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971.
【目的】揭示内陆河流域集水区土地利用/覆被变化对水文过程的影响及其成因。【方法】基于能够逐年调用土地利用/覆被数据的LU-SWAT模型,并结合控制变量法研究了黑河流域集水区黑河上游1990—2009年土地利用/覆被变化对地表径流、侧向流、蒸散发量、地下径流以及总产水量的影响。【结果】LU-SWAT模型对于黑河上游月、年出山径流模拟结果较好,其月径流模拟的纳什系数为0.93,相关性系数为0.94;其年径流模拟的纳什系数为0.83,相关性系数为0.86。此外,其对各个水文要素的模拟结果符合西北干旱区内陆河流域集水区的水文特征;1990—2001年黑河上游土地利用变化主要表现在林地的减少,而2002—2009年土地利用的变化除了林地和草地的增加之外,还表现在裸地的大面积减少;1990—2001年黑河上游地表径流、侧向流、蒸散发量以及总产水量都呈现增加趋势,而地下径流呈减少趋势,2002—2009年流域地表径流、侧向流、蒸散发量以及总产水量减少,而地下径流量增加。在黑河上游,干旱条件下各水文要素对于土地利用覆被变化的响应更明显。【结论】1990—2001年林地的减少可能是流域地表径流、侧向流、蒸散发量以及总产水量都呈现增加趋势而地下径流呈减少趋势的主要原因。2002—2009年裸地的大面积减少可能是流域地表径流、侧向流、蒸散发量以及总产水量减少而地下径流量增加的主要原因。 相似文献
972.
【Objective】The purpose of this paper is to solve secondary salinization of soil in Northwest China. 【Method】the capillary water rising movement characteristics of layered soil has been analyzed through indoor test. And the variation characteristics of capillary water movement under the influence of common change of layer and thickness of sand layer has been considered in this paper, and functional relationship between groundwater recharge and height of capillary water rising with time changing has been built. Furthermore, contour distribution of groundwater recharge and capillary water rising height has been also comparative analyzed.【Result】There was a very significant positive correlation between the horizon and the volume constant and the height constant (P<0.01). And there was a significant negative correlation between the horizon and the stable recharge rate of groundwater and the rate of steady increase of capillary water (P<0.05). There was a significant negative correlation between the thickness of sand layer and stable recharge rate and steady rising rate(P<0.05). When the duration of the capillary water height was rising was 0~4 days, the sandy layer was 30~50 cm, the thickness of sand layer was 0~15 cm, which has a significant effect on the change of groundwater recharge and height of capillary water. When the duration of the capillary water height was rising was 4~12 days, the sand layer is distributed in 15~30 cm, the thickness of sand layer was 15~30 cm, which has a significant effect on the change of groundwater recharge and height of capillary water. To summarize, the results of this study were of great significance for the study of water salt movement and soil salinization in layered soils.【Conclusion】The fitting parameters of the function including volume constant (v), stable recharge rate (q*), groundwater recharge time constant (τQ), capillary water rising height (υ), steady rising rate (μ*) and rising height time constant (τh) were determined by the variation of capillary groundwater recharge and capillary water height with time changing respectively. © 2019 Journal of Irrigation and Drainage. All rights reserved. 相似文献
973.
黄土丘陵沟壑区封禁流域立地因子对植物群落特征的影响(摘要) 总被引:2,自引:0,他引:2
[目的]研究黄士丘陵沟壑区封禁流域立地因子对植物群落特征的影响。[方法]通过对陕西吴起县内封禁流域进行植被调查,研究了不同立地类型内植被群落特征和物种多样性的差异。[结果]调查区域内植被群落以旱生草本植物为主,物种组成相对单一,结构简单。地带性植被类型为铁杆蒿(Artemisia sacrorum)+茭蒿(Ar-temisiagiraldii)群落;植物多样性在不同地貌部位表现为梁顶〉沟底〉梁坡〉沟坡,在不同坡向表现为:半阴坡〉阴坡〉半阳坡〉阳坡的顺序;阳坡多样性指数随坡度的增加表现为"S"形变化趋势,37°左右达到最大值。[结论]为黄土丘陵沟壑区的植物恢复提供了理论依据。 相似文献
974.
975.
利用CFD软件,采用Realizable k-ε湍流模型,分别在3种工况下,对1台比转数为71的导叶-蜗壳组合式离心泵的内部流动进行三维非定常数值模拟,获取了离心泵内部流场结构,计算泵的扬程及效率。根据计算结果,分析了叶轮转动位置对泵外特性和内流场的影响。结果表明:当叶轮转动位置不同时,泵扬程、效率随之发生变化,选取某一特定位置处结果作为最终预测结果会产生较大的随机误差;叶轮转动位置的不同,也会对叶轮、导叶、蜗壳流道内的压力场和速度场产生一定的影响。 相似文献
976.
977.
978.
为规范中国标准连续出版物号在期刊中的著录,查阅了31种畜牧、动物医学类期刊,以GB/T 9999-2001《中国标准连续出版物号》为标准,统计不规范著录格式,提出克服、纠正不正确、不规范的著录格式,正确编排印刷中国标准连续出版物号。 相似文献
979.
Jiayao Zhuang Jinchi Zhang Bo Zhang Hongyan Luo Xiaying Huang Jun Fu 《Frontiers of Forestry in China》2009,4(3):323-329
The distribution of root biomass was studied in different soil layers (0–10, 10–20, 20–30, 30–40 cm) by means of a “study
plot” method for various plant species in the Shangshe Catchment area in the Dabie Mountains, Anhui Province. The number and
lengths of root samples were recorded. In each study plot, anti-scourability of soils in corresponding soil layers was measured
with a C.C. Suoboliefu anti-scourability instrument. The results showed the following: 1) The root system was largely distributed
in the 0–40 cm soil layer and the number of roots was the largest in the surface soil layer. Fine roots<1 mm in diameter predominated
in root length. 2) In the same section, the anti-scourability indices of the surface soil layer were larger than those of
other soil layers in the various plant species. The tree root system, especially the fine roots<1 mm in diameter, are highly
instrumental in controlling soil losses. Correlation coefficients of length, number and density of fine roots and the anti-scourability
index were 0.8173, 0.7159 and 0.6434, respectively. The length of fine root is a key factor in the anti-scourability soil
index. This index is closely correlated with the non-capillarity of each soil type, indicating that forests have a strong
soil stabilizing function, because their root systems improve physical soil properties and ultimately are responsible for
the establishment of a biosoil system with an anti-scourability index.
__________
Translated from Science of Water and Soil Conservation, 2007, 5(6): 15–20 [译自: 中国水土保持科学] 相似文献
980.
氮肥水平对多花黑麦草叶绿素及高光谱反射特征的影响* 总被引:1,自引:0,他引:1
叶绿素含量是评价牧草群体长势、估测产量和确定最佳施肥量的重要指标。对不同氮肥水平下多花黑麦草(特高)叶绿素含量及冠层反射光谱特征进行了测试与分析,并研究了高光谱参数红边位置与叶绿素含量的相关性。结果表明:在分蘖期和拔节期施用氮肥(尿素)达到300kg/hm2时,能够显著提高多花黑麦草叶绿素含量;显著降低可见光和近红外区域冠层光谱反射率;并且使红边位置(λr)向长波方向移动。多花黑麦草冠层叶绿素a,叶绿素b,叶绿素a+b与红边位置之间均存在极显著相关性(P<0.01)。利用高光谱参数红边位置可以更加快速、准确地对多花黑麦草冠层叶绿素含量进行估测并筛选适宜施肥量。 相似文献