封育和放牧对黄土高原典型草原芽库的影响

Effects of fencing and grazing management on bud bank in a semiarid steppe on the Loess Plateau

在多年生草地生态系统中,芽库在干扰后的种群补充和更新中占据着重要地位。本研究采用单位面积挖掘取样法,比较分析了封育和放牧对黄土高原典型草原地上植被特征和芽库密度的影响。结果表明,黄土高原典型草原芽库以分蘖芽为主,密度为832~6 848芽·m^(-2)。与放牧相比,短期封育显著提高了芽库总密度和禾草芽库密度,但显著降低了非禾草芽库密度(P<0.05)。封育和放牧对典型草原芽库密度的显著影响,主要来自根茎型、分蘖型和根蘖型牧草芽库的贡献。短期封育显著提高根茎型和分蘖型牧草的芽库密度,而显著降低根蘖型牧草的芽库密度(P<0.05)。禾草芽密度与地上生物量呈显著正相关,与地上茎分枝数呈显著负相关(P<0.05)。封育和放牧对黄土高原典型草原地上植被特征的影响可能是通过调控禾草芽库密度来实现的。在草地管理中,芽库对地上植被的发展有一定的指示作用,可以依靠芽库的测定来预测未来植被的产量、演替趋势和发展方向。

In perennial grassland ecosystems, the bud bank plays an important role in vegetation maintenance and recruitment. In this study, we used field root-digging to examine the bud bank, analyze above-ground vegetation characteristics, and below-ground bud bank density, under fencing and grazing management measures. Results showed that the bud bank in a semiarid perennial steppe on the Loess Plateau was dominated by tiller buds, and bud bank density ranged from 832 to 6 848 bud - m-2. Short-term fencing significantly increased the bud bank density and the density of grass bud banks, and decreased the density of forb bud banks in relation to grazed grasslands （P〈0.05）. The change of tiller buds, rhizomatous buds and root sucker buds caused a change in total bud bank density under two management types. The density of tiller buds and rhizomatous buds was significantly higher and the density of root sucker buds was significantly lower in grasslands fenced for five years than in grazed grasslands （P〈0.05）. Grass bud bank density was significantly and positively correlated with above-ground biomass, but negatively correlated with above-ground shoot numbers （P〈0.05）. To a certain extent, the effects of grazing and fencing on aboveground vegetation in a semiarid steppe on the Loess Plat-eau are mediated through grass bud bank demography. The bud bank is an excellent predictor of the aboveground vegetation. We can predict grassland productivity and succession direction using bud bank determination.