Agriculture & Forestry, Vol. 65 Issue 2: 39-51, 2019, Podgorica
39
DOI: 10.17707/AgricultForest.65.2.03
Farhad ASADI, Afrooz ALIMOHAMADI
1
ASSESSING THE PERFORMANCE OF POPULUS CASPICA AND
POPULUS ALBA CUTTINGS UNDER DIFFERENT
IRRIGATION INTERVALS
SUMMARY
Understanding the function of poplar species under different irrigation
regimes is critical for water resources and ecosystem sustainable management.
This study was conducted in order to understand the performance (survival and
height growth) of two poplar species (Populus alba L. and Populus caspica
Bornm.) cuttings in two lengths (15 cm and 25 cm) under three irrigation
treatments (7-day, 14-day and 21-day intervals). One trial was established using
split-split-plot design with three replications. Every two weeks height and
number of remaining cuttings were measured. Results showed the survival
average at the end of periods for 7-day, 14-day and 21-day irrigation treatments
were 83.33 %, 22.08 % and 0 %, respectively, for P. alba and P. caspica were
25.89 % and 44.39 %, respectively and for cuttings in 15 and 25 cm were 29.61
% and 40.66 % respectively. The results of two-way analysis of variance of the
survival among cuttings indicated that the differences survival among cuttings
were all marked under the four treatments and analysis of variance of the height
growth indicated that except under the size treatment, the differences height
growth among cuttings were all marked under the other three treatments.
Keywords: Populus caspica, Populus alba, irrigation interval, height
growth, survival.
INTRODUCTION
Poplar is an excellent candidate for short rotation coppice cultures, which
rely on species that is characterized by fast growth and dynamic production of
biomass (Payamnour et al, 2013). This species as an alternative source for wood
production (Alimohamadi et al. 2012) have been planted in Iran for many years.
Annual production of poplar plantations, according to available statistics, is more
than triple the production of Caspian forests (the only commercial forests in Iran)
while their area is less than 10 percent of Caspian forests area (Bozorgmehr et al.
2014). Poplar growth is highly dependent on the moisture content of the soil
(Bagheri et al. 2012) and soil water can exert an important control on poplar
growth (Dong et al. 2011, Hogg et al. 2013). Accordingly having a permanent
resource of water is a primary need of poplar plantation. Since Iran is in the arid
1
Farhad Asadi, Mazandaran Agricultural and Natural Resources Research Center, Sari, IRAN,
Afrooz Alimohamadi, (corresponding author: afrooz.alimohamadi@pnu.ac.ir), Department of
Agriculture and Natural Resources, Payame Noor University (PNU), Teheran, IRAN.
Notes: The authors declare that they have no conflicts of interest. Authorship Form signed online.
40
Asadi and Alimohamadi
zone which receives less than a third of world average precipitation (Badripour,
2006), shortage of water resources is a major obstacle to successful poplar
cultivation. In order to increase the productivity of poplar plantations in arid and
semiarid lands, high efficiency irrigation strategies must be used. The efficiency
of water use can be examined through assessment of poplar responses which
differ from one species to another and from one age to other age. Various indices
have been used to find the poplar responses to irrigation which consist of: a)
growth traits such as diameter at breast height (Bagheri et al. 2012, Shock et al.
2005), basal area at breast height (O’Neill and Allen 2015, Voltas et al. 2006),
total height (Bagheri et al. 2012, Shock et al. 2005), stem height (Bagheri et al.
2012), crown diameter (Bagheri et al. 2012), relative growth rate (Karačić and
Weih 2006), volume (O’Neill and Allen 2015, Bagheri et al. 2012, BaoFang et
al. 2007, Shock et al. 2005), biomass (Monclus et al. 2009, Karačić and Weih
2006), survival (O’Neill and Allen 2015, Saeidi and Azadfar 2009, Van den
Driessche et al. 2003), radial growth (Giovannelli et al. 2002), root number
(BaoFang et al. 2007); b) physiological characteristics such as foliar nutrition
(Shock et al. 2005), mesophyll-to-stomatal conductance ratio (Rancourt et al.
2015), photosynthetic performance (Zhu et al. 2014; Saeidi and Azadfar, 2009,
Fengjun et al. 2006 ), transpiration (Samuelson et al. 2007), leaf-specific
hydraulic conductance (Samuelson et al. 2007), canopy stomatal conductance
(Samuelson et al. 2007), stem water potential (AiHong et al. 2009); c)
morphological traits such as leaf area (Monclus et al. 2009, BaoFang et al. 2007,
Samuelson et al. 2007); d) phenology events such as bud-burst (Bagheri et al.
2012, Sera and Pons 2013), leaf expansion (Bagheri et al. 2012), leaf abscission
(Bagheri et al. 2012), flowering (Bagheri et al. 2012; Sera and Pons 2013) and e)
anatomical characters such as wood anatomy (Cocozza et al. 2011).
In order to develop efficient water use strategies in poplar plantations,
different irrigation regimes can be conducted. Irrigation regime which is
determined by the rate of irrigation, irrigation frequency (intervals), and time of
water applications to crops. Some research has been undertaken on high
efficiency irrigation regime in poplar plantations. Zhu et al (2014) investigated
the effects of changed irrigation (water-saving irrigation and flood irrigation) on
two poplar species (P. euphratica and P. russkii) growing in arid ecosystems.
Results showed that reduced water availability during water-saving irrigation had
a moderate but not significant impact on the photosynthesis of the two poplar
species. Sera and Pons (2013) analyzed the dynamics of poplars between 2002
and 2008 which comprised periods of water surplus and water scarcity. No
difference was observed between periods of water scarcity and water surplus.
Bagheri et al (2012) showed significant difference between the 4, 8 and the 12
day irrigation intervals in respect to growth parameters of P. euramericana, P.
trichocarpa, P. alba, P. nigra and P. deltoids. Cocozza et al (2011) investigated
the correlation between the main ring traits of young poplar clones (P ×
canadensis and P. deltoides) and irrigation regimes (irrigated with 70 mm of
water every week and no-irrigated). Results showed P. deltoides has the potential
Assessing the performance of Populus caspica and Populus alba cuttings
41
to recover promptly after drought stress. AiHong et al (2010) in temperate desert
zone analyzed the change of water potential of Populus euphratica Oliv. and P.
Russkii Jabl under different irrigation volumes. Saeidi and Azadfar (2009)
investigated the effect of drought and hydromorphy stresses on net
photosynthesis rate and survival of P. nigra , P. deltoides and P. euramericana.
Result showed P. deltoides and P. nigra had more resistance to drought stress
than hydromorphic. Zomer et al (2007) irrigated their poplar plantations during
April to June, when the atmospheric temperature is high with a low level of
relative humidity. Fengjun et al (2006) applied four water treatments: wellwatered condition, slight water stress, moderate water stress, and severe water
stress. The results revealed that the clones with higher long-term water use
efficiency always had strong photosynthetic capacity and optimum root/shoot
ratio. Shock et al (2005) applied five irrigation treatments for hybrid poplar
consisted of three water application rates using micro sprinklers and two water
application rates using drip tape during five years. Result showed drip irrigation
with two tapes per tree row resulted in higher tree growth than micro sprinkler
irrigation.
In Iran, most of the researches about efficient irrigation management have
been done on agricultural crops. Furthermore, there is no research available to
determine growth response of P. alba and P. caspica as a local and critically
endangered species in Caspian forest of Iran (Falah et al 2011) under different
irrigation treatments. Given the importance of Poplars and for optimum use of
water resources in arid season, in this study we explored the growth response and
survival of P. caspica and P. alba cuttings in two lengths to different irrigation
intervals.
MATERIAL AND METHODS
Site
Experiments were carried out in the Chamestan forest and rangeland
research station located in Noor city (36° 25’ N & 51° 55’ E, 70 m a.s.l),
Mazandaran province, Iran. Mean annual temperature and precipitation are 15.8
C° and 840 mm, respectively. Absolute minimum and maximum temperature are
-8.5 C° and 36 C°, respectively. Average relative humidity is 78%.
Experiment design
Cuttings of P. caspica and P. alba in two lengths (15 and 25 cm) were
established in a field trial, as a split-split-plot design with three replications. The
species as factor A was assigned to whole plots, then the cutting length as factor
B was assigned to split-plots within the applications of Factor A, and then split
the experimental units used for factor B into sub-sub-plots to receive different
irrigation intervals as factor C. For this purpose a total of 108 (three treatments of
irrigation intervals, two treatments of cutting lengths, two kinds of species, three
pots and three replications) plastic bags were put into a water container with 15
cm depth and 46 cm diameter (Figure 1). The culture medium was a soil with 33
percent clay, 47 percent loam and 21 percent sand. Soil pH and electrical
Asadi and Alimohamadi
42
conductivity were 6.58 and 0.57 ds/m, respectively. Percentage of lime, organic
carbon and total nitrogen were 1.19, 2.78 and 0.29, respectively and finally the
amounts of phosphorus, potassium, calcium and magnesium were 23.78, 420,
175.5 and 37.5 ppm, respectively (Rouhi Moghadam, 2008). The cuttings were
planted on February with one cutting in each pot. Weeding operation was done
during the growing season. Three different irrigation intervals were applied: 7day intervals, 14-day intervals and 21-day intervals. The amount of irrigation
water at each time was 2000 mL for per pot.
Figure 1: Cuttings in plastic bags under different treatments
Measured objects and statistical analyses
In order to calculating the seedling height growth as an appropriate
indicator for evaluating the effects of stress (Sadati et al. 2011) and survival
under different treatments, every two weeks height and number of remaining
cuttings were measured. Ten measurements were performed on April 27th, May
11th, May 25th, June 8th, June 22th, July 6th, July 20th, August 3rd, August 17th and
August 31th.
Data were evaluated by Kolmogorov-Smirnov test for assessing the
normality, two-way analysis of variance for analyzing the effects of applied
treatments on height growth and survival, Duncan's multiple range test for
measuring the differences between irrigation and period treatments. Statistical
analyses were conducted using SPSS 21.0.
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
RESULTS AND DISCUSSION
Results showed (Figures 2 and Figure 3) the percentage survival of
cuttings under five treatments (in total twelve treatments).
Assessing the performance of Populus caspica and Populus alba cuttings
43
a: P. alba cuttings in 15 cm under 7-day irrigation, b: P. alba cuttings in 15 cm under 14day irrigation, c: P. alba cuttings in 15 cm under 21-day irrigation, d: P. alba cuttings in
25 cm under 7-day irrigation, e: P. alba cuttings in 25 cm under 14-day irrigation, f: P.
alba cuttings in 25 cm under 21-day irrigation, g: P. caspica cuttings in 15 cm under 7day irrigation, h: P. caspica cuttings in 15 cm under 14-day irrigation, i: P. caspica
cuttings in 15 cm under 21-day irrigation, j: P. caspica cuttings in 25 cm under 7-day
irrigation, k: P. caspica cuttings in 25 cm under 14-day irrigation, l: P. caspica cuttings
in 25 cm under 21-day irrigation
Figure 2. The percentage survival under different treatments during measured
periods
44
Asadi and Alimohamadi
Figure 3. Survival of study species under three irrigation intervals and two sizes
The percentage survival was zero of which three treatments were related to
P. alba include the cuttings in 15 cm under 14 and 21-day irrigation intervals and
the cuttings in 25 cm under 21-day irrigation intervals and two treatments were
related to P. caspica include the cuttings in 15 cm under 21-day irrigation
intervals and the cuttings in 25 cm under 21-day irrigation intervals.At the end of
periods there was no zero percent survival in any 7-day irrigation treatments but
all cuttings under 21-day intervals (all treatments related to two species and two
sizes) had died that four deaths had occurred at the ninth period and the P. alba
cuttings in 15 cm under 21-day irrigation intervals had died at the eighth period.
The only treatment with 100 percent survival at the end of periods was related to
P. caspica cuttings in 25 cm under 7-day irrigation intervals.
The survival average at the end of periods for 7-day, 14-day and 21-day
irrigation treatments were 83.33 %, 22.08 % and 0 %, respectively, for P. alba
and P. caspica were 25.89 % and 44.39 %, respectively and for cuttings in 15
and 25 cm were 29.61 % and 40.66 % respectively.
The average height growth of P. alba and P. caspica were 7.44 cm and
9.62 cm. Furthermore, for 7-day, 14-day and 21-day irrigation intervals were
9.25 cm, 8.68 cm and 7.67 cm, respectively and the average height growth of
cuttings in 15 cm and 25 cm were 8.50 cm and 8.56 cm (Figures 4 and Figure 5).
The maximum height growth of four treatments occurred during the fourth
period, for four others occurred during fifth period, two treatments during sixth
Assessing the performance of Populus caspica and Populus alba cuttings
45
period had maximum height growth and two treatments during first period had
maximum height growth (Figure 4).
a: P. alba cuttings in 15 cm under 7-day irrigation, b: P. alba cuttings in 15 cm under 14day irrigation, c: P. alba cuttings in 15 cm under 21-day irrigation, d: P. alba cuttings in
25 cm under 7-day irrigation, e: P. alba cuttings in 25 cm under 14-day irrigation, f: P.
alba cuttings in 25 cm under 21-day irrigation, g: P. caspica cuttings in 15 cm under 7day irrigation, h: P. caspica cuttings in 15 cm under 14-day irrigation, i: P. caspica
cuttings in 15 cm under 21-day irrigation, j: P. caspica cuttings in 25 cm under 7-day
irrigation, k: P. caspica cuttings in 25 cm under 14-day irrigation, l: P. caspica cuttings
in 25 cm under 21-day irrigation
Figure 4. The height growth under different treatments during measured periods
Asadi and Alimohamadi
46
Figure 5: Height growth of study species under three irrigation intervals and two
sizes
The results of two-way analysis of variance of the survival among cuttings
(Table 1) indicated that the differences among cuttings were all marked under the
four treatments (length, species, irrigation intervals and periods). Based on
Duncan's multiple range test, irrigation intervals were classified in two separate
groups: 21-day and 14-day irrigation treatments as first group and 7- day
irrigation treatment as second group. Furthermore, periods based on multiple
comparisons were divided into 3 groups (Figure 6).
Table 1: Two-way analysis of variance for survival of study species under
irrigation and size treatments
Treatment
species
length
irrigation
period
species × length
species × irrigation
species × period
length × irrigation
length × period
irrigation × period
df
1
1
2
9
1
2
9
2
9
18
F
40.385
7.666
26.754
75.899
.160
9.162
1.108
.939
.521
18.170
p Value
.000**
.006**
.000**
.000**
.690ns
.000**
.357ns
.392ns
.859ns
.000**
Significance values are indicated as: * P<0.05, ** P<0.01 and ns non-significant
Assessing the performance of Populus caspica and Populus alba cuttings
47
The results of two-way analysis of variance of the height growth among
cuttings (Table 2) indicated that except under the size treatment, the differences
height growth among cuttings were all marked under the other three treatments
(species, irrigation intervals and periods). Based on Duncan's multiple range test,
irrigation intervals were classified in two separate groups: 21- day irrigation
treatment as first group and 14- day and 7- day irrigation treatments as second
group. Furthermore, periods based on multiple comparisons were divided into 5
groups (Figure 7).
Figure 6: Grouping of periods based on mean survival
Table 2: Two-way analysis of variance for height growth of study species under
irrigation and size treatments
Treatment
df
F
p Value
species
1
31.505
.000**
length
1
2.077
.151ns
irrigation
2
6.997
.001**
period
8
64.840
.000**
species × length
1
2.992
.085ns
species × irrigation
2
.398
.672ns
species × period
8
5.883
.000**
length × irrigation
2
.497
.609ns
length × period
8
2.990
.003**
irrigation × period
16
6.516
.000**
Significance values are indicated as: * P<0.05, ** P<0.01 and ns non-significant
Owing to limited water resources, irrigation interval is more important
than irrigation volume in conventional and industrial poplar plantation systems
(Bagheri et al. 2012). According to this our goal was to examine the more
efficient irrigation regime for P. caspica and P. alba plantations. The results of
applying three irrigation intervals during four months indicated that all cuttings
48
Asadi and Alimohamadi
under 21-day irrigation intervals after about three months died. Furthermore the
only 22 percent of the cuttings under 14-day irrigation intervals survived at the
end of period, but 83 percent of cuttings under 7-day irrigation intervals survived,
therefore it might be concluded that these irrigation regimes (14-day and 21-day)
are not appropriate for poplar wood production. This conclusion is comparable
with the work of Bagheri et al (2012) that showed all the clones of
P.euramericana, P.trichocarpa, P. alba, P. nigra and P. deltoides have intensive
growth reduction at the 12-day interval irrigation in comparison 4-day and 8-day
regime, but there was no difference between 4-day and 8-day irrigation intervals.
Moreover Hara (2004) suggested weekly irrigation during the dry months for
high intensity production of poplar. Chaghaii (2016) believed in areas where
there is no groundwater the irrigation intervals may be reduced to 10-day and soil
should be completely full of water, but on windy sites with sandy soil the
irrigation intervals may be reduced to 7-5 day. Some researchers suggest that the
irrigation intervals should not be considered the same and according to local
conditions should be given more flexibility on warm days (Bagheri et al. 2012,
Zomer et al. 2007).
Figure 7: Grouping of periods based on mean height growth
Unlike this fact that P. alba is known as high drought tolerance species
(Edward et al. 1994) the present result showed the survival average at the end of
periods and average height growth of P. alba cuttings are significantly less than
P. caspica cuttings and therefore P. alba than P. caspica are more sensitive to
longer intervals of irrigation, but Bagheri et al (2012) showed P. alba clones than
other study poplar clones are less affected by drought conditions and have the
same performance at three irrigation intervals (4, 8 and 12-day).
The results showed the survival of cuttings in 25 cm length are
significantly more than cuttings in 25 cm length, although there was no
significant difference between height growths of cuttings in two lengths. These
results are confirmed by some studies that showed the longer the cuttings, the
higher are the survival (Singh Thakur et al. 1995, Rossi, 1991).
Assessing the performance of Populus caspica and Populus alba cuttings
49
Since potential growth of poplar is highly dependent on the amount of
applied irrigation (Shock et al. 2002) and soil moisture (Kharytonov et al. 2017)
therefore the improvement of water use efficiency especially in arid areas with
regard to limited water supply is a key objective to improve the sustainability of
cultivated poplar (Rancourt et al. 2015).
Water-saving irrigation (Zhu et al. 2014) and increasing the intervals of
irrigation (Bagheri et al. 2012) could be as economical practices for managing
water use in such areas, As our goal was to examine the effect of different
irrigation intervals on survival and height growth of two poplar species.
Furthermore, management of irrigation intervals owing to water influence on pest
management is very important. As the work of Tahriri Adabi et al (2013) showed
high provided amount of water in 4 days interval in comparison to 8 and 12 days,
make poplar species and clones more susceptible against pest. It is worth
mentioning that today using treated wastewater for poplar irrigation is suggested
as an alternative strategy for water supply problems in semi-arid to arid areas
(Houda et al. 2016).
CONCLUSIONS
Our study revealed that 1) survival of study poplar was found to be
dependent on irrigation intervals; 2) the best performance (survival and height
growth) of study poplar was under 7-day irrigation interval; 3) P. caspica has
relatively higher water-stress resistance than P. alba; 4) longer cuttings than
shorter cuttings had higher survival.
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