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 31 毫秒
1.
Changes in coffee economics are leading producers to reduce agrochemical use and increase the use of shade. Research is needed on how to balance the competition from shade trees with the provision of ecological services to the coffee. In 2000, long-term coffee experiments were established in Costa Rica and Nicaragua to compare coffee agroecosystem performance under full sun, legume and non-legume shade types, and intensive and moderate conventional and organic inputs. Coffee yield from intensive organic production was not significantly different from intensive conventional in Nicaragua, but in Costa Rica it was lower during three of the six harvests. Full sun coffee production over 6 years was greater than shaded coffee in Costa Rica (61.8 vs. 44.7 t ha?1, P = 0.0002). In Nicaragua, full sun coffee production over 5 years (32.1 t ha?1) was equal to coffee with shade that included Tabebuia rosea (Bertol.) DC., (27?C30 t ha?1) and both were more productive (P = 0.03) than coffee shaded with Inga laurina (Sw.) Willd. (21.6 t ha?1). Moderate input organic production was significantly lower than other managements under all shade types, except in the presence of Erythrina poepiggina (Walp.) O.F. Cook. Inga and Erythrina had greater basal area and nutrient recycling from prunings than other shade species. Intensive organic production increased soil pH and P, and had higher K compared to moderate conventional. Although legume shade trees potentially provide ecological services to associated coffee, this depends on management of the competition from those same trees.  相似文献   

2.
Intensification of coffee (Coffea arabica) production is associated with increases in inorganic fertilizer application and decreases in species diversity. Both the use of organic fertilizers and the incorporation of trees on farms can, in theory, reduce nutrient loss in comparison with intensified practices. To test this, we measured nutrient concentrations in leachate at 15 and 100 cm depths on working farms. We examined (1) organically managed coffee agroforests (38 kg N ha?1 year?1; n = 4), (2) conventionally managed coffee agroforests (96 kg N ha?1 year?1; n = 4), and (3) one conventionally managed monoculture coffee farm in Costa Rica (300 kg N ha?1 year?1). Concentrations of nitrate (NO3 ?-N) and phosphate (PO4 3?-P) were higher in the monoculture compared to agroforests at both depths. Nitrate concentrations were higher in conventional than organic agroforests at 15 cm only. Soil solutions collected under nitrogen (N)-fixing Erythrina poeppigiana had elevated NO3 ?-N concentrations at 15 cm compared to Musa acuminata (banana) or Coffea. Total soil N and carbon (C) were also higher under Erythrina. This research shows that both fertilizer type and species affect concentrations of N and P in leachate in coffee agroecosystems.  相似文献   

3.
Greater understanding of the influences on long-term coffee productivity are needed to develop systems that are profitable, while maximizing ecosystem services and lowering negative environmental impacts. We examine a long-term experiment (15 years) established in Costa Rica in 2000 and compare intensive conventional (IC) coffee production under full sun with 19 agroforestry systems combining timber and service tree species with contrasting characteristics, with conventional and organic managements of different intensities. We assessed productivity through coffee yield and coffee morphological characteristics. IC had the highest productivity but had the highest yield bienniality; in the agroforestry systems productivity was similar for moderate conventional (MC) and intensive organic (IO) treatments (yield 5.3 vs. 5.0 t ha?1 year?1). Significantly lower yields were observed under shade than full sun, but coffee morphology was similar. Low input organic production (LO) declined to zero under the shade of the non-legume timber tree Terminalia amazonia but when legume tree species were chosen (Erythrina poepiggiana, Chloroleucon eurycyclum) LO coffee yield was not significantly different than for IO. For the first 6 years, coffee yield was higher under the shade of timber trees (Chloroleucon and Terminalia), while in the subsequent 7 years, Erythrina systems were more productive; presumably this is due to lower shade covers. If IC full sun plantations are not affordable or desired in the future, organic production is an interesting alternative with similar productivity to MC management and in LO systems incorporation of legume tree species is shown to be essential.  相似文献   

4.
Tree removal in Latin American coffee agroforestry systems has been widespread due to complex and interacting factors that include fluctuating international markets, government-supported agricultural policies, and climate change. Despite shade tree removal and land conversion risks, there is currently no widespread policy incentive encouraging the maintenance of shade trees for the benefit of carbon sequestration. In facilitation of such incentives, an understanding of the capacity of coffee agroforests to store carbon relative to tropical forests must be developed. Drawing on ecological inventories conducted in 2007 and 2010 in the Lake Atitlán region of Guatemala, this research examines the carbon pools of smallholder coffee agroforests (CAFs) as they compare to a mixed dry forest (MDF) system. Data from 61 plots, covering a total area of 2.24 ha, was used to assess the aboveground, coarse root, and soil carbon reservoirs of the two land-use systems. Results of this research demonstrate the total carbon stocks of CAFs to range from 74.0 to 259.0 Megagrams (Mg)?C ha?1 with a mean of 127.6?±?6.6 (SE)?Mg?C ha?1. The average carbon stocks of CAFs was significantly lower than estimated for the MDF (198.7?±?32.1?Mg?C?ha?1); however, individual tree and soil pools were not significantly different suggesting that agroforest shade trees play an important role in facilitating carbon sequestration and soil conservation. This research demonstrates the need for conservation-based initiatives which recognize the carbon sequestration benefits of coffee agroforests alongside natural forest systems.  相似文献   

5.
The effect of different planting densities (100,000 and 167,000 plants ha?1) and levels of nitrogen fertilization (0, 261, 521, and 782 kg N ha?1 year?1) on biomass production and chemical composition of Moringa oleifera was studied in a split-plot design with four randomized complete blocks over 2 years with eight cuts year?1 at the National Agrarian University farm in Managua, Nicaragua (12°09′30.65″N, 86°10′06.32″W, altitude 50 m above sea level). Density 167,000 plants ha?1 produced significantly higher total dry matter yield (TDMY) and fine fraction yield (FFDM), 21.2 and 19.2 ton ha?1 respectively, compared with 11.6 and 11 ton ha?1 for 100,000 plants ha?1. Growth rate in 167,000 plants ha?1 was higher than in 100,000 plants ha?1 (0.06 compared with 0.03 ton ha?1 day?1). Average plant height was 119 cm irrespective of planting density. Fertilization at the 521 and 782 kg N ha?1 year?1 levels produced the highest TDMY and FFDM in both years of the study and along all cuts. The interaction between cut and year was significant, with the highest TDMY and FFDM during the rainy season in the second year. Chemical composition of fractions showed no significant differences between planting densities. Significantly higher crude protein content was found in the coarse fraction at fertilizer levels 521 and 782 kg N ha?1 year?1 (87.9 and 93.7 g kg?1 DM) compared with lower levels. The results indicate that Moringa can maintain up to 27 ton ha?1 dry matter yield under dry tropical forest conditions over time at a planting density of 167,000 plants ha?1 if the soil is regularly supplied with N at a level of approximately 521 kg ha year?1 in conditions where phosphorus and potassium are not limiting.  相似文献   

6.
A major challenge for cocoa producers in Côte d’Ivoire is to seek alternative shade trees or crop associations to adapt their planting devices and techniques to the shortage of forests. The recent tendency developed by farmers is to plant simplified orchards combining cacao and fruit trees. An on-farm trial was set up in a 5-year-old cocoa farm to compare a cacao monocrop planted at densities of 1,115 trees ha?1 with cacao intercropped with orange or avocado trees, both at 44 trees ha?1. Observations were done on incident light received by the cacao, vigour, growth and cocoa yields. On average, the cacaos received 100 % light in the monocrop, 89.6 % under orange trees and 80.6 % of incident light under avocado trees. They yielded 64.0 pods tree?1 year?1 in the monocrop (equivalent to 2.54 kg dry cocoa beans tree?1), 30.3 pods tree?1 when combined with orange trees and 28.3 pods tree?1 with avocado trees. The two combinations allowed cocoa yields equivalent to those observed in the region (0.58 kg dry cocoa beans tree?1). Vigour and yield were very highly correlated with the incident light received. Both the yield and the incident light are a logistic function of the planting distance from the shade tree. The inflexion point of the logistic functions corresponds to the minimum planting distance between the cacao and the intercropped fruit trees. On this basis, we suggest that the cacaos should not be planted closer than 6.50 ± 0.2 m to the orange or avocado trees.  相似文献   

7.
Some land-use systems in Saskatchewan, Canada include the nitrogen-fixing trees buffaloberry (Shepherdia argentea Nutt.), caragana (Caragana arborescens Lam.) and sea buckthorn (Hippophae rhamnoides L.). These species provide various ecological functions such as ameliorating soil moisture, light and temperature but little work has been done quantifying biological nitrogen fixation by these species. Greenhouse experiments were conducted to quantify N2-fixation using the 15N natural abundance and the 15N dilution methods. Buffaloberry failed to form nodules in all but one of the four replicates in the natural abundance experiment. Using the 15N dilution method, the percentage of N derived from atmosphere (%Ndfa) in the shoot of buffaloberry averaged 64 %. For caragana, the mean  %Ndfa was 59 and 65 % and seabuckthorn was 70 and 73 % measured using the natural abundance and dilution methods, respectively. Because of large variability in biomass production between plants grown in the natural abundance experiment and the dilution experiment, the amounts of N2 fixed also were very variable. Buffaloberry fixed an average of 0.89 g N m?2; the average for caragana ranged from 1.14 to 4.12 g N m?2 and seabuckthorn ranged from 0.85 to 3.77 g N m?2 in the natural abundance and dilution experiments, respectively. This corresponds to 16 kg N ha?1 year?1 for buffaloberry; an average of 15–73 kg N ha?1 year?1 in caragana and 11–67 kg N ha?1 year?1 in seabuckthorn. The substantial amounts of N2 fixed by these species indicate that they have the potential to contribute to the overall N balance in land-use systems in which they are included.  相似文献   

8.
In tropical areas of Mexico, Leucaena leucocephala is widely used in silvopastoral systems. However, little information exists on other native woody species of high forage potential, such as Guazuma ulmifolia. The aim of this study was to evaluate the components of biomass, forage yield and quality, and availability of N in fodder banks of L. leucocephala, G. ulmifolia, and a mixture of both species during dry and rainy seasons, under sub-humid tropical conditions. The experimental unit was a 5 × 10 m plot, containing three rows with 2 m between rows; each row had 20 plant positions with 0.50 m between plants. Within each plant position there was either a single plant, in the case of pure-crop, or two plants, in the case of mixed of both species. A complete randomized block design with three repetitions was used. In both seasons, there were a significantly greater proportion of leaves in the G. ulmifolia fodder banks (71 %) and in mixed fodder banks (69 %) than in L. leucocephala fodder banks (64 %). Consequently, these systems had leaf-to-stem ratios of 2.4, 2.2 and 1.9, respectively. The forage yield of fodder banks was not influenced by season. The mixed fodder bank had greater forage yield (5.1 t DM ha?1) than the L. leucocephala fodder bank (3.4 t DM ha?1) in each season. Additionally, the mixed fodder bank accumulated more forage yield during the experimental period (10.2 t DM ha?1 year?1) than G. ulmifolia (9.0 t DM ha?1 year?1) or L. leucocephala (6.9 t DM ha?1 year?1). The concentrations of CP, C and C:N were not influenced by season. Forage NDF and ADF concentrations were greater in the rainy season (476 g kg?1 DM) compared with the dry season (325 g kg?1 DM). Mixed fodder banks had the greatest N yield (185.9 kg ha?1) and consequently the greatest availability of N (371.8 kg N ha?1 year?1). We conclude that mixed fodder banks of L. leucocephala and G. ulmifolia are a better option for improving productivity and forage quality in comparison with pure fodder banks in Yucatan, Mexico.  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.
This study evaluated the effects of site-specific, soil-testing-based fertiliser recommendations on maize yields using the transdisciplinary (TD) process. The TD process utilizes knowledge from science and practice. Farmers, extension officers, local financial institutions, and other practitioners collaborated with local scientists from the University of Eldoret in the process of financing, purchasing, and applying fertilisers in adequate amounts and composition. A total of 144 farmers participated in the study, which lasted for two seasons. The data sampling was based on a randomized 2?×?3?×?4?×?2 factorial complete block design, including the following factors: TD (non-participation vs participation in the TD process); ST (soil testing in the following categories: fertiliser application with no soil testing, fertiliser application following government recommendations, and application of site-specific, soil-testing-based fertiliser recommendations), and location (Kapyemit, Kipsomba, Ng’enyilel, and Ziwa). The “no soil testing” (ST1) category refers to farmers’ own practices at an average fertilisation of about 60?kg?N?ha?1 and 15?kg?P?ha?1. The government recommendation (ST2) calls for 75?kg?N?ha?1, 25?kg?P?ha?1, and 6?t?ha?1 manure, and site-specific fertiliser recommendations (ST3) were based on actual soil-testing results; generally, this resulted in the recommendation of 90?kg?N?ha?1, 30?kg?P?ha?1, 25 kg K ha?1, 2?t?ha?1 lime, and 1?t?ha?1 manure. Highly significant effects were seen where farmers participated in the TD process (TD) for soil testing (ST). The farmers’ yields in Uasin Gishu County of 4.5?t?ha?1 increased by approximately 1.5?t?ha?1 based on site-specific, soil-testing fertilisation recommendations and by approximately 1.0?t?ha?1 based on participation in the transdisciplinary process. However, as indicated by a significant interaction of the variables ST and TD—and while there is a significant main effect of participating in a TD process—the latter increase occurs only if site-specific, soil-testing-based recommendations can be used in the transdisciplinary process with farmers.  相似文献   

11.
Afforestation and ecological restoration have often been carried out with fast-growing exotic tree species because of their high apparent growth and yield. Moreover, fast-growing forest plantations have become an important component of mitigation measures to offset greenhouse gas emissions. However, information on the long-term performance of exotic and fast-growing species is often lacking especially with respect to their vulnerability to disturbance compared to native species. We compared carbon (C) storage and C accumulation rates in vegetation (above- and belowground) and soil in 21-year-old exotic slash pine (Pinus elliottii Engelm.) and native Masson pine (Pinus massoniana Lamb.) plantations, as well as their responses to a severe ice storm in 2008. Our results showed that mean C storage was 116.77 ± 7.49 t C ha?1 in slash pine plantation and 117.89 ± 8.27 t C ha?1 in Masson pine plantation. The aboveground C increased at a rate of 2.18 t C ha?1 year?1 in Masson pine and 2.23 t C ha?1 year?1 in slash pine plantation, and there was no significant difference in C storage accumulation between the two plantation types. However, we observed significant differences in ice storm damage with nearly 7.5 % of aboveground biomass loss in slash pine plantation compared with only 0.3 % loss in Masson pine plantation. Our findings indicated that the native pine species was more resistant to ice storm because of their adaptive biological traits (tree shape, crown structure, and leaf surface area). Overall, the native pine species might be a safer choice for both afforestation and ecological restoration in our study region.  相似文献   

12.
Scattered trees and woodlots are a prominent feature of agricultural landscapes of Rwanda. However, little is known about their characteristics and their contribution to farmers’ wood needs. Here, we present the results of a survey of (a) the abundance, composition, and size of trees and woodlots in the low, medium and high altitude regions of Rwanda, (b) total woody biomass and biomass for fuelwood at farm and landscape levels, and (c) opportunities for their sustainable use. Scattered trees occurred in all landscapes at minimum densities ranging from 20 to 167 trees ha?1. Of the 56 tree genera recorded, a handful of tree species dominated, with the ten most common species accounting for over 70 % of all trees recorded. Most of them provided fuelwood, fruit and timber to farm owners. Woodlots occurred on about 40 % of the survey farms and consisted for 90 % of eucalyptus coppice. Woody biomass dry weight of scattered trees on agricultural landscape was 0.7 t ha?1 in low altitude region (LAR), 3 t ha?1 in medium altitude region (MAR), and 1 t ha?1 in high altitude region (HAR). Dry weight woody biomass in woodlots (<0.5 ha) was the highest in MAR (221 t ha?1), followed by that in HAR (205 t ha?1) and least in LAR (96 t ha?1). About 80 % of total woody biomass in trees and woodlots on farmland was useable biomass for fuelwood, indicating that the production of fuelwood on agricultural land was important. Woody biomass on agricultural land was higher than that in forest plantations, and was potentially sufficient to reduce the gap between fuelwood supply and demand when the entire agricultural area was taken into account. In order to achieve this on agricultural land, while contributing to food security and environmental conservation as well, smallholder farmers must be provided with incentives to grow woodlots and to adopt agroforestry systems, thereby considering the trade-offs with agricultural production. Strategies to encourage smallholder farmers to increase the use of agroforestry have to account for the farmers’ ecological and socioeconomic conditions.  相似文献   

13.
In the Northern and Baltic countries, grey alder is a prospective tree species for short-rotation forestry. Hence, knowledge about the functioning of such forest ecosystems is critical in order to manage them in a sustainable and environmentally sound way. The 17-year-long continuous time series study is conducted in a grey alder plantation growing on abandoned agricultural land. The results of above- and below-ground biomass and production of the 17-year-old stand are compared to the earlier published respective data from the same stand at the ages of 5 and 10 years. The objectives of the current study were to assess (1) above-ground biomass (AGB) and production; (2) below-ground biomass: coarse root biomass (CRB), fine root biomass (FRB) and fine root production (FRP); (3) carbon (C) and nitrogen (N) accumulation dynamics in grey alder stand growing on former arable land. The main results of the 17-year-old stand were as follows: AGB 120.8 t ha?1; current annual increment of the stem mass 5.7 t ha year?1; calculated CRB 22.3 t ha?1; FRB 81 ± 10 g m?2; nodule biomass 31 ± 19 g m?2; fine root necromass 11 ± 2 g m?2; FRP 53 g DM m?2 year?1; fine root turnover rate 0.54 year?1; and fine root longevity 1.9 years. FRB was strongly correlated with the stand basal area and stem mass. Fine root efficiency was the highest at the age of 10 years; at the age of 17 years, it had slightly reduced. Grey alder stand significantly increased N and Corg content in topsoil. The role of fine roots for the sequestration of C is quite modest compared to leaf litter C flux.  相似文献   

14.
Cacao agroforestry systems (cacao-AFS) produce abundant litter. After decomposing, litter releases nutrients into the soil. The aim of this research was to estimate litter production and its nutrient content in 35- and 55-year-old cacao-AFS. The research was conducted in three cacao-AFS of each age, in Cardenas, Tabasco, México. Four traps per cacao-AFS were used to collect litter. Litter was collected every 15 days for one year. It was then fractioned into cacao leaves, shade tree leaves, petioles, branches and stems, and cacao flowers and fruits. To determine nutrient content of litter, samples were composited by age of cacao-AFS and by season of the year. Then chemical analysis was done in triplicate. Data were subjected to analysis of variance, orthogonal contrasts, and Student t and Duncan tests. Cacao-AFS produce litter all year. Thirty-five-year-old cacao-AFS produced more litter than 55-year-old cacao-AFS (2042 vs 1570 kg DM ha?1 year?1). Except for the shade tree leaf fraction (559.5 vs 642 kg DM ha?1), 35-year-old cacao-AFS were superior to 55-year-old cacao-AFS in all the other litter fractions. Cacao leaf fraction was the main source of litter in cacao-AFS of both ages. Neither age of cacao-AFS nor the season of the year affected N, K, Zn or S content in litter. Orthogonal contrasts indicated statistical differences between ages of cacao-AFS for P, Ca, and Fe content in litter. Both N–P–K–Ca–Mg contents in litter of 35-year-old cacao-AFS (1.2–0.4–1.2–1.7–0.4%) and in litter of 55-year-old cacao-AFS (1.1–0.6–1.2–1.4–0.4%) are enough to recover the nutrients extracted by the cacao crop.  相似文献   

15.
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   

16.
Although agrosystems are recognized for their socio-economic value, few works have been conducted to assign its sequestration potential and ecological services. Accordingly, this study aimed to evaluate the ecological services of the eucalyptus stands in order to permit to small producers the access in carbon credit market. Three stands were selected according to age. Data were compared to that of a savannah (control). In total, 12,817 individuals belonging to 30 families, 53 genera and 70 species were identified in the plantations against 7107 individuals belonging to 24 families, 36 genera and 42 species in the savannah. Gmelina, Annona, Hymenocardia, Allophyllus, Daniellia, Terminalia and Piliostigma were the most represented genera. There was no significant difference between Savannah and plantations in terms of diversity (p > 0.05). The largest stock of carbon was found in oldest stands (108.51 ± 26.46 t C/ha) against 13.62 ± 3.03 t C/ha in Savannah. Eucalyptus saligna stored 39.66 t C/ha (4 t C ha?1year?1) in young stands; 57.28 t C/ha (6 t C ha?1year?1) in medium stands and 85.46 t C/ha (9 t C ha?1year?1) in old stands. The sequestration potential was higher in eucalyptus stands (398.25 t CO2eq/ha) than savannah (50.05 t CO2eq/ha). In total 956.82 t CO2eq/ha were sequestered for an economic value of $9568.45/ha against 50.05 t CO2eq/ha corresponding to $500.56/ha in Savannah. Eucalyptus stands are carbon sinks and could be an opportunity for financial benefits in the event of payment for environmental services in the context of the CDM process.  相似文献   

17.
Forest ecosystems can modify the atmospheric CO2 through biomass accumulation mostly in tree stems with diameter at breast height (DBH) ≥ 10 cm. Aboveground biomass increment (ΔAGB), and changes in stand AGB, no. stems and basal area (BA) were calculated from mortality, recruitment, and growth data of tree stems in tropical evergreen broadleaved forest, Central Highland Vietnam. Data were derived from ten 1-ha permanent plots established in 2004, where all stems with DBH ≥ 10 cm were tagged, identified to species, and measured for DBH in 2004 and 2012. In an 8-year duration, the increment was 53 ± 10 stems ha–1, 7.8 ± 0.3 m2 ha–1 for BA and 86.0 ± 4.6 Mg ha–1 for AGB. The stem mortality rate was 0.9% year–1 and the stem recruitment rate was 2.2% year–1. Annual ΔAGB was 10.8 Mg ha–1 year–1, equaling to 5.4 Mg C ha–1 year–1. Of which, tree stems of 35–80 cm DBH classes accounted for 65%. The results indicated that the forest is in stage of carbon sequestration. Any disturbances causing death of 35–80 cm DBH tree stems will much reduce carbon sequestration capacity and it will take a long time for AGB to return to pre-disturbance stage.  相似文献   

18.
The impacts of wood harvest, biomass removal and inter-rotation site management practices on productivity of Acacia mangium in South Sumatra were studied over 12 years across successive rotations. The productivity measured as MAI increased from 29.4 m3 ha?1 year?1 in the first to 48.0 m3 ha?1 year?1 in the second rotation. Whole tree harvesting (total stem, branches and leaves) caused a 21 % reduction in volume compared to harvesting merchantable wood alone in the next rotation. The rates of nutrients accumulation in trees were highest during the first year of growth, and declined from age 2 years. Significant amounts of nutrients were recycled through litter fall from 1 year after planting. Results highlight the importance of management which promotes nutrient supply on stand growth. Removal of slash and litter lowered soil pH, by about 0.1 unit. A small reduction was also found in soil organic carbon and nitrogen in the top soil during the first 3–4 years but values returned to pre-harvest levels by the end of the rotation. Extractable soil phosphorus and exchangeable cations decreased by the end of second rotation but these measures underestimate the nutrient pools available for A. mangium. These findings along with results from other studies have helped to implement operations which promote conservation of site resources for sustainable production in the region.  相似文献   

19.
Replantation of degraded forest using rapidgrowth trees can play a significant role in global carbon budget by storing large quantities of carbon in live biomass,forest floor,and soil organic matter.We assessed the potential of 20-year old stands of three rapid-growth tree species,including Alnus subcordata,Populus deltoides and Taxodium distichum,for carbon(C) storage at ecosystem level.In September 2013,48 replicate plots(16 m × 16 m) in 8 stands of three plantations were established.36 trees were felled down and fresh biomass of different components was weighed in the field.Biomass equations were fitted using data based on the 36 felled trees.The biomass of understory vegetation and litter were measured by harvesting all the components.The C fraction of understory,litter,and soil were measured.The ecosystem C storage was as follows: A.subcordata(626.5 Mg ha~(-1)) [ P.deltoides(542.9Mg ha~(-1)) [ T.distichum(486.8 Mg ha~(-1))(P \ 0.001),of which78.1–87.4% was in the soil.P.deltoides plantation reached the highest tree biomass(206.6 Mg ha~(-1)),followed by A.subcordata(134.5 Mg ha~(-1)) and T.distichum(123.3 Mg ha~(-1)).The highest soil C was stored in theplantation of A.subcordata(555.5 Mg ha~(-1)).The C storage and sequestration of the plantations after 20 years were considerable(25–30 Mg ha~(-1) year~(-1)) and broadleaves species had higher potential.Native species had a higher soil C storage while the potential of introduced species for live biomass production was higher.  相似文献   

20.
Coffee (Coffea canephora var robusta) is grown in Southwestern Togo under shade of native Albizia adianthifolia as a low input cropping system. However, there is no information on carbon and nutrient cycling in these shaded coffee systems. Hence, a study was conducted in a mature coffee plantation in Southwestern Togo to determine carbon and nutrient stocks in shaded versus open-grown coffee systems. Biomass of Albizia trees was predicted by allometry, whereas biomass of coffee bushes was estimated through destructive sampling. Above- and belowground biomass estimates were respectively, 140 Mg ha−1 and 32 Mg ha−1 in the coffee–Albizia association, and 29.7 Mg ha−1 and 18.7 Mg ha−1 in the open-grown system. Albizia trees contributed 87% of total aboveground biomass and 55% of total root biomass in the shaded coffee system. Individual coffee bushes consistently had higher biomass in the open-grown than in the shaded coffee system. Total C stock was 81 Mg ha−1 in the shaded coffee system and only 22.9 Mg ha−1 for coffee grown in the open. Apart from P and Mg, considerable amounts of major nutrients were stored in the shade tree biomass in non-easily recyclable fractions. Plant tissues in the shaded coffee system had higher N concentration, suggesting possible N fixation. Given the potential for competition between the shade trees and coffee for nutrients, particularly in low soil fertility conditions, it is suggested that the shade trees be periodically pruned in order to increase organic matter addition and nutrient return to the soil. An erratum to this article can be found at  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