【作者】 刘志民；

【导师】 刘新民；

【作者基本信息】 中国科学院研究生院（寒区旱区环境与工程研究所） ， 自然地理， 2001， 博士

【摘要】 干扰对植被的作用可概括为两个方面:植物种或植被对干扰的适应和干扰对植被的作用。植物在物种水平适应干扰时表现的可塑性反应、在种群水平适应干扰时表现的均衡反应、在群落或植被水平适应干扰时表现的功能类型的分异以及干扰在植被过程中对植物繁殖体扩散的作用、对种子库组成的作用、对植物种组成和生物量的作用已成为研究的焦点,并且正被深入地研究。基于对干扰研究趋势的了解,本论文选择如下6个方面进行了例证研究,其中前3个方面论述的是植物在3个水平(包括物种、种群、群落或植被)对干扰的适应,后3个方面论述的是干扰对植被过程(包括种子传播、种子库组成、植物种组成、地上生物量)的作用。 ● 植物在物种水平对干扰的可塑性适应。比较了来自三个国家、具有从很干旱到很湿润范围的原始生境背景的20个植物种的幼苗根系对旱化土壤的反应。 ● 植物在种群水平对干扰的均衡适应。研究了海拔梯度、沙埋和砍伐等干扰方式对砂生槐种群的作用。 ● 植物在群落水平对干扰的功能类型适应。根据已有文献,对沙坡头流沙逆转、生境旱化过程中的植被动态进行了植物功能类型的解释。 ● 干扰在植被过程中对繁殖体扩散的作用。以对砂生槐种群种子库格局和种子传播方式的调查为基础,阐述了风、水、动物、重力等引发的干扰对砂生槐种子传播的作用。 ● 干扰在植被过程中对种子库组成的作用。以科尔沁沙地为例,对不同放牧强度下沙质草地种子库特征进行了研究。 ● 干扰在植被过程中对植物种和生物量的作用。通过对河北坝上草地沙漠化过程中的植物种丰富度和生物量以及褐沙蒿、冷蒿在群落中重要值变化的研究,对沙漠化过程中的植被过程特别是两种蒿属植物对植被退化和沙漠化阶段的指示意义进行了探讨。 通过这些例证研究,得出了一些植物适应干扰和干扰对植被作用的结论。 (1)对于植物幼苗根系对旱化土壤的形态反应的比较研究表明:幼苗形态可塑性是植物适应旱化土壤的机制之一;来自干旱生境的植物种的幼苗比来自湿润生境的植物种的幼苗具更明显的形态反应。 (2)对于砂生槐适应干扰的研究表明,快速生长与慢速生长、有性繁殖与无性繁殖间的均衡是重要的植物适应干扰机制。更多还原

【Abstract】 Effects of disturbance on vegetation can be summarized in two categories: 1) adaptations of species or vegetation to disturbance; and 2) roles of disturbance in determining vegetation processes. Plastic responses of plant species to disturbance, tradeoffs between variables within populations in response to disturbance, differentiation of plant functional types in plant communities (or vegetation) in relation to disturbance, and roles of disturbance in dispersing diaspores, determining seed composition, species composition and above-ground biomass have attracted extensive attentions of ecologists in recent years. To determine the trait variations associated with disturbance history and current disturbance regime as well as the interactions between these factors, global-scale comparisons of numerous individual studies are required. Therefore, several case studies concerning 6 aspects are presented in this thesis.Plastic responses of plant species to disturbance. 20 species from habitats of widely varying moisture status, ranging from marsh to desert in three countries, were selected to compare the morphological responses of their seedlings’ roots to drying soil.Trade-offs between variables in populations in response to disturbance. A study on the roles of an altitudinal gradient, sand burial and cutting in Sophora moorcroftiana population characteristics was conducted.Differentiation of plant functional types in plant communities in relation to disturbance. According to existed literature, an analysis on vegetation dynamics concerning shifting sand reversion and habitat drying at Shapotou was carried out with reference to plant functional types.Role of disturbance in dispersing diaspores. Based on the surveys of seed bank patterns and seed dispersal ways of Sophora moorcroftiana, the roles of dispersal agents such as wind force, flowing water, animals and gravity, which are sources of disturbance in dispersing seeds of S. moorcroftiana, were discussed.Role of disturbance in determining seed composition. In the Horqin Sandy Land, soil seed bank characteristics of sandy steppe under different grazing regimes were explored.Roles of disturbance in determining species composition and above-ground biomass.Based on the investigation of shifts of species richness, above-ground biomass and importance value shift of Artemisia intramongolica and A. frigida at Bashang in Hebei Province, the vegetation process, and especially, the indicating roles of the two Artemisia species in the desertification process were discussed. The conclusions in specific adaptations to disturbance and roles of disturbance on vegetation processes derived from these case studies are listed here.(1) The comparison of the morphological responses in seedlings’ roots to drying soil showed that 1) morphological plasticity in seedlings’ roots is one of the adaptive mechanisms of plants to drying soil; and 2) seedlings of species from dry habitats make more appropriate morphological responses to the onset of drought than do seedlings of species from wet habitats.(2) The study on performances of Sophora moorcroftiana showed that trade-offs between rapid and slow growth, sexual and vegetative reproduction in populations are important adaptations of plants to disturbances.(3) The study on vegetation dynamics at Shapotou showed that 1) with the changes of disturbance types, vegetation processes are characterized as the shift of primary plant functional types; and 2) compared with species composition and lifeforms, plant functional types have more universal significance in describing vegetation dynamics.(4) The study on seed dispersal of Sophora moorcroftiana showed that 1) wind force, flowing water, animals and gravity all contributed to the diaspore dispersal and the formation of population patterns although their effects on seed distribution were different; 2) disturbance has positive effects on vegetation.(5) In the Horqin Sandy Land, with the increase of grazing intensity, seed composition and seed number in the soil seed bank changed in four aspects: 1) seed bank density declined; 2) seed composition proportion of annuals increased; 3) seed number proportion of annuals decreased, but that of leguminous species increased; 4) the correlation between seed number in the seed bank and species frequency in the vegetation became poorer. The influence degree of grazing on soil seed bank is one of indexes in determining grazing intensity.(6) At Bashang, with desertification occurring, the vegetation structure was modified in two aspects: 1) invasion of shrubs; 2) the increase in the proportion of annuals. However, the above-ground biomass did not change linearly. A conclusion is that degree of species dominance is more sensitive to desertification than above-ground biomass, and that speciescomposition and indicating species, rather than biomass, seem to be the more important factor in determining desertification intensities.These case studies are significant in ecological restoration and vegetation management.(1) To successfully establish artificial vegetation on sand dunes in arid area through seeding is greatly relies on the emergence and survival of seedlings. It might be helpful to select species, which can adjust their root morphologies and exploit deeply buried water resources in the seedling phase in drying soil, as sand binders.(2) The characteristics of Sophora moorcroftiana (such as trade-offs in growth and reproduction, morphological characteristics which may have drought-resistant significance, long life span and slow growth) in response to disturbance mean that it can be selected as a sand binder in its distributed area.(3) In sand-fixing practice, psammophytes, ruderals and drought tolerators have different functions. An expected result can be realized if vegetation management protocol is established based on the analysis of roles of different plant functional types in vegetation process.(4) In the Horqin Sandy Land, because the treatment of 6 sheep unit/ha had caused the evident decrease in seed density of soil seed bank and strikingly poor relativity between seed number in the seed bank and species frequency in the vegetation, it should be taken as intense grazing regime.(5) At Bashang, Artemisia intramongolica is an indicator of serious desertification. A. frigida is an indicator of grassland degradation due to over-grazing, or of vegetation restoration after serious desertification. Therefore, when carrying out restoration projects of desertified land at locations like Bashang, Artemisia frigida could be introduced to prevent desertified lands from further deterioration, Artemisia intramongolica could be introduced to rapidly restore the desertified land.更多还原