To provide a theoretical basis for vegetation restoration and the maintenance of biodiversity,we studied the effects of the duration of enclosure on plant propagation and vegetation regeneration in the semiarid perennial steppe of Yunwu Mountain.We compared non-enclosed (grazed) grasslands and grasslands enclosed for 5,15,23,32 years using the field root-digging method to investigate plant reproductive strategies.The results showed that the duration of enclosure significantly affected species richness (P＜0.05).Species richness was significantly higher in grazed sites than in grasslands with 23 and 32 years of grazing exclusion.However,there was no significant difference in species richness among grazed grassland,grassland with 5 years grazing exclusion,and grassland with 15 years grazing exclusion (P＞0.05).The duration of enclosure significantly affected the densities of total offspring,asexual offspring,rhizomes,tillers,stolons,and branches (P＜0.05),however,the densities of sexual offspring and root suckers did not differ significantly among the treatments (P＞ 0.05).With prolonged duration of enclosure,the total density and asexual reproduction density decreased;the offspring density from rhizomes and tillers first increased and then decreased;the offspring density from root suckers and branches first decreased and then increased;the offspring density from stolons increased gradually;and the ratio of asexual and sexual reproduction densities first increased and then decreased.There were significant positive correlations between vegetation density and asexual offspring density,and between vegetation density and total offspring density.Our results indicate that short-term enclosure was conducive to offspring recruitment,and long-term enclosure was disadvantageous for grassland regeneration.Fencing for 5 years was the most conducive to offspring recruitment and grassland regeneration in the semiarid steppe of Yunwu Mountain.Compared with sexual offspring,asexual offspring contributed more to total offspring density,which directly affects the density of the plant community.The trends in the change in density in the plant community could be predicted from offspring density during the succession process.%研究封育年限对黄土高原典型草原繁殖更新的影响,为退化黄土高原植被恢复和生物多样性维持提供一定的理论依据.在云雾山自然保护区的实验区选取不同封育年限区(5,15,23,32年)和放牧地(对照)草地作为试验样地,采用挖掘取样法进行草地繁殖更新的研究.结果表明:封育年限对后代繁殖更新苗的物种丰富度影响显著(P＜0.05).封育5年草地和封育15年草地的后代更新苗的物种丰富度与放牧地差异不明显(P＞0.05),而封育23年草地和封育32年草地的后代更新苗的物种丰富度显著小于放牧地.封育年限对草地后代繁殖更新总密度、无性繁殖密度、根茎型、分蘖型、匍匐型和分枝型的繁殖密度均影响显著(P＜0.05).随着封育年限的增加,繁殖更新总密度和无性繁殖密度均呈递减趋势,根茎型和分蘖型密度均呈先升高后降低趋势,根蘖型和分枝型密度呈先降低后升高趋势,匍匐型的密度呈逐渐增加趋势,无性繁殖密度与有性繁殖密度之比呈先增加后降低趋势.植物群落密度与无性繁殖密度、繁殖更新总密度之间均呈正显著相关.在云雾山典型草原,短期封育有利于植物后代繁殖更新,长期封育反而不利于草地的繁殖更新,对退化草地封育5年最有利于植物的繁殖更新.植物无性繁殖密度的变化直接影响着繁殖总密度的变化,从而影响了植物群落的密度变化.
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