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1.
Coffee, Coffea arabica L., which is native to Ethiopia, is the world’s most widely traded tropical agricultural commodity. While much is known about the productivity and management of coffee for coffee beans little attention has been given to the plants overall biomass production and carbon sequestration. The objective of this study was to develop and evaluate allometric equations for estimating the aboveground biomass of C. arabica plants growing in indigenous agroforestry system in the Rift Valley escarpment of south-eastern Ethiopia. Coffee plays an important role in providing income and in sustaining these productive systems. Biomass harvesting of 31 plants with 54 stems was carried out in a 40 km2 area varying in elevation from 1,500 to 1,900 m. The stem accounted for most (56 %) of plant biomass, followed by branches (39 %) and twigs plus foliage (5 %). Plant mean biomass was 22.9 ± 15.8 kg. Power equations using stem diameter measured at either 40 cm (d 40) or at breast height (d, 1.3 m) with and without stem height (h) were evaluated. The square power equation, $ Y \; = \; b_{ 1} d_{ 40}^{ 2} $ , was found to be the best (highest ranked using goodness-of-fit statistics) for predicting total and component biomass. The reliability of the prediction decreased in the order: stem > branches > twigs plus foliage. A cross-validation procedure showed that equation parameterization was stable and coefficients reliable. Our parameterized square power equation for total aboveground biomass was also found to be better than the equations parameterized by Hairiah et al. (Carbon stocks of tropical land use systems as part of the global C balance: effects of forest conversion and options for clean development activities, International Centre for Research in Agroforestry, Bogor, 2001) and Segura et al. (Agroforest Syst 68:143–150, 2006) for C. arabica grown in agroforestry systems, confirming the importance of parameterization of allometric equations with site specific data when possible.  相似文献   

2.
A number of agroforestry models have been developed to simulate growth outcomes based on the interactions between components of agroforestry systems. A major component of this interaction is the impact of shade from trees on crop growth and yield. Capability in the agricultural production systems simulator (APSIM) model to simulate the impacts of shading on crop performance could be particularly useful, as the model is already widely used to simulate agricultural crop production. To quantify and simulate the impacts of shading on maize performance without trees, a field experiment was conducted at Melkassa Agricultural Research Centre, Ethiopia. The treatments contained three levels of shading intensity that reduced incident radiation by 0 (control), 50 and 75% using shade cloth. Data from a similar field experiment at Machakos Research Station, Kenya, with 0, 25 and 50% shading were also used for simulation. APSIM adequately simulated maize grain yield (r2 = 0.97) and total above-ground biomass (r2 = 0.95) in the control and in the 50% treatments at Melkassa, and likewise in the control (r2 = 0.99), 25% (r2 = 0.90) and 50% (r2 = 0.98) treatments at Machakos. Similarly, APSIM effectively predicted Leaf Area Index attained at the flowering (r2 = 0.90) and maturity (r2 = 0.94) stages. However, APSIM under-estimated maize biomass and yield at 75% shading. In conclusion, the model can be reliably employed to simulate maize productivity in agroforestry systems with up to 50% shading, but caution is required at higher levels of shading.  相似文献   

3.
Agroforestry systems are widely practiced in tropical forests to recover degraded and deforested areas and also to balance the global carbon budget. However, our understanding of difference in soil respiration rates between agroforestry and natural forest systems is very limited. This study compared the seasonal variations in soil respiration rates in relation to fine root biomass, microbial biomass, and soil organic carbon between a secondary forest and two agroforestry systems dominated by Gmelina arborea and Dipterocarps in the Philippines during the dry and the wet seasons. The secondary forest had significantly higher (p < 0.05) soil respiration rate, fine root biomass and soil organic matter than the agroforestry systems in the dry season. However, in the wet season, soil respiration and soil organic matter in the G. arborea dominated agroforestry system were as high as in the secondary forest. Whereas soil respiration was generally higher in the wet than in the dry season, there were no differences in fine root biomass, microbial biomass and soil organic matter between the two seasons. Soil respiration rate correlated positively and significantly with fine root biomass, microbial biomass, and soil organic C in all three sites. The results of this study indicate, to some degree, that different land use management practices have different effects on fine root biomass, microbial biomass and soil organic C which may affect soil respiration as well. Therefore, when introducing agroforestry system, a proper choice of species and management techniques which are similar to natural forest is recommended.  相似文献   

4.
A 26 years old agroforestry plantation consisting of four multipurpose tree species (MPTs) (Michelia oblonga Wall, Parkia roxburghii G. Don, Alnus nepalensis D. Don, and Pinus kesiya Royle ex-Gordon) maintained at ICAR Research Complex, Umiam, Meghalaya, India were compared with a control plot (without tree plantation) for soil fertility status and CO2 efflux. The presence of trees improved all the physico-chemical and microbial biomass parameters studied in this experiment. Relative to control, soils under MPTs showed significant increases of 17 % soil organic carbon, 26 % available nitrogen (AN), 28 % phosphorus (AP), 50 % potassium (AK), 65 % mean weight diameter (MWD) of aggregates, 21 % moisture and 34 % soil microbial biomass carbon (MBC) while reducing the mean bulk density (7 %). However, these parameters significantly differed among the tree species i.e., soils under A. nepalensis and M. oblonga had higher values of these attributes except bulk density, than under other species. Irrespective of treatments, the values of all these attributes were higher in surface soils while bulk density was highest in subsurface (60–75 cm). Cumulative CO2 efflux under MPTs was significantly higher (15 %) and ranged from 1.71 g 100 g?1 (M. oblonga) to 2.01 g 100 g?1 (A. nepalensis) compared to control at 150 days of incubation. In all the treatments, increment in temperature increased the oxidation of soil organic matter, thereby increased the cumulative CO2 efflux from soils. Of the tree species, with increment in temperature, A. nepalensis recorded more CO2 efflux (2.50 g 100 g?1) than other MPTs but the per cent increase was more in control plot. P. kesiya and A. nepalensis recorded highest activation energy (59.1 and 39 kJ mol?1, respectively). Net organic carbon sequestered in soil was highest under A. nepalensis (25.7 g kg?1) followed by M. oblonga (19.3 g kg?1), whereas control showed the lowest values. Amount of net carbon stored in the soil had significant and positive correlation with MBC (r = 0.706**), MWD (r = 0.636*), and AN (r = 0.825**).  相似文献   

5.
Agroforestry practice is believed to be an effective means of maintaining and improving soil fertility, and is widely used by farmers around the world. To gain better understanding of the effects of agroforestry practice on soil fertility, the organic carbon content, total nitrogen content, microbial biomass, basal respiration, and activity of soil enzymes at three soil depths (0–10, 10–20, and 20–30 cm) of Ginkgo (Ginkgo biloba L.)–tea (Camellia sinensis (L.) O. Kuntze) agroforestry systems were investigated. Study plots were established in Yushan Farm in Changshu, Jiangsu Province, China. These involved two densities of Ginkgo trees mixed with tea (G1 and G2) and monoculture tea systems (G0). The results showed that C, N, microbial biomass, and enzyme activity were higher in surface soil than in soil from the middle and lower layers whereas pH and metabolic quotient increased with soil depth. pH, microbial biomass C, N, basal respiration, and catalase and invertase activity in the 0–10 cm layer were significantly lower for G0 than for G1 and G2. Polyphenoloxidase activity in the 0–10 cm layer was significantly lower for G2 than for G0 and G1. Metabolic quotient in the 20–30 cm layer was significantly higher for G0 than for G2. The activity of soil enzymes, including catalase, dehydrogenase, urease, protease, and invertase, significantly and positively correlated with soil organic carbon and total nitrogen. The results of this study suggest that growing tea with Ginkgo could be regarded as good agroforestry practice which could enhance accumulation of organic matter in soil, improve the activity of soil enzymes, and maintain soil productivity and sustainability.  相似文献   

6.
Diversity of trees and shrubs in agricultural systems contributes to provision of wood and non-wood products, and protects the environment, thereby, enhancing socioeconomic and ecological sustainability of the systems. This study characterizes the diversity, density and composition of trees in the agroforestry homegardens of Sidama Zone, Southern Ethiopia, and analyses physical and socioeconomic factors influencing diversity and composition of trees in the systems. A total of 144 homegardens were surveyed from 12 sites. In total, 120 species of trees and shrubs were recorded of which, 74.2 % were native to the area. The mean number of tree species per farm was 21. Density of trees varied between sites with mean values ranging from 86 to 1,082, and the overall average was 475 trees ha?1. Four different crop-based enset (Enset ventricosum (Welw.) Cheesman)-coffee homegarden types were recognized and they differed not only in the composition of major crops but also in the diversity, density and composition of trees. The composition, diversity and density of trees is influenced by physical and socioeconomic factors. The major physical factors were geographical distance between sites and differences in altitude of farms. The most important socioeconomic factors were farm size and access to roads. Tree species richness and density increased with farm size. Increased road access facilitated marketing opportunities to agricultural products including trees, and lead to a decline in the basic components of the system, enset, coffee and trees. In the road-access sites, the native trees have also been largely replaced with fast growing exotic species, mainly eucalypts. The decrease in diversity of trees and perennial components of the system, and its gradual replacement with new cash and annual food crops could jeopardize the integrity and complexity of the system, which has been responsible for its sustenance.  相似文献   

7.
Guazuma ulmifolia was experimentally pruned to determine when pruning should begin during the rainy season in order to extend the production of green tree-forage during the dry season. Three prunings (P-1, P-2, and P-3) were performed (5 weeks apart) during the rainy season (August, September, and October) and four forage harvests (C-a, C-b, C-c, and C-d) (3 weeks apart) took place during the dry season (February, March, and April). Over 2 years, forage biomass production was evaluated as total biomass (g dry matter tree?1), biomass of the morphological components (leaves, stems, and dead matter), and nutritional quality (crude protein, fiber, lignin, and digestibility). Date of pruning affected the production of total biomass (P = 0.001) with the earliest pruning (P-1) yielding the greatest forage quantity, while stems (P = 0.022) and dead matter (P = 0.032) varied due to a year by pruning interaction. Total biomass, leaves, stems, and dead matter varied by the interaction between forage harvest and year for all four variables (P < 0.037). In both years, the largest forage harvest occurred in C-b (P < 0.05), leaf production was highest in C-a and C-b (P < 0.001), stem production was greatest in C-b (P = 0.013) and dead matter was highest in C-b and C-d (P = 0.002). Leaf crude protein ranged between 10 and 19 %, and the interaction of pruning by forage harvest by year was significant (P = 0.035). Digestibility, neutral and acid detergent fiber and lignin differed significantly because of the interaction between forage harvest and year (P < 0.005), with February showing the lowest values for fiber and the highest digestibility. The best time to prune G. ulmifolia is in August so that the young trees will produce more total biomass with a higher crude protein content. The most suitable moment for forage harvest is in February when the trees have more leaves with greater digestibility and less fiber.  相似文献   

8.
Grewia optiva Drummond is one of important agroforestry tree species grown by the farmers in the lower and mid-hills of western Himalaya. Different models viz., monomolicular, logistic, gompetz, allometric, rechards, chapman and linear were fitted to the relationship between total biomass and diameter at breast height (DBH) as independent variable. The adjusted R2 values were more than 0.924 for all the seven models implying that all models are apparently equally efficient. Out of the six non-linear models, allometric model (Y = a × DBH b ) fulfils the validation criterion to the best possible extent and is thus considered as best performing. Biomass in different tree components was fitted to allometric models using DBH as explanatory variable, the adjusted R2 for fitted functions varied from 0.872 to 0.965 for different biomass components. The t values for all the components were found non-significant (p > 0.05), thereby indicating that model is valid. Using the developed model, the estimated total biomass varied from 6.62 Mg ha?1 in 4 year to 46.64 Mg ha?1 in 23 year old plantation. MAI in biomass varied from 1.66–2.05 Mg ha?1 yr?1. The total biomass carbon stocks varied from 1.99 Mg ha?1 in 4 year to 15.27 Mg ha?1 in 23 year old plantation. Rate of carbon sequestration varied from 0.63–0.81 Mg ha?1 yr?1. Carbon storage in the soil up to 30 cm soil depth varied from 25.4 to 33.6 Mg ha?1.  相似文献   

9.
Tropical forests store a large part of the terrestrial carbon and play a key role in the global carbon (C) cycle. In parts of Southeast Asia, conversion of natural forest to cacao agroforestry systems is an important driver of deforestation, resulting in C losses from biomass and soil to the atmosphere. This case study from Sulawesi, Indonesia, compares natural forest with nearby shaded cacao agroforests for all major above and belowground biomass C pools (n = 6 plots) and net primary production (n = 3 plots). Total biomass (above- and belowground to 250 cm soil depth) in the forest (approx. 150 Mg C ha?1) was more than eight times higher than in the agroforest (19 Mg C ha?1). Total net primary production (NPP, above- and belowground) was larger in the forest than in the agroforest (approx. 29 vs. 20 Mg dry matter (DM) ha?1 year?1), while wood increment was twice as high in the forest (approx. 6 vs. 3 Mg DM ha?1 year?1). The SOC pools to 250 cm depth amounted to 134 and 78 Mg C ha?1 in the forest and agroforest stands, respectively. Replacement of tropical moist forest by cacao agroforest reduces the biomass C pool by approximately 130 Mg C ha?1; another 50 Mg C ha?1 may be released from the soil. Further, the replacement of forest by cacao agroforest also results in a 70–80 % decrease of the annual C sequestration potential due to a significantly smaller stem increment.  相似文献   

10.
Agroforestry is an ancient practice widespread throughout Africa. However, the influence of Sahelian agroforestry systems on carbon storage in soil and biomass remains poorly understood. We evaluated the carbon storage potential of three agroforestry systems (fallow, parkland and rangeland) and five tree species (Faidherbia albida, Acacia raddiana, Neocarya macrophylla, Balanites aegyptiaca and Euphorbia balsamifera) growing on three different soils (clay, sandy loam and sandy) in the Niayes zone, Senegal. We calculated tree biomass carbon stocks using allometric equations and measured soil organic carbon (SOC) stocks at four depths (0–20, 20–50, 50–80 and 80–100 cm). F. albida and A. raddiana stored the highest amount of carbon in their biomass. Total biomass carbon stocks were greater in the fallow (40 Mg C ha?1) than in parkland (36 Mg C ha?1) and rangeland (29 Mg C ha?1). More SOC was stored in the clay soil than in the sandy loam and sandy soils. On average across soil texture, SOC stocks were greater in fallow (59 Mg C ha?1) than in rangeland (30 Mg C ha?1) and parkland (15 Mg C ha?1). Overall, the total amount of carbon stored in the soil + plant compartments was the highest in fallow (103 Mg C ha?1) followed by rangeland (68 Mg C ha?1) and parkland (52 Mg C ha?1). We conclude that in the Niayes zones of Senegal, fallow establishment should be encouraged and implemented on degraded lands to increase carbon storage and restore soil fertility.  相似文献   

11.
Field experiments were conducted during rainy seasons of three consecutive years (2008–2010) to study the effect of green leaf manuring on dry matter partitioning and productivity of lowland rice (Oryza sativa L.). Green leaves of five indigenous agroforestry tree species viz., Erythrina indica, Acacia auriculiformis, Alnus nepalensis, Parkia roxburghii, and Cassia siamea were treated at 10 t ha?1 on fresh weight basis in rice fields and compared with recommended N–P2O5–K2O (80:60:40 kg ha?1) and control treatments. During 2008–2009 year, yield attributes and rice yield were greater in NPK plots as compared to the green-leaf manured ones. However, in the third year, green leaf manuring (except that of Alnus) surpassed even the recommended N–P2O5–K2O treatment in terms of dry matter production and yield; better response was however observed with Erythrina. The soil available N after final harvest increased by ca. 14–20 % in Alnus and Erythrina treated plots as compared to the control. Over all, it could be said that management of plant residues can have long-term implications apart from the desired maintenance of soil organic matter and improving crop yield.  相似文献   

12.
Among several agroforestry practices in the Central Rift Valley (CRV) of Ethiopia, Acacia tortilis-dominated Parkland agroforestry systems are common. Utilizable information regarding the effects of the tree species on soil conditions in Ethiopia is very scarce to be of use for improved agricultural productivity. This study was conducted in three land use types in CRV areas in Oromia National Regional State in Ethiopia. The aim of the study was to determine the effects of A. tortilis on soil fertility variations along a gradient from the tree base to open area in different land use types. Soil samples from surface layers (0–15 cm) were taken at four concentric transects distances from tree base (0.5, 2 and 4 m), compared with soil samples from the adjacent open areas (15 m distance from the tree canopy cover), and then analyzed following the standard procedures. The results of the study indicated that except for Na the amount of soil nutrients under A. tortilis were significantly varied (P < 0.05) in the land use types. Generally, comparisons between under the canopy and outside the canopy of the tree species indicated a highly significant difference on major soil fertility parameters. The effect of the tree species on soil fertility parameters was significantly higher with the distance from the tree base to outside of the canopy. But soil texture was not affected, indicating that it is more related to parent material and land use practices than the tree influence. The study revealed that the indigenous Parkland agroforestry practices of A. tortilis tree improve soil fertility. Hence, the soil patches observed under A. tortilis trees can be important local nutrient reserves, leading to soil heterogeneity in an otherwise uniform agricultural landscape. This may be important for the agricultural landscape health and on farm biodiversity conservation in agricultural landscapes of similar agroecological conditions.  相似文献   

13.
Ecosystem-level assessments of carbon (C) stocks of agroforestry systems are scarce. We quantified the ecosystem-level C stocks of one agroforestry-based oil palm production system (AFSP) and one agroforestry-based oil palm and cacao production system (AFSP+C) in eastern Amazonia. We quantified the stocks of C in four pools: aboveground live biomass, litter, roots, and soil. We evaluated the distribution of litter, roots, and soil C stocks in the oil palm management zones and in the area planted with cacao and other agroforestry species. The ecosystem-C stock was higher in AFSP+C (116.7 ± 1.5 Mg C ha?1) than in AFSP (99.1 ± 3.1 Mg C ha?1). The total litter-C stock was higher in AFSP+C (3.27 ± 0.01 Mg C ha?1) than in AFSP (2.26 ± 0.06 Mg C ha?1). Total root and soil C stocks (0–30 cm) did not differ between agroforestry systems. Ecosystem-C stocks varied between agroforestry systems due to differences in both aboveground and belowground stocks. In general, the belowground-C stocks varied spatially in response to the management in the oil palm and non-oil palm strips; these results have important implications for the monitoring of ecosystem-level C dynamics and the refinement of soil management.  相似文献   

14.
Most studies undertaken in the field of agroforestry have focussed on system design, soil fertility management, and system interactions. Less emphasis has been placed on biodiversity aspects. The aim of this study is to investigate the potential of indigenous, multistrata agroforests for maintaining native woody species diversity in the south-eastern Rift Valley escarpment, Ethiopia. A total of 60 farms, representing three agroforest types (enset-AF, enset-coffee-AF and fruit-coffee-AF), were randomly selected along altitudinal gradients. Enset (Ensete ventricosum) is a perennial, herbaceous monocarpic banana-like plant which serves as a food plant in Ethiopia. The three agroforests are results of the domestication of natural forests and intensification of the landuse systems centuries ago. Sample-based assessment protocols were employed to place sample quadrats and to measure all individuals in the quadrats. A total of 58 woody species, belonging to 49 genera and 30 families, was recorded. Of all woody species identified, 86% were native. The highest proportion of native woody species was recorded in enset-AF (92%), followed by enset-coffee-AF (89%) and fruit-coffee-AF (82%). Among native tree species, Millettia ferruginea and Cordia africana were the most widespread. In all, 22 native woody species were recorded as of interest for conservation, acccording to IUCN Red lists and local criteria. Among them, Pygeum africanum and Rhus glutinosa were categorised as vulnerable in the wild, and in need of conservation priority. The introduction of non-native fruit trees in agroforests can be a threat to maintenance of native woody species. Management strategies favoring enset and coffee will also put other native tree species at risk. A smaller number of native woody species was recorded in fruit-coffee-AF, but a higher mean basal area and stem number. The mean basal area and stem number ranged from 5.4?±?0.5 to 11.7?±?1.0?m2?ha?1 and 625?±?84 to 1,505?±?142 stems?ha?1, respectively. Altitude explained 68 and 71% of the variation in species richness and abundance, respectively. Finally, it is concluded that recognition of the indigenous agroforestry system as an option for maintaining native woody species should be given more attention, to counteract the local threat of these species from the wild.  相似文献   

15.
Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha?1), microbial biomass N (mean of 168?kg?ha?1) and mineralizable N (mean of 79?kg?ha?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.  相似文献   

16.
In a transect study involving 15 mature seasonally dry tropical forests growing on uniform geological substrate in the Yucatan Peninsula, Mexico, we analyzed the influence of a large reduction in mean annual precipitation (1,036–537 mm year?1) on carbon (C) and nitrogen (N) pools in soils. We investigated the C content in organic soil and in active fraction pools (organic matter and microbial biomass) and analyzed the dependence of these pools on precipitation. Carbon (total, inorganic and organic, and in microbial biomass) and N (total) concentrations in bulk soil decreased as rainfall increased from <600 mm year?1 >1,000 mm year?1. Additionally, in all organic matter fractions, C and N concentrations generally decreased with greater precipitation. Soil average C mineralization decreased by 61 % from the wettest to the driest region. Reduced precipitation during the dry season increased microbial biomass C and water-extractable C concentrations and decreased the C concentration in organic matter fractions. No other significant changes were observed between seasons in C concentrations, N concentrations or C mineralization. Overall, we conclude that physical (macroclimate) and biological processes are more active in soils in the wettest region, resulting in a faster turnover of organic matter.  相似文献   

17.
The current expansion of the oil palm (Elaeis guineensis Jacq.) in the Brazilian Amazon has mainly occurred within smallholder agricultural and degraded areas. Under the social and environmental scenarios associated with these areas, oil palm-based agroforestry systems represent a potentially sustainable method of expanding the crop. The capacity of such systems to store carbon (C) in the soil is an important ecosystem service that is currently not well understood. Here, we quantified the spatial variation of soil C stocks in young (2.5-year-old) oil palm-based agroforestry systems with contrasting species diversity (high vs. low); both systems were compared with a ~10-year-old forest regrowth site and a 9-year-old traditional agroforestry system. The oil palm-based agroforestry system consisted of series of double rows of oil palm and strips of various herbaceous, shrub, and tree species. The mean (±standard error) soil C stocks at 0–50 cm depth were significantly higher in the low (91.8 ± 3.1 Mg C ha?1) and high (87.6 ± 3.3 Mg C ha?1) species diversity oil palm-based agroforestry systems than in the forest regrowth (71.0 ± 2.4 Mg C ha?1) and traditional agroforestry (68.4 ± 4.9 Mg C ha?1) sites. In general, no clear spatial pattern of soil C stocks could be identified in the oil palm-based agroforestry systems. The significant difference in soil carbon between the oil palm area (under oil palm: 12.7 ± 2.3 Mg C ha?1 and between oil palm: 10.6 ± 0.5 Mg C ha?1) and the strip area (17.0 ± 1.4 Mg C ha?1) at 0–5 cm depth very likely reflects the high input of organic fertilizer in the strip area of the high species diversity oil palm-based agroforestry system treatment. Overall, our results indicate a high level of early net accumulation of soil C in the oil palm-based agroforestry systems (6.6–8.3 Mg C ha?1 year?1) that likely reflects the combination of fire-free land preparation, organic fertilization, and the input of plant residues from pruning and weeding.  相似文献   

18.
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   

19.
Aiming to support the use of native species from the Atlantic Rainforest in local agroforestry systems, we analysed chemical and biochemical components related to leaf decomposition of Inga subnuda, Senna macranthera, Erythrina verna, Luehea grandiflora, Zeyheria tuberculosa, Aegiphila sellowiana, and Persea americana. These tree species are native (except for P. americana) and commonly used in agroforestry systems in the Atlantic Rainforest. For the three first species (Fabaceae), we also analysed the remaining dry matter and released nutrients from leaves, using litter bags, and biological nitrogen fixation, using Bidens pilosa and Brachiaria plantaginea as references of non-N2-fixing plants. Leaves from I. subnuda, L. grandiflora, and P. americana had a lower decomposition rate than the other species, exhibiting negative correlations with lignin/N and (lignin+polyphenol)/N ratios. The percentages of remaining dry matter after 1 year were 69 % (I. subnuda), 26 % (S. macranthera) and 16 % (E. verna). Higher nutrient release was found in decreasing order from residues of E. verna, S. macranthera, and I. subnuda. The percentages of nitrogen fixation were 22.6 % (E. verna), 20.6 % (I. subnuda) and 16.6 % (S. macranthera). Diversification of tree species in agroforestry systems allows for input of diversified organic material and can contribute to maintaining and improving soil functions resulting in improvements of soil quality.  相似文献   

20.
Soil organic carbon (SOC) plays an important role in soil fertility and productivity. It occurs in soil in labile and non-labile forms that help in maintaining the soil health. An investigation was undertaken to evaluate the dynamics of total soil organic carbon (C tot), oxidisable organic carbon (C oc), very labile carbon (C frac 1), labile carbon (C frac 2), less labile carbon (C frac 3), non-labile carbon (C frac 4), microbial biomass carbon (C mic) and SOC sequestration in a 6-year-old fruit orchards. The mango, guava and litchi orchards caused an enrichment of C tot by 17.2, 12.6 and 11 %, respectively, over the control. The mango orchard registered highest significant increase of 20.7, 13.5 and 17.4 % in C frac 1, C frac 2 and C frac 4, respectively, over control. There is greater accumulation of all the C fractions in the surface soil (0–0.30 m). The maximum total active carbon pool was 36.2 Mg C ha?1 in mango orchard and resulted in 1.2 times higher than control. The passive pool of carbon constituted about 42.4 % of C tot and registered maximum in the mango orchard. The maximum C mic was 370 mg C kg?1 in guava orchard and constituted 4.2 % of C tot. The carbon management index registered 1.2 (mango orchard)- and 1.13 (guava and litchi orchard)-fold increase over control. The mango orchard registered highest carbon build rate of 1.53 Mg C ha?1 year?1 and resulted in 17.3 % carbon build-up over control. Among the carbon fractions, C frac 1 was highly correlated (r = 0.567**) with C mic.  相似文献   

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