Landscape structure and breeding bird distribution in a sub-Mediterranean agro-ecosystem

Richness, abundance and distribution of birds were investigated in the Aulella watershed,a mountainous area of 300 km², located in the extreme northwestern corner of Tuscany, Italy in spring and summer, 1995. The study area encompasses five vegetation types (from Mediterranean maqui to upland beech forest) and three main land use categories (woodlands, mixed cultivated + urban areas, montane prairies). The recent history of land abandonment in the study area has produced a rapid expansion of shrubland and woodland, reducing cultivated areas to small patches interspersed in a woodland matrix. Richness, abundance and distribution of birds recorded at 414 points, randomly selected along secondary roads, and located using a Global Positioning System (GPS), were compared with topography, vegetation type and land use in a Geographic Information Systems (GIS) with a grid cell resolution of 200 × 200 m. Bird richness (55 species in all) and abundance are correlated: (a) negatively with the increasing altitude and increasing distance from cultivated areas; (b) positively with the increasing distance from woodlands and mountain prairies. Slope orientation appears to have a negligible effect on bird assemblages. Bird richness and abundance are significantly correlated with vegetation type. Cultivated areas support the highest bird richness and abundance that increase with patch size of the cultivated areas. Local extinction and/or reduction in within-species abundance of birds are expected to continue if the process of land abandonment continues. This revised version was published online in July 2006 with corrections to the Cover Date.     

北京西山灌木林小流域暴雨径流研究*

利用北京西山次生灌木林地上６个小流域的实测降雨径流数据，采用ＩＵＨ法，分析影响径流的主要因子，并对降雨径流进行预测，结果表明：ＩＵＨ法在小流域上应用效果较好，对径流过程的拟合较为一致；天然次生灌木林具有良好的水源涵养功能，在森林植被覆盖率超过４０％时，每增加１０％，ＩＵＨ洪峰可降低４．６％，洪峰滞时可延长９．３％。     

一种基于数字高程模型的流域边界提取修正方法

Boundary extraction of watershed is an important step in forest landscape research. The boundary of the upriver watershed of the Hunhe River in the sub-alpine Qingyuan County of eastern Liaoning Province, China was extracted by digital elevation modeling (DEM) data in Arclnfo8.1. Remote sensing image of the corresponding region was applied to help modify its copy according to Enhanced Thematic Mapper (ETM) image‘s profuse geomorphological structure information. Both the DEM-dependent boundary and modified copy were overlapped with county map and drainage network map to visually check the effects of result. Overlap of county map suggested a nice extraction of the boundary line since the two layers matched precisely,which indicated the DEM-dependent boundary by program was effective and precise. Further upload of drainage network showed discrepancies between the boundary and the drainage network. Altogether, there were three sections of the extraction result that needed to correct. Compared with this extraction boundary, the modified boundary had a better match to the drainage network as well as to the county map. Comprehensive analysis demonstrated that the program extraction has generally fine precision in position and excels the digitized result by hand. The errors of the DEM-dependant extraction are due to the fact that it is difficult for program to recognize sections of complex landform especially altered by human activities, but these errors are discernable and adjustable because the spatial resolution of ETM image is less than that of DEM. This study result proved that application of remote sensing information could help obtain better result when DEM method is used in extraction of watershed boundary.     

新立小流域侵蚀地带动态仿真模型的研究

在新立小流域景观生态设计基础和系统动力学方法,建立了综合治理的动态仿真模型,通过对比分析,提出了可供选择的治理方案。     

基于侵蚀力学机制的流域土壤侵蚀模型研究—以长江三峡库区王家桥流域为例

根据王家桥流域观测资料及人工降雨实验成果,从侵蚀力学机制出发,严格区分了坡面侵蚀与流域侵蚀两个不同的概念,建立了坡面侵蚀模数和流域侵蚀模数。计算结果表明,流域内坡面侵蚀只占流域侵蚀模数的7.1%～11.7%,流域侵蚀物质主要来源于沟蚀、部分重力侵蚀。因此在王家桥流域如何开展水保工作是一个值得深思的问题。     

GIS支持下三峡库区典型小流域土壤养分流失量预测

土壤养分流失是农田非点源污染的主要形式。以长江三峡库区典型小流域为研究区域 ,根据土壤养分流失规律与土壤侵蚀量预测结果 ,以及表土中养分含量 ,像元土壤侵蚀量和泥沙对养分的富集比 ,建立了可与 GIS结合的侵蚀泥沙携带养分量预测模式。运算结果显示 ,小流域有机质、氮、磷、钾流失总量分别为 5 0 9.8,47.1,14.6 ,1137.4t,平均 30 .5 ,2 .8,0 .9,6 8.1t/ km2。根据正常施肥水平及有机质累积率草拟的土壤养分流失分级标准来判断 ,三峡库区小流域养分流失量 ,以严重流失占的比例较大。     

黄土高原泾河流域水沙特征分析

以黄土高原中部泾河及其7个子流域为研究对象，选取了流域内8个水文站33年的径流量和输沙量以及30年的降水量数据，同时对2002年的MODIS数据进行分类处理，分析了不同流域的水沙变化差异及其地表覆被类型特征。结果表明：泾河流域近50年来的输沙量略有下降，而径流量减少比较显著；泾河及其7个子流域的水沙变化和9种地表覆盖类型空间格局的差异显著；地表植被类型较好的流域，径流量相对较大而输沙量相对较小，且径流量与输沙量的起伏波动较小，反之则流域的径流量相对较小而输沙量相对较大，且径流量与输沙量的变化明显。     

泾河流域植被景观格局对流域径流的调节作用

对黄土高原腹地泾河流域12个子流域植被景观格局和流域径流动态的关系进行了探讨。结果表明景观层次上植被的整体空间格局对流域径流动态有着如下调节作用:(1)泾河流域4种植被景观类型中,森林灌丛植被景观流域年径流量最大,径流年内分配比较均匀,但年际变化很大;其次为复合植被景观,农业植被景观流域径流量较小,且主要集中在汛期;草地植被景观流域径流极小,主要发生在汛期的7~8月份,年际变化比较小。(2)在主要植被景观指数中,景观破碎度、景观多样性与流域径流正相关,景观聚集度、景观优势度与流域径流负相关,景观形状与流域径流相关不显著。(3)结构复杂的植被景观对流域径流具有较好的调洪补枯作用。随着景观破碎度和景观多样性的增大,流域径流年内分配趋于均衡;而随景观聚集度的增大,流域径流年内分配则趋向集中,景观形状对流域径流调节作用不明显。(4)多样性高的植被景观可降低极端径流出现,维持流域生态系统的稳定性。     

神木试区环境地貌特征

根据野外考察获取的大量资料,着重对试区区域环境地貌形成、演化过程、地貌的形态组合特征进行了详实的分析和探讨。并在此基础上,对于六道沟流域水系形成的年龄进行推算,得出现代地貌和水系是在中更新时期距今约148～46万年期间形成的古沟谷基础上,经过后来堆积和切割重新演化形成,而且处于发展之中。同时还就一些特殊的地貌现象进行了探讨。最后,文章就现代地貌发育与地表侵蚀的关系以及控制沟道侵蚀的途径进行了评述。     

神木六道沟气候及地面组成物质特征对侵蚀产沙影响分析

在野外调查与试验研究的基础上,分析了六道沟及其相邻流域降雨、径流、气温、风力等气候因素及地面组成物质特征对侵蚀产沙的影响。认为暴雨强度大,疾风多、植被少,地面组成物质复杂松散,以及不良的土壤理化特性,是该区侵蚀产沙特别强烈的根本原因,该区的侵蚀具有复杂多样的特殊性,在时间与空间上差异较大,分布不均;地面物质粗、产沙量大、是粗沙的主要产区;掌握侵蚀特点,控制风沙直接入沟,入河及坡耕地的改造,防治沟头,沟壑崩塌,扩大草灌,发展多样性农业为治理重点。