Drought and flood characteristics in the farmingpastoral ecotone of northern China based on the Standardized Precipitation Index

The farming-pastoral ecotone of northern China(FPENC)provides an important ecological barrier which restrains the invasion of desert into Northwest China.Studying drought and flood characteristics in the FPENC can provide scientific support and practical basis for the protection of the FPENC.Based on monthly precipitation data from 115 meteorological stations,we determined the changes in climate and the temporal and spatial variations of drought and flood occurrence in the FPENC during 1960-2020 using the Standardized Precipitation Index(SPI),Morlet wavelet transform,and inverse distance weighted interpolation method.Annual precipitation in the FPENC showed a slightly increasing trend from 1960 to 2020,with an increasing rate of about 1.15 mm/a.The interannual SPI exhibited obvious fluctuations,showing an overall non-significant upward trend(increasing rate of 0.02/a).Therefore,the study area showed a wetting trend in recent years.Drought and flood disasters mainly occurred on an interannual change cycle of 2-6 and 9-17 a,respectively.In the future,a tendency towards drought can be expected in the FPENC.The temporal and spatial distribution of drought and flood differed in the northwestern,northern,and northeastern segments of the FPENC,and most of the drought and flood disasters occurred in local areas.Severe and extreme drought disasters were concentrated in the northwestern and northeastern segments,and severe and extreme flood disasters were mainly in the northeastern segment.Drought was most frequent in the northwestern segment,the central part of the northeastern segment,and the northern part of the northern segment.Flood was most frequent in the western part of the northwestern segment,the eastern part of the northeastern segment,and the eastern and western parts of the northern segment.The accurate evaluation of the degrees of drought and flood disasters in the FPENC will provide scientific basis for the regional climate study and critical information on which to base decisions regarding environmental protection and socio-economic development in this region.

Spatiotemporal variation of forest land and its driving factors in the agropastoral ecotone of northern China

As an important natural resource,forest land plays a key role in the maintenance of ecological security.However,variations of forest land in the agropastoral ecotone of northern China(AENC)have attracted little attention.Taking the AENC as an example and based on remote-sensing images from 2000,2010 to 2020,we explored the spatiotemporal variation of forest land and its driving factors using the land-use transfer matrix,spatial autocorrelation analysis and spatial error model.The results showed that from 2000 to 2020,the total area of forest land in the AENC increased from 75,547.52 to 77,359.96 km^(2) and the changes were dominated by the transformations among forest land,grassland and cropland,which occurred mainly in areas with the elevation of 500-2000 m and slope of 15°-25°.There was obvious spatial agglomeration of forest land in the AENC from 2000 to 2020,with hot spots of forest land gathered in the southern marginal areas of the Yanshan Mountains and the low mountainous and hilly areas of the Loess Plateau.The sub-hot spots around hot spots moved southward,the sub-cold spots spread to the surrounding areas and the cold spots disappeared.The spatiotemporal variation of forest land resulted from the interactions of natural environment,socioeconomic and policy factors from 2000 to 2020.The variables of average annual precipitation,slope,terrain relief,ecological conversion program and afforestation policy for barren mountains affected the spatial pattern of forest land positively,while those of annual average temperature,slope and road network density influenced it negatively.

Strategies for Prioritizing Ecological Construction with Consideration of Agricultural Industry Development in Northern China’s Agro- pastoral Ecotone : A Perspective of Opportunity Cost

In northern China’s agro-pastoral ecotone,there are conflicts between agricultural industry and ecological construction resource competition,and also problems urgently to be solved for economic growth and sustainable ecological improvement.Taking the development concept of"lucid waters and lush mountains being mountains of gold and silver"as the guiding principle of prioritizing ecological and green development,this paper studied the strategies for prioritizing ecological construction with consideration of economic development of agricultural industry from the perspective of opportunity cost.Through the analysis of opportunity cost,externality,and Pareto optimal theory,and using the calculation method of the unit equivalent factor value of terrestrial ecological service function,this paper calculated the ecological service value of forest,grassland,and farmland.It found that the ecological value of forest and grassland per unit area was greater than the ecological value of agricultural industry.This indicates that the opportunity cost of farmland for ecological construction was less than that of agricultural industry.Based on the theoretical and quantitative analysis,it came up with recommendations for establishing a comprehensive system for prioritizing ecological construction with consideration of agricultural industry development and establishing and improving the incentive mechanism of ecological construction.

Development of quantitative methods for detecting climate contributions to boundary shifts in farming-pastoral ecotone of northern China

The quantitative effect of climate change on fragile regions has been a hot topic in the field of responses to climate change. Previous studies have qualitatively documented the impacts of climate change on boundary shifts in the farming-pastoral ecotone （FPE）; however, the quantitative methods for detecting climate contributions remain relatively limited. Based on long-term data of meteorological stations and interpretations of land use since 1970, climate and land use boundaries of the 1970s, 1980s, 1990s and 2000s were delineated. To detect climate contributions to the FPE boundary shifts, we developed two quantitative methods to explore the spatial-temporal pattern of climate and land use boundary at the east-west （or south-north） （FishNet method） and transect directions （Digital Shoreline Analysis System, DSAS method）. The results indicated that significant differences were exhibited in climate boundaries, land use boundaries, as well as climate contributions in different regions during different periods. The northwest FPE had smaller variations, while the northeast FPE had greater shifts. In the northwest part of the southeast fringe of the Greater Hinggan Mountains and the Inner Mongolian Plateau, the shifts of climate boundaries were significantly related to the land use boundaries. The climate contributions at an east-west direction ranged from 10.7% to 44.4%, and those at a south-north direction varied from 4.7% to 55.9%. The majority of the results from the DSAS were consistent with those from the FishNet. The DSAS method is more accurate and suitable for precise detection at a small scale, whereas the FishNet method is simple to conduct statistical analysis rapidly and directly at a large scale. Our research will be helpful to adapt to climate change, to develop the productive potential, as well as to protect the environment of the FPE in northern China.

Adaptation to a Warming-Drying Trend Through Cropping System Adjustment over Three Decades:A Case Study in the Northern Agro-Pastural Ecotone of China

Long-term field monitoring data and historical crop data are useful to assess the impacts of climate change and to manage cropping systems. The objectives of this study are to understand the cropping system response to a warming-drying trend in the northern agro-pastural ecotone （NAE） of China and to document how farmers can adapt to the warming-drying trend by changing cropping system structure and adjusting planting date. The results indicate that a significant warming-drying trend existed in the NAE from 1980 to 2009, and this trend significantly decreased crop （spring wheat, naked oat, and potato） yields. Furthermore, the yield decreased by 16.2%-28.4% with a 1℃ increase in maximum temperature and decreased by 6.6%-11.8% with a 10% decrease in precipitation. Considering food security, water use efficiency, and water ecological adaptability in the semi-arid NAE, cropping system structure adjustment （e.g., a shift from wheat to potato as the predominant crop） and planting date adaptation （e.g., a delay in crop planting date） can offset the impact of the warming-drying trend in the NAE. Based on the successful offsetting of the impact of the warming-drying trend in the NAE, we conclude that farmers can reduce the negative effects of climate change and minimize the risk of crop failure by adapting their cropping system structure at the farming level.

Impacts of regional land-use patterns on ecosystem services in the typical agro-pastoral ecotone of northern China

A comprehensive understanding of the spatial-temporal evolution and driving forces on ecosystem services(ES)is essential for the agro-pastoral ecotone’s ecological security in northern China.However,the land-use pattern(LULC)agglomeration with spatial differentiation in the pastoral and agricultural areas has been rarely concerned.Taking distinct LULC(1980-2018)in Chifeng as an example,we compared four crucial categories of ESs with InVEST.Using SEM,we further contrasted the effects of several variables on regional ES variations in pastoral-dominated(North)and agriculture-dominated(South)regions,respectively.Results revealed the conversion between forest and grassland oriented the LULC transformation in the North.In contrast,human-activitiy-oriented land tended to occupy environmentally sensitive places in the South.Similar ES variations were supplied with the North outperforming the South when soil conservation was omitted.As for the impacts of regional ES variations,the natural and LULC policies both showed positive effects,whereas the anthropogenic factors showed positive in the North,which was negative in the South.Therefore,the ecologicallymaintained-dominant and ecologically-restored-dominant strategies should be separately adopted in the North and South.Our study provided appropriate regional ecological management suggestions for balancing the LULC-driven conflicts between ecological protection and regional development.

Land use pattern evolution and optimization in the Farming-Pastoral Zone of Northern China

Using information about the land cover of the Farming-Pastoral Zone of Northern China retrieved from multi-temporal NOAA/AVHRR and SPOT VEGETAN images obtained in 1989, 1994 and 1999, the authors analyzed land-use pattern evolution over this 10-year period and built a land-use pattern simulation model, based on which land-use pattern evolution and optimization modeling in this region were studied. Results showed that the proposed model can effectively simulate regional land-use patterns and help improve regional ecological environments.

北方农牧交错带农牧系统养分流动特征及环境效应研究进展

北方农牧交错带跨度大、范围广、农牧兼有,是研究北方农牧业最具代表性的区域。养分流动直接反应养分循环状况,是农业生态系统平衡的重要表征之一,研究农牧系统养分流动对于发展可持续农牧业,减少环境养分负荷等具有重要意义。总结了农牧系统氮、磷、钾3种主要养分流动特征及其环境效应,提出了农牧系统养分循环亟待深入研究的重要方向,以期为后续农牧系统养分循环的理论研究、提高养分利用率技术手段的研发以及环境政策措施的制定提供借鉴与参考。

粮食单产视角下中国北方农牧交错带粮食安全研究

从中国北方农牧交错带粮食安全和粮食单产的重要性出发,利用空间自相关分析揭示带内粮食单产的空间分异及演化特征,作为划分农牧业发展地域的依据,进而利用地理探测器模型揭示控制单产分异的主导因子及其交互作用,藉此探讨提高带内粮食单产、保障粮食安全的对策。结果表明:(1)2000—2020年带内粮食单产呈现相对稳定的集聚分布态势,自然环境分异大势是其基础性控制因素,社会生产条件及其耦合水平则强化了粮食单产的空间分异特征。(2)单产热点区主要集中在带内东北部平原地区和西南部河湟谷地,冷点区分布在中部水土流失区和丘陵地区,次热和次冷点区则围绕热、冷点形成圈层结构;依据该格局可将热点区划分为宜农区,将次热和次冷区划分为农牧耦合区,将冷点区划分为生态修复区,以因地制宜地促进带内农牧业协调发展。(3)2000—2020年带内粮食单产的增长模式从以劳动力为主导转变为以现代农业技术为主导,但出现了劳动力与耕地、现代农业技术之间过度解耦,以及各种现代农业技术之间的耦合性不足等问题,因而提出了以“人-地-技”耦合发展促进粮食单产健康增长、提高粮食安全保障能力的建议。

北方农牧交错带人地系统耦合协调的时空特征及障碍因子

人地系统协调是实现可持续发展的重要前提,探究北方农牧交错带人地系统耦合协调特征及障碍因素,对适时推进乡村振兴、实现农牧区高质量发展具有重要意义。本研究基于人地系统类型结构,从农牧业、村庄、乡域、城镇4个层面构建指标体系,运用耦合协调度模型和障碍度模型,分析人地系统发展水平、耦合协调程度及人地系统协调的障碍因素。结果表明:2000—2020年,北方农牧交错带人地系统发展水平呈现上升性和空间非均衡性,农牧业、村庄子系统发展相对滞后,乡域子系统发展水平增幅明显;人地系统耦合度基本处于高水平耦合阶段,协调度稳步提高,整体由轻度失调衰退向勉强协调发展转变,空间上呈现由西北向东南递减的格局;阻碍人地系统协调水平提升的主要因素为乡村人均草地面积、人均GDP、乡村人均肉产量,且障碍程度不断增强;子系统障碍度顺序为农牧业>村庄>城镇>乡域,农牧业、村庄子系统障碍作用突出,乡域子系统障碍作用明显减弱。综上,北方农牧交错带人地系统耦合协调水平稳步提升,但仍面临农牧结构平衡、生态环境保护、三产融合发展等诸多挑战。

不同生态类型区对人类活动净氮输入的影响——以北方农牧交错带为例

为探究中国北方农牧交错带在不同生态类型区人类活动对净氮输入的影响,基于人类活动净氮输入模型(NANI),以北方农牧交错带7省、23地级市的统计数据及相关参数,分析1985~2020年NANI的时空分布特征及影响因素.结果表明:1985~2020年研究区NANI呈先上升后下降趋势,河北省贡献最高.黄土丘陵沟壑水土流失区与北方农牧交错带NANI年际变化一致、京津冀水源涵养区和长城沿线沙化退化区NANI年际变化值呈上升趋势.空间分布呈由西北向东南逐渐降低的趋势.从输入组分来看,研究区最大贡献源为氮肥施用(30.34%~56.29%),其次是大气氮沉降(31.20%~47.23%),黄土丘陵沟壑水土流失区主要输入组分为氮肥施用和食品/饲料氮输入(累计76.46%~85.14%).对北方农牧交错带NANI影响最大的两个因素为人口密度和畜禽量.因此,中国北方农牧交错带的农业结构调整需结合分区进行管控,调整氮肥使用策略和畜禽养殖模式,促进区域农牧业与生态环境之间的深度融合.

中国北方农牧交错带生态系统服务空间格局及影响因子——以内蒙古中西部地区为例

中国北方农牧交错带是我国重要的生态安全屏障之一,面临经济发展与脆弱生态环境保护间的突出矛盾。生态系统服务的定量研究是生态可持续管理的重要科学依据,也是当前的研究热点之一。以北方农牧交错带的核心区域--内蒙古中西部地区为例,结合中高分辨率遥感数据和生物物理模型准确量化了2000-2018年关键生态系统服务,基于Getis-Ord G*方法分析了生态系统服务的空间格局,考虑地理数据的空间自相关性选取了空间回归模型探索其影响因子。结果表明:(1)净初级生产力(NPP,Net primary productivity)、土壤水蚀控制服务(SC,Soil conservation)、产水量(WY,Water yield)及三层土壤含水量(SM1,Soil moisture of top layer;SM2,Soil moisture of middle layer;SM3,Soil moisture of bottom layer)在东部较高,防风固沙服务(SF,Sand fixation)在南部和西部较高;(2)以上生态系统服务受气候变化、景观格局、地形和土壤条件等综合影响,不同影响因素对生态系统服务的作用存在差异。NPP受森林景观格局和归一化植被指数的影响最为显著;WY、SM1、SM2、SM3及SC受降水量的影响较为显著;风速和表层土壤砂粒含量对SF影响最为显著。研究结果可以为优化景观格局和土地系统,缓解中国北方农牧交错带的社会-生态矛盾提供科学依据和案例参考。

北方农牧交错区不同播期和刈割期对燕麦饲草产量和品质的影响

为明确不同播期和刈割期对燕麦(Avena sativa L.)饲草产量和品质的影响,本研究以粮饲兼用燕麦品种‘白燕2号’为材料,于2018—2019年在内蒙古农牧交错区进行了5个播期和3个刈割期的田间试验。结果表明:推迟播种可获得相对较高的燕麦饲草产量和品质,但推迟播种提高了中性洗涤纤维和酸性洗涤纤维含量,其中酸性洗涤纤维含量受年份和刈割期影响较大;燕麦饲草粗蛋白含量受刈割时间影响显著(P<0.001),在抽穗期含量最高;燕麦饲草产量在灌浆期达到最大;生育期间积温对燕麦饲草生长影响显著,拔节到抽穗期的积温增加不利于燕麦饲草产量和品质的形成,但出苗到分蘖间的积温增加可提高粗脂肪和酸性洗涤纤维的含量。总之,在北方农牧交错区种植燕麦饲草‘白燕2号’,在5月中下旬之间播种,在灌浆期刈割,可获得相对优质高产的燕麦饲草。

北方草地及农牧交错区草地植被碳储量及其影响因素

【目的】草地生态系统在全球碳平衡中有重要的意义,草地植被碳库及其变化机制研究是植被生态学的重要命题。本文研究北方草地和农牧交错区草地植被碳密度及其空间格局,解析不同区域草地植被碳密度的关键影响因素,分析了气候、土壤、放牧等因素对地上地下植被碳库的相对贡献。【方法】基于2002—2009年北方草地及农牧交错带草地植被调查数据,结合同期MODIS/NDVI遥感影像和1﹕100万草地类型图,建立了我国主要草地类型的生物量估算模型;整合野外考察数据和前人研究结果,探讨了研究区地上地下生物碳库及其空间格局;基于研究区255个县级行政单元,分析了不同类型草地植被碳库与气候要素、土壤要素及家畜承载量的关系,应用一般线性模型(GLM)解析了不同影响因素对草地碳密度的相对贡献。【结果】(1)北方草地与农牧交错区草地地上平均生物碳密度为36.9 g C·m^-2,地下生物碳密度为362.9 g C·m^-2,地下生物碳密度高于地上10倍,均呈从东到西递减的趋势,频率分布图基本服从对数正态分布,不同草地类型的生物碳密度存在明显差异;(2)整个研究区及草原亚区、荒漠亚区、农牧交错亚区内,地上生物量与年降水量(MAP)呈极显著正相关、与年均气温(MAT)均呈极显著负相关,与土壤黏粒含量(Clay%)呈显著正相关、与土壤砂粒含量(Sand%)呈显著负相关,整个研究区家畜承载量与草地地上生物量之间呈极显著正相关;(3)一般线性模型(GLM)分析结果表明,年平均降水量(MAP)、年均气温(MAT)、土壤黏粒含量(Clay%)、放牧强度对地上生物量空间变异的解释率分别达到29.6%(P<0.001)、5.8%(P<0.001)、0.8%(P<0.05)、1.3%(P<0.001);地下生物量的空间变异主要来自于年降水量(MAP)、年均气温(MAT)、土壤砂粒含量(Sand%),对方差的解释率分别达到12.1%(P<0.001)、6.8%(P<0.001)、1.9%(P<0.005),放牧强度没有明显贡献。【结论】气候条件尤其是年降水量是草地生物量碳库的主要影响因素,但对地上生物量影响更为明显;土壤质地对植被生物碳库也有显著贡献,尤其对地下生物量的影响更加显著;放牧强度只能解释地上生物量变化的1.3%、对地下生物量没有显著贡献,这一发现意味着气候对生物量碳库的贡献远大于放牧影响。

北方农牧交错带参考作物蒸散量时空变化与成因分析

利用北方农牧交错带46个气象站1961-2013年气象资料,采用Penman-Monteith公式法计算该地区参考作物蒸散量(ET_0)、ET_0对气象因子的敏感性系数、气象因子对ET_0的贡献率,并通过趋势分析、GIS空间插值方法对这些指标的时空变化进行分析。结果表明:(1)北方农牧交错带年ET_0平均值在839~1097mm,近53a来以0.21mm·a^(-1)的速率减小。(2)空间分布上,ET_0总体呈现"一高二低"的分布格局:陕北高原为高值区,大兴安岭北部高纬地区、青东农区及陇中片区为两大低值中心区。且陕北高原、陇中及青东农区61%的站点ET_0平均以0.85mm·a^(-1)(P<0.05)的趋势递增,而吉林西部、科尔沁沙地、辽西地区则呈明显减小趋势。(3)气象因子对ET_0的贡献受ET_0对气象因子的敏感性和气象因子的相对变化共同影响,其中北方农牧交错带ET_0对相对湿度最敏感,其次为平均风速;但近53a来风速呈极显著下降趋势,下降速率达0.0154m·s^(-1)·a^(-1)(P<0.001),因此,综合分析结果表现为风速对ET_0的贡献量最大,说明北方农牧交错带ET_0下降主要归因于风速的降低。

我国北方农牧交错带的气候界线及其变迁

北方农牧交错带对于气候变化和人类干扰敏感,在我国经济、社会发展和环境保护方面具有重要的战略地位。因此,关于其气候界线及变迁的基础研究,可以为农牧交错带的其他深入研究提供科学支撑。文章基于北方236个气象站点1980～2009年的日气象资料,依据李世奎（20世纪80年代）提出的气候指标界定北方农牧交错带不同时段的气候界线,通过叠置法分析农牧交错带的核心区域及气候界线变迁。结果表明：现今（1980～2009年）农牧交错带的分布仍呈现出从东北至西南的带状格局,但范围整体较早期（20世纪80年代前）有所扩张,分布在内蒙古自治区的交错带面积最广。近30年来,农牧交错带的气候界线东西摆动,但整体上是向东迁移的。变化趋势与该区域降水量的变化具有一定的相关性,东北段变化幅度大,由于该区降水量减少而向东变迁;华北区的东部变化幅度较大,而其西部则变化幅度小;西北段则由于该区降水量增加而向西北延伸。

北方农牧交错带农田生态系统健康评价——以武川县为例

采用生态系统健康的理论和评价方法分析评价农田生态环境问题具有重要的理论和现实意义,应用生态健康指数定量评价农田健康水平是生态系统管理的重要内容。以武川县农田为研究对象,选择水分、生物量、幅宽等代表性指标,分析了不同作物覆盖下农田生态健康指数。结果表明:不同种植模式间农田健康指数差别明显。播种期较早的小麦田最为健康,没有采用地膜覆盖的马铃薯田健康指数最低,而采用地膜覆盖的马铃薯田健康指数比较高。推广小麦栽培和覆膜栽培是北方农牧交错带农田很好的经营管理模式,具有推广价值,是缓解该地区环境的有效手段之一。

北方农牧交错带农田水分生产潜力开发研究进展与思考

不合理的土地利用方式与利用强度导致农业用水不合理是造成北方农牧交错带生态退化的重要原因,适度开发利用农田水分是当前发展农业生产和重建生态系统的关键。分析了农田水分研究进展、农田水分生产潜力研究进展及当前农田水分生产潜力开发面临的新形势与新任务,提出要遵循适度原则合理开发利用北方农牧交错带农田水分生产潜力。初步辨识了农田水分生产潜力适度开发的基本内涵,提出了北方农牧交错带农田水分生产潜力适度开发的研究框架与关键科学命题。当前,要遵循农田水分适度开发的思想指导当地农业生产,恢复生态,促进北方农牧交错带的可持续发展。

气候和土地利用变化对中国北方农牧交错带植被覆盖变化的影响

基于1986、2000年中国北方农牧交错带的遥感影像及研究区的气象数据,利用植被覆盖度信息提取模型研究了1986—2000年间研究区植被覆盖度的时空变化,并分析了气候和土地利用变化对植被覆盖度变化的影响.结果表明:1986—2000年,研究区高盖度植被的面积缩减,低盖度植被的面积增加;植被覆盖升高区主要位于该区东北段的东部、北段的西部和西北段的西部,其他地段的植被覆盖明显退化;植被覆盖度与降水、干燥度指数呈正相关,与温度呈负相关;不同土地利用类型的植被覆盖度变化方向和程度各异.

北方农牧交错带生态系统服务价值测算及变化

基于1986年和2000年北方农牧交错带生态系统类型、NPP和植被覆盖度的分布,利用遥感和GIS技术,结合生态经济学方法,测算了北方农牧交错带生态系统服务功能的经济价值及动态变化。结果表明:(1)在生态系统服务价值的构成中,草地、农田和森林的贡献率最大;(2)从单位面积价值看,森林和灌丛服务功能的单位面积价值最高;(3)在水平分布上,生态系统服务价值的区域差异明显,其分布受气候和人类活动影响较大;在垂直分布上,地形因子对生态系统服务价值的影响较大,人类活动影响微弱;(4)1986～2000年间,各个生态系统服务功能的价值及其总价值都在下降,单位面积价值的最大值由东北向西南方向移动到交错带的中部。