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1.
针对东北黑土区长缓坡地形条件下坡面产汇流集中易加剧土壤侵蚀的问题,本研究基于GIS和SIMWE(SIMulated Water Erosion)模型,引入连通性指数和水深空间分布作为水文连通性与径流路径的衡量指标.通过量化不同典型水土保持措施对土壤入渗速率和地表曼宁糙率的影响,构建梯田数字高程模型(DEM)模拟表征地表...  相似文献   

2.
通过2008-2009年在江苏南京农业大学牌楼试验站的盆栽试验,选择耐盐棉花品种中棉所44和盐敏感性品种苏棉12号为材料,模拟5种不同含盐水平的滨海盐土(0、0.35%、0.60%、0.85%和1.00%),分析了棉花生育期棉田土壤电导率与棉花功能叶光谱反射率和高光谱参数的关系,并建立了棉田土壤电导率(EC)的定量监测模型.结果表明:棉花功能叶光谱反射率在近红外和中红外区域均随土壤盐分水平的升高而升高;以敏感波段1350nm和2307 nm构建的归一化光谱指数NDSI(R1350,R2307)与土壤电导率的决定系数最高,基于此构建了基于NDSI(R1350,R2307)的棉田土壤EC监测模型:EC=-42.899NDSI(R1350,R2307)+27.338;在光谱微分参数中,以TM影像第5个波段的光谱反射率(TM5-SWIR)与棉田土壤EC的决定系数最高,构建了基于TM5-SWIR的棉田土壤EC监测模型:EC=0.0574 TM5-SWIR2-2.5928 TM5-SWIR+ 30.021.以NDSI(R1350,R2307)和TM5-SWIR为自变量的监测模型的预测精度均较高,分别为0.887和0.814,根均方差均较小,分别为1.09和1.29 dS·m-1.利用棉花功能叶NDSI(R1350,R2307)和TM5-SWIR均能较好地监测棉田土壤电导率.  相似文献   

3.
Questions: The assembly of arable weed communities is the result of local filtering by agricultural management and crop competition. Therefore, soil seed banks can reflect the effects of long‐term cumulative field management and crop sequences on weed communities. Moreover, soil seed banks provide strong estimates of future weed problems but also of potential arable plant diversity and associated ecological functions. For this, we evaluated the effects of different long‐term farming systems under the same crop rotation sequence on the abundance, diversity and community assembly of weed seed bank, as well as on the functional diversity and composition. Location: DOK (biodynamic [D], bioorganic [O], conventional [K]) long‐term trial, Therwil, Switzerland. Methods: The effects of long‐term contrasted farming systems (i.e., biodynamic, organic, conventional, mineral and unfertilised systems) and last crop sown (i.e., wheat and maize) were evaluated on different indicators of species and functional diversity and composition of the weed soil seed bank. Results: The results showed significant influences of 40 years of contrasted farming systems on the diversity and composition of the seed bank, with higher diversities being found in unfertilised and organic farming systems, but also higher abundances than those found under conventional systems. Organic farming also allowed higher functional richness, dispersion and redundancy. Different farming systems triggered shifts in species and functional assemblies. Conclusions: The results highlight the importance of organic management for the maintenance of a diverse arable plant community and its functions. However, such results emphasise the need for appropriate yearly management to reduce the abundance of settled weediness and prevent affecting crop production. The farm management filtered community composition based on functional traits. Although the soil seed bank buffers the long‐term farming and crop sequence, the last crop sown and, thus, the yearly management were important determinants of seed bank composition.  相似文献   

4.
黄土高原水土流失治理现状、问题及对策   总被引:19,自引:0,他引:19  
黄土高原位于黄河中游地区,是世界上水土流失最为严重的区域之一;黄土高原水土流失治理问题历来受到国家高度关注,涌现了种类多样的水土流失治理模式,目前还缺乏对黄土高原区域尺度水土流失治理模式的总结和整理。本文总结和整理了建国以来黄土高原主要的四类水土流失治理模式,生物措施模式主要由退耕还林、荒山造林和封山育林工程组成,工程措施模式包括修建梯田和淤地坝,以及近期涌现的治沟造地工程;小流域综合治理模式主要体现在坡面、沟道系统整治,生物和工程措施相结合的特点,区域综合整理模式则强调对生态系统进行整体保护、系统修复和综合治理,达到生态、社会、经济可持续发展。基于黄土高原水土流失治理模式存在的问题,提出了黄土高原水土流失治理模式调整和优化建议,以期对黄土高原生态恢复建设和水土流失科学治理提供科学依据。  相似文献   

5.
黄土高原丘陵沟壑区典型小流域水土流失治理模式   总被引:2,自引:1,他引:2  
袁和第  信忠保  侯健  李宗善  杨磊 《生态学报》2021,41(16):6398-6416
黄土高原是我国水土流失最为严重的区域,几十年的水土流失治理工作成果显著。当前生态文明建设已是我国国家战略之一,对黄土高原水土流失治理模式现状进行系统总结十分必要。对水土流失治理措施体系和流域土地利用情况系统分析,整理和总结了黄土高原6个典型流域的治理模式,包括治沟造地、防蚀固沙、生态农业发展、三大体系、梯田开发和水资源高效利用等6种模式。对比各治理模式发现,小流域综合治理模式是以环境治理为手段,从而达到改善人类生存和发展空间的终极目的,措施技术体系构建上体现了从坡面到沟道、工程措施植物措施相结合的特征;但不同的生态环境现状和社会经济条件下,治理模式有不同的表现形式。基于小流域水土流失治理模式的相似性和差异性,从自然地理条件和社会经济发展需求两方面探讨了流域水土流失治理模式,提出黄土高原水土流失治理模式形成机制框架,以期对当前黄土高原水土流失治理、黄河流域生态保护与高质量发展提供参考。  相似文献   

6.
结合ArcGIS与通用土壤流失方程(RUSLE),研究了1990—2015年三峡库区土壤保持量的时空动态变化规律,并分析了气候、水文、地形、社会等因子对土壤保持功能的影响。结果表明:1990—2015年三峡库区年均土壤保持量为5.79×109t (1004.23 t·hm-2),森林、灌木、草地、农田、未利用地的土壤保持功能依次降低。25年间三峡库区单位面积土壤保持量变化范围为818.73~1280.50 t·hm-2,2000年土壤保持服务功能最高。三峡库区土壤保持功能呈现东北高,西南低,长江沿岸及重庆主城区附近较低的空间分布趋势;土壤保持量随海拔增加呈现先增加后减小的趋势,海拔1000~1500 m的区域土壤保持能力最强;土壤保持量随坡度呈逐渐增加的趋势。海拔、坡度、降水、植被覆盖变化对土壤保持功能变化的贡献最大。人类活动干扰是土壤保持功能变化的主要驱动力。加强生态保护与修复,统筹治理,降低人为干扰,有助于提升三峡库区生态安全。  相似文献   

7.
Soil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha?1 yr?1 nitrogen (109(±8) kg yr?1 per household), 13.9(±0.3) kg ha?1 yr?1 phosphorus (26(±2) kg yr?1 per household), 79(±2) kg ha?1 yr?1 potassium (150(±11) kg yr?1 per household) and 2100(±40) kg ha?1 yr?1 organic carbon (3000(±300) kg yr?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) USSoil amendment with organic wastes in the Highlands of Ethiopia has been greatly reduced by widespread use of dung cakes and crop residues as fuels. This study assessed the interaction between household energy and recycling of nutrients and carbon to the soil using household survey, focus group discussions, key informant interviews, direct observations and measurements between 2014 and 2015 in Kumbursa village (Central Highlands of Ethiopia). All surveyed households were entirely dependent on biomass fuel for cooking, with production and consumption rates directly related to wealth status, which significantly varied (P < 0.001) among three farm wealth groups (poor, medium and rich). Crop residues and dung cakes accounted for 80(±3)% by energy content and 85(±4)% by dry mass weight of total biomass fuel consumption. Mean losses were 59(±2) kg ha?1 yr?1 nitrogen (109(±8) kg yr?1 per household), 13.9(±0.3) kg ha?1 yr?1 phosphorus (26(±2) kg yr?1 per household), 79(±2) kg ha?1 yr?1 potassium (150(±11) kg yr?1 per household) and 2100(±40) kg ha?1 yr?1 organic carbon (3000(±300) kg yr?1 per household). Rich farmers lost significantly more carbon and nutrients in fuel than farmers in other wealth groups. However, these losses were spread over a larger area, so losses per land area were significantly higher for medium and poor than for rich farmers. This means that the land of poorer farmers is likely to become degraded more rapidly due to fuel limitations than that of rich farmers, so increasing the poverty gap. The estimated financial loss per household due to not using dung and crop residues as organic fertilizer was 162(±8) US$ yr?1. However, this is less than their value as fuels, which was 490(±20) US$ yr?1. Therefore, farmers will only be persuaded to use these valuable assets as soil improvers if an alternative, cheaper fuel source can be found.  相似文献   

8.
9.
Land-use intensification in Mediterranean agro-forest systems became a pressure on biodiversity, concerning particularly the woodland sensitive species. In 2001, the effects of a land-use gradient from old-growth cork-oak forest to a homogeneous agricultural area were assessed using rove beetles as indicators in a Mediterranean landscape. The aim was to find which species were negatively affected by land-use intensification at the landscape level and whether they benefited from cork-oak patches occurring along the land-use gradient. A total of 3,196 rove beetles from 88 taxa were sampled from all landscape types. Agricultural area recorded significantly higher numbers of abundance and species richness in relation to the cork-oak mosaics, i.e. the old-growth forest and the managed agro-forest landscapes (montados). Moreover, 70% of rove beetle indicator species common enough to be tested by IndVal displayed their highest indicator value for agriculture, showing a lower number of woodland indicators in comparison to ground beetles. Nevertheless, one rove beetle taxon was considered a specialist of closed woodland mosaics while no specialist ground beetle was found for that landscape typology. Some rare rove beetle species were also important in typifying diversity patterns of old-growth cork-oak forests. Hence, future management in Mediterranean landscapes should take into account not only indicator species common enough to be tested by IndVal, but also rare and endemic species. Considering the added value of cork-oak woodland cover for sensitive rove and ground beetle diversity, the strengthening of cork-oak woodland connectivity seems to be a crucial management that is required in agricultural Mediterranean landscapes.  相似文献   

10.
魏云洁  甄霖  胡云锋  肖玉 《生态学报》2019,39(16):5809-5819
黄土高原是我国乃至全球水土流失治理的重点地区,经过40多年的治理,积累了种类多样的水土保持技术,对遏制和缓解水土流失和生态退化起到了良好作用。目前由于缺乏对具体治理需求的考量,从而影响水土保持技术效果的发挥,故技术评估和需求分析是选择适宜可行生态治理技术的重要环节。选择安塞纸坊沟流域和南沟流域的4个自然村为研究区,通过实地调研、利益相关者问卷调查和地理空间分析,旨在辨识并评估现有水土保持技术,识别技术需求,构建指标体系分析其立地适宜性和社会-经济可行性。研究结果表明,农户主要应用3类12项技术,工程类和生物类技术应用居多,生物类中地埂植物带和农业类技术应用较少;目前应用的水土保持技术整体效果较好,专家认为12项技术中工程类的梯田和淤地坝、生物类的地埂植物带综合表现最好,农户对梯田和水平沟、鱼鳞坑整地等坡面治理技术的效果评分高于专家,对淤地坝、谷坊等沟道治理技术以及集雨水窖和保护性耕作技术的效果评分低于专家,农户更关注技术的经济效益;技术存在的问题表现在梯田和治沟造地配套措施不完善,淤地坝、谷坊和水窖缺少修缮维护;识别出的技术需求分为3类,即新技术、改良技术和配套技术;纸坊沟流域的两个村立地条件更适宜人工造林种草,南沟流域的两个村更适宜天然封育,由社会-经济可行性分析可知,峙崾崄农户需要更多梯田种植果树及其配套技术,纸坊沟需要更多梯田种植作物或大棚蔬菜瓜果,大南沟需要造地后的配套技术,杏树窑需要造地种植作物及道路等配套基础设施。该研究是对黄土高原水土保持技术进行评估和需求分析的重要尝试,为生态治理决策提供参考。  相似文献   

11.
Glossina palpalis gambiensis and G. tachinoides are the main vectors of human and animal trypanosomoses in West Africa. In some parts of their distribution area, they co-exist in sympatry, but little is known about their interactions. This study aimed to explore their respective flight height and daily activity when co-existing or alone. Attractive targets were used, made of a black/blue/black cloth covered with adhesive film, so that all tsetse that landed were caught. The study was conducted in two areas in South Burkina Faso: Kartasso, upstream the Mouhoun river, where G. p. gambiensis is the only tsetse occurring; and Folonzo, on the Comoé river, where both species occur. Out of more than 3,800 tsetses caught in total, in Folonzo, G. tachinoides occurred at higher densities than G. p. gambiensis (84 vs 16% of the total densities). The mean height of capture was 55 cm for G. tachinoides, and 65 cm for G. p. gambiensis. As a comparison, in Kartasso where G. p. gambiensis is alone, the mean height of capture was 46 cm, these differences being statistically significant. In average, females were caught higher in altitude than males, and the two species showed a similar activity profile in the day. These results are discussed in the light of differences in the nature of the forest gallery, or possible interspecies competition behaviour in relation with their limited energy metabolism and flight capacities, or also with species differences in landing behavior, linked to host feeding detection. These observations have consequences on control tools releasing attractive odours, which may have contrasted efficacy depending of the flight height of the species.  相似文献   

12.
王力  卫三平  吴发启 《生态学报》2009,29(3):1543-1553
调查了黄土丘陵沟壑区燕沟流域刺槐(Robinia pseudoacacia)林地、辽东栎(Quercus liaotungensis)林地、荒草地、农地等不同植被类型条件下7种地类的土壤水分环境,分析不同植被类型对水分环境的生长响应.结果认为,各地类均存在一定程度的水分亏缺,亏缺量由大到小依次为:阳坡刺槐林地991.57mm、阳坡荒草地941.21mm、阴坡刺槐林地866.53mm、阳坡辽东栎林地815.89mm、阴坡荒草地790.27mm、阴坡辽东栎林地745.20mm、农地325.55mm.土壤水分的交换深度农地达320cm,阴坡荒草地为240cm,阴坡辽东栎林地为200cm,阴坡刺槐林地和阳坡辽东栎林地均为160cm,阳坡荒草地为140cm,阳坡刺槐林地为120cm.试验期间,林地、荒草地和农地分别约有10%、14%、30%的降水储存于土壤中,林地、荒草地600cm深土壤水库可利用水量62.6~309.0mm,与农地728.6mm相比土壤水库的调节能力很有限.受林木耗水量和土壤供水能力的双重影响,阳坡刺槐林枯梢现象严重,有整株枯死林木;阴坡刺槐林有明显的枯梢,但没有整株枯死的林木;辽东栎林也存在枯梢现象,但较刺槐林轻微,林木生长仍然十分旺盛.人工林地植被较高的截留和蒸腾耗水是造成土壤干燥化的主要原因,在植被建设中应遵循区域植被的演替规律,以水定植,尽量选择低耗水的适生乡土树种,采取自然修复为主、人工栽植为辅的措施,同时实施好水土保持措施.黄土丘陵区天然辽东栎林是当地植被演替的顶级群落,林地土壤的干燥化是黄土高原气候整体趋于旱化造成的,并不是人为干扰导致植被过度耗水造成的,这种土壤干燥化不宜归属于干层的范畴.判别土壤干层应以当地稳定天然植被群落的生物量水平和土壤水分状况为基准.  相似文献   

13.
土壤碳、氮、磷生态化学计量比可以广泛地指示群落的生态学动态过程,其研究可以为湿地生态系统的恢复与保护提供依据。以敦煌阳关湿地为研究对象,选取53个样地,分层(0—20、20—40 cm和40—60 cm)采集土壤样品,对3种植被盖度类型(高盖度、中盖度和低盖度)的土壤碳、氮、磷生态化学计量比特征及其影响因素进行了研究。结果表明:(1) 0—20、20—40 cm和40—60 cm土层C/N变化趋势均为:高盖度中盖度低盖度,C/P、N/P变化趋势均为:低盖度中盖度高盖度。(2)高盖度土壤C/N、C/P和N/P均随土层深度的增加而增大;中盖度土壤C/N随土层深度的增加而增大,C/P、N/P随土层深度的增加先减小后增大;低盖度C/N、C/P和N/P均随土层深度的增加先减小后增大。(3) 0—60 cm土层土壤水分与C/N显著负相关(P0.01),而与C/P、N/P显著正相关(P0.01),土壤盐分与C/P、N/P均显著负相关(P0.01),pH与C/P、N/P均显著正相关(P0.05),TP与C/N呈显著负相关(P 0.05),TN与C/P、OC与N/P均呈极显著正相关(P0.01)。由多元线性回归分析可知,土壤水分是土壤C/N、C/P和N/P的关键影响因子。  相似文献   

14.
We studied the population genetic structure of Cobitis vettonica, an endangered freshwater fish species endemic to the Iberian Peninsula, in order to propose a biogeographic model of the responses of species to the multiple changes that occurred in the Iberian hydrological system during the Quaternary period. We also deciphered the relationship of C. vettonica with its sister species C. paludica, particularly in sympatric areas, and provide genetic information for conservation purposes. To achieve this goal, we analyzed both mitochondrial and nuclear data (the cytochrome b and the nuclear recombination activating 1 genes) and a battery of single‐nucleotide polymorphisms (SNPs) of 248 individuals of C. vettonica or C. paludica from 38 localities, including some sympatric ones, covering the entire distribution area of C. vettonica. We highlight the important role played by the hydrogeomorphological processes and climatic changes that occurred in the Iberian Peninsula during the Quaternary on both the population structure of C. vettonica and its relationship with its sister species C. paludica. Our results support the genetic introgression of populations at the eastern limit of the distribution of C. vettonica. Furthermore, we postulate genetic introgression in sympatric areas. Finally, we propose the establishment or expansion of four Operational Conservation Units (OCUs) for C. vettonica, and highlight the threat faced by its populations due to the low level of genetic diversity detected for some of its populations and genetic introgression with C. paludica, which could eventually displace C. vettonica, resulting in a loss of diversity in this species.  相似文献   

15.
王彦阳  梁广文 《昆虫学报》2012,55(3):367-370
为了明确中华真地鳖Eupolyphaga sinensis Walker在自然界的分布及土壤性质对其存活的影响, 运用森下氏分散指数(Morisita’s index of dispersion)研究了中华真地鳖种群空间格局; 测试了4种不同土壤含水量(16%~29%)条件下中华真地鳖的卵孵化率与若虫存活率, 还测试了以野外不同来源土壤(山脚栖息土、 堆肥、 菜园土、 蘑菇料发酵土和黄砂红壤土)饲养时中华真地鳖若虫的存活率。结果表明, 中华真地鳖若虫在室外为聚集分布, 成虫为均匀分布, 从地面到40 cm的土壤深度都分布有中华真地鳖。土壤初始含水量21%和24%的卵孵化率最高, 其他含水量的卵孵化率均显著较低(P<0.05), 土壤初始含水量29%时的若虫存活率最低。堆肥、 山脚栖息土更适合中华真地鳖生存。结果可为该虫的采集、 饲养和深入研究提供科学的依据。  相似文献   

16.
干旱半干旱区坡面覆被格局的水土流失效应研究进展   总被引:17,自引:0,他引:17  
植被恢复与建设是控制水土流失的重要措施.在干旱半干旱地区,植被在空间上的分布呈现离散特征,在坡面上形成的裸地-植被镶嵌和植被条带分布等覆被格局对水土流失过程具有重要影响.覆被格局与水土流失关系研究是景观生态学格局与过程研究的重要内容.从植被斑块、坡面覆被格局对水土流失的影响与耦合覆被格局与水土流失的手段和方法三个方面对国内外相关研究进行总结分析.从中发现,植被类型、层次结构和形态特征是植被斑块尺度上影响径流泥沙的关键因素;不同覆被类型的产流产沙特征与覆被格局的准确描述是研究覆被格局水土流失效应的重要基础;坡面覆被格局对水土流失的影响关键在于其改变了径流泥沙运移和汇集的连续性,应重点关注径流泥沙源汇区的连通性和空间分布在水土流失中的作用;以坡面的精确覆被制图为基础,建立基于水土流失过程的覆被格局指数和耦合格局信息的径流与侵蚀模型是定量研究覆被格局影响的有效手段.今后应加强以下研究:以动态系统的观点研究覆被格局的变化对水土流失的影响,系统理解覆被格局与水土流失之间的相互联系与反馈机制,探讨两者间动态关系随尺度变化的规律性并发展尺度上推方法;构建过程意义明确且简单实用的格局指数,将覆被格局与水土流失过程有机联系起来;发展覆被格局的动态信息与产流产沙过程相结合的水文模型,加强对格局与径流泥沙反馈系统的耦合,建立真正意义上的覆被格局-水土流失过程耦合模型.  相似文献   

17.
We studied the distribution, size structure, growth, and diet of the freshwater prosobranch Melanopsis etrusca in experimental and natural population samples. This snail is endemic to isolated headwaters of thermal springs in central Italy. In recent times, several anthropogenic pressures such as water extraction and stream contamination have caused population declines and local extinctions of M. etrusca. Consequently, this species was included on the IUCN Red List of Threatened Species. The streams inhabited by M. etrusca had oligohaline waters; however, some physicochemical variability existed among sites. We found that the two variables most directly related to the patterns of distribution and life history of M. etrusca were water pH and temperature. In particular, individual growth was faster in streams with water temperatures constantly >30°C, which was reflected by a shorter life cycle than in cooler streams (13°–26°C), where snails showed a seasonal pattern of growth. Finally, we observed that individuals in a population that is exposed to extreme temperatures (>35°C) performed a peculiar behavior, spending long periods outside the water. We also found that the diet of M. etrusca reflected the local composition of the periphytic community and was dominated by macrophyte fragments. Our data suggest that heat‐adapted populations of M. etrusca hold the greatest potential for recolonization after collapse events. From a conservation perspective, reintroduction programs could be useful to avoid local extinction or bottleneck effects but at the risk of the loss of evolutionary innovations that may have emerged at the population level.  相似文献   

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The United Nations climate treaty may soon include a mechanism for compensating tropical nations that succeed in reducing carbon emissions from deforestation and forest degradation, source of nearly one fifth of global carbon emissions. We review the potential for this mechanism [reducing emissions from deforestation and degradation (REDD)] to provoke ecological damages and promote ecological cobenefits. Nations could potentially participate in REDD by slowing clear‐cutting of mature tropical forest, slowing or decreasing the impact of selective logging, promoting forest regeneration and restoration, and expanding tree plantations. REDD could also foster efforts to reduce the incidence of forest fire. Potential ecological costs include the accelerated loss (through displaced agricultural expansion) of low‐biomass, high‐conservation‐value ecosystems, and substitution of low‐biomass vegetation by monoculture tree plantations. These costs could be avoided through measures that protect low‐biomass native ecosystems. Substantial ecological cobenefits should be conferred under most circumstances, and include the maintenance or restoration of (1) watershed functions, (2) local and regional climate regimes, (3) soils and biogeochemical processes, (4) water quality and aquatic habitat, and (5) terrestrial habitat. Some tools already being developed to monitor, report and verify (MRV) carbon emissions performance can also be used to measure other elements of ecosystem function, making development of MRV systems for ecological cobenefits a concrete possibility. Analysis of possible REDD program interventions in a large‐scale Amazon landscape indicates that even modest flows of forest carbon funding can provide substantial cobenefits for aquatic ecosystems, but that the functional integrity of the landscape's myriad small watersheds would be best protected under a more even spatial distribution of forests. Because of its focus on an ecosystem service with global benefits, REDD could access a large pool of global stakeholders willing to pay to maintain carbon in forests, thereby providing a potential cascade of ecosystem services to local stakeholders who would otherwise be unable to afford them.  相似文献   

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