巴音布鲁克地区植物物候时空动态变化及其驱动分析

植物物候是反映气候变化最显著、直观的指标,对理解气候变化与植物物候的相互作用具有重要的意义。而不同的生态系统对气候变化的响应和反馈存在差异,科学分析气候变化趋势下多种生态系统植物物候变化特征及其驱动因子对理解植物物候变化机制具有重要意义。本文选取多种生态系统交错分布的巴音布鲁克为研究区域,基于MODIS NDVI时间序列,得到了研究区物候的空间格局特征、时空变化特征以及与海拔和气候因子之间的关系。结果表明:(1)研究区植被返青期主要于4月上旬至5月下旬,枯黄期主要于9月中旬至10月中旬;(2) 2001—2017年,研究区植物返青期总体上呈提前趋势,其中草原、草甸和沼泽提前显著。枯黄期在北部呈提前趋势,在南部呈推迟趋势,其中高山植被和草原枯黄期提前显著;(3)植被的返青期总体上随着海拔的升高而推迟,枯黄期总体上随着海拔的升高而提前,各生态系统植被间的物候期差异随着海拔的升高而缩短。(4)研究区植物返青期与春季气温呈显著负相关,其中高山植被受5月气温影响较大,草原和沼泽受4月气温影响较大,草甸受4月和5月气温影响较大。     

高寒草甸植被耗水量及生物量积累与气象因子的关系

分析高寒草甸植被生育期耗水量及植被生物量积累与气象因子的关系,结果表明植被生育期耗水量呈单峰型变化过程,7月耗水量最大。初期营养生长阶段的5月耗水量、植被生物量均较低,水分影响着植物的初期营养生长但不甚显著;植物旺盛生长的6～7月,耗水量高,而生物量波动明显,温度和水分均影响到生物量的提高,且水分是影响植被生长的关键因素;植物生长末期的8～9月,耗水量及植被阶段累积生物量均较低,水分条件充足,并非是植物生长的限制因素。海北高寒草甸地区植被年地上净初级生产量、地下净初级生产量、净初级生产量与植被耗水量关系不明显。而与相应的温度具有较显著的正相关关系。表明高寒草甸地区植被净初级生产量受温度条件限制的影响比水分条件更为明显。     

模拟增温对青海湖鸟岛高寒草原群落结构影响初步研究

采用国际冻原计划(ITEX)开顶箱(OTC)模拟增温实验方法,研究了青海湖鸟岛高寒草原群落结构、典型物种生长特征、地上生物量及繁殖分配对温度升高的响应。模拟增温使生长季20 cm土壤温度白天平均增温1.08℃;夜晚平均增温0.55℃。短期模拟增温没有影响到群落的物种组成,但改变了物种的重要值。增温使得原有群落逐步演替为以禾本科假苇拂子茅为主的群落,使群落趋于单一化发展。增温显著地增加了该区域主要禾本科植物的地上生物量和其有性繁殖株个体的高度以及穗子的长度,同时也增加了有性繁殖植株的比例。这说明由于小气候作用,环境条件诱发导致的土壤温度的改变,会使得植被的种群结构、典型物种生长特征、地上生物量及繁殖分配发生改变。     

近12a三江源地区植被物候对水热的响应

基于1999—2010年SPOT VEGETATION旬值NDVI数据,结合谐波分析法与偏相关分析等方法,对三江源地区年植被物候特征值进行了确定,并分析了年际物候对不同时段水热变化的响应。结果表明:1三江源地区响应时段累积降水量和气温的增加都会使植物生长季始期推迟。2三江源地区植物生长季末期与累积降水和气温的最值偏相关系数分别为0.180 6和-0.067 8,说明响应时段累积降水量的增加会使植物生长季末期推迟,而累积气温的升高会使植物生长季末期提前,但累积气温影响相对较小。而响应时段累积降水量的增加,会使植物生长季长度延长;累积气温的升高,会使植物生长季长度缩短。3三江源地区植物生长季长度的年际变化,受生长季末期的影响较大。4三江源地区植物生长季始期主要受前一年累积气候要素影响强烈;生长季末期主要受生长季内累积降水影响强烈。生长季长度受生长季之前的累积气温的作用强烈。     

短期增温下青藏高原多年冻土区植物生长季土壤水分的动态变化

以青藏高原腹地典型高寒草甸植被类型为研究对象,采用红外灯加热的方法模拟全球增温,并利用水分探头,于2012年植物生长季（5—9月）获取0~100 cm不同土层深度土壤水分含量数据,并分析其对增温的响应。结果表明：① 短期增温对高寒草甸土壤水分含量有提高作用,但增幅并不显著（P>0.05）,平均提高2.85%。② 土壤水分含量随土层深度的增加呈现先减少后增加的趋势,在10~20 cm土层深度处降为最低值13.8%,在60~100 cm土层深度附近达到了20.57%的最高值;对照组5个月10~20 cm土层深度的土壤水分含量显著低于其他土层,而增温组0~20 cm土层深度的土壤含水量显著低于其他土层深度,表明增温对表层（0~10 cm）的土壤含水量影响较大,对深层土壤含水量的影响则较小,而且短期增温不会对土壤水分的垂直分布趋势产生影响。③ 土壤水分含量随时间的变化,在5—8月呈上升趋势,表明在青藏高原北麓河地区植物生长季,8月是其土壤水分含量最充足的月份,到了9月土壤中含水量开始降低,但5个土层深度降幅均不明显;增温组土壤水分含量随时间的变化趋势与对照组基本一致。     

气候变暖背景下近30a北半球植被变化研究综述

归一化植被指数(NDVI)目前广泛应用于全球和区域尺度植被变化研究,成为揭示气候变化的重要指标。基于NDVI变化以及NDVI提取的植被物候变化2个方面(植被生长季开始时间SOG,植被生长季结束时间EOG),对近30 a气候变暖背景下北半球植被变化的有关研究结论进行回顾总结。结果显示:1近30 a北半球植被生长季NDVI整体呈增加趋势,森林植被NDVI增长速率大于其他植被类型;20世纪90年代NDVI增加趋势较80年代显著,从21世纪初开始,出现NDVI增长速率减缓现象;2近30 a北半球SOG整体呈提前趋势,近10 a SOG提前趋势减缓;欧亚地区SOG提前趋势可能较北美显著,非洲植被物候变化规律不清晰;北半球植被物候变化表现出明显的纬度地带性,55°~65°N纬度带SOG提前趋势与45°~55°N纬度带EOG推迟趋势相对显著;3除森林退化严重外,近30 a青藏高原植被整体上以增加为主,NDVI增长趋势北部显著,中部和东部微弱,南部呈下降趋势;高原东部和藏北SOG提前趋势显著,而中部、西部和西南部有推迟现象。     

高寒湿地生态系统水分利用效率研究

高寒湿地生态系统水分利用效率的研究,有助于明晰高寒地区碳水耦合程度和优化水资源管理。基于涡度相关系统,研究分析了2015年和2016年生长季青海湖高寒湿地生态系统水分利用效率的变化特征和主要环境因子对其的影响。结果表明:生态系统各月水分利用效率日变化都呈先减小后增大的趋势,且生长季中期大于前期和后期的水分利用效率。生态系统水分利用效率季节变化呈生长季中期高,初期和后期低。2015年和2016年总体水分利用效率分别为5.42 g·kg~(-1)和4.65 g·kg~(-1)。与环境因子的分析表明,生态系统水分利用效率与温度、叶面积指数、月降水量和土壤体积含水量相关性显著,而与光合有效辐射和饱和水汽压差的相关性较差。     

基于CVOR指数的巴音布鲁克高寒草原健康评价

利用草地生态系统健康评价CVOR综合指数,对巴音布鲁克高寒草原生态系统2004—2012年健康状态进行评价与退化分级研究,并对引起CVOR变化的内在驱动力因素进行探讨。结果表明:(1)研究区高寒草原生态系统健康状况由一般病态(2004年CVOR=0.58)逐渐恢复为健康状态(2012年CVOR=0.72);退化状况由强度退化恢复为中度退化,但局部仍存在强度退化;(2)降水是高寒草原生态系统CVOR指数的主要限制因子,降水也是除基况外各分指数变化的重要驱动因素;在气候变化背景下,CVOR指数将上升;(3)放牧改变了围栏外的群落功能组分,围封可以改善高寒草原生态系统的健康状况,有利于植被的正向演替,过度放牧是影响高寒草原恢复和演替的重要因素。总体上,降水和放牧是影响研究区高寒草原健康状况的主要原因。     

短花针茅荒漠草原土壤呼吸对长期增温和氮素添加的响应

作为全球变化的主要成分,温度升高和氮沉降量增多会对土壤呼吸产生深远影响。本研究基于长期增温和氮素添加野外控制试验(2006年开始处理),利用Li-8100开路式碳通量测定系统测定2016年生长季(5～10月)土壤呼吸速率,研究土壤呼吸速率对内蒙古短花针茅荒漠草原增温和氮素添加的响应,研究结果表明:1)氮素添加显著降低了土壤呼吸速率3. 2%(P <0. 05),增温对其没有显著影响(P=0. 59),但是氮素添加与增温共同作用对土壤呼吸速率的影响显著(P <0. 05),在增温条件下,氮素添加使土壤呼吸速率减弱;2)土壤呼吸速率与土壤湿度呈显著正相关关系(P <0. 0001); 3)土壤呼吸速率对温度的敏感性(Q10值)在增温处理下降低,但是在氮素添加以及氮素添加和增温共同处理下增强。上述结果表明在水分限制的荒漠草原生态系统,氮素添加和增温对土壤呼吸的影响受到水分条件的调控。     

青海气候变化趋势及对植被生产力影响的研究

应用青海省南部三江源区、东北祁连山地及环青海湖区气象站1961-2004年气温、降水和所在地区植被地上净初级生产力资料,分析和模拟了44年来有关气候变化特征以及植被生产力与气温、降水、地理坐标参数间的关系,模拟估算了假设未来气候温暖化情景下青海植被生产力变化的可能。结果表明:44年来青海各地气温均在升高,青海北部比南部增温明显;年降水量变化平稳,但北部比南部有所增加;土壤实际蒸发散表现出明显的升高趋势;青海南部植被地上净初级生产力(NPP)逐年降低,青海东北地区相对平稳。模拟计算表明,由于青藏高原植被的生长主要受温度条件的限制,在未来气候增暖,降水不变或增加的趋势下,植被地上NPP均有所增加。     

Effects of long-term warming on the aboveground biomass and species diversity in an alpine meadow on the Qinghai-Tibetan Plateau of China

Ecosystems in high-altitude regions are more sensitive and respond more rapidly than other ecosystems to global climate warming.The Qinghai-Tibet Plateau(QTP)of China is an ecologically fragile zone that is sensitive to global climate warming.It is of great importance to study the changes in aboveground biomass and species diversity of alpine meadows on the QTP under predicted future climate warming.In this study,we selected an alpine meadow on the QTP as the study object and used infrared radiators as the warming device for a simulation experiment over eight years(2011-2018).We then analyzed the dynamic changes in aboveground biomass and species diversity of the alpine meadow at different time scales,including an early stage of warming(2011-2013)and a late stage of warming(2016-2018),in order to explore the response of alpine meadows to short-term(three years)and long-term warming(eight years).The results showed that the short-term warming increased air temperature by 0.31℃and decreased relative humidity by 2.54%,resulting in the air being warmer and drier.The long-term warming increased air temperature and relative humidity by 0.19℃and 1.47%,respectively,and the air tended to be warmer and wetter.The short-term warming increased soil temperature by 2.44℃and decreased soil moisture by 12.47%,whereas the long-term warming increased soil temperature by 1.76℃and decreased soil moisture by 9.90%.This caused the shallow soil layer to become warmer and drier under both short-term and long-term warming.Furthermore,the degree of soil drought was alleviated with increased warming duration.Under the long-term warming,the importance value and aboveground biomass of plants in different families changed.The importance values of grasses and sedges decreased by 47.56%and 3.67%,respectively,while the importance value of weeds increased by 1.37%.Aboveground biomass of grasses decreased by 36.55%,while those of sedges and weeds increased by 8.09%and 15.24%,respectively.The increase in temperature had a non-significant effect on species diversity.The species diversity indices increased at the early stage of warming and decreased at the late stage of warming,but none of them reached significant levels(P>0.05).Species diversity had no significant correlation with soil temperature and soil moisture under both short-term and long-term warming.Soil temperature and aboveground biomass were positively correlated in the control plots(P=0.014),but negatively correlated under the long-term warming(P=0.013).Therefore,eight years of warming aggravated drought in the shallow soil layer,which is beneficial for the growth of weeds but not for the growth of grasses.Warming changed the structure of alpine meadow communities and had a certain impact on the community species diversity.Our studies have great significance for the protection and effective utilization of alpine vegetation,as well as for the prevention of grassland degradation or desertification in high-altitude regions.     

Effects of warming and clipping on plant and soil properties of an alpine meadow in the Qinghai-Tibetan Plateau,China

Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau(QTP) in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010–2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in October 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments: control(CK), warming(W), clipping(C) and warming+clipping combination(WC). The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0–30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0–60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0–30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40–100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30–50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the downward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen. However, long-term data collection is needed to further explain this interesting phenomenon.     

Differences in response of desert plants of different ecotypes to climate warming:a case study in Minqin, Northwest China

Globally climates are warming.How do desert plants of different ecotypes respond to the climate change?This paper studied the differing responses to climate warming shown by desert plants of different ecotypes through analyzing the phenology and meteorological data of 22 desert plant species growing in Minqin Desert Botanical Garden in Northwest China during the period 1974–2009.The results indicate:(1)The temperature in the study area has risen quickly since 1974,and plants’growing periods became longer.The spring phenology of mesophytes advanced,and the autumn phenology of xerophytes was delayed;(2)The starting dates of spring phenophase of mesophytes and xerophytes differed significantly and both showed an advancing trend;(3)The spring phenology of mesophytes advanced by more days than that of xerophytes,whereas the autumn phenology of mesophytes was delayed by less days than that of the xerophytes;and(4)Mesophytes are more sensitive than xerophytes to rising temperature in spring and falling temperature in autumn.These findings are of value in plant management and regional introduction of different species.     

Warming effects on plant biomass allocation and correlations with the soil environment in an alpine meadow,China

Alpine meadow ecosystem is fragile and highly sensitive to climate change.An understanding of the allocation of above-and below-ground plant biomass and correlations with environmental factors in alpine meadow ecosystem can result in better protection and effective utilization of alpine meadow vegetation.We chose an alpine meadow in the Qinghai-Tibetan Plateau of China as the study area and designed experimental warming plots using a randomized block experimental design.We used single-tube infrared radiators as warming devices,established the warming treatments,and measured plant above- (AGB) and below-ground biomass (BGB) during the growing seasons (May to September) in 2012 and 2013.We determined the allocation of biomass and the relationship between biomass and soil environment under the warming treatment.Biomass indices including above-ground biomass,below-ground biomass and the ratio of root to shoot (R/S) ,and soil factors including soil moisture and soil temperature at different depths were measured.The results showed that (1) BGB of the alpine meadow had the most significant allometric correlation with its AGB (y=298.7x~ (0.44) ,P0.001) ,but the relationship decreased under warming treatment and the determination coefficient of the functional equation was 0.102 which was less than that of 0.188 of the unwarming treatment (control) ; (2) BGB increased,especially in the deeper soil layers under warming treatment (P0.05) .At 0–10 cm soil depth,the percentages of BGB under warming treatment were smaller than those of the control treatment with the decreases being 8.52% and 8.23% in 2012 and 2013,respectively.However,the BGB increased 2.13% and 2.06% in 2012 and 2013,respectively,at 10–50 cm soil depths; (3) BGB had significant positive correlations with soil moisture at 100 cm depth and with soil temperature at 20–100 cm depths (P0.05) ,but the mean correlation coefficient of soil temperature was 0.354,greater than the 0.245 of soil moisture.R/S ratio had a significant negative correlation with soil temperature at 20 cm depth (P0.05) .The warmer soil temperatures in shallow layers increased the biomass allocation to above-ground plant parts,which leading to the increase in AGB;whereas the enhanced thawing of frozen soil in deep layers causing by warming treatment produced more moisture that affected plant biomass allocation.     

Effects of freezing intensity on soil solution nitrogen and microbial biomass nitrogen in an alpine grassland ecosystem on the Tibetan Plateau,China

The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention.In this study,the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments.The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River.In the experiment,the soil samples were cultivated at –10°C,–7°C,–5°C,–3°C and –1°C,respectively for three days and then thawed at 2°C for one day.The results showed that after the freeze-thaw process,the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased.When the freezing temperature was below –7°C,there was no significant difference between the content of nitrogen components,which implied a change of each nitrogen component might have a response threshold toward the freezing temperature.As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem,more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.     

气候变暖对农业害虫及其天敌的影响

全球气候的持续变暖引起了人类的高度关注。农业害虫是关系到农业生产顺利进行的一个特殊的昆虫类群,已经受到温度升高的影响。本文从气候变暖对农业害虫的发生、为害以及与天敌间关系的影响等三方面进行了综述。温度升高导致农业害虫的发生区域扩张,发生期提前和延长,高温适生种群发生量增大;农业害虫的为害时期改变,为害程度加重,为害物种之间产生新的竞争关系;农业害虫与寄主植物、天敌之间的同步性发生改变,继而影响到农业害虫的生物防治。本文最后对当前的研究工作进行了评述,就气候变暖形势下农业害虫的防治提出建议。     

全球气候变暖对京津冀地区极端天气气候事件的影响及防灾减灾对策

在综合分析全球气候变暖对极端天气气候事件影响的基础上,详细分析了京津冀地区气候变化对全球气候变暖的响应。研究表明：近百年来该区气温与全球气候变暖呈明显的正响应,而降水则表现为明显的负响应。全球气候变暖对该区极端天气气候事件的可能影响主要表现为：气温上升明显,高温热害天气增多;物候季节提前或反常、极端气候灾害频发;极端降...     

气候变暖对典型草原区降水时空分布格局的影响

立足于全球变暖对内蒙古典型草原区降水时空变化影响的研究,预测全球变化可能带来的后果,为良性的生态系统服务提供理论依据。基于1971-2000年锡林浩特市和阿巴嘎旗两个气象台站的平均温度和锡林郭勒盟境内16个气象站点的降水资料,结合地理信息系统技术,系统分析了气候变暖对典型草原区降水时空分布格局的影响。初步研究结果表明:气温变化过程和全球变暖的趋势相一致,特别是20世纪90年代气温上升变暖趋势最为强烈。在全球气候变暖的背景下,研究区的降雨量受东南季风的影响呈现由东南向西北递减的分布规律。但区域降雨存在明显的年代际变化特征,各区域降水变化差异显著,从东南到西北变化的幅度减小。30年来研究区的降雨量变化表现出时间、空间上的不规则性,表明全球气候变化对草原区过去30年的降雨影响不显著,没有达到可识别的程度。     

Dependency of litter decomposition on litter quality,climate change,and grassland type in the alpine grassland of Tianshan Mountains,Northwest China

Litter decomposition is an important component of the nutrient recycling process and is highly sensitive to climate change. However, the impacts of warming and increased precipitation on litter decomposition have not been well studied, especially in the alpine grassland of Tianshan Mountains. We conducted a manipulative warming and increased precipitation experiment combined with different grassland types to examine the impact of litter quality and climate change on the litter decomposition rate based on three dominant species (Astragalus mongholicus, Potentilla anserina, and Festuca ovina) in Tianshan Mountains from 2019 to 2021. The results of this study indicated there were significant differences in litter quality, specific leaf area, and leaf dry matter content. In addition, litter quality exerted significant effects on litter decomposition, and the litter decomposition rate varied in different grassland types. Increased precipitation significantly accelerated the litter decomposition of P. anserina; however, it had no significant effect on the litter decomposition of A. mongholicus and F. ovina. However, warming consistently decreased the litter decomposition rate, with the strongest impact on the litter decomposition of F. ovina. There was a significant interaction between increased precipitation and litter type, but there was no significant interaction between warming and litter type. These results indicated that warming and increased precipitation significantly influenced litter decomposition; however, the strength was dependent on litter quality. In addition, soil water content played a crucial role in regulating litter decomposition in different grassland types. Moreover, we found that the litter decomposition rate exhibited a hump-shaped or linear response to the increase of soil water content. Our study emphasizes that ongoing climate change significantly altered litter decomposition in the alpine grassland, which is of great significance for understanding the nutrient supply and turnover of litter.     

Spatiotemporal characteristics and influencing factors of ecosystem services in Central Asia

Land use/land cover (LULC) change and climate change are two major factors affecting the provision of ecosystem services which are closely related to human well-being. However, a clear understanding of the relationships between these two factors and ecosystem services in Central Asia is still lacking. This study aimed to comprehensively assess ecosystem services in Central Asia and analyze how they are impacted by changes in LULC and climate. The spatiotemporal patterns of three ecosystem services during the period of 2000-2015, namely the net primary productivity (NPP), water yield, and soil retention, were quantified and mapped by the Carnegie-Ames-Stanford Approach (CASA) model, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, and Revised Universal Soil Loss Equation (RUSLE). Scenarios were used to determine the relative importance and combined effect of LULC change and climate change on ecosystem services. Then, the relationships between climate factors (precipitation and temperature) and ecosystem services, as well as between LULC change and ecosystem services, were further discussed. The results showed that the high values of ecosystem services appeared in the southeast of Central Asia. Among the six biomes (alpine forest region (AFR), alpine meadow region (AMR), typical steppe region (TSR), desert steppe region (DSR), desert region (DR), and lake region (LR)), the values of ecosystem services followed the order of AFR>AMR>TSR>DSR> DR>LR. In addition, the values of ecosystem services fluctuated during the period of 2000-2015, with the most significant decreases observed in the southeast mountainous area and northwest of Central Asia. LULC change had a greater impact on the NPP, while climate change had a stronger influence on the water yield and soil retention. The combined LULC change and climate change exhibited a significant synergistic effect on ecosystem services in most of Central Asia. Moreover, ecosystem services were more strongly and positively correlated with precipitation than with temperature. The greening of desert areas and forest land expansion could improve ecosystem services, but unreasonable development of cropland and urbanization have had an adverse impact on ecosystem services. According to the results, ecological stability in Central Asia can be achieved through the natural vegetation protection, reasonable urbanization, and ecological agriculture development.