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.

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.

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.

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.

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.

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。

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。

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。

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。

基于能值理论的农牧交错带两个典型县域生态经济系统的耦合效应分析

农牧交错带生态经济系统耦合效应与区域经济的可持续发展紧密相关,该文运用能值理论与方法,首次提出了农牧系统耦合度的概念,并对农牧交错带两个典型县域的农牧系统耦合现状进行了分析。结果表明农牧耦合效果不好,主要表现为两种典型结构模式,一种以安塞县为代表,农牧能值总体利用率较高,但畜牧业内部结构偏重食粮动物使得高质能转化率低下;另一种以武川县为代表,农牧业结构总体上朝趋于协调方向发展,但畜牧业规模过大,由于草畜平衡严重失调,导致农牧系统耦合机制难以稳定。该文根据能值指标分析结果,还提出了提高农牧系统耦合的一些措施及关于产业结构调整的探讨。

北方农牧交错带干旱区保护性耕作对土壤水分的影响研究

为了揭示农牧交错地区不同农田耕作方式对其水分环境的影响过程及规律,选择翻耕地和免耕地两种土地耕作类型,分析不同耕作方式下土壤水分的时空变化情况.结果表明:①在作物生长的整个生育期内土壤水分含量有随降雨量周期变化的趋势,无论是何种耕作方式,除生育期降雨外,播前底墒也是土壤供水的重要组成部分;②土壤贮水能力免耕地大于翻耕地;0～80 cm土壤水分的空间剖面自上而下分为两个层次:表层失水层(0～30 cm)和中层贮水层(30～80 cm).③用SPSS统计软件进一步对土壤水分与土层深度的关系进行拟合,结果表明土壤水分与土层深度的关系具有极强的相关性,其关系方程为拟和三次抛物线型.

干旱区保护性耕作对土壤水分的影响研究

为了研究保护性耕作对土壤水分的影响,选择翻耕地和免耕地两种土地耕作类型,分析不同耕作方式下土壤水分的时空变化规律。在保护性耕作实行的两年时间里,测定了土层不同深度土壤水分,结果表明:(1)在作物生长的整个生育期内土壤水分含量有随降雨量周期变化的趋势,无论是何种耕作方式,除生育期降雨外,播前底墒也是土壤供水的重要组成部分;(2)土壤贮水能力免耕地都是大于翻耕地的;0-80cm土壤水分的空间剖面自上而下分为两个层次:表层失水层(0-30cm)和中层贮水层(30-80cm)。(3)用SPSS统计软件进一步对土壤水分与土层深度的关系进行拟合,结果表明土壤水分与土层深度的关系具有极强的相关性,其关系方程为拟和三次抛物线相型。

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。

北方农牧交错带人口胁迫与耕地利用的相互关系

该文以我国北方农牧交错带内的安塞县为例 ,构建了一个适合于区域范围、人与耕地关系简单平衡模型 ,并从中推出了人与耕地关系平衡胁迫力计算式。在分析该县农业生产用地构成、耕地及粮食的历史动态变化之后 ,根据人口预测结果与有关参数值 ,以 5年为步长计算分析了 2 0 0 0～ 2 0 30年 ,不同粮食自给水平下的人口承载能力胁迫力、耕地面积需求胁迫力、耕地生产率胁迫力。确定了有利于实现“退耕还林草”生态环境建设的较合理的粮食自给率 。

中国东北样带生物群区及其对全球气候变化响应的初步探讨

本文应用室内模拟与野外实地调查相结合的方法，对中国东北森林草原样带上生物群区及其过渡带的位置与面积进行了判定，并预测了未来全球变化条件下生物群区及过渡带可能的变化趋势。结果表明：中国东北样带内的生物群区和过渡带可由基于气候数据和Ｈｏｌｄｒｉｄｇｅ方法的数量模型较确切地判定出，与实际调查的结果吻合较好。在未来气候变化下，过渡带面积呈扩大化趋势；森林区对降水量的变化反应敏感；草原区地理分布位置变动很大，但其相对面积变化较小；荒漠灌丛对全球变化的反应最为剧烈。

发展草地农业是农牧交错带农业结构调整的出路

农牧交错带的农业产业结构调整在生态环境不断恶化、农民收入增长乏力的状况下势在必行。本文分析了农牧交错带生态经济的现状,明确了生态经济理论应作为农业产业结构调整的主要理论依据,并指出实行人工种草、舍饲养殖,发展草地农业、畜牧业是农牧交错带农业结构调整的出路。最后,提出了结构调整的关键措施。

中国北方农牧交错带草地植被波动理论与实践

植被波动是植被动态学的重要组成部分,中国北方农牧交错带草地植被波动特征较南方森林群落波动存在较大差异.该文在生态学、统计学的基础上,结合草地植被特征,对草地植被波动及波动率进行定义,并首次组建了草地植被波动测度公式,同时采用专家评分法确定波动系数.在波动率公式构建的基础上,以宁夏盐池县为例,研究北方农牧交错带草地植被数量波动及波动率.结果表明,盐池县2002—2006年草地植被波动率正向波动2003年最大,为0.685,是近年来植被生长状况最好的一年;负向波动以2005年的-1.098的绝对值最大,表明2005年是近年来植被生长状况最差的一年.

关于系统耦合理论的探讨

系统耦合理论是近年来研究的热点问题。以农牧交错带为例,针对在生态经济系统目前该理论的定量化方面研究不足的事实,提出用能值方法考虑农牧交错带系统耦合的机制,并指出农牧交错带系统耦合机制应建立在土地利用方式、子系统间能值转化过程和生态系统的能值储备上;同时影响系统耦合机制的主要因素有初级生产力的大小、畜牧业的内部结构和畜牧业的发展规模以及生态系统服务价值的大小。还探讨性地提出系统耦合度的概念化公式,期望能更好地应用并发展这一理论。

中国北方农牧交错区生态脆弱性时空演变格局与驱动因素——以盐池县为例

生态脆弱性是当前全球环境变化与区域可持续发展研究的重点,也是生态文明建设和绿色发展研究的热点。以中国北方农牧交错区盐池县为例,基于2000—2017年3期遥感数据,运用景观格局指数法、空间自相关以及地理探测器等模型对研究区生态脆弱性时空演变格局及其驱动因素进行综合评价。结果显示:(1)研究区草地分布广泛,且面积逐年增加,耕地和未利用地面积分别减少44673.7 hm^(2)和73033.1 hm^(2),林地、水域和建设用地面积增加迅速,年均变化率分别为2.86%、2.15%和4.80%;(2)景观斑块数量减少,破碎度趋于缓和,不同类型景观彼此之间具有良好的连接性,景观格局趋向规则、连续的整体演变;研究区景观生态脆弱性逐年下降,高脆弱分布区主要分布在北部的高沙窝镇、花马池镇以及西部的惠安堡镇,低脆弱区主要分布在东南部的麻黄山镇、大水坑镇以及青山乡等地区,且低脆弱区范围由东南向西北延伸;空间自相关Moran’s I大于0.52,表明存在正相关,空间具有显著的集聚性和异质性,且呈现出“东南低,西北高”的分布格局;地理探测器结果显示景观斑块数、破碎度、优势度以及香浓多样性指数是影响研究区生态脆弱性空间异质性的主要因素。

农牧交错带农业生态系统生产力的能值分析——以武川县为例

本文运用能值理论和方法,以农牧交错带的武川县为案例对该区域的农业生态系统的初级生产力、次级生产力、农牧系统耦合和农户经济生产力及10多年来的能值投入和产出进行了分析和评价,并结合当地的一些实际情况试图说明该区域的农业生态经济系统面临的问题和可持续发展的途径。