oak forests in Hungary, production is only 4.3 g 

m -2 (Smith 1982). Oceanic European oak forests may 

reach 35.5 g m -2 (Pócs 1982). Forman (1969) reported a 

scant 2-3 g m -2 in deciduous forests in New Hampshire, 

USA, whereas Rieley and coworkers (1979) reported 1600 

- 2900 g m -2 in a Welsh Quercus petraea woods. In these 

oakwoods, the production was 170-210 g m -2 for the 

mosses, whereas the herbs had a production of only 120 g 

m -2 . Many of the oakwoods in England are on rocky 

hillsides where litter accumulation is small, whereas many 

North American temperate forests bury the mosses in litter 

just as the fall growth season for mosses begins (Pitkin 

1975). However, Rieley and coworkers (1979) offer 

another explanation. Sheep eat the grasses selectively and 

leave the mosses behind. On tree trunks and logs, above 

the litter, temperate forest bryophytes can be significant. 

In the temperate rainforest of Washington, USA, 

biomass can be as great as 800 g m -2 of tree surface, 

translating to 500 g m -2 of forest floor. In the Douglas fir 

forests of Oregon, USA, bryophyte biomass can be as high 

as 8.9 kg on a single 65 m tall tree (Pike et al. 1972). On 

Mt. Baker in Washington, bryophyte biomass averages ca 

180 g m -2 (Edwards et al. 1960). However, in pine forests

in France, the moss Pseudoscleropodium purum (Figure 

19) has a relatively low annual production of only 39 g m -2 

(Kilbertus 1968). 

Figure 19. Pseudoscleropodium purum. Photo by Michael 

Lüth. 

Epiphytes 

Neckera pennata (Figure 20) demonstrates that colony 

growth in area is proportional to colony size, thus 

exhibiting exponential growth (Wiklund & Rydin 2004). 

Precipitation was an important parameter in determining 

colony growth. Presence of other species reduced growth. 

Wicklund and Rydin estimated that the colony needs to 

attain a size of 12-79 cm 2 before reproducing sexually, 

taking 19-29 years to attain that size. 

Figure 20. Neckera pennata, an epiphytic moss. Photo by 


Peatlands 

Moore (1989) found a slight tendency for production 

of Sphagnum to decrease as temperatures decrease 

northward. Wider differences, however, occur within a 

single peatland. Hummocks can have annual production of 

100-150 g m -2 , lawns 500 g m -2 , and pools 600-800 g m -2 

(Clymo 1970, Clymo & Hayward 1982), suggesting that 

water availability is the limiting factor for production. Vitt 

(1990) reported that production varies from 70 to 400 g m -2 

per year, with fen mosses at the lower half of the range. 

The highest productivity measured in peatlands seems to be 

that of Sphagnum (868 g m -2 yr -1 ) in a recently burned 

Eriophorum community in Great Britain (Heal et al. 1975). 

Grigal (1985) found a productivity of 320-380 g m -2 yr -1 in 

a forested Minnesota bog and Elling & Knighton (1984) 


found slightly higher results (390 g m -2 yr -1 ) in an open 

Minnesota bog. These figures of production compare with 

a standing crop of 500 g m -2 in west Norway (Laennergren 

& Oevstedal 1983). Somewhat lower values have been 

reported for Moor House, England, Sphagnum, where the 

productivity was 213 g m -2 yr -1 (Forrest & Smith 1975). 

Surprisingly, rich fen production is lower. Vitt (1990) 

found that in Alberta, Canada, at higher elevations it was 

47-93 g m -2 yr -1 , whereas in the lower boreal sites it was 

125-131 g m -2 yr -1 . Vitt attributes the lack of increased 

productivity in rich fens to the similarity of N and P 

concentrations in the poor, rich, and extreme-rich fens. 

Nevertheless, in poor fens, Bartsch and Moore (1985) 

found that productivity of Sphagnum in Quebec was only 

58-73 g m -2 yr -1 in hummocks and 9-19 g m -2 yr -1 in lawns. 

It is somewhat puzzling that bog hummocks have less 

production than carpets, but that poor fen hummocks have 

double the production of lawns (Vitt 1990). 

In peatlands, bryophytes are major contributors to the 

primary productivity. At a peatland in West Virginia, 

bryophytes covered 68% of the ground and contributed 

43% of the aboveground net primary productivity, with 20, 

10, and 27% contributed by herbaceous species, trailing 

shrubs, and upright shrubs, respectively (Wieder et al. 

1989). Bryophytes covered 68% of the ground. 

Precipitation plays a major role in the productivity. Moore 

(1989) found that growth at the lawn sites was higher than 

that of hummocks in an average rainfall year, but in a dry 

year, growth in two of the three lawn sites was less than 

that in the hummocks. 

Species can differ widely in their photosynthetic 

activity. Dry matter accumulated 141-206 g m –2 in 

Sphagnum tenellum, 32-190 g m -2 in S. papillosum, and 

187-219 g m -2 in S. nemoreum (=S. capillifolium) at the 

Takadayachi Moor in Hakkoda Mountains, Japan 

(Fukushima et al. 1995). 

Temperature influences the light compensation point 

of peatland mosses in Alaska (Harley et al. ). The light 

compensation point increased from 37 µM m -2 s -1 at 10°C 

to 127 µM m -2 s -1 at 20°C, despite little increase in the 

maximum CO2 uptake rate. Laboratory experiments 

indicated that responses could be quite different from that 

in the field, with considerably lower light compensation 

points and higher light saturation rates of assimilation. 

Peatlands can serve as important carbon sinks. In 

restored peatlands, Waddington and Warner (2000) found 

that the peatlands resulted in considerable decrease in the 

atmospheric CO2 (~70% decrease due to gross productivity, 

30% to decreased respiration). Unfortunately, restoration 

did not restore the peatlands to a net carbon sink, but it 

greatly improved the sequestration of carbon. 

Desert 

In the Chihuahuan, Sonoran, and Mohave Deserts in 

North America, the highest biomass of mosses (2.24 g m -2 ) 

occurred on the north slope of the Mojave (Nash et al. 

1977). 

In a sandy semidesert, Juhász et al. (2002) found that 

Syntrichia ruralis exhibited their highest daily carbon 

fixation rates in December and January, whereas in the 

summer it went dormant. A net carbon gain did not occur 

until October. This species is able to maintain its 

physiological integrity and net photosynthetic gain by


changing the surface reflectance and exhibiting thermal 

dissipation of excess light energy (Hamerlynck et al. 2000). 

Grimmia laevigata from the inland chaparral of 

California, USA, is unable to survive in the most xeric sites 

because it is unable to maintain a positive carbon balance 

during repeated wet-dry cycles (Alpert & Oechel 1985). 

Savannah 

In such dry habitats as the savannah, the life cycle can 

be shortened to accommodate the lack of water. Mosses 

such as Archidium ohioense, Bryum coronatum, Fissidens 

minutifolius, and Trachycarpidium tisserantii develop 

protonemata and gametophytes in March – April; by 

September and October the spores are being dispersed 

(Makinde & Odu 1994). All of these events occur within 

the rainy season, permitting maximum photosynthesis. 

Temperate Rainforest 

Although the rainforest has its season of daily rain, it 

also has periods of continued dryness. Under these 

circumstances, respiration may exceed photosynthesis, 

causing negative photosynthetic gain (DeLucia et al. 2003). 

Forest floor bryophytes in a New Zealand rainforest have 

an annual net carbon uptake of 103 g m -2 , compared to 

annual carbon efflux from the forest floor (bryophyte + soil 

respiration) of -1010 g m -2 . Bryophytes were unable to 

recover more than 10% of carbon lost from the forest floor. 

Tropical rainforest 

The biomass of bryophytes in the tropics rises sharply 

with elevation. Frahm (1990a) found standing biomass of 

bryophytes to be less than 10-12 g m -2 of tree trunk at low 

elevations (up to 1000 m), up to 140 g m -2 in Peru, and 400 

- 800 g m -2 in Borneo. Exceptionally high biomass of 

bryophytes, up to 1030 g m -2 , can occur in high altitude 

epiphytes in Tanzania (Pócs 1982). The astonishingly high 

figure of 1400 g m -2 productivity occurs among the 

epiphytic bryophytes of a Tanzanian cloud forest (Pócs 

1980). 

High temperatures and low light place severe 

limitations on tropical net productivity (Frahm 1990b). 

Temperatures above 25°C drastically decrease the net 

assimilation. Coupled with the lowlight, temperature 

causes productivity of bryophytes in tropical lowlands to be 

the lowest of any tropical altitude, with high rates of 

respiration often resulting in no net carbon gain. 

Aquatic 

Rivers and Streams 

Naiman (1983) considered mosses in 4th order or 

higher streams to be the most productive autotrophic 

members of the stream community in boreal forest 

watersheds, producing 3.9 x 10 10 g yr -1 . This compares to 

periphyton productivity of only 2.1 x 10 10 g yr -1 in the same 

watersheds. These higher order streams occupy 76.8% of 

the lotic surface area and are responsible for 86.3% of the 

gross productivity, demonstrating the importance of 

bryophytes in the stream ecosystem. 

But stream habitats can be rather unfavorable, 

especially for mosses. In one study in Oregon, Fontinalis 

only had positive photosynthesis in the winter (Naiman & 

Sedell 1980). It was negative the rest of the year. 

Despite their slow growth and low nutrient 

requirements, higher nutrients can favor enhanced growth 

in some bryophyte taxa. In Alaskan streams, 

Hygrohypnum alpestre and H. ochraceum increased in 

cover following phosphorus enrichment, whereas 

Schistidium agassizii showed little response (Arscott et al. 

2000). Although the Hygrohypnum species were intolerant 

of desiccation, they were more tolerant of high 

temperatures than S. agassizii, having the higher 

productivity (1676-6342 µg O2 g -1 dry mass h -1 ) compared 

to that of S. agassizii (428-1163 µg O2 g -1 dry mass h -1 ). 

Lakes and Ponds 

Bryophytes in lakes enjoy the presence of constant 

water, permitting photosynthesis at any time other factors 

are favorable. Instead of being at the mercy of water 

availability like most bryophytes, these bryophytes face the 

limits of low light intensity, rapidly attenuated red light, 

and poorly dissolved CO2. In most lakes, temperature is 

not a problem, with bottom temperatures of deep lakes 

generally not going below 4ºC, and summer temperatures 

often not exceeding 10ºC. In more shallow lakes and 

ponds, summer temperatures may become a problem if they 

reach 20ºC and sustain that temperature for extended 

periods. Under those conditions, hydrated bryophytes not 

only lose more energy to respiration than they gain by 

photosynthesis, but they must compete with aquatic 

tracheophytes and algae that benefit from the higher 

temperatures. Sediment CO2 can often contribute to the 

productivity of bottom-dwelling bryophytes in lake 

systems. 

The floating liverwort Riccia fluitans (Figure 21) 

increased its relative growth rate from 0.011 d -1 at low light 

and CO2 to 0.138 d -1 at high light and CO2 (Andersen & 

Pedersen 2002). There was strong acclimation to light and 

CO2 conditions. Nevertheless, high light intensities 

resulted in decreased maximum net photosynthesis while 

increasing CO2 continued to increase the maximum net 

photosynthesis. The CO2 compensation point for 

photosynthesis was strongly depressed by high light and 

low CO2 and increased in low light and high CO2. High 

levels of CO2 within the floating mat permits 

photosynthesis at greater depths where the light intensity 

attenuates. 

Wagner et al. (2000) found that in Waldo Lake, 

Oregon, liverworts, comprising 98% of the bryophyte 

biomass, exhibited growth similar to that of upland plants 

(1.5-3 cm annually). 

Figure 21. Riccia fluitans, a floating thallose liverwort. 

Photo by Michael Lüth.

Summary 

Productivity can be considered in many ways, 

including ability to invade, linear growth, biomass increase, 

CO2 uptake, O2 production, C 14 incorporation, chlorophyll 

concentration, and surface expansion. Biomass gain may 

often be uncoupled from linear growth, with the former 

typically occurring first. 

Likewise, annual growth of the plant can be measured 

in many different ways, including length of branch 

internodes; distance between splash cups on a stem; height 

above a cranked wire, tag, nylon net, plastic bubbles, or 

dye, growth out of a nylon bag; photographic record of 

expansion on a grid. Pleurocarpous mosses typically 

exhibit exponential growth, whereas unbranched 

acrocarpous mosses have linear growth, thus requiring 

different measures of growth. 

Etiolation (excessive elongation and loss of 

chlorophyll due to insufficient light) may occur in low-light 

environments, giving a false measurement of length as an 

indication of productivity. 

Productivity is generally highest when there is a good 

supply of water and ceases when the bryophyte is 

desiccated, causing seasonal differences. Once the 

moisture requirement is met, temperature and light are 

important in determining maximum productivity, with most 

bryophytes diminishing in productivity above 20-25ºC and 

dying at prolonged exposure above 30ºC if hydrated. The 

lower limit varies geographically and with species, with 

some species having their compensation point as low as - 

10ºC. In water, bryophytes are limited by low light and 

low concentrations of CO2, but those on the bottom can 

take advantage of CO2 from the sediments. 

Belowground productivity may be extensive in some 

bryophytes, such as those in the Polytrichaceae. Capsules, 

and even spores, can contribute to overall productivity, but 

at the same time, they typically reduce productivity of the 

leafy gametophyte. 

Life span may be months to centuries, but unlike 

tracheophytes, generally only the upper portion of the stem 

supports active productivity. Mortality of the whole stem 

can be high, reaching 32% in Antarctic young populations 

of Polytrichum strictum. On the other hand, longevity may 

reach 17 years in the Arctic, compensating for the slow 

growth, and apparently is even higher in some cold lakes. 

The Leaf Area Index (LAI) indicates that bryophytes 

are well adapted to take advantage of the many angles of 

the sun, reaching such levels as 44 and 129 for sun-adapted 

species, whereas a value of 1 indicates full usage; anything 

higher than 1 permits maximum usage at more angles of 

the sun. Mosses in the boreal biome have an LAI of about 

20. Light use efficiency can be very high, but productivity 

still remains low, perhaps due to CO2 limitation. Mosses 

have a maximum CO2 uptake of about 3 mg dm -2 hr -1 , 

whereas C3 tracheophytes reach 45 and C4 plants reach 80. 

Some bryophytes, especially Cryptothallus mirabilis, 

rely on fungal partners for their carbon input. Other 

thallose liverworts can lose energy to fungi. 

The highest productivity, when it occurs, seems to be 

from bryophytes in the driest habitats. On the other hand, 

yearly productivity seems to be highest in Sphagnum, 

reaching 12 tons per hectare. 


Striking differences occur among latitudes and 

habitats. For example, Antarctic bryophytes have drastic 

daily temperature fluctuations and show little response 

temperature differences. Cool tundra populations of 

Polytrichum strictum may have only 1/4 – 1/3 the 

production they exhibit in the cool Antarctic grassland. 

The ultimate limit to productivity, hence to distribution, is 

achieving a positive carbon balance. Heat causes 

respiratory loss and frequent wet-dry cycles require 

excessive repair, both reducing the net carbon gain in some 

habitats to 0 and ultimate death. 

Acknowledgments 

Klaus Weddeling, Brian O'Shea, and Marshall Crosby 

helped me find the new name for Hylocomium parietale. It 

appears to have been H. parietinum, now Pleurozium 

schreberi. Several bryonetters helped me locate the current 

name of Homaliodendron scalpellifolium, which is now H. 

flabellatum. 

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Chapter 12: Productivity 21

CHAPTER 12 PRODUCTIVITY - Bryophyte Ecology - Michigan ...

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