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1.
Leaf litter decomposition and nutrient release patterns from five common multipurpose tree species—viz., Artocarpus heterophyllus, Mangifera indica, Areca catechu, Citrus sp., and Tamarindus indica, found in homegardens of Mizoram—were evaluated using a litter bag technique. The result of the study indicates a varying pattern of decomposition and nutrient release (N&P) among the species. Citrus sp. and T. indica were found to be the most labile species with comparatively much higher decay constant and faster nutrient release. Initial nitrogen concentration, lignin content, and lignin/N ratio of foliage litter showed significantly higher (p < .01) correlation with the decay coefficient and were found to be the important determinants in the decay process. The initial slow release and immobilization of N in A. heterophyllus and M. indica leaf litter reflect their potential as a source of nitrogen storage and effective mulching material. While litter from T. indica and Citrus sp. can provide the short-term nutrient need, foliage for the other three species may supply the long-term nutrient requirement for the understory crops in such agroforestry systems.  相似文献   

2.
Homegardens are one of the oldest forms of managed land use systems characterised by high diversity and complexity of their species structure which in turn contribute to efficient nutrient cycling. Litterfall and decomposition are the two major processes that replenish the soil nutrient pools and endow sustainability to these agroforests. A study was carried out in the village Dargakona, Barak Valley, northeast India to understand the pattern of litter production and litter decomposition in the traditional homegardens. Annual litter production was 6.27 Mg ha−1 with a bimodal distribution pattern and the nitrogen input through litterfall accounted for 48.17 kg ha−1 year−1. Litter decomposition studies for ten multipurpose trees revealed Sapium baccatum and Toona ciliata to be the most labile litter species and the decay rate coefficients varied among the species with differing rates of nutrient release pattern. Such studies can provide information regarding the litter quality of indigenous tree species and help validate farmers planting and management of multiple species which allows for efficient nutrient cycling of the system.  相似文献   

3.
Rates of weight loss and nutrient (N and P) release patterns were studied in the leaf litter of the dominant tree species (Ailanthus grandis, Altingia excelsa, Castanopsis indica, Duabanga sonneriatioides, Dysoxylum binectariferum, Mesua ferrea, Shorea assamica, Taluma hodgsonii, Terminalia myriocarpa and Vatica lancefolia) of a tropical wet evergreen forest of northeast India. Nitrogen and phosphorus mineralization rate and decay pattern varied significantly from species to species. In general, the decay pattern, characterized by using a composite polynomial regression equation, exhibited three distinct phases of decay during litter decomposition—an initial slow decay phase (0.063% weight loss day−1), followed by a rapid decay phase (0.494% weight loss day−1) and a final slow decay phase (0.136% weight loss day−1). The initial chemical composition of the litter affected decomposition rates and patterns. Species like D. sonneriatoides, D. binectariferum, and T. hodgsonii with higher N and P content, lower carbon and lignin content, and lower C:N ratio and lignin:N ratio exhibited relatively faster decomposition rates than the other species, for example M. ferrea, C. indica and A. grandis. A slow decay rate was recorded for species such as M. ferrea, C. indica, and A. grandis. The initial N and P content of litter showed significant positive correlations with decay rates. Carbon and lignin content, lignin:N, and C:N showed significant negative correlations with decay rates. Soil total N and P, and rainfall, soil temperature, and soil moisture had positive correlations with decay rates. The rapid decomposition rates observed in comparison with other different forest litter decay rates confirm that tropical wet evergreen forest species are characterized by faster decomposition rates, indicating a faster rate of organic matter turnover and rapid nutrient cycling.  相似文献   

4.
Household and homegarden characteristics in southwestern Bangladesh   总被引：1，自引：0，他引：1  
Homegardens around the world often exhibit remarkable variation in composition and structure depending on the physiographic and climatic conditions of the area and a wide variety of household characteristics. This research investigated whether households’ contextual attributes have a quantitative and predictable relationship with homegarden vegetation structure from a total of 402 randomly selected households in southwestern Bangladesh. The central analytical tool to test the relationship between household characteristics and the homegarden vegetation structure was multiple regression. The moderate to low regression R 2 values revealed that most household characteristics were not strong predictors of homegarden vegetation structure. Despite the weak explanatory power of the majority household characteristics, time spent and homestead size had the strongest relationship with species richness and income in a homegarden. Households being the main source of labor for a majority of households suggest that outside labor shortage would not influence homegarden vegetation structure. We suggest that women’s active participation in homegardening activities to reduce gender inequality in the family which will perhaps result in more diverse and economically viable homegarden. However, increasing population density and the concomitant fragmentation of landholdings to homesteads may create opportunity for homegarden promotion in Bangladesh. Our results of decreased species richness in the homegarden with improved roads and proximity to market support the general hypothesis of subsistence homegardens and did not reinforce the general fears of gradual decline in species richness due to a market economy. Household characteristics had no influence on the presence of IUCN Red Listed species in the homegarden, except for gender and education of the household head. However, most homegardeners were unaware about the status of red listed species, suggesting that occurrence of red listed species in homegardens was by chance. Thus, efforts to improve awareness and to save and conserve rare species from extirpation are needed.  相似文献   

5.
The Yucatán Peninsula of México has shallow soils and receives low amounts of precipitation, and has therefore low agricultural potential. Lacking large-scale irrigation from rivers and adequate rainfall, the indigenous Maya groups maintain agricultural productivity by adapting a variety of practices. Multistrata homegardens, one of their agricultural systems, have provided goods for trade, sale and personal consumption for many centuries. Nevertheless, an understanding of the controlling biological factors and interactions within these systems can lead to yield improvements. Photosynthetic rates, water use and litter production for a variety of species have been studied in these gardens to determine how Maya management impacts resource flow, productivity and diversity. When irrigated, diurnal photosynthetic rates nearly doubled for Manilkara zapota and water use increased two fold for M. zapota and Cordia dodecandra. Total litter production in traditional homegardens varied from 1,000 to 4,000 kg ha−1 yr−1 and ten arboreal species were found to contribute more than 33% of total litterfall biomass. Nutrient concentrations in the leaves of the predominant species were analyzed; Meliococcusbijugatus and Spondias purpurea were found to contribute the largest quantities of N, P and C. Our research indicates that species and structural diversity are critical to sustainability of homegardens, allowing efficient use and transfer of carbon, nutrients and water. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

6.
Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount （73.4%-87.6 %） of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence： N （11-129 kg.hm-2.aq） 〉 Ca （9-69） 〉 K （5-20） 〉 Mg （3-15） 〉 P （0.4-4.7） for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C：N ratios at the riparian zone might be due to the higher-quality litter inputs （largely N-fixing alder）.  相似文献   

7.
Annual amounts of litterfall and nitrogen input by litterfall were measured in a subtropical evergreen broad-leaved forest to examine the contribution of a liana species, Mucuna macrocarpa Wall., to the spatial heterogeneity of litterfall production and nitrogen input. The total litterfall in the study plot was 7.1 t ha−1 year−1. The amount of litterfall varied with topography and was greatest at the valley bottom and decreased toward the ridges. Macuna macrocarpa litterfall was absent on the ridges although it accounted for the largest percentage, 32%, of total leaf litter production in the valley. Nitrogen input by litterfall was 69 kg ha−1 year−1 in the plot. Nitrogen input by litterfall was also largest at the valley bottom and decreased toward the ridges. Leaf litter of M. macrocarpa had approximately twice the nitrogen concentration of litterfall of other species. Macuna macrocarpa accounted for 42% of nitrogen input by leaf litter in the valley. The abundance and the high nitrogen concentration of M. macrocarpa intensified differences in the amount of litterfall and nitrogen input by litterfall between valleys and ridges. It was concluded that a liana species, M. macrocarpa, can contribute to the spatial heterogeneity of litterfall and may subsequently affect nutrient cycling in a subtropical evergreen broad-leaved forest on Okinawa Island.  相似文献   

8.
Patterns of litterfall and nutrient input in a subtropical evergreen broad-leaved forest in northern Okinawa, Japan, were studied during May, 1996–April, 1999. The mean annual rate of litterfall in the five sampling plots ranged from 6.84 to 8.93 Mg ha−1 yr−1, of which 63.3–68.5% were leaves; 22.4–29.1% woody parts (including branches < 5.0 cm in diameter and bark); 2.8–5.0% sexual organs and 4.6–6.3% miscellaneous material. Significant differences were found among plots and among years. Significantly monthly differences pronounced seasonal patterns in litterfall were observed. Total litterfall and leaf litter showed negative correlations with relative basal area of the dominant species,Castanopsis sieboldii; and showed positive correlations with mean height of the stands. The dominant species,C. sieboldii produced an average of 2.36 Mg ha−1 yr−1 of leaf litter, which covered 30.5% of the annual litter production, and the nutrient input from those litterfall contributed 32.3, 28.3, 30.2, 22.2, 32.5, and 30.5% of total N, P, K, Ca, Mg, and Na, respectively. Nutrient use efficiency in litter production was high, especially for P and K compared with other broad-leaved forests in Japan indicating that P and K may be limiting in Okinawan evergreen broad-leaved forest.  相似文献   

9.
Interest in planted fallow systems has focused on soil fertility improvement, neglecting other potential benefits of such systems. It is important to quantify other processes responsible for crop yield increases under planted fallows, such as weed control. The suppressive potential on weeds of Flemingia macrophylla [(Willd.) Merrill] and Pueraria phaseoloides (Roxb.) Benth, planted fallows was evaluated in field trials in three villages in southern Cameroon. In each village, experiments were set up in 4–5 year-old bush fallow dominated by Chromolaena odorata (L.) R. M. King & H. Rob. and 20 year-old secondary forest. Total aboveground biomass production of P. phaseoloides was 7.45 Mg ha−1, 4.2 times higher than F. macrophylla (1.78 Mg ha−1 ; P < 0.05). The high biomass of P. phaseoloides resulted in a significantly greater reduction in total weed biomass compared to Flemingia macrophylla in both wet and dry seasons. In the wet season (11 and 18 MAP), there were significant fallow system × land use and fallow system × village interactions for total weeds and broadleaf weeds. P. phaseoloides in bush (0.55 Mg ha−1), and P. phaseoloides at Ngoumou (0.09 Mg ha−1) had the lowest total weeds in the wet seasons. After the dry season, the lowest total weed mass was consistently recorded in P. phaseoloides while the highest was in the natural regrowth. The population of grasses was always higher in the F. macrophylla system than in P. phaseoloides system throughout the wet and dry seasons. Grass biomass in the P. phaseoloides-forest LUS was the least (0.01 Mg ha−1), 58 times lower than in F. macrophylla-bush (0.58 Mg ha−1). Biomass production of P. phaseoloides was highly significantly correlated with total weed biomass (r = −0.64; P = 0.004) while no relationship was found between biomass production of F. macrophylla and total weed biomass (r = −0.08, P = 0.747). It was concluded that P. phaseoloides was a suitable leguminous species for weed control. But for F. macrophylla, its low biomass production coupled with a compact plant architecture compromised it as an appropriate species for weed control in a planted fallow system.  相似文献   

10.
Litterfall and decomposition are the two main processes accounting for soil enrichment in agroforestry. The extent of enrichment in soil properties depends on the tree species, management practices and the quantity and quality of litter. A field investigation was carried out to study litterfall production, decay rates, release of nutrients and consequent changes in soil physicochemical properties under crowns of four multipurpose tree species (MPTs) in irrigated conditions in farm fields. The species were Prosopis cineraria (L.), Dalbergia sissoo (Roxb.) ex DC, Acacia nilotica (L.) Del. and Acacia leucophloea (Roxb.) Willd. Annual accretion of litter ranged from 36 to 54 kg tree−1 year−1 and was highest under D. sissoo and lowest under A. nilotica. Total litterfall production was in the order: P. cineraria > A. leucophloea > A. nilotica > D. sissoo. P. cineraria showed the highest NPK concentration in litter. For all MPTs, a large pulse of litterfall coincided with the winter season (November to February). Litter of P. cineraria decomposed fastest while that of A. nilotica was slowest. More than 95% of the leaf litter of P. cineraria decomposed in 6 months, of D. sissoo in 7 months and A. leucophloea and A. nilotica in 9 months. Decomposition rate of litter was highly correlated with neutral detergent fibre (NDF) (r = −0.94) and P (r = −0.91) concentration. N, P and K release were best correlated with NDF, acid detergent fibre (ADF), P, lignin, lignin/N and C/P ratios and NDF alone explained 88% to 94% of the variability in litter decomposition and nutrient release rates. There was significant build up of soil organic carbon and available NPK in the agrisilvicultural systems but also a decrease in soil pH. Build up in soil fertility was significantly correlated with litterfall and soil improvement was greatest under P. cineraria.  相似文献   

11.
This study determined existing quantitative stand structure and its implication on silvicultural management of homestead forestry. The results showed that fruit and timber species have importance values of 57% and 43%, respectively, in the study area, which is in contrast to the commonly held view of absolute domination of fruit species. The fruit species were only moderately dominant over timber species in relation to the quantitative stand structure of homestead forests. Two fruit species, Mangifera indica and Artocarpus heterophyllus, contribute about one third of the stand structure, while amongst the timber species Samanea saman and Albizia spp. are the most important species. A simulated evaluation of soil expectation value of homestead forest showed that the existing stand structure would not maximize the financial gain perpetually, in contrast, the quantitative stand structure could be effectively regulated to maximize grower benefit without compromising the existing biodiversity. Optimization of the quantitative stand structure of homestead forests could be achieved by changing the species composition, specifically by increasing the percentage of commercially valuable species like Michelia champaca, Tectona grandis, Artocarpus chapalasha, Gmelina arborea, Litchi chinensis, Citrus grandis, Psidium guajava, Lagerstroemia speciosa, Swietenia mahogany, etc., reducing the percentage of species like Mangifera indica, Artocarpus heterophyllus, Cocos nucifera, Samanea saman, Spondias pinnata, Phoenix sylvestris, etc., and eradicating species like Lannea coromandelica and Ficus benghalensis. It was estimated that the optimal relative density of fruit and timber species that would generate optimal financial benefit would be 40.4% and 59.6%, respectively.  相似文献   

12.
Although the homegarden systems in the tropics are claimed to sustain basic community needs without environmental deterioration, the ecological rationalities behind the harmony between the humans, homegardens, and the environment are not well understood. Four study sites (Sukhothai, Srisatchanalai, Ayudhaya, and Nonthaburi) representing the four Thai eras in the Chao Phraya Basin were selected for studying these rationalities. The size and physical stature of the homegardens, their plant association and community features, physical environmental factors, nutrient and soil fertility parameters, and cultivation practices were studied. The major factor that determines species selection in homegardens is the utilization of the products, while the various practices within the homegardens are determined by such factors as the species, the system, and the environment. All homegardens had four vertical stratifications, with physical structures almost similar to that of dry dipterocarp forest, but with lower height for each layer, lower diversity of plants, and sparser crown layer. The analysis also shows a high possible utilization efficiency for space, light, water and nutrients in the soil in the homegardens. Shannon-Wiener's indices of species diversity of the homegardens were close to those of dipterocarp forest. The homegardens are in-situ reservoirs for biodiversity at genetic-, species-, and ecological levels. There was no complete harvesting from these homegardens. This practice ensured minimal nutrient export from the systems, while high amounts and diversity of litter biomass should contribute to high efficiency of nutrient cycling. Futhermore, phosphorus availability could be better in homegardens. The homegardens had more favorable microenvironment with lower soil and atmospheric temperature and higher relative humidity than outside. There has been no single incident of a pest outbreak at a threatening level. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

13.
In a lowland tropical rain forest in Sarawak, leaf-litter decomposition and the initial litter chemistry of 15 tree species were studied. During 13 months of field experiment, weight loss of litter samples was between 44% and 91%, and calculated decomposition rate constants (k) ranged from 0.38 to 2.36 year−1. The initial litter chemistry also varied widely (coefficients of variation: 19%–74%) and showed low N and P concentrations and high acid-insoluble residue (AIS) concentration. For nutrient-related litter chemistry, correlations with the decomposition rate were significant only for P concentration, C/P ratio, and AIS/P ratio (r s = 0.59, −0.62, and −0.68, n = 15, P < 0.05, respectively). For organic constituents, correlations were significant for concentrations of AIS and total carbohydrates, and AIS/acid-soluble carbohydrate ratio (r s = −0.81, 0.51, and −0.76, n = 15, P < 0.05, respectively). These results suggested that the relatively slow mean rate of decomposition (k = 1.10) was presumably due to the low litter quality (low P concentration and high AIS concentration), and that P might influence the decomposition rate; but organic constituents, especially the concentration of AIS, were more important components of initial litter chemistry than nutrient concentrations.  相似文献   

14.
The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry, a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon (C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha−1; 15 years: 17.6 Mg C ha−1; 25 years: 18.2 Mg C ha−1) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha−1 but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration rates were 3 Mg C ha−1 y−1, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system.  相似文献   

15.
To evaluate the effects of pruning on stem radial growth increment and leaf and twig biomass production, an experiment with four pruning intensities (0, 50, 75 and 90%) on ten locally important tree species (Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bombax malabarica, Bridelia crenulata, Erythrina indica, Grewia tiliifolia, Macaranga peltata, Terminalia paniculata and Xylia xylocarpa ), was carried out. The results did not support the contention that a certain level of pruning promotes stem growth in trees. Instead, all species have a level of pruning that reduces annual increment in stem diameter. In Ailanthus triphysa and Artocarpus hirsutus trees subjected to different pruning intensities showed a decline in the annual increment in stem diameter while in other species diameter increment reduced when the pruning intensity was 75% and 90%. Response to pruning in terms of biomass production also varied from species to species. In Erythrina indica, Macaranga peltata and Terminalia paniculata annual foliage and branch production in pruned trees was significantly more than that of the un-pruned trees. However, in Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa pruned trees produced comparatively more amount of foliage and branches produced annually than that by the un-pruned trees when the pruning was carried out once in 2 years. Based on these observations it is recommended that trees of Erythrina indica, Macaranga peltata and Terminalia paniculata may be pruned at 50% level annually while the trees of Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa may be pruned at the same pruning intensity once in 2 years.  相似文献   

16.
Homegardens in Kerala have long been important multi-purpose agroforestry systems that combine ecological and socioeconomical sustainability. However, traditional homegardens are subject to different conversion processes linked to socioeconomic changes. These dynamics were studied in a survey of 30 homegardens. On the basis of a cluster analysis of tree/shrub species density and subsequent further grouping using homegarden size as additional characteristic, six homegarden types were differentiated. These were assessed regarding structural, functional, management and dynamics characteristics. Four development stages of homegardens were found along a gradient from traditional to modern homegardens. Fifty percent of the homegardens still displayed traditional features, whereas 33% incorporated modern practices. The process of modernisation includes a decrease of the tree/shrub diversity, a gradual concentration on a limited number of cash-crop species, an increase of ornamental plants, a gradual homogenization of homegarden structure and an increased use of external inputs. One homegarden was characterised as an adapted traditional homegarden combining multispecies composition and intensive management practices using internal inputs with commercial production. In comparison to modern homegardens, this homegarden type offers an example of an alternative development path in adapting homegardens to changing socioeconomic conditions. The study of structural and functional dynamics of homegardens offers the opportunity to understand the trends in socio-economic sustainability and how these relate to ecological sustainability.  相似文献   

17.
The soil of a west Javanese homegarden was a clay-loam, humic Cambisol of medium fertility, with neutral to weak acid reaction. The 0.13 ha large garden contained about 60 plants species (excluding weeds), of which 39 supplied useful products and the remaining were ornamentals. Tree coverage was 81% and total ground cover, including ground litter and weeds was 99%. The vegetation was multi-layered. Total biomass was estimated to 126 t ha–1, including 4.4 t ha–1 of ground litter. Of the total biomass, 95% belonged to the tree compartment;Cocos nucifera, Eugenia aromatica andLansium domesticum alone constituted 75%.The homegarden resembled young secondary forest both in structure and biomass, and may be considered as a man made forest kept in a permanent early successional state. The nutrient pool stored in the vegetation was generally low compared to the soil reserves. Only the pool sizes of N and K constituted a significant percentage (5.5 and 11.7%, respectively) of soil reserves.It is concluded that the sustainability of the homegarden is connected to the medium fertile soil with large nutrient reserves, the large plant biomass directly and indirectly protecting the soil against erosion and drying, and a high species diversity providing a large variation in crop phenology and stability in nutritional supply. All this is in contrast to what has been experienced in most attempts of practising monoculture on sloping lands on Java.  相似文献   

18.
Nutrient release from plant residues can be manipulated as per crop demand through several approaches. A pot study was conducted to study the influence of incorporation of leaf litter of poplar (Populus deltoides), eucalypt (Eucalyptus hybrid) and dek (Melia azedarach) inoculated with cellulolytic fungus culture (Aspergillus awamori) on the nutrition and biomass of wheat (Triticum aestivum, cv. PBW 343) in loamy sand and sandy loam soils. The residual effect of leaf litter after wheat harvest was studied on sorghum (Sorghum bicolor, cv. Punjab Sudax Chari 1). The treatments consisted of a control (no leaf litter) and three uninoculated as well as inoculated leaf litter levels of tree species–0.15%, 0.30% and 0.45% (w/w, dry weight basis). A uniform dose of N, P and K @ 50, 11 and 10 mg kg−1 soil, respectively from inorganic fertilizers was applied to all the treated pots. Straw and grain yield, and nutrient content of wheat increased with increasing level of uninoculated or inoculated leaf litter in both the soils. The inoculated leaf litter augmented the yield and nutrient content of crop significantly (P < 0.05) as compared to the corresponding uninoculated treatments. Poplar and dek leaf litter produced higher wheat yield, plant nutrient content and available nutrients in soil after wheat harvest than eucalypt leaf litter. Dry matter yield of sorghum raised on residual fertility increased significantly with increasing levels of leaf litter application. The comparative responses in yield and nutrient content of crops were higher in loamy sand than in the sandy loam soil. The study shows the beneficial influence of use of cellulolytic microorganisms on enhancement in decomposition and nutrient release from litterfall of tree species.  相似文献   

19.
Litter decomposition in a subtropical plantation in Qianyanzhou,China   总被引：1，自引：0，他引：1  
A long-term (20 months) bulk litter decomposition experiment was conducted in a subtropical plantation in southern China in order to test the hypothesis that stable isotope discrimination occurs during litter decomposition and that litter decomposition increases concentrations of nutrients and organic matter in soil. This was achieved by a litter bag technique. Carbon (C), nitrogen (N) and phosphorus (P) concentrations in the remaining litter as well as δ13C and δ15N during the experimental period were measured. Meanwhile, organic C, alkali-soluble N and available P concentrations were determined in the soils beneath litter bags and in the soils at the control plots. The dry mass remaining (as % of the initial mass) during litter decomposition exponentially declined (y = 0.9362 e−0.0365x , R 2 = 0.93, P < 0.0001), but total C in the remaining litter did not decrease significantly with decomposition process during a 20-month period. By comparison, total N in the remaining litter significantly increased from 5.8 ± 1.7 g kg−1 dw litter in the first month to 10.1 ± 1.4 g kg−1 dw litter in the 20th month. During the decomposition, δ13C values of the remaining litter showed an insignificant enrichment, while δ15N signatures exhibited a different pattern. It significantly depleted 15N (y = −0.66x + 0.82, R 2 = 0.57, P < 0.0001) during the initial 7 months while showing 15N enrichments in the remaining 13 months (y = 0.10x − 4.23, R 2 = 0.32, P < 0.0001). Statistically, litter decomposition has little impact on concentrations of soil organic C and alkali-soluble N and available P in the top soil. This indicates that nutrient return to the topsoil through litter decomposition is limited and that C cycling decoupled from N cycling during decomposition in this subtropical plantation in southern China.  相似文献   

20.
A key assumption in many homegarden studies is that homegardens are ecologically and socio-economically sustainable due to their species diversity. The precise relation between diversity and sustainability is still heavily debated, however. A basic question is how diversity in homegardens can best be characterized in view of the various dimensions of species diversity and their variation in time and space. This paper assesses different types of species diversity in the homegardens of Sidama region of southern Ethiopia. In a survey of crop species in 144 homegardens a total of 78 cultivated crop species (excluding trees) belonging to 10 functional groups were recorded; there were on average 16 crop species and 8 functional groups per farm. Within homegardens, plots differ in species composition and crop diversity. Four types of homegarden systems are distinguished differing in both type and area-share of dominant species, relative orientation at subsistence or cash production and overall crop diversity. The gradual replacement of enset by maize and of coffee by more financially attractive cash crops khat and pineapple causes a decrease in overall crop diversity. Our data demonstrate that it is incorrect to consider homegardens as generic systems with a uniform distribution of species diversity: important within and between homegarden variation exists. Ecological and socio-economic sustainability is not just related to species diversity per se, but rather to more specific features such as presence of keystone species and diversity in functional species groups. Socio-economic sustainability in terms of adjustment to socio-economic change implies dynamics in species diversity.  相似文献   

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