Landscape Frontiers,Geography Frontiers: Lessons to Be Learned     

George P. Malanson  Yu Zeng  Stephen J. Walsh 《The Professional geographer》2006,58(4):383-396

Advancing ecotones, such as treelines and frontiers of human settlement, may share some characteristic dynamics because both include feedbacks between spatial pattern and process. Both might be examined as complex, self‐organizing systems in terms of complexity theory and thus be usefully compared. A cellular automaton of advancing alpine treeline in Montana shows attractors in power‐law frequency distributions of spatial and temporal pattern. Frontiers of study areas in the Amazonian region of Ecuador, analyzed using change detection of Landsat Thematic Mapper imagery, have power‐law distributions of advancing deforestation. Alternative approaches in self‐organized complexity, including self‐organized percolation, and the inverse cascade model, and an approach to complexity involving optimization, highly optimized tolerance, are considered. Some combination of these, based on their common ancestry in percolation theory (with its ties to geocomputation), might provide insights into population‐environment interactions at settlement frontiers and ecotones together, given comparisons drawn between the spatial feedbacks at alpine treeline and in Ecuador. GIScience and landscape ecology can develop synergies by building on this area of geocomputation and complexity theory, as in analysis of attractors in state spaces of spatial metrics from spatially explicit simulations and representing their uncertainty.  相似文献   

Invertebrate and microbial responses to inundation in an ephemeral river reach in New Zealand: effects of preceding dry periods     

Scott T. Larned  Thibault Datry  Christopher T. Robinson 《Aquatic Sciences - Research Across Boundaries》2007,69(4):554-567

Inundation marks the shift from a terrestrial ecosystem to an aquatic ecosystem in ephemeral rivers. The forms and rates of responses by aquatic invertebrates and sediment microbes to inundation depend on desiccation resistance during preceding dry periods. We assessed invertebrate and microbial responses to inundation over a range of preceding dry periods in an ephemeral reach of the Selwyn River, New Zealand. Microbial response variables were dissolved oxygen consumption and non-specific esterase activity. Sampling sites along the reach had been continuously dry for 1–592 d prior to sample collection. The onset of flow simulated by an experimental inundation led to the appearance of aquatic invertebrates in all samples, but the assemblages varied with the length of the preceding dry period. Taxon richness decreased linearly with dry period length while density decreased exponentially. These patterns indicate that a large number of individuals from desiccation-sensitive taxa were eliminated soon after flow ceased, and a low-density assemblage composed of a small number of desiccation-resistant taxa persisted during prolonged dry periods. As with invertebrate density, sediment respiration and nonspecific esterase activity decreased with length of dry period, and were characterized by exponential decay functions. The results of the inundation experiments suggest that a temporal ecotone exists for about one week after the disappearance of flowing water, and before the terrestrial system stabilizes.  相似文献   

On paleodrainage evolution in mid-late Epipleistocene based on radar remote sensing in northeastern Ejin Banner, Inner Mongolia     

WANG Xinyuan  GUO Huadong  CHANG Yueming  ZHA Liangsong 《地理学报》2004,14(2):235-241

Radar remote sensing can acquire information of sub-surface covered by sand in arid area, detect surface roughness and vegetation coronet's layer and linear feature such as linear structure and channel sensitively. With sediment facies analysis, this paper studies the features of environmental evolution in mid-late Epipleistocene (60 ka BP-20 ka BP) in northeastern Ejin Banner. The conclusions are listed as follows: (1) The evolution of the three lakes, i.e. Gaxunnur, Sugunur and Tian'e lakes, are dominated by faults and regional climate. (2) By analyzing sedimentary section of old Juyanze Lake, the three lakes used to be a large outflow lake before 50 ka BP in northeastern Ejin Banner, and at 50 ka BP, temperature declined rapidly in northwestern China. The event caused the lake's shrinkage. (3) By fault activity uplift in the northern part of old Juyan Lake and depression in the southern part, the lake's water followed from north to south at around 35 ka BP, old Juyanze fluvial fan was formed. At the same time, Juyan Lake separated from Sugunur Lake and Wentugunr old channel was abandoned. (4) In recent 2000 years, Ruoshui River is a wandering river, sometimes it flows into Juyan Lake and sometimes Sugunur and Gaxunnur lakes. Due to human activities and over exploitation, the oasis ecosystem is rapidly degenerated in 15 years (1986-2000).  相似文献   

Water regime in soils and plants along an aridity gradient in central Baja California, Mexico     

Ernesto Franco-Vizcaíno 《Journal of Arid Environments》1994,27(4)

The Central Desert of Baja California has pronounced climatic gradients. Water storage in the upper metre of soil and leaf water potentials in Larrea tridentata, Simmondsia chinensis and Fouquieria columnaris were monitored during 28 months at six sites. Estimated annual evapotranspiration was 75-150 mm in sandy loams, and 45-60 mm in sandy soils. Cumulative recharge accounted for 80% of precipitation in loams, but only 50% in sands. During the study period, increased aridity was expressed as longer periods of drought, but there was no less recharge. Weak to moderate relationships were found between soil water content and predawn leaf water potential.  相似文献   

Landscape Analysis of the Forest-Tundra Ecotone in Rocky Mountain National Park,Colorado*     

William L. Baker  Peter J. Weisberg 《The Professional geographer》1995,47(4):361-375

Landscapes in the ecotone between forest and tundra contain a mosaic of patches of trees, meadows, lakes, disturbed areas, and other features. The structure of this mosaic affects species habitat and potential ecotone response to global change. However, the alpine forest-tundra ecotone may be insensitive to climatic change if it is a climatic relict or is frequently disturbed. We used GIS and multivariate statistics to (1) analyze landscape structure in transects across the ecotone in Rocky Mountain National Park, (2) identify the major variants of forest-tundra ecotone, and (3) identify the influence of the environment and natural disturbances on variation in the landscape structure of the ecotone. There are six major types of ecotone varying in the amount of natural disturbances, permanent features (e.g., lakes), closed forest, patch forest, and krummholz. Variation is primarily related to slope, elevation, aspect, and geology associated with the morphology of the mountains and the disturbances they produce. The ecotone is not strongly structured by natural disturbances; thus, it may be more strongly controlled by and sensitive to climatic change than in areas where disturbance is more prevalent. Monitoring of potential ecotone response to global change is feasible, if tailored to the types of ecotone and their expected response.  相似文献   

准噶尔盆地东南缘绿洲荒漠交错带土壤动物群落特征     

吾玛尔·阿布力孜  阿布都如苏力·吐孙  古丽布斯坦·努尔买买提  吴松林 《中国沙漠》2012,32(6):1617-1625

为理解准噶尔盆地东南缘绿洲-荒漠交错带土壤动物群落特征,采用国际通用采样方法在2010年4月、7月、9月及11月中旬对该交错带不同生境土壤动物群落进行了调查研究,比较分析了该区土壤动物群落组成、多样性及其季节动态特征。结果表明:①共采集到大、中小型土壤动物9 788只,隶属于4门12纲32目,其中甲螨目、弹尾目、中气门目和前气门目为优势类群,常见类群有垫刃目、鞘翅目幼虫、膜翅目、无气门目、缨翅目和双翅目幼虫,优势类群和常见类群占群落总个体数的96.27%,其他22类群均属于稀有类群,只占总捕获量的3.73%。②在不同生境土壤动物群落组成、个体数量及多样性都表现出了明显的时空变异（P<0.05）,其类群数高低顺序为自然林＞防护林＞牧草地＞灌木林＞耕地＞菜瓜地＞荒草原＞荒漠,而个体数量顺序为菜瓜地＞耕地＞牧草地＞防护林＞自然林＞荒草原＞灌木林＞荒漠。③不同生境土壤动物的垂直分布具有明显的表聚特征,即从地表向下,随着土壤深度的增加土壤动物个体数量逐渐减少。④在不同生境土壤动物个体数量表现出了明显季节变化,其高低顺序为冬季＞秋季＞春季＞夏季。研究结果为进一步开展干旱区绿洲-荒漠生态系统土壤动物生态学的研究奠定了基础。  相似文献   

草地退化对植物硅分布和植硅体碳汇的影响:以北方农牧交错带草地为例     

杨石磊  宋照亮  郝倩  张晓东  杨孝民  夏少攀  杨伟华 《第四纪研究》2019,39(1):89-98

草地生态系统中,硅(Si)不仅在植物生长过程中扮演着重要的角色,而且通过形成植硅体碳(Phytolith-Occluded Carbon,简称PhytOC)的方式参与陆地生态系统碳循环。近几十年来,由于人为干扰等因素导致的草地退化引起了广泛的关注。本研究中,我们选取了我国北方农牧交错带中30个不同退化程度的样地,分析了8种常见植物(共71个样品)地上部分Si含量和分布特征,并估算了植硅体碳产生通量。结果发现,随着草地退化的加剧,糙隐子草(Cleistogenes squarrosa)地上部分Si含量呈下降趋势,而羊草(Leymus chinensis)表现为先上升后下降的倒"V"型。不同退化程度样地植物地上部分Si平均含量分别为12.25±1.02 g/kg(轻度)、10.56±1.15 g/kg(中度)和8.06±0.93 g/kg(重度),而植硅体碳产生通量显著下降,分别为0.320±0.038 kg/(ha·a)、0.190±0.021 kg/(ha·a)和0.068±0.006 kg/(ha·a)(P<0.05)。研究表明,草地退化对不同种类植物的Si含量和产生通量的影响不同,这可能是由于植物的功能类型不同造成的。草地退化可以导致种群结构的变化和地上净初级生产力(ANPP)的降低,从而影响草地植物地上部分Si的分布和植硅体的固碳能力。当退化严重时,初步估算北方农牧交错带内草地植物地上部分植硅体固碳速率将下降5倍以上。  相似文献   

河流生态护岸研究进展综述   总被引：1，自引：0，他引：1  

梁开明  章家恩  赵本良  叶延琼  孔旭晖 《热带地理》2014,34(1):116-122

生态护岸是结合生态工程与土木工程技术的一种护岸形式,对保护岸坡结构稳定和维护河流生态环境的可持续发展起着重要作用。文章简要综述了国内外生态护岸的产生背景及发展现状,在此基础上探讨了生态护岸的概念与内涵。根据应用条件和功能特征,对生态护岸的一些代表性类型、采用的材料、技术以及各类生态护岸的适用范围进行了分类描述。通过国内外的研究实例,对目前生态护岸技术的研究方法进行了系统的归纳,并结合现状分析了当前生态护岸在应用中存在的问题,提出应该针对不同环境条件以及不同功能要求,因地制宜地建设既能确保安全又能兼顾一定生态效应的护岸。最后展望了在生态护岸的生态系统服务功能、评价标准体系以及可持续利用管理等方面尚需继续深入进行的研究和探索。  相似文献   

新疆提孜那甫河流域山区冰草生态交错带的空间格局及其动态变化研究   总被引：1，自引：1，他引：0  

陈蜀江  贾翔  黄铁成  陈孟禹 《冰川冻土》2015,37(6):1650-1659

冰-草生态交错带是陆地生态交错带的重要类型之一, 对其进行有效监测和研究对于生物多样性的保护具有重要意义. 利用2004-2013年近10 a的MODIS10A1数据提取积雪日数, 结合DEM和Landsat影像研究提孜那甫河流域山区的冰-草生态交错带的时空格局及其动态变化. 结果表明: ①近10 a 来交错带的平均面积为5 749 km², 占研究区总面积的37.83%. ②交错带分布由西南向东北偏移, 在东北坡、东坡分布较西坡和北坡多, 主要分布在海拔4 600~4 900 m的区域; 在坡度大于25°陡坡以上的区域分布较多. ③近10 a间冰-草生态交错带面积总体呈波动上升趋势, 总增长率为10.68%, 年均增长约66.78 km²; 其中2005年和2009年交错带面积较前一年有所明显下降, 而2007年交错带面积上升较为明显; 交错带面积与气温呈强正相关, 与降水呈弱负相关. ④近10 a交错带的平均海拔呈缓慢上升趋势, 2013年的交错带分布的平均海拔较2004年上升了45 m; 而近50 a来研究区高寒草甸带向上爬高了约100 m左右.  相似文献   

Development of quantitative methods for detecting climate contributions to boundary shifts in farming-pastoral ecotone of northern China   总被引：3，自引：0，他引：3  

Wenjiao Shi  Yiting Liu  Xiaoli Shi 《地理学报(英文版)》2017,27(9):1059-1071

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.  相似文献