黄土高原水蚀风蚀交错带煤田开发区小流域植被恢复模式

Vegetation restoration model in a watershed of a coal mining area in the water and wind erosion crossing zone of the Loess Plateau.

该文以陕北神木县六道沟小流域为研究区,应用参与性农户评估方法（PRA）调查煤田开发对流域居民收入和流域可持续发展的影响,分析流域内主要植被的生长和土壤水分状况,探讨陕北特大型煤田开发基地的生态恢复模式,为煤田可持续开发提供科学依据。调查表明,煤田开发明显改变了流域内农民的收入结构和数量,工农收入比由1.4∶1（1993年）变为26.5∶1（2007年）,人均收入由830.0元增加为9 340.0元,增加了约10倍;收入的增加提高了流域农民对退耕还林（草）政策的认知度,高达95%的群众对退耕还林还草政策持肯定态度;流域内的土地利用方式有了明显变化,表现为种植业用地显著下降,由原来的31.3%下降为21.5%,而畜牧业用地（包括荒草地）从39.6%增加为52.4%,原因是煤田开发让大部分劳动力投入到煤矿生产中,部分耕地特别是坡耕地荒废,成为荒草地。流域内小叶杨人工乔木林85%以上林木生长老化、衰败,树高平均仅4~6 m,形成典型的低效、低产林,林地土壤水分亏损严重,0~50 cm土层含水量仅有3.85%;流域10年生人工柠条灌木林郁闭度只有0.2,并且深层土壤水分被过渡利用,200~600 cm层次平均含水量仅有4.1%;10年生人工紫花苜蓿草地土壤水分消耗也较显著,但程度明显低于人工柠条林地,且紫花苜蓿的存在促进了天然草本群落的演替。研究认为,在煤炭资源枯竭之前,进行有效的草本植被恢复,建立以草本植物为主体、草灌结合、具有高效生态效益和一定经济效益、有利于促进流域次生地带性植被自然生长的人工植物群落是流域有效的植被恢复模式。因此,保证流域形成具有一定郁闭度的优质放牧草原群落,在煤炭资源枯竭之后,流域经济可以顺利地由资源消耗型经济转为以放牧业为支柱产业的循环经济,实现流域的可持续发展。

This paper studies the effects of coal exploitation on farmers＇ incomes and on the sustainable development of the Liudaogou Watershed by participatory rural appraisal（PRA）,analyzes the growth patterns of predominant vegetation types and the soil water conditions,and discusses a plan for vegetative restoration at the main site of coal exploitation in the north of Shaanxi Province,northwestern China.The purpose is to put forward scientifically based measures for the sustainable development of coal mining areas.Results showed that coal exploitation significantly altered the distribution and amount of local incomes such that the ratio of incomes from industry and agriculture changed from 1.4∶1（in 1993） to 26.5∶1（in 2007） while per capita income increased from 830.0 to 9 340.0 RMB.The increase of income promoted the farmers＇ awareness of the policy of replacing farmland with either forests or grassland and 95% of farmers had a positive attitude towards it.Land use changed greatly： cropland decreased from 31.3% to 21.5% while pastureland increased from 39.6% to 52.4% due to the transfer of the work force from traditional cultivation to the coal industry.Poor growth in 85% of artificial forest of Populus simonii resulted in inferior woodland of low productivity having an average height of only 4-6 m and severe soil water deficits.Artificial shrubland coverage consisting of 10-year-old Caragana korshinski was only 20% and soil water was used excessively from deeper soil such that the average soil moisture was just 4.1% in the 200-600 cm layer.Pastures of 10-year-old Medicago sativa also showed soil water deficits,but soil moisture was higher than that under the 10-year-old C.korshinski,and M.sativa promoted the succession of natural grasses.These results indicate that herbaceous species should be the main choice for use in the process of vegetation restoration,while arboreal species are not suitable for planting in this area especially due to the prevailing soil water conditions.Therefore,it is suggested that before the exhaustion of the coal resources,restoring herbaceous vegetation and developing a high quality pasture community is the best means for establishing sustainable development in the watershed that can subsequently provide the basis for an economic transfer from a resource-depleted system to a rotating grazing system,following the demise of the local coal mining industry.