基于CA-Markov模型土地利用对景观格局影响辨识

采用CA-Markov模型方法,研究挠力河流域不同时段土地利用对湿地景观格局干扰强度的差异性.结果表明:(1)流域湿地景观格局变化显著.1967-2000年,挠力河流域湿地类型景观最大斑块指数逐渐减小,耕地和水域斑块的面积周长分维数逐渐减小,而沼泽和居民地的散布与并列指数变大,草甸和耕地聚集度指数增大;湿地景观破碎化程度增加;湿地景观空间分布逐渐由流域周围高地势区向中心河流廊道退缩.(2)流域土地利用变化明显.耕地和居民用地数量迅速增加,耕地趋于集中连片分布,土地利用呈由自然湿地逐渐转化为耕地的变化过程,耕地成为主导的土地利用类型.(3)流域土地利用强度存在阶段差异.1967-2000年,流域内人类活动对湿地景观的干扰强度逐渐加剧,人为景观面积比例由1967年的26.5%上升至2000年的67.8%.土地利用影响强度指数由1967年的1.690上升至2000年的2.394.2000年模拟的流域土地利用影响强度比2000年实际土地利用影响强度小,由此可以识别1983-2000年人类对湿地景观的干扰强度比1967-1983年有所增大;利用居民地和沼泽面积的变化可以识别流域人口增长和排水活动对土地利用影响的时段差异性.     

基于MIKESHE模型的潮河流域土地利用与降水变化对水文的影响评价

运用多测站校正检验机制率定方法,应用MIKESHE模型量化评价土地利用与降水变化对流域水文的影响。结果表明,尽管MIKESHE模型在流域上游大阁站的模拟性能稍逊于下会站和戴营站,3个测站校正和验证阶段的Nash-sutchliffe系数值分别为0.56和0.49、0.65和0.69、0.57和0.68,但模型对于各测站平均径流的模拟效果较好,说明该模型在潮河流域等华北土石山区具有一定的适用性和应用潜力。与基准期(1963—1979年)相比,1980—1989年潮河流域年径流量减少约22 mm,土地利用与降水变化对流域水文变化的贡献相当,两者分别占总径流变化的59%和41%;1990—1999年年径流量较基准期基本没有变化,这主要是由于降水变化与土地利用变化对流域水文的影响作用相反;2000—2008年,流域年径流量较基准期减少35 mm,降水变化对径流减少的影响作用占80%,土地利用变化则占20%。     

开都孔雀河流域近20年土地利用/覆被变化及景观破碎化研究

根据开都孔雀河流域1990、2000和2010年Landsat-TM影像数据和中巴资源卫星数据,结合GIS技术,研究其近20 a土地利用/覆被及景观格局的动态变化特征及变化原因。结果表明,1990—2010年开都孔雀河流域土地利用类型变化最明显的是耕地、建设用地和水域湿地,年均变化率分别为4.76%、-1.61%和1.45%,而未利用地年均变化率最小,为-0.29%。草地面积的8.71%和未利用地面积的1.73%均转变为耕地,草地面积的2.41%转变为水域湿地,建设用地的54.74%转变为未利用地;林地面积在2000年前减少,主要转变为耕地,而在2000年后耕地和草地转变为林地,又使其面积增加。整个研究时段耕地、水域湿地分布趋于集中,逐渐成为研究区的优势景观类型;在2000年前林地分布破碎化明显,在2000年后趋于集中;1990—2010年,草地面积减少,景观优势度下降,景观形状趋于简单。认为人口的不断增加以及经济利益的驱动使得流域内耕地面积不断扩大,从而严重危及流域的生态环境安全。     

岷江流域不同土地利用方式下紫色土有机碳储量特征

以岷江中下游流域紫色土为研究对象,按流域分上中下游区段3个抽样层采样,研究不同土地利用方式下紫色土有机碳储量特征,为紫色土退化评估及地力维护提供参考.结果显示,紫色土有机碳总量以林地(14.151g/kg)显著高于果园地(9.458g/kg)、菜园地(8.542g/kg)、草坡地(7.875g/kg),以玉米地(6.226g/kg)最低.水溶性有机碳含量呈现林地>果园地>菜园地>草坡地>玉米地趋势.同时,流域上、中、下游紫色土有机碳总量总体上差异显著,且以上游区段紫色土有机碳总量最高.流域中下游紫色土有机碳总量变化较大,其中,林地以下游高于中游,果园及草坡地以中游高于下游.菜园地、玉米地在3个区段上差异未达显著水平.岷江流域紫色土有机碳储量总体特征表现上游最高,中下游变化复杂,下游略高于中游区域.图1表4参10     

黄土小流域水沙输移过程对土地利用/覆被变化的响应

以甘肃定西安家沟小流域为典型研究区,基于TM、ALOS遥感影像解译和地面长期水文数据,深入分析了1997至2010年间流域土地利用变化特征及其产流产沙效应。结果显示,（1）14年间,流域林灌草面积分别增加160.23%、176.33%和80.75%;坡耕地、居民地、裸地和梯田面积分别减少25.57%、0.16%、48.45%和21.52%。以2005年为时间节点,发现前期灌草增加较多、裸地减少明显,后期则是乔木增加比例和坡耕地减少比例更为显著,彰显出不同历史阶段植被恢复的策略变化。（2）流域出口多年平均径流量和输沙量分别由前期的18 249 m3和6 383 kg锐减至后期的2 292 m3和2 267 kg,流域土地利用/覆被有效增加是其主要驱动。（3）春冬季节,由于降雨稀少、径流泥沙的本底值很低,前后两个阶段的水沙输移量差异较小,土地利用/覆被变化的影响相对尚不显著。但在夏秋季节,随着降雨事件增多,土地利用/覆被变化减水减沙的效应趋于显性化。     

1961─2010年降水和土地利用变化对淮河干流上中游径流的影响

为了研究近50a来降水和土地利用变化对淮河干流上中游径流变化的影响程度,利用逐日径流和降水资料,采用线性趋势、累积距平、Mann-Kendall非参数检验法和t检验等统计方法,探讨了淮河干流上中游径流的变化趋势、突变等,并基于双累积曲线,构建了降水-径流关系模型,定量估算了降水和土地利用变化对径流的贡献程度。结果表明,(1)淮河干流上游径流量呈增加趋势,其线性倾向率为0.08×10~8 m~3·a~(-1),而中游呈减少趋势,其线性倾向率为-0.38×10~8 m~3·a~(-1),且中游径流量C_v大于上游;上游和中游降水量均呈增加趋势,其线性倾向率分别为0.34和1.72 mm·a~(-1);径流量的年际波动均大于降水量。(2)上游径流量突变年份为1972年,降水对径流量影响的基准时段为1961-1972年;中游径流量突变年份为1985年,降水对径流量影响的基准时段为1961-1985年。(3)相对于基准时段,降水有利于径流增加,而土地利用变化导致径流减少。(4)土地利用变化是引起径流变化的主导因素,对上游和中游径流量变化的贡献率分别为76%和74%;降水对径流量变化起着次要作用,但其影响也不容忽视。     

干旱内陆河流域土地利用变化及其对环境的影响——以西北地区黑河流域为例

从区域的角度,研究土地利用/土地覆被变化导致的生态环境退化,对于丰富土地利用/土地覆被变化研究内容具有重要的理论意义,同时又对当地生态环境的保护与恢复具有现实的指导意义。文章以我国西北干旱区内陆河流域黑河为例,利用遥感和GIS技术,分析和评价近17年(1987—2004年)来该流域土地利用的动态变化及其对于整个流域环境的影响。研究结果表明,自1987—2004年黑河流域5种土地利用类型面积发生了显著的变化。具体表现在耕地面积由1987年的5178.0km2增加到2004年的5357.8km2,林地面积从1987年的6422.1km2增加到2004年的6450.4km2,城镇用地面积从1987年的115179.5km2增加到2004年的115791.4km2;另一方面,草地面积却从1987年的27710.6km2减少到2004年的27209.3km2,水域面积从1987年的1645.7km2减少到2004年的1386.4km2。同时又分别从黑河上、中、下游方面,对土地利用变化情况作了具体的分析。通过以上研究可以看出,近17年来,黑河流域土地利用发生了深刻的变化,由此造成了整个流域的生态环境退化问题,主要表现在水环境的变化、土地荒漠化、土壤盐渍化以及植被退化等方面。     

基于SWAT模型的淠河流域土地利用变化的水文响应模拟

以淮河南岸最大支流——淠河流域为研究区域,采用嵌套入ArcGIS软件的SWAT分布式机理性水文模型定量评估土地利用变化对降水-径流关系的影响.结果表明,1996-2010年淠河流域的土地利用变化主要表现为水田、旱地向建设用地转化以及林地向园地转化.相较于1996年的土地利用情景,2010年土地利用情景下的多年平均径流增加5.87％,年径流的增加主要表现为汛期径流增加,非汛期径流则呈减少趋势,径流量年内变幅加大.对于不同水文年份而言,平水年对土地利用变化的水文响应最明显,变幅最大,枯水年则略大于丰水年,淠河流域的水源涵养能力呈现减退趋势.     

岷江上游干旱河谷荒坡植物群落种-面积曲线拟合及最小面积确定

采用由3种曲线方程拟合的群落种-面积曲线来确定岷江上游干旱河谷荒坡植物群落的最小取样面积,结果表明:对于岷江上游干旱河谷荒坡植物群落类型而言,利用方程S=c-ae-bA拟合所得的种-面积曲线好于其他方程.当比例因子ρ取0.6、0.7、0.8时,群落最小面积均小于2 m2,样方可设置为1 m × 2 m,即样地面积为2 m2,能够满足精度60%～80%的研究要求;当ρ取0.9时,群落最小面积均明显小于4 m2,样方可设置为2 m × 2 m,即样地面积为4 m2,能够满足精度90%的研究要求.     

云南纵向岭谷区河流输沙量对土地利用变化的响应——以黑惠江、龙川江、盘龙河流域为例

以黑惠江、龙川江、盘龙河流域为例,探讨了云南纵向岭谷区河流输沙量对土地利用变化的响应关系。结果表明,林地面积增加,耕地和草地面积减少,使河流输沙量明显降低;林地向耕地和草地的转化以及草地向耕地的转化,导致输沙量明显增加。黑惠江流域和盘龙河流域在1990年后的10 a中土地利用方式趋于合理,年输沙量呈现减少趋势;而龙川江流域土地利用的合理性降低,年输沙量呈现增加趋势。3个流域河流输沙量变化均符合气候变化的大趋势,土地利用变化是河流输沙量变化的主要原因。3个流域河流输沙量对土地利用的响应规律符合山地河流的一般规律,但是其表现强于地势相对平缓的地区。     

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.     

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.     

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.     

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．     

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.     

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.     

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.     

Hypothesis Concerning the Causes of the Disappearance of Boreal Toads from the Mountains of Colorado

Recent reports of world-wide declines and extinctions of amphibian populations have raised questions about the relation of environmental change to the demise of certain amphibian species. Between 1974 and 1982, 11 populations of boreal toads ( Bufo boreas boreas ) in the West Elk Mountains of Colorado totally disappeared. The apparent cause of extinction of these toads was infection with the bacteria Aeromonas hydrophila . In this paper, the presence of disease in declining populations of these toads is used in conjunction with a variety of data from the literature to formulate a working hypothesis for explaining the cause of the decline of this species, and perhaps others: