自然与人为干扰胁迫下喀斯特峰丛洼地植物根系的适应策略

It is crucial to the vegetation restoration and rocky desertification control that response of plant roots to intensive human disturbance and natural stress, such as high ratio of naked rock, high content of calsium (Ca) and magnesium (Mg), barren soil, severe seasonal karst drought, etc, in depression between karst hills. However, it has been neglected in the previous researches. Four successional stages (i.e., herbaceous stage, shrub stage, shrub-tree stage, and climax primary forest) reflecting different human disturbance intensities and three slope position (i.e., lower slope, middle slope, and upper slope) on behalf of natural stress environment will be chosen to build three community quadrats (20m×20m), respectively. Based on the field investigation and experimental analysis, the research will intend to reveal the differences of root system distribution, root architecture, and configuration, ecological, and physiological function of fine root among plants under different hunman disturbance and natural stresses in depression between karst hills. Principal component analysis (PCA) and canonical corresponding analysis (CCA) will be applied to find out the major factors of influencing on plant root growth and distributon, and to show interaction relationships between groups of plant root, aboveground vegetation, soil physical and chemical properties, soil microbe, topography, and human activities. Detrended canonical correspondence analysis (DCCA) also will be used to demonstrate plant root distribution along human disturbance or natural stress environmental gradients. The aim of this study is to reveal the adaptive strategies of plant roots under natural stress or human disturbance in depression between karst hills, which could provide a scientific basis for quick recovery of vegetation and ecological restruction in karst areas...

植物根系对喀斯特峰丛洼地岩石裸露率和钙镁含量高、土壤瘠薄、季节性岩溶干旱严重等自然和人为干扰强烈双重胁迫环境的适应是植被恢复与石漠化治理的关键，但这却被以往研究所忽视。本项目在不同人为干扰强度下形成的草本、灌木、灌乔过渡、顶极原生林4个植被演替阶段和能综合反映自然胁迫环境的下、中、上3个坡位分别选择3种代表性群落，各建立3个样方（20m×20m）。基于全面系统调查，分析不同人为和自然胁迫环境下喀斯特峰丛洼地植物根群分布、根系构型和细根结构、生态、生理等功能特征的差异，用PCA、CCA等方法找出影响植物根系生长发育和分布的主要因子，阐明植物根系与地上植被、土壤理化性状、土壤微生物性状、地形、人为干扰等集团因子之间的关系，用DCCA表征植物根系沿人为干扰或自然胁迫环境梯度的分布，揭示植物根系在喀斯特峰丛洼地人为干扰与自然胁迫下的适应策略，为喀斯特峰丛洼地植被迅速恢复和生态重建提供理论依据。

喀斯特峰丛洼地植物根系对自然和人为干扰环境的适应是植被恢复与石漠化治理的关键。本项目通过开展喀斯特峰丛洼地植被恢复过程中优势种根系构型特征、植被恢复过程细根生物量和功能特征时空变化、喀斯特峰丛洼地植被群落特征及与土壤性状的耦合关系、森林生态系统根系生物量及碳储量估算等相关问题的研究。获得结论如下：.（1）喀斯特常绿落叶阔叶混交林种群分布受物种属性和生境异质性共同塑造，具有明显的垂直分布格局，丰富度和Shannon-Wiener指数随海拔升高呈单峰变化。.（2）喀斯特峰丛洼地不同恢复阶段优势种根系呈叉状分支结构，具有较长的根系连接长度和较低分支率，体现了喀斯特物种对生境的适应对策。.（3）喀斯特灌丛细根生物量显著高于草丛、次生林和原生林，集中分布在0~10 cm表层土壤中，从春季至冬季活细根生物量呈单峰变化的趋势，均以秋季生物量最高，细根生产量呈现次生林>原生林>灌丛>草丛的趋势；细根比根长和比表面积随着植被由草丛向原生林正向恢复而逐渐降低，多数细根根长和根面积为0~0.5 mm和0.5~1 mm两级根，且土壤有机碳、速效钾和全氮对细根特征影响较大。.（4）不同恢复阶段根际与非根际土壤养分均呈现显著差异，大多数养分表现出明显富集效应，且土壤有效态养分较全量养分对植物根际微小的变化响应更为灵敏，根际土壤细菌与真菌Shannon-wiener指数、丰富度指数与Pielou均匀度都高于非根际土壤。.（5）沿群落正向演替发展，群落科、属、种及物种多样性的最大值出现在次生林阶段，原生林具有最佳的群落结构；典型植被类型土壤中的优势固氮微生物为慢生根瘤菌，植物群落与固氮微生物群落显著相关，土壤总氮、有效态钾、有效态钙对固氮微生物群落的影响显著..（6）建立的广西主要树种（组）生物量回归方程能很好的估算林分生物量，区域尺度明确了森林生物量分配格局具有明显的地理分布格局，无论是否消除植物个体大小的影响，其生物量分配格局均受环境因子的制约。