共查询到20条相似文献，搜索用时 31 毫秒
1.
Tree-crop interactions were monitored by measuring tree growth characters of Prosopis cineraria L. and Tecomella undulata L. and yields of Vigna radiata (L) in agroforestry systems in degraded lands of Indian Desert. Potential competition for resource between the trees and
associated crop was analyzed by measuring soil water contents, soil organic matters and NH4-N at different depths of soil layers i.e., 0–25 cm, 25–50 cm and 50–75 cm in the experimental plots. The plots size were
16 m × 18 m (D1), 20 m × 18 m (D2) and 32 m × 18 m (D3) with tree densities of 208, 138 and 104 trees·ha−1 after June 2002, respectively. Results showed that tree height increased by 3% to 7% during June 2002 to June 2004. Collar
diameter increased by 30% and 11% in D1, 23% and 19% in D2 and 18% and 36% in D3 plots, respectively, in P. cineraria and T. undulata in two years period. The increase in crown diameter was 9% to 18% in P. cineraria and 11% to 16% in T. undulata. Tree growth was relatively greater in 2002 than in 2003. Yield of V. radiata increased linearly from D1 to D3 plots. Lowest soil water content at 1 m distance from tree base indicated greater utilization of soil water within the tree
rooting zone. Concentrations of soil organic matters and NH4-N were the highest (p<0.05) in 0–25 cm soil layer. P. cineraria was more beneficial than T. undulata in improving soil conditions and increasing crop yield by 11.1% and thus more suitable for its integration in agricultural
land. The yield of agricultural crop increased when density of tree species was appropriate (i.e., optimum tree density),
though it varied with tree size and depended upon resource availability. The result indicated bio-economic benefits of optimum
density of P. cineraria and T. undulata over traditional practices of maintaining random trees in farming system in arid zones.
Biography: G. Singh (1961– ), male, Scientist E and Head, Division of Forest Ecology, Arid Forest Research Institute, New
Pali Road, Jodhpur-342005, India. 相似文献
2.
Alley cropping systems may influence soil water movement and the water budget because of its complex interactions between
crop and tree rooting systems. The objective of this paper was to evaluate water balance and water competition in an alley
cropping system, consisting of deciduous tree wild jujube (Choerospondias axillaris) and economic crop peanut (Arachis hypogaea) within subtropical China. Five treatments (20- by 6-m plots) with three replications were included in this study. The treatments
were monoculture peanut cropping (P), monoculture younger trees (T1), monoculture older trees (T2), peanut intercropped with
younger trees (T1P), and peanut intercropped with older trees (T2P). A multi-layered water balance model, with water movement
between soil layers, was implemented by the measurement of soil water potential using sets of tensiometers during the periods
from March 1999 to December 2002. The spatial and temporal variations of soil water regime indicated that the trees used soil
water below the 60-cm soil depth and alleviated the water stress. The direction of soil water movement indicated that soil
water moved to the tree row, which indicated that trees competed with peanuts for water, especially during the seasonal drought
period. Water competition was related to the tree spacing and tree age. Compared to the tree monoculture systems, the alley
cropping system significantly influenced water budget components and water use patterns, as indicated by the increased evapotranspiration
(6–11%), and decreased net drainage (7–45%), water storage (6–29%), and runoff (50–60%). Furthermore, alley cropping systems
encouraged the rapid growth of trees, and depressed the biomass and yield of peanuts by 20–50% associated with tree shading
effects. The results suggest that competition for water and light must be taken into account when optimizing the alley cropping
system. 相似文献
3.
Between June 1993 and June 1994, 112 farmers in the oil palm (Elaeis guineensis)-cassava (Manihot esclentus) belt of southeastern
Nigeria were interviewed to determine the status and agroforestry potential of Dacryodes edulis. Between 50% and 100% of respondents
in different states within the belt owned D. edulis trees. On average, a farmer owned 9.3 trees, the largest number being
16, by farmers in Imo State. Twenty percent of farmers in the system rated D. edulis their best farm tree. It was present
in all the farm niches: homegardens (51.4%), tree crop plots (20.7%) food crop plots (11.4%), secondary forest/fallow (14.2%)
and virgin forest (2.5%). The tree is planted primarily for home consumption and sale to generate cash. At the current densities,
on-farm D. edulis trees generally did not decrease yield of companion crops or trees. Except for ring weeding around the stem,
D. edulis trees received little or no management attention. More than 50% of the trees produced 33 to 50 kg of fruit tree−1 annually. This is valued at US $0.4 to 0.8 kg−1. Farmers were willing to plant more D. edulis trees provided trees with traits such as less height for easy harvesting of
fruits, larger fruit, more fruits, sweeter fruits and year round production of fruits were available. Possible agroforestry
technologies into which D. edulis may fit include live fences, scattered trees in food crop fields, shade trees in tree crop
plots and contour bund or hedgerow planting. Research is required to determine best tree accessions, canopy management strategies,
optimum tree population and improved methods on post- harvest handling of fruits.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
We studied the effects of two types of selective thinning on beech stands formed by a shelterwood cut in 1910 — with lower number of crop trees and higher thinning intensity (T1) and higher number of crop trees with lower thinning intensity (T2). The stands were thinned in 1980, 1991 and 2001. Despite a lower stand density after thinning, the annual basal area increments of thinned stands in both thinning periods (1980–1991 and 1991–2002) were around 20% higher compared to those of the control (unthinned) stands. The mean annual basal area increment of dominant trees was 30–56% larger in the thinned plots compared to the control plots. Of 176 initial crop trees in the T1, 72% were chosen again during the last thinning. In the T2, 258 crop trees were chosen in the first thinning, and only 62% of these trees were chosen again during the last thinning. Only crown suppression and diameter classes of crop trees significantly influenced their basal area increment when diameter classes, crown size, crown suppression, and social status were tested. In the thinned stands, the dominant trees are more uniformly distributed if compared to the dominant trees in the control plots. Finally, the herbaceous cover and the species diversity were higher in the thinned plots. 相似文献
5.
We investigated the effects of selective logging disturbances on tree diversity and soil characteristics in the Bia Conservation Area in southwest Ghana.The study was conducted in unlogged,29-35 years post-logged and swamp forests using ten 25 m×25 m plots.In total,we identified 310 individual trees belonging to 87 species.Mean ShannonWeiner index was highest in the post-logged forest but there were no significant differences in tree density,dominance,or DBH size class distributions between these forests.Soil physical properties such as pH and bulk density up to 30 cm depth were similar in the two of forests In terms of soil nutrient status,available P,exchangeable K and total N contents were all similar in the unlogged and post-logged forests.Our findings suggest that the effects of logging on tree diversity are comparatively long-term,in contrast to its short-term effects on some top soil physical and chemical characteristics. 相似文献
6.
亚热带常绿阔叶林结构、树种多样性和土壤特性的研究(英文) 总被引：1，自引：0，他引：1
采用样地调查法,对日本冲绳岛北部的亚热带常绿阔叶林的林分结构,树种组成以及土壤特性等进行了调查分析。结果表明,该亚热带林具有林冠低矮、小径木多等特点。林分的平均林冠高度仅10m,平均立木密度达5400株·hm2(≥3.0cmDBH),其中胸径小于10cm的立木占64%。林分胸高断面积为54.4m2·hm-2。30个调查样地共出现树种数(≥3.0cmDBH)达80种,分属31个科。根据树种的重要值,Castanopsis sieboldii和Schima wallichii分别为优势树种和亚优势树种。树种多样性指数(H’)平均达3.63,均衡度指数(J’)为0.71,丰富度指数(S’)为4.72。这些多样性指数都随着优势树种重要值的增加而显著降低。土壤养分测定结果表明,该森林的土壤肥力低,异质性大,并可能存在Al毒害。由相关分析知,林分密度和优势树高均与土壤pH值呈显著正相关关系;多样性指数则与土壤交换性K ,Ca2 以及Ca2 /Al3 比呈显著的正相关,而与土壤有机碳,全氮和磷呈显著的负相关。这些结果说明土壤性质是影响冲绳亚热带常绿阔叶林林分结构和树种组成多样性的重要因素。图3表4参38。 相似文献
7.
Trees in cropped fields may improve nitrogen (N) use efficiency by intercepting leached N, but crop yield will be reduced if the trees compete strongly with crops for N. Ideal trees for intercropping will take up N from deeper soil layers not accessed by the crop species. Spatiotemporal aspects of tree nitrogen capture niches were investigated within a hedgerow intercropping system by placing 15N at three depths and monitoring 15N uptake by trees pruned either 25 or 4 days before application of 15N. Trees with contrasting rooting patterns (Gliricidia sepium L. and Peltophorum dasyrrachis (Miq.) Kurz) were grown in mixed hedgerows and intercropped with maize (Zea mays L.). Neither species showed significant N uptake during the 5-14 days after pruning, even though some shoot regrowth occurred during this time. Mean topsoil (0-5 cm depth) root length density of G. sepium was 520% greater than that of P. dasyrrachis, whereas total root length (0-100 cm depth) of G. sepium was only 450% greater. On average, G. sepium recovered 15 times as much 15N as P. dasyrrachis, following application of 15N at 5 cm depth, but the two species recovered a similar amount following application at 80 cm depth, suggesting that P. dasyrrachis had better niche complementarity with shallow rooting crops. However, both species showed strong plasticity in vertical N uptake pattern in response to competition from establishing maize plants. The species differed in their response: N uptake activity by G. sepium shifted down the soil profile in response to increasing competition from a growing maize crop (uptake from 80 cm depth changed from 4 to 9% of uptake from 5 cm depth), whereas N uptake by P. dasyrrachis became relatively shallow (uptake from 80 cm depth changed from 305 to 25% of uptake from 5 cm depth). Niche avoidance and increased competitiveness within the topsoil represent alternative responses to competition. The response displayed may be related to soil fertility in the species' natural habitats. 相似文献
8.
Pessimistic forecasts often suggest that widely spaced trees enjoying free growth (no competition with other trees) will fail
to provide high quality timber. This challenges the temperate agroforestry practice of planting widely spaced trees to produce
high quality timber. We analyse tree growth data from recent temperate agroforestry plantations aged three to eight years,
featuring low tree plantation densities (50 to 400 stems ha−1), the association of trees with intercrops (silvoarable systems)
or animals (silvopastoral systems), and the use of plastic shelter tubes to protect trees (1.2 to 2.5 m high) and avoid damage
by cattle or sheep in pastures or facilitate maintenance in silvoarable systems. The plantations are located in climates ranging
from Mediterranean, dry central temperate plains, cold and wet central uplands to mild oceanic areas. Some plantations included
a forestry control (high density of plantation, no tree shelter, no intercropping nor grazing). Trees were evaluated for height
and diameter growth and stem form (straightness and absence of knots). Trees in most agroforestry plots grew satisfactorily,
often faster than in forestry control plots. In some experimental plots, average annual height increments as high as 1 m and
diameter increments as high as 1.5 cm were observed. Few agroforestry plantations were unsuccessful, and the reasons for the
failures are discussed: animal damage in silvopastoral plots, but also a wrong choice of tree species unsuitable for local
soil and climate characteristics. From these early results we can formulate some guidelines for designing future agroforestry
plantations in temperate climates, concerning tree density, use of tree shelters and care required for widely spaced trees.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Soil properties under Acacia nilotica trees in a traditional agroforestry system in central India 总被引：2，自引：0，他引：2
Acacia nilotica (L.) Willd. ex Del is an important multipurpose tree of traditional agroforestry system in the central belt of the Indian
sub-continent. The tree is reported to reduce crop yields under its canopy. However, information is lacking on the spatial
variation in soil physical characters, nutrient pool sizes and their availability to crops under its canopy. The present study
reports influence of three tree canopy positions, viz. mid canopy, canopy edge and canopy gap, of Acacia nilotica (≥ 12 years) on texture, organic C, total and mineral N and P, and soil pH, in 0 to 10, 10 to 20 and 20 to 30 cm depth of
the soil at ten sites in a traditional agroforestry system. Sand particles declined by 10% and 9% whereas clay particles increased
by 14% and 10% under mid canopy and canopy edge, respectively, compared to that under canopy gap. Clay particles did not decline
significantly with soil depth under all canopy positions. Proportion of silt particles was not influenced by the canopy position.
Soil organic C, total N, total P, mineral N (NO3
−-N and NH4
+-N) and P were greater under mid canopy and canopy edge positions compared to canopy gap. Soil organic C and N pool sizes
were maximum in 0 to 10 cm and declined with the depth of soil. Total and mineral P contents were nearly uniform across the
depths. C/N ratio tended to increase with the soil depth whereas C/P ratio declined.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
We have evaluated the effects of improving substrate fertility on the growth and reproduction of a P. halepensis plantation in a restored limestone quarry on a stony calcareous regolith (R plots). The natural substrate was supplemented
by adding a 0.2 m layer of a fine textured soil (RS plots) or a sewage sludge amended soil (RSS plots). The treatments were
performed when the pines were 7 years old, and tree growth (height and trunk and canopy diameter) was monitored over the subsequent
12 years. The reproductive status of the trees was also measured when the pines were 20 years old. Tree growth was proportional
to the amount of soil nutrients: 12 years after treatment the mean height of the R, RS and RSS trees was 1.5, 3.1 and 6.2 m
respectively and growth increases over the baseline were 76, 264 and 632%. The treatment also affected the age of onset of
reproduction (15, 11 and 9 years, respectively), the average number of cones per tree (12, 43 and 61), and the amount of seeds
per cone (37, 52 and 72), but did not modify the germination percentage of pine seeds (ca 71.5%). Soil organic carbon increased
proportionally to the vegetation development, contributing to carbon sequestration. These results suggest that improving the
nutritional status of the soil not only improves the growth of trees, but it also ameliorates their reproductive ability (earlier
reproduction onset and larger seed crop size). Implications for soil restoration through afforestation are also discussed. 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(6):427-435
ABSTRACTTotal and soluble nutrients in peat were studied after ash fertilization on an oligotroph peatland in southeast Norway. Plots 15?m?×?15?m in size were fertilized with 0, 4, 7, and 10 tons ha1 of wood or peat ash in 1944. Chemical analyses after 18, 35 and 48 years showed a gradual reduction of phosphorus (P) and calcium (Ca) from the 0 to 10?cm surface peat layer. Some of the leached Ca was recovered in the layers 10–20 and 20–40?cm, while hardly any of the lost P was recovered in this way. The amount of potassium (K) in the surface layer declined by 75% over the first 18 years, and remained stable thereafter. Nothing of the lost K was recovered in deeper layers. The pH reflected the Ca levels. Over the years, an increasing proportion of the applied P, K and Ca was retrieved in the trees. Needle analyses indicated that declining tree vigor on plots fertilized with 4 and 7 tons of ash ha?1 was due to P limitations. After 48 years, the peat content of P and Ca was still significantly higher in fertilized than in control plots, thus demonstrating the long-lasting effect of ash fertilization. 相似文献
12.
The spatial and temporal evolution of soil water content (θ) in Quercus ilex dehesas has been investigated to determine how trees modify the soil water dynamics and the nature of tree-grass interactions in terms of soil water use in these ecosystems. Soil physical parameters and θ were measured at different distances from the tree trunk (2–30 m) in the upper 300 cm of soil. θ was measured monthly by TDR during 2002–2005. Tree water potential was determined during the summers of 2004 and 2005. At deeper soil layers, mean θ values were higher beyond than beneath tree canopy during dry periods. θ depletion beyond tree canopy continued even in summer, when herbaceous plants dried up, suggesting that trees uptake water from the whole inter-tree space. Results have shown a high dependence of trees on deep water reserves throughout late spring and summer, which helps to avoid competition for water with herbaceous vegetation. 相似文献
13.
Plant-soil-water relations of a silvopastoral system composed of a Douglas-fir (Pseudotsuga menziesii) timber crop, subterranean clover (Trifolium subterraneum) as a nitrogen-fixing forage, and tall fescue (Festuca arundinacea) as a forage crop were investigated near Corvallis, Oregon, during 1983–1986. Treatments included all possible combinations of two tree-planting patterns (trees planted 2.4 m apart in a grid, and groups of five trees spaced 7.6 m between clusters) and two grazing/understory management systems (agroforests were seeded to subclover and grazed by sheep; forests were unseeded and ungrazed).Mean twig xylem water potential (XWP) for Douglas-fir trees ranged from –0.3 to –1.5 MPa on forest plots and from –0.3 to –1.2 MPa on agroforest sites. Pre-dawn and sunset XWP were more negative for forest than for agroforest plots during dry summer periods. Midday XWP was similar for both agroforest and forest plots on all dates. Soil water content at 50–100 cm depth was greater under agroforest plots as compared to forest plots in 1984, but not in 1985 (unusually dry spring). Average foliage nitrogen content of tree needles was 1.54% vs. 1.43% for agroforests vs. forests, respectively.Our data are consistent with the hypotheses that: (1) grazing of understory vegetation may reduce water stress of trees during dry periods by reducing transpirational water use by the forage plants; and (2) nitrogen-fixing vegetation combined with grazing increases nitrogen uptake of associated trees. However, neither mean foliar N nor average XWP differences experienced by trees in agroforest versus forest plantations were sufficient to have an effect on tree growth. Our data demonstrate that it is possible to produce a second crop (i.e. forage grazed by sheep) in timber plantations without reducing the growth of the main tree crop.Submitted as Oregon Agrocultural Experiment Station Technical Paper No. 10109. 相似文献
14.
Thomas J. Kumar B.M. Wahid P. A. Kamalam N. V. Fisher R. F. 《Agroforestry Systems》1998,41(3):293-305
To acquire information on the nature of belowground interactions in intercropping system involving ginger, Zingiber officinale
Roscoe, and Ailanthus triphysa (Dennst.) Alston, their root activity was evaluated based on 32P recovery by each species in
mixed and sole crop situations. Treatments included two Ailanthus densities (1,111 and 3,333 tress ha−1) and four lateral
distances of 32P application (10 and 20 cm from the treated ginger plant and 20 and 40 cm from the treated Ailanthus trees).
Recovery of 32P in ginger foliage increased with time, irrespective of tree population density and lateral distance of isotope
application. Lack of significant variations in 32P recovery as a function of tree population density suggests that tree density
is probably not a strong determinant of belowground competition in the well-fertilised, manured and mulched system studied
(at least till four years after tree planting). Nonetheless, neighbouring Ailanthus trees absorbed a substantial potion of
the 32P supplied to ginger. This, in turn, suggests that the effective root zones of ginger and Ailanthus may overlap. Data
on 32P uptake of Ailanthus suggest that 41% to 59% of the root activity is concentrated within a zone of about 40-cm distance
from the trunk. Neighbouring trees in the high density stands absorbed significantly more 32P than those in low density stands
(P < 0.01 at 30 and 45 days after 32P application). Our observations also suggest that competition between the tree and the
herbaceous crop for nutrients applied to the tree component is unlikely in the Ailanthus-ginger mixed species system studied.
Therefore, from a crop management perspective, it is better to fertilise the herbaceous component of the mixed species system
adequately, as it will also benefit the tree component. Nutrient use efficiency may be higher under such situations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
A hedgerow intercropping study was conducted for 7 years in West Sumatra, Indonesia on an acid and highly A1-saturated (72%) soil to determine growth and yield responses of tree hedgerows and upland rice and cowpea intercrops. Three tree species,Paraserianthes falcataria, Calliandra calothyrsus, andGliricidia sepium, and a no tree control were planted at three lime rates of zero, 375 kg ha–1, and liming to 25% Al+H saturation. Annual fertilizer inputs of 20 kg P and 50 kg K ha–1 were kept low to approximate low input farming systems. The trees were pruned 4 to 6 times per year and prunings applied to the intercrops.Paraserianthes andCalliandra grew vigorously, whileGiricidia grew poorly and was replaced after four years withFlemingia macrophylla. Hedgerow growth and yields were reported in a previous paper [Evensen et al., 1994].Rice and cowpea yields initially increased with lime andParaserianthes pruning application, but yields and soil cations (Ca, Mg, and K) declined until fertilizer inputs were increased after four years. Thereafter, crop yields increased and soil cations returned to original levels. Soil C and N were maintained over the 7 years on plots with trees. These results indicate little build-up of nutrient cations due to recycling by the trees and suggest that successful alley farming on such highly weathered soils requires maintenance of soil fertility with external inputs. 相似文献
16.
不同密度杉木幼林系统生产力和生态效益研究 总被引：6，自引：2，他引：4
杉木幼林系统是由４个不同密度级处理系列小区组成,栽植密度为１６６５、３３３０、４９９５和６６６０株／ｈｍ＾２（以下分别用Ａ、Ｂ、Ｃ和Ｄ代替）。这些小区土壤质地及地形别无二致,都是用１年生实生苗１９８７年春天定植。８年生时调查了这些幼林系统林木生长、冠层厚度、枝下高以及生态效益等。随着密度由Ａ增加到Ｄ：平均胸径生长量从８．１ｃｍ降到６．６ｃｍ;平均树高生长量由５．９ｍ降至５．４ｍ;平均冠层厚度自４． 相似文献
17.
《Forest Ecology and Management》2006,233(1):143-148
The influence of different in situ rainwater harvesting and moisture conservation methods on soil moisture storage and growth of Tamarix ramosissima was studied in the semiarid loess region of China from 2002 to 2004. The treatments included control (T1), trench (T2), saucer covered by plastic film (T3), bare ridge and bare furrow (T4), plastic-covered ridge and bare furrow (T5), and plastic-covered ridge and gravel-covered furrow (T6). The results indicated that soil water storage for the T5 and T6 was significantly higher than the control. The T6 treatments produced the highest amount of soil water storage, 18–137 mm more than the controls at soil depth of 0–100 cm and 40–75 mm at soil depth of 100–200 cm. No significant differences in soil water storage were found between the T2, T3, T4 and the control treatments at soil depth of 0–100 cm, but soil water storage at soil depth of 100–200 cm was significantly higher for the T2, T3, T4 treatment than the control.Rainwater harvesting and moisture conservation treatments increased growth of T. ramosissima, tree height was significantly higher for the rainwater harvesting and moisture conservation treatments than the controls. Tree height, crown diameter and collar girth for the T6 treatments increased by 70, 57 and 79% as compared to the controls. No significant differences in crown diameter and collar girth were observed between T1, T2 and T3 or T4 and T5 treatments in some years. The effectiveness of the different treatments for the tree height, crown diameter and collar girth was in the order of T6, T5, T4, T3, T2 and T1. 相似文献
18.
Kindu Mekonnen Roland J. Buresh Richard Coe Kering Maru Kipleting 《Agroforestry Systems》1998,42(3):265-282
Measurements of root and nutrient distributions in agroforestry systems have often been obtained from unreplicated plots.
We, therefore, measured the vertical and horizontal distribution of root length and soil nitrate in replicated plots of sesbania
[Sesbania sesban (L.) Merr.] to assess plot-to-plot variation and identify appropriate sampling schemes. Sampling was on profile
walls exposed from pits at two on-farm sites (Ochinga and Muange) in Kenya. At Ochinga, soil was sampled at 27 0.15-m depth
intervals and eight 0.15-m-wide locations perpendicular to 2.25-m-wide rows of 19-month-old sesbania. At Muange, sampling
was 18 months after establishment of sesbania from seedlings with a 1 m by 1 m spacing. Soil was sampled at 17 0.15-m depth
intervals and nine 0.15-m-wide sampling locations – one exactly below the tree and four each on opposite sides of the tree.
Root length density generally decreased with distance from sesbania and with soil depth. Soil nitrate, however, followed different
trends in the four replications at Ochinga and the three replications at Muange. At Ochinga, nitrate above 2.5-m depth clearly
increased with distance from the tree in two replications but followed no distinct trend in another replication. At Muange,
nitrate above 1.2-m depth decreased with distance from the tree in one replication, increased with distance from the tree
in another replication and followed no clear trend in another replication. The suitability of various sampling schemes for
measuring root length and nitrate was accessed from percent bias between measured values at sampling locations in the scheme
and actual values for an entire transect of sampling locations. Bias associated with selection of sampling locations tended
to be higher within the 2.25-m-wide sesbania rows than the 1 m by 1 m sesbania spacing. Soil sampling in systems with rows
of young trees should be at several locations along a transect perpendicular to tree rows in order to minimize bias.
This revised version was published online in June 2006 with corrections to the Cover Date.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
晋西黄土区主要造林树种单株耗水量研究 总被引：1，自引：0，他引：1
依据水量平衡原理,采用桶栽试验分别测算晋西黄土区主要造林树种侧柏、刺槐、杏和河北梨生长季(4-10月)单株耗水量,并根据林地土壤水分动态及土壤水分特征曲线标定的各树种无效水界值,分析各树种土壤水分供耗特点及其有效性.结果表明:1)2002年(贫水年)生长季降水量430.7 mm,试验树种同期耗水量约为430～490 mm,供耗失衡;2003年(丰水年)降水量870.2 mm,耗水量约为480～515 mm,但降雨分配不均,5、10月供耗也略有失衡.2)不同树种年内土壤含水量变化趋势相近,而同月耗水量差异较大,同一树种不同月耗水量差异也较大,丰水年各试验地土壤水分状况要好于贫水年.3)侧柏、刺槐、杏和河北梨无效水界值分别为8.0%、8.4%、9.2%和9.7%,侧柏较其他3个树种利用水分能力强;贫水年林外单株树木土壤含水量在一段时间内低于对应树种的无效水界值,影响树木正常生长;单株树木依靠冬季和次年春季降水补充,生长季初期都能恢复到速效水水平. 相似文献
20.
《Scandinavian Journal of Forest Research》2012,27(3):217-233
The effects of wood ash or wood ash plus nitrogen (N) fertilization on soil chemical properties, needle nutrient concentrations and tree growth were studied in five coniferous stands, aged 31–75 yrs, after 5 and 10 yrs. In each experiment 3 t ha?1 of loose wood ash was applied to three replicated plots (30×30 m). In three of the experiments 120–150 kg N ha?1 was applied together with the same wood ash (WAN). These three experiments also included a stand-specific fertilization (SSF) treatment, which consisted of 120, 150 or 180 kg N ha?1. Five years after wood ash or WAN application the pH increase in the humus layer was 1–1.7 pH-units and in the 0–5 cm mineral soil layer 0.3–0.4 pH-units. The increase was approximately the same 10 yrs after application, and was also associated with an increase in pH in the 5–10 cm mineral soil layer. Wood ash or WAN significantly increased both the total and extractable calcium and magnesium concentrations in the humus layer on all the sites. Wood ash or WAN had an increasing effect on the boron concentrations, but a decreasing effect on the manganese concentrations in the needles. Wood ash had no significant effect on the volume growth. The trees on the WAN plots grew as well as or slightly better than those on the SSF plots. 相似文献