草 食 家 畜

【目的】浑善达克沙地广泛存在的不合理放牧是当前榆树疏林生态系统退化、榆树种群繁衍受阻的主要原因。针对沙地特殊的基质和植被特征，探讨适合其特质的放牧管理形式，为榆树疏林生态系统的恢复和可持续利用提供科学依据。【方法】选择4块对比样地，通过采集树芯，建立胸径-树龄模型，结合50×50 m²样方每株调查，获取榆树年龄结构分布。通过牧户调查，获取每块样地的放牧管理方式，探讨放牧季节和家畜种类对榆树种群繁衍更新的影响。【结果】冬季放牧的样地，榆树种群密度适宜(104株/50×50 m²)，年龄分布均衡，种群繁衍更新状态良好；夏季放牧的样地，榆树密度较小(97株/50×50 m²)，其中幼苗缺失，种群更新受阻；轻度牧牛的样地，新生出密集的榆树种群(750株/50×50 m²)，以幼树、幼苗为主，种群处于显著恢复阶段；长期牧羊的样地，榆树密度低(31株/50×50 m²)，幼苗和成年榆树缺失，种群更新不良。【结论】因沙地松软不耐踩踏的特性，沙地适合在冬季冰冻硬化后放牧，应避免在其它季节放牧。因家畜对植物的选择性采食，轻度牧牛有利于榆树种群的恢复，牧羊对榆树种群恢复不利。

【Objective】The widespread irrational grazing in the Hunshandak sandy land is the main reason for the degradation of the Ulmus pumila woodland ecosystem and the obstruction of Ulmus pumila population reproduction and renewal. In order to explore suitable grazing forms that fit the special substrate and vegetation characteristics of sandy land, so as to provide scientific basis for the restoration and sustainable utilization of the Ulmus pumila woodland ecosystem.【Methods】Four adjacent comparison plots were selected in the Hunshandak sandy land, and a DBH-age model of Ulmus pumila was established by collecting tree cores.Combined with a measurement of each tree in a 50 m×50 m plot, the age distribution of Ulmus pumila in the four plots was analyzed. Through a survey of ranchers, the grazing utilization forms of each plot were obtained to explore the effects of grazing season and livestock species on the reproduction and regeneration of Ulmus pumila populations.【Results】In the winter grazing plot,the population density of Ulmus pumila was suitable(104 plants/50 m×50 m), with a balanced age distribution and good regeneration status, while in the summer grazing plot, the density was relatively small(97 plants/50 m×50 m), with missing seedlings and hindered population renewal; In the plot for mild cattle grazing, a dense population of Ulmus pumila(750 plants/50m×50 m) had emerged, mainly consisting of young trees and seedlings, indicating that the population was in a significant recovery stage, while in the plot for long-term sheep grazing, the density was low(31 plants/50 m×50 m), and seedlings and adult trees were missing, indicating poor population renewal.【Conclusion】Due to the soft and easily trampled nature of the sandy land, grazing should be avoided in other seasons and only be conducted in winter after the ground had been frozen. Besides, in consideration of the food selectivity of livestock, mild cattle grazing was more beneficial to the recovery of the Ulmus pumila population than sheep grazing in a long term.