干旱半干旱地区围栏封育对甘草群落特征及其分布格局的影响

长期的封育禁牧引起甘草种群退化已受到越来越多的学术关注。选取采挖后不同封育年限的甘草群落为研究对象,以样地调查数据为基础,应用方差均值比率和聚集强度指数的测定方法进行围栏封育对甘草群落征及其分布格局的影响进行分析,结果表明:(1)随着围栏封育年限的增加,甘草群落物种丰富度指数、多样性指数均呈增加的趋势,均匀度指数则呈先增加后降低的趋势;(2)随着围栏封育年限的增加,甘草群落内甘草、冰草、黄蒿和猪毛蒿4种主要种群空间格局均发生了变化。甘草和冰草种群由随机分布变为聚集分布,但种间竞争却呈相反的变化趋势;黄蒿和猪毛蒿种群则由聚集分布变为随机分布;(3)干旱、半干旱地区野生甘草种群的恢复期为5a左右,其鲜草产量及地上生物学指标均为最佳,截时应进行合理的采挖与利用,以促进其种群的发展与生产力的提升。

Influence of enclosure on Glyeyrrhiza uralensis community and distribution pattern in arid and semi-arid areas

With the policies of conversion of cropland to forest and grassland and exclosure under no grazing carried on, the desert stppe ecosystems is under restoration and regeneration to some extent. However, long-term exclosure did not assure the restoration of plant communities in desert steppe. As was concerned, Glyeyrrhiza uralensis community tended to degrade. Taking the Glyeyrrhiza uralensis community under exclosrue of different ages after excavation as a subject, the influence of enclosure on Glyeyrrhiza uralensis population community and distribution pattern was discussed, by the method of the mean variance ratio and indices of aggregation intensity. The result showed:1) Under enclosure along with the increasing ages, species richness index and diversity index of Glyeyrrhiza uralensis community tended to increase. Evenness index firstly increased and then decreased. 2) The spatial pattern of Glyeyrrhiza uralensis, Agropyron cristatum, Artemisia sieversiana and Artemisia scoparia population were all changed. That of Glyeyrrhiza uralensis population and Agropyron cristatum population changed from random into aggregation,but the intercompetition was opposite. That of Artemisia sieversiana and Artemisia scoparia population changed from aggregation into random. 3) In arid and semi-arid region, the recovery of Glyeyrrhiza uralensis species needed 5 years, and the grass yield and the ground biological indexes are better. At that time, Glyeyrrhiza uralensis should be reasonably excavated, thus beneficial for the improvement of population development and related productivity.