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。     

武夷山国家级自然保护区植被类型的地形分异

为探讨地形对中亚热带森林植被分布的影响，在利用地理信息系统技术提取研究区域各地形因子和植被景观信息基础上，分析了福建武夷山国家级自然保护区植被景观和地形的总体特征，揭示了植被分布在地形上的变异规律。结果表明，区内各植被类型面积分布不均，地带性植被常绿阔叶林和针阔混交林是主要植被类型，占总面积的70．53％。在海拔的影响下，保护区植被有明显的垂直分带现象。坡度和坡向对不同植被类型分布影响程度不同，只对中山草甸、阔叶矮曲林和人工植被等3种植被类型有较显著影响。从各植被类型在海拔、坡度和坡向上的变异系数看，海拔因子对植被类型的分布影响最大。图4表3参16     

黄土残塬沟壑区坡度和坡长对土壤侵蚀的影响分析

该研究以黄土区坡地的坡长与坡度对于土壤侵蚀的影响为研究内容,旨在为因害设防,更好的治理水土流失,对黄土高原坡地综合治理提出理论依据和切实可行的实践指导. 根据在山西省吉县黄土残塬沟壑区长期定位水土流失观测与调查资料,并结合以往关于黄土区的研究成果分析了坡长和坡度与侵蚀的关系,研究表明:随坡长和坡度的增大,径流增大,侵蚀量越大,侵蚀模数增大;年侵蚀模数与坡长呈正相关关系;随着坡长增大,细沟侵蚀和浅沟侵蚀明显增强;坡耕地坡长最好小于15 m.     

Spatial Variability of Irrigated Corn Yield in Relation to Field Topography and Soil Chemical Characteristics

Corn yield, topography and soil characteristics were sampled on a 26 ha area of a centre pivot irrigated cropland. The aim of the study was to determine relationships between corn yield, field topography and soil characteristics. The study was carried out in the Alentejo region of Portugal. Corn yield was measured with a combine harvester fitted with a grain-flow sensor and positioned by means of the Global Positioning System (GPS). A grid-based digital elevation model (DEM) with 1-m resolution was constructed and several topographic attributes were calculated from the DEM: the local slope gradient (S), profile curvature (Curv), specific catchments area (SCa), and a steady-state wetness index (W). Yield and topographical attributes were computed for areas of radius 5, 10, 25 and 50 m, being considered its maximum, minimum, range and average values. The soil was systematically sampled with a mechanical probe for a total of 109 soil profiles used for analysis of the following soil superficial (<0.30 m) characteristics: extractable phosphorous (P₂O₅) and extractable potassium (K₂O), soil pH, cation exchange capacity (CEC) and exchangeable bases. With centre pivot irrigation systems, the Wave₅₀ index was shown to be useful for the identification of field areas in which low corn yields may be due to lack of water. At the same time, SCa was found to be useful for the identification of field areas in which low yields are due to excess water and drainage problems. Higher positive correlation between pH, Ca and Curv were observed; calcium concentration was found on the transition areas between flat surfaces to concave ones, while lower values were detected in convex and concave areas. Topographical indexes, namely Wave₅₀, SCa and Curv, can be especially helpful in site-specific management for delineating areas where crop yields are more sensitive to extreme water conditions.     

Assessment of soil texture class on agricultural fields using ECa,Amber NDVI,and topographic properties

Soil texture (ST) is relatively stable over time, although it may change due to erosion, clay eluviation, and other processes. Soil texture affects soil quality, productivity and management. Therefore, indirect, accurate methods for assessing of soil texture classes (STCs) are needed in agricultural practice. A study was performed on four production fields in northern and central Poland to compare the fitting performance of STC models based on apparent electrical conductivity (ECa), topographic properties (elevation, slope gradient and wetness index) and Amber NDVI measurements. One common and accurate indicator of STCs was not found for all study fields. On average, ECa was most accurate in indicating areas of different STCs within the fields, but it tended to overestimate the size of sandy areas on loamy fields and vice versa. The accuracy of STC assessment using ECa measurements may be biased due to imperfect soil drainage, high elevations, which increase evaporation and STC variation with depth. STC assessment using Amber NDVI measurements may be useful, particularly on flat and sandy fields, but the results are affected by the same factors as ECa, and additionally by crop growth stages and by the weather conditions in the period preceding the measurements. Despite the good quantitative results of the STC assessment by elevation (one field) and by the topographic wetness index (another field), both terrain attributes failed to accurately indicate the distribution of some STC areas within each field. Therefore, in landscapes developed from deposits of the last glaciation relevant ST differences might not sufficiently be detected by the analysis of terrain attributes alone. The selection of STC predictors and evaluation of the assessment quality must consider both the quantitative indicators such as correlation and determination coefficients describing relationships between ST and ECa, NDVI and topography and percentage of a field area with accurately indicated STC and the distribution of areas with different STCs within a field. The use of ECa, NDVI values, and topographic properties for STC assessment may be useful in reducing costs of soil sampling and analysis, but cannot replace it.     

虚拟农场地形地貌建模研究

提出了利用导入农场地形轮廓、合理规划地形高度图的方法建立可动态更新的统一数据地形,并通过合理设计地形纹理,使纹理贴图与地形有机结合,实现了逼真的地表效果。在农场地貌设计中,为了解决虚拟农场中无法实现按农艺要求种植植物的问题,提出了在虚拟场景编辑模式下建立自定义插件,完成批量精确定位种植植物的方法,实现了虚拟环境下种植农作物的自动化、精确化。以上方法建立的地形及地形上的植物可动态实时更新,为后期进一步开发农场仿真操作提供了技术保障。     

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。     

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.     

黄河三角洲不同地表覆被类型和微地貌的土壤盐分空间分布

掌握不同地表覆被类型和微地貌特征下的不同深度土壤盐分空间分布规律，对土壤盐渍化防治具有重要意义。该研究以黄河三角洲入海口为研究区，在分析不同深度土壤全盐量、盐基离子（Ca2+、Mg2+、Na+、SO42-、HCO3-、Cl-）空间变异特征的基础上，通过单因素方差分析不同地表覆被类型和微地貌特征下该区土壤盐分的差异，并通过地理探测器分析地表覆被类型、微地貌对土壤盐分的交互影响。结果表明：1）表层土壤Mg2+变异系数达到1.010 8，为强变异性，其余盐基离子均为中等变异性，且均有强烈的空间相关性，全盐量与盐基离子均呈现沿海向内陆降低的趋势，约有42.57%的地区为轻度盐化土；2）不同地表覆被类型间土壤全盐量与Na+、Cl-具有显著差异；3）不同微地貌类型间Na+、Cl-具有显著差异；不同海拔的深层土壤Na+具有显著差异；4）海拔对土壤全盐量与Na+的解释力最强，地表覆被类型对土壤Cl-的解释力最强；5）坡向和海拔对土壤盐分的交互作用最强烈，q值在0.545～0.708之间，其次是地表覆被类型与坡向，q值在0.521～0.613之间。氯化钠主导该区域土壤盐分空间变异，不同地表覆被类型和微地貌特征下均呈显著差异，表层土壤盐分明显高于深层，坡向与海拔之间的交互作用能够较好地解释该地区土壤盐分空间分布。     

山东省灌溉农业分区自然特征影响因素研究

山东省全区地形地貌与气候条件差异很大,由地形地貌与气候条件构成的自然特征对灌溉农业分区的制约首当其冲。论文首先分析了山东省的地形地貌,以各种地形面积百分比作为相应指标值;并通过对比分析选择以"积温计算法"表达的干燥度作为山东省气候条件的指标值;最后,通过分析山东省的地形地貌及2000-20005年各地市的干燥度,对不同地区发展节水灌溉进行了讨论。相关指标值的确定,为灌溉农业分区和实施适宜的节水技术提供了理论支持。