内蒙古羊草草原17年刈割演替过程中功能群组成动态及其对群落净初级生产力稳定性的影响(英文)

基于17 yr的野外实验数据,研究了内蒙古羊草草原群落刈割演替过程中的功能群组成动态,探索了功能群组成变化与群落净初级生产力(ANPP)之间的关系,分析了结构参数怎样影响功能参数。结果显示:在17 yr的割草演替过程中,群落的结构与功能均发生了变化。随着羊草群落刈割演替的进行,群落的功能群组成发生了显著变化,根茎禾草在群落中的优势地位相继被一、二年生植物、高丛生禾草和矮丛生禾草所取代。到17 yr末,群落变成根茎禾草、矮丛生禾草、高丛生禾草共同建群的群落。在对照群落中ANPP与年降水量显著相关,但在刈割群落中二者则不相关。年降水量解释对照群落ANPP变异的62％,而连年的刈割干扰则是刈割群落中ANPP动态的主要驱动因子。群落净初级生产则显出对刈割干扰的抵抗能力,在刈割干扰的前几年,依靠群落内功能群组成的不断调节,保持相对稳定的水平,当刈割进行5 yr之后,群落结构的变化积累到一定程度,净初级生产迅速下降到一个较低的水平,此后依靠群落结构的不断调节来维持这一功能水平。因此,群落结构是以渐变的方式改变的,而群落功能的下降则是以跃变的形式完成的。群落依赖于结构的不断调整来保持功能的相对稳定,但结构变化到一定程度也会导致功能的衰退。

Compositional Dynamics of Plant Functional Groups and Their Effects on Stability of Community ANPP During 17 yr of Mowing Succession on Leymus chinensis Steppe of Inner Mongolia, China

Using field experimental data of 17 yr of mowing succession of Leymus chinensis (Trin.) Tzvel. steppe of Inner Mongolia (Nei Mongol), we analyzed the dynamics of community composition based on plant functional groups (PFGs), explored the relationship between changes of the PFGs proportion in community and the community annual net primary production (ANPP), and examined the influences of structural parameters on functional parameters. Our results showed that during 17 yr of mowing succession, changes in both community structure and function took place. The roles of different PFGs varied appar-ently with mowing succession: the dominance of rhizome grasses was replaced successively by annuals and biennials, tall bunch grasses, and short bunch grasses. Following 17 yr of mowing, the community became codominated by rhizome grasses, tall bunch grass, and short bunch grass. ANPP correlated significantly with annual precipitation in control plot, but not in successive mowing plot. Annual precipita-tion explained more than 62% of the annual variability in ANPP of control plot, whereas annual variation of ANPP in mowing plot was mainly driven by successive mowing disturbance. The community ANPP showed resilience to mowing disturbance and kept relatively stable initially through internal regulation of PFGs, and declined to a lower level with structural changes of the community after about 5 yr, and then again maintained at a stable level through structural regulation. Therefore, in mowing succession the commu-nity structurere presented by PFGs changed gradually while the community function represented by ANPP declined abruptly. The community relied on constantly regulating the structure to maintain the function stability. The community function would degrade after its structure changed to certain degree.