Structure regulation of land use and landscape pattern changes based on matter element analysis in a small watershed in Sichuan,China

The agricultural land suitability assessment based on the natural characteristics of land blocks is tra-ditionally the basis for agricultural and/or land use plan-ning.The assessment,however,is static and cannot be incorporated with potential land use changes.Recently,a dynamic approach,i.e.,matter element analysis,has been effectively applied for land use planning.In the pre-sent study,based on matter element analysis,we estab-lished a matter element analysis model for land use suitability assessment using the suitability grade of land use,evaluation indicators and their characteristic values as matter elements,and also using sutra field,controlled field,weight value and correlation degree from field sur-vey,as well as an expert system.This model was applied to the structure regulation of the land use in the small Yuejiagou watershed of the Langzhong Municipality in Sichuan Province,China.Results show that the propor-tion among agriculture,forestry and animal husbandry tended to rationalize land use.The economic and eco-logical indices of the lands were increased from 1529.8 to 1719.99 and from 1460.94 to 1758.21 after the regu-lation,respectively.The regulation also caused changes in landscape patterns as follows:The indices of diversity and evenness were increased from 1.3028 to 2.0920 and from 0.6108 to 0.8463,or by 60.58% and 38.56%,respect-ively.However,the indices of dominance and contagion were decreased from 0.6431 to 0.2106 and from 0.7467 to 0.7125,respectively.This indicated that the land use in the small watershed was rational.The spatial distribution of patches tended to be uniform.The patch congregation was gradually dispersed.This study verified that the mat-ter element analysis approach can not only overcome the factitious influences and improve the precision of land assessment,but also can be used for the structure regu-lation of specific patches.     

基于物元分析的小流域土地利用结构调整及景观格局变化

将土地利用的适宜度、适宜度评价指标及其特征值作为物元,由实测资料和专家系统综合得到模型的经典域、节域、权重及关联度,建立起土地利用适宜性评价的物元分析模型,将模型应用于四川省阆中市岳家沟小流域土地利用结构调整中.结果表明,经调整后,该区的农林牧比例趋于合理,土地的经济效益指数、生态效益指数分别由原来的1529.80、1460.94提升到1719.99、1758.21.此外,调整后,景观格局发生变化：景观多样性指数（H）和景观均匀度指数（E）分别由调整前的1.3028和0.6108增加到调整后的2.0920和0.8463,分别增加了60.58%和38.56%,最大多样性指数上升了18.33%.而景观优势度和蔓延度指数则由调整前的0.6431和0.7467减少到调整后的0.2106和0.7125.说明景观斑块的空间分布趋于均匀,斑块的聚集状况分散化.实例证明,在小流域土地利用结构调整中,物元分析方法能克服土地适宜性评价过程中人为因素的影响,提高评价的精度,而且能落实到山头、地块,具有较强的可操作性.     

基于斑块评价的三峡库区腹地坡耕地优化调控方法与案例研究

三峡库区腹地坡耕地大量存在,且25°的陡坡耕地实现全部退耕还林难度很大,同时还存在农户自发弃耕撂荒现象。有必要深入探讨库区腹地不同地域特征下坡耕地优化调控的理论与方法。在充分考虑坡耕地的分布现状和未来发展趋势的前提下,设定了坡耕地优化调控的6个原则,提出空间优化适宜性评价和农户对坡耕地资源的需求压力数量评价相结合的坡耕地综合优化调控方法。选取库区腹地典型流域草堂溪流域进行案例研究。根据草堂溪流域特点以及坡耕地分布特征,从坡耕地可达性、生态功能和坡改梯适宜性3方面选取相关指标作为格局适宜性调控体系,选取耕地压力指数和果园对农户需求的补充能力作为数量调控体系。综合优化将研究区坡耕地分为优化利用型、重点整治型、逐步退耕型和优先退耕型4种类型,结合研究区坡耕地特点在保持耕地压力不增加、减少陡坡不适宜耕地和土壤侵蚀的前提下设置了4种退耕情景。最后根据农户自发撂荒地的空间分布特征,验证了评价指标体系建立的合理性和正确性。     

泾河流域分县景观格局特征及相关性

景观生态主要是研究生态系统的空间格局。因而很有必要对空间格局进行数量化的分析,在此基础上进行科学管理。应用斑块数、斑块面积、斑块密度、优势度、聚集度和分维数计算了泾河流域31个县景观格局的特征,首次以景观特征值为基础,将研究区域各县景观进行分类,并对不同类型的景观特征及相关性进行分析。结果表明,近年来流域破碎化程度有所增加,各景观指数值在研究区域之间变异很大。优势度和聚集度比较高的区域土地利用较单一,常常是以农用地为主导如咸阳、泾阳和乾县,或以农地和草地共同主导如环县。而优势度和聚集度较低的区域,土地利用较多样化,农地、林地和草地面积比例相近,如泾源、平凉、陇县、宁县和旬邑,这些县位于黄土丘陵沟壑区和黄土高塬沟壑区。高优势度、高聚集度和低分维数的区域为陕西省咸阳市,为泾河流域冲积平原区,土地利用以大面积的农用地为主导。景观指数的相关分析表明,3种主要的土地利用面积比例之间存在极显著负相关,林地面积和优势度、聚集度有极显著负相关,而草地面积和分维数存在极显著正相关,分维数高的县位于泾河流域中游的黄土高原沟壑区,分维数低的县位于下游河谷阶地和关中平原和黄土高原交界处。这种相关性表明了自然地貌及人类活动对景观的影响和干扰作用。     

基于小流域尺度的土壤重金属分布与土地利用相关性研究——以厦门市坂头水库流域为例

人类活动改变流域集水区土地利用方式同时提高了土壤重金属水平,并影响地表水重金属负荷。以具有明确地理边界的流域作为研究单元可能实现计量区别不同人类活动或因其引起的土地利用方式对土壤重金属空间分布及其环境风险的贡献。但不同人类活动及其改变的土地利用方式对土壤和地表水重金属负荷的相对贡献研究缺乏可操作性方法论。以我国典型的山塘水库小流域—福建省厦门市坂头水库流域为例,结合遥感影像解译、野外土壤重金属水平调查和GIS地统计方法,针对小流域尺度土壤重金属空间分布及其环境风险与土地利用方式相关性研究进行方法论的探索。坂头水库流域覆盖205km2,土地利用类型有林地、农业用地、城镇用地、绿地和水面等5大类。按照不同土地利用类型覆盖面积为权重,以统计最小样本数为准则,在该流域内共采集150个表层土壤样品,针对6种具有人为源特征重金属(Cu、Zn、Pb、Cr、Ni、Cd)土壤总量及富集水平进行分析,以潜在生态风险指数评价流域土壤重金属风险,并结合土地利用类型分析了其空间特征。结果表明:与林地和绿地相比,城镇用地和农业用地表层土壤重重金属水平显著较高;土壤重金属富集水平及其潜在生态风险依次为:城镇用地农业用地绿地林地;城镇化加重了流域土壤重金属Cu、Zn和Cd的污染风险;土壤Pb富集水平与土地利用方式无关,可能为大气沉降来源;所有土地利用方式土壤Cr和Ni总量低于区域土壤背景值,但城镇用地的富集指数显著高于林地。基于土地利用方式的反距离加权空间插值(LU-IDW)也清晰地揭示了土壤重金属富集及其潜在生态风险与人类活动密切相关,尤其是城镇化。以野外调查结合遥感卫星图像解译和基于土地利用方式的空间插值的研究方法有效地揭示了研究流域土壤重金属的空间分布特征及其潜在风险评价空间模式,为小流域尺度的环境质量演变研究提供了方法论和案例。     

流域景观类型及配置对大型底栖动物完整性的影响

通过对滦河流域66个河段大型底栖动物采集和生境指标监测,基于大型底栖动物完整性评价和13种景观指数构建,探讨了不同景观指数对于大型底栖无脊椎动物完整性的解释能力。景观指数类型包括流域及欧式距离缓冲区土地利用百分比、水流路径缓冲区土地利用百分比、局部区域土地利用百分比和基于水流路径的反距离权重指数。基于多元线性逐步回归模型,根据调整R2(Square of the coefficient)来判断不同指数的解释能力。研究结果表明基于水流路径的反距离权重指数对于大型底栖动物完整性的解释能力最好,其次为基于水流路径的缓冲区和局部区域的土地利用百分比指数,全流域及欧氏距离缓冲区内土地利用百分比解释能力最差。农田是影响大型底栖动物完整性最重要的景观类型,距离河流越近的农田对大型底栖动物完整性的影响越大,因此流域及河岸带农田的控制和管理对于滦河流域大型底栖动物完整性的恢复具有重要的作用。     

Combination of fuzzy-AHP and GIS techniques in land suitability assessment for wheat (Triticum aestivum) cultivation

Land suitability classification is a useful management practice to ensure planned and sustainable use of agricultural lands according to their potentials. The main purposes of this study were to analyze land suitability for bread wheat (Triticum aestivum) cultivation and generate a land suitability map for wheat by integrating the analytical hierarchy (AHP)-fuzzy algorithm with the Geographical Information System (GIS) in the Tozanl? sub-basin located in the upper part of Ye?il?rmak Basin, Turkey. Topographic (elevation, slope, aspect) characteristics of the basin and some of physical and chemical properties of soils (texture, pH, electrical conductivity, lime, organic matter, and soil depth) were used as criteria in determining the suitability classes. Ninety-two disturbed soil samples were collected from 0 to 20 cm depth in October 2017 using random sampling method. Weighted overlay spatial analysis in GIS was used to combine different thematic layers to identify areas suitable for wheat production. The fuzzy-AHP suitability assessment model was adapted to determine the weights for topographic and soil properties. The highest specific weights were obtained for soil depth (0.232) and elevation (0.218), while the lowest weight was calculated for aspect (0.042). Highly, moderately, and marginally suitable lands for wheat cultivation cover 2.63, 9.85 and 32.59% of the study area, respectively. In addition, the results indicated that 54.92% of the total area is permanently unsuitable for wheat cultivation. The results revealed that integration of AHP-fuzzy algorithm and GIS techniques is a useful method for accurate evaluation of land suitability in planning for specific crop production and decreasing the negative environmental impacts of agricultural practices.     

1980-2010年北京市农用地碳储量对土地利用变化的响应

分析北京市农用地碳储量对土地利用变化的响应,对快速城市化和工业化区域及全国农用地低碳利用调控具有重要意义。利用1980年第二次土壤普查数据与2010年测土配方施肥项目成果土壤数据核算北京市农用地表层土壤碳储量,利用生物量遥感信息（NDVI）模型反演林地、草地植被碳储量,对北京市土地利用变化造成的农用地碳储量变化进行研究,结果表明：1）1980-2010年,北京市农用地碳储量由75.29 Tg-C增至81.13Tg-C,增加5.83 Tg-C,其中,土壤碳储量减少7.51 Tg-C,植被碳储量增加13.34 Tg-C;2）30年间,北京市农用地面积减少14.11×10⁴ hm²,其中,耕地流失最为显著,主要去向为建设用地和林地,林地面积略有增加;3）北京市用地类型保持不变的农用地土壤碳储量减少297.63×10⁴ t,植被碳储量增加1095.21×10⁴ t,共计增加797.58×10⁴ t,其中,用地类型保持不变的耕地、林地碳储量增加,草地碳储量减少;4）30年间,土地利用类型转化使北京市农用地土壤碳储量减少75.71×10⁴ t,植被碳储量增加212.49×10⁴ t,共计增加136.78×10⁴ t,其他用地类型转为林地使碳储量增加,有利于碳汇的形成,林地转出为其他用地类型均会造成一定碳排放;5）平原造林、退耕还林等工程有利于增加北京市农用地固碳量。未来北京市可通过控制农用地面积减少量,优化农用地内部结构,降低用地类型间的转换频率以提高农用地碳储量。研究可为其他区域及全国在快速城市化工业化过程中提升农用地碳储量提供一定参考。     

Degradation and loss of forest land and land-use changes in Sarawak,East Malaysia: a study of native land use by the Iban

Swidden agriculture, commercial logging and plantation development have been considered to be the primary common causes of degradation and loss of tropical rain forests in Southeast Asia. In this paper, I chose a part of northeastern Sarawak, East Malaysia as my case study area to analyze the changes in its land-use characteristics. In the study area, as well as primeval forests, we see that land use began about 100 years ago by a native group called the Iban; commercial logging began in the 1960s, and the development of oil palm plantations began recently. I describe the changes in land use as well as their social and economic causes by referring to aerial photographs, literature surveys, interviews with government officers and the Iban, and observation of land use. My analysis of land use demonstrates that on “state land”, where commercial logging and oil palm plantation development are occurring, large areas of forest have been disturbed in a short period of time. The objective is to benefit economically in response to the social and economic conditions surrounding the study area. On the other hand, in the “Iban territory,” where the Iban practice their land use, land conversion has not occurred on a large scale and in a short period of time, even though the forest has been cut and agricultural fields have been created in response to social and economic conditions as well. They disperse small agricultural fields throughout their forest land. Therefore, the landscape of the “Iban territory” is based on secondary forest, composed of patches of forest in various stages and with several types of agricultural land. Today in Sarawak, monocrop plantations are rapidly expanding and little primeval forest remains. Given these conditions, the land-use practices of natives such as the Iban will be evaluated from the viewpoint of ecosystem and biodiversity conservation. It could play an important role in providing habitats for natural wildlife.     

基于13C、15N和C/N识别南岳小流域沉积有机质的来源

农业流域有机质流失造成水体富营养化和土地退化,不仅威胁水质和粮食安全,而且会导致温室气体排放等潜在环境问题。本研究用¹³C、¹⁵N和C/N作为指纹标志物,分析了南岳小流域出口沉积有机质的来源及其在林地、稻田和菜地等典型土地利用类型土壤的空间分布特征,并结合贝叶斯稳定同位素混合模型定量估算了各土地利用类型的贡献率。结果表明: δ¹³C具有显著的空间差异,沉积物有机质(-22.6‰±0.53‰)和林地土壤(-23.13‰±1.71‰)的δ¹³C显著高于稻田土壤(-25.24‰±1.4‰)。各土地利用类型土壤的δ¹⁵N差异不显著,沉积物的均值最大,为(4.37±0.83)‰,林地最小,为(2.38±1.97)‰;林地土壤的C/N均值最大,为16.66±7.18,稻田土壤的C/N均值最小,为11.95±0.92。贝叶斯稳定同位素混合模型结果显示,林地、稻田和菜地对流域出口沉积有机质的贡献率分别为19.6%、15.7%和64.7%;稻田和菜地作为农业用地的总贡献率为80.4%。说明农业用地土壤是南岳小流域沉积有机质的主要来源,可以通过优化农田管理措施有效控制流域养分流失。     

Effect of Native Vegetation Loss on Stream Ecosystem Processes: Dissolved Organic Matter Composition and Export in Agricultural Landscapes

Stream and river ecosystems are dependent on energetic inputs from their watersheds and thus shifts in land use from forest cover to agriculture will affect stream community composition and function. The disruption of forest-aquatic linkages alters the organic matter resources in agricultural streams. Dissolved organic matter (DOM) is the dominant form of organic matter in aquatic ecosystems, and a microbial energy source that is important for stream respiration. The concentrations and characteristics of DOM are regulated by both terrestrial (for example, terrestrial organic matter supply) and in-stream processes (for example, microbial respiration and periphyton production) that are influenced by land management. The effects of watershed land use and topographic, soil and climatic variables on DOM quantity (dissolved organic carbon concentration and load), source (terrestrial or in-stream) and quality (composition and lability) were measured in 14 streams across an agricultural land-use gradient. DOC concentration was positively correlated with watershed pasture cover and negatively correlated with watershed relief. No watershed variables were important correlates of DOC load. Stream DOM was primarily of terrestrial origin, but DOM in agricultural streams had a greater proportion of sources from in-stream sources. This may be due to reduced connection with riparian vegetation and increased in-stream primary production. We suggest that maintaining watershed tree cover greater than 52% and ensuring less than 10% of the length of riparian corridor is cleared for pasture could minimize changes to DOM composition. This is important to avoid flow-on effects for stream ecosystem processes that are mediated by DOM. Long-term DOM monitoring will be valuable for assessing the functional impacts of land-use change.     

Biotelemetry of crustacean decapods: sampling design,statistical analysis,and interpretation of data

Lotic systems in many regions of the country have experienced habitat degradation and biodiversity loss due to agricultural activity and urbanization. Southeastern Michigan is no exception, as agriculture in the River Raisin watershed and increased urbanization in the Huron River watershed threatens both systems. To further understand the ecological impact of land use on trophic interactions in Midwestern streams and assess the use of a selected set of weighted, quantitative food web metrics as a tool for investigating the influence of anthropogenic disturbance on these systems we compared summer food webs for nine second-order streams. All streams were categorized as developed, undeveloped, or agricultural based on land cover data. Developed and undeveloped streams were located in the Huron River watershed and agricultural streams were located in the River Raisin watershed. Reach-level habitat quality was also assessed at each study site using the EPA’s Rapid Habitat Assessment. Fish diets (n = 410) were analyzed to create summer food webs for each site. Comparisons of food webs were made using a suite of weighted, quantitative metrics to identify differences in fish–macroinvertebrate interactions across streams with differing land cover at the sub-basin scale and habitat quality at the local scale. Although undeveloped streams had higher species richness and less habitat degradation, no significant patterns were observed in the quantitative metrics across the three stream categories or based on reach-level habitat conditions. Decapoda, terrestrial Hymenoptera, and Chironomidae were the primary prey taxa in all stream categories. Decapods accounted for the majority of biomass consumed and the pattern of this consumption strongly influenced metric scores. The suite of quantitative metrics tested in this study did not detect significant differences in fish–macroinvertebrate food webs across land use categories, likely in part due to the dominance of a large, tolerant prey taxa in fish diets, regardless of land use and local habitat quality.     

Impact of riparian buffer zones on water quality and associated management considerations

Recent attention has focused on riparian forest buffer systems for filtering sediment, nutrients, and pesticides entering from upland agricultural fields. This paper summarizes the results of a field monitoring study done in Tokachikawa watershed in Hokkaido, Japan, Cisadane, Cianten and Citamyang sub-watersheds in Indonesia and Cauvery watershed, India to quantify the impact of riparian buffer zones on changes in stream water quality. A watershed approach was used to compare land use indicators – uplands, forests, riparian forest, livestock areas – to a wide range of surface water physical and chemical properties. Stream water physical property values increased from upstream to the confluence point, influenced by the upland and livestock land use activities. The greatest reduction in impairment of water quality was observed in buffer zones located along higher order streams where the gradient is very low, leading to slow groundwater movement. The lower stream water temperature in riparian buffer zones suggests that the shading effect is most pronounced in this area of the watershed. The results demonstrate the positive impact of forest buffer zones in reducing the influence of agricultural nutrients and chemicals on surface stream waters. Design and management considerations for establishing riparian zone land use are discussed.     

流溪河流域景观空间特征与河流水质的关联分析

人类活动影响或改变流域景观空间结构,并有可能对河流水质产生不同程度的影响,以流溪河流域为研究区,分析流域景观空间格局特征与水质指数之间的相关关系。将流域划分为27个子流域,采集水样分析水质状况,所选用的水质指标有氨氮(NH3-N)、硝态氮-亚硝态氮(NO3-N+NO2-N)、总磷(TP)、化学需氧量(CODCr)。结果表明:1)该流域土地利用结构与水质具有显著相关性,其中居住用地对水质的影响作用最强,林地对河流水质具有净化功能,与水质指标之间的关系表现为负相关,园地与水质指标关系具有不确定性;2)流域景观特征从上游到下游之间表现为城市化增强的梯度,水质状况响应这个梯度变化表现为上游优于下游,人类活动及城市化发展引起的土地利用变化及土地管理方式对水质变化有显著影响;(3)景观破碎度与水质呈现显著正相关性,是影响水质的重要指标,景观聚集程度和斑块形状复杂程度与水质有负相关关系;子流域尺度和河岸带尺度景观空间特征对水质的影响差异不明显。     

中国农用地集约度与农业气候适宜度的空间关系研究

通过构建指标体系,对全国30个省(区、市)农用地集约度做了评价计算;基于前人的研究成果,运用空间插值的方法计算了农业气候适宜度;并在此基础上对二者的空间关系进行了研究。主要结论是:(1)总体而言,我国农用地集约度东部地区大于西部地区,农业气候适宜度由东南向西北递减。从某种程度上说,农业气候适宜度制约着我国农用地集约度的空间布局,但是集约度的提高也可以改变农用地集约利用对气候条件的依赖性。(2)1995～2005年我国农用地集约度总体提高12.6%;农业气候适宜度低的省(区、市)提高最明显,适宜度中等的省(区、市)次之,适宜度高的省(区、市)最不明显。(3)根据农业气候适宜度的空间关系,就因地制宜地对农用地进行集约经营提出两点建议。     

基于土地利用冲突识别的国家公园社区调控研究——以钱江源国家公园为例

功能分区和土地利用冲突识别为国家公园社区调控提供空间指引，为社区精细化管理提供依据。以钱江源国家公园试点区（以下简称为"钱江源国家公园"）为例，综合考虑国家公园建设多重目标，建立了生态保育、游憩利用和农业生产适宜性评价体系，并基于三类适宜性构建潜在土地利用冲突识别矩阵。通过叠加国家公园功能分区与土地利用冲突分析结果，识别国家公园社区类型并提出调控措施。结果表明：①三类适宜性土地利用总量较丰富且存在空间差异，其中生态保育适宜性呈中部高，南北两侧低的分布特征，游憩利用、农业生产适宜性呈中部、北部高，南部低的空间特征；②土地利用冲突识别矩阵将钱江源国家公园土地利用冲突划分为4大类，即用地优势区、冲突激烈区、冲突一般区和冲突微弱区，其中47.24%的土地存在潜在利用冲突，冲突等级以冲突激烈为主，用地优势区占比50.21%；③基于国家公园功能分区框架与土地利用冲突结果叠加分析，将国家公园社区划分为区外安置型、控制发展型、优先整治型、游憩发展型、特色农业型5种类型，并提出差异化调控措施。     

Land-Use Change and Stream Water Fluxes: Decadal Dynamics in Watershed Nitrate Exports

Stream water exports of nutrients and pollutants to water bodies integrate internal and external watershed processes that vary in both space and time. In this paper, we explore nitrate (NO₃) fluxes for the 326 km² mixed-land use Fall Creek watershed in central New York for 1972–2005, and consider internal factors such as changes in land use/land cover, dynamics in agricultural production and fertilizer use, and external factors such as atmospheric deposition. Segmented regression analysis was applied independently to dormant and growing seasons for three portions of the period of record, which indicated that stream water NO₃ concentrations increased in both dormant and growing seasons from the 1970s to the early 1990s at all volumes of streamflow discharge. Dormant season NO₃ concentrations then decreased at all flow conditions between the periods 1987–1993 and 1994–2005. Results from a regression-based stream water loading model (LOADEST) normalized to mean annual concentrations showed annual modeled NO₃ concentration in stream water increased by 34% during the 1970s and 1980s (from 1.15 to 1.54 mg l⁻¹), peaked in about 1989, and then decreased by 29% through 2005 (to 1.09 mg l⁻¹). Annual precipitation had the strongest correlation with stream water NO₃ concentrations (r = −0.62, P = 0.01). Among land use factors, corn production for grain was the variable most highly correlated to stream water NO₃ concentrations (r = 0.53, P = 0.01). The strongest associative trend determined using Chi-squared Automatic Interaction Detection (CHAID) was found between stream water NO₃ concentrations and N-equivalence of dairy production (Bonferroni adjusted P value = 0.0003). Large increases in dairy production were coincident with declining nitrate concentrations over the past decade, which suggest that dairy management practices may have improved in the watershed. However, because dairy production in the Fall Creek watershed has been fueled by large increases in feed imports, the environmental costs of feed production have likely been externalized to other watersheds.     

The Influence of Land Use on Lake Nutrients Varies with Watershed Transport Capacity

Nutrient loading to lakes depends on both the availability of nutrients in a watershed and their potential for movement to a lake. Many studies have demonstrated that variation in watershed land use can translate to differences in lake water quality by affecting nutrient availability. There have been few attempts, however, to understand how loading to surface waters is affected by land use when there are differences in watershed transport capacity. We compared the relationship between land use/cover and lake nutrients in lakes draining watersheds that exhibited high and low transport capacity using a 5 year (2001–2005) dataset describing the chemistry of 101 lakes and reservoirs in a region of intensive agriculture. We measured watershed transport capacity by compositing the hydrologic, geologic, and topographic variables correlated with interannual variability in lake total nitrogen (TN) or phosphorus (TP) because the hydrologic permeability of watersheds amplifies downstream responses to rainfall events. Factors describing watershed transport capacity differed for TN and TP, consistent with differences in nutrient mobility and biogeochemistry. Partial least squares regression revealed that watershed transport capacity influenced the nature of the association between land use/cover and lake chemistry. In watersheds with low transport capacity, in-lake processes and near-shore land use/cover tended to be more influential, whereas, in watersheds with high transport capacity, land use/cover across the entire watershed was important for explaining lake chemistry. Thus, although land use is a key driver of nutrient loading to lakes, the extent to which it influences water quality can vary with watershed transport capacity. JMF conceived the study and analyzed the data. JAD collected the data. JMF and JAD wrote the paper.     

陕北典型退耕还林区林下草本物种生态位研究

基于样方法进行不同资源位的群落调查,并用群落物种多样性、生态位宽度、生态位重叠和生态位相似性比例分析了安塞县典型退耕区16种不同退耕模式及年限群落林下草本物种生态位特征。结果表明:乔木林下草本群落物种多样性高于灌木林。生态位宽度以达乌里胡枝子和阿尔泰狗娃花最大,它们的Shannon-Wiener(Bs-w,i)和Levins(Bl,i)指数分别为0.89、0.83和0.64、0.58。生态位宽度较大的种间生态位重叠程度大,如阿尔泰狗娃花、铁杆蒿、长芒草等。生态位宽度与生态位相似比例值并不一致。生态位相似性比例小于0.5的种对有174对,约占种群总对数的91.6%,说明种群对环境需求有较大的差异,各种群能较好地共生于群落中。     

基于土地利用/覆被变化的流域景观格局与水沙响应关系研究

以黄河流域的2个典型流域为研究对象,借助GIS和Fragstats平台与长系列水沙数据,分析流域景观格局和水沙变化特征,并探讨景观指数与径流输沙的关系。结果表明:(1)两个流域优势景观类型为草地,1985—2010年间变化最大的景观类型分别为未利用土地(25a变幅为453.94 km~2)和耕地(25a变幅为52.85 km~2);(2)秃尾河流域景观均向规则、高连通和高度聚集的方向发展。孤山川控制流域内景观多样性和聚集度逐渐增加,整体向好。秃尾河流域景观稳定性指数高于孤山川流域,两流域草地和未利用土地地稳定性均呈增加趋势,而城乡工矿用地则相反。(3)流域年径流量和泥沙量均呈现逐年同步减小的趋势。秃尾河年径流量明显高于孤山川,但孤山川流域泥沙量与秃尾河流域相近。两流域径流泥沙相关关系显著,秃尾河流域相关系数(0.48)明显低于孤山川流域(0.85)。(4)景观指数与径流量、泥沙量呈显著线性相关,其中景观多样性相关的指数SHDI、SIDI、SHEI和SIEI均与径流呈极显著正相关,而泥沙仅与CONTAG、COHESION呈显著负相关。