0001−0011  Characteristics of permafrost degradation in Northeast China and its ecological effects: A review … ShanShan Chen, ShuYing Zang, Li Sun

Abstract: Latitudinal permafrost in Northern Northeast (NNE) China is located in the southern margin of the Eurasian continent, and is very sensitive to climatic and environmental change. Numerical simulations indicate that air temperature in the permafrost regions of Northeast China has been on the rise since the 1950s, and will keep rising in the 21^st century, leading to extensive degradation of permafrost. Permafrost degradation in NNE China has its own characteristics, such as northward shifts in the shape of a "W" for the permafrost southern boundary (SLP), discontinuous permafrost degradation into islandlike frozen soil, and gradually disappearing island permafrost. Permafrost degradation leads to deterioration of the ecological environment in cold regions. As a result, the belt of larch forests dominated by Larix gmelinii has shifted northwards and wetland areas with symbiotic relationships with permafrost have decreased significantly. With rapid retreat and thinning of permafrost and vegetation change, the CO₂ and CH₄ flux increases with mean air temperature from continuous to sporadic permafrost areas as a result of activity of methanogen enhancement, positively feeding back to climate warming. This paper reviews the features of permafrost degradation, the effects of permafrost degradation on wetland and forest ecosystem structure and function, and greenhouse gas emissions on latitudinal permafrost in NNE China. We also put forward critical questions about the aforementioned effects, including: (1) establish long-term permafrost observation systems to evaluate the distribution of permafrost and SLP change, in order to study the feedback of permafrost to climate change; (2) carry out research about the effects of permafrost degradation on the wetland ecosystem and the response of Xing'an larch to global change, and predict ecosystem dynamics in permafrost degradation based on long-term field observation; (3) focus intensively on the dynamics of greenhouse gas flux in permafrost degradation of Northeast China and the feedback of greenhouse gas emissions to climate change; (4) quantitative studies on the permafrost carbon feedback and vegetation carbon feedback due to permafrost change to climate multi-impact and estimate the balance of C in permafrost regions in the future.

东北多年冻土退化特征及生态效应综述  陈珊珊，臧淑英，孙丽

东北多年冻土位于欧亚大陆的南缘，对气候和环境变化十分敏感。自1950年以来，东北多年冻土区处于升温状态，并在21世纪保持升温趋势，导致多年冻土广泛退化。东北多年冻土退化有其自身的特征，例如多年冻土南部边界呈“W”形向北移动，不连续的多年冻土退化成岛状冻土，且岛状多年冻土在逐渐消失。东北多年冻土退化导致寒区的生态环境恶化。多年冻土退化导致以落叶松为主导的落叶松林带向北移动，与多年冻土共生的湿地面积明显减少。随着多年冻土和植被变化，在连续多年冻土到岛状多年冻土的过程中，气温随之升高，产甲烷菌活动增强，CO₂和CH₄通量随之增加，对气候变暖具有正反馈作用。本文综述了东北多年冻土退化的特征，多年冻土退化对湿地和森林生态系统结构和功能的影响以及温室气体排放的影响，并提出了关于上述影响的关键问题：（1）建立长期的多年冻土观测系统，以评估多年冻土的分布和SLP变化，从而研究多年冻土对气候变化的反馈；（2）研究多年冻土退化对湿地生态系统的影响以及兴安落叶松对全球变化的响应，并根据长期的实地观测，预测多年冻土生态系统的动态变化；（3）重点研究东北多年冻土退化温室气体通量的动态以及温室气体排放对气候变化的反馈；（4）基于多年冻土变化对气候的多重影响，对多年冻土碳反馈和植被碳反馈进行定量研究，估算未来多年冻土区的碳平衡。

 0012–0021  Aeolian processes on sandy desertification of an alpine meadow: A wind tunnel experiment … ZhiShan An, KeCun Zhang, LiHai Tan, BaiCheng Niu, YanPing Yu

Abstract: In recent years, the desertification of alpine meadows has become a serious ecological problem and has gradually become a threat to regional economic activities in Maqu County. To reveal the mechanism for sandy desertification of alpine meadows, we conducted wind tunnel experiments on aeolian processes over sandy alpine meadows. Results show that the sandflux profile of mix-sized sediment decays exponentially with increasing height. However, the profile pattern of a group of uniform-sized particles depends on the experimental wind speeds. The profile pattern of all the groups studied can be expressed by exponential decay functions when the wind speed is less than or equal to 16 m/s. while that for all the groups studied can be expressed by a Gaussian distribution function when the wind speed is above 16 m/s. The average saltation heights of mixed sands at wind speeds of 12 m/s, 16 m/s, 20 m/s, and 24 m/s were 2.74, 4.19, 5.28, and 6.12 cm, respectively. The mean grain size basically first decreases and then increases with increasing height under different wind speeds. The sorting improves with increasing wind speed, while the kurtosis and skewness show relationships with only the characteristics of the parent soil.

高寒草地沙化过程与机理的风洞实验研究  安志山，张克存，谭立海，牛百成，鱼燕萍

近年来在全球气候变暖背景下，玛曲县高寒草地的沙化问题日趋严重，对区域内的生态环境和社会经济产生重大威胁。本文利用风洞实验模拟区域高寒草地的沙化过程并揭示其机理。研究结果表明：与低海拔地区风沙流结构相比，高寒沙化草地表层输沙率与高度之间亦呈指数关系。在12 m/s和16 m/s风速下，所有粒径组的输沙率与高度之间符合指数函数。当风速增加至20 m/s，除中沙的输沙率与高度之间符合指数函数外，细沙、极细沙、粉沙和粘土的输沙率与高度之间符合高斯函数。当风速增加至24 m/s，所有粒径组的输沙率与高度之间符合高斯函数。12 m/s、16 m/s、20 m/s和24 m/s实验风速下沙粒的跳跃高度依次为2.74 cm、4.19 cm、5.28 cm和6.12 cm，且风速超过16 m/s，沙化草地表层的蚀积强度明显增加。

沙粒平均粒径随高度增加表现为先减小后增加，分选性随风速增大趋于变好，峰态和偏度与土壤母质的粒径分布规律一致，与实验风速和高度无关。

0022–0033  A case study on Landscape Component Niche based on Landscape Pattern Indices: Yanchi, Ningxia Province, China … XiaoNing Zhang, XueLu Liu, Ghanney Philip, XiaoDan Li, QuanXi Wang, YaNan Xu, TingTing Hui     

Abstract: Yanchi County is located in the agro-pastoral ecotone and belongs to the ecologically fragile area of Northwest China. It is important to study the evolution of landscape pattern to curb its environmental degradation. In order to intuitively show how the landscape pattern of the study area changes over time, Landsat Thematic Mappers (TM) and Landsat Operational Land Imager (OLI) data of 1991, 2000, 2010 and 2017 were used. This paper attempts to apply niche theories and methods into landscape ecology, and constructs a niche model of landscape components by using "n-dimentional hypervolume niche theory" and landscape pattern indices. By evaluating the spatial and temporal evolution of niche from the perspective of two-dimensional space to reflect the changes of landscape pattern in the study area over the past 26 years, new theories

and methods were introduced for the characterization of landscape pattern. The results indicate that: 1) The larger the attribute and dominance value of landscape components, the higher the ecological niche and the stronger the control effect on the overall landscape. 2) The ecological niche of each landscape component was significantly different, just as its control effect on the overall landscape. 3) The dynamic change of the ecological niche of each landscape component was different, with grassland, unused land and arable land always in a high dominant position, although the ecological niche of construction land and water area was always low. In general, the introduction of niche theory into the landscape ecology provided a new method to study the changes in regional landscape pattern.

基于景观格局指数的景观组分生态位研究——以宁夏盐池县为例  张晓宁，刘学录，Ghanney Philip，李晓丹，王全喜，徐亚男，惠婷婷

盐池县处于农牧交错带上，属于生态脆弱区，研究其景观格局的演变对遏制其环境恶化具有重要的指导意义。为了更直观地展现研究区的景观格局如何随时间变化，本研究使用1991年、2000年、2010年和2017年的Landsat TM和Landsat OLI数据，尝试将生态位的理论和方法应用于到景观生态学当中，运用“多维超体积生态位”理论和景观格局指数构建了景观组分生态位模型，通过二维空间角度评估生态位的时空演变去反映研究区26年来景观格局的变化，为景观格局的表征引入了新的理论、方法和研究视角。结果表明：（1）景观组分属性值和优势度值越大，生态位越高，对整体景观的控制作用越强；（2）各景观组分生态位具有显著差异，对整体景观的控制作用不同；（3）各景观组分生态位的态势变化不同，且草地、未利用地和耕地始终处于较高优势地位，而建设用地和水域的生态位始终较低。总的来说，将生态位理论引入到景观生态学当中，为研究区域景观格局的变化提供了新的方法。

0034–0046  Soil-moisture dynamics and tree-water status in a Picea crassifolia forest, Qilian Mountains, China … Hu Liu, Lin Li, SiJia Wang, QiYue Yang, WenZhi Zhao

Abstract: Landscapes of the mountainous regions in northwestern China comprise a unique pattern of vegetation, consisting of a mosaic of grassland and shrub-forest. Forests generally self-organize into ordered structures and coalesce into blocks on north-facing slopes or stripes along southeast-facing slopes, with Picea crassifolia being the most representative and dominant tree species. We investigated the tree-water status and soil-moisture dynamics at a forest site (Guantan) of the Qilian Mountains in northwest China. The 30-minute-interval measurements of tree-sap flow during the growing season of 2008 are presented, and the potential functional relations between tree transpiration and environmental factors are evaluated. Soil moisture and solar energy were identified as the most influential factors, explaining more than 70% of the variance in sap flow. Based on field measurements obtained at the forest site, a stochastic model of soil-moisture dynamics was tested; and the steady-state probability density functions (PDFs) of the long-term soil-moisture dynamics and static tree-water stress were estimated using the validated model and parameters. We found that the model reproduced measured soil moisture well, despite all the simplifying assumptions. The generated PDF of long-term soil moisture was relatively open, with middle to low average values; and the calculated density of the static tree-water stress at the forest site was largely concentrated between 0 and 0.6, suggesting a moderate water-stress situation in most cases. We argue that both water and energy are limiting factors for vegetation at the forest site. In addition, the tradeoff between reduced evapotranspiration (ET) from limited solar energy and increased soil-moisture availability may create a stressed but tolerable environment and, in turn, produce a relatively constant ecological niche favorable to Picea crassifolia growth.

祁连山青海云杉林土壤水分动态与植被水分状况  刘鹄，李琳，王思佳，杨淇越，赵文智

中国西北干旱区山地系统多呈现一种以草地景观类型为基质，灌木和森林等其它景观类型作为斑块镶嵌、空间上具有明显自组织特征的林草复合结构；森林通常在阴坡与半阴坡呈斑块或条带状分布，青海云杉是其主要建群种。本文利用祁连山典型森林观测站点(关滩)获得的树干液流与环境要素数据，定量分析了青海云杉林生长季土壤水分动态和林木水分状况，发现土壤水分与太阳辐射是影响树干液流最重要的环境因子，二者对树干液流数据变异方差的解释率高达70%。利用随机土壤水分动态模型和水分胁迫函数，模拟分析了青海云杉林在其特殊气候条件下土壤水分与水分胁迫的稳态概率密度函数（Probability density functions，PDFs），结果表明：土壤水分的概率分布范围相对较宽但峰值却出现在中低水平（s=0.3），相应的植被水分胁迫（）概率分布范围为0~0.6，因此祁连山青海云杉林常处于中度水胁迫状态。认为能量和水分都是祁连山青海云杉林生长的限制因素，但能量因素在限制植被生长速率的同时也减少了其蒸散发需求，因此在一定程度上又提高了土壤水分的可获得性，这种权衡关系（Tradeoff）有利于青海云杉获得一种存在环境胁迫却又能够应对的、可以维持相对缓慢却能长期稳定生长的环境生态位。

0047–0058  Culturable bacterial diversity in hypolithic and peripheral soils in the west of the Hexi Corridor desert and its influencing factors … LiFang He, ShiWeng Li, GaoSen Zhang, XiuKun Wu, BingLin Zhang, Wei Zhang

Abstract: Microbes inhabiting the desert respond sensitively to environmental changes and may be an indicator for changes in the desert ecosystem. Hypolithic microbial communities in the desert play a vital role in ecosystem processes such as soil formation and organic matter accumulation. This study investigated and compared the culturable bacterial community structure and diversity in hypolithic and peripheral soils, and the interaction between bacteria and environmental factors. The bacteria were isolated using four different kinds of media and identified by 16S rRNA gene-sequence analysis. The numbers of culturable bacteria in the hypolithic and peripheral soils ranged from 3.0×10⁴ to 3.6×10⁵ CFU/g and from 6.5×10⁴ to 5.3×10⁵ CFU/g, respectively, indicating that the bacteria number in peripheral soil was higher than that in hypolithic soil. A total of 98 species belonging to 34 genera were identified, among which Arthrobacter, Bacillus, and Streptomyces were found dominantly and widely distributed. The community of culturable bacteria had obvious sample specificity, and the diversity in hypolithic soil was higher than that in peripheral soil. On the regional scale, the distribution of culturable bacteria and the environmental factors showed regular changes. On the local scale, the high heterogeneity of the hypolithic environment determined the specificity of the number and species of culturable bacteria.

河西走廊西部石下与石周可培养细菌的多样性及其影响因素研究  何丽芳，李师翁，章高森，伍修锟，张昺林，张威

生存于荒漠中的微生物对地球环境的变化高度敏感，对荒漠地区生态系统的变化具有一定的指示作用。石生微生物在荒漠生态系统土壤形成和有机质积累中起着重要作用。本研究调查了河西走廊西部石下和石周土壤中可培养细菌群落的结构和多样性，分析了细菌与环境因子之间关系。用4种培养基对石下和石周土壤中的细菌进行了分离和纯化，并进行了16S rRNA基因序列分析与鉴定。结果表明，石下可培养细菌的数量为3.0×10⁴~3.6×10⁵ CFU/g，石周表层土细菌数量为6.5×10⁴~5.3×10⁵ CFU/g。共鉴定可培养细菌34属98种，以节杆菌（Arthrobacter）、芽孢杆菌属（Bacillus）和链霉菌属（Streptomyces）为优势属和广布属。可培养细菌群落结构具明显的样点特异性，石下生可培养细菌的多样性高于石周土。在区域尺度上，石下环境的高度异质性决定了可培养细菌的数量和种类的特异性。