青藏高原高寒草地退化与人工恢复过程中植物群落的繁殖适应对策

以三江源区不同退化程度高寒草甸和不同恢复年限人工草地作为研究对象,通过野外调查与采样、实验室分析,探究了高寒地区退化天然草地与人工恢复草地的植被群落繁殖构件数量变化.结果表明:在群落水平上,天然草地退化和人工草地建植会对植物繁殖构件的数量和生物量产生影响.随着天然草地退化程度的增加,营养枝数量和生物量则明显下降,而繁殖枝的数量和生物量明显升高(P＜0.05);随着人工草地恢复年限的增加,营养枝的数量和生物量逐渐增加,而繁殖枝的数量和生物量则逐渐降低(P＜0.05);随着恢复年限的增加,人工草地繁殖构件的变化逐渐接近未退化天然草地.在功能群水平上,植物繁殖构件数量亦随草地退化程度和人工恢复年限而变化.随着恢复年限的增加,禾本科、莎草科、杂类草的营养枝数量和生物量均呈现显著增加(P＜0.05),而繁殖枝数量和生物量则显著下降,禾本科的繁殖构件数量远远大于莎草科和杂类草;随着退化程度的增加,三大功能群的营养枝枝数和生物量显著增加(P＜0.05),而繁殖枝则呈现相反的趋势.实证了草地退化和人工恢复改变植物群落繁殖分配对策的科学假设,为高寒草地植被恢复重建技术的发展和更新提供理论支撑.

Adaptation strategies of reproduction of plant community in response to grassland degradation and artificial restoration

In this study, we selected the artificial grasslands with different restoration years and natural grasslands with different degradation levels to explore the changes of vegetation reproduction mode, aiming to find the feasible restoration approaches derived from the theoretical study. We found that grassland degradation and establishing artificial grassland had significant effect on the number and biomass of asexual and sexual shoots. The main conclusions are as follows: asexual reproduction dominated in the native alpine grassland. The number and biomass of asexual shoots of natural grasslands were basically lower than those of cultivated grasslands. The number of asexual shoots increased with the cultivation ages (P<0.05), and decreased with the degradation degree (P<0.05). On the contrary, the number and biomass of the sexual shoots presented opposite trend with those of the asexual shoots. With the increase of restoration years, the components of asexual and sexual shoots were close to non-degraded grassland. At the functional groups level, the number and biomass of asexual shoots were decreased with the restoration years (P<0.05), while those of sexual shoots were presented on the opposite trend; moreover, the components of grasses were significantly higher than other two groups (P<0.05). At the same time, we found that forbs accounted for absolute advantage, the similar change can be seen about degraded grassland as compared with artificial grasslands along the degradation levels. The above conclusions indicated that grassland degradation had altered the reproductive allocation and strategies about plant community, and establishing artificial grasslands is an efficient method to restore degraded alpine grasslands.