渭河流域长时间序列NPP估算及时空变化特征分析

植被净初级生产力（net primary production，NPP）是生态系统碳循环及能量流动的关键参数，也是生态系统可持续发展的重要生态指标，分析植被NPP的时空变化特征对于区域碳循环研究具有重要意义。利用MODIS反射率数据（MOD09A1）、MODIS NDVI数据（MOD13A3），基于CASA模型估算2001-2018年渭河流域植被NPP，分析植被NPP的时空变化特征，并探讨不同植被类型间NPP的差异性以及高程变化对植被NPP的影响。研究表明:1）2001-2018年，渭河流域植被NPP总体呈波动式增加趋势，年均NPP处于292.59~444.90 gC·m²，年际增加速率为6.23 gC·m²；流域植被NPP具有明显的空间异质性，表现为中东部的六盘山、子午岭和南部秦岭等地区较高，西部和北部的黄土高原地区较低。2）18 a来，除常绿针叶林外，其余植被类型NPP均呈增加趋势。不同植被类型的年均NPP的差异表现为落叶阔叶林（625.70 gC·m²）>常绿针叶林（390.16 gC·m²）>草地（368.49 gC·m²）>农田（344.65 gC·m²）>灌丛（340.17 gC·m²）。3）不同地形条件下植被NPP具有一定差异性，在900~1 300 m（农田、山地落叶小叶林），植被NPP最高；1 700~1 900 m及3 500 m以上区域（稀树灌木草原、灌木），植被NPP最低。     

年际尺度上土地覆盖类型时空分异及其对气候和地形的响应

为了更加深刻地理解气候和地形条件对土地覆盖的作用机理,该研究以2001年-2009年逐年的MODIS Land Cover(MCD12Q1)为主要数据源,参考中国土地覆盖分类体系整合国际上通用的5种(IGBP、UMD、LAI-fPAR、NPP和PFT)土地覆盖分类体系,分析年际尺度上中国西北干旱半干旱地区的土地覆盖时空分异及其对气候和地形的响应。研究结果表明:IGBP较其他4种更适合年际尺度上干旱半干旱地区土地覆盖的时空分异研究。2001年-2009年,5种分类体系中农田和草地增加,水体湿地和荒漠减少,聚落保持不变,森林有增有减,并且土地覆盖类型间相互发生转换,其在空间上的转移与干旱半干旱地区的自然条件变化和人类活动相适应。6种土地覆盖类型对自然条件的响应与光、热、水在时空格局上的分配以及人类活动作用的强弱相一致。研究结果可为区域或全球土地利用和土地覆盖研究提供参考。     

温带沙漠土壤空间分布的尺度依赖性研究

Spatial variation is a ubiquitous feature of natural ecosystems, especially in arid regions, and is often present at various scales in these regions. To determine the scale dependence of the heterogeneity of soil chemical properties and the dominant scales （factors） for soil heterogeneity in arid regions, the spatial variability of soil resources was investigated in the Gurbantunggut Desert of Central Asia at the scales of 10-3, 10-2, 10-1, 100, 101, 102, 103 and 104 m （from individual plant to population or community to ecosystem）. Soil chemical properties including pH, electrical conductivity （EC）, organic carbon, total nitrogen, available nitrogen, total phosphorus, and available phosphorus were considered in the investigation. At a scale of 10-1 m, which represented the scale of individual plant, significant enrichment of soil resources occurred under shrub canopy and ＂fertile islands＂ formed in the desert ecosystem. Soil EC exhibited the largest heterogeneity at this scale, indicating that individual plants exerted a great influence on soil salinity/alkalinity. Soil nutrients exhibited the greatest heterogeneity at a scale of 102 m, which represented the scale of sand dune/interdune lowlands （between communities）. The main important factors contributing to soil spatial heterogeneity in the Gurbantunggut Desert were individual plants and different topographic characteristics, namely, the appearance of vegetation, especially shrubs or small trees, and existing sand dunes. Soil salinity/alkalinity and soil nutrient status behaved differently in spatial heterogeneity, with an inverse distribution between them at the individual scale.     

An arthropod community beyond the dry limit of plant life

Water availability, which enables plant growth and animal activity, regulates dryland ecosystem function. In hyper-arid ecosystems, rain cannot support vascular plant growth. Therefore, hyper-arid vegetation is restricted to the lower topography, where runoff accumulates. Typically, food resources originating from areas of dense vegetation are dispersed across the desert floor, enabling animal life in areas lacking vascular plant growth. However, certain regions, such as the hyper-arid upper topography, may be devoid of plant-derived food resources. The present study examined arthropod activity in the upper topography of a hyper-arid desert, in comparison with arthropod activity in the lower topography. Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel, vegetated riverbeds. Surprisingly, the study revealed dense arthropod communities in the barren upper topography. Arthropods collected in the upper topography represented 26% of total arthropod abundance. In addition, the overlap between arthropod identity in the ridges and wadis(i.e., riverbeds) was low, and certain arthropods were strongly affiliated with the ridges. The upper topographic communities included high numbers of silverfish(Zygentoma: Lepismatidae), malachite beetles(Psiloderes), and predatory mites(Acari: Anystidae), and these arthropods were present at various life stages. It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area. These results raise the possibility that other food sources, independent from vascular plants, may play a significant role in the life history of hyper-arid arthropods.     

基于GIS的陕西省定边县耕地种植玉米适宜性评价

【目的】对陕西定边县耕地种植玉米的适宜性进行评价,旨在为耕地的科学管理及可持续利用提供参考依据。【方法】以地处黄土高原与鄂尔多斯荒漠草原连接的陕西省定边县为例,通过野外调查与室内分析,在GIS技术的支持下,将土壤图、土地利用现状图和行政区划图叠加确定评价单元,结合层次分析法、模糊评价法等数学方法,从土壤管理、土壤养分、土壤性质、立地条件4个方面共选取10项指标,对定边县耕地种植玉米适宜性进行了定量评价,并分析了影响该地区耕地种植玉米适宜性的主要指标。【结果】陕西省定边县耕地种植玉米适宜性可分为最适宜、适宜、次适宜和不适宜4个等级,玉米种植最适宜区、适宜区、次适宜区和不适宜区的面积分别为53 185.64,121 634.76,57 681.57和10 801.20hm2,分别占耕地总面积的21.86%,49.99%,23.71%和4.44%;通过层次分析法的组合权重可知,坡度、地貌类型、灌溉能力、土壤质地、有机质和碱解氮为影响该地区耕地种植玉米适宜性的重要指标。【结论】陕西省定边县耕地总体上比较适宜种植玉米,次适宜耕地可以通过改造提高种植玉米的适宜性,不适宜的耕地可以从事其他作物的种植或用作他用。     

Influences of landform as a confounding variable on SOM-NDVI association in semiarid Ordos Plateau

Soil organic matter(SOM) plays an important role in maintaining vegetation cover and thus mitigating land erosion of fragile terrestrial ecosystems such as in the Northern Ordos Plateau of China(NOPC).However,little information is available on whether and how SOM varies spatially as an intrinsic characteristic of landform in NOPC.The objective of this study was to examine the spatial associations of SOM with landform and vegetation cover.The study was conducted in a 23,000-km2 area within NOPC because this area has landforms of mobile dunes(MD),flat dunes(FD),grassy sandy land(GSL),flat sandy bedrocks(FSB),and swamps and salt lakes(SW),which are typical landforms in semiarid ecosystems.SOM was determined using a standard laboratory analysis method for 5 cm topsoil samples collected at 72 locations across the study area.In addition,the 250 m Multitemporal Moderate Resolution Imaging Spectroradiometer(MODIS) imageries taken in the period from August 2006 to August 2010 were used to extract Normalized Difference Vegetation Index(NDVI) which in turn was used as the surrogate of vegetation cover.Classic and geostatistical methods were used to compare SOM concentration across different landforms.The results indicated that an area with a greater value for NDVI(i.e.better vegetation cover) tended to have a higher SOM concentration regardless of the landform types.However,the association between SOM and NDVI varied from one landform to another.The SW and GSL had a highest SOM concentration,while MD had a lowest concentration.For the study area as a whole and the FD,GSL,and MD,SOM was found to be the sole function of NDVI,whereas,for the FSB,SOM was influenced by several intrinsic variables,namely ground surface altitude,slope,and aspect,as well as NDVI.SOM for the SW landform was found to be a function of NDVI.Furthermore,SOM and NDVI exhibited a consistent spatial pattern of increasing from north to south and from west to east.The highest SOM concentration of 3.5% occurred along an east-westward belt,which is adjacent to water pathways,in the mid part of the study area.     

青海省自然生态分区初探

自然生态分区是生态环境规划和管理的基础。文章就当前青海省生态环境管理中分区不统一、特点各异等问题进行分析和比较,提出全省生态分区意见。通过对全省有关区划工作的结果进行分析比较,提出将青海省3大地貌类型划分为10个自然生态区(一级区)。     

基于GIS的亚热带典型地区土壤有机碳空间分布预测

Spatial distribution of organic carbon in soils is difficult to estimate because of inherent spatial variability and insufficient data. A soil-landscape model for a region, based on 151 samples for parent material and topographic factors, was established using a GIS spatial analysis technique and a digital elevation model (DEM) to reveal spatial distribution characteristics of soil organic carbon (SOC). Correlations between organic carbon and topographic factors were analyzed and a regression model was established to predict SOC content. Results for surface soils (0-20 cm) showed that the average SOC content was 12.8 g kg^-1, with the SOC content between 6 and 12 g kg^-1 occupying the largest area and SOC over 24 g kg^-1 the smallest. Also, soils derived from phyllite were the highest in the SOC content and area, while soils developed on purple shale the lowest. Although parent material, elevation, and slope exposure were all significant topographic variables (P < 0.01), slope exposure had the highest correlation to SOC content (r = 0.66). Using a multiple regression model (R² = 0.611) and DEM (with a 30 m × 30 m grid), spatial distribution of SOC could be forecasted.     

模拟降雨条件下流域地貌动态变化过程研究

通过室内模拟实验对降雨侵蚀条件下流域地貌变化过程进行了研究，研究表明，单位降雨量所产生的流域表面面积、沟道投影面积和流域体积的变化量在整个流域发育过程中呈现出一定规律性，沟道投影面积和流域体积均表现为先逐渐增加，达到一定程度后又逐渐下降，而表面面积则表现为先逐渐增加，达到一定程度后则处于上下波动的状态。     

园林绿地中微地形处理研究

依据园林规划设计的基本原理就公共绿地，居住区绿化等不同绿地类型的微地形处理手法进行探讨，提出在园林绿化中一些常见地形的处理原则。