【作者】 尚宗波；

【导师】 高琼；

【作者基本信息】 中国科学院植物研究所 ， 生态学， 2001， 博士

【摘要】 松嫩平原盐碱化草地是我国著名的天然草场，又是东北西部绿色生态屏障，具有较高的经济价值和重要的生态意义。但是由于各种自然因素和人为因素，致使草地出现退化、沙化和盐渍化，尤其是草地盐渍化加重，生态环境日趋恶化。当地地形条件和气候要素是导致草地原生盐碱化的主要原因。而人类对草地的过度使用，如过度放牧和割草等则是导致草地快速次生盐碱化的主要原因，不仅导致土壤的退化，而且引起草地群落发生次生演替过程。在典型的次生演替过程中，常常可以出现羊草（Aneurolepidium chinense）群落、羊草和—虎尾草（Aneurolepidium chinense ＆ Chloris virgata）群落、虎尾草（Chloris virgata）群落、碱蓬（Suaeda glauca）群落等演替阶段。 本文试图建立一个过程模型，来模拟草地的生态学过程机理以及人类过度放牧对草地生态系统的影响。本模型包括5个部分：1）主要气候因子的模拟，2）土壤水分动态的模拟，3）土壤盐碱化动态的模拟，4）草地群落生长的模拟，5）不同放牧强度对草地生态系统的影响评价。以下将对各个部分分别描述。 在气候因子模拟子模型中，给出了影响草地生态系统主要气候因子的种类，并重点介绍了如何利用解析法计算太阳辐射，包括平地和坡地的理论可照时间，天文辐射日总量以及总辐射量。利用改进后的Penman式，模拟了全国的潜在蒸散量，与900多个气象站点的水面蒸发观测资料进行了验证，模拟结果很好。 利用面向对象技术，将土壤水分动力学模型与水分平衡模型相结合，建立了土壤水分动态的物理过程模型。模型以1d为步长，可以模拟多种土壤质地的水分动态。利用松嫩平原4中典型土壤（碳酸盐草甸黑钙土、栗钙土、碱化盐土、草甸碱土）1997年土壤湿度观测资料对模型进行了验证，效果很理想。 在水盐平衡模型和动力学模型基础上建立了物理过程模型，来模拟土壤盐碱化动态。模型以1d为步长，适合于模拟异质性强的多层土壤水盐动态。模拟了1997年羊草及碱蓬群落下的土壤盐分、碱化度、pH值动态，并与实验资 ③＠料进行了比较，”模拟给果可以反映土壤盐分和碱化的季节变化规律。 模型将气候要素、土壤湿度。土壤盐分浓度、碱化度和 pH值作为影响草地群落生长最重要的环境因于，在土壤水分动态和盐碱化动态模型基础上，建立了过程模型来模拟以羊草（．chin洲、虎尾草（ vi刚taX星星草（Puccinellitenuytora砰碱蓬代 glauca）为建群种的 4种植物群落的地上生物量、地下生物量以及枯死生物量变化动态。利用吉林省长岭的气候资料和实验资料，模拟了1991年土壤湿度动态，1991年 4种群落土壤盐分、碱化度和pH值变化动态，以及1991”年4种群落生长动态，井分别利用实验资料进行了验证，模拟效果非 一常理想。 在此基础上，利用模型对不同放牧强度对土壤水分动态、盐碱化动态的影响进行了评价，井探讨了对群落演替和生长的可能影响。模型选择不放牧、轻牧、重牧、过牧。极牧5种放牧强度，利用模型每15天将地上生物量分别去除00／6、25o、50O、7SO和90O，并且相应改变了土壤导水特性来模拟不同的放牧强度。模拟结果表明，重牧、过牧、极牧下土壤湿度显著降低，但在轻牧下土壤湿度略有上升。在不放牧时，土壤以脱盐、脱碱过程为主，而轻牧下脱盐。脱碱过程则会变缓；重牧、过牧。极牧下则以盐碱化为主。不放牧时羊草群落一直古优势，而轻牧下则被羊草一虎尾草群落替代；虎尾草可以忍受轻的盐碱，。囱此在重牧下取代羊草群落成为优势种；在过牧和极牧下。上壤盐碱化非常迅速，最终只有碱蓬可以忍受强度的盐碱，这时草地变为碱蓬群落或光碱斑。不放牧下草地群落生长良好，生物量最大：轻牧下，草地群落生物量保持在中等水平；而重牧、过牧、极牧下草地生物量迅速减少。通过将每年收割的生物量进行累加，可以发现轻牧卞收获的生物量总量是最大的，随着放牧强度的增加，收获的生物量迅速减少，如果同时考虑到适口性的问题，则可以发现轻牧下可以收获最多的生物量，而过牧和极牧下只能收获极少的适口性非常差的碱蓬。 模拟结果表朋，过牧是导致松嫩草地次生盐碱化最重要的．原因，它不仅造成草地土壤的退化，而且加速了草地群落的次生演替。适宜的放牧强度对于保护草地免受退化，保持较高的草地生产力水平至关重要。而过牧不仅降低了草地的生产力，而且严重破坏了草地环境，引起草地的迅速退化。更多还原

【Abstract】 The vast alkalinized-salinized grasslands in the Songnen Plain, Northeastern China, are suffering from degradation resulting from soil alkalization and salinization. The topographical features and climatic conditions of the area result in a very slow primary soil alkalization and salinization process. Human抯 over-utilization of the grasslands, e.g. overgrazing and mowing, results in a secondary soil alkalization and salinization process, which is much faster than the primary one. It is a process of serious degradation of the grassland, and leads quick regressive successions of the meadow steppe ecosystem. A general regressive succession process under overgrazing can be separated into some phases in terms of their dominant species, 1) Aneurolepidium chinense, 2) Aneurolepidium chinense and Chioris 憊irgata, 3) Chloris virgata, and 4) Suaeda glauca. In this paper, we attempted to build a process-based model, to describe the ecological processes in the grassland ecosystems, and to estimate the potential impacts of different grazing intensity on the grassland. This model was constituted with five submodels, which described the 1) climatic valuables for grassland ecosystems, 2) the hydrological pro~esses in the soil, 3) the alkalizationlde- alkalization and salinizationlde-salinization processes in the soil, 4) the growth processes of the herbaceous communities and 5) the potential impacts of different grazing intensities on the grasslands. Some important climatic variables for grassland ecosystems were described in the submodel of climatic valuables, including temperature, precipitation, radiation, relative humidity, sunshine fraction and wind velocity. Analytical equations were used to calculate the radiation at any topographical situation, which includes the possible iii - lv - duration of sunshine, exoatmospheric solar radiation, and total solar radiation. Amended Penman抯 equation was used to evaluate the potential evapotranspiration of China. The simulation results were verified to be effective with the observed pan evaporation data from 900 meteorological observation stations. After combining a numerical integration model and a water balance model, a physically-based modelling of hydrological processes in soil was built with the Object-oriented design. This model is run at daily-time step, and it can be used for different soil texture classes. It was used for simulating dynamics of soil water with great vertical spatial heterogeneous. The hydrological processes of four different soils in Songnen grasslands were simulated and the results and the results were verified with the experimental data from four dots in Songnen Plain in 1997. A dynamical model was built on the basis of salt and water balanced modelling and mechanism modelling. This model is a daily-time step, and suit for the simulation the movements of salts in heterogeneous soil. As a case study of the model, the dynamics of salt concentration, exchangeable sodium percentage (ESP) and pH were simulated on two plots in 1997, with A. chinense and S. corniculata growing on it respectively. Comparing with the experimental data, the simulation results can express the dynamics of saline and alkaline in different seasons. Climatic valuables, soil moisture, salt concentration, ESP and pH were regarded as the most importan更多还原