怀来盆地丘陵区弃耕地自然恢复过程中植物群落地下生物量动态

Dynamics of underground biomass during natural restoration process of abandoned farmland in Huailai Basin,Hebei Province

采用空间替代时间方法，确定怀来盆地丘陵区弃耕地自然恢复过程中的3个阶段：弃耕地阶段、草本群落阶段和灌丛群落阶段。基于此，研究弃耕地自然恢复过程中植物群落地下生物量动态。结果表明：随着弃耕地的恢复，植物群落活根、死根和地下生物量都显著增加，各恢复阶段之间的差异，重点在0—20cm范围内，各群落深层次根系以活根为主；多年生植物，尤其是灌木的入侵，使植物群落根系总体上明显向纵深方向发展；不同恢复阶段地下生物量的季节累积规律也不同，经过一个生长季，弃耕地和草本群落的地下生物量均有显著增加，而灌丛群落的变化不显著；弃耕地地下生物量特征主要由浅根系的猪毛菜（Salsola collina）决定，甘草（Glycyrrhiza uralensis）的贡献也不容忽略，草本群落地下生物量则转变为以多年生的禾草和杂类草根系为主，灌丛群落地下生物量分布特征与累积规律反映了其优势灌木种河蒴荛花（Wikstroemia chamaedaphre）的根系特征；除了弃耕地活根外，各群落活根、死根和地下生物量在土壤中的垂直分布呈T字型，递减规律可用指数或幂函数表示，根系聚集在土壤表层，容易造成植物对水分和养分的竞争。

Three types of sites were selected to represent three phases of the restoration process with the method of substituting time with space in Huailai Basin, Hebei Province. They were recently abandoned farmland, abandoned farmland colonized by grasses, and abandoned farmland colonized by shrubs. Dynamics of underground biomass during the natural recovery process of abandoned farmland were studied. Results showed that the living roots, dead roots and total roots increased with the recovery process. The roots in the deep layers were most living. The differences among the three communities of the underground biomass were significant in the 0 - 20 cm soil layer. Perennial species, especially the shrubs had deeper root distribution. Seasonal accumulation of the underground biomass was different among the three communities. After a growth season, the roots were increased on the recently abandoned farmland and the grass colonized farmland, butslightly decreased on the shrub colonized farmland. The characteristics of the underground biomass of the recently abandoned farmland were mainly influenced by Salsola collina Pall., a shallow rooted species, with noticeable contribution of Glycyrrhiza uralensis. The underground biomass on the grass colonized farmland was mainly composed of perennial grass and forbs. Distribution and accumulation of the shrub community roots were consistent with the shrub species, Wikstroemia chamaedaphre. With exception of the living root on the recently abandoned farmland, distributions of the living roots, dead roots and total roots of the three communities followed the T shape. The pattern of decreasing roots with depth could be expressed by exponent or power functions. The accumulation of roots in the surface soil layers could easily induced competition for nutrients and water.