【作者】 杨阳；

【导师】 安韶山；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2019， 博士

【摘要】 黄土高原植被恢复过程中,植被与土壤的生态环境效应及其带来的一系列生态福祉是维持该区域可持续发展的关键性因素。植被恢复促进了土壤的恢复和生态系统服务功能的提升;反过来,土壤的恢复和生态系统服务功能的提升有利于植被的重建。然而,这仅仅是阶段性取得的系列研究成果,植被恢复与土壤的生态环境效应及其带来的生态系福祉的长期效应仍需要进一步考虑。为此,本文选择黄土高原4个典型小流域(纸坊沟、坊塌、董庄沟和杨家沟),利用1998、2008年和2018年遥感解译数据,实际测量数据,降雨数据,社会经济数据,退耕还林、实地勘测的植被与土壤等数据,研究了黄土高原4个典型小流域植被和土壤恢复特征,并采用In VEST模型对1998-2018年不同典型小流域的土壤保持功能、碳储存功能、水源涵养功能和生境质量进行了综合评估,从小流域植被恢复的时空尺度上,探究黄土高原典型小流域生态系统服务功能权衡/协同的时空分布特征,以此评估植被恢复与生态系统服务功能的平衡与互促作用,对实现黄土高原植被恢复过程中经济发展与生态环境保护具有重要意义。其结论如下:(1)黄土高原4个典型小流域植被恢复促进了植物群落多样性、土壤养分和微生物群落多样性的提高,由于土壤养分为土壤微生物群落提供了营养来源,二者在植被恢复过程中表现出同增同减的协同模式,并且这种协同促进在各流域的不同土地利用类型之间均有所体现。纸坊沟流域和坊塌流域人工草地土壤水分和有机碳含量最低,退耕草地最高;董庄沟流域和杨家沟流域土壤水分和有机碳大小依次表现为退耕草地>人工林地>灌丛>耕地。纸坊沟流域和坊塌流域人工草地土壤有效养分(速效磷、铵态氮、硝态氮、微生物量碳和微生物量氮)最小,退耕草地最大,董庄沟和杨家沟流域土壤有效养分退耕草地最大,耕地最小。纸坊沟流域和坊塌流域土壤细菌和真菌Shannon和Simpson指数均表现为退耕草地>人工灌丛>自然灌丛>人工林地>耕地>人工草地,董庄沟流域和杨家沟流域土壤细菌和真菌Shannon和Simpson指数均表现为退耕草地>灌丛>人工林地>耕地。在细菌群落中,4个典型流域主要的门类,包括Actinobacteria(放线菌门)、Proteobacteria(变形菌门)、Chloroflexi(绿弯菌门)和Acidobacteria(酸杆菌门),其中退耕草地Actinobacteria平均丰度最大,耕地Proteobacteria平均丰度相对较大;对于真菌群落,主要的门类包括Ascomycota(子囊菌门)和Basidiomycota(担子菌门),其中退耕草地和自然灌丛Ascomycota相对丰度较大,耕地和人工草地Basidiomycota相对丰度较大。由此说明在黄土高原,不管区域差异和土地利用的差异变化,其主要的微生物群落群落分布保持一致,具有一定的相似性,而不同土地利用导致了不同微生物群落的相对丰度有所差别,不同典型小流域土壤养分(除了全磷)与微生物群落Shannon指数均呈显著的线性相关。(2)植被恢复促进了NDVI和NPP的提高,其中NDVI和NPP在1998-2018年间大幅提升,虽存在NDVI和NPP降低的区域,但面积较小,NDVI和NPP整体上呈增加趋势,其中1998-2008年呈微弱的增加,为植被恢复期;2008-2018年急剧增加,期间伴有波动性变化,为植被恢复显著期。纸坊沟流域1998-2018年草地面积呈增加趋势,增加比例达33.84%,2008-2018年增加幅度高于1998-2008年;耕地、梯田和灌木面积呈减小趋势,主要转为草地和林地;坊塌流域1998-2018年林地和草地面积呈增加趋势,林地面积增加比例为4.57%;草地面积增加比例为10.05%,耕地和梯田面积呈减小趋势,主要转为草地,灌木和林地;董庄沟流域1998-2018年林地和草地面积呈增加趋势,耕地面积呈减小趋势,减小比例约为24.48%,耕地主要转为林地和草地,其中林地转移比例约为7.99%,草地转移比例约为15.22%;杨家沟流域1998-2018年林地面积呈增加趋势,草地面积呈减小趋势,草地主要转为林地,其中林地转移比例约为37.01%。(3)植被恢复过程中,自然因素和土地利用是影响植被NDVI和NPP的主要因素。对于自然影响因素,植被NDVI和NPP主要受到温度和蒸发量、降水量与总人口的影响,其中纸坊沟流域和坊塌流域,温度、降雨量和总人口对NDVI和NPP的贡献率最大;董庄沟流域和杨家沟流域温度和降雨量对NDVI和NPP的贡献率最大。对于土地利用的影响因素,纸坊沟流域和坊塌流域林地净变化量对NDVI和NPP的贡献率最大,董庄沟流域草地净变化量对NDVI和NPP的贡献率最大,杨家沟流域林地净变化量对NDVI和NPP的贡献率最大;而耕地净变化量、建设用地净变化量和未利用地净变化量对NDVI和NPP的贡献率最小,这几种土地利用类型的转化对NDVI和NPP的贡献率较小。(4)植被恢复促进了生态系统服务功能(土壤保持量、碳储量、产水量和生境质量)的增加,其中在1998-2008年(植被恢复期)增加较快,而2008-2018年(植被恢复显著期)增加较为缓慢;植被恢复与生态系统服务功能的增加并非同步性,生态系统服务功能的增加滞后于植被恢复,但整体上二者呈协同促进的模式。1998-2018年4个典型小流域大部分区域生境质量增加,少部分区域生境质量减小,空间上生境质量呈增加趋势,主要原因是20年间退耕还林还/草工程的实施。(5)生态系统服务功能重要区划分显示:黄土高原不同典型小流域1998-2018年生态系统服务功能重要区域面积所占比重较高,仍需要一定的保护。其中1998-2008年纸坊沟流域和坊塌林地、灌木和草地各生态系统服务功能呈增加趋势,耕地和裸地呈减小趋势,建筑用地和道路各生态系统服务功能基本保持不变,并且相对较少;1998-2008年董庄沟和杨家沟流域林地和草地各生态系统服务功能呈增加趋势,建筑用地、裸地和道路各生态系统服务功能基本保持不变,并且相对较少。2008-2018年纸坊沟流域和坊塌流域土壤保持功能一般重要区域面积所占比重较高,其次是比较重要区域;2008-2018年董庄沟流域和杨家沟流域土壤保持功能一般重要区域面积所占比重较高,其次是比较重要区域。(6)植被恢复过程中,自然因素和经济特征是影响植被生态系统服务功能的主要因素。其中,纸坊沟流域和坊塌流域人工林地、人工灌丛和自然灌丛总人口和蒸发量对碳储量和土壤保持功能起到负的影响作用;耕地和退耕草地总人口和GDP对碳储量和土壤保持功能起到正的促进作用。杨家沟流域和董庄沟流域人工林地和灌丛总人口和蒸发量对碳储量和土壤保持功能起到负的影响作用;耕地和退耕草地总人口和GDP对碳储量和土壤保持功能起到正的促进作用。生境质量的回归系数基本与其他服务功能相一致,除了经济因素和降雨蒸发的影响外,植被多样性因素对生境质量也起着重要作用。此外,土壤养分特性、土壤物理特性等自然环境因素也是影响该区域生态系统服务功能的重要驱动因素。(7)植被恢复过程中,生态系统服务功能权衡与协同关系共存,但主要表现为同增同减的协同关系,局部表现为此消彼长的权衡关系;整体上以(时间尺度)相互促进的关系为主导,伴有局部的空间制约关系(空间尺度),这种促进与制约关系用以维持生态系统的各项物质和功能的平衡发展。具体来看,1998年纸坊沟流域生态系统服务综合作用结果以协同作用为主,2008和2018年生态系统服务综合作用结果以权衡为主。1998和2018年坊塌流域生态系统服务综合作用结果以权衡作用为主,2008年生态系统服务综合作用结果以协同作用为主。1998-2018年董庄沟和杨家沟流域生态系统服务综合作用结果以权衡作用为主。同种土地利用类型生态系统服务功能有所差异,同种生态系统服务功能在不同地类上的发展情况也有所不同。总体来看,水源涵养、碳储量和土壤保持量呈明显同增同减的协同关系,主要是由于在植被恢复的不同时期,生态系统服务功能在时间和空间上增加或者降低的幅度并不一致,导致生态系统服务功能在时间和空间上与植被恢复进程并非同步,从而造成了生态系统服务功能在时间和空间上呈协同和权衡关系。更多还原

【Abstract】 Ecological and environmental effects and mostly ecosystem services functions due to vegetation restoration were regarded as the critical factors for maintain for sustainable development for vegetation restoration on the Loess Plateau.Vegetation restoration promoted soil restoration and the improvement of ecosystem services.In turn,soil restoration and the improvement of ecosystem services are conducive to vegetation reconstruction.However,this is only a series of progresses in stages,and the long-term effects of vegetation restoration on ecosystem service functions still need to be further studied.Here,we selected Zhifanggou,Fangta,Dongzhuanggou and Yangjiagou four typical small watershed on the Loess Plateau,and assessed soil conservation,carbon storage,water conservation and habitat quality by using remote sensing interpretation data,including the measurement data,rainfall data,social and economic data from 1998 to 2018.Thereafter,we explored the characteristics and spatial distribution of ecosystem service tradeoffs of these typical small watersheds,which are benefit to ecological development and environmental protection in terms of vegetation restoration on the Loess Plateau.We get these conclusions:(1)We found that vegetation restoration promoted soil nutrients(including available nutrients)and microbial community diversity in different typical small watershed,and soil nutrients and and soil microbial community diversity showed the synergy pattern due to soil nutrients provide a nutrient source for soil microbial communities,further,this synergy pattern was reflected in different land use types in each watershed.Specially,soil total porosity was higher in cultivated land,artificial grassland and artificial forestland,and lower in natural grassland,artificial shrub and natural shrub in terms of zhifanggou and fangta,while there was an opposite trend in dongzhuanggou and yangjiagou.Soil moisture and organic carbon content was lower in artificial grassland,and higher in natural grassland in terms of zhifanggou and fangta.In dongzhuanggou and yangjiagou,soil moisture and organic carbon content ordered as natural grassland > artificial forest > shrub > cultivated land.Similarly,soil available nutrients showed the same change trend with soil organic carbon.Moreover,soil microbial diversity(Shannon and Simpson)showed artificial shrub >natural shrub > artificial forest > natural grassland > artificial grassland in terms of zhifanggou and fangta,and natural grassland > shrub > artificial forestland > cultivated land in dongzhuanggou and yangjiagou.In these watersheds,Actinobacteria,Proteobacteria,Chloroflexi and Acidobacteria was the main bacterial community,and the average abundance of Actinobacteria in natural grassland was higher,while the average abundance of Proteobacteria in cultivated land was higher.Ascomycota and Basidiomycota was the main fungal community,and the average abundance of Ascomycota in natural grassland and shrub was higher,while the average abundance of Basidiomycota in cultivated land and artificial grassland.The results indicated that in the Loess Plateau,regardless of regional differences and the difference of land use change,the main distribution of microbial community community,has a certain similarity,and different land use has led to the relative abundance of the different microbial communities is different,different typical small watershed soil nutrient(except for total phosphorus)and microbial community Shannon index has significant linear correlation.(2)We also found that vegetation restoration promoted NDVI and NPP in different typical small watershed.NDVI and NPP showed a consistent trend from 1998 to 2018 in these watershed,and NDVI increased slightly from 1998 to 2008,while increased sharply from 2008 to 2018 with fluctuation.Actually,from 1998 to 2018,the area of grassland in zhifanggou increased(the increasing proportion was 33.84%),and the increased rate in2008-2018 was higher than that in 1998-2008,while the area of cultivated land,terrace and shrub decreased,mainly turning to grassland and foresland.The area of grassland(the increasing proportion was 10.05%),forestland(the increasing proportion was 34.57%)in fangta increased,but terrace and cultivated land decreased,mainly turning to grassland,shrub and forestland.The area of forestland and grassland in dongzhuanggou increased,while the area of cultivated land decreased.The cultivated land was mainly converted to forestland and grassland,and the converted proportion was about 7.99% and 15.22%respectively.The area of forestland in yangjiagou increased,while the area of grassland decreased.The grassland was mainly converted to forestland,and the converted proportion was about 37.01%.(3)Natural factors and land use changes were the main driving factors to NDVI and NPP in different typical small watershed.NDVI and NPP were negatively related with temperature and evaporation(P<0.01),and positively related with rainfall(P<0.01),and negatively related with total population(P<0.05).Grey correlation analysis showed that temperature,rainfall and total population had a higher comprehensive correlative degree(0.913,0.926 and 0.903),which had a large contribution to NDVI and NPP in zhifanggou and fangta,while temperature and rainfall had a large contribution to NDVI and NPP in dongzhuanggou and yangjiagou.Further,the net variation in forestland had a largecontribution to NDVI and NPP in zhifanggou and fangta,and the net variation in grassland had a large contribution to NDVI and NPP in dongzhuanggou,and the net variation in forestland had a large contribution to NDVI and NPP in yangjiagou.However,the net variation in cultivated land,construction land and unutilized land had small contribution to NDVI and NPP.(4)We also found that vegetation restoration promoted ecosystem services functions(Soil conservation,carbon storage,water yield and habitat quality)in different typical small watershed,and ecosystem services functions increased sharply from 1998 to 2008,while increased slightly from 2008 to 2018 with fluctuation.Although the progress of vegetation restoration was nonsynchronous with the increasing of ecosystem services functions,vegetation restoration and ecosystem services functions showed the synergy pattern.In addition,the habitat quality of most regions in these four typical small watershed increased,and the spatial habitat quality also increased,mainly due to the project of grain for green in the past 20 years.(5)There was a higher important area of soil conservation in these watershed,which should be protected.In particular,land use types had a large effect on ecosystem services function.Ecosystem services function in forestland,shrubs and grassland in zhifanggou and fangta increased,cultivated land and bare land decreased,and building land and roads remain unchanged with lower ecosystem services function.Ecosystem services function in forestland and grassland in dongzhuanggou and yangjiagou increased,and building land,bare land and roads remain unchanged with lower ecosystem services function.The proportion of the general important area of soil conservation was relatively higher,and then important area in zhifanggou and fangta.The proportion of the general important area of soil conservation was relatively higher,and then important area in dongzhuanggou and yangjiagou.(6)Natural factors and economic characteristics were the main driving factors to ecosystem services functions in different typical small watershed.We found that the regression coefficients about the total population and evaporation capacity to soil conservation function were negative in artificial forestland,artificial shrub and natural shrub in zhifanggou and fangta,while the regression coefficients about the total population and GDP to soil conservation function were positive in cultivated land and natural grassland.The regression coefficients about the total population and evaporation to carbon storage and soil conservation function were negative in artificial forestland and shrub,while the regression coefficients about the total population and GDP to carbon storage and soil conservationfunction were negative in cultivated land and natural grassland.The results of the regression coefficients in habitat quality was same in these watershed,besides,plant diversity had a large effect on habitat quality in these watershed.In addition,vegetation characteristics,soil nutrient characteristics,soil physical characteristics and other natural environmental factors also were the important driving factors to ecosystem service function.(7)Together,we found both of tradeoff and synergy among ecosystem service functions in different typical small watershed,while the pattern of synergy was dominant.It showed mutual promotion in time scale and mutual constraints in spatial scale.In doing so,it can be benefit to maintain the balance of the functions of the ecosystem in this region.Concretely,in 1998,ecosystem service integration exhibited synergy in zhifanggou,and exhibited tradeoff in 2008 and 2018.In fangta,ecosystem service integration exhibited tradeoff in1998 and 2018,while exhibited synergy in 2008.In dongzhuang and yangjiagou,ecosystem service integration exhibited tradeoff from 1998 to 2018.There was a significant positive correlation between carbon storage function and water conservation function(P<0.05),and significant positive correlation between water yield and water conservation function(P<0.05),while no significant correlation between habitat quality and other ecosystem service function(P>0.05),suggesting that habitat quality had a strong spatial heterogeneity.In addition,there was a difference in ecosystem service function in the same land use type,and there was a difference in land use type in the same ecosystem service function.In total,soil water conservation,carbon storage and soil conservation showed synergy of the same increase with the same decrease.This was the main reason that ecosystem service functions increased or decreased in different degrees during the periods of vegetation restoration,thus resulting in that the shifts of ecosystem service functions were not synchronized with vegetation restoration at spatial and temporal scale,and then some kinds of ecosystem service functions showed the synergy and tradeoff at spatial and temporal scale.Although,we found the shifts of ecosystem service functions were not synchronized with vegetation restoration,vegetation restoration promoted and improved ecosystem service functions from1998 to 2018.The main function of ecosystem services showed the synergistic relationship,while some local region showed tradeoff among ecosystem service functions.In doing so,it can be benefit to maintain the balance of the functions of the ecosystem in this region.更多还原