基于土壤非饱和状态下对水稻田产流模型的改进及验证

水稻灌溉需水量是一个地区农田水利规划、灌溉系统规划的重要参数,也是合理开发利用水资源、水资源调度和实现地区可持续发展的重要依据。在水量平衡的基础上,对蒸散发项和渗漏项的计算方法做出改进,其中对蒸散发项的改进参考了新安江模型中二层蒸散发模型的计算方法,渗漏项的计算在实验的基础上采用半经验半理论的方法改进。最后,结合当地的...     

新疆农业水土资源时空匹配研究

水土资源是农业可持续发展的核心,水资源的合理利用会影响到土地的利用方式。为了分析新疆农业水土资源匹配状况,本文采用农业水土资源匹配系数对2008-2017年新疆14个地、州、市的水土资源时空匹配程度进行研究。研究结果表明:从时间上看,2008年到2017年,新疆农业水土资源匹配系数呈现出增加的趋势。从空间分布上看,北疆地区的农业水土资源匹配系数整体较低,南疆地区的农业水土资源匹配系数较高。通过对2008年和2017年新疆农业水土资源匹配系数的差值对比发现,克孜勒苏柯尔克孜自治州、阿勒泰地区、伊犁哈萨克自治州(直属)、乌鲁木齐市和和田地区的农业水土资源匹配系数的变化较明显;博尔塔拉蒙古自治州和喀什地区农业水土资源匹配系数降低最明显。     

The effect of salinity on corn yield using the CERES-maize model

In most cases, when calculating soil water availability, only thewater content is considered. The effect of salinity on the wiltingpoint is neglected. The objective of this work is to use asimulation model (CERES-maize) in order to predict cornyields as a function of water salinity under severalenvironmental, agrotechnical, and plant characteristics. A modelis presented in which the wilting point is a function of the soilsalt content. At high salinity, the water content at wilting pointis higher than at low salinity, resulting in an insufficient amountof available water and, therefore, a reduced yield. The modelwas used to simulate several theoretical and experimentalsituations for forage corn and grain corn. Simulation resultsshowed that nitrogen fertilization increases the salinity thresholdvalue and the yield sensitivity (rate of yield reduction per unitof salinity). The also showed that forage corn is more sensitiveto salinity than grain corn. If the soil is not leached, a heaviersoil texture has a higher salinity threshold value. On the otherhand, if the soil is leached, the soil texture has no influence onthe salinity threshold value and the yield is less sensitive tosalinity in sandy soils. The determination coefficient (r²= 0.75) indicated that the results of the simulations were in goodagreement with the field data.     

浅析土生空团菌(Cenococcum geophilum)自然侵染率及其与植被、根际土壤因子的关系

为了明确土生空团菌环境适应机理,以内蒙古地带性植被为研究对象,调查和测定了不同森林类型区土生空团菌自然侵染率、植被类型、土壤养分含量变化,探讨土生空团菌自然侵染率与植被、土壤因子的关系。结果表明,从植被类型来看,大兴安岭兴安落叶松、黑里河油松、大青山虎榛子、乌拉山白桦、贺兰山青海云杉等宿主植物土生空团菌自然侵染率均为30%以上,不同森林类型区油松土生空团菌自然侵染率也存在一定的差异。从根际土壤因子分析,土生空团菌自然侵染率与根际土壤有机质(r=0.492)、全氮(r=0.479)呈明显正相关(P<0.05),与根际土壤速效磷(r=0.575)呈极显著正相关(P<0.01)。     

Efficacy of road removal for restoring wildlife habitat: Black bear in the Northern Rocky Mountains, USA

Forest roads reduce habitat quality for wildlife, in part by increasing susceptibility to hunting and poaching. Road removal is an increasingly common strategy for restoring habitat; however, little is known about responses of wildlife to road removal versus other methods of road closure. We assessed effects of different types of road closure (gated, barriered, and recontoured) on black bear (Ursus americanus) frequency and habitat on 18 open and closed road pairs in the western USA. Over 4 years, 44 bears were photographed during 3545 camera-trap days. Bear frequency was significantly higher (2.4 versus 0.6/100 days, respectively) and human frequency was significantly lower (2.4 versus 361.6/100 days, respectively) on closed than on open roads. Additionally, abundance of fall foods was higher (23.9% and 12.8%, respectively) and line-of-sight (a measure of habitat security) shorter (54.9 versus 69.4 m, respectively) on closed compared to open roads. Bears were detected on closed but not on open roads during daytime, suggesting avoidance of humans. Among-road-treatment differences included significantly higher frequency of bears on recontoured than on gated or barriered roads (4.6, 1.6, and 0.5/100 days, respectively), and significantly higher cover of fall bear foods on recontoured than on gated or barriered roads (39.3%, 12.1% and 16.4%, respectively). Frequency of bears was negatively correlated with frequency of humans and line-of-sight distance and positively correlated with abundance of fall foods and hiding cover. Results suggest that while all types of road closure benefit sensitive wildlife, removal by recontour may be the most effective strategy for restoring habitat.