北方农牧交错区草原利用与禁牧政策的关键问题研究          下载免费PDF全文

周立华  侯彩霞 《干旱区地理》2019,42(2):354-362

草原作为我国最大的陆地生态系统，对生态安全、生物多样性、畜牧业等具有重要的意义，但草原生态承载力有限，随着人口和社会经济压力的不断增加，对草原的过度利用导致草原生态破坏严重，草原生态系统面临巨大威胁。为了恢复和保护草原生态系统，2002年前后国家在草原破坏严重的地区实施禁牧政策。政策实施以来，草原得到很大程度的恢复，生态效果明显，但政策实施过程中也出现了一些新的问题。探索北方农牧交错区草原利用效率和存在的问题可为进一步制定相关政策提供依据，对北方农牧交错区的生态环境修复和可持续发展有重要的意义。本文通过对相关文献的综述和典型禁牧区的研究，从禁牧政策的效益、问题和农户支持度等方面，进行了研究和论述，主要结论包括：（1）北方农牧交错区草原生态承载力低，生态赤字严重。（2）禁牧政策虽对生态环境的改善起到很大作用，但在一些禁牧区，当地政府不能因地制宜实施禁牧政策，再加上配套实施和基础设施滞后，草场界限模糊以及政策宣传和监管力度不够等问题导致了新的草原退化，草原生态恢复大打折扣。（3）禁牧政策实施对农户的生产和生活造成一定的影响，部分农户无法顺利完成生计方式的转型，又因生态补偿标准低和补偿有失公平等问题无法弥补禁牧造成的经济损失，导致农户生活水平有所下降，加深了生态环境与农户生计之间的矛盾，部分农户对禁牧政策的支持度较低。  相似文献   

Topography-Controlled Soil Water Content and the Coexistence of Forest and Steppe in Northern China     

《自然地理学》2013,34(6):561-573

The semi-arid forest-steppe ecotone in China is characterized by a patchy pattern of forest and steppe, with forest patches restricted to shady slopes. To address the effect of topography on forest distribution through regulation of available water, we calculated evaporation as a function of slope aspect and inclination. Field vegetation records from randomly selected sites with minimum slope inclination were used to test the simulated forest distribution. Seasonal and diurnal changes of surface soil temperature and moisture of shady and sunny slopes were recorded. Soil water content was measured during two growing seasons on both sunny and shady slopes with the same forest type at three sites located along the mean annual precipitation (MAP) gradient. Evaporation decreases with slope inclination on shady slopes, but increases with inclination on sunny slopes. The shady slope received 35% of the annual direct solar radiation received by the sunny slope when the slope inclination was 25°, and the contrast in annual direct solar radiation between the shady and sunny slopes further widens as slope inclination increases. Steeper shady slopes can support forests in dryer climates, with log-linear regression revealing a minimum slope inclination for forest distribution along the MAP gradient. The simulated minimum slope inclination for forest growth was larger than the observed minimum inclination, and the difference was greater in wetter conditions. A larger forest area fraction was considered to lead to a reduction in soil temperature and evaporation, as verified by soil temperature and moisture records and soil water content measurements. The slope-specific forest distribution in the semi-arid region of China can be explained by a topography-controlled soil water supply. Lower evaporation, resulting from lower direct solar radiation on shady slopes, allows shady slopes to retain a water supply sufficient for sustaining forests, and the existence of forests on shady slopes further reduces evaporation. Different tree species coexist at the xeric timberline due to regulation by slope inclination and aspect.  相似文献   

河西走廊荒漠绿洲过渡带封育对土壤和植被的影响   总被引：1，自引：1，他引：1  

王国华  任亦君  缑倩倩 《中国沙漠》2020,40(2):222-231

在河西走廊荒漠绿洲过渡带,封育天然植被是植被群落恢复、防止绿洲沙漠化的有效措施。以流动沙丘作为对照(0年),对封育5年和15年的半固沙和固定沙丘植被群落以及土壤进行调查取样和分析。结果表明:随着封育年限增加,天然固沙植被群落生物多样性增加,灌木层和草本层植物密度、盖度和生物量都显著增加,灌木层盖度从10%增加到40%,草本层以一年生草本植物为主,物种从5种增加到8种,生物量从1 g·m^-2增加到13 g·m^-2。随着天然植被盖度增加,土壤表层沙土细粒化明显,沙土中黏粉粒含量显著增加,土壤质地由粗质沙粒向细质沙粒转变;随着沙土中黏粉粒成分的增加,沙土有机质、全氮、全磷含量也增加,灌丛下土壤养分含量高于灌丛间,“沃岛效应”明显。同时,在灌丛下表层土壤出现明显的盐分集聚现象,其中SO₄^2-、K⁺、Na⁺含量分别增加了6、3、17倍。在降水100 mm左右的荒漠绿洲过渡带,封育可以显著恢复固沙植被群落和提高沙土质地和养分。  相似文献   

不同防护措施对梭梭幼苗生长和土壤水分的影响          下载免费PDF全文

刘璐  蒋进  宋春武 《干旱区地理》2018,41(3):564-571

在策勒绿洲-荒漠过渡带流动沙地对种植的梭梭幼苗采取了不同的处理措施（凋落物防护、固沙剂防护、防沙网防护和裸沙地,其中裸沙地作为对照）,研究不同防护措施对梭梭幼苗生长状况及地表100 cm内土壤含水率的影响,对恢复和重建绿洲-荒漠过渡带防护林体系具有重要意义。研究结果表明：（1）初春采用滴灌一次性供水135 L·m^-2,可以确保梭梭幼苗当年的生长需求。（2）不同防护措施下梭梭幼苗的株高、冠幅、基径、新枝长度均表现为：凋落物防护 > 固沙剂防护 > 防沙网防护 > 裸沙地,在生长末期凋落物防护下梭梭的株高、冠幅、基径、新枝长度分别达到115.7 cm、131.8 dm²、22.5 mm、73 cm。（3）不同防护措施对土壤含水率的影响比较明显,土壤含水率表现为：凋落物防护 > 固沙剂防护 > 防沙网防护 > 裸沙地,其中凋落物防护、固沙剂防护土壤含水率分别是裸沙地的1.31倍和1.16倍。因此,在极端干旱的绿洲-荒漠交错带,采用凋落物防护和固沙剂防护措施对提高沙地蓄水保墒能力和促进梭梭幼苗生长均有积极作用。  相似文献   

中国生态过渡带分布的空间识别及情景模拟   总被引：1，自引：1，他引：0  

范泽孟 《地理学报》2021,76(3):626-644

在全球变化及其生态环境效应研究中,如何对生态过渡带的空间分布格局及变化情景进行空间定量识别和模拟分析,对揭示气候变化和人类活动对全球变化的响应及反馈具有指示性意义。在对HLZ模型进行修正和拓展的基础上,建立了生态过渡带类型的空间识别方法。并基于1981—2010年的全国782个气候观测站点数据,在实现全国生态过渡带类型及分布的空间识别基础上,结合3种气候情景数据CMIP5 RCP 2.6、RCP 4.5和RCP 8.5,实现了T0（1981—2010年）、T1（2011—2040年）、T2（2041—2070年）和T3（2071—2100年）4个时段内全国生态过渡带的空间分布格局及其未来情景模拟。另外,引入平均中心空间分析模型,对全国生态过渡带平均中心的时空偏移趋势进行了定量分析。结果显示：在T0~T3时段内,全国共出现41种生态过渡带类型,约占全国陆地面积的18%;冷温带草原/湿润森林与暖温带干旱森林过渡带（564238.5 km²）、冷温带湿润森林与暖温带干旱/湿润森林过渡带（566549.75 m²）、北方湿润/潮湿森林与冷温带湿润森林过渡带（525750.25 km²）是最主要的3种生态过渡带类型。面积占到全国生态过渡带总面积的35%;2010—2100年期间的冷温带荒漠灌丛与暖温带荒漠灌丛/有刺草原过渡带的增加速度最快,在3种情景RCP 2.6、RCP 4.5和RCP 8.5下,其面积将分别增加3604.2 km²/10a、10063.1 km²/10a和17242 km²/10a;寒冷型生态过渡带类型总体上呈向暖湿型过渡带类型增加的趋势;北方潮湿森林与冷温带湿润/潮湿森林过渡带的平均中心偏移幅度最大,在4个时段内整体向东北方向偏移,其偏移幅度将超过150 km。另外,随着气温的逐渐上升和降水量的增加,中国北方的生态过渡带整体呈向北偏移趋势,南方生态过渡带则逐渐减少且平均中心呈现逐渐向高海拔地区退缩的趋势,气候变化对青藏高原区生态过渡带时空格局的影响日益显著。  相似文献   

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   

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   

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   

民勤绿洲边缘带灌丛沙丘防风作用研究   总被引：7，自引：1，他引：7  

王升堂  邹学勇  张春来  程宏 《地理科学》2007,27(1):104-108

对民勤天然绿洲边缘带的固定、半固定及半流动风速灌丛沙丘实地观测表明,气流通过单个固定灌丛沙丘时,近地面平均风速降低4.4%,在965 m观测样线内降低57%,且风是连续降低的,愈靠近内侧降低得愈多,到绿洲内部农田边缘处时,平均风速仅有对照点的21%。深入了解灌丛沙丘对绿洲的防护机理,对于合理保护和恢复绿洲边缘带灌丛沙丘,避免绿洲遭受风沙侵袭具有重要意义。  相似文献   

长白山岳桦苔原过渡带动态与气候变化   总被引：11，自引：0，他引：11  

周晓峰  王晓春  韩士杰  邹春静 《地学前缘》2002,9(1):227-231

应用样带网格调查方法 ,对长白山岳桦苔原过渡带上岳桦径级结构、分布格局以及过渡带的环境因子进行调查 ,并与最近几十年的极端低温进行了对比研究 ,用格局的差异和径级结构的动态变化来揭示全球变暖对岳桦苔原过渡带的影响。结果表明 :全球气候变暖对长白山岳桦苔原过渡带产生很大影响 ,气候变暖使得岳桦苔原过渡带中的岳桦分布主要以幼苗和幼树为主 ,其中岳桦的径级分布呈倒J字型 ,过渡带中岳桦种群格局呈聚集型分布。整个岳桦种群随着全球气候变暖有一种整体向上迁移的趋势 ,尤其以岳桦苔原过渡带最为明显 ,岳桦苔原过渡带变宽 ,岳桦向苔原侵入的程度加剧。  相似文献