中国雪灾时空变化及畜牧业脆弱性分析

以省级报刊为主要信息源,辅以气象部门统计资料,获取了县域统计单元的雪灾信息,重建了中国1949～2000年雪灾的时空分布格局。对雪灾的时空变化分析结果表明,中国雪灾存在3个高发中心,即内蒙古中部、新疆天山以北和青藏高原东北部;雪灾年际波动幅度大,总体呈现增长趋势。本文还进一步分析了中国雪灾均灾次的高、低值区与草场退化程度的关系,从承灾体脆弱性的角度揭示了雪灾格局形成的机制。     

九龙江流域大气氮湿沉降研究

通过2004～2005年对位于我国东南沿海的九龙江流域及周边共17个站点的实地观测,运用GIS技术定量揭示了大气氮湿沉降强度和时空分布特征,并利用氮稳定同位素分析雨水硝态氮的主要来源.结果表明,①17个站点雨水总氮平均浓度为(2.20±1.69)～(3.26±1.37) mg·L-1(以N计,下同),铵态氮、硝态氮和有机氮分别占39%、25%和36%;②雨水氮浓度随降雨强度的增大呈降低趋势,旱季浓度明显大于雨季,降水对大气具有清洗作用;③低δ15N值表明雨水硝态氮主要来源于汽车尾气排放、化石燃料燃烧和化肥施用;④九龙江流域大气氮湿沉降量平均9.9 kg·hm-2,春夏2季约占全年的91%,大气氮湿沉降占沉降总量的66%,揭示了该地区1∶2的大气氮干湿沉降结构.大气氮湿沉降时空差异与降雨量和氮的排放直接相关.     

西江河口段秋季表层水体CO2分压的变化特征

为了探讨西江河口段表层水体CO2分压(pco2)的分布特征,于2006年秋季在西江磨刀门至马口河段沿程实测了58个样点的表层水体理化参数.结果表明,河道表层水体Pco2值介于93.15-334.38Pa之间,平均值为174.00Pa,被测河段是个明显的大气CO2"源".河流水体的理化性质在向海输送过程中发生了明显的改变,并且导致表层水体Pco2随航程的增加而递减.样点水体接受的日照时间与其Pco2,有负相关关系,使得表层水体Pco2呈现出日周期变化.河段表层水体Pco2的这种时空变化与河口过程中河-海作用的弱化而引起水体理化参数(如水温、pH值、电导率、总溶解固体、氧化还原电位和碱度等)的变化以及水体内部碳的生物化学过程(如光合作用与呼吸作用以及有机物的分解转化等)密切相关.     

近45a宁夏气温、降水及植被指数的变化分析

利用1961~2005年宁夏气温、降水资料,并结合1982~2003年植被指数(NDVI)数据,分析了宁夏气温、降水和NDVI的时空变化特征。结果表明:近45a来,宁夏气温明显升高,降水总体呈减少趋势;冬季和引黄灌区升温最明显,冬季降水增加,其它季节及各地区降水减少,其中秋季和宁夏南部山区减少最明显;秋冬季降水在1968年前后发生了突变,突变后,冬季降水增多,秋季降水减少;1985~1996年间发生了气温突变,突变后各季及各地区气温明显升高,冬春季和引黄灌区降水增多,其它季节和地区降水减少,极端气候事件较突变前发生更为频繁;近20a宁夏区域内NDVI值呈增加趋势,荒漠化面积整体得到控制。进一步分析表明,前一年气温偏高、夏季降水增加时,有利于当年NDVI值增加。     

Differences in sensory ecology contribute to resource partitioning in the bats Myotis bechsteinii and Myotis nattereri (Chiroptera: Vespertilionidae)

Coexisting animal species frequently differ in resource use in at least one niche dimension and thus avoid competition. While a range of morphological differences that lead to differentiation in animals' mechanical access to food have been identified, the role of sensory differences in within-guild niche differentiation has received less attention. We tested the hypothesis that differences in sensory access to prey contribute to resource partitioning between potentially competing species using two sympatric, similar-sized, congeneric bat species as a model system. Nursery colonies of Natterer's bat (Myotis nattereri) and Bechstein's bat (Myotis bechsteinii) roost in bat boxes in the same orchard and forage in forests and orchards nearby. In observations and behavioural experiments with freshly captured M. bechsteinii, we showed that individuals are able to hunt using prey-generated sound alone. In contrast, M. nattereri rarely uses prey-generated sound, but instead is able to find prey by echolocation very close to vegetation. In accordance with these behavioural data, we showed that M. bechsteinii has significantly larger ears than M. nattereri, providing it with superior detection and localization abilities for relatively low-frequency prey rustling sounds. We hypothesized that these differences in sensory ecology of the two syntopic, congeneric species would contribute to resource partitioning, so that M. bechsteinii would find more noisy prey taxa, possibly hidden in vegetation, by listening for prey sounds, while M. nattereri would have better access to still prey using echolocation or associative learning. Analysis of faecal samples collected on the same nights from bat boxes occupied by each species corroborated this prediction. The diets of the two species differed significantly, reflecting their different prey perception techniques and thereby supporting the hypothesis that differences in sensory ecology contribute to niche differentiation. Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users. B.M. Siemers and S.M. Swift contributed equally to this work.     

利用RAPD标记分析卧龙自然保护区不同海拔沙棘种群的遗传变异

从1800m到3400m五个海拔连续取样,用RAPD分子标记研究了卧龙自然保护区中国沙棘种群的遗传结构和遗传变异.用11条寡核苷酸引物,扩增得到151个重复性好的位点,其中143个多态位点,多态率达94.7%.在5个沙棘种群中,总遗传多样性值(HT)为0.289,B种群内的遗传多样性值为0.315,这完全符合沙棘这种多年生、远交的木本植物高遗传变异的特性.5个种群内遗传多样性随海拔升高呈低—高—低变异趋势,在2200m海拔处的B种群遗传多样性达最大值0.315,3400m海拔处的E种群则表现最小,仅0.098.5个种群间的遗传分化值GST=0.406,也即是说有40.6%的遗传变异存在于种群间,59.4%存在种群内.1800m海拔处的A种群与其他种群的明显分离是造成种群间遗传分化大的原因.UPGMA聚类图和PCoA散点图分别进一步确证了5个种群间关系和所有个体间的关系.最后,经过Mantel检测,遗传距离与海拔表现了明显的相关性(r=0.646,P=0.011).     

Quality and Congestion in Environmental Goods: The Road to the Wangapeka

An increasing complaint heard among New Zealand residents is that their enjoyment of local environmental resources is being diminished by increased congestion from foreign visitors. This paper considers a model of vertical differentiation in which foreign high-value and domestic low-value consumers incur congestion costs in using a common resource. We demonstrate that reducing quality in the face of increased foreign demand is optimal absent discriminatory prices (but not otherwise). We also consider the provision of multiple environmental goods and demonstrate that providing differential qualities may be optimal even if domestic consumers do not use the high-quality resources at all.     

Endocrine disrupters in the aquatic environment

Possible mechanisms to explain endocrine effects on reproduction and sex differentiation are presented for selected pharmaceuticals, agrochemicals, industrial chemicals and plant sterols which are known to be present in the aquatic environment. Disruptions of the hormonal coordination can be induced by xenobiotics on various levels of the hierachically organised endocrine system of vertebrates. Phthalate plasticisers, for example, may disrupt the pituitary control of gonadal functions; prenatal/larval exposure to synthetic estrogen impairs sex differentiation and neuroendocrine sexual determination of the central nervous system; phenylurea herbicides block the androgen receptor; the biotransformation of weakly estrogenic plant sterol components of paper mill wastewater (e.g. βsitosterol) may lead to androgenic compounds. The effect of hypolipidemic drugs on lipid homeostasis (peroxysom proliferation) is transmitted via a receptor protein that seems to be closely related to the endocrine system both functionally as well as phylogenetically; possible interferences with the neuroendocrine control of sex differentiation are also discussed. In invertebrates, tributyltin is known to effect the biosynthesis of steroidal sexual hormones. PCBs are suspected to be competitive inhibitors of the steroid catabolism. In order to identify potential risks caused by chemicals to the reproductive capacities of aquatic animals and to the quality of drinking water, methods should be established to detect endocrine disrupters at the various levels of the endocrine system.     

全球CO2倍增对我国自然地域分异及农业生产潜力的影响预测

ＣＯ_２倍增导致全球变暖,并对自然环境产生影响的研究已成为举世瞩目的重大课题。本文在ＩＰＣＣ预告的基础上,分析了气候变化对我国自然地域分异的影响,用６７１个站点资料分析了我国温度带及各自然地区的数量指标、各地区生产潜力及影响生产潜力的因子,将气候变暖增温、温度带北移的界线及降水区向西迁移后干湿地区界线的变化绘制成图,同时预测了农业生产潜力的未来变化。结果表明：全球变暖使我国温暖地区面积增加,半干旱及干旱区水分条件改善,有利于作物生产。     

水电工程干扰下澜沧江典型段的水温时空特征

以澜沧江流域漫湾库尾至大朝山坝下的水电工程干扰典型段为研究区域,利用1978～2005年建坝前后的水温实测资料,采用相关分析、线性回归的方法分析表层水温、下泄水温的时空分布特征.结果表明,水电工程建设后库区蓄水对表层水温有着明显的增温效应,坝前表层水温仅5～8月低于气温,其余所有月份坝前表层水温均高于建坝前的天然表层水温,时间分异性减弱.库区出水温度一般冬季(干季)高于气温和天然表层水温,而夏季(雨季)则相反,与天然水温和气温的变化趋势有2个月的滞后性.从库尾到坝前,表层水温与天然气温逐渐接近,水温/气温比与距离大坝距离之间存在正相关关系,漫湾库区下泄水对大朝山库区的水温具有一定的累积效应.本研究结果表明水电工程对澜沧江典型河段的水温时空分布存在显著效应.