林地水土保持功能持续提高的机制及对策

通过对不同林地水土保持功能分析得出,其发展过程可分为成长期、成熟期和减退期,并定义成熟期为可持续发展期。分析了影响水土保持功能持续提高的环境分配系数r和环境利用系数k,认为r是林地中光、水、肥分配的参数,k为光、水、肥利用的参数。林地水土保持功能的持续提高,应通过调整r和k,即调控林地的树种组成、林分层次和林分密度,形成合理的林分结构,保持成熟期的持续发展。并在此基础上提出了林地水土保持功能持续提高的相应对策。     

Simulating the vegetation-producing process in small watersheds in the Loess Plateau of China

Small watersheds are the basic composition unit of the Loess Plateau in China. An accurate estimation of vegetation net primary productivity (NPP) is of great significance for eco-benefit evaluation in small watershed management in this region. Here we describe the development and testing of a vegetation-producing process model (VPP) of a small watershed in the Loess Plateau. The model couples three modules: radiation adjustment; soil hydrological processes; and vegetation carbon assimilation. Model validation indicates that the VPP model can be used to estimate the NPP of small watersheds in the region. With the VPP model, we estimated the spatial NPP distributions in the Yangou watershed for 2007. The results show that in the Yangou watershed the NPP is relatively low, averaging 168 g C/(m 2 ·a). Trees and shrubs have a higher NPP than crops and grasses. The NPP is larger on the partly shaded and shaded slopes than on the partly sunny and sunny slopes. The NPP on the slopes increases gradually on 0-20° slopes and decreases slightly on slopes steeper than 20°. Our simulation indicates that the vegetation type is the most important factor in determining the NPP distribution in small watersheds in the Loess Plateau.     

地下滴灌棉花栽培试验与技术研究

根据新疆兵团农五师九十团8hm^2地下滴灌棉花栽培、灌溉和施肥等方面的试验研究,地下滴灌与地面滴灌比较,无论投入产出和作物的长势,地下滴灌都比地面滴灌优越。地下滴灌比地面滴灌工程设备、材料费低0．15297万元／hm^2,降低年运行费用841．8元／hm^2。     

坡度对东北黑土流失影响的研究

通过室外人工模拟降雨的方法,得出了在不同坡度、降雨量和降雨强度时,不同植被覆盖度的流失泥沙颗粒组成、黑土地表的径流量以及土壤含水量的相应变化。     

miRNA在植物适应土壤胁迫中的作用

基本养分缺乏和含有有毒元素的土壤全球范围内广泛存在,严重影响作物生产。为了减少土壤胁迫的伤害,植物进化了适应不良土壤环境的机制。研究发现植物miRNA在植物适应土壤胁迫中具有重要作用。总结了在植物响应土壤养分缺乏胁迫和土壤元素毒害胁迫中植物miRNA的作用,强调植物miRNA在胁迫响应调控网络中的作用,提出改良植物不良土壤适应能力的思路。     

Distribution of biomass and carbon in even‐aged stands of Norway spruce (Picea abies (L.) Karst.): A case study on spacing and thinning effects in northern Denmark

The main objective of this case study was to explore the possible influence of forest management on the levels and distribution of biomass and carbon (C) in even-aged stands of Norway spruce [Picea abies (L.) Karst.] in Denmark. Data originated from a long-term thinning experiment and an adjacent spacing experiment at stand ages of 58 and 41 years, respectively. Biomass of 16 trees from different thinning and spacing treatments was measured or partly estimated, and soils were sampled for determination of C stocks. All trees in each plot were measured for stem diameter and some for total height, to allow for scaling-up results to stand-level estimates. For trees of similar size, foliage biomass tended to be higher in the spacing experiment, which was located on slightly more fertile land. Foliage biomass increased with increasing thinning grade, but the effect could not be separated from that of tree size. At stand level, foliage biomass tended to increase with increasing spacing as well as with increasing thinning grade. For branchwood, stems and roots (including below-ground stump), the biomass increased with increasing tree size and stand volume at tree and stand level, respectively, but no differences between stands, spacings or thinning grades were observed, apart from that expressed by tree size or stand volume. At stand level, C stocks of all biomass compartments decreased with increasing thinning grade, while the distribution between compartments was hardly influenced. The ratio between above-ground and stem biomass was about 1.21 at stand level, while the ratio between below- and above-ground biomass was about 0.17. Thinning influenced the C stock of the forest floor and mineral soil oppositely, resulting in no effect of thinning on total soil C.     

Management of Nitrogen-Rich Legume Cover Crops as Mulch in Traditional Olive Orchards

A low-input agricultural system needs a natural source of nitrogen (N). Legume species can fix great amounts of N that can be subsequently used by a nonlegume crop. In this study three legume cover crops were grown in traditional olive orchards in northeastern Portugal from October 2009 to May 2010, and the aboveground biomass was mechanically destroyed and left on the ground as a mulch. In the following growing season, from October 2010 to May 2011, two nitrophilic plant species were grown in circular microplots of 154 mm surrounded by polyvinyl chloride rings to assess the soil N availability. The N fixed by the legume cover crops, estimated by the difference technique, was shown to vary from 79.7 to 187.5 kg N ha^?1. The nitrophilic plant species identified a small peak of soil available N in the autumn of 2010, probably resulting from the mineralization of the root system of the legume species. In the next spring, the increase of soil-available N in the plots where the legume cover crops had been grown, in comparison to the control plot, was residual. The great amounts of N present in the mulched materials seem to disappear without having entered the soil. Mulching with high-N content biomass may be troublesome due to the high risk of N losses probably by ammonia (NH₃) volatilization.     

中国水土流失问题的初探

长期以来,水土流失直接威胁着人们赖以生存的环境,在所有的生态破坏中,水土流失称之为“环境破坏第一杀手”。针对我国山地丘陵面积大、地质条件复杂、人为破坏加速、水土流失严重的实际情况,通过丰富的历史资料和整治经验及野外工作所积累的大量数据分析,以生态恢复学为指导,总结了水土流失的基本特点,研究了水土流失治理与经济可持续发展的关系,探讨了水土流失给生态安全造成的巨大危害,展望了水土保持的预期目标,根据中国的实际情况,提出了综合治理的基本思路。