Abstract: In order to study the influences of uncultivation duration and slope aspect on the aboveground biomass of shrub and subshrub life-form and species richness on uncultivated arable lands in Loess Hilly Region,the four uncultivated arable lands with different uncultivation durations (12 a,20 a,30 a and 42 a) which located on the shady and sunny slopes respectively in the loess hilly region were used as objects in this study. The changes in the biomass and species richness of the shrub communities on these uncultivated lands were analyzed. The results showed that the species richness,aboveground biomass of the plant communities,aboveground biomass of shrub and subshrub life-form and its percentage increased along with the chronosequence after uncultivation. The peak values occurred in the 30 years after uncultivation in sunny slope with 10.5 species·m^-2,133.20 g·m^-2,50.15 g·m^-2,respectively;and the highest percentage of aboveground biomass of shrub and subshrub life-form in shady slope reached in the 42 years after uncultivation,with a value of 51.68%. The aboveground biomass of plant community and species richness in the sunny slope were higher than those in the shady slope,correspondingly;while the aboveground biomass of shrub and subshrub life-form in the sunny slope was less than that in the shady slope. Furthermore,the proportion of the number of species in the shrub and subshrub life-form decreased along with the chronosequence after uncultivation,and the proportion reached 28.57% in the 12 years after uncultivation. There were significant positive correlations of the aboveground biomass of plant communities,shrub and subshrub life-form and species richness of the communities with the uncultivation duration. The species number and aboveground biomass of shrub and subshrub life-form changed with different slope aspect.

Key words: Uncultivated lands, Aboveground biomass, Shrubs and subshrubs, Species richness, Slope aspect

摘要： 为研究撂荒年限和坡向对草地植物灌丛地上生物量及丰富度的影响,本研究以黄土丘陵区不同坡向4个主要撂荒年限(12 a,20 a,30 a和42 a)草地作为研究对象,分析其草地灌丛地上生物量及丰富度的变化。结果表明,撂荒草地物种丰富度、植物群落地上生物量、灌丛地上生物量及其百分比随撂荒年限的增加而增加,峰值多集中出现在30 a阳坡草地,分别达到:10.5种·m^-2,133.20 g·m^-2和50.15 g·m^-2,阴坡草地灌丛地上生物量百分比在42 a占比最高,达到51.68%;阳坡草地群落地上生物量及物种丰富度高于阴坡草地;但阳坡草地灌木和半灌木地上生物量低于阴坡草地,且阳坡撂荒草地群落灌木和半灌木物种数目百分比随撂荒年限的增加而降低,12 a占比最高达28.57%。撂荒年限与群落地上生物量、灌木和半灌木地上生物量、物种丰富度之间均存在正相关关系,坡向不同引起植物群落灌丛数量和生物量的变化。

关键词: 撂荒草地, 地上生物量, 灌木和半灌木, 物种丰富度, 坡向