Research Progress on Ecological Safety Assessment of the Farming-pastoral Ecotone in China

[Objective] The study was conducted to overview the farming-pastoral ecotone research progress in China.[Methods] Started from the influences on soil,precipitation and water conservation,climate and mulching of different land use types,the paper summarized the current research situation on several hot issues and proposed suggestions for future study.[Results] Researches on farming-pastoral ectone in China have achieved great progress,but still require more deep and comprehensive studies.Suggestions：Current studies should focus on solutions for degradation of farmland and grassland;Conduct deeper analysis on the relatively weaker aspects in a multi-domain fusion type;Implement the study results on eco-environmental recovery,production improvement and other practical activities;Lift the research of ecotone to a national or even global level,and make them far more comprehensive.[Conclusion] Provide theoretical basis for ecological protection of farming-pastoral ecotone in our country.

Mapping the Farming-pastoral Ecotones in China

Conventional farming-pastoral ecotones methods of delineating were not quantitative and could not fully show their spatial distribution. The present paper attempts to develop quantitative methods for mapping farming-pastoral ecotones in China. Nine indicators, related to temperature, precipitation and altitude aspects, were selected to quantify ecological susceptibility of vegetation （crops and forage）. Methods of analytic hierarchy process （AHP） and expert score ranking combined with fuzzy set theory were applied to assign the weight for each indicator and to define the membership functions. The geographic information system （GIS） was used to manage the spatial database and conduct the spatial analysis. According to the spatial calculation of evaluation model integrated with GIS, the ecological susceptibility of vegetation （crops and forage） was mapped. Three different zones, pastoral area, farming-pastoral ecotones and farming area, were classified by spatial cluster analysis and the maximum likelihood classification for the numeric map of vegetation ecological susceptibility by GIS. This map was validated by the economic statistical result based on the ratio of the output value from animal husbandry in total output value of agriculture by the National Bureau of Statistics in China, indicating that the mapping of the farming-pastoral ecotones may be accepted.

Alpine ecotone in the Siberian Mountains:vegetation response to warming

Birch(Betula tortuosa)is one of the treeline forming species within the Siberian Mountains.We analysed the area dynamics of birch stands and the upslope climb of birch treeline based on the Landsat time series scenes and on-ground data.We found that since the warming onset(1970th)birch area increased by 10%,birch stands and treeline boundary were moving upslope with a rate of 1.4 m/yr and 4.0 m/yr.Birch upslope shift correlated with air temperatures at the beginning(May-June)and the end(August-October)of the growth period.Meanwhile,no correlation was found between birch upslope migration and precipitation.Winds negatively influenced both birch area growth and birch upslope climb during spring,fall,and wintertime.In the windy habitats,birch,together with larch and Siberian pine,formed clusters(hedges)which mitigated the influence of adverse winds.These clusters are the adaptive pattern for trees’upslope climb within windward slopes.The other adaptation to the harsh alpine ecotone habitat is non-leaf(bark)photosynthesis which supports tree survival.Thereby,Betula tortuosa upslope climb depends on the wind impact and warming in spring and fall that extended growth period.With ongoing warming and observed wind speed decrease on the background of sufficient precipitation,it is expected to further birch advance into alpine tundra in the Siberian Mountains.

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.

Impacts of revegetation management modes on soil properties and vegetation ecological restoration in degraded sandy grassland in farming-pastoral ecotone

Focusing on the impact of various vegetation management modes on sandy grassland's soil property and vegetation ecological restoration of farming-pastoral ecotone,field surveys and lab analysis were conducted to study the correlation between the characteristics of soil properties and vegetation ecological restoration under four different vegetation management modes,i.e.,unenclosed natural restoration,enclosed natural restoration,unenclosed artificial restoration and enclosed artificial restoration,which have a restoration history of 15 years in the southern edge of the degraded sandy land area of Mu Us Desert in Leilongwan Town,Hengshan County,Shaanxi Province.After 15 years of vegetation restoration,these four vegetation management modes all proved to be useful for improving the vegetation ecological restoration and the soil quality of the degraded sandy grassland not only by enhancing the aboveground vegetation height,coverage and biomass but also increasing the content of soil clay,organic matter,CEC,total nitrogen,available nutrient while reducing soil bulk density.The vegetation ecological restoration effect and soil quality under enclosed or artificial restoration management are better than those of unenclosed or natural restoration management;and the most satisfactory vegetation ecological restoration effects and soil quality can be achieved under the integration of enclosed and artificial restoration management.Severely degraded sandy grassland,during the vegetation restoration,would form an interactional coordinating relationship with the vegetation and soil properties.Vegetation properties as height,coverage and biomass have significant positive correlations with organic matter,CEC,total nitrogen and available nitrogen,phosphorus,and potassium contained in soil.Only the adoption of the strict enclosure system,implementation of aggressive artificial vegetation restoration measures and the realization of the regurgitation-feeding policy of industry towards husbandry can guarantee the gradual restoration of degraded sandy grassland in farming-pastoral ecotone,so that it can continue to play the role of ecological protective screen.

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.

Soil microbial community assemblage and its seasonal variability in alpine treeline ecotone on the eastern Qinghai-Tibet Plateau

The alpine treeline ecotone is characterized as the upper limit of the forest in the high-mountain ecosystem.Due to the freeze-thaw cycles,the soil organism community,such as microbial communities are expected to change between seasons.However,there are limited microbialcommunity studies focused on the high altitude alpine ecosystem.We conducted a study in the alpine treeline ecotone on the eastern Qinghai-Tibet Plateau,China,and investigated the seasonal variability of the soil microbial community.We collected all soil samples within the alpine treeline ecotone,between the treeline and timberline in the high-mountain region.The 16S rRNA genes of the microbial communities(bacterial and archaeal)were analyzed by highthroughput sequencing to the genus level.The results showed that soil microbial community in the alpine treeline ecotone was consistently dominated by eight phyla which consisted of 95% of the total microbial community,including Proteobacteria,Actinobacteria,Acidobacteria,Firmicutes,Planctomycetes,Chloroflexi,Bacteroidetes,and Verrucomicrobia.The overall diversity and evenness of the community were relatively stable,with an average of 0.5% difference between seasons.The highest seasonal variability occurred at the upper boundary of the alpine treeline ecotone,and few or almost no seasonal change was observed at lower elevations,indicating dense forest cover and litter deposition might have created a local microclimate that reduced seasonal variation among the surrounding environmental conditions.Our study was one of the first group that documented the microbial community assemblage in the treeline ecotone on the Qinghai-Tibet Plateau.

Dynamics of the Alpine Treeline Ecotone under Global Warming:A Review

The alpine treeline ecotone is defined as a forest-grassland or forest-tundra transition boundary either between subalpine forest and treeless grassland,or between subalpine forest and treeless tundra.The alpine treeline ecotone serves irreplaceable ecological functions and provides various ecosystem services.There are three lines associated with the alpine treeline ecotone,the tree species line(i.e.,the highest elevational limit of individual tree establishment and growth),the treeline(i.e.,the transition line between tree islands and isolated individual trees)and the timber line(i.e.,the upper boundary of the closed subalpine forest).The alpine treeline ecotone is the belt region between the tree species line and the timber line of the closed forest.The treeline is very sensitive to climate change and is often used as an indicator for the response of vegetation to global warming.However,there is currently no comprehensive review in the field of alpine treeline advance under global warming.Therefore,this review summarizes the literature and discusses the theoretical bases and challenges in the study of alpine treeline dynamics from the following four aspects:(1)Ecological functions and issues of treeline dynamics;(2)Methodology for monitoring treeline dynamics;(3)Treeline shifts in different climate zones;(4)Driving factors for treeline upward shifting.

岷江源区亚高山森林-高山草地生态系统界面土壤无机磷赋存特征及其影响因子

土壤无机磷是高寒生态系统有效磷的重要来源,研究亚高山森林-高山草地生态系统界面的土壤无机磷组分动态及其影响因素有助于深刻理解该生态系统的生物地球化学循环过程。本研究采用Tiessen修订的Hedley磷素分级法,分析了岷江源区卡卡山和斗鸡台亚高山森林-高山草地生态系统界面不同深度土壤(0-15和15-30 cm)无机磷组分的季节动态(生长初期、生长盛期、生长末期)和空间赋存特征及其主要影响因子。结果表明:1)不同形态土壤无机磷的含量受到生长期、植被类型及其交互作用的显著影响(P<0.05);斗鸡台土壤活性无机磷(NaHCO_(3)-Pi)含量在生长季初期最低;卡卡山草甸(56.0 mg·kg^(-1))、树种线(68.4 mg·kg^(-1))和密闭森林(65.7 mg·kg^(-1))土壤活性无机磷含量在生长季末期最高(P<0.05);两处生态系统界面的土壤中等活性无机磷(NaOH-Pi)含量在生长季末期均达到最高值(P<0.05)。2)密闭森林样带的土壤无机磷主要形态是活性无机磷,HCl-Pi是树种线样带土壤无机磷的主要形态,中等活性无机磷和残留无机磷(Residual-P)是草甸区土壤无机磷的主要形态。3)土壤有机碳、全氮、全磷、含水量、酸碱度以及土壤碳氮磷化学计量比与土壤无机磷组分含量显著相关(P<0.05)。研究结果表明,生长期、植被类型和土壤理化性质与无机磷组分的变化显著相关。

国内外高山林线研究综述

高山林线作为山地郁闭林和高山草甸的分界在山地生态系统中占有重要地位。以往对山地生态的研究远少于对其它类型陆地生态系统的研究，高山林线方面的研究就更为缺乏。讨论了高山林线的概念和内容，对国内外高山林线研究及特点作了简单回顾，指出高山林线的研究意义及在我国开展此项研究的初步方案。

川西高山树线群落交错带地被物及土壤的水文效应

采用样带法,以川西米亚罗林区鹧鸪山高山树线群落交错带为研究对象,分析交错带地被物和土壤的持水特性及其变化规律。结果表明:地被物最大持水量为33.55～140.03t·hm-2,暗针叶林>林线>树线>密灌丛>草甸>疏灌丛,暗针叶林枯落物最大持水量显著高于疏密灌丛和草甸;林线地被物拦蓄降水的作用最明显;暗针叶林以苔藓层和枯落物层具有最大有效拦蓄效果,林线和树线以苔藓层具有最大有效拦蓄效果,疏密灌丛以枯落物层具有最大有效拦蓄效果,高山草甸草本层、苔藓层、枯落物层有效拦蓄效果相当;0～30cm土壤饱和蓄水量都在2000t·hm-2以上,暗针叶林>林线>疏灌丛>密灌丛≈草甸>树线;各群落0～30cm土层非毛管持水量为575.89～801.46t·hm-2,表现为暗针叶林>疏灌丛>树线>密灌丛>林线>草甸。

东祁连山灌-草群落交错带土壤呼吸动态及影响因子分析

为探究高寒灌-草交错带土壤呼吸动态及影响因素,应用LI-8100A 土壤呼吸自动测定系统,对东祁连山典型灌丛-草地交错带土壤呼吸动态及土壤因子进行测定,分析呼吸速率与土壤因子的相互关系.结果表明,整个交错带内土壤呼吸速率的均值介于2.3～7.2μmol/（m2·s）,各样地间土壤呼吸速率大小顺序为珠芽蓼草甸中心（S1）〉草甸-金露梅灌丛交错区（MSC1）〉金露梅灌丛中心（S2）〉 金露梅- 杜鹃灌丛交错区（MSC2）〉 杜鹃灌丛中心（S3）,S1 和MSC1 样地的土壤呼吸日变化呈单峰型,峰值出现在14：00,S2、MSC2、S3 样地峰型不明显,且日变幅较小,仅为0.3～1.1μmol/（m2·s）;交错带内土壤物理性质和养分储量呈明显的垂直分异规律,土壤呼吸速率与土壤温度、全磷储量呈极显著的正相关（P〈0.01）,与土壤含水量极显著负相关（P〈0.01）,与0～20cm 土壤有机碳储量呈显著负相关（P〈0.05）;拟合分析显示,土壤温度、含水量和全磷储量是土壤呼吸速率的主要限制因子,土壤呼吸与土壤温度拟合系数最高,可解释土壤呼吸空间变异的79.9%.

高山树线交错带及其对全球气候变化的响应研究进展

高山树线交错带(Alpine treeline ecotone,ATE),处于高寒严酷气候胁迫的临界状态,是高海拔生态系统承受环境变化压力最大的地带之一,全球性和区域性气候变暖必然在这一生态界面上有所反映。已有的研究表明,高山树线交错带对气候变化的响应方式及强度,因地形、ATE类型和物种组成以及研究方法和尺度而异。在气候变化的背景下,关于ATE的动态对高海拔生态系统土壤生物地化过程及碳循环的影响的相关研究还比较缺乏,而土壤生物过程对环境因子的敏感度远高于植物群落演替对环境变化的响应。因此,今后的研究应该结合各学科的最新研究手段,在不同尺度上开展对ATE的生态和土壤过程与机理方面的定量研究。

高寒农牧交错带植被恢复对土壤有机碳、全氮含量的影响

以耕地为对照,研究了高寒农牧交错带种植老芒麦草和撂荒2种植被恢复措施对土壤有机碳和全氮含量的影响.结果表明,与耕地相比较种植老芒麦草和撂荒使0-30 cm土层土壤总有机碳含量分别增加了19.7%-22.4%和7.3%-10.6%,颗粒有机碳(0.05-2.00 mm)含量分别增加了43.0%-52.3%和28.7%-59.8%,土壤全氮含量分别增加了12.0%-20.6%和5.4%-13.7%.这一结果说明,在高寒农牧交错带通过种植老芒麦草或者撂荒植被恢复措施,对于提高土壤有机质含量和全氮含量、恢复土壤质量具有非常显著的效果.

高寒农牧交错区退耕还林政策实施效应评价

高寒农牧交错区的生态经济系统十分脆弱。退耕还林政策的实施有力地促进了地区生态环境的改善,并对当地社会经济的可持续发展产生深远影响。以青海省湟中县为例,通过入户问卷调查和退耕地样方调查,有针对性、具体地评价退耕还林生态、经济、社会效益,并结合研究区现存问题,提出了相应对策和建议。

高寒农牧交错区退耕还林政策实施效应评价

高寒农牧交错区的生态经济系统十分脆弱。退耕还林政策的实施有力地促进了地区生态环境的改善,并对当地社会经济的可持续发展产生深远影响。以青海省湟中县为例,通过入户问卷调查和退耕地样方调查,有针对性、具体地评价退耕还林生态、经济、社会效益,并结合研究区现存问题,提出了相应对策和建议。

高寒农牧交错区生态重建与经济发展互动模型及应用研究

以高寒农牧交错区为研究对象,运用灰色关联法,建立了高寒农牧交错区生态重建与经济发展的互动模型。模型结果表明:(1)生态重建与地区经济发展之间存在极强的关联性,二者互为驱动,相互促进,交互耦合构成生态经济系统;(2)在生态与经济互动中,经济系统的影响占优,表明经济贫困是生态重建的最大限制因素;(3)农户作为生态重建和经济发展的行为决策者是生态经济互动链的节点。在此基础上,结合样点村实际,选择林药结合的退耕模式、移民搬迁、建设小城镇和发展反季节蔬菜基地等作为实现研究区经济与生态协调发展的具体模式与有效途径。

川西高山林线三种灌木凋落叶分解中的无脊椎动物多样性

以无脊椎动物为主体的土壤动物是影响凋落物分解的重要生物因素,对维持陆地生态系统物质循环和能量流动具有重要作用。高山林线交错带是高山植被垂直带谱中重要的过渡区域,拥有比相邻生态系统更高的生境复杂性和物种多样性。林线上温度波动和冻融循环频率显著高于针叶林,为了了解林线交错带上环境差异对凋落物分解过程中的土壤动物群落结构和多样性的影响,采用凋落物分解袋的方法,于高山生态系统的两个主要时期,即雪被末期和生长季末期,研究了林线主要代表性灌木——高山柳(Salix cupularis)、高山杜鹃(Rhododendron lapponicum)和红毛花楸(Sorbus rufopilosa)凋落叶分解的土壤动物多样性特征。结果表明:凋落物中的无脊椎动物群落多样性及个体、类群密度随物种、海拔梯度和季节而变化,且季节差异对无脊椎动物多样性的影响比物种和海拔梯度更显著。3个因子的交互作用不仅影响土壤动物群落多样性和均匀度,而且影响群落个体密度和类群密度。雪被末期,凋落物中的无脊椎动物多样性指数H、均匀度指数J及丰富度指数D以针叶林最高,优势度指数C以林线最高;生长季节末期的无脊椎动物类群密度和个体密度显著高于雪被末期。总体上,凋落物中的无脊椎动物群落丰富度以生长季末期最高,林线较针叶林丰富。这意味着,未来气候变暖情景下,灌丛密度增加,凋落物输入量增大,可能导致无脊椎动物多样性增加。

岷江源区典型高山林草交错带土壤养分的空间变化特征及影响因素

高山林草交错带是响应全球气候变化的敏感区。林草交错带植被类型和植物群落特征受气候变化和土壤养分状况的共同影响。然而,这一敏感生态带内主要土壤养分状况及海拔梯度特征仍不清楚。本研究于2019年6月上旬,对岷江源区两处高山林草交错带按不同植被带(草甸区−高寒草甸、树种线−亚高山灌丛带、树线−乔灌带、密闭森林−暗针叶林)分别在0−10和10−20 cm土层取土样,测定土壤有机碳、总氮、总磷、pH和土壤水分含量,分析土壤碳、氮、磷和水分含量的空间分布特征及其影响因素。研究发现,植被类型是影响岷江源高山林草交错带土壤理化性质的主要因子;草甸区土壤全碳(total carbon,TC)、全氮(total nitrogen,TN)、有机碳(soil organic carbon,SOC)含量显著低于其他植被带(P<0.05),树种线、树线、密闭森林处土壤TC、TN、SOC含量无显著差异(P>0.05);树线处土壤总磷(total phoshorus,TP)含量显著低于其他植被带(P<0.05);土壤全碳、全氮、有机碳土壤含水量(soil variable water content)间有极显著相关关系(P<0.01),在树种线处土壤各理化性质间相关性最弱;树线处土壤化学计量比较大,且该植被类型带土壤C∶P、N∶P的空间异质性很强。结果表明,虽然岷江源高山林草交错带树种线、树线、密闭森林处的C、N、P含量无显著差异(P>0.05),但树种线和树线处植被对土壤养分间的相互作用影响显著(P<0.05)。

藏东南色季拉山林线植物非结构性碳水化合物的季节变动

【目的】研究高山林线植物非结构性碳水化合物(NSC)含量的变化,以更好地揭示高山林线的形成机制。【方法】以藏东南色季拉山林线过渡带的5种木本植物(阳坡:乔木方枝柏,灌木林芝杜鹃和雪层杜鹃;阴坡:乔木急尖长苞冷杉,灌木雪山杜鹃)为研究对象,在生长季(8月初)与非生长季(11月底)分别取其树叶、树枝、树干(方枝柏和急尖长苞冷杉)、树根等组织,测定并分析其NSC含量。【结果】林线过渡带植物在整个生长周期都有充足的NSC,生长季植物NSC含量在2.74%~3.56%,非生长季NCS含量是生长季的2.85~3.84倍。生长季5种林线过渡带植物的NSC源/汇值为1.12~1.79;非生长季2种乔木NSC含量的NSC源/汇值均大于1,表明植物碳供应充足;3种灌木植物的NSC源/汇值均小于1,表现为碳供应不足。低温等不良环境是导致非生长季植物可溶性糖与淀粉比值较生长季明显升高的主要因素;非生长季林线过渡带植物可溶性糖含量是生长季的2.64~7.66倍,而高水平的可溶性糖含量和可溶性糖与淀粉间持续的动态转化都是植物顺利过冬的保障。【结论】构成色季拉山林线的方枝柏和急尖长苞冷杉在生长季与非生长季均未表现出碳供应不足的现象,“生长抑制”和“更新繁殖障碍限制”两种假说能很好地解释藏东南色季拉山林线的形成机制。