Many nature reserves are established to protect the habitat needs of particular endangered species of interest but their effectiveness for protecting other species is questionable.In this study,this effectiveness was ...Many nature reserves are established to protect the habitat needs of particular endangered species of interest but their effectiveness for protecting other species is questionable.In this study,this effectiveness was evaluated in a nature reserve network located in the Qinling Mountains,Shaanxi Province,China.The network of reserves was established mainly for the conservation of the giant panda,a species considered as a surrogate for the conservation of many other endangered species in the region.The habitat suitability of nine protected species,including the giant panda,was modeled by using Maximum Entropy(MAXENT)and their spatial congruence was analyzed.Habitat suitability of these species was also overlapped with nature reserve boundaries and their management zones(i.e.,core,buffer and experimental zones).Results show that in general the habitat of the giant panda constitutes a reasonable surrogate of the habitat of other protected species,and giant panda reserves protect a relatively high proportion of the habitat of other protected species.Therefore,giant panda habitat conservation also allows the conservation of the habitat of other protected species in the region.However,a large area of suitable habitat was excluded from the nature reserve network.In addition,four species exhibited a low proportion of highly suitable habitat inside the core zones of nature reserves.It suggests that a high proportion of suitable habitat of protected species not targeted for conservation is located in the experimental and buffer zones,thus,is being affected by human activities.To increase their conservation effectiveness,nature reserves and their management zones need to be re-examined in order to include suitable habitat of more endangered species.The procedures described in this study can be easily implemented for the conservation of many endangered species not only in China but in many other parts of the world.展开更多
To provide scientific support for planning maize production and designing countermeasures against the effects of climate change on the national maize crop, we analyzed the climatic suitability for cultivating maize ac...To provide scientific support for planning maize production and designing countermeasures against the effects of climate change on the national maize crop, we analyzed the climatic suitability for cultivating maize across China. These analyses were based on annual climate indices at the Chinese national level; these indices influence the geographical distribution of maize cultivation. The annual climate indices, together with geographical information on the current cultivation sites of maize, the maximum entropy (MaxEnt) model, and the ArcGIS spatial analysis technique were used to analyze and predict maize distribution. The results show that the MaxEnt model can be used to study the climatic suitability for maize cultivation. The eight key climatic factors affecting maize cultivation areas were the frost-free period, annual average temperature, ≥0°C accumulated temperature, ≥10°C accumulated temperature continuous days, ≥10°C accumulated temperature, annual precipitation, warmest month average temperature, and humidity index. We classified climatic zones in terms of their suitability for maize cultivation, based on the existence probability determined using the MaxEnt model. Furthermore, climatic thresholds for a potential maize cultivation zone were determined based on the relationship between the dominant climatic factors and the potential maize cultivation area. The results indicated that the importance and thresholds of main climate controls differ for different maize species and maturities, and their specific climatic suitability should be studied further to identify the best cultivation zones. The MaxEnt model is a useful tool to study climatic suitability for maize cultivation.展开更多
东北地区是我国沼泽湿地分布最广泛的地区。为研究沼泽湿地对气候变化的响应,选取了对沼泽湿地分布可能存在影响的26个环境因子,利用最大熵(Maximum Entropy,MaxEnt)模型模拟了沼泽湿地基准气候条件下的潜在分布,并预测了气候变化情景下...东北地区是我国沼泽湿地分布最广泛的地区。为研究沼泽湿地对气候变化的响应,选取了对沼泽湿地分布可能存在影响的26个环境因子,利用最大熵(Maximum Entropy,MaxEnt)模型模拟了沼泽湿地基准气候条件下的潜在分布,并预测了气候变化情景下2011—2040年、2041—2070年和2071—2100年3个研究阶段东北沼泽湿地潜在分布。研究结果表明:最大熵模型预测精度较高(平均AUC(Aera Under Curve)为(0.826±0.005))。基准气候条件下东北沼泽潜在分布区主要为大小兴安岭和三江平原地区。随着时间的推进,东北地区沼泽湿地原有潜在分布面积明显减少,而新增潜在分布面积较少,总面积呈现急剧减少趋势。至2071—2100年,原有沼泽湿地潜在分布面积将减少99.80%,新增潜在分布面积仅2.48%,总潜在分布面积减少97.32%。空间分布上,东北沼泽湿地潜在分布呈现由东向西迁移,南北向中心收缩的趋势。研究结果可为东北地区沼泽湿地保护政策的制定提供参考。展开更多
The spatial interaction model is an effective way to explore the geographical disparities inherent in the Belt and Road Initiative(BRI) by simulating spatial flows. The traditional gravity model implies the hypothesis...The spatial interaction model is an effective way to explore the geographical disparities inherent in the Belt and Road Initiative(BRI) by simulating spatial flows. The traditional gravity model implies the hypothesis of equilibrium points without any reference to when or how to achieve it. In this paper, a dynamic gravity model was established based on the Maximum Entropy(MaxEnt) theory to estimate and monitor the interconnection intensity and dynamic characters of bilateral relations. In order to detect the determinants of interconnection intensity, a Geodetector method was applied to identify and evaluate the determinants of spatial networks in five dimensions. The empirical study clearly demonstrates a heterogeneous and non-circular spatial structure. The main driving forces of spatial-temporal evolution are foreign direct investment, tourism and railway infrastructure construction, while determinants in different sub-regions show obvious spatial differentiation. Southeast Asian countries are typically multi-island area where aviation infrastructure plays a more important role. North and Central Asian countries regard oil as a pillar industry where power and port facilities have a greater impact on the interconnection. While Western Asian countries are mostly influenced by the railway infrastructure, Eastern European countries already have relatively robust infrastructure where tariff policies provide a greater impetus.展开更多
准确提取城市不透水面对生态环境、水热循环及热岛效应等研究具有重要意义。该文利用WorldView高分辨遥感影像,提出基于PUL(Positive and Unlabeled Learning)算法的高分辨率影像城市不透水面提取方法,该方法不需要负样本数据,只需少量...准确提取城市不透水面对生态环境、水热循环及热岛效应等研究具有重要意义。该文利用WorldView高分辨遥感影像,提出基于PUL(Positive and Unlabeled Learning)算法的高分辨率影像城市不透水面提取方法,该方法不需要负样本数据,只需少量的正样本和未标记样本即可训练分类模型。结果显示,PUL算法的提取结果优于一类支持向量机(OCSVM)以及最大熵(MAXENT)模型。使用不同正样本量时,PUL的提取结果总体精度和kappa系数均优于OCSVM和MAXENT,最高总体精度为91.27%,最高kappa系数可达0.8255,可快速、有效地从高分辨率遥感影像中提取不透水面。展开更多
基金Under the auspices of National Natural Science Foundation of China(No.40901289)Major State Basic Research Development Program of China(No.2009CB421104),U.S.National Science Foundation
文摘Many nature reserves are established to protect the habitat needs of particular endangered species of interest but their effectiveness for protecting other species is questionable.In this study,this effectiveness was evaluated in a nature reserve network located in the Qinling Mountains,Shaanxi Province,China.The network of reserves was established mainly for the conservation of the giant panda,a species considered as a surrogate for the conservation of many other endangered species in the region.The habitat suitability of nine protected species,including the giant panda,was modeled by using Maximum Entropy(MAXENT)and their spatial congruence was analyzed.Habitat suitability of these species was also overlapped with nature reserve boundaries and their management zones(i.e.,core,buffer and experimental zones).Results show that in general the habitat of the giant panda constitutes a reasonable surrogate of the habitat of other protected species,and giant panda reserves protect a relatively high proportion of the habitat of other protected species.Therefore,giant panda habitat conservation also allows the conservation of the habitat of other protected species in the region.However,a large area of suitable habitat was excluded from the nature reserve network.In addition,four species exhibited a low proportion of highly suitable habitat inside the core zones of nature reserves.It suggests that a high proportion of suitable habitat of protected species not targeted for conservation is located in the experimental and buffer zones,thus,is being affected by human activities.To increase their conservation effectiveness,nature reserves and their management zones need to be re-examined in order to include suitable habitat of more endangered species.The procedures described in this study can be easily implemented for the conservation of many endangered species not only in China but in many other parts of the world.
基金supported by the National Basic Research Program of China(2010CB951303)the Special Fund for Agro-scientific Research in the Public Interest(200903003)the Basic Operation Cost of China Meteorological Administration(CMA)
文摘To provide scientific support for planning maize production and designing countermeasures against the effects of climate change on the national maize crop, we analyzed the climatic suitability for cultivating maize across China. These analyses were based on annual climate indices at the Chinese national level; these indices influence the geographical distribution of maize cultivation. The annual climate indices, together with geographical information on the current cultivation sites of maize, the maximum entropy (MaxEnt) model, and the ArcGIS spatial analysis technique were used to analyze and predict maize distribution. The results show that the MaxEnt model can be used to study the climatic suitability for maize cultivation. The eight key climatic factors affecting maize cultivation areas were the frost-free period, annual average temperature, ≥0°C accumulated temperature, ≥10°C accumulated temperature continuous days, ≥10°C accumulated temperature, annual precipitation, warmest month average temperature, and humidity index. We classified climatic zones in terms of their suitability for maize cultivation, based on the existence probability determined using the MaxEnt model. Furthermore, climatic thresholds for a potential maize cultivation zone were determined based on the relationship between the dominant climatic factors and the potential maize cultivation area. The results indicated that the importance and thresholds of main climate controls differ for different maize species and maturities, and their specific climatic suitability should be studied further to identify the best cultivation zones. The MaxEnt model is a useful tool to study climatic suitability for maize cultivation.
文摘东北地区是我国沼泽湿地分布最广泛的地区。为研究沼泽湿地对气候变化的响应,选取了对沼泽湿地分布可能存在影响的26个环境因子,利用最大熵(Maximum Entropy,MaxEnt)模型模拟了沼泽湿地基准气候条件下的潜在分布,并预测了气候变化情景下2011—2040年、2041—2070年和2071—2100年3个研究阶段东北沼泽湿地潜在分布。研究结果表明:最大熵模型预测精度较高(平均AUC(Aera Under Curve)为(0.826±0.005))。基准气候条件下东北沼泽潜在分布区主要为大小兴安岭和三江平原地区。随着时间的推进,东北地区沼泽湿地原有潜在分布面积明显减少,而新增潜在分布面积较少,总面积呈现急剧减少趋势。至2071—2100年,原有沼泽湿地潜在分布面积将减少99.80%,新增潜在分布面积仅2.48%,总潜在分布面积减少97.32%。空间分布上,东北沼泽湿地潜在分布呈现由东向西迁移,南北向中心收缩的趋势。研究结果可为东北地区沼泽湿地保护政策的制定提供参考。
基金the auspices of A Category of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA20010101)。
文摘The spatial interaction model is an effective way to explore the geographical disparities inherent in the Belt and Road Initiative(BRI) by simulating spatial flows. The traditional gravity model implies the hypothesis of equilibrium points without any reference to when or how to achieve it. In this paper, a dynamic gravity model was established based on the Maximum Entropy(MaxEnt) theory to estimate and monitor the interconnection intensity and dynamic characters of bilateral relations. In order to detect the determinants of interconnection intensity, a Geodetector method was applied to identify and evaluate the determinants of spatial networks in five dimensions. The empirical study clearly demonstrates a heterogeneous and non-circular spatial structure. The main driving forces of spatial-temporal evolution are foreign direct investment, tourism and railway infrastructure construction, while determinants in different sub-regions show obvious spatial differentiation. Southeast Asian countries are typically multi-island area where aviation infrastructure plays a more important role. North and Central Asian countries regard oil as a pillar industry where power and port facilities have a greater impact on the interconnection. While Western Asian countries are mostly influenced by the railway infrastructure, Eastern European countries already have relatively robust infrastructure where tariff policies provide a greater impetus.
文摘准确提取城市不透水面对生态环境、水热循环及热岛效应等研究具有重要意义。该文利用WorldView高分辨遥感影像,提出基于PUL(Positive and Unlabeled Learning)算法的高分辨率影像城市不透水面提取方法,该方法不需要负样本数据,只需少量的正样本和未标记样本即可训练分类模型。结果显示,PUL算法的提取结果优于一类支持向量机(OCSVM)以及最大熵(MAXENT)模型。使用不同正样本量时,PUL的提取结果总体精度和kappa系数均优于OCSVM和MAXENT,最高总体精度为91.27%,最高kappa系数可达0.8255,可快速、有效地从高分辨率遥感影像中提取不透水面。
文摘湖南省是白颈长尾雉(Syrmaticus ellioti)的主要栖息地之一,分析其潜在适生区对该物种保护具有现实指导意义。本研究综合考虑地形、水源、气候、植被、土地类型以及人为干扰等多项因子,结合有效的白颈长尾雉分布点,利用最大熵(maximum entropy, Maxent)模型预测湖南省白颈长尾雉的适宜栖息地。结果显示, Maxent模型10次重复运行训练集的平均曲线下面积(area under the curve, AUC)值为0.964,预测结果优秀;到县道距离(dis_x)、最暖季度降水量(bio18)、到混交林距离(dis_mxf)和平均气温日较差(bio2)是影响白颈长尾雉适宜栖息地分布的主要因子,到稀树草原距离(dis_sav)、海拔(altitude)和到荒地距离(dis_bar)对其分布的影响也较大,其余因子具有一定影响但并不显著;白颈长尾雉适生区面积为4.76×10^(4)km^(2),主要位于湘西、湘南的山地,但适宜栖息地破碎化程度较高,整体较为分散。
