大兴安岭林草交错带草地退化成因分析及其应对策略

Analysis of causes of forest-steppe ecotone degradation and countermeasures in the Greater Xing’an Range

近年来随着气候波动和人类农牧业对土地利用强度的增加,我国北方林草交错带面临严峻的草地退化问题.然而利用长期气候、放牧和开垦数据分析北方高纬度寒区林草交错带草地退化原因的研究还很薄弱.本研究利用63年长期数据,以大兴安岭林草交错带典型区域额尔古纳市和陈巴尔虎旗为研究对象,分析导致该区域草地退化的主导因素.结果表明,自1957年到2019年,两个地区的年均温都呈现极显著上升,平均升高2.9℃~3.1℃;降水量在150~550 mm呈剧烈式波动,但在2000年以后均呈下降趋势.不同经营主体的家畜放牧密度差异巨大,国有农场家畜密度由建厂初期不足每公顷1个羊单位上升到现在每公顷2~5个羊单位,而个人牧户的家畜密度从1980年每公顷0.5个羊单位增至2019年的每公顷7个羊单位,造成该区域严重的草畜失衡.随着土地利用政策变化,国营上库力农场和陶海牧场的播种面积先呈波动式上升,至2014年剧增至峰值37000和7000 hm^(2),以后由于退耕还林政策实施播种面积逐年下降.通过对气候、放牧和开垦数据的主成分分析表明,在区域气候逐渐变暖和干旱化的背景下,超载过牧是导致本区域草地退化的主导因素.因此,在本区域草地面临气候变化和土地退化的双重压力的背景下,建议加强对林草交错带土地利用方式的监察和管理,运用奖补手段,缓解开垦压力,降低放牧强度;强化科技创新,建立智慧牧场,利用人工种植优良牧草以及补播改良等科学技术手段,加大优质牧草生产,最终实现我国北方高纬度寒区林草交错带草地资源的可持续利用.

Due to climate fluctuations and increased land-use intensity owing to agriculture and animal grazing in recent years,the grasslands in the forest-steppe ecotone of northern China have dramatically degraded.The impacts of climate change and human activities on grassland degradation in the forest-steppe ecotone have not been adequately documented—especially using long-term data.In this paper,using 63-year long-term land-use change and meteorological data of Argun city and Chenbarhu Banner,we analyzed what factors have led to grassland degradation in the forest-steppe ecotone of the Greater Xing’an Range.Results showed that from 1957 to 2019,the mean annual temperature significantly increased from 2.9℃to 3.1℃in Argun city and Chenbarhu Banner.The mean annual precipitation fluctuated dramatically between 150 and 550 mm,with precipitation exhibiting an overall decreasing trend from 2000 to 2019.The livestock density increased greatly among different business entities.The average livestock density increased from less than 1 standard sheep unit/hm^(2) to 2–5 standard sheep unit/hm^(2) in the state-owned farms,while the average livestock density of individual herdsmen increased from 0.5 standard sheep unit/hm^(2) in 1980 to 7 standard sheep unit/hm^(2) in 2019,resulting in a serious grass-livestock imbalance.The reclaimed areas of Shangkuli farm and Taohai pasture fluctuated upward,peaking at 37000 and 7000 hm^(2) respectively in 2014.Since then,the reclaimed areas have decreased due to the policy of returning farmland to forest.The results of principal component analysis(PCA)using climate,grazing,reclamation,and grassland degradation in this area showed that overgrazing was the dominant factor leading to grassland degradation in the ecotone under scenarios of regional climate warming and drought.These findings suggest the need to strengthen the construction of grassland supervision and management systems to cope with the dual pressures of regional climate change and land degradation.The reward and subsidy funds from the central government should be used to return farmland to forest and grassland and herdsmen’s animal husbandry.Furthermore,we suggest that local governments establish multiple species artificial grasslands and adopt new technologies to restore and reconstruct degraded grassland to achieve sustainable utilization of grassland resources in the forest-steppe ecotone of northern China.