Temporal and spatial responses of ecological resilience to climate change and human activities in the economic belt on the northern slope of the Tianshan Mountains, China

In the Anthropocene era,human activities have become increasingly complex and diversified.The natural ecosystems need higher ecological resilience to ensure regional sustainable development due to rapid urbanization and industrialization as well as other intensified human activities,especially in arid and semi-arid areas.In the study,we chose the economic belt on the northern slope of the Tianshan Mountains(EBNSTM)in Xinjiang Uygur Autonomous Region of China as a case study.By collecting geographic data and statistical data from 2010 and 2020,we constructed an ecological resilience assessment model based on the ecosystem habitat quality(EHQ),ecosystem landscape stability(ELS),and ecosystem service value(ESV).Further,we analyzed the temporal and spatial variation characteristics of ecological resilience in the EBNSTM from 2010 to 2020 by spatial autocorrelation analysis,and explored its responses to climate change and human activities using the geographically weighted regression(GWR)model.The results showed that the ecological resilience of the EBNSTM was at a low level and increased from 0.2732 to 0.2773 during 2010–2020.The spatial autocorrelation analysis of ecological resilience exhibited a spatial heterogeneity characteristic of"high in the western region and low in the eastern region",and the spatial clustering trend was enhanced during the study period.Desert,Gobi and rapidly urbanized areas showed low level of ecological resilience,and oasis and mountain areas exhibited high level of ecological resilience.Climate factors had an important impact on ecological resilience.Specifically,average annual temperature and annual precipitation were the key climate factors that improved ecological resilience,while average annual evapotranspiration was the main factor that blocked ecological resilience.Among the human activity factors,the distance from the main road showed a negative correlation with ecological resilience.Both night light index and PM2.5 concentration were negatively correlated with ecological resilience in the areas with better ecological conditions,whereas in the areas with poorer ecological conditions,the correlations were positive.The research findings could provide a scientific reference for protecting the ecological environment and promoting the harmony and stability of the human-land relationship in arid and semi-arid areas.

Evolution of economic linkage network of the cities and counties on the northern slope of the Tianshan Mountains,China

The exchanges between cities and counties in the northern slope economic belt of Tianshan Mountains(NSEBTM)are increasingly frequent and the economic linkages are increasingly close,but the spatial distribution of economic development and linkages among the cities and counties within NSEBTM is uneven.Therefore,it is of great significance to study the evolution of spatial-temporal pattern of the economic linkage network of cities and counties on NSEBTM to promote the coordinated and integrated development of the regional economy on NSEBTM.In this study,we used the modified gravity model and social network analysis method to analyze the spatio-temporal evolution characteristics of the economic linkage network structure of cities and counties on NSEBTM in 2000,2010,and 2020.The results showed that the comprehensive development quality level of cities and counties on NSEBTM increased from 2000 to 2020,its growth rate also increased,and its gap between cities and counties continued expanding.Both the spatial distribution patterns of the comprehensive development quality level of cities and counties on NSEBTM in 2000 and 2010 were presented as“high in the middle and low at both ends”,while the spatial distribution pattern of 2020 was exhibited as“high value and low value staggered”.The total amount of external economic linkages of cities and counties on NSEBTM showed an obvious upward trend,and its gap between cities and counties continued expanding,presenting a pattern of“a strong middle section and weak ends”.The direction of economic linkages of NSEBTM existed obvious central orientation and geographical proximity.The density of economic linkage network of NSEBTM increased from 2000 to 2020,and the structure of economic linkage network changed from single-core structure centered with Urumqi City to multicore structure centered with Urumqi City,Karamay City,Shihezi City,and Changji City,shifting from unbalanced development to balanced development.In the future,we should accelerate the construction of urban agglomeration on NSEBTM,cultivate a modern Urumqi metropolitan area,improve comprehensive development quality of the cities and counties at the eastern and western ends,strengthen the intensity of economic linkages between cities and counties,optimize the economic linkage network,and promote the coordinated and integrated development of regional economy.

Regional Structure and Spatial Morphology Characteristics of Oasis Urban Agglomeration in Arid Area——A Case of Urban Agglomeration in Northern Slope of Tianshan Mountains,Northwest China

It is great important to the health development of urban agglomeration to correctly understand the formation and development law of regional structure of urban agglomeration.Employing the analysis methods like fractal theory and quantitative statistics,coupling with the use of remote sensing images and other spatial data,this article discusses the urban agglomeration of oasis on the northern slope of the Tianshan Mountains in an arid area,and conducts the researches on its city scale,spatial distribution and individual form from 1990 to 2005.The result shows that it has loose hierarchical scale structure and polarization trend of population distribution while its hierarchical scale structure tends to mature.Under the influence of natural conditions,the spatial layout of urban agglomeration of oasis has macro characteristics that suggest cities distributed along oasis edges(dense or sparse),spatially expand along rivers,and cluster around traffic branches.The connectivity among the cities is high and shows an internal organization form of a banding distribution.The whole spatial shape of the internal structure of cities presents a "dumbbell" form,with mononuclear phenomenon receding and multi-nuclear appearing gradually.Individual cities spatially expand along rivers,portraying a long strip appearance.It indicates that the urban agglomeration of oasis shows regular and close structure but with a tendency to be complicated form and the loose structure.In the development of urban agglomeration,the authors recommend that the development of the city with good economic development conditions should be strengthened,and more attention be put into regional planning.

Sustainable land-use patterns for arid lands: A case study in the northern slope areas of the Tianshan Mountains

Sustainable land use patterns are ecological and economic prerequisites of regional sustainable development. This is especially true for arid lands, where the environment is wholly fragile thanks to extremely limited precipitation, and where human activities have greatly transformed natural desert system by clearing natural vegetation, expanding oases and even building dams on inland rivers. However, the current studies on land use patterns are still characterized by field investigations and case studies, with almost no solid scientific basis. This paper holds that land types and their combination patterns are the principal basis for designing sustainable land use patterns, and that GIS and RS-based large-scale land type mapping and the study of their spatial combination structures should be coordinated with the demand of social development. The existing environmental problems induced by irrational land use mostly result from their deviation from the natural properties of land types. Taking the northern slope of the Tianshan Mountains （NSTM） as an example and considering land type patterns as the basis of land use patterns, this paper improves the vertical oa- sis-and-mid-mountain two-belts development model and the sustainable mountain land use model for arid lands put forward in recent years; and in terms of oases patterns, it outlines oasis development models, including intensive land use pattern in alluvial-diluvial fans, moderate agricultural development pattern in alluvial plains, and ecological land use pattern in river-end oases.

An analysis of oasis stability in arid areas:a case study in the northern slope areas of the Tianshan Mountains

This paper discusses oasis stability at regional scale with a case study in the northern slope areas of the Tianshan Mountains (NSTM). The results showed certain significant aspects. (1) As long as water resources in the oasis keep stable and their utilization efficiency can be maintained or gradually increased, the primary productivity could be continuously increased and the natural primary productivity keeped relatively stable. In this case, it is considered that the oasis is stable and its sustainable development can be achieved at regional scale. (2) Considering the availability of water resources in the oases, the oases on the alluvial-diluvial fans are highly stable. In the alluvial plain downstream of the groundwater overflowing zones the oases are moderately stable and in the lacustrine deltas or dry lacustrine deltas the oases are lowly stable. (3) Enlargement of oases and the increase of water resources and vegetation coverage in the oasis will certainly enhance the 'cold-island effect' of the oasis and increase the stability of oases.

Response of ecosystem service value to land use/cover change in the northern slope economic belt of the Tianshan Mountains, Xinjiang, China

Land use/cover change(LUCC)is becoming more and more frequent and extensive as a result of human activities,and is expected to have a major impact on human welfare by altering ecosystem service value(ESV).In this study,we utilized remote sensing images and statistical data to explore the spatial-temporal changes of land use/cover types and ESV in the northern slope economic belt of the Tianshan Mountains in Xinjiang Uygur Autonomous Region,China from 1975 to 2018.During the study period,LUCC in the study region varied significantly.Except grassland and unused land,all the other land use/cover types(cultivated land,forestland,waterbody,and construction land)increased in areas.From 1975 to 2018,the spatial-temporal variations in ESV were also pronounced.The total ESV decreased by 4.00×10^(8) CNY,which was primarily due to the reductions in the areas of grassland and unused land.Waterbody had a much higher ESV than the other land use/cover types.Ultimately,understanding the impact of LUCC on ESV and the interactions among ESV of different land use/cover types will help improve existing land use policies and provide scientific basis for developing new conservation strategies for ecologically fragile areas.

Spatiotemporal characteristics of the expansion of an urban agglomeration and its effect on the eco-environment: Case study on the northern slope of the Tianshan Mountains

Urban agglomerations, which are highly integrated urban groups, form during the advanced stages of industrialization and urban development. The urban agglomeration on the northern slope of the Tianshan Mountains is one of the 19 urban agglomerations promoted by China’s 13th Five-Year Plan and a key area of urbanization in Xinjiang. Based on remote sensing data, we analyzed the expansion of construction land in the urban agglomeration on the northern slope of the Tianshan Mountains and its effect on ecological value in 1980–2015. The results show that the expansion of construction land significantly affected ecological value in the study area over the past 35 years. Among land use types, grassland was the dominant contributor to changes in ecological value;its contribution rate reached 66.27% with an interannual variation of only 5%. The contribution rate of urban and rural residential land along with industrial and mining lands was very low(0.82%), while the interannual variation was large(86%). The area of construction land in the urban agglomeration expanded from 1,067 to 2,586 km^2, and the conversions of different land use types had different effects on ecological value. Among land use types, the conversions of lowcoverage grassland and dry land made the largest contributions to changes in ecological value. During the study period, a total of 1,685 km^2 of ecological land, 69.91% of which belonged to cultivated land and grassland, was converted into construction land.A total area of 1,082 km^2 of dry land and low-coverage grassland was converted into construction land, accounting for 64.21% of the total ecological land that was converted into construction land. In 2000–2015, the area of urban construction land increased significantly along with the proportion of unused land, including gobi(172 km^2), bare land(65 km^2), and salt-affected land(65 km^2), being converted into construction land. In contrast, the area of construction land that was converted into ecological land was less than 166 km^2. The areas with the largest expansions of construction land were concentrated in Urumqi, Karamay,and Changji, where the areas of construction land increased by 399, 186, and 126 km^2, respectively. The areas with the most rapid expansions in construction land were concentrated in Kuytun, Toksun, and Usu. The environmental effects of construction land expansion and land use change were more positive in the late stage of urban agglomeration(2000–2015) compared to in the early stage(1980–2000). Kuytun City, Shihezi City, and Wujiaqu City showed large changes in ecological value caused by the expansion of construction land, whereas the changes in ecological value in the 14 other cities were relatively small, and the expansion of construction land slowed in 2000–2015 compared to in 1980–2000. In the future, further development of the urban agglomeration on the northern slope of the Tianshan Mountains should fully consider the sensitivity and carrying capacity of the vulnerable ecological environment in this area. Population growth and industrial development in the urban agglomeration should be controlled based on the available water resources and ecological capacity to reduce the pressure on the environment and ensure sustainable development.

Fluctuation of Picea timberline and paleoenvironment onthe northern slope of Tian-shan Mountains during the late Holocene

As a good indicator of Holocene climate, the fluctuation of alpine timberline is a synthetical result of impacts of many environmental factors dur-ing geological and historical periods and modern times. As the dominant tree species of mountainous conifer forests on the northern slope of Tianshan Mountains in Xinjiang, the distribution of Picea schrenkiana and its population size are sensitive to climatic change. The typical natural profile of Huashuwozi and the nearby Xiaoxigou archaeologi-cal profile, located in Quanzijie Township, Jimusaer County in Xinjiang, were chosen to analyze and compare the relative high-resolution pollen records, and to measure 14C dating and SEM (scanning elec-tron microscope) microstructure for charcoal frag-ments contained in Xiaoxigou profile’s cultural layers. The results show that in these two profiles, the high percentages of Picea (more than 20% and 35%, re-spectively) appeared in the stratum of the same pe-riod (2000-1300 a BP), which corresponds to the charcoal fragment’s age of Picea schrenkiana con-tained in Xiaoxigou cultural layers. These results convincingly revealed that during the period of 2000-1300 a BP, the timberline for Picea schrenkiana on the northern slope of Tianshan Mountains in Xinjiang declined by about 330m compared with the present.

天山北坡经济带城乡聚落格局变化与影响因素分析

以天山北坡经济带城乡聚落为研究对象,采用景观格局指数、地理信息系统(GIS)空间分析、位序-规模法等分析1980-2020年间城乡聚落格局的变化,结合地理探测器从自然、区位及社会经济因素探究城乡聚落格局的影响因素。结果表明:1980-2020年间,城乡聚落数量、规模持续扩张且趋于集聚,前20 a扩张以耕地、草地为主,后20 a以未利用地为主;城乡聚落密度变化显著,高密度区主要集中在各绿洲呈现“多核集中分布”特征,中密度区沿高密度区周围扩张,低密度区沿绿洲边缘分布并在非绿洲区有扩张;首位聚落规模发展较好,趋于位序-规模曲线,中型聚落略微发育,小型聚落数量持续减少;交通等区位因素是天山北坡城乡聚落格局的首位影响因素,社会经济因素次之,自然地理因素影响较小,各影响因素差异显著。

天山北坡城市群人居环境适宜性评价

基于人居环境自然和人文综合要素,构建了人居环境综合适宜性指数(HSCI),以天山北坡城市群为研究区,分析其2022年的空间分异规律。结果表明:(1)天山北坡城市群自然环境的空间适宜性受地形起伏度和温湿指数影响显著,整体为一般适宜区集中连片分布、高度适宜区零星分布在天山北坡山麓地带的绿洲。其中胡杨河市和乌鲁木齐县的自然环境适宜性最好;(2)人文环境的空间适宜性受夜间灯光指数和基础服务指数的影响较大,整体形成以乌鲁木齐市和石河子市为中心的“双核”空间特征,并有向周围递减的趋势;(3)天山北坡城市群人居环境综合适宜性指数最好的地方人口分布最多,充分体现了乌鲁木齐市作为区域极核的地位;(4)人居环境适宜性指数与天山北坡城市群的人口、经济和土地匹配程度不足。高质量和较高质量区土地面积仅占总量的2.62%,经济则占总量的54.69%,人口高达总量的59.06%。说明天山北坡城市群地区人口与经济在适宜性方面具有高度匹配性,但人居适宜性指数较高的土地存在过度集中和利用的情况。

天山北坡城市群国土空间格局识别与时空变化分析

气候变化和人类活动大环境下,探索国土空间格局演化特征及其规律对进一步缓和绿洲地区人地矛盾有着重要的意义。以天山北坡城市群为例,选取2000、2010年和2020年3期土地利用数据及DEM数据,基于“三生”空间理论对天山北坡城市群国土空间结构数量与空间分布进行分析。结果表明:(1)20 a间天山北坡城市群“三生”空间类型面积呈不同程度的增减,其中水域和林地生态空间的转出量最多,牧草和其他生态空间两者间相互的转换数量最大;(2)研究区除阜康市、木垒哈萨克自治县、奇台县、石河子市及乌鲁木齐市的国土空间利用程度综合指数呈小幅度增加和递减外,其他县域呈逐年提高趋势;(3)生产空间的核密度高值区呈东南-西北条带状,连片分布于研究区的中部,而生态空间的核密度高值区则分布于研究区外围;生活空间的核密度高值区以乌鲁木齐市为中心呈点状分布,周围衍生出许多零碎的中值点,总体分布较为破碎,空间连接性较低。

天山北坡经济带植被覆盖度动态变化研究

为探明天山北坡经济带植被覆盖度时空变化及其原因,本研究基于MODIS13Q1NDVI数据、气象数据、地形数据、人文数据,基于Google Earth Engine(GEE)平台,利用Theil-Sen Median趋势分析、Mann-Kendall显著性检验和稳定性分析方法,探究2000-2020年天山北坡经济带植被覆盖度(FVC)时空变化特征及其影响因子.结果表明:天山北坡经济带的FVC表现为两条平行的高覆盖度带.其中中部地区具有较高的植被覆盖度,而边缘地区的植被覆盖度相对较低.2000~2020年间,天山北坡经济带的FVC在时空上呈轻度变化,约占总变化的70%.植被改善区域主要呈现带状分布,集中在研究区的中部,而植被减少区域主要分布在研究区的南缘.整体上,天山北坡的植被覆盖度呈现出西北至东南的相间分布趋势,并且有逐渐上升的趋势.与东部地区相比,西部地区的植被改善更为明显.2000~2020年间,天山北坡经济带的FVC整体上表现出较高的稳定性和较小的波动,其变异程度介于弱变异和中等变异之间.但是,在克拉玛依市北部、乌鲁木齐市西南部以及研究区南缘的零星地区,FVC存在较强的变异.通过地理探测器模型对天山北坡经济带FVC影响因素的研究表明,人类活动(人口密度、夜间灯光和土地利用类型)是FVC空间分异的主要解释因素.从驱动因素来看,人口密度P值为0.283,对FVC影响最大,夜间灯光P值为0.125,土地利用类型P值为0.179.

天山北坡城市群高质量测度与障碍因子诊断研究

通过熵权TOPSIS方法,测度2020年天山北坡城市群高质量发展水平,并采用障碍因子模型和耦合协调模型,判定影响高质量发展的障碍因子和城市内部协调度。结果表明:高质量综合得分排名为乌鲁木齐市>克拉玛依市>石河子市>吐鲁番市>五家渠市>昌吉市>阜康市;影响乌鲁木齐市主要障碍因子是建成区绿化覆盖率、每万人图书馆数量、人均城市道路面积、建成区排水管道密度;其余城市的主要障碍因子是进出口贸易额、城市GDP、每万人专利授予量、参加基本养老保险的人数;乌鲁木齐市属于轻度失调,石河子市、克拉玛依市和昌吉市属于严重失调,吐鲁番市、五家渠市和阜康市属于极度失调。天山北坡城市群高质量发展水平与内部耦合协调水平低且呈非均衡的空间分布格局,未来应充分发挥各市的区位、资源和产业优势,着力补齐短板,注重全方位协调发展,提升发展质量。

天山北坡典型草地施肥阈值及不确定性分析

在全球气候变化的背景下,干旱半干旱区草地作为陆地生态系统中重要且非常脆弱的组分之一,显现出一系列生态问题。探究气候变化及人类活动对于该区草地生态系统净初级生产力(NPP)的影响,对于合理利用自然资源,保持农牧业可持续发展具有重要的意义。施肥作为促进作物生长的一种方式,合理施肥也可以提高退化草地的NPP。基于此,本研究拟以天山北坡沿海拔梯度分布的4种草地类型:高山草甸(AM)、中山森林草甸(MMFM)、低山干草原(LMDG)和平原荒漠草原(PDG)为研究对象,基于反硝化-分解模型(DNDC)分析该区典型草地生态系统净初级生产力对施加不同氮肥的响应,并揭示施肥阈值及最优施肥方式。结果表明:1)适度氮肥添加促进了各个类型草地生态系统NPP的增长,但草地NPP对施肥量的响应存在阈值,且不存在适用于4种草地类型的统一最优施肥方式。LMDG草地生态系统对施氮肥的响应最敏感。2)PDG草地NPP达到最大的施肥方式为一年分两次施加100 kg·hm^(-2)硝酸盐,NPP的最大值为68.72 g C·m^(-2)·a^(-1)。LMDG草地NPP最大的施肥方式为一年分两次施加尿素260 kg·hm^(-2),NPP的最大值为263.28 g C·m^(-2)·a^(-1)。MMFM草地生态系统达到NPP最大的施肥方式为一年一次施尿素80 kg·hm^(-2),NPP的最大值为171.22 g C·m^(-2)·a^(-1)。无水氨作为在AM草地中反应最好的氮肥,以最小的施肥量(60 kg·hm^(-2))达到了NPP的最大值(114.62 g C·m^(-2)·a^(-1))。3)通过蒙特卡洛不确定分析的结果显示,施肥时间对PDG和LMDG的影响更为明显,施肥量波动对LMDG和MMFM的影响较其他两种草地更为明显。

天山北坡绿洲乡村聚落空间基因解析及影响机制研究

空间基因蕴含着聚落与环境互动形成的空间信息,在空间特色传承上有着重要作用。由于新疆天山北坡地区聚落在独特的自然环境中形成了互动演化的聚落空间形态,因此以其为研究对象,通过卫星影像图和三维数据采集其中的12个典型聚落样本,在从自然环境、空间片段形态、聚落形态、路网形态和拓扑连接五方面提取空间基因的基础上,构建聚落空间基因图谱,运用因子分析与聚类分析方法,对聚落进行分类,阐释其背后蕴含的环境-空间互动影响模式,并提出保护与改造建议,以期为不同地区乡村聚落空间基因研究提供借鉴,为聚落类型划分、乡村特色保护与发展提供研究思路。

基于InVEST模型的天山北坡城市群生境质量时空演化研究

生境质量与土地利用/土地覆被类型为生物多样性所提供栖息地的适宜性有密切关系。探究天山北坡城市群土地利用引发的生境质量变化特征,揭示区域生态系统脆弱性,可为生态服务功能改善及区域生态环境保护提供一定参考。基于2000—2020年天山北坡城市群土地利用数据,采用InVEST模型从时空维度进行生境质量测算,再采用莫兰指数对生境质量空间特征进行分析。结果表明:(1)2000—2020年天山北坡城市群生境质量指数值整体在0.8以上,虽然生境质量为差和较差等级区域面积占研究区总面积的比例较高,但整体向良好和优等级方向发展;(2)天山北坡城市群生境质量由优和良好等级转为差和较差等级区域面积占比为3.75%,而由较差向差等级持续恶化的区域面积占比高达10%;(3)天山北坡城市群生境质量高值区与低值区在空间上均存在较高的正相关特征,即生境质量在空间上呈现高-高集聚和低-低集聚的两极特征,且随着时间推移,这种趋势愈发明显。总体上,研究期间天山北坡城市群生境质量空间变化幅度不大,上升区域上升的主要原因是生态工程的实施改变了区域土地利用/覆被类型,使得生境适宜性增强,而下降区域下降的主要原因是建设用地扩张。因此,建议进一步加大研究区生态保护和生态恢复措施。

天山北坡区域大气污染特征及冬季重污染成因分析——以石河子市为例

以天山北坡典型代表城市石河子市为例,基于地面常规污染物浓度监测、气象观测、激光雷达观测及中尺度气象模型(WRF)模拟资料,综合分析了气象条件和边界层结构变化对空气质量的影响。结果表明:以石河子市为代表的天山北坡地区空气质量季节性差异显著,PM_(2.5)浓度在冬、夏两季相差最高达11.4倍,且冬季(12月—次年2月)大气污染发生率高达81.2%,重度及以上污染天气占59.1%。冬季污染呈连续“污染季”变化特征,在2020—2021年冬季发生的4次重污染过程中,每次重污染过程持续时间为7~27 d,间隔仅1~3 d,各过程均以PM_(2.5)污染为主导,PM_(2.5)峰值浓度为373~425μg/m^(3),PM_(2.5)/PM_(10)均值为0.82。进入秋冬季后,地面连续低温、高湿的气象条件对PM_(2.5)浓度的增长有显著促进作用,以温度<-3℃和65%<相对湿度<92%为主要影响条件,在该条件下边界层高度的显著降低和连续强逆温引起的近地扩散条件转差,是冬“污染季”形成的根本原因。在2021年1月16—22日重污染过程期间,地面为持续低温、高湿、微/静风状态,重污染生消仅随边界层和逆温条件改变,其中污染累积时段边界层高度较清洁时段降低近5倍,逆温强度超过1.5℃/(100 m),后续由逆温的减退和边界层抬升带来3 d清洁天气。

新疆草地时空动态及其对气候变化的响应——以昌吉回族自治州为例

基于MODIS NPP、EVI遥感影像,采用MVC法、一元线性回归法与Pearson相关分析法,探讨天山北坡昌吉州草地植被时空动态及其对同期气温、降水的响应。结果表明:2000—2020年,草地植被NPP、EVI均为跃动式显著递增,2016年后呈逐年递减;NPP、EVI多年均值为0.095 kg C·m^(-2)、0.186;相较于2000年(NPP=0.077 kg C·m^(-2)、EVI=0.166),2020年NPP(0.099 kg C·m^(-2))、EVI(0.194)分别增长了28.57%、16.87%。草地NPP空间异质性显著增加并呈扩大趋势,EVI空间差异逐年递增,变化范围分别为0.038 kg C·m^(-2)(NPP)、0.059(EVI)。在空间上,NPP、EVI多年平均分布具有差异;总体上,NPP、EVI随海拔升高而增加,但绿洲边缘、古尔班通古特沙漠南缘分布有高位EVI,面积占比65.01%的NPP与21.93%的EVI显著递增。9种草地类型植被NPP、EVI与降水呈显著正相关的面积占比远大于同期气温,不同类型草地对降水的响应具有差异。降水是草地植被的重要影响因子,但高海拔区域的适度增温有益于草地植被生长。

天山北坡中段天然草地植物群落特征及变化规律研究

【目的】调查天山北坡中段垂直带上三种典型草地类型植被基本优势种情况,以及三种草地类型在植被生长季内植物群落基本特征及动态变化规律。【方法】采用实地观测固定样方法,每月固定时间监测植物群落基本特征数据。【结果】三种不同草地类型天然草地植物群落优势种不同月份所表现出的重要值和基本特征规律均不相同,三种草地类型植物群落各优势种的重要值在不同月份无固定规律,各优势种在不同月份的优势性也会有变化;天山北坡中段山地草甸植物种类丰富,建群种植物主要为中生禾草和杂类草,优势种植物主要为无芒雀麦、鸭茅和羽衣草,生长季内草层平均高度为6.8~32.2 cm,植被盖度80%~100%。山地草原植物群落结构简单,优势种植物主要为苔草、羊茅和针茅,生长季内草层平均高度为6.3~12.6 cm,植被盖度62%~80%。山地荒漠植被稀疏,优势种植物主要为冷蒿、镰芒针茅和盐爪爪,生长季内草层平均高度为6.9~11.9 cm,植被盖度23%~35%,覆盖度较低,草地退化现象明显。【结论】天然草地植物群落基本特征及变化规律受气候影响较大,尤其受降水量影响很大。本研究中不同草地类型各优势种植物各监测指标在不同月份呈现的规律有所不同,但与植物本身生长发育规律基本一致。

天山北坡中段雪岭云杉径向生长对气候变化的响应

分析树木径向生长对气候变化的响应,有利于准确预测未来森林的动态变化。天山北坡中山带广泛分布着以雪岭云杉(Picea schrenkiana)为单优树种的温带针叶林,本研究采集该处高海拔雪岭云杉树芯样本,用树木年轮学方法探究雪岭云杉径向生长对气候因子及干旱事件的响应特征。结果表明:(1)1960—2020年,雪岭云杉树轮宽度指数呈极显著上升趋势,未出现生长衰退现象,表明近期雪岭云杉生长状况良好。(2)雪岭云杉树轮宽度主要与当年6—8月气温,4月降水及除当年7月外的各月scPDSI显著正相关;滑动相关显示,雪岭云杉树轮宽度与气候因子的关系不稳定,1991年后,云杉对气候因子的正响应进一步加强。(3)雪岭云杉径向生长变化百分率在1879—1880年低于-25%,表明其在1879—1885年发生了生长衰退;随干旱频率和强度的增加,雪岭云杉应对干旱事件的抵抗力和恢复力下降,当云杉长时间处于水分较充足的环境而遭受突发干旱事件时,会导致其抵抗力严重下降,易发生生长衰退。综上所述,在气候变化背景下,升温在近期仍有利于该区域高海拔雪岭云杉径向生长,但升温过程中伴随着干旱频率和强度的增加,将使雪岭云杉的抵抗力和恢复力进一步下降,生长衰退风险升高。即在近期,雪岭云杉会在升温促进生长和干旱抑制生长间不断博弈,最终产生何种影响需进一步观察研究,未来应采取多种手段密切监测其生长动态。