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1.
The height of the annual flood crest of the Amazon at Iquitos has increased markedly in the last decade. During this same period, there has been greatly increased deforestation in the upper parts of the Amazon watershed in Peru and Ecuador, but no significant changes in regional patterns of precipitation. The change in Amazonian water balance during the last decade appears to be the result of increased runoff due to deforestation. If so, the long-predicted regional climatic and hydrological changes that would be the expected result of Amazonian deforestation may already be beginning.  相似文献   

2.
Coupled climate-carbon cycle models suggest that Amazon forests are vulnerable to both long- and short-term droughts, but satellite observations showed a large-scale photosynthetic green-up in intact evergreen forests of the Amazon in response to a short, intense drought in 2005. These findings suggest that Amazon forests, although threatened by human-caused deforestation and fire and possibly by more severe long-term droughts, may be more resilient to climate changes than ecosystem models assume.  相似文献   

3.
Territorial behavior is expected to buffer populations against short-term environmental perturbations, but we have found that group living in African lions causes a complex response to long-term ecological change. Despite numerous gradual changes in prey availability and vegetative cover, regional populations of Serengeti lions remained stable for 10- to 20-year periods and only shifted to new equilibria in sudden leaps. Although gradually improving environmental conditions provided sufficient resources to permit the subdivision of preexisting territories, regional lion populations did not expand until short-term conditions supplied enough prey to generate large cohorts of surviving young. The results of a simulation model show that the observed pattern of "saltatory equilibria" results from the lions' grouping behavior.  相似文献   

4.
Land-use allocation protects the Peruvian Amazon   总被引:2,自引:0,他引:2  
Disturbance and deforestation have profound ecological and socioeconomic effects on tropical forests, but their diffuse patterns are difficult to detect and quantify at regional scales. We expanded the Carnegie forest damage detection system to show that, between 1999 and 2005, disturbance and deforestation rates throughout the Peruvian Amazon averaged 632 square kilometers per year and 645 square kilometers per year, respectively. However, only 1 to 2% occurred within natural protected areas, indigenous territories contained only 11% of the forest disturbances and 9% of the deforestation, and recent forest concessions effectively protected against clear-cutting. Although the region shows recent increases in disturbance and deforestation rates and leakage into forests surrounding concession areas, land-use policy and remoteness are serving to protect the Peruvian Amazon.  相似文献   

5.
Fires in South America cause forest degradation and contribute to carbon emissions associated with land use change. We investigated the relationship between year-to-year changes in fire activity in South America and sea surface temperatures. We found that the Oceanic Ni?o Index was correlated with interannual fire activity in the eastern Amazon, whereas the Atlantic Multidecadal Oscillation index was more closely linked with fires in the southern and southwestern Amazon. Combining these two climate indices, we developed an empirical model to forecast regional fire season severity with lead times of 3 to 5 months. Our approach may contribute to the development of an early warning system for anticipating the vulnerability of Amazon forests to fires, thus enabling more effective management with benefits for climate and air quality.  相似文献   

6.
Archaeology and indigenous history of Native Amazonian peoples in the Upper Xingu region of Brazil reveal unexpectedly complex regional settlement patterns and large-scale transformations of local landscapes over the past millennium. Mapping and excavation of archaeological structures document pronounced human-induced alteration of the forest cover, particularly in relation to large, dense late-prehistoric settlements (circa 1200 to 1600 A.D.). The findings contribute to debates on human carrying capacity, population size and settlement patterns, anthropogenic impacts on the environment, and the importance of indigenous knowledge, as well as contributing to the pride of place of the native peoples in this part of the Amazon.  相似文献   

7.
Australian halictines belong to the primitive genus Lasioglossum or related subgenera. The underground nests have lined cells in series or clusters and sometimes at the end of laterals. Two full generations per year are produced in the communal nests. Overwintered and newly emerged females form unique "pseudosocieties" rather than matrifilial societies along Holarctic patterns. Several Chilalictus species produce a "male caste" of big-headed, flightless males, in addition to normal individuals. Oviposition of unfertilized eggs on large pollen balls causes such allometric bees.  相似文献   

8.
The importance of land-cover change in simulating future climates   总被引:14,自引:0,他引:14  
Adding the effects of changes in land cover to the A2 and B1 transient climate simulations described in the Special Report on Emissions Scenarios (SRES) by the Intergovernmental Panel on Climate Change leads to significantly different regional climates in 2100 as compared with climates resulting from atmospheric SRES forcings alone. Agricultural expansion in the A2 scenario results in significant additional warming over the Amazon and cooling of the upper air column and nearby oceans. These and other influences on the Hadley and monsoon circulations affect extratropical climates. Agricultural expansion in the mid-latitudes produces cooling and decreases in the mean daily temperature range over many areas. The A2 scenario results in more significant change, often of opposite sign, than does the B1 scenario.  相似文献   

9.
This study of a wealthy soybeancooperative in central Brazil shows howglobally ambitious institutions promotethemselves as regional organizations. Manystudies of cooperatives focus on their abilityto provide material improvements in the livesof cooperative members and to the locality inwhich they operate. Data from cooperativemembership, from promotional literature, andfrom local news article illustrate symbolicstrategies used by management to aggressivelypromote the idea that the cooperative saved theregion from underdevelopment. The claim that itrepresents regional interests is problematicbecause the cooperative has promoted frontierspeculation by its membership in the Amazon.The cooperative has also embracedexport-oriented agriculture and cattleranching, sidelining regional foodproduction.  相似文献   

10.
Brown与Levinson根据他们对言语行为的研究提出了他们的著名的面子保全理论。面子及对而子的需求在不同的文化中具有普遍性,因此本文根据而子保全论中的礼貌策略对著名的文化巨著红楼梦》中的言语行为进行了分析,并总结出其所用礼貌策略的不同文化内涵。  相似文献   

11.
This paper builds on previous research about the potential downsides of food sovereignty activism in relatively wealthy societies by developing a three-part taxonomy of harms that may arise in such contexts. These are direct opposition, false equivalence, and diluted goals and methods. While this paper provides reasons to resist complacency about wealthy-world food sovereignty, we are optimistic about the potential for food sovereignty in wealthy societies, and we conclude by describing how wealthy-world food sovereignty can be a location of either transnational solidarity or (at least) nonharmful forms of cooptation.  相似文献   

12.
The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this "Andean" substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.  相似文献   

13.
Smoking rain clouds over the Amazon   总被引:7,自引:0,他引:7  
Heavy smoke from forest fires in the Amazon was observed to reduce cloud droplet size and so delay the onset of precipitation from 1.5 kilometers above cloud base in pristine clouds to more than 5 kilometers in polluted clouds and more than 7 kilometers in pyro-clouds. Suppression of low-level rainout and aerosol washout allows transport of water and smoke to upper levels, where the clouds appear "smoking" as they detrain much of the pollution. Elevating the onset of precipitation allows invigoration of the updrafts, causing intense thunderstorms, large hail, and greater likelihood for overshooting cloud tops into the stratosphere. There, detrained pollutants and water vapor would have profound radiative impacts on the climate system. The invigorated storms release the latent heat higher in the atmosphere. This should substantially affect the regional and global circulation systems. Together, these processes affect the water cycle, the pollution burden of the atmosphere, and the dynamics of atmospheric circulation.  相似文献   

14.
Neotropical rivers support a diverse array of endemic taxa, including electric fishes of the order Gymnotiformes. A comprehensive survey of the main channels of the Amazon River and its major tributaries (>2000-kilometer transect) yielded 43 electric fish species. Biogeographical analyses suggest that local mainstem electric fish diversity is enhanced by tributaries. Mainstem species richness tends to increase downstream of tributary confluences, and species composition is most similar between tributaries and adjacent downstream mainstem locations. These findings support a "nodal" or heterogeneous model of riverine community organization across a particularly extensive and diverse geographical region.  相似文献   

15.
South Africa's Mediterranean-climate fynbos shrubland is a hot spot of species diversity, but its diversity patterns contrast strongly with other high-diversity areas, including the Amazon rain forest. With its extremely high levels of endemism and species turnover, fynbos is made up of dissimilar local communities that are species-rich but relatively poor in rare species. Using neutral ecological theory, we show that the relative species-abundance distributions in fynbos can be explained by migration rates that are two orders of magnitude lower than they are in tropical rain forests. Speciation rates, which are indexed by the "biodiversity parameter" Theta, are estimated to be higher than they are in any previously examined plant system.  相似文献   

16.
  目的  太阳辐射是森林生态系统最主要的能量来源,同时是影响森林生态系统区域气候与环境的最重要因素之一。探讨森林辐射长期变化特征,以期为气候变化、热带地区森林生产力、辐射能量平衡的研究以及辐射模型的建立和验证等建立研究基础。  方法  利用西双版纳热带季节雨林14年(2003—2016)辐射实测数据,对不同时间尺度的辐射各分量变化特征及其占总辐射的比率进行了比较分析。  结果  西双版纳热带季节雨林的总辐射、净辐射、反射辐射、大气逆辐射和林冠向上长波辐射的年平均值分别为:5 268.8、3 151.5、513.8、12 468.6、13 299.3 MJ/m2。总辐射的年际变化呈波动上升趋势,相反,净辐射的年际变化呈显著下降趋势;受大气状况的影响,大气逆辐射的年际变率较大,导致有效辐射的年际变率较大,而林冠向上的长波辐射年际变率较小;受研究区域特殊天气、季节性雾的影响,大气逆辐射日变化曲线在干季呈双峰型,雨季呈单峰型;在不同时间尺度上,林冠向上的长波辐射高于大气逆辐射,表明热带季节雨林林冠是大气的一个热源。净辐射占年总辐射的比率在60%左右,年际变化呈显著下降趋势,反射辐射和有效辐射占年总辐射的比率变化不大;净辐射占总辐射比率在昼间高,清晨和傍晚低,日变化曲线呈倒U型,反射辐射和有效辐射占总辐射的比率在昼间低,清晨和傍晚高,日变化曲线呈U型。  结论  西双版纳热带季节雨林辐射除受到太阳活动、云量和水汽等因子的影响外,还受区域小气候的影响,如季节性落叶和季节性雾。研究森林辐射特征的长期变化,对于气候变化研究、气候模型验证和森林生产力研究等具有重要意义。   相似文献   

17.
本文以县域为基本空间单元,以2000-2008年各空间单元的截面和时序数据为例,从综合农业区的角度,运用Theil系数及其嵌套分解法、空间相关模型等,结合GIS技术,探讨了江西省农业经济差异的动态变化及地域格局。研究表明:区域总差异经历了收敛趋同到逐渐扩大的过程,亚区内差异构成了农业区乃至全省总体差异的主体;差异空间集聚特征显著,并且集聚性先增强,后减弱;据区内差异组分与贡献,把各农业区划分为高值-上升、低值-波动等五种地域差异类型区;占主体的"H-H"、"L-L"类型地域分布相对稳定,分别为赣北、西北的农业区Ⅰ、Ⅱ与赣南的农业区Ⅵ;在此基础上,探讨了农业各产业对经济发展水平的影响,针对各农业区产业发展特点与存在的问题,提出了各农业区产业结构优化的方向。  相似文献   

18.
Reconstruction of an 83-year record (1903 to 1985) of the discharge of the Amazon River shows that there has been no statistically significant change in discharge over the period of record and that the predominant interannual variability occurs on the 2- to 3-year time scale. Oscillations of river discharge predate significant human influences in the Amazon basin and reflect both extrabasinal and local factors. Cross-spectrum analyses of Amazon flow anomalies with indicators of the El Ni?o-Southern Oscillation phenomenon suggest that the oscillations in the hydrograph are coupled to the tropical Pacific climate cycle.  相似文献   

19.
运用生态服务价值理论,从生态系统服务价值变化角度,计算了河北省新乐市土地利用变化对生态系统服务价值的影响。研究发现,2010~2020年,新乐市耕地、园地、林地面积增加,水域和其他未利用地面积减少。按照土地利用总体规划,2020年新乐市的生态系统服务价值为5.300亿元,将比2009年减少0.945亿元。新乐市土地利用方式的变化将会对区域生态环境带来负面影响,需要采取相应措施积极应对。  相似文献   

20.
Attention to diversity in women's attitudes toward farming and in women's patterns of farm work activity expands our understanding of the linkage between agrarian structure, regional history, and the behavior and values of individual farm women. We combine several disciplinary and methodological approaches to reveal patterns in work and values in a Southern case and then verify the existence of similar patterns in the Midwest. Two divergent conceptions of women's relationship to farm and marital partnership were found in a Georgia study, the agrarian and the industrial, and we explore how they emerged in the context of the political and economic history of the South. We find these marital models are linked today to different patterns of farm work. We then extend the Georgia analysis to a statewide survey of Ohio farm women, where attitudinal diversity is not as marked, due to the stronger agrarian traditions of the Midwest and its distinct political economy. We find similar patterns, however, in Ohio farm women's work and affirm the validity of Carbert's categorization of Rosenfeld's survey items. Attention to diversity in the work patterns, values, and attitudes of farm women highlights that the term traditional is a misnomer when applied to Southern women and reinforces the value of multi-disciplinary approaches and regional comparisons.  相似文献   

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