基于遥感和GIS的青藏铁路生态累积效应研究

采用遥感和GIS技术,通过生态系统功能偏离累积指数、景观格局干扰累积指数、植被退化指数、生态阻隔累积指数和区域生态累积效应指数研究青藏铁路建设和运营对沿线生态系统的累积影响.结果表明,铁路建设和运营对沿线0～1 km直接影响区的生态服务功能、景观格局、植被覆盖和生态流均造成一定的累积影响,但以景观格局和生态流受到的影响最大,且对拉萨至唐古拉段的影响大于唐古拉至格尔木段,主要表现为对农田、草地、河流湿地和荒漠生态系统的影响.从铁路沿线＞1～5和＞5～10 km范围的间接或协同累积影响来看,拉萨至唐古拉段明显高于唐古拉至格尔木段.铁路建设运营对＞1～5 km范围的农田、荒漠和河流湿地生态系统仍存在一定负面影响,且以农田生态系统受到的负面累积影响最大,主要表现为拉萨和格尔木城市扩张对农田生态系统的干扰和占用.     

榆林地区植被时空分异特征及其影响因素研究

植被作为反映陆地生态系统和气候的重要指标,对研究全球或区域生态环境变化具有重要作用.以地处黄土高原生态脆弱区的榆林市为研究区,基于地理探测器模型,选取坡向、坡度、气温、降水和土壤类型5类自然因子,土地利用类型、人口密度和GDP 3类人文因子,分析榆林地区植被空间分异特征及其驱动力,并揭示了促进植被生长影响因子的最适宜特...     

中国生态脆弱区的差异及绿色发展途径分析

受全球气候变化和人类活动的影响,生态脆弱区生态系统持续退化,迫切需要展开生态恢复工程等应对措施,促进人与自然和谐共生、经济发展与生态环境保护协调统一。以往的研究,更倾向于对某一类型生态脆弱区或某一生态脆弱行政区域进行研究。文章旨在从更宏观的角度,基于统计年鉴结果和相关研究报道,梳理和分析主要退化问题和区域绿色发展的需求。在阅读大量国内外相关文献的基础上,选择以中国21个涉及生态脆弱的行政区域为研究对象,对其生态环境状况、环境污染治理投资和生态修复的效率进行综合调查分析。然后,将21个行政区域划分为北方林草农牧交错区、西南石漠化区、西北混合交错区、南方红壤区和青藏高原复合侵蚀区,通过研究5个典型区域的生态脆弱差异和绿色发展情况,明确生态环境脆弱地区绿色发展的合适路径。结果表明,由于水资源的空间分布不均、土地利用规划不协调、地质地形差异大、植被稀疏等原因,造成不同地区的生态脆弱差异性明显,主要表现为南方水蚀和水土流失严重、北方土地沙化和草地退化严重。生态系统的退化阻碍了生态脆弱区实现绿色发展,一方面,植被覆盖率低限制了生态系统抵抗外界干扰的能力,另一方面,投资能力弱使得环境治理的实施力度大大降低。因此,必须结合不同行政区域的生态脆弱情况,提出合适的绿色发展途径。     

塔里木河下游生态输水过程中荒漠河岸林活力恢复监测

根据近5年来对塔里木河下游荒漠河岸林植被的监测数据,分析了生态输水后植物活力的恢复状况.结果显示:应急生态输水增加了塔里木河下游的生物多样性,使原本面临死亡的荒漠河岸植被重新复活,而且不同程度上促进了胡杨群落的自然更新;在近河道50 m的范围内均出现了少量的胡杨、柽柳实生苗,并且在离河道150 m的范围内已经有相当数量的胡杨次生苗,在离河道400 m范围内大约有25%的胡杨均有不同程度的基部新枝萌蘖.通过生态输水后地下水位的逐步抬升,河道两岸的低阶地发育着一定面积的草甸植被,形成了由胡杨、柽柳和草本植物所组成的干旱区非地带性河岸稀疏植被群落,说明应急生态输水对于胡杨为建群种的荒漠河岸林植被的恢复和自然更新产生了积极的影响.     

三江源区植被固定CO2释放O2功能评价

植被在固定CO2释放O2和大气与陆地生态系统碳循环中起着十分重要的作用,是区域和全球环境变化的主要反馈和调节系统,具有重要的生态功能,体现出生态服务价值。根据三江源区多次科考调查及相关资料,计算各种植被类型的净初级生长量,进而根据光合作用方程式、造林成本法、碳税法和工业制氧法估算其固定CO2和释放O2的物质量及其价值量。结果表明:三江源区植被年净初级生长量为8.67×107t·a-1,固定CO21.41×108t·a-1,释放O21.04×108t·a-1。根据造林成本法和碳税法估算出三江源区植被固定CO2的价值为2.8926×1010元·a-1。利用造林成本法和工业制氧法估算出释放O2的价值为3.9157×1010元·a-1。三江源区植被固定CO2释放O2物质量和价值量中,草甸贡献率最高,其次是落叶灌丛、沼泽和草原。本研究对地处青藏高原腹地、生态系统脆弱且空气稀薄的江河源区的生态系统结构和功能的研究具有重要意义。     

排水对沼泽湿地碳通量和碳储量的影响

沼泽湿地是全球重要的碳库,排水是沼泽湿地面临的主要人类活动干扰,排水后水位的改变引起沼泽湿地生态系统过程和功能的变化,进而对碳收支产生影响.基于中国知网和Web of Science数据库检索和筛选65组数据(包括25组CO_2通量、18组CH_4通量和22组碳储量数据),综述国内外排水对沼泽湿地碳通量和碳储量影响的研究.研究发现排水使沼泽湿地CH_4与CO_2通量改变,改变的幅度与湿地生态系统类型、排水时间及排水强度等因素有关.排水后CH_4的排放通量降低了29%-75%. CO_2通量的不同组分响应不同:排水后生态系统呼吸增加了10.9%-120%;总初级生产力的响应有很大的差异,可能升高也可能降低;净初级生产力有变化但不显著;净生态系统生产力多为显著降低,变化幅度为1.8%-290.4%.排水对碳储量的影响更间接,多数研究表明排水后土壤碳储量显著降低,植被碳储量的变化不一致,与湿地类型和排水后的利用方式有关,存在不确定性.已有研究多以某一特定排水时间或排水强度的实验研究为主,未来应加强不同排水强度对碳通量和碳储量的影响研究,研究方法上要将控制实验、野外调查与模型模拟研究相结合,以深入理解排水对湿地生态系统碳收支的影响,为湿地保护和恢复提供理论依据.     

基于GIS的北京市生态脆弱性评价

城市化背景下"社会-自然"耦合生态系统的生态脆弱性评价成为当今研究热点。以GIS为平台,使用SPOT5和Landsat 8 OLI遥感数据等多元数据,运用"敏感、弹性和压力"生态脆弱性评估框架模型,结合空间主成分分析法,计算北京市生态脆弱度(EVI)、生态敏感度(ESI)、生态弹性度(EEI)和生态压力度(EPI),进行生态脆弱性评价。结果表明:(1)北京市生态脆弱性整体程度呈中等水平,但城镇区域生态脆弱性偏高(极高和高度脆弱区面积占北京市总面积的34%),山地林区生态脆弱性较低(一般脆弱区占研究区总面积的11%)。(2)生态脆弱性的敏感度、弹性度和压力度的权重系数分别为0. 196、0. 526和0. 278,平原地区植被覆盖度低和城镇建设用地比例过高是北京市生态脆弱性的主要影响因子。(3) EVI、ESI、EEI和EPI与土地利用方式均呈显著相关,其中EVI与建设用地相关性最大,Pearson相关系数为0. 80。(4)建议北京市生态保护和恢复工作应针对不同区域的脆弱性特征采取相应措施,进行优化实施。     

青藏铁路建设对沿线景观格局的影响

采用遥感和地理信息系统技术,通过对青藏铁路唐古拉山口至拉萨段铁路沿线景观进行分类和制图以及对铁路修建前后景观指数的计算,分析了铁路修建前后景观格局的变化。结果表明铁路建设工程对沿线小范围的景观格局影响较大,对沿线较大范围的景观格局影响较小。     

陕北黄土高原典型人类活动影响下景观生态风险评价

植被恢复促进了景观格局和生态过程的改变,景观生态风险评价有助于揭示人类干预下生态系统结构、功能等在景观尺度产生的潜在不利生态效应。以生态脆弱、人与生态环境的相互作用敏感的陕北黄土高原为典型研究对象,根据2000、2005、2010和2015年夜间遥感地图、植被净初级生产力和土地利用数据,建立景观生态风险指数,对陕北黄土高原的综合风险状况及其变化进行定量评价,并对植被变化、城镇化分别与景观生态风险变化间的相关关系展开分析。结果表明,景观格局变化对生态稳定性有潜在影响,景观生态风险以增长趋势为主,2005—2010年景观生态风险增长的范围最大,涨幅为186.0%,其中,中风险和极高风险等级面积增长超2.7倍;2010—2015年景观生态风险增加有所缓解,增加12.9%;2000—2005年景观生态风险降低26.0%。景观生态风险低等级面积逐渐缩小,其他等级面积逐渐变大。其中,2005年后景观生态风险等级呈片状扩展,主要位于陕北西北部风沙区。植被变化、城镇化分别与景观生态风险值变化之间在西北风沙滩区均呈显著正相关。在景观生态风险增加区植被呈退化趋势;在景观生态风险低值区即退耕还林逐年拓展的区域,植被恢复促进景观生态风险的降低。植被恢复对景观生态风险的影响大于城镇化进程。研究成果对于区域发展和生态恢复的综合调控具有一定参考价值。     

基于土地利用的喀斯特地区生态系统服务功能价值评估——以贵州省为例

为探讨喀斯特地区生态系统服务功能价值特征,对贵州省生态系统服务功能价值进行评估,结果表明生态系统服务功能价值在2005、2010、2020年分别为1 610.43亿、2 357.86亿、4 328.89亿元.贵州省各类生态系统服务功能单价顺序为湿地>水体>森林>草地>农田>荒漠,其中湿地生态系统是荒漠生态系统服务功能价值的149.31倍.2005～2020年贵州省生态服务功能价值结构和土地利用结构以森林生态系统占绝对优势,各类型生态系统服务功能价值顺序为森林>农田>草地>水体>荒漠>湿地,各类型生态系统面积大小顺序为森林>农田>荒漠>草地>水体>湿地.2005、2010、2020年贵州省单位面积生态系统服务功能价值分别为9 142、13 385、24 573元/hm2.根据至2020年的土地利用规划,贵州省生态系统服务功能将持续增加.     

On the behaviour of the residence time at the bottom of the mixed layer

To understand why the findings of Deleersnijder et al. [(2006), Environ Fluid Mech 6: 25–42]—the residence time in the mixed layer in not necessarily zero at the pycnocline—are consistent with those of Delhez and Deleersnijder [(2006), Ocean Dyn 56:139–150]—the residence time in a control domain vanishes at the open boundaries of this control domain—, it is necessary to consider a control domain that includes part of the pycnocline, in which the eddy diffusivity is assumed to be zero. Then, depending on the behaviour of the eddy diffusivity near the bottom of the mixed layer, the residence time may be seen to exhibit a discontinuity at the interface between the mixed layer and the pycnocline. If such a discontinuity exists, the residence time is non-zero in the former and zero in the latter. This is illustrated by analytical solutions obtained under the assumption that the eddy diffusivity is constant in the mixed layer.     

Observations on the function of the glands of the foot of the pediveliger of Ostrea edulis during settlement

The use during settlement of secretions of the 9 different types of gland in the foot of the pediveliger of Ostrea edulis L. was examined experimentally. During settlement, there is a progressive decrease in the crawling speed of the larva and a strengthening of its bond with the substratum. Both changes are related to (a) a change from ciliary to muscular pedal locomotion; (b) the increasing acidity and viscosity of the mucoid secretions used; (c) the secretion of a byssus thread by the glands of the byssus duet; (d) changes in the form and composition of this byssus. At the termination of settlement, the entire contents of 2 types of gland are discharged. Their secretions give rise to the cement which permanently fixes the larva to the substratum. The 9 types of gland are utilised sequentially in a manner closely related to the 6 phases recognised in settlement behaviour.     

刍议医院资产管理的现状及其对策

医院的固定资产和流动资产是医院赖以生存和发展的基础,是一项非经营性国有资产．目前公立医院固定资产、流动资产管理现状不容乐观,针对这种状况,首先分析问题形成的原因,然后提出管理的措施或建议,从而使资产管理工作规范化、制度化、科学化,使有限的卫生资源发挥出最大的社会效益和经济效益．参3．     

豪猪消化系统的解剖研究

为了了解豪猪的消化生理,为豪猪的人工饲养技术研究提供基础依据,以达到高效饲养豪猪的目的,笔者对豪猪的消化器官进行了系统解剖研究.结果表明:豪猪的胃为单室胃.盲肠很发达,这与其能够消化植物纤维有关.豪猪肝脏很发达,其重量为402 g,是其体重的4.59%,肝脏分叶多而明显.     

Mining of the forest and the time path of the price of timber

The paper analyzes the effect of transportation (site specific) costs and the effect of mining (depletion) of the forest on the time path of the price and of the net price of timber in two forestry models. The models differ in that one has zero costs and the other has positive costs. The analyses yield the standard mining theory results for certain cases. They also yield extentions of these results for cases with growth of the harvested trees and/or regeneration on the harvested land. The paper concludes, as one would expect, that the theory of the mine is useful in analyzing the time path of the price of timber.     

Adjusting the economy to the new energy realities of the second half of the age of oil

Our research indicates that, due to the depletion of conventional, and hence cheap, crude oil supplies (i.e. peak oil), increasing the supply of oil in the future would require exploiting lower quality resources (i.e. expensive), and thus will most likely occur only at high prices. This situation creates a system of feedbacks where economic growth, which requires more oil, would require high oil prices that will undermine that economic growth. We conclude that the economic growth of the past 40 years is unlikely to continue unless there is some remarkable change in how we manage our economy.     

Splitting the tail of the displacement kernel shows the unimportance of kurtosis

Animals disperse in space through different movement behaviors, resulting in different displacement distances. This is often described with a displacement kernel where the long-distance dispersers are within the tail of the kernel. A displacement with a large proportion of long-distance dispersers may have impact on different aspects of spatial ecology such as invasion speed, population persistence, and distribution. It is, however, unclear whether the kurtosis of the kernel plays a major role since a fatter tail also influences the variance of the kernel. We modeled displacement in landscapes with different amounts and configurations of habitats and handled kurtosis and variance separately to study how these affected population distribution and transition time. We conclude that kurtosis is not important for any of these aspects of spatial ecology. The variance of the kernel, on the other hand, was of great importance to both population distribution and transition time. We argue that separating variance and kurtosis can cast new light on the way in which long-distance dispersers are important in ecological processes. Consequences for empirical studies are discussed.     

Stimulation of fat-body production in the polyps of the coralPocillopora damicornis by the presence of mutualistic crabs of the genusTrapezia

A mutualism exists between the xanthid crabs of the genusTrapezia and their host corals,Pocillopora damicornis. It has previously been established that these obligate coral residents benefit the coral hosts by defending them against echinoderm predators and by increasing the survival of polyps located deep between the coral branches. In turn, the corals apparently benefit the crabs by producing lipid-filled structures on which the trapezid crabs feed; these fat bodies may contain some of the lipid which in previous studies of coral metabolism has been termed excess. It was determined by experiments conducted at the Hawaii Institute of Marine Biology that the presence of crabs in colonies ofP. damicornis stimulates the polyps to produce the lipid-filled fat bodies; removal of crabs causes corals to cease producing fat bodies. A structure very similar to the fat bodies ofP. damicornis has been reported inAcropora durvillei. Both of these coral genera ordinarily possess xanthid-crab mutualists. This association between branching corals and crustaceans may have evolved because corals of these genera provide shelter among their branches and because these shallow-water corals are evidently capable of releasing lipid which is excess to the corals' metabolic needs, but which can be utilized by the crabs.     

三峡库区消落带土壤中铅污染调查

报道了三峡库区长江干流及小江支流消落带土壤中重金属铅含量背景值的调查结果。结果表明，目前土壤未被重金属铅污染。