森林火行为的影响因素研究

文章阐述了森林林火行为的概念、研究的意义,分析、总结了森林火行为影响因素,可归纳为可燃物、地形、气象条件和人为措施等,并展望了未来的研究方向,不仅对单个影响因素进行研究,还要深入研究各因素间的相互作用,耦合机制等,并进行长期的定位研究。     

东北典型黑土耕层颗粒组成与腐殖质层厚度的关系

土壤颗粒组成是影响土壤肥力的主要物理性质之一.为了了解东北黑土腐殖质层厚度与土壤颗粒组成的关系,通过在东北典型黑土区选择典型坡面,调查不同地貌部位土壤腐殖质层厚度,测定耕层土壤的颗粒组成,分析腐殖质层厚度和耕层土壤颗粒组成随地貌部位的变化趋势,以及土壤颗粒组成与腐殖质层厚度的关系.结果表明:土壤腐殖质层厚度由上坡至坡脚...     

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.     

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.     

基于CSLE模型的神木市土壤侵蚀模数计算

基于GIS、RS平台,采用CSLE模型,依据全国气象站网2001—2017年日降雨数据、1∶50万神木市土壤属性空间分布图及工程措施数据、10 m分辨率DEM数据、土地利用现状和植被覆盖度数据、Landsat影像,对神木市2010、2015、2017年土壤侵蚀模数变化特征进行分析。结果表明:3期神木市土壤侵蚀模数分别为1252.5、1216.68、1976.07 t/(km²·a),呈先减少后增加的趋势;随植被覆盖度增加,3期不同植被覆盖度区域土壤侵蚀模数和侵蚀量均呈先增后减的趋势;随海拔升高,3期不同高程带内土壤侵蚀模数均呈逐渐减小的趋势;随坡度增加,3期不同坡度级别区域土壤侵蚀模数均大致呈增加的趋势;此外,暴雨是导致神木市土壤侵蚀增加的重要原因,在水土保持工作中应增加应对暴雨的措施。     

Assessing the impact of phosphorus cycling on river water P concentration in Hokkaido

Abstract

We estimated the phosphorus (P) budgets for all 212 cities, towns and villages of Hokkaido, Japan. We also carried out water sampling from all major rivers flowing in the respective areas during the snowmelt season and measured total P (TP) concentration. Surplus P in the agricultural land was estimated by subtracting the amount of crop uptake from the input sources, such as the amount of chemical and compost fertilizers, crop residues, rainfall and irrigation. The livestock excreta P not utilized on farmland was assumed to be disposed P. Total P concentrations in most of the river water ranged from undetectable to 1 mg L^?1, rarely reaching up to 2.32 mg L^?1, and the areas surrounding the Funka Bay had comparatively higher concentrations. More than two-thirds of the areas had surplus P in farmland ranging from negative values to 30 kg ha^?1 of farmland, and areas with mixed farmland and livestock husbandry had higher surplus values ranging from 31 to 72 kg ha^?1, indicating that the source of the residual P was applied chemical and manure fertilizers. Total P concentration in river water was not correlated with the proportion of upland field and urban area or with the farmland surplus P resulting from the P cycling and the municipal waste P that mixes into the river water. However, TP concentration was positively correlated with the proportion of Andisol area occupied by farmlands (r = 0.25, P < 0.01). The TP concentration was also correlated with the topographic factors in areas (r = 0.49, P < 0.01) that possess more than 50% Andisols in farmlands. Multiple regression analysis showed that TP concentration was best explained by a combination of disposed excreta, the Andisol area occupied by farmland, the application rate of chemical fertilizers and topographic factors (r ² = 0.21, P < 0.001). Thus, P losses from farmlands to river water during the snowmelt season could mainly be attributed to fertilizer management and soil type along with the topographic condition of the area.     

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。     

非线性光学晶体KTiOPO4(KTP)的缺陷研究

利用同步辐射白光X射线形貌术和化学腐蚀法,研究了熔盐法和水热法生长的KTP晶体中的缺陷.其中熔盐法生长KTP晶体分别采用固相和液相2种方法合成生长的原料.实验结果发现KTP晶体中的生长扇形界、生长条纹和位错等缺陷.