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1.
Identifying which introduced species have the greatest potential for establishment, spread and impact is critical for prioritizing pre‐ and post‐border control. Using species distribution modelling and existing species locations we assessed the establishment risk based on the climatic suitability areas of 25 plant species listed as eradication targets under South African regulations. To improve confidence, three bioclimatic models were used to predict the potential distribution of each species. This information was combined with the number of localities and the “eradication feasibility syndromes” in a scoring‐categorical system to rank the species. Three management groups were identified. Group “A” includes species with medium‐high establishment risk and higher likelihood to be eradicated, these species should be a priority for eradication. Group “B” includes species with a medium‐low establishment risk but given the low number of known population and the species characteristics, eradication is likely to be feasible. Finally species in group “C” scored a medium‐high establishment risk but the eradication would be difficult due to the high number of known localities. This ranking provides a rapid method to prioritize the management towards the eradication of new potential invasive plant species in the country combining the establishment risk, known number of localities and the inferred eradication success.  相似文献   
2.
Climate change may shift interactions of invasive plants, herbivorous insects and native plants, potentially affecting biological control efficacy and non‐target effects on native species. Here, we show how climate warming affects impacts of a multivoltine introduced biocontrol beetle on the non‐target native plant Alternanthera sessilis in China. In field surveys across a latitudinal gradient covering their full distributions, we found beetle damage on A. sessilis increased with rising temperature and plant life history changed from perennial to annual. Experiments showed that elevated temperature changed plant life history and increased insect overwintering, damage and impacts on seedling recruitment. These results suggest that warming can shift phenologies, increase non‐target effect magnitude and increase non‐target effect occurrence by beetle range expansion to additional areas where A. sessilis occurs. This study highlights the importance of understanding how climate change affects species interactions for future biological control of invasive species and conservation of native species.  相似文献   
3.
Increases in atmospheric temperature and nutrients from land are thought to be promoting the expansion of harmful cyanobacteria in lakes worldwide, yet to date there has been no quantitative synthesis of long‐term trends. To test whether cyanobacteria have increased in abundance over the past ~ 200 years and evaluate the relative influence of potential causal mechanisms, we synthesised 108 highly resolved sedimentary time series and 18 decadal‐scale monitoring records from north temperate‐subarctic lakes. We demonstrate that: (1) cyanobacteria have increased significantly since c. 1800 ce , (2) they have increased disproportionately relative to other phytoplankton, and (3) cyanobacteria increased more rapidly post c. 1945 ce . Variation among lakes in the rates of increase was explained best by nutrient concentration (phosphorus and nitrogen), and temperature was of secondary importance. Although cyanobacterial biomass has declined in some managed lakes with reduced nutrient influx, the larger spatio‐temporal scale of sedimentary records show continued increases in cyanobacteria throughout the north temperate‐subarctic regions.  相似文献   
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中国西北干旱区蒸散发时空动态特征   总被引:21,自引:9,他引:12  
邓兴耀  刘洋  刘志辉  姚俊强 《生态学报》2017,37(9):2994-3008
利用MODIS ET数据集中2000—2014年的地表实际蒸散发量产品,运用变异系数、Theil-Sen median趋势分析与MannKendall检验和Hurst指数法,研究了中国西北干旱区蒸散发的空间格局、不同维度的空间异质性和时间变化特征及未来趋势预测。结果表明:(1)2000—2014年全区蒸散发量总体较小,蒸散发量小于200 mm的区域占总面积的38.329%。在空间上ET自山区向两侧平原减少,不同土地覆盖的ET大小为:林地农用地草地稀疏植被。受降水和土地覆盖的综合影响,ET的高值区(400 mm)主要在降水丰富的山区林地和草地,而低值区(200 mm)主要在降水较少的平原稀疏植被区和草地。(2)近15年全区蒸散发变异程度不明显,以相对较低的波动变化为主。各亚区内波动较低区域的比例为:北疆天山祁连山内蒙西部河西走廊南疆。(3)15年间全区年均蒸散发量呈波动变化,总体有微弱的减小趋势,变化率为-0.9348 mm/a。基于像元尺度的分析也表明全区ET以减小的变化趋势为主,但各亚区的减小程度各异:天山内蒙西部河西走廊北疆祁连山,仅南疆有增加趋势。(4)全区ET的Hurst指数均值为0.689,Hurst指数大于0.5的范围所占比例为80.033%,未来全区蒸散发的变化趋势以持续性减小为主。其中22.003%区域的变化趋势无法确定。未来各亚区ET的减少趋势为:内蒙西部天山河西走廊北疆祁连山南疆。  相似文献   
6.
Temperature and nutrient availability play key roles in controlling the pathways and rates at which energy and materials move through ecosystems. These factors have also changed dramatically on Earth over the past century as human activities have intensified. Although significant effort has been devoted to understanding the role of temperature and nutrients in isolation, less is known about how these two factors interact to influence ecological processes. Recent advances in ecological stoichiometry and metabolic ecology provide a useful framework for making progress in this area, but conceptual synthesis and review are needed to help catalyze additional research. Here, we examine known and potential interactions between temperature and nutrients from a variety of physiological, community, and ecosystem perspectives. We first review patterns at the level of the individual, focusing on four traits – growth, respiration, body size, and elemental content – that should theoretically govern how temperature and nutrients interact to influence higher levels of biological organization. We next explore the interactive effects of temperature and nutrients on populations, communities, and food webs by synthesizing information related to community size spectra, biomass distributions, and elemental composition. We use metabolic theory to make predictions about how population‐level secondary production should respond to interactions between temperature and resource supply, setting up qualitative predictions about the flows of energy and materials through metazoan food webs. Last, we examine how temperature–nutrient interactions influence processes at the whole‐ecosystem level, focusing on apparent vs. intrinsic activation energies of ecosystem processes, how to represent temperature–nutrient interactions in ecosystem models, and patterns with respect to nutrient uptake and organic matter decomposition. We conclude that a better understanding of interactions between temperature and nutrients will be critical for developing realistic predictions about ecological responses to multiple, simultaneous drivers of global change, including climate warming and elevated nutrient supply.  相似文献   
7.
Climate extremes, such as drought, may have immediate and potentially prolonged effects on carbon cycling. Grasslands store approximately one‐third of all terrestrial carbon and may become carbon sources during droughts. However, the magnitude and duration of drought‐induced disruptions to the carbon cycle, as well as the mechanisms responsible, remain poorly understood. Over the next century, global climate models predict an increase in two types of drought: chronic but subtle ‘press‐droughts’, and shorter term but extreme ‘pulse‐droughts’. Much of our current understanding of the ecological impacts of drought comes from experimental rainfall manipulations. These studies have been highly valuable, but are often short term and rarely quantify carbon feedbacks. To address this knowledge gap, we used the Community Land Model 4.0 to examine the individual and interactive effects of pulse‐ and press‐droughts on carbon cycling in a mesic grassland of the US Great Plains. A series of modeling experiments were imposed by varying drought magnitude (precipitation amount) and interannual pattern (press‐ vs. pulse‐droughts) to examine the effects on carbon storage and cycling at annual to century timescales. We present three main findings. First, a single‐year pulse‐drought had immediate and prolonged effects on carbon storage due to differential sensitivities of ecosystem respiration and gross primary production. Second, short‐term pulse‐droughts caused greater carbon loss than chronic press‐droughts when total precipitation reductions over a 20‐year period were equivalent. Third, combining pulse‐ and press‐droughts had intermediate effects on carbon loss compared to the independent drought types, except at high drought levels. Overall, these results suggest that interannual drought pattern may be as important for carbon dynamics as drought magnitude and that extreme droughts may have long‐lasting carbon feedbacks in grassland ecosystems.  相似文献   
8.
The most common approach to predicting how species ranges and ecological functions will shift with climate change is to construct correlative species distribution models (SDMs). These models use a species’ climatic distribution to determine currently suitable areas for the species and project its potential distribution under future climate scenarios. A core, rarely tested, assumption of SDMs is that all populations will respond equivalently to climate. Few studies have examined this assumption, and those that have rarely dissect the reasons for intraspecific differences. Focusing on the arctic-alpine cushion plant Silene acaulis, we compared predictive accuracy from SDMs constructed using the species’ full global distribution with composite predictions from separate SDMs constructed using subpopulations defined either by genetic or habitat differences. This is one of the first studies to compare multiple ways of constructing intraspecific-level SDMs with a species-level SDM. We also examine the contested relationship between relative probability of occurrence and species performance or ecological function, testing if SDM output can predict individual performance (plant size) and biotic interactions (facilitation). We found that both genetic- and habitat-informed SDMs are considerably more accurate than a species-level SDM, and that the genetic model substantially differs from and outperforms the habitat model. While SDMs have been used to infer population performance and possibly even biotic interactions, in our system these relationships were extremely weak. Our results indicate that individual subpopulations may respond differently to climate, although we discuss and explore several alternative explanations for the superior performance of intraspecific-level SDMs. We emphasize the need to carefully examine how to best define intraspecific-level SDMs as well as how potential genetic, environmental, or sampling variation within species ranges can critically affect SDM predictions. We urge caution in inferring population performance or biotic interactions from SDM predictions, as these often-assumed relationships are not supported in our study.  相似文献   
9.
气候变化和人类活动是对陆地生态系统碳循环产生重要影响的两个因素,定量评估气候变化与人类活动对植被净初级生产力(NPP)的相对影响,对深入理解其驱动机制和控制荒漠化发展具有重要意义。以疏勒河流域为研究区,利用遥感和气象数据计算潜在NPP(PNPP)及其与实际NPP(ANPP)之间的差值,分别衡量了气候变化和人类活动对流域NPP的相对影响。研究结果表明:(1)2001—2015年疏勒河流域年ANPP整体呈缓慢增加趋势,与全国和西北地区相比,普遍较低,流域植被整体生产力水平不高。流域年ANPP空间分布呈现上游祁连山区和中下游绿洲区ANPP较高,而中下游荒漠戈壁区ANPP较低的分布格局。(2)2001—2015年流域年PNPP的变化趋势表明,降水量的变化是导致疏勒河流域植被退化加剧或缓解的主要气候驱动因素,但气温的变化对植被的影响较为复杂。(3)2001—2015年流域大部分地区植被退化系人类活动造成的,但人类活动的负向影响力在减弱。(4)气候变化和人类活动对植被NPP的相对影响均表现出明显的空间异质性,其中人类活动是疏勒河流域植被变化的主要驱动因素。  相似文献   
10.
Forecasting the growth of tree species to future environmental changes requires a better understanding of its determinants. Tree growth is known to respond to global‐change drivers such as climate change or atmospheric deposition, as well as to local land‐use drivers such as forest management. Yet, large geographical scale studies examining interactive growth responses to multiple global‐change drivers are relatively scarce and rarely consider management effects. Here, we assessed the interactive effects of three global‐change drivers (temperature, precipitation and nitrogen deposition) on individual tree growth of three study species (Quercus robur/petraea, Fagus sylvatica and Fraxinus excelsior). We sampled trees along spatial environmental gradients across Europe and accounted for the effects of management for Quercus. We collected increment cores from 267 trees distributed over 151 plots in 19 forest regions and characterized their neighbouring environment to take into account potentially confounding factors such as tree size, competition, soil conditions and elevation. We demonstrate that growth responds interactively to global‐change drivers, with species‐specific sensitivities to the combined factors. Simultaneously high levels of precipitation and deposition benefited Fraxinus, but negatively affected Quercus’ growth, highlighting species‐specific interactive tree growth responses to combined drivers. For Fagus, a stronger growth response to higher temperatures was found when precipitation was also higher, illustrating the potential negative effects of drought stress under warming for this species. Furthermore, we show that past forest management can modulate the effects of changing temperatures on Quercus’ growth; individuals in plots with a coppicing history showed stronger growth responses to higher temperatures. Overall, our findings highlight how tree growth can be interactively determined by global‐change drivers, and how these growth responses might be modulated by past forest management. By showing future growth changes for scenarios of environmental change, we stress the importance of considering multiple drivers, including past management and their interactions, when predicting tree growth.  相似文献   
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