Modeling the Effects of Anthropogenic Habitat Change on Savanna Snake Invasions into African Rainforest

Abstract:  We used a species-distribution modeling approach, ground-based climate data sets, and newly available remote-sensing data on vegetation from the MODIS and Quick Scatterometer sensors to investigate the combined effects of human-caused habitat alterations and climate on potential invasions of rainforest by 3 savanna snake species in Cameroon, Central Africa: the night adder (Causus maculatus) , olympic lined snake (Dromophis lineatus) , and African house snake (Lamprophis fuliginosus) . Models with contemporary climate variables and localities from native savanna habitats showed that the current climate in undisturbed rainforest was unsuitable for any of the snake species due to high precipitation. Limited availability of thermally suitable nest sites and mismatches between important life-history events and prey availability are a likely explanation for the predicted exclusion from undisturbed rainforest. Models with only MODIS-derived vegetation variables and savanna localities predicted invasion in disturbed areas within the rainforest zone, which suggests that human removal of forest cover creates suitable microhabitats that facilitate invasions into rainforest. Models with a combination of contemporary climate, MODIS- and Quick Scatterometer-derived vegetation variables, and forest and savanna localities predicted extensive invasion into rainforest caused by rainforest loss. In contrast, a projection of the present-day species-climate envelope on future climate suggested a reduction in invasion potential within the rainforest zone as a consequence of predicted increases in precipitation. These results emphasize that the combined responses of deforestation and climate change will likely be complex in tropical rainforest systems.     

Effects of Weed-Management Burning on Reptile Assemblages in Australian Tropical Savannas

Abstract: Fire is frequently used for land management purposes and may be crucial for effective control of invasive non‐native plants. Nevertheless, fire modifies environments and may affect nontarget native biodiversity, which can cause conflicts for conservation managers. Native Australian reptiles avoid habitat invaded by the alien plant rubber vine (Cryptostegia grandiflora) and may be susceptible to the impacts of burning, a situation that provides a model system in which to examine possible conservation trade‐offs between managing invasive plants and maintaining native biodiversity. We used replicated, experimental fire treatments (unburned, dry‐season burned, and wet‐season burned) in 2 habitats (riparian and adjacent open woodland) to examine the short‐ (within 12 months of fire) and longer‐term (within 3 years of fire) changes of reptile assemblages in response to wet‐ and dry‐season burning for weed management in tropical savannas of northern Australia. Within 12 months of fire, abundances of the skink Carlia munda (Scincidae) were higher in the burned sites, but overall reptile composition was structured by habitat type rather than by effects of burning. Within 3 years of a fire, the effects of fire were evident. Reptiles, especially the gecko Heteronotia binoei (Gekkonidae), were least abundant in dry‐season burned sites; litter‐associated species, including Carlia pectoralis (Scincidae), were rarely observed in burned habitat; and there were fewer species in the wet‐season burned sites. Reptile abundance was associated with vegetation structure, which suggests that fire‐induced changes detrimentally altered the availability of resources for some reptiles, particularly leaf‐litter species. Invasive alien plants, such as rubber vine, have severe effects on native biodiversity, and control of such species is a fundamental land management objective. Nevertheless, fire management of invasive alien plants may adversely affect native biodiversity, creating a conservation conundrum. In such scenarios, land managers will need to identify the most desired conservation goal and consider the consequences for native biota.     

Storm flow export of metolachlor from a coastal plain watershed

Abstract

During an 18‐month (1994–1995) survey of the surface water in an Atlantic Coastal Plain watershed, metolachlor was most frequently detected during storm flow events. Therefore, a sampling procedure, focused on storm flow, was implemented in June of 1996. During 1996, three tropical cyclones made landfall within 150 km of the watershed. These storms, as well as several summer thunderstorms, produced six distinct storm flow events within the watershed. Metolachlor was detected leaving the watershed during each event. In early September, Hurricane Fran produced the largest storm flow event and accounted for the majority of the metolachlor exports. During the storm event triggered by Hurricane Fran, the highest daily average flow (7.5 m² s^‐1) and highest concentration (5.1 μg L^‐1) ever measured at the watershed outlet were recorded. Storm flow exports leaving the watershed represented 0.1 g ha^‐1 or about 0.04% of active ingredient applied.     

基于对象的高分辨率遥感图像滑坡检测方法

滑坡遥感检测对于灾害调查和制图具有重要意义,面向对象是高分辨率遥感图像信息提取的重要思路。以高植被覆盖的热带雨林地区为例,在对试验区滑坡遥感图像特征进行分析的基础上,提出了基于对象的高分辨率遥感图像滑坡检测方法。通过多期遥感图像的多尺度、多层次分割,确定了图像对象变化检测的基本单元,构建了滑坡检测多级对象层次网络;依靠图像对象特征、上下文关系和拓扑关系等,构建了适于该实验区的滑坡检测知识规则,从而将滑坡检测整个过程包含在图像对象分析之中,并最后实现了高分辨率遥感图像的滑坡检测。实例证明,基于对象的滑坡检测方法适于热带雨林地区的信息提取,这对于其它地理环境类似地区的灾害调查与制图工作具有一定的参考价值。     

Economic costs of extratropical storms under climate change: an application of FUND

Extratropical cyclones have attracted some attention in climate policy circles as a possible significant damage factor of climate change. This study conducts an assessment of economic impacts of increased storm activities under climate change with the integrated assessment model FUND 3.5. In the base case, the direct economic damage of enhanced storms due to climate change amounts to US$2.8 billion globally (approximately 38% of the total economic loss of storms at present) at the year 2100, while its ratio to the world GDP is 0.0009%. The paper also shows various sensitivity runs exhibiting up to 3 times the level of damage relative to the base run.     

我国的主要气象灾害及其经济损失

自然灾害一直伴随着人类社会的生产、生活与发展,气象灾害尤甚,它们给人类社会造成的经济损失十分巨大。根据中国气象局资料统计,在各类自然灾害中,气象灾害大约占到70%以上。我国每年重大气象灾害影响的人口大约达4亿人次,所造成的经济损失大约占到国民生产总值的1%~3%。近半个世纪以来,发生在我国的重大气象灾害,受灾人口常高达数亿人次,造成的直接经济损失高达数千亿元。为此,对包括热带气旋、干旱、洪涝、低温冷冻和雪灾等我国的主要气象灾害及其经济损失的总体概况,进行了总结和归纳,可作为了解和认识我国气象灾害及其经济与社会影响的参考依据。     

Ecological metrics of biomass removed by three methods of purse-seine fishing for tunas in the eastern tropical Pacific Ocean

An ecosystem approach to fisheries management is a widely recognized goal, but describing and measuring the effects of a fishery on an ecosystem is difficult. Ecological information on the entire catch (all animals removed, whether retained or discarded) of both species targeted by the fishery and nontarget species (i.e., bycatch) is required. We used data from the well-documented purse-seine fishery for tunas (Thunnus albacares, T. obesus, and Katsuwonus pelamis) in the eastern tropical Pacific Ocean to examine the fishery's ecological effects. Purse-seine fishing in the eastern tropical Pacific is conducted in 3 ways that differ in the amount and composition of target species and bycatch. The choice of method depends on whether the tunas are swimming alone (unassociated sets), associated with dolphins (dolphin sets), or associated with floating objects (floating-object sets). Among the fishing methods, we compared catch on the basis of weight, number of individuals, trophic level, replacement time, and diversity. Floating-object sets removed 2-3 times as much biomass as the other 2 methods, depending on how removal was measured. Results of previous studies suggest the ecological effects of floating-object sets are thousands of times greater than the effects of other methods, but these results were derived from only numbers of discarded animals. Management of the fishery has been driven to a substantial extent by a focus on reducing bycatch, although discards are currently 4.8% of total catch by weight, compared with global averages of 7.5% for tuna longline fishing and 30.0% for midwater trawling. An ecosystem approach to fisheries management requires that ecological effects of fishing on all animals removed by a fishery, not just bycatch or discarded catch, be measured with a variety of metrics.     

不同施肥模式对热区晚稻水田CH4和N2O排放的影响

由于农田温室气体排放的原位观测主要集中于温带和亚热带地区,热带地区农田土壤温室气体的排放往往被忽视.研究不同施肥模式下海南稻田温室气体排放特征对于准确评估我国农田土壤CH_4和N_2O排放及制定相应的减排措施有重要意义.本研究设置5个处理:空白对照(CK)、常规施肥(CON)、优化施肥(YH)、优化施肥与缓控释肥配施(ZYH1)、优化施肥、缓控释肥和有机肥三者配施(ZYH2),采用静态箱-气相色谱法,通过田间小区试验研究晚稻生长季CH_4和N_2O排放动态特征,并估算全球增温潜势(GWP)以及温室气体排放强度(GHGI).结果表明,CK、CON、YH、ZYH1和ZYH2处理的CH_4晚稻生长季累计排放量分别为175. 70、60. 30、63. 00、62. 80和56. 60 kg·hm~(-2),相应处理的N2O晚稻生长季累积排放量分别为0. 78、3. 40、1. 03、1. 44和0. 44 kg·hm~(-2). ZYH2的产量较CK、CON、YH和ZYH1分别提高了29. 69%、11. 81%、6. 74%和10. 36%,GWP较CK、CON、YH和ZYH1分别降低了64. 80%、43. 23%、12. 93%和15. 15%,同时,GHGI分别降低了76. 49%、52. 52%、20. 54%和23. 87%.相关分析结果表明:土壤温度和Eh是驱动CH_4排放变化的主要因素.综合产量及温室气体减排效果而言,优化施肥+羊粪有机肥+缓控释肥处理(ZYH2)是当地值得推广的减肥模式.     

增江流域河流颗粒有机碳的来源、含量变化及输出通量

对华南增江径流进行了 1个水文年度的 1 5次等时段采样 ,分析了河流悬移质中主要生源元素 (C、N、H)的含量 ,并估算了不同物源的贡献 .结果表明 ,增江悬移质中的有机碳以水生藻类的贡献为主 ,土壤侵蚀来源的有机碳在悬移质粗粒组中的份额平均为 37 2 4 % ,在细粒组中仅占 1 1 1 1 % 增江流域颗粒有机碳的输出通量为 0 83× 1 0 6g·km-2 ·a-1 ,其中来自土壤的颗粒有机碳通量为 0 2 2× 1 0 6g·km-2 ·a-1 .     

西双版纳热带森林挥发性有机物的观测研究

2002年7月中旬利用异戊二烯通量测定系统对云南西双版纳热带森林异戊二烯的排放通量进行了连续测量,同时对光合有效辐射(PAR)、气温、湿度、风等参数进行了观测.结果表明,热带地区人工橡胶林区域湿季异戊二烯的排放有明显的日变化规律,中午前后为一天中的最大值,异戊二烯排放通量的日平均值在0.85～0.24mgC/(m²h)之间.对小时值和日平均值而言,异戊二烯的排放与PAR和气温的变化规律比较一致,但它对PAR比对气温更加敏感.不同的天气状况对异戊二烯的排放有非常明显的影响.橡胶林是一个单萜烯排放者,其单萜烯的排放速率明显依赖于PAR.橡胶林和热带雨林冠层上空异戊二烯和单萜烯的浓度也有明显的日变化规律,而且橡胶林区域的异戊二烯和单萜烯的浓度均明显高于热带雨林.