Abstract:

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 co-dominated 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 structure represented 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.

Key words: Leymus chinensis steppe, mowing succession, functional groups dynamics, annual net primary production (ANPP), community, stability