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1.

Faidherbia albida is one of the scattered trees commonly intercropped with most cereals in Ethiopia due to its positive impacts. The tree is pruned for various purposes including for fencing and fuelwood. In this study, the impact of pruning on water relations of F. albida and on understorey wheat productivity was investigated. The on-farm study was conducted in Ejerssa Joro, semi-arid Ethiopia. Six mature trees were selected; three were fully pruned and three were left unpruned. Sap flow and leaf water potential were measured on these trees. Crop gas exchange, aboveground biomass and grain yield were measured under and outside tree canopies. The highest and the lowest sap volumes, recorded from unpruned F. albida, during the dry period, were 153 L day?1 and 20 L day?1, respectively. The highest and the lowest sap volumes were 13.4 L day?1 and 0.04 L day?1 recorded during the wet period. Wheat CO2 assimilation was highest (7.8 µmolm?2 s?1) at 1 m distance and declined away from the tree trunk under unpruned trees. Aboveground biomass and grain yield under unpruned treatments were significantly (P?<?0.05) higher than outside of canopy of same tree and outside canopies of pruned trees. Pruning reduced aboveground biomass and grain yield by 30% and 27%, respectively; despite the higher water uptake by unpruned trees. We recommend that intensive pruning of F. albida be discouraged and propose further studies on optimal pruning for increased food production and provision of tree products to meet farmers’ needs.

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2.
Scattered trees and woodlots are a prominent feature of agricultural landscapes of Rwanda. However, little is known about their characteristics and their contribution to farmers’ wood needs. Here, we present the results of a survey of (a) the abundance, composition, and size of trees and woodlots in the low, medium and high altitude regions of Rwanda, (b) total woody biomass and biomass for fuelwood at farm and landscape levels, and (c) opportunities for their sustainable use. Scattered trees occurred in all landscapes at minimum densities ranging from 20 to 167 trees ha?1. Of the 56 tree genera recorded, a handful of tree species dominated, with the ten most common species accounting for over 70 % of all trees recorded. Most of them provided fuelwood, fruit and timber to farm owners. Woodlots occurred on about 40 % of the survey farms and consisted for 90 % of eucalyptus coppice. Woody biomass dry weight of scattered trees on agricultural landscape was 0.7 t ha?1 in low altitude region (LAR), 3 t ha?1 in medium altitude region (MAR), and 1 t ha?1 in high altitude region (HAR). Dry weight woody biomass in woodlots (<0.5 ha) was the highest in MAR (221 t ha?1), followed by that in HAR (205 t ha?1) and least in LAR (96 t ha?1). About 80 % of total woody biomass in trees and woodlots on farmland was useable biomass for fuelwood, indicating that the production of fuelwood on agricultural land was important. Woody biomass on agricultural land was higher than that in forest plantations, and was potentially sufficient to reduce the gap between fuelwood supply and demand when the entire agricultural area was taken into account. In order to achieve this on agricultural land, while contributing to food security and environmental conservation as well, smallholder farmers must be provided with incentives to grow woodlots and to adopt agroforestry systems, thereby considering the trade-offs with agricultural production. Strategies to encourage smallholder farmers to increase the use of agroforestry have to account for the farmers’ ecological and socioeconomic conditions.  相似文献   

3.
We observed the influence of five different altitudes and prevailing agro ecosystems on biomass and carbon sequestration potential in Kullu district of Himachal Pradesh, India. The study area had five prevailing land uses viz., agriculture, agro-horticulture, horticulture, silvi-pasture, and forest at four elevations representing about 1 °C temperature change. The results showed that maximum total biomass of 404.35 Mg C ha?1 was accumulated by forest landuse and followed a decreasing trend in the order as forest > silvi-pasture > agro-horticulture > horticulture > agriculture. Similar trends were also seen with respect to biomass carbon (C) density and C-sequestration potential of different land uses. Biomass and carbon density potential enhanced with the increase in the altitudinal ranges from 1100–1400 to 2000–2300 m a.s.l. But, the rate of C-sequestration potential enhanced from 1100 to 2000 m and declined at 2000–2300 m a.s.l. Maximum carbon density (393.29 Mg C ha?1) of both plant as well as soil was displayed by the forest-based land use systems situated at an altitudinal gradient of 2000–2300 m a.s.l. The rate of C-sequestration was maximum (2.17 Mg ha?1) in the agro-horticulture at 2000–2300 m a.s.l. This study brings out the potential of different land use systems influenced by varying factors on their C-sequestration potential in western Himalayan elevation gradient, thereby providing useful information for effective management in a climate change mitigation and carbon budget.  相似文献   

4.
Cacao trees under different shade tree shelter: effects on water use   总被引：1，自引：1，他引：0  
We asked how shade tree admixture affects cacao water use in agroforests. In Central Sulawesi, Indonesia, cacao and shade tree sap flux was monitored in a monoculture, in a stand with admixed Gliricidia trees and in a mixture with a multi-species tree assemblage, with both mixtures having similar canopy openness. A Jarvis type sap flux model suggested a distinct difference in sap flux response to changes in vapor pressure deficit and radiation among cacao trees in the individual cultivation systems. We argue that differences originate from stomatal control of transpiration in the monoculture and altered radiation conditions and a different degree of uncoupling of the VPD from the bulk atmosphere inside shaded stands. Probably due to high sap flux variability among trees, these differences however did not result in significantly altered average daily cacao water use rates which were 16 L day?1 in the multi-species assemblage and 22 L day?1 in the other plots. In shaded stands, water use of single cacao trees increased with decreasing canopy gap fraction in the overstory since shading enhanced vegetative growth of cacao fostering transpiration per unit ground area. Estimated transpiration rates of the cacao tree layer were further controlled by stem density and amounted to 1.2 mm day?1 in the monoculture, 2.2 mm day?1 for cacao in the cacao/Gliricidia stand, and 1.1 mm day?1 in the cacao/multi-species stand. The additional transpiration by the shade trees is estimated at 0.5 mm day?1 for the Gliricidia and 1 mm day?1 for the mixed-species cultivation system.  相似文献   

5.
The changes in species composition, abundance and forest stand structure were analyzed across altitudinal regimes in tropical for- ests of Eastern Ghats of northern Andhra Pradesh, India. Three 1-ha plots were established with one each in low, medium and high altitudes. A total of 153 species, 2129 stems (709 stems ·ha -1 ) of ≥10 cm girth were enumerated. Species richness and diversity pattern varied along altitud- inal gradient and increased with the altitude. Species richness varied from 52 to 110 species·ha -1 and stand density from 639 to 836 stems·ha -1 with average basal area of 34.39 m 2 ·ha -1 . Shannon-Wiener index (H’) ranged from 4.55 to 5.17. Low altitude (i.e., Site 1) is dominated by Xylia xylocarpa (59.22) and Lagerstroemia parviflora (23.90), medium altitude (i.e., Site 2) by Xylia xylocarpa (45.50) Bursera serrata (17.29), and high altitude (i.e., Site 3) has Schleichera oleosa (28.25) Pterocarpus marsu- pium (26.55) as predominant species. Taxonomically, Rubiaceae (12 species), Fabaceae (12), Euphorbiaceae (11), Rutaceae (7) and Lauraceae (7) were dominant families. Density-wise, Fabaceae, Combretaceae, Euphorbiaceae, Anacardiaceae and Myrtaceae were abundant. Thus, conservation assessment based on altitudinal regimes and the information on species structure and function can provide baseline information for monitoring and sustaining the biodiversity.  相似文献   

6.
The purpose of this study was to investigate how forests on subtropical mountains, which resembled tropical and temperate forests, were assembled, and to examine the compression and overlap of vegetations. We established 344 sample plots (400 m2) located at different altitudinal gradients ranging from 16 to 3,500 m above sea level (ASL) in Hsueshan Range northern Taiwan. Vegetation types were classified by TWINSPAN and the results of DCA were used to analyze the changes in vegetation types along elevation. Vegetation I was composed of the species of Euphorbiaceae, Moraceae, and Rubiaceae, which were taxa of tropical floristic elements, and the extent of this vegetation was limited below 1,500 m ASL. Vegetation II was defined into two subtypes, which were distributed from 1,000 to 2,500 m ASL, and were composed predominantly of Chamaecyparis and Tsuga, respectively. Our data also revealed that vegetation II contained co-dominants of species from families Lauraceae and Fagaceae. Moreover, evergreen broadleaved trees similar to tropical mountain forests were found to have narrower altitudinal ranges on subtropical mountains, whereas coniferous forests resembled temperate areas and were characterized by endemic conifer species. Vegetation III, from 2,500 to 3,500 m ASL, was characterized by endemic conifer species, Abies and Tsuga. Interestingly, deciduous forest was almost absent in this area and Fagus was the only tree type on a small mountain ridge. Data obtained from this study will help in raising conservation awareness for subtropical mountains since unique patterns of compression and overlap characteristics of tropical and temperate resembling forests were evident.  相似文献   

7.
Few studies have analyzed how tree species within a mixed natural forest affect the dynamics of soil chemical properties and soil biological activity. This study examines seasonal changes in earthworm populations and microbial respiration under several forest species (Carpinus betulus, Ulmus minor, Pterocarya fraxinifolia, Alnus glutinosa, Populus caspica and Quercus castaneifolia) in a temperate mixed forest situated in northern Iran. Soil samplings were taken under six individual tree species (n = 5) in April, June, August and October (a total of 30 trees each month) to examine seasonal variability in soil chemical properties and soil biological activity. Earthworm density/biomass varied seasonally but not significantly between tree species. Maximum values were found in spring (10.04 m?2/16.06 mg m?2) and autumn (9.7 m?2/16.98 mg m?2) and minimum in the summer (0.43 m?2/1.26 mg m?2). Soil microbial respiration did not differ between tree species and showed similar temporal trends in all soils under different tree species. In contrast to earthworm activity, maximum microbial activity was measured in summer (0.44 mg CO2–C g soil?1 day?1) and minimum in winter (0.24 mg CO2–C g soil?1 day?1). This study shows that although tree species affected soil chemical properties (pH, organic C, total N content of mineral soils), earthworm density/biomass and microbial respiration are not affected by tree species but are controlled by tree activity and climate with strong seasonal dynamics in this temperate forest.  相似文献   

8.
Coarse woody debris (CWD) is involved in important forest ecosystem functions and processes, e.g., habitat provision, water retention, and organic matter decomposition. However, a quantitative, CWD-produced soil organic carbon (SOC) imprint has not yet been detected, possibly due to lack of free adsorption sites on soil minerals. To circumvent this potential constraint, we selected plots with and without CWD in a beech (Fagus sylvatica L.) primeval forest in the West Carpathian volcanic range (Slovakia). Local andic soil contains abundant allophane and amorphous Fe-compounds as important SOC binding agents. The C concentration in the fine earth of sampled soils was determined by the dry combustion method. We established that organic carbon concentration decreased with depth from 0.20 kg kg?1 (0.0–0.3 m) to 0.11 kg kg?1 (0.3–0.5 m) in soil with CWD and from 0.13 kg kg?1 (0.0–0.3 m) to 0.07 kg kg?1 (0.3–0.5 m) in soil without CWD. The respective average differences in soil organic carbon concentration (0.07 kg kg?1) and stock (15.84 kg m?2) between the two series of plots within the upper 0.3 m were significant according to the t test (P < 0.05 or P < 0.01, respectively). Also, corresponding differences within the 0.3–0.5 m layer (0.04 kg kg?1 and 5.51 kg m?2) were significant (P < 0.05, P < 0.001). Our results represent the first indication that CWD-produced SOC imprint may reach deeper than just a few centimeters in soils featuring high adsorption capacity, such as Andosols.  相似文献   

9.
Recent re-measurements of silvicultural trials in conifer plantations on nutrient-poor cedar-hemlock (CH) cutovers on northern Vancouver Island have confirmed co-limitation by nitrogen and phosphorus. Repeated fertilization increased volumes of both cedar and hemlock on CH sites (at 2,500 stems ha?1) by about 100 m3 ha?1 relative to unfertilized plots 22 years following initial fertilization, and increased the productivity of regenerating conifers to a level approximating that of neighbouring hemlock-amabilis fir (HA) sites. More surprising was the response to fertilization on the more-productive HA sites. After 22 years, cedar in fertilized HA plots had produced an extra 180 m3 ha?1 compared to unfertilized HA plots, while hemlock had produced an extra 250 m3 ha?1 in fertilized plots (at 2,500 stems ha?1). Thus, contrary to expectations, the greatest volume responses of both hemlock and cedar to fertilization occurred on the good (HA) sites rather than on the poor (CH) sites. Ecological studies of CH and HA sites supported the hypothesis that the poor nutrient supply and productivity of CH sites is a long-term consequence of excessive moisture, and that the two site types bracket a critical ecological threshold of moisture, aeration and redox.  相似文献   

10.
The effect of different planting densities (100,000 and 167,000 plants ha?1) and levels of nitrogen fertilization (0, 261, 521, and 782 kg N ha?1 year?1) on biomass production and chemical composition of Moringa oleifera was studied in a split-plot design with four randomized complete blocks over 2 years with eight cuts year?1 at the National Agrarian University farm in Managua, Nicaragua (12°09′30.65″N, 86°10′06.32″W, altitude 50 m above sea level). Density 167,000 plants ha?1 produced significantly higher total dry matter yield (TDMY) and fine fraction yield (FFDM), 21.2 and 19.2 ton ha?1 respectively, compared with 11.6 and 11 ton ha?1 for 100,000 plants ha?1. Growth rate in 167,000 plants ha?1 was higher than in 100,000 plants ha?1 (0.06 compared with 0.03 ton ha?1 day?1). Average plant height was 119 cm irrespective of planting density. Fertilization at the 521 and 782 kg N ha?1 year?1 levels produced the highest TDMY and FFDM in both years of the study and along all cuts. The interaction between cut and year was significant, with the highest TDMY and FFDM during the rainy season in the second year. Chemical composition of fractions showed no significant differences between planting densities. Significantly higher crude protein content was found in the coarse fraction at fertilizer levels 521 and 782 kg N ha?1 year?1 (87.9 and 93.7 g kg?1 DM) compared with lower levels. The results indicate that Moringa can maintain up to 27 ton ha?1 dry matter yield under dry tropical forest conditions over time at a planting density of 167,000 plants ha?1 if the soil is regularly supplied with N at a level of approximately 521 kg ha year?1 in conditions where phosphorus and potassium are not limiting.  相似文献   

11.
H. T. Tate  T. Page 《New Forests》2018,49(4):551-570
Developing methods for routine clonal propagation of sandalwood (Santalum austrocaledonicum) is important for its domestication and development as a commercial agroforestry species. The amenability of this species to propagation by leafy stem cuttings in low-cost non-mist propagators was assessed in four separate experiments. These experiments evaluated the effects of (1) genotype (15 genotypes from two island provenances), (2) cutting position on the stock plant (apical, medial and basal), (3) cutting size (1-node/400 mm2 and 2-node/800 mm2 leaf area), (4) three propagation media [scoria (5 mm, air-filled porosity (AFP)—29%), vermiculite and perlite (1:1 v/v, AFP—46%) and vermiculite, perlite and peat (2:2:1 v/v/v, AFP—42%)], (5) indole-3-butyric (IBA) (3000, 4000 and 8000 ppm) and (6) irradiance in the propagator [daily light integral (DLI) 5.3, 3.9, 2.6, 2.2 mol m?2 day?1]. IBA, propagation media and cutting size had no significant effect on rooting percentage, root number or root growth. Evidence of provenance-based variation in rooting capacity was recorded with greater rooting success for genotypes from the island of Erromango compared with Tanna. Variation in adventitious root induction was also recorded between individual genotypes from Erromango across all four experiments. Cuttings collected from the apical and medial parts of the shoot on the stock plant had higher rooting percentage than those collected from the base. Differences in rooting capacity between apical and medial shoots were variable between experiments and may be attributed to different levels of hardening. The use of artificial shade (~?70%) to achieve a mean DLI of between 2.6 and 3.9 mol m?2 day?1 increased rooting percentage compared to both lower (2.2 mol m?2 day?1 or?~?90% shade) and higher (5.3 mol m?2 day?1 or?~?50% shade) irradiance treatments. Leaf retention of cuttings in the propagator was positively associated with the percentage of cuttings with adventitious roots, with highest percentage in cuttings with full leaf retention, regardless of original cutting size. This study demonstrated S. austrocaledonicum seedlings can be successfully propagated by cuttings provided the propagation conditions are optimized for each genotype.  相似文献   

12.
Composition and structure of the main forest types, as well as the species changes under disturbance, were described as the representation of the forest vegetation in the north slope of Changbai mountain, northeast China. There were 3 forest zones from 600 m to 2,000 m asl, (1) broad-leaved-conifer mixed forest zone, 600–1,100 m asl, dominated byPinus koraiensis, Tilia amurensis, Acer mono, Ulmus japonica, (2) coniferous forest zone, 1,100–1,700 m asl, dominated byPicea jezoensis var.komarovii, P. koraiensis, Abies nephrolepis, and (3)Betula ermanii forest zone, 1,700–2,000 m asl, dominated byBetula ermanii, except for the east slope which was occupied byLarix olgensis. The evergreen component increased with elevation up to the upper limit of the coniferous forest zone (1,700 m), but disappeared in theB. ermanii zone. Species richness was significantly related to elevation. Towards higher elevation, the lapse rate of species-number was 1.6 species per 100 m, and it was only one species near the timberline. Species richness was reduced sharply under intensive disturbance, such as clear cutting, windfalletc. The species diversity was very low in the early stage of succession, and high in the later.  相似文献   

13.
Aboveground biomass and carbon stock in the largest sacred grove of Manipur was estimated for trees with diameter [10 cm at 1.37 m height.The aboveground biomass,carbon stock,tree density and basal area of the sacred grove ranged from 962.94 to 1130.79 Mg ha~(-1),481.47 to 565.40 Mg ha~(-1) C,1240 to 1320 stem ha~(-1) and79.43 to 90.64 m~2 ha~(-1),respectively.Trees in diameter class of 30–40 cm contributed the highest proportion of aboveground biomass(22.50–33.73%).The aboveground biomass and carbon stock in research area were higher than reported for many tropical and temperate forests,suggesting a role of spiritual forest conservation for carbon sink management.  相似文献   

14.
Short rotation coppice (SRC) is seen as a successful management system, which in addition to energy wood production may enhance soil carbon sequestration. The objective of this study was to investigate total, labile and stable soil carbon fractions at SRCs composed of poplar clones Max 1 (Populus nigra x P. maximowiczii), Muhle Larsen (Populus Trichocarpa), and black locust (Robinia pseudoacacia L.). Study was conducted at three SRC sites (Allendorf, Dornburg, and Forst) varying in age (1–4 years old), soil texture and climatic characteristics, in Germany. Composite soil samples collected at SRCs from 0 to 3; 0–10; 10–30; and 30–60 cm depth layers were compared with soils collected from adjacent crop strips. Samples were analysed for total organic carbon (TOC), hot-water extractable carbon (HWC), and organic carbon (OC) at 250–2,000; 53–250; and <53 µm soil-size aggregates. Total OC stocks in 0–60 cm soil layer were the highest at the site with the heaviest texture, Dornburg, followed by Forst and Allendorf, comprising 92–107; 59–74; and 53–64 Mg ha?1, respectively. Although no significant differences in the total OC stocks between SRCs and adjacent crops were found for the 0–60 cm layer, a significantly (p < 0.05) higher TOC, HWC, OC at macro-aggregates (250–2,000 µm), and the amount of macro-aggregates were found in the top 0–3 cm layer in all SRC sites (except the youngest poplar SRC in Forst) compared to adjacent crop strips. A greater macro-aggregate formation in SRCs related to the lower soil disturbance compared to the tilled crops, revealed a potential of SRC for C sequestration, as C occluded within soil aggregates has a slower decomposition rates and longer residence time.  相似文献   

15.
A major challenge for cocoa producers in Côte d’Ivoire is to seek alternative shade trees or crop associations to adapt their planting devices and techniques to the shortage of forests. The recent tendency developed by farmers is to plant simplified orchards combining cacao and fruit trees. An on-farm trial was set up in a 5-year-old cocoa farm to compare a cacao monocrop planted at densities of 1,115 trees ha?1 with cacao intercropped with orange or avocado trees, both at 44 trees ha?1. Observations were done on incident light received by the cacao, vigour, growth and cocoa yields. On average, the cacaos received 100 % light in the monocrop, 89.6 % under orange trees and 80.6 % of incident light under avocado trees. They yielded 64.0 pods tree?1 year?1 in the monocrop (equivalent to 2.54 kg dry cocoa beans tree?1), 30.3 pods tree?1 when combined with orange trees and 28.3 pods tree?1 with avocado trees. The two combinations allowed cocoa yields equivalent to those observed in the region (0.58 kg dry cocoa beans tree?1). Vigour and yield were very highly correlated with the incident light received. Both the yield and the incident light are a logistic function of the planting distance from the shade tree. The inflexion point of the logistic functions corresponds to the minimum planting distance between the cacao and the intercropped fruit trees. On this basis, we suggest that the cacaos should not be planted closer than 6.50 ± 0.2 m to the orange or avocado trees.  相似文献   

16.
Seedlings of six provenances of Betula pubescens Ehrh. from different latitudes (59–70°N) were grown under six ozone exposure regimes by combining different concentrations and daily exposure periods. The different treatments at increasing O3 exposure over 40 nmol mol?1 (AOT40 given in parentheses) were: 19 nmol mol?1/24 h day?1 (0.1 μmol mol?1‐h), 42 nmol mol?1/12 h day?1 (2.5 μmol mol?1‐h), 44 nmol mol?1/24 h day?1 (7.1 μmol mol?1‐h), 76 nmol mol?1/6 h day?1 (9.4 μmol mol?1‐h), 75 nmol mol?1/12 h day?1 (17.8 μmol mol?1) and 116 nmol mol?1/6 h day?1 (19.8 μmol mol?1) for 40 days at a 24 h day?1 photoperiod in growth chambers placed in a greenhouse. The effect of increasing the O3 exposure from 19 nmol mol?1/24 h (0.1 μmol mol?1‐h AOT40) to 42 nmol mol?1/12 h (2.5 μmol mol?1‐h AOT40) was a decrease in root but not shoot dry weight. A further increase in the exposure to 44 nmol mol?1/24 h (7.1 μmol mol?1‐h AOT40) also decreased the shoot dry weight. An increase in the O3 concentration to 75 (9.4–17.8 μmol mol?1‐h AOT40) and 116 nmol mol?1 (19.8 μmol mol?1‐h AOT40) further decreased shoot and root dry weights. A moderate O3 exposure (42 nmol mol?1/12 h = 2.5 μmol mol?1‐h AOT40) increased the plant height and leaf size, while a further increase in O3 concentration and exposure time decreased both of these variables. The birch provenances generally had a similar response to the O3 treatments. The accumulated O3 exposure over the 0, 10, 20, 30, 40 and 50 nmol mol?1 concentrations (AOT0, AOT10, AOT20, AOT30, AOT40 and AOT50, respectively) was calculated for all O3 treatments. The shoot and root dry weights were correlated best with AOT40 and AOT30, and were estimated to decrease by 10% at an AOT40 of 7.0 and 5.5 μmol mol?1‐h, respectively. The development of O3 injury (yellow stipples/chlorosis) was most marked when correlated with AOT40.  相似文献   

17.

Context

Avoidance or control of epicormic shoots is among the major silvicultural challenges for the production of high-quality oak timber. In northern Europe, contemporary oak silviculture aims to produce valuable timber on a relatively short rotation, applying early, heavy thinning combined with artificial pruning.

Aims

The aim of this study was to analyse the effects of pruning and stand density on the production of new epicormic shoots on young trees of pedunculate oak (Quercus robur L.).

Methods

The study was based on two field experiments in even-aged stands of pedunculate oak subjected to different thinning practices and early selection of potential future crop trees. From ages 13 to 15 years, stem density was reduced to 300 trees ha?1, 1,000 ha?1 or stands remained unthinned. Pruning was conducted on selected trees at ages 22–24 years. At that age, the stem density in unthinned control plots ranged from 2,500 to 3,100 ha?1. All treatments were replicated twice within each experiment.

Results

Pruning led to an overall increase in the total production of new epicormic shoots. More epicormic shoots were produced in the lower part of the stem (0–3 m in height) than in the upper part (3–6 m). The number of new epicormic shoots increased with increasing stand density.

Conclusion

Early, heavy thinning combined with high pruning at regular intervals may help shorten the rotation length for pedunculate oak without further reduction in wood quality than that which is caused by wider annual growth rings.  相似文献   

18.
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19.
The study was conducted in the Solan Forest Division with an area of 57,158 ha in Himachal Pradesh to study spatial distribution of plant biodiversity. The forest division has an altitudinal gradient from 600–2,260 m amsl. The contours on the Forest Survey of India (FSI) topo sheets (1:25000 scale) for this division were digitized to generate its Digital Elevation Model (DEM). It was stratified into five elevation classes (600–900, 900–1,200, 1,200–1,500, 1,500–1,800, 1800 m and above). A stock map of the division was digitized and superimposed on stratified DEM to know the distribution of vegetation at different elevations. Eight types of land use covers recorded in this division are: (a) chir pine (Pinus roxburghii) forests, (b) bamboo (Dendrocalamus strictus) forests, (c) khair (Acacia catechu) forests, (d) ban oak (Quercus leucotricophora) forests, (e) deodar (Cedrus deodara) forests, (f) broad leaved forests, (g) cultivation, and (h) culturable blank. Around 16.50% of the division's area was estimated to be under different land uses. Total biomass of vegetation in different land uses of the division is estimated as 63.80?×?104 tons. Total carbon stock of the division was 11.71?×?105 tons. Biomass density and carbon density were found to increase with elevation.  相似文献   

20.
Abstract

Tree response to climate trends is most likely to be observed in the forest–tundra ecotone, where mainly temperature limits tree growth. On-ground observation and multitemporal Landsat data were used in the analysis of forest–tundra ecotone dynamics (from 1976 to 2000) in the Western Sayan Mountains, Siberia. Observations showed an increase in forest stand crown closure, upward tree-line and regeneration shift and the transformation of Siberian pine and fir krummholz into arboreal forms. Closed stands were increasing in the area at a rate of 0.8% year?1 and advancing their upper boundary at an altitudinal rate of 0.6 m year?1; these changes were shown mainly by the transformation of sparse stands into closed stands. The altitudinal rate of regeneration propagation was estimated at 1.2 m year?1. It was also found that these changes correlated positively with temperature trends. The response of tree vegetation to air temperature increase was dependent on topographic relief features (azimuth and slope steepness).  相似文献   

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