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1.
Optimal management of Korean pine plantations in multifunctional forestry   总被引：1，自引：0，他引：1  
Korean pine is one of the most important plantation species in northeast China.Besides timber,it produces edible nuts and plantations sequester carbon dioxide from the atmosphere.This study optimized the management of Korean pine plantations for timber production,seed production,carbon sequestration and for the joint production of multiple benefits.As the first step,models were developed for stand dynamics and seed production.These models were used in a simulation–optimization system to find optimal timing and type of thinning treatments and optimal rotation lengths.It was found that three thinnings during the rotation period were optimal.When the amount or profitability of timber production is maximized,suitable rotation lengths are 65–70 years and wood production is 5.5–6.0 m~3 ha~(-1) a~(-1).The optimal thinning regime is thinning from above.In seed production,optimal rotation lengths are over 100 years.When carbon sequestration in living biomass is maximized,stands should not be clear-cut until trees start to die due to senescence.In the joint production of multiple benefits,the optimal rotation length is 86 years if all benefits(wood,economic profits,seed,carbon sequestration) are equally important.In this management schedule,mean annual wood production is 5.5 m~2 ha~(-1) and mean annual seed yield 141 kg ha~(-1).It was concluded that it is better to produce timber and seeds in the same stands rather than assign stands to either timber production or seed production.  相似文献   

2.
China’s state-owned forest enterprises have been important national timber production bases and their timber resources have been severely degraded during the past decades. About one-third of the state-owned forestland has been classified as commercial forestland, but no economic mechanisms have been laid out on governing timber plantations under market economy. This paper demonstrates the potential investment returns and analyzes factors that directly influence the returns of fast-growing poplar plantations in a state owned-forest enterprise, China Jilin Forest Industry Group (CJFIG), in northeastern China. We examined practically possible ranges of mean annual increment (MAI), general inflation rate, rate of forest fund, and interest rate in the study area. We then computed net present values (NPV), equivalent annual income (EAI) and internal rate of return (IRR) by using the minimum, medium, and maximum values of the each determinant above. Results showed NPV ranged from $1,024 to $6,925 ha?1, EAI ranged from $120 to $623 ha?1 year?1, and IRR ranged from 13.2 to 29.3 %. We show that growing poplar plantations could be two times more profitable than managing the existing natural forests in CJFIG by referring to EAI values. Improving MAI is the most effective way to increase both NPV and IRR while changes in the one-time tax at timber harvesting or changes in inflation rate have the least effect on NPV and IRR among the determinants studied. Discount rate, which can be easily manipulated by obtaining subsidies and policy-based loans, also has substantial influence on NPV. The state owned forest enterprises in China have special advantages to obtain relatively high economic returns in developing fast-growing plantation forests under market economy.  相似文献   

3.
We used the coupled forest and rockfall model PICUS Rock’n’Roll, linking a hybrid forest patch model and a 3D rockfall model, to assess the effects of four management scenarios (BAU: business as usual age class shelterwood approach; PFM1 and PFM2: rockfall protection management scenarios with slit-shaped gaps; NOM: no management scenario without any active silvicultural intervention) on rockfall protection and timber production on a 38 ha slope over 100 years. Compared to PFM1 and PFM2, we found slightly more harvested timber for the BAU scenario (BAU: 6.7 m³ha?1yr?1, PFM: 5.7–5.9 m³ha?1yr?1), but lower contribution margins (BAU: 55 €ha?1yr?1, PFM: 113–115 €ha?1yr?1). Overall, depending on rock size and forest state, 30–70% of the simulated rocks that would otherwise hit the road at the foot of the slope were stopped by the forest. While the PFM scenarios maintained a high rockfall protection level over 100 years (PE between 45–64%) the BAU showed periods of reduced protection (PE between 26–65%). The NOM scenario maintained favorable conditions in the beginning, but declining protection efficiency in the last decades of the century (PE 49–63%). We conclude that rockfall protection management can outperform BAU with regard to both timber production and rockfall protection.  相似文献   

4.
This study provides the first complete framework for the valuation of ecosystem services of agroforestry and uses a tree-based intercropping (TBI) system in southern Québec, Canada, as a case study. Ten ecosystem services were estimated, all of which were of interest and directly applicable to most agricultural systems worldwide: nutrient mineralization, water quality, soil quality, pollination, biological control, air quality, windbreak, timber provisioning, agriculture provisioning, and climate regulation. A mix of mathematical models for the quantification and economic valuation of various ecosystem services were used. The results revealed a total annual margin of $2,645 ha?1 y?1 (averaged over 40 years). The economic value of combined non-market services was $1,634 ha?1 y?1, which was higher than the value of marketable products (i.e. timber and agricultural products). An analysis of the present value suggested that agricultural products ranked highest among the ecosystem services taken singularly, followed by water quality, air quality, climate regulation, and soil quality maintenance. Total economic value of all ecosystem services for the rotation period was $54,782 ha?1, only one third of which was contributed by agricultural products. Although the total value of the ecosystem services provided by TBI was high, farmers only benefited from agricultural and timber products. Thus, government incentives are needed to interest farmers in adopting practices that benefit society as a whole.  相似文献   

5.
This study compared visitor preferences of forestry professionals across six European countries (Sweden, Denmark, Great Britain, Austria, Romania and Portugal) using a questionnaire survey. The 598 interviewees were asked to rank photographs depicting recently thinned experimental plots in a 13-year old stand of pedunculate oak (Quercus robur L.) according to the criterion: “Which forest environment do you prefer as a visitor?” The plots represented five different residual stem densities: 7000 (no thinning, very high stem density), 5300 (heavy thinning, high stem density), 1000 (very heavy thinning, medium stem density), 300 (extremely heavy thinning, low stem density/open stand) and 100 (solitary trees, very low stem density/very open stand) stems ha?1. The results indicated geographical variation in the preferences for different thinning practices in young stands of oak. Portuguese, Austrian and Romanian respondents generally favoured thinned, but dense stands, whereas Danish and British respondents preferred very heavily thinned stands. Swedish respondents preferred open stands resulting from extremely heavy thinning. Photographs taken along rows were favoured to photographs across rows, indicating a preference for scenes offering perspective and accessibility. The results indicate a variation of visitor preferences among forestry professionals for different silvicultural regimes. We interpret this in the context of national traditions and forestry paradigms that influence the shaping of preferences.  相似文献   

6.
Fast-growing poplar plantations are considered of great benefit to both timber production and carbon (C) sequestration, and are increasingly planted for multiple purposes worldwide. Irrigation and fertilization are common management practices in plantations in semiarid regions. However, quantitative investigation of the integrative effect of surface drip irrigation and fertigation (SDIF) on biomass and C storage in poplar plantations remains limited. In this study, we conducted a field experiment on a fast-growing poplar cultivar (Populus × euramericana cv. Guariento) plantation to compare the combination of surface drip irrigation and fertigation in growing seasons with conventional management (control; CK). Experiments repeated over 2 years showed that SDIF significantly increased biomass and C storage in both trees and soil in the plantation compared with the CK. Tree biomass C in SDIF-treated and CK stands after the first year of the experiment (age 5) was 6.20 and 4.05 t C ha?1, respectively, and the difference further increased, i.e., 15.18 and 8.63 t C ha?1, respectively, after the second year of the experiment (age 6). There was 53 and 76 % higher C storage in SDIF-treated trees than in the CK trees after the first and second years of the experiment, respectively. The SDIF increased the soil C concentration, especially in the surface soil at 0- to 40-cm depth. Soil organic C at a depth of 0–60 cm under the SDIF treatment was 45.42, 50.87 and 61.32 t C ha?1 in the 1st, 2nd and 3rd years, respectively, with annual increases of 12 and 21 % between the first and second, and second and third year, respectively. The corresponding soil organic C in the CK was 43.08, 43.57 and 47.92 t C ha?1 in the 1st, 2nd and 3rd years; the annual increases were only 1 and 10 %, respectively. The results confirmed the significant effect of the combined management on C storage in poplar plantations, thus we suggest it can be applied in forestry management, even though it generally did not change C concentrations of tree components.  相似文献   

7.
This study analyses the trade-off between bioenergy production and soil conservation through thinning operations in Norway spruce (Picea abies L. Karst) plantations in Denmark. Thinning operations were evaluated under different regimes and intensities for a complete rotation period of sixty years and for different site qualities (site-classes I–VI). Applying a dynamic forest growth modeling tool, evolution of forest structure was predicted to observe the potentials for biomass production and inevitable soil degradation. Results showed thinning from below, with a higher utilization (maintenance of a minimum basal area of 25 m2 ha?1) could produce more bioenergy. However, these operations require simultaneous severe forest soil degradation. Therefore, the optimum thinning for bioenergy production under preservation constraints was thinning from above with a lower intensity (maintenance of a minimum basal area of 45 m2 ha?1). The ratio of bioenergy win (kWh) to soil-loss (m3 ha?1) was calculated for this regime varying between 74,894 kWh m?3 in a high quality site (site-class I) and 6,516 kWh m?3 in a low quality site (site-class VI) with an average of 44,282 kWh m?3. However, this could not always preserve the highest amount of growing stock essential for natural dynamics of forest ecosystem with an exception of the low quality sites (site-class VI). Thus, when aiming at bioenergy production through thinning operations, trade-offs with soil conservation and growing stock preservation should be regarded to prevent environmental degradation.  相似文献   

8.
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   

9.
Biodiversity loss is a major problem in terms of loss of genetic and ecosystem services and more specifically via impacts on the livelihoods, food security and health of the poor. This study modeled forest management strategies that balance economic gains and biodiversity conservation benefits in planted tropical forests. A forest-level model was developed that maximized the net present value (NPV) from selling timber and carbon sequestration while maintaining a given level of biodiversity (as per the population density of birds). The model was applied to Eucalyptus urophylla planted forests in Yen Bai Province, Vietnam. It was found that the inclusion of biodiversity conservation in the model induces a longer optimal rotation age compared to the period that maximizes the joint value from timber and carbon sequestration (from 8 to 10.9 years). The average NPV when considering timber values plus carbon sequestration was 13 million Vietnamese Dong (VND) ha− 1 (765 USD ha− 1), and timber, carbon sequestration and biodiversity values were 11 million VND (676 USD) ha− 1. Given this differential, governments in such tropical countries may need to consider additional incentives to forest owners if they are to encourage maximizing biodiversity and its associated benefits. The results also have some implications for implementing the climate control measure of “Reducing Emissions from Deforestation and Forest Degradation-plus (REDD +)” in developing countries, i.e., payment for carbon sequestration and biodiversity benefits in planted forests.  相似文献   

10.
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   

11.
Most tropical forests outside protected areas have been or will be selectively logged because the timber industry is a main income-generating resource for many developing countries. Therefore, understanding the composition of commercial timber species and logging types is key for sustainable forest management in countries like Vietnam as they move toward fulfilling Reducing Emissions from Deforestation and Forest Degradation (REDD+) agreements. Seven 1-ha plots were surveyed in the Central Highland of Vietnam, and 18 commercial tree species from these plots, whose timber is widely used by local people for housing and furniture making and timber is easily sold at local markets for high prices, were analyzed. In total, 151 tree species with a diameter at breast height (DBH) of ≥?10 cm were recorded. The 18 commercially valuable species assessed in this study accounted for 33.2% of all stems (total of 524 stems ha?1 for all species), 47.1% of basal area (total of 34.35 m2 ha?1 for all species), and 50.8% of aboveground biomass/AGB (total of 262.68 Mg ha?1 for all species). Practicing diameter-limit harvesting of all commercially valuable species with DBH of ≥?40 cm, which is widely performed in Vietnam, will reduce the number of stems by 7%, basal area by 31.6%, and AGB by 38.2%. Because such harvesting practices cause severe ecological impacts on the remaining forest, logged forests may require >?40 years to recover the structure status of a pre-logged forest. In addition, the recovery of the 18 commercially valuable species may require a much longer time because they comprised 33.2% of stems. Permission for logging natural forests should be given in Vietnam to sustain lives of local communities, where logging has been prohibited. However, alternative harvesting systems, such as reduced-impact logging systems, should be considered. The systems selected must simultaneously generate economic returns for local people and respect the REDD+ agreements with regard to protecting biodiversity and reducing carbon emissions.  相似文献   

12.
Macro- (C, N, P, K, Ca and Mg) and micronutrient (Fe, Mn, Cu and Zn) reservoirs were estimated in the O (Oi+Oe+Oa) and in the A (0–10 cm depth) soil horizons of four stands of Nothofagus pumilio (lenga) from Tierra del Fuego which differ in their forestry characteristics. The type of soil layer (O and A) and the forest structure, as related to above-ground biomass storage, were assessed as a factor of variation in the nutrient reservoirs of both soils layers. Nutrient reservoirs showed similar ranges in both soil layers for total organic C (34–65 Mg ha?1), total N (1.5–3.5 Mg ha?1), rapidly available Ca (1.3–2.7 Mg ha?1) and Mg (0.18–0.36 Mg ha?1). Rapidly available K, available P, and medium-term available Fe and Cu were accumulated preferentially in A the horizons, whereas medium-term available Mn and Zn were mainly stored in the O horizons. The forest structure was not a statistically significant factor of variation on the nutrient reservoirs in the O horizons, although a legacy effect of the accumulated above-ground biomass on nutrient reservoirs in this soil layer can not be discarded. On the contrary, the pools of total organic C, total N, rapidly available K and medium-term available Cu and Zn in the A horizons varied significantly with the different forest structure. In terms of lenga forests sustainability, uppermost soils layers should be preserved as they accumulate most of the soil fertility which is essential for lenga regeneration after logging. The inclusion of the assessment of soil fertility in the management plans of the lenga forests in the ecotone of the Argentinean Tierra del Fuego is strongly recommended, as it will contribute to ensure a successful regeneration of lenga in logged areas.  相似文献   

13.
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   

14.
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   

15.
Steadily increasing damage to Norway spruce forests in Europe has caused researchers and managers to consider whether these forests can be converted to more stable ecosystems. In a central European mountain region, we investigated whether management systems (MSs) specified by regional stakeholders provide sound alternatives to the currently applied management. We used the forest model Sibyla to explore whether the tested MSs differ in their sensitivity to climate change in terms of altered biomass production, stand structure, forest damage, and financial outcome. The tested MSs were no-management (NM), currently applied management (BAU), and management based on the preferences of forest managers (FM) or on the preferences of other stakeholders (OSH). With NM, spruce remained dominant during the simulation period 2010–2100, and the rate of damage significantly increased. Spruce also remained dominant with FM, while the abundance of non-spruce species significantly increased with BAU and OSH. The rate of salvage logging converged at 50% of the total harvest for all MSs up to 2050. Climate change reduced biomass production (?15%) with all MSs but had a negligible effect on biodiversity indicators. The average initial value of the simulated stands was 20,000 € ha?1 and the nominal value in 2100 was between 1900 and 10,900 € ha?1. The Net Present Value calculated with the 2% interest rate was negative during the whole simulation period (?5600 to ?18,500 € ha?1 in 2100). Effect of climate change on all financial indicators was negative. Our findings indicate that secondary spruce forests are highly vulnerable and that the systems proposed by both forest managers and other regional stakeholders failed to significantly reduce forest damage and stabilize forest production.  相似文献   

16.
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   

17.
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   

18.
This study assessed the amount of carbon stored and the economic viability of the small-scale Clean Development Mechanism (CDM) carbon offsets in Pinus caribaea and Eucalyptus grandis plantations under varying rotations. Volume equations were used to estimate carbon stocks and merchantable wood volume in the plantations, while net present value (NPV) and annual equivalent value (AEV) were used as measures of profitability at the optimum economic rotation age as well as at the CDM-defined crediting period of 20 years. The findings show that over a 20-year rotation, E. grandis and P. caribaea plantations sequestered 638 and 418 t CO2-e ha?1, respectively. The NPVs of E. grandis and P. caribaea with carbon credits over the CDM carbon-crediting period of 20 years were US$2 540 ha?1 and US$1 814 ha?1, respectively. This is higher than the NPVs without carbon credits of US$1 543 ha?1 and US$1 390 ha?1 for E. grandis and P. caribaea, respectively. The AEV of E. grandis harvested at its optimal economic rotation of 10 years was US$316 ha?1. This is slightly higher than the AEV of US$298 ha?1, utilising the CDM carbon-crediting period of 20 years. In contrast, the AEV of P. caribaea under the 20-year CDM carbon-crediting period was higher than harvesting at the optimal economic rotation of 16 years without carbon credits. When the average CDM contract establishment costs exceed US$500 ha?1 and US$1 000 ha?1 for P. caribaea and E. grandis woodlots, respectively, it is not economically viable for one to participate in the CDM forest carbon offsets programme. In conclusion, the study results indicate that whereas E. grandis has a higher biological potential to sequester carbon than P. caribaea, it is currently not economically viable for participation in the CDM forest carbon offset scheme. In contrast, it is economically viable for P. caribaea plantations to participate in the CDM, if the CDM contract establishment costs are low.  相似文献   

19.
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   

20.
A total of 15 years of experimentation period (1995–2010) was divided into two phases. In the first phase (1995–2005), five mango based agri-horticultural models (AHM) viz. Mango + cowpea–toria, mango + cluster bean/okra–toria, mango + sesame–toria, mango + black gram–toria and mango + pigeon pea in addition to sole mango plantation (no intercrop) and in second phase (2005–2010), two mango based AHM (mango + colocasia and mango + turmeric) in addition to sole mango (no intercrop) were studied. The mean maximum cowpea equivalent yield (t ha?1) was harvested from cowpea (1.84) followed by okra (1.21), black gram (1.11), sesame (0.68) and mean minimum with pigeon pea (0.58). The crop yield reduction among the mango based AHM was observed from third year to tenth year. The positive correlation was found between light transmission and intercrops yields amongst all models during both phases. However, the correlation between mango canopy spread and intercrop yields shown negative trends. The yield reduction in intercrops varied from 37.0–52.6 % during first phase and 20.6–23.5 % during second phase of experimentation compared to sole crop. The results revealed that the fruit based AHM were effective in improving fruit yields of the mango. The mean maximum fruit yield of mango (7.02 t ha?1) was harvested with cowpea–toria crop rotation followed by black gram–toria (6.59 t ha?1) and minimum fruit yield (5.76 t ha?1) realized with sole mango tree during first phase (1999–2005). Likewise, mean maximum fruit yield (13.71 t ha?1) from mango tree was obtained in the turmeric block followed by (13.00 t ha?1) in colocasia block and minimum fruit yield with sole mango tree (11.86 t ha?1). All the treatments of AHM recorded higher soil moisture as compared to sole mango plantation during both phases. The moisture retention under different AHM was in the order of cowpea (13.32 cm) > black gram (13.29 cm) > pigeon pea (13.27 cm) > okra (12.42 cm) > sesame (12.17 cm) > sole mango (11.62 cm) during first phase, whereas moisture retention was observed in the order of turmeric (14.20 cm) > colocasia (14.01 cm) > sole mango (12.60 cm) during second phase. The cowpea–toria crop rotation with mango gave maximum benefit: cost ratio followed by okra–toria under rainfed conditions. Besides economic viability of cowpea–toria with mango, this system had improved tree growth as well as fruit yield of mango. In the second phase, mango + turmeric yielded more benefit than mango + colocasia system. In the first phase, the mango + cowpea–toria system improved organic carbon, total nitrogen, phosphorus, potash and reduced pH by 49.0, 56.3, 48.6, 58.5 and 11.6 %, respectively as compared to initial values whereas mango + turmeric system increased organic carbon, nitrogen, phosphorus, potash and reduction in pH by 51.0, 45.0, 29.7, 29.0 and 3.4 %, respectively over initial values within soil depths of 0–30 cm during second phased. Mango based AHM is recommended for adoption with selective intercrops up to 15 years of age of mango plantation for multiple outputs and good economic viability without impairing site fertility.  相似文献   

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