Agricultural Vulnerability to Drought in China's Agro-pastoral Ecotone:A Case Study of Yulin City,Shaanxi Province

Agro-pastoral ecotone of northern China is the prominent area for agricultural production,but it is also the most typical ecological fragile area with frequent drought disasters.Taking Yulin City at Shaanxi Province in China as the case area,the paper aims to investigate the spatio-temporal changes of agricultural vulnerability to drought in China’s agro-pastoral ecotone in the period 2000 to2020.The results show that:1)the agricultural vulnerability to drought in Yulin City has shifted from high vulnerability in the period2000–2010 to low vulnerability in the period 2011–2020.2)There exist obvious spatio-temporal differences of the agricultural vulnerability to drought in Yulin City during the research period.3)Four sensitive events and 14 resilient events were identified in the research and the crops of Yulin had become more resilient to drought.Finally,the paper put forward with policy implications to make adaptive strategies of agriculture to climate change in China’s agro-pastoral ecotone in the future,e.g.,carrying out agricultural zoning based on agricultural production conditions,intensifying the construction of disaster prevention and relief system,and integrating with modern agricultural technology to develop new type agriculture.

Changes in soil carbon stocks and related soil properties along a 50-year grassland-to-cropland conversion chronosequence in an agro-pastoral ecotone of Inner Mongolia,China

Land use change significantly influences soil properties. There is little information available on the long-term effects of post-reclamation from grassland to cropland on soil properties. We compared soil carbon （C） and nitrogen （N） storage and related soil properties in a 50-year cultivation chronosequence of grassland in the agro-pastoral ecotone of Inner Mongolia. Field surveys on land use changes during the period of 1955-2002 were conducted to build a chronosequence of cropland of different ages since the conversion from grassland. The results showed that soil C and N storage, soil texture, and soil nutrient contents varied with land use types and cropland ages （P〈0.01）. In the 0-30 cm soil layer, the soil organic carbon （SOC） density was significantly lower in the crop- lands （3.28 kg C/m2 for C50 soil） than in the grasslands （6.32 kg C/m2）. After 5, 10, 15, 20, 35, and 50 years of crop planting （years since the onset of cultivation）, the SOC losses were 17%, 12%, 19%, 47%, 46%, and 48%, respec- tively, compared with the grasslands. The soil total nitrogen （TN） density of the grasslands was 65 g N/m2, and TN density of the cropland soil was 35 g N/m2 after 50 years of crop planting. Both the SOC and TN densities could be quantitatively determined by a negative exponential function of cropland age （P〈0.0001, R2=0.8528; P〈0.0001, R2=0.9637）. The dissolved organic carbon （DOC） content, pH value were decreased; and the soil bulk density and soil available potassium （AK） content, clay content, and sand content were increased since the conversion of grassland into cropland during the 50-year period. Our results show soil nutrients were higher in grassland than in cropland. The conversion of grasslands to croplands induced a loss of soil C storage and changes of related soil properties. The reclamation time of cultivated soil （cropland age） had significant effects on soil properties in the study area.

Evaluation of Land Reclamation and Implications of Ecological Restoration for Agro-pastoral Ecotone: Case Study of Horqin Left Back Banner in China

The agro-pastoral ecotone has been recognized as the main distribution area of reserved land resource for cultivation. Accordingly, clarifying this assumption, as well as concerting land reclamation and ecological restoration, is important to ensure food security and environmental improvement in the agro-pastoral ecotone. We selected Horqin Left Back Banner(HLBB) as the subject of our case study. The landscape ecological security pattern of this area was determined using the minimum cumulative resistance model. Over-cultivation, quantity of reserved land resource for cultivation, and changes in landscape indexes before and after land use adjustment were then analyzed. Over-cultivation is a serious problem in the agro-pastoral ecotone. Reserved land resource for cultivation is less than that considered previously, and the area of reserved land resource for cultivation in HLBB only accounts for 11.50% of total uncultivated land. With regard to changes in landscape indexes, the adjusted land use pattern is effective for anti-desertification. The compensation standard for abandoned cultivated land should be improved and the comprehensive results of ‘Grain for Green' should be evaluated to further implement ecological restoration in the agro-pastoral ecotone.

Wavelet analysis of spring climate characteristics in arid aeolian area of agro-pastoral ecotone in China

The unique regional climate characteristics are among the main reasons for the frequent wind-sand activity in arid and cold areas in the agro-pastoral ecotone in Inner Mongolia, China. This paper focuses on the time series of temperature and precipitation in spring when sandstorms often occur in the area. Based on meteorological data for a 46-year period from 1959 to 2004, multi-scale variations and abrupt changes in temperature and precipitation were analyzed with the Mexican hat function （MHF） wavelet method, showing the multi-scale variation characteristics of temperature and precipitation, as well as the periods and change points at different time scales. The relationship between temperature and precipitation was obtained using the wavelet analysis method. Obvious staggered features of the variations of spring temperature and precipitation were observed in this agro-pastoral ecotone. The strongest oscillation periods of spring temperature variations were 1 and 22 years, while for precipitation, the strongest oscillation periods of variations were 2, 8, and 22 years. In addition, lower spring temperature corresponded to lower precipitation, whereas higher temperature yielded higher precipitation rate.

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.

Exploring the spatio-temporal impacts of farmland reforestation on ecological connectivity using circuit theory:A case study in the agro-pastoral ecotone of North China

Farmland reforestation can contribute substantially to ecological restoration.Previous studies have extensively examined the ecological effects of farmland reforestation,but few of them have investigated the spatiotemporal responses of broad-scale landscape connectivity to reforestation.By using a typical agro-pastoral ecotone in northern China as a case study,we addressed this issue based on an innovative integration of circuit theory approach and counterfactual analysis.The forest connectivity through multiple dispersal pathways was measured using the circuit theory approach,and its spatiotemporal changes after reforestation were evaluated by counterfactual analysis.The results showed that from 2000–2015,the reforested farmland occupied 2095 km^2,and 12.5% was on steeply sloped land.Farmland reforestation caused a greater increase in ecological connectivity by adding new ecological corridors and stepping stones in scattered forest areas rather than in areas with dense forest distributions.The newly added corridors and stepping stones were fragmented,short and narrow and thus deserve powerful protection.Future reforestation to improve landscape connectivity should highlight pinch point protection and obstacle removal as well as the tradeoff between farmland loss and farmer survival.Our findings are expected to inform the optimization of the Grain for Green policy from the perspective of broad-scale biodiversity conservation.

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 engineering and its role for sustainable agriculture in the agro-pastoral ecotone:A case study of Yulin, Shaanxi Province, China

With global climate change, the agricultural light-temperature potential productivity in the agro-pastoral ecotone has increased. This offers a good opportunity to develop agriculture in the agro-pastoral ecotone. However, the agro-pastoral ecotone is also an ecologically fragile area in which land degradation challenges agricultural development. As population grows and the need for food increases, the land carrying capacity of the agro-pastoral ecotone becomes insufficient, and the human–land relationship is not harmonious. Such conditions have limited the agricultural and rural development in the ecotone. The paper demonstrates how land engineering may improve land quality and support agricultural development in the ecotone based on studies at a research station established in 2015 in Yulin,Shaanxi Province, China. The studies target three factors: soil improvement, crop selection,and field management. The results show that:(1) The highest yield of crops planted on improved land is close to or even higher than that achieved under previous crop growth conditions. For instance, the corn yields can exceed 25%.(2) The potatoes grown on the improved land yield the highest gross income, reaching 67,200 yuan/ha. By way of land engineering,input costs can be balanced in 3–5 years.(3) As a result of land engineering, some villages in Yulin City have realized sustainable agricultural and even rural development, and promotion of this model will support the sustainable development of agriculture in the agro-pastoral ecotone.

退耕还林(草)工程对中国北方农牧交错带生态系统健康的影响

生态系统健康是生态环境治理的目标,探究国家级生态修复项目退耕还林(草)工程对中国北方农牧交错带生态系统健康的影响,确定合理的生态环境恢复和资源管理策略,有助于加快生态环境建设、促进区域可持续发展。基于“压力-状态-响应”(PSR)模型,构建起一套包括自然、社会和经济等方面的综合指标体系,评估了2000年、2005年、2010年和2015年中国北方农牧交错带的生态系统健康水平,利用Moran′s I分析退耕还林(草)工程和区域生态系统健康的空间相关性,并从普通最小二乘法、地理加权回归模型、时间加权回归模型和时空地理加权回归模型中,选择最优回归模型,揭示退耕还林还草实施强度变化(△NDVI)对生态系统健康变化(△EHI)的影响机制。结果表明:(1)2000—2015年,中国北方农牧交错带的生态系统健康指数呈现“先下降后上升”的变化趋势,区域整体处于亚健康状态和一般健康状态,健康状况逐渐转好。(2)全局双变量Moran′s I结果显示,在2000—2010年工程的开始和发展阶段,退耕还林(草)工程对生态系统健康呈现正相关影响关系,而2010—2015年间,两者之间变为负相关关系。(3)多种回归模型相比较,GTWR模型表现最优。在2000—2010年间,退耕还林(草)工程对研究区域东北部生态系统健康变化具有显著正向影响,在2010—2015年间,该区域由正向驱动变为负向驱动;中部地区则一直保持正向驱动;西南部地区则呈现“负向驱动—正向驱动—负向驱动”的波动变化情况。

人工自然交错带生态安全格局构建研究——以西安市鄠邑区为例

城市扩张造成秦岭北麓生态交错带环境发生显著退化,如何针对生态交错带特征开展区域生态修复,成为亟待研究的规划技术问题。文章借鉴生态安全格局构建的一般方法,结合秦岭北麓人工自然交错带、山地平原过渡带的生态特殊性分析,选择西安市鄠邑区为对象开展研究,提出适宜人工自然交错带的景观格局分析4步骤,包括:生态源地识别、阻力面构建、生态廊道识别、交错带景观资源整合,并基于此提出了秦岭北麓生态交错带修复的基本思路与分区策略。

Environmental variables vis-a-vis distribution of herbaceous tracheophytes on northern sub-slopes in Western Himalayan ecotone

Background:In the northern hemisphere,the north face of the mountains has a high diversity of species which is attributed to the moist and shady conditions at the north face.Other environmental variables may also influence the species diversity on the northern faces of the mountain and therefore needs to be studied in detail.The northern slopes represent three different sub-slopes—north,north east,and north west.During the current investigation of Pir-Panjal and Dauladhar ranges in Bhadarwah valley,fine-scale studies on the relationship between vegetation and four variables(soil pH,moisture content,electrical conductivity,and steepness)were conducted.The study determined the role of these variables on the vegetation of three different sub-slopes.The sampling was done at the confluence of two communities(forest and grassland)at three sites on the northern sub-slopes of the lesser stratum in western Himalayan.Results:The result revealed that rich herbaceous diversity prevails on the lesser Himalayan stratum(Bhadarwah valley).As many as 65.8%species differ from site to site,whereas species commonality among the sites is minimum.The role of environmental variables on the species composition at different sub-slopes of the north mountain face is deduced through canonical correspondence analysis(CCA).Conclusions:The availability of solar light increases air and soil temperature on the north east–facing slope.All the environmental variables(soil pH,moisture,electrical conductivity,and mountain steepness)are insignificant at pure north face for the species composition.Therefore,it can be concluded that some other environmental variables may influence the species composition which are needed to be further investigated.

北方农牧交错带免耕对农田耕层土壤温度的影响

针对北方农牧交错带部分地区免耕措施生态效益好但作物产量有所下降的现状,为了找出影响作物生长的因素,对比分析了免耕和翻耕两种耕作方式下耕层土壤温度的变化。结果表明:免耕地升温和降温都比较缓慢且幅度小,翻耕地土壤温度在日间总体高于免耕地。在垂直方向上,土壤温度随土层深度降低,但一天中不同时刻的表现差异显著。土壤温度变化与当时气温呈正相关关系,相关系数大于0.5。与免耕地相比,翻耕地气温与土壤温度的直线回归关系更显著。受土壤温度等物理性状的影响,免耕地作物生物量及产量明显不如翻耕地。因此,北方农牧交错带要通过农艺措施改善土壤物理结构,提高免耕农田作物产量。

北方农牧交错带土壤风蚀沙化影响因子的风洞试验研究

土壤风蚀沙化是北方农牧交错带农牧业生产与发展的主要限制因子,通过室内风洞实验研究,定量分析了土壤风蚀率(风蚀强度)与风速及土壤水分的相关关系、土壤风蚀输沙量的空间分布规律以及翻耕后土壤风蚀的动态变化。结果表明:风蚀率与风速变化成正相关,随着风速增大,风蚀率相应增加,18m/s风速是风蚀由轻变重的一个转折点;土壤水分与风蚀率呈负相关,水分含量越高,风蚀率越小,6%含水量水平是土壤风蚀由重变轻的一个转折点。通过曲线拟合表明,风蚀率与风速成幂函数的关系,与土壤水分含量成对数函数关系。土壤风蚀空间不同高度输沙量呈单峰曲线的变化趋势,在距地面2～4cm范围内集沙量最多,80%左右的沙量集中在近地面10cm范围内。土地翻耕是加重土壤风蚀的重要因素,对于天然草场,翻耕后风蚀强度是未翻耕的66～306倍,对于旱作农田,留茬覆盖可以有效控制土壤风蚀,翻耕马铃薯地风蚀强度是留茬地的25～108倍。

阴山北麓农牧交错带带状留茬间作轮作防风蚀技术研究

针对内蒙古阴山北麓农牧交错带在冬春季地表大部分裸露、风蚀沙化严重的现状 ,结合当地实际 ,试验了小麦与马铃薯带状留茬间作的耕作措施 ,研究其抗风蚀的效果。结果表明 :该种措施在滞留积雪 ,增大土壤湿度 ;减少土壤水分蒸发速度 ,保持土壤墒情 ;增大地表粗糙度 ,降低近地面风速等方面比当地传统的秋耕翻地有明显的效果 ,从而有效地减少了耕地的土壤风蚀量。同时具有轮作培肥土壤和边际增产作用 ,小麦平均增产 14 .4 % ,马铃薯平均增产 8.1% ,是适应当地条件的有效、简单、经济可行的防风蚀方法。

新疆北部绿洲-荒漠过渡带植物种类多样性分析

在“国家重点基础研究发展规划项目”( G1 9990 4 35 - 3)的研究中 ,为了探索绿洲环境的特征 ,对新疆北部进行了植被生态学考察 ,比较分析了北疆的绿洲与荒漠、山地生物多样性之中的优势植物和特征植物。在考察中 ,采集植物标本 1 5 4种 ,隶属 34科 ,1 0 0属 ,其中发现1个新种 ,有中国新分布 3种 ,有 1 0 2种增添了在新疆的新分布地点。

华北农牧交错区饲用玉米覆膜和施氮的效应研究

【目的】针对华北农牧交错区饲草量少质差的现实问题,研究了生物产量较高的饲用玉米覆膜和施氮的效应,以生产高产优质节水饲草。【方法】采用田间试验与室内样品分析相结合的方法。【结果】覆膜使饲用玉米干物质增产23.8%,且显著地促进了玉米对氮素的吸收,提高了氮素的表观利用率与产投比,植株粗蛋白的含量增加,有效地改善了其营养品质;覆膜改变了玉米田的耗水时序规律,水分利用效率提高了10%以上。施氮实现了饲用玉米的生物产量与营养品质协同增长,且营养成分的增幅(含量和产量)成倍于生物产量的增幅,施氮在提高饲用玉米生物产量36.1%～39.5%的情况下,植株中粗蛋白、粗脂肪的含量分别提高了109%和145%,产量提高了160%和210%;裸地施氮量约200kg·ha-1、膜地不超过300kg·ha-1是兼顾玉米高产优质和土壤速效氮平衡的施用量。【结论】饲用玉米覆膜和施氮是华北农牧交错区发展高产优质节水饲草,缓解草畜矛盾,促进区域生态恢复和经济发展的有效技术措施。

农牧交错带粮草带状间作防风蚀保土效应的研究

在内蒙古阴山北麓地区的中部,年降水量平均只有280￣350mm。由于冬春季地表大部分裸露,风蚀沙化已相当严重,因此应控制耕作,鼓励农民种草,耕作种植模式应以粮草带状间作为主。试验结果表明:该模式可有效增加地表粗糙度,比对照裸地平均降低近地面5cm风速31.6%,风蚀量平均降低79.4%;减缓地表风蚀粗化,>1mm的砾石为对照裸地的25%;生物量达3773kg/hm2,是天然草场的5.7倍。同时具有轮作培肥土壤的的作用,是适应当地条件的有效、简单、经济可行的防风蚀方法。

近50年冀北高原土地利用变化的土壤生境效应

区域性土壤生境的变化 ,很大程度上取决于该区土地利用及其覆被的变化 .通过冀北高原近 5 0年不同时段的资料分析证实 ,大片天然草场无序垦为耕地的利用变化及伴随的管理粗放 ,致土壤生境发生系列负面效应 ,土壤养分逐年下降 .5 0年中 ,该区土壤有机质 ,N、P、K全量及速效态量分别以 36 90 %、6 7 77%、4 4 4 4 %、34 15 %、32 2 2 %、5 8 90 %、35 2 9%的降幅趋势性地下降 ;砂、粉、粘三项表征土壤物性特征的不同土粒含量则以 18 2 4 %、19 5 5 %和 12 2 9%升降皆有的幅度变化 .这一结果揭示 ,为确保区位重要、生境脆弱区的土地质量不因利用变化和随时间推移而下降 ,永续处于动态平衡 ,务必科学管理 。

北方农牧交错带典型农户系统的能值分析

本文通过对北方农牧交错带两个典型农牧经营的农户的生产系统进行能值分析研究后表明在该地区总体上他们仍未摆脱广种薄收的生产方式,能值产投比的增加是依靠畜群超载数量的增加,这样对环境产生了巨大的压力。因此应尽快建立严格的舍饲养殖和草畜平衡,控制畜群数量,调整结构,提高净能值产出率,降低系统的环境承载率,才能实现区域的可持续发展。

北方农牧交错带县域典型农业生态系统结构的对比演变

为了能准确地描述农业生态系统结构的合理性,并从时间序列上反映系统产业结构的动态演变特征,立足北方农牧交错带,在近31a的时间尺度上,以偏农区的榆阳区和偏牧区的乌审旗县域典型农业生态系统作为比较研究对象,采用系统组分优势度、系统结构优势度和系统稳定性指数作为研究模型,对两地农业生态系统的产业结构进行了综合分析和评价,显示种植业是偏农区农业生态系统的主导产业,其组分优势度在后期下降较快;林业在两地农业生态系统中的组分优势度均较小;畜牧业是偏农区最具发展潜势的产业,是偏牧区国民经济发展的支柱产业;渔业组分优势度在两地均为最小,基本对系统无贡献;偏农区农业生态系统结构较为优越,而偏牧区农业生态系统稳定性较为突出。结合研究结果,并就种植业、林业、牧业和渔业在北方农牧交错带偏农区和偏牧区的发展提出了建设性意见,以期为当地及北方农牧交错带农业生态系统产业模式优化和农牧业可持续发展提供理论依据和科学借鉴。