我国北方半干旱牧区天然打草场退化分级

摘要

Natural hay pastures in semi-arid pastoral areas produce the highest yields of hay in northern China.However,long-term continuous hay harvesting with no rest interval has resulted in severe degradation across widespread areas of these natural hay pastures.In addition,no clear data exist on the spatial distribution or degree of degradation occurring in natural hay pastures primarily because a nationally unified and normative evaluation standard is lacking.In view of the above problems,we employed an analytic hierarchy process to carry out screening and accuracy validation of evaluation indicators for natural hay pastures in north China grasslands (temperate meadow steppes,temperate steppes,mountain meadows,and lowland meadows).Our study identified seven easily measured indicators that reflect the state of natural hay pastures (average height,aboveground biomass,coverage,proportion of medium grasses,litter biomass,proportion of degradation-indicative plants,and proportion of bare spots and saline-alkali spots).A five-level scoring method was employed to delineate the threshold range for these indicators,The results of this study show that this method effectively solved the technical bottleneck for graded evaluation of degradation in natural hay pastures.This provides a theoretical basis for the scientific assessment of natural hay pasture degradation as well as important technical support for sustainable use of natural hay pastures and livestock production.%半干旱牧区天然打草场是北方牧区产量最高的草场,但由于长期连续打草,没有休闲机会,目前天然打草场普遍存在严重的退化,极大限制了天然打草场牧草的产量和质量,同时,我国天然打草场退化的空间分布及其退化程度的本底数据一直不清,主要原因之一与没有形成全国统一的、规范的评价标准有关.基于上述问题,本文采用层次分析法针对北方(温性草甸草原、温性草原、山地草甸、低地草甸为主)的草原区开展天然打草场退化评价指标的筛选与精度验证,研究明确了能够快速反映天然打草场退化的7项指标(平均高度、地上生物量、盖度、中型禾草比例、凋落物量、退化指示植物比例及裸斑、盐碱斑占地面比例),采用5级级差法划定了各项指标的阈值范围,即平均高度25-80 cm,地上生物量480-2500 kg ha-1,盖度26％-98％,中型禾草比例10％-50％,凋落物量100-400 kg ha-1,退化指示植物比例0-11％,裸斑、盐碱斑占地面比例0-14％.研究结果有效解决了天然打草场退化分级评价的技术瓶颈,为天然打草场退化的科学评价提供理论依据,也对天然打草场可持续利用及畜牧业生产提供了重要技术支撑.