首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
Estimates of above-ground biomass are required for better planning, sustainable management and monitoring of changes in carbon stocks in agroforestry systems. The objective of this study was to develop and compare biomass equations for Markhamia lutea, Casuarina equisetifolia, Maesopsis eminii and Grevillea robusta grown in a linear simultaneous agroforestry system in Uganda. These species were established in single rows in the middle of fields in 1995 from four-month old seedlings. A total of 57 trees were sampled for this study, 13 for M. lutea, 12 for C. equisetifolia, 16 for M. eminii and 16 for G. robusta. Biomass values of the various tree components (stem, branches and foliage) as well as the total above-ground biomass were fitted to linear and non-linear allometric models using total height, diameter-at-breast height (DBH), crown width as predictor variables. Although both DBH and height are typically used as independent variables for predicting above-ground biomass, the addition of height in biomass equations did not significantly improve model performance for M. eminii, M. lutea and G. robusta. However, addition of height significantly increased the proportion of variation explained in above-ground biomass for C. equisetifolia, while DBH did not significantly improve the prediction of biomass. The study confirmed the need for developing species-specific biomass equations.  相似文献   

2.
Trials were established at three sites in Uganda to test the suitability of multipurpose trees (MPTs) as upperstorey in crop lands to provide poles, small timber and fuelwood. The three sites were Kachwekano District Farm Institute (1°16 S, 29°57 E, 2000 m.a.s.l.) in Kabale District, Kabanyolo University Farm (0°28 N, 32°27 E, 1250 m.a.s.l.) in Mpigi District and Bushenyi District Farm Institute (0°34 S, 30°13 E, 1610 m.a.s.l.) in Bushenyi District. The MPTs were planted in single rows at intra spacing of 2 m and each plot contained seven or nine trees. On both sides of the tree row, crops were raised. Data on crop yields were collected every season, while data on the growth of the trees were collected four times each year.In terms of tree growth,Grevillea robusta, Casuarina cunninghamiana andAlnus acuminata performed well with height growth of 1.8–2.4 m per year at Kachwekano, while at BushenyiGrevillea robusta, Casuarina junghuhniana, Cupressus lusitanica andCedrela serrulata averaged 1.6–2.0 m height per year. At Kabanyolo,Melia azedarach, Cassia siamea, Jacaranda mimosifolia, Grevillea robusta andMaesopsis eminii had height increments ranging from 1.8–2.7 m annually. Crop yields were affected by the presence of the MPTs, withMaesopsis eminii being the most competitive (averaging 60% reduction, over five seasons). The crop rows nearest to the tree line were the most affected. OnlyAlnus acuminata seems to have had a positive effect on crop yields. The installation of a root mesh to reduce tree root competition for nutrients and water in four species increased yields in plots with MPTs by 5% (Melia azedarach) to 152% (Maesopsis eminii), but the control plot still had significantly higher bean yields, suggesting that shading could also be important. In the case of maize, suppression seems to be due mainly to root competition because after its elimination yields obtained thereafter did not differ significantly from those of the control except for the Maesopsis plots. The negative influence of the MPTs could, therefore, be minimized by periodically pruning the tree crowns and roots.  相似文献   

3.
Greater organic matter inputs in agroforestry systems contribute to the long-term storage of carbon (C) in the soil, and the use of simulation models provides an opportunity to evaluate the dynamics of the long-term trends of soil organic carbon (SOC) stocks in these systems. The objective of this study was to apply the Century model to evaluate the long-term effect of agroforestry alley crop and sole crop land management practices on SOC stocks and soil C fractions. This study also evaluated the accuracy between measured field data obtained from a 19-year old tropical (TROP) and 13-year old temperate (TMPRT) alley crop and their respective sole cropping systems and simulated values of SOC. Results showed that upon initiation of the TROP and TMPRT alley cropping systems, levels of SOC increased steadily over a ~100 year period. However, the sole cropping systems in both tropical and temperate biomes showed a decline in SOC. The active and passive C fractions increased in the TROP agroforestry system, however, in the TMPRT agroforestry system the active and slow fractions increased. The input of organic matter in the TROP and TMPRT agroforestry systems were 83 and 34% greater, respectively, compared to the sole crops, which likely contributed to the increased SOC stock and the C fractions in the alley crops over the 100 year period. Century accurately evaluated levels of SOC in the TROP (r 2 = 0.94; RMSE = 226 g m−2) and TMPRT (r 2 = 0.94; RMSE = 261 g m−2) alley crops, and in the TROP (r 2 = 0.82; RMSE = 101 g m−2) and TMPRT (r 2 = 0.83; RMSE = 64 g m−2) sole crops. Century underestimated simulated values in the alley cropping systems compared to measured values due to the inability of the model to account for changes in soil bulk density with increasing organic matter inputs with tree age from prunings or litterfall.  相似文献   

4.
Agroforestry systems are potentially suitable for conservation of tree genetic resources. Farmers around Mt. Kenya usually integrate trees into their farm. Large parts of these trees seem to be of exotic origin, whereas indigenous species have priority for conservation. This study aimed at determining on-farm richness, composition and frequency of indigenous and exotic woody species around Mount Kenya to assess the suitability of farms for the conservation of indigenous tree species. 265 on-farm plots of 0.5 ha size each were selected in 18 different agro-ecological zones by using a stratified sampling scheme. All woody species within the plot were recorded with their local and scientific names. Total species richness was 424 (including 306 indigenous ones), mean richness per plot 16.5 species (including 8.8 indigenous ones). Eight out of the 10 most frequent species were exotic ones with Grevillea robusta from Australia ranking first (found on almost 76% of the surveyed farms). The proportion of indigenous species increased with increasing aridity and temperature. Dominance of exotic species was found at farms of humid mid- and highlands. Ordination analysis revealed that mostly exotic species contributed to separation of farms in the highlands and upper midlands, whereas indigenous species in the lower midlands and lowlands. As the frequencies of most indigenous trees were low, only parts of the surveyed farms can contribute to conservation of tree genetic resources, particularly the less intensively managed farms of the more arid lands. Farmers’ access to knowledge on valuable indigenous tree species and to quality seedlings of these trees need to be improved to increase indigenous species’ frequencies on farms and possibly to replace some of the exotic species in the future.  相似文献   

5.
Growth rates of 29 multipurpose trees grown in an agroforestry arboretum for six years at a sub-humid to semi-arid climatic zone are presented. Exotic species such as Grevillea robusta, Sesbania grandiflora, Leucaena leucocephala, Cassia siamea and Sesbania sesban, some of which were outside their traditional climatic zones, had higher diameters, heights and bole volumes/tree (upto 130% more in certain cases) than of the indigenous species. However, poor performance of several species (both exotic and indigenous) would limit their agroforestry potentials at the evaluation site or other similar areas.  相似文献   

6.
On-farm indigenous (Cordia africana) and exotic (Grevillea robusta) tree species were compared in terms of the quality of their utility and their agronomic traits in the Meru Central district of Kenya. These two species are the most common indigenous and exotic trees, respectively, among the recorded 117 trees on farms. Interviews with farmers and collected documents on tree felling and planting showed that farmers considered C. africana to be more useful than G. robusta. However, farmers wanted to plant more G. robusta than C. africana because the easily established and fast growing G. robusta has a higher short-term contribution to the household economy. The advantages of C. africana, however, should be redefined in terms of its long-term contribution to farmers; C. africana contributes to farming more effectively than does G. robusta. The lower growth performance and relative difficulty in the establishment of C. africana can be compensated for by its higher timber quality and coppicing ability.  相似文献   

7.
To assess possible new agroforestry scenarios the tree–soil–crop interaction model in agroforestry systems (WaNuLCAS 3.01) was used based on-site specific data collected from Tabango (Central Philippines). Three native timber trees (Shorea contorta Vid., Pterocarpus indicus Juss., and Vitex parviflora Willd.) and one widely spread exotic specie (Swietenia macrophylla King.) were simulated under different intercrop scenarios with maize (Zea mays L.) and subsequently compared. Model simulation results quantified and explained trade-off between tree and crop. For example, higher tree densities will lead to a loss of crop yield that is approximately proportional to the gain in wood volume. However, beside this trade-off effect, there is considerable scope for tree intercropping advantage under a fertilization scenario, with systems that yield about 50% of the maximum tree biomass still allowing 70% of monoculture maize yield. Maximum tree yield can still be obtained at about 20% of the potential crop yield but intermediate tree population densities (400 trees ha−1) and the resulting larger stem diameters may be preferable over the larger total tree biomass obtained at higher tree densities. Another advantage from intercropping systems is that trees directly benefit from the inputs (i.e., fertilizer) that are applied to the crops. The three native trees species studied have different performance in relation to productivity but are similar to (or even better than) S. macrophylla.  相似文献   

8.
Soil properties under an exotic plantation (Pinus caribaea) and an indigenous plantation (Podocarpus imbricatus) were compared with adjacent secondary forests and abandoned land in the tropical forest areas of Jianfengling National Nature Reserve in Hainan province, southern China. The surface soil (0–0.2 m) under Pi. caribaea has higher bulk density, lower soil organic carbon, total N, total K, available N, microbial biomass carbon, and smaller soil microbial communities (as indicated by soil Biolog profiles) than under Po. imbricatus. Both land use types showed negative cumulative soil deterioration index (DI) compared to secondary forests. However, compared to abandoned land (DI = –262), the soil quality of Po. imbricatus showed improvement (DI = –194) while that of Pi. caribaea showed deterioration (DI = –358). These results demonstrated that these exotic pine plantations can significantly and negatively influence soil properties. By contrast, our results showed that adoption of indigenous species in plantations, or natural regeneration, can improve soil quality.  相似文献   

9.
In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (−P) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1–11 m2 per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LAn, n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.  相似文献   

10.
This study examined the long-term growth performance of Cordia africana and Grevillea robusta, which are the most common indigenous and exotic trees, respectively, associated with crops in the Mount Kenya region. Local farmers prefer G. robusta to C. africana as on-farm trees because they believe that G. robusta grows faster. Measurements of height and diameter at breast height were made of 47 C. africana and 89 G. robusta trees for which the age was established based on interviews with farmers. The oldest G. robusta and C. africana trees were 55 and 46 years old, respectively. The apical growth rate for G. robusta was greater than that for C. africana in Katheri (a humid area). The differences between the two species were less remarkable in Ruiri (a dry-subhumid area). There was no notable difference in the radial growth performance of the two species in Katheri and Ruiri. These comparisons suggest that the long-term growth performance of C. africana is not necessarily inferior to that of G. robusta.  相似文献   

11.
The poplar based agroforestry system improves aggregation of soil through huge amounts of organic matter in the form of leaf biomass. The extent of improvement may be affected by the age of the poplar trees and the soil type. The surface and subsurface soil samples from agroforestry and adjoining non-agroforestry sites with different years of poplar plantation (1, 3 and 6 years) and varying soil textures (loamy sand and sandy clay) were analyzed for soil organic carbon, its sequestration and aggregate size distribution. The average soil organic carbon increased from 0.36 in sole crop to 0.66% in agroforestry soils. The increase was higher in loamy sand than sandy clay. The soil organic carbon increased with increase in tree age. The soils under agroforestry had 2.9–4.8 Mg ha−1 higher soil organic carbon than in sole crop. The poplar trees could sequester higher soil organic carbon in 0–30 cm profile during the first year of their plantation (6.07 Mg ha−1 year−1) than the subsequent years (1.95–2.63 Mg ha−1 year−1). The sandy clay could sequester higher carbon (2.85 Mg ha−1 year−1) than in loamy sand (2.32 Mg ha−1 year−1). The mean weight diameter (MWD) of soil aggregates increased by 3.2, 7.3 and 13.3 times in soils with 1, 3 and 6 years plantation, respectively from that in sole crop. The increase in MWD with agroforestry was higher in loamy sand than sandy clay soil. The water stable aggregates (WSA >0.25 mm) increased by 14.4, 32.6 and 56.9 times in soils with 1, 3 and 6 years plantation, respectively, from that in sole crop. The WSA >0.25 mm were 6.02 times higher in loamy sand and 2.2 times in sandy clay than in sole crop soils.  相似文献   

12.
Trees which root below crops may have a beneficial role in simultaneous agroforestry systems by intercepting and recycling nutrients which leach below the crop rooting zone. They may also compete less strongly for nutrients than trees which root mainly within the same zone as crops. To test these hypotheses we placed highly enriched 15N-labelled ammonium sulphate at three depths in the soil between mixed hedgerows of the shallow-rooting Gliricidia sepium and the deep rooting Peltophorum dasyrrhachis. A year after the isotope application most of the residual 15N in the soil remained close to the injection points due to the joint application with a carbon source which promoted 15N immobilization. Temporal 15N uptake patterns (two-weekly leaf sub-sampling) as well as total 15N recovery measurements suggested that Peltophorum obtained more N from the subsoil than Gliricidia. Despite this Gliricidia appeared to compete weakly with the crop for N as it recovered little 15N from any depth but obtained an estimated 44–58% of its N from atmospheric N2-fixation. Gliricidia took up an estimated 21 kg N ha–1 and Peltophorum an estimated 42 kg N ha–1 from beneath the main crop rooting zone. The results demonstrate that direct placement of 15N can be used to identify N sourcing by trees and crops in simultaneous agroforestry systems, although the heterogeneity of tree root distributions needs to be taken into account when designing experiments. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

13.
Uptake and management of agroforestry technologies differs among farms in Rwanda and needs to be documented as a basis for shaping future research and development programs. The objective of this study was to investigate current agroforestry practices, farmers’ preferences, tree management and perspectives for agroforestry technologies. The study consisted of a combination of a formal survey, a participatory tree testing, farmer evaluation and focus group discussions in the Central Plateau (moderate altitude) and the Buberuka (high altitude) agro-ecological zones. A survey and a tree testing exercise with a range of species: (timber species—Eucalyptus urophyla, Grevillea robusta; legume shrubs - Calliandra calothyrsus, Tephrosia vogelii; and fruit species—Persea americana and Citrus sinensis) were carried out in Simbi (Central Plateau) and Kageyo (Buberuka) with farmers from different wealth status who received tree seedlings for planting, managing, and evaluating. Simbi had more tree species farm?1 (4.5) than Kageyo (2.9). Fruit trees occurred most frequently in Simbi. Grevillea robusta, Calliandra calothyrsus and Tephrosia vogelii were mostly established along contours, fruit trees in homefields and Eucalyptus urophyla trees in woodlots. Survival was better on contours for Grevillea robusta (58–100 %) and Calliandra calothyrsus (50–72 %). Tree growth was strongly correlated with the total tree lop biomass in Eucalyptus urophyla (R 2 = 0.69). Grevillea robusta was most preferred in Simbi and Eucalyptus urophyla and Calliandra calothyrsus in Kageyo. The study provided information useful for revising the national agroforestry research and extension agenda and has important implications for other countries in the highlands of Africa.  相似文献   

14.
Tree root pruning is a potential tool for managing belowground competition when trees and crops are grown together in agroforestry systems. We investigated the effects of tree root pruning on shoot growth and root distribution of Alnus acuminata (H.B. & K.), Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br., Maesopsis eminii Engl. and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was reopened and roots recut at 50 and 62 months after planting. We assessed the effects on tree growth and root distribution over a 3 year period, and crop yield after the third root pruning at 62 months. Overall, root pruning had only a slight effect on aboveground tree growth: height growth was unaffected and diameter growth was reduced by only 4%. A substantial amount of root regrowth was observed by 11 months after pruning. Tree species varied in the number and distribution of roots, and C. equisetifolia and M. lutea had considerably more roots per unit of trunk volume than the other species, especially in the surface soil layers. Casuarina equisetifolia and M. eminii were the tree species most competitive with crops and G. robusta and M. lutea the least competitive. Crop yield data provided strong evidence of the redistribution of root activity following root pruning, with competition increasing on the unpruned side of tree rows. Thus, one-sided root pruning will be useful in only a few circumstances.  相似文献   

15.
Soil hydro-physical behaviour was studied under a 20-year old agroforestry plantation consisting of five multipurpose tree species (Pinus kesiya Royle ex-Gordon, Alnus nepalensis D.Don, Parkia roxburghii G.Don, Michelia oblonga Wall. and Gmelina arboria Roxb.) maintained under normal recommended practices at Indian Council of Agricultural Research (ICAR) Complex, Umiam, Meghalaya, India. The aim was to select tree species, which could act as better bio-ameliorant as well as provides higher economic return in highly degraded soil of northeastern hill region of India. A site without vegetation (no tree) nearby the plantation was also selected as control for comparison. Soil samples for various hydro-physical analysis, were taken from 0–15 and 15–30 cm soil depth at a distance of 1 m from respective tree species during wet and dry season of 2003–2004. No appreciable differences in relative contents of textural separates of sand, silt and clay were observed among various tree covers. Surface cover with constant leaf litter fall and extensive root system increased soil organic carbon, helped in better soil aggregation, improved water transmissivity and infiltrability and in turn, reduced soil erosion in the present study. However, due to variation in quantity of leaf litter fall and root biomass, these parameters differed among tree species. Of the tree species, P. kesiya, M. oblonga and A. nepalensis were found to be rated best for bio-amelioration of soils as these tree covers had more root and shoot biomass and more litter fall compared to other species. However, considering both timber production and improvement in hydro-physical behaviour, M. oblonga was found best among the tested tree species. The study, thus, suggested that inclusion of tree species M. oblonga in agroforestry system is a viable option for natural resource management and could sustain long-term soil productivity in a highly degraded soil of this region as well as for food security of the resource poor people of North East India.  相似文献   

16.
In many tropical soils, excessive weathering of primary minerals confounded by intense agricultural production has resulted in the depletion of organic matter and plant available forms of phosphorus (P). Long-term growth of cover crops in tropical agroforestry systems have been shown to influence nutrient cycling, and soil organic matter pools. The objective of this experiment was to assess the affect of 2 years of cover-crop cultivation on organic matter accumulation and P bioavailability using Mehlich I and sequential fractionation methods. The experiment included six treatments in the understory of a cacao-plantain agroforestry system adjacent to lower montane tropical forests of the San Martin district of Eastern Peru. Cacao and plantain formed the primary canopy on otherwise abandoned agricultural land. The treatments consisted of four perennial leguminous cover crops (Arachis pintoi, Calopogonium mucunoides, Canavalia ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), and a control treatment (no cover crop). After only 2 years of cultivation, results suggest that all cover crop species accessed residual P pools in 0–5 cm soil depths as indicated by a decrease in the 0.5 M HCl extractable P pools when compared to control. Additional use of residual P pools by A. pintoi and C. macrocarpum were indicated by significant reduction in the 6.0 M HCl extractable P pool. Relative to control, there was no treatment effect on soil organic matter content; however significant differences occurred between treatments. The C. ensiformis, C. mucunoides and C. repens treatments in 5–15 cm soil depths contained significantly more organic matter than the A. pintoi treatment. In 15–30 cm soil depths the C. ensiformis treatment contains significantly more organic matter than the A. pintoi treatment. Continued research should focus on monitoring the long-term effects of cover crop cultivation on the bioavailability of soil P pools in surface soil horizons, development of organic matter pools and the productivity of the agroforestry species.  相似文献   

17.
The response of corn (Zea mays) to incorporated leaf and twig mulches ofLeucaena leucophala, Gliricidia sepium andCassia siamea, andGrevillea robusta as a non-legume comparison was investigated in a 10-week pot trial and a concurrent soil incubation study to evaluate the suitability of various agroforestry trees as mulch sources.Leucaena contributed to the highest N uptake and biomass production of these corn plants, reflecting the benefits of organic mulching.Cassia-treated plants also performed better than the unmulched controls, butGrevillea incorporation suppressed corn growth probably because of the relatively high Mn status of this mulch. Manganese toxicity was confirmed by comparative vector diagnosis of plant nutrient status.Cliricidia mulching resulted in seedling mortality after germination possibly from high soil pH and ammonium toxicity. Mineral N production in mulched soils during the laboratory incubation was well correlated with N uptake in corn shoots. The results suggest that the nutritional effects of agroforestry tree mulches on growth of companion crops may be effectively screened by a combined soil test, pot trial, and plant analysis approach.  相似文献   

18.
Agroforestry systems based on poplar (Populus deltoides) are becoming popular in eastern and northern parts of India. Therefore studies on the structure and function of the systems are important. The investigations included allometric equations for above- and belowground tree components, crop and plantation floor biomass and litter fall estimation at Pusa, Bihar, India. Biomass, floor litter mass, litter fall and net primary productivity (NPP) of plantations increased with an increase in age of trees whereas, crop biomass for any specific crop interplanted with poplar decreased with the age of the plantation. The total plantation biomass increased from 12.08 to 90.59 Mg ha−1 and NPP varied from 5.69 to 27.9 Mg ha−1 year−1. The biomass accumulation ratio ranged from 2.1 to 3.2. Total annual litter fall was in between 1.95 and 10.00 Mg ha−1 year−1, of which 92–94% was contributed by leaf litter. Compartmental models were developed for dry matter distribution in agroforestry systems involving young (3-year-old) and mature (9-year-old) poplar trees interplanted with various crops, the crops being grown in two rotations maize (Zea mays) – wheat (Triticum aestivum) – turmeric (Curcuma domestica) and pigeonpea (Cajanus cajan) – turmeric. This study substantiates the potential of Populus deltoides G3 under agroforestry combinations.  相似文献   

19.
Indices of shallow rootedness and fractal methods of root system study were combined with sapflow monitoring to determine whether these ‘short-cut’ methods could be used to predict tree competition with crops and complementarity of below ground resource use in an agroforestry trial in semi-arid Kenya. These methods were applied to Grevillea robusta Cunn., Gliricidia sepium (Jacq.) Walp., Melia volkensii Gürke and Senna spectabilis syn. Cassia spectabilis aged two and four years which were grown in simultaneous linear agroforestry plots with maize as the crop species. Indices of competition (shallow rootedness) differed substantially according to tree age and did not accurately predict tree:crop competition in plots containing trees aged four years. Predicted competition by trees on crops was improved by multiplying the sum of proximal diameters squared for shallow roots by diameter at breast height2, thus taking tree size into account. Fractal methods for the quantification of total length of tree root systems worked well with the permanent structural root system of trees but seriously underestimated the length of fine roots (less than 2 mm diameter). Sap flow measurements of individual roots showed that as expected, deep tap roots provided most of the water used by the trees during the dry season. Following rainfall, substantial water uptake by shallow lateral roots occurred more or less immediately, suggesting that existing roots were functioning in the recently wetted soil and that there was no need for new fine roots to be produced to enable water uptake following rainfall. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

20.
Multipurpose tree species （MPTs） were studied in an agroforestry arboretum under subtropical humid climate in Northeast India. Out of 12 MPTs planted under agroforestry systems, Acacia auriculiformis in spacing of 2 m × 2 m （2500 stems·hm^-2） could have the potentiality to meet the timber/fuelwood requirement due to its high wood production of 635 m^3·hm^-2 with mean annual increment （MAI） of 2.54×10^-2 m^3.treel.a^-1 in a short rotation period of 10 years. Thus, A. auriculiformis is a short rotation forest tree species suitable to grow in subtropical humid climate. On the other hand, at 16 years of age, Eucalyptus hybrid and Michelia champaca in spacing of 3 m × 3 m （1111 stems.hm^2） produced appreciably high timber volume of 315 m^3.hm^-2 and 165 m^3.hm^-2 with MAI of 1.77×10^-2 m^3.tree^-1·a^-1 and 0.92×10.2 m^3.tree^-1.a^-1, respectively. At 16 years of age, Gmelina arborea produced a timber volume of 147 m^3.hm^-2 with MAI of 1.47×10^-2 m^3.tree^-1.a^-1 followed by Samania saman （140 m^3.hm^-2）, Albizziaprocera （113 m^3·hm^-2） and Tectona grandis （79 m3.hm^-2） with MAI of 1.40, 1.13 and 0.78 × 10^-2 m^3 .tree^-1a^-1, respectively in 4 m × 4 m spacing （625 stems.hm^-2）. Gliricidia maculata and Leucaena leucocephala could be used as live fences around the farm boundary to supply their N-rich leaves for mulch as well as manure to crops. In agroforestry arboretum, direct seeded upland rice （Oryza sativa - variety, AR-11）, groundnut （Arachis hypogaea - variety, JL-24） and sesamum （Sesamum indicum - variety, B-67） were grown during the initial period upto 8 years of tree establishment. Under other MPTs, there was a reduction in crop productivity as compared to open space. After 8 years of tree establishment, horti-silvi and silvi-pastoral systems were developed and pineapple （Ananas comosus - variety Queen）, turmeric （Curcuma longa -variety RCT -1） and cowpea （Vigna sinensis - variety Pusa Barsati） as forage crop were raised. The productivity of p  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号