陕北黄土区陡坡地人工植被的土壤水分生态环境

通过定点土壤水分测定与对比分析，研究了陕北黄土区35～45°陡坡地人工植被的土壤水分亏缺状况、年际、年内动态变化规律、干燥化特征及其补偿恢复特征。结果表明：陡坡地多年生人工植被的土壤水分亏缺极为严重，贫水年0～10m土层贮水量仅相当于田间持水量的26．2％～42．0％，丰水年贮水量也仅占田间持水量的27．0％～43．3％；亏缺次序为：柠条〉刺槐〉苜蓿〉侧柏〉杨树〉油松〉荒坡〉杏〉枣〉农地。年际间同一植被土壤水分含量的变化主要发生在200cm以上土层内，变异程度随土壤深度的增加而减弱。同一生长季，各种植被0～120cm土层含水量的变异系数都较大，但植被间差异较小；120cm以下土层，变异系数较小，但植被间差异较大。陡坡地多年生植被均有永久干层存在，但深层土壤干燥化强度因植物种类和生长年限而存在明显的差异。雨季土壤水分的补偿和恢复深度为1．0～1．4m，但不同植被的土壤贮水增量和补偿度有较大差异。同一植被丰水年的雨水补偿深度比干旱年可增加60cm以上，5m土层贮水增量增加3倍以上。在自然降雨条件下，陡坡地多年生人工植被的土壤贮水亏缺状况不能得到改善，土壤干化现象也不可能有所缓解。

水分生态环境对刺槐细根垂直分布的影响

采用土钻法,对安塞县和长武县的刺槐细根面积垂直分布特征进行调查研究,结果表明:(1)刺槐细根的垂直分布与水分生态环境密切相关,现存的细根密度是对具体生境逐步适应调整的结果。(2)刺槐在遗传特性上表现为深根性树种。刺槐细根的垂直分布除了受树种遗传特性的影响,很大程度上受水分生态环境的影响。(3)刺槐细根的垂直分布区域与降雨的补偿深度基本一致,如果土壤中的水分得不到很好的补偿,将对刺槐的生长造成很大影响。因此,黄土高原营造人工林,应充分考虑降水对土壤含水量的补偿深度和补偿程度,以水分生态环境中所能容纳的适宜细根密度为依据确定造林密度,才能使树木达到最大生产力。

黄土高原植被恢复的水分生态环境研究

水分是制约黄土高原地区植被恢复与生态环境重建的决定性因子 .在分析现有关于该区植被建设中的水分生态环境的各项研究的基础上 ,从水资源、土壤水分背景、土壤水分动态、土壤干层、土壤水分的林草生产力、水分性质分区、林草对策等 7个方面 ,对黄土高原的土壤水分环境进行了阐述 ,针对该问题的研究现状 ,指出其中存在的问题 。

Advance and application of lake optics research

The mainstreams of lake optics research in recent decades include optical properties of lakewater, observation, transmission and calculation of underwater radiation, determination of absorption coefficient S of yellow substance, influence of UV-B radiation of lake primary productivity by bio-optical model. Major lake optics applications, such as calculation of lake primary productivity and chl-a, analysis of factors restricting eu- trophication, and protection against lake eutrophication are summarized.

Influence of litter layer on ecological environment in northeastern leymus chinensis grassland of China

In this paper, we adopted simulation method to discuss influences of litter layer on plants habitat in grassland. Results indicated that ground surface evaporation, soil moisture, surface temperature, soil pH, soil bulk density and soil porosity were all strongly related to the litter quantity. Potassium （K） and organic materials in the soil covered by litter layer were higher than those in the soil uncovered by litter layer. With 100 g.ln-z increase of litter, the percentage of organic materials increased by 17.9%, nitrogen （N） increased by 7.6%, phosphor （P） increased by 26.4%, and K increased by 3.8%. With the litter accumulation amounting up to 600 g-m-2, the percentage of organic materials increased by 1.8 times, N increased by 81.5%, P increased by 1.8 times and K increased by 26.4%. According to the expected coefficient method of optimization, a mathematical model was established about the optimal accumulation quantity of litter.