Abstract: In February 2001, one-year bareroot cypress (Cupressus sempervirens var. horizontalis) seedlings were replanted in plastic pot in a lowland nursery located in southern coast of the Caspian Sea (north of Iran). Soils of pots consisted of 1:1 sand:clay (A), pure sand (B), 2:1 sand:clay (C), 1:1:1 sand:clay:organic matter (D), 1:1:2 sand:clay:organic matter (E). In each soil treatment a high value of survival and growth was appeared in July and progressively decreased till November. In each month the seedlings grown on rich soils (D and E) had mostly greater growth and survival than on infertile soils. At the end of the first growing season seedling vitality differed significantly among the soils but did not differed notably in soil A with those in other soils. Survival rate was highest in the rich soils (D and E). Stem length as well as collar diameter performed the least growth on the poor soils (B and C). Like other characteristics measured, survival responded better to soils containing organic matter (D and E). It is concluded that generally characteristics of cypress seedling are suited by adding organic matter to sandy soils. This is while that poor nutrient available soil such as soil A produces a proper growth for cypress seedling, too.
INTRODUCTION
The main objective of each plantation project is to suit the growth and establishment of seedlings. In this regard, good elaboration of inhibiting factors of planting sites and careful understanding of ecological requirements of species are unavoidable (Krasowski and Elder, 2000). In plantations, growth and survival increase and the costs decrease when high-quality seedling is yielded in nursery (Wightman et al., 2001). Generally, soil is a determining factor in life cycle of conifer seedlings (Korani, 1991; Sheikh-Khan et al., 1980, cited by Shahini, 1996). For example, peat with 70% organic matter, compared to low-fertile soils, produces greater growth for some pines (Schwan, 1994). In medium of sand:clay:sphagnum (1:1:3), Cupressus sempervirens shows a better growth after second growing season (Hassan et al., 1994). However, some cypress species including Japanese cypress (Chamaecyparis obtusa) is grown on low fertility sites, contrary to Japanese cedar (Cryptomeria japonica) which grown on the richer sites (Sasaki et al., 1994; Yamashita et al., 2004).
Generally, few investigations have been reported about the effect of soil on conifers in the north of Iran. C. sempervirens is one of the forth-fold native coniferous species in Iran and has a unique role in restoration of the deforested areas, particularly in the Mediterranean climatic zones. Regarding to the importance of seedling production, research on soil type in order to improve the qualitative and quantitative characteristics of this species in nursery is necessary. We hypothesized that the best survival and growth rates of cypress seedling could be obtained in more fertile soils. In addition, poor nutrient available soil could be also an acceptable soil for raising cypress seedling.
MATERIALS AND METHODS
The study site was a lowland nursery located in southern coast of the Caspian
Sea (north of Iran), Noor town (36°34’ N and 51°59’ E, -20
m a.s.l.). Mean annual precipitation was 1100 mm, mean annual temperature and
mean max. temperature of the warmest month were 16.4 and 30°C, respectively.
Dry days (xerothermique index) of the year were determined 55 days.
| Table 1: | Discoloration degree of C. sempervirens seedlings, based on UN/ECE and UE (Anonymous, 1998) |
Based on Emberger (1932) classification, climate of the study site, with Q2 = 143.6 (index of precipitation and temperature) and m = 3.7°C (Mean minimum temperature of the coldest month) is moist with mild winters.
In February 2001, some 1-year bareroot Cupressus seedlings in 30 (±2.5) cm length and 4 (±0.4) mm collar diameter produced in a preliminary investigation were replanted in plastic pots of 20x20x40 cm. Soil in pots consisted of 1:1 sand:clay (A), pure sand (B), 2:1 sand:clay (C), 1:1:1 sand:clay:organic matter (D), 1:1:2 sand:clay:organic matter (E). The research was conducted for one year. Only one weeding (in June) but no irrigation was made during the study period.
Collar diameter and stem length were measured at intervals of two months (late March to late November). Vitality quality (foliage coloration) of needles, according to UN/ECE and UE (Anonymous, 1998) classification (Table 1), was recorded in late August. Seedlings were counted every two months and survival rate determined in late November.
The experiment of design was as randomized complete design, with three replicates of 28 units (seedlings) for each medium. For comparison of means a Tukey-HSD test was analyzed among five soil treatments. Statistical analyses were performed using the SAS software. The p-value was set at 0.05 of probability level.
RESULTS
Survival: Measurements showed that in beginning of the first growing
season (March) all seedlings replanted in February were alive. A high survivorship
for all treatments appeared in July but gradually declined till November. In
each month the seedlings growing on rich soils (D and E) had higher survival
rate when compared with those on infertile soils (Fig. 1).
By comparing means, it was also revealed that at the end of the first growing
season, pure sand (B) and sandy-clay (C) soils remained the poorest survivorship
for seedlings (Table 2). Survival in soil (A) was not significantly
different with those in soils B, C and D. Indeed, the highest survival rates
(90.5 and 85.7%) were occurred in soils E and D, respectively.
| Fig. 1: | Survival (%) of C. sempervirens seedlings at different soils, occurred in different months of the 1st growing season |
| Fig. 2: | Stem growth (cm) of C. sempervirens seedlings at different soil types, occurred in different months of the 1st growing season |
Growth and vitality: At the end of the first growing season, stem growth
on each soil reached to its maximum in late July and appeared with a decreasing
trend till November (Fig. 2). Stem length was the least in
soils B and C (Table 2). No substantial difference of stem
length could be found in soils D and E, such as in soils D and A. In general,
this term was greater on soil E than on soil A. Like stem growth, collar diameter
growth rose in late July and dropped by the end of the period (Fig.
3). Collar diameter was greatest in nutrient available supplies (D and E).
Compared with soil B, soil A produced a bigger collar diameter.
| Table 2: | Average values of C. sempervirens seedlings in different soil occurred in months of the 1st growing season |
| -Within columns, values followed by different letter(s) are significantly different at p≤0.05 | |
| Fig. 3: | Collar diameter growth (mm) of C. sempervirens seedlings at different soil, occurred in different months of the 1st growing season |
No significant difference of this term could be detected between soil B and soil C (Table 2). Vitality quality (foliage coloration) seemed to be of better status in rich soils (D and E) than in poor soils (B and C). Soil A exhibited an intermediate vitality grade from this viewpoint (Table 2).
DISCUSSION
By the current study it appears that at the end of the study period, stem length as well as collar diameter is smallest on high sand soils (B and C). This is in agreement with findings of Tabari et al. (2005), who present that in 1-year-old (1+0) C. sempervirens seedling shoot growth advances when sand added to sandy-clay substrate. In the current research, the same as findings of Parde (1952, cited by Rezaei, 1992) and Hassan et al. (1994), it is revealed that in Cupressus seedling low growth is observed on infertile and sandy soils and high growth on rich soils. Accordingly, Sheikh-Khan (1980, cited by Shahini, 1996) confirms the positive role of NPK on increase of growth and Korani (1991, on Pinus taeda) reports the increased growth on high-nutritional soils. It should be also cited that other genus of cypress (Chamaecyparis obtuse) can be found on low fertility sites where the N availability is low (Yamashita et al., 2004). Generally, it has been accepted that among the nutrient elements, nitrogen (N) is one of the most important nutrients in regulating the forest productivity on many sites (Reich et al., 1997) and its interaction with soil water may be an important factor of higher productivity (Enoki et al., 1996).
In the present research survival, as well as foliage coloration (vitality quality), is not substantially different in soil A with those in soils B and C. However, on poor soils (B and C) seedlings represent lower survivorship and foliage coloration than on fertile soils (D and E). On soil A, both characteristics play an intermediate role.
Generally, as appeared in this investigation, all parameters poorly responded to poor soils (B and C). Indeed, these characteristics, particularly growth, are often of more suitable conditions on rich soils (D and E). This implies that nutrient available soils are more favorable than sandy soils to grow C. sempervirens seedling. However, regarding to the similar effects of nutrient available soils (D and E) on seedling characteristics measured, employment of soil D is preferable and more economic, due to the lower proportion of organic matter. Alternatively, infertile soil of A can be suited for this purpose, too.
The results obtained from this study are valid for this specific site and may not be generalized due to lake of replicated periods or sites. However, it can be also suggested that additional investigations to be made to present the results in other sites and in following periods.