生态地理区域界线划分的指标体系

生态地理区域界线由一系列反映生态地理区域特征的指标为依据 ,通过其空间差异落实到具体的空间位置上。客观地认识和划定生态地理区域界线是揭示生态环境时空有序性的重要途径 ,是地域系统研究的基础。生态地理区域界线是两个相邻的、彼此不同的生态地理区质上转变的线或带 ,反映同一等级内划分出来的内部相对一致性与外部的差异性。界线代表有一定宽度的带 ,而且可能随着时间而迁移变化 ,等级越低界线越明显 ,等级越高界线越宽。在生态地理区域划分中 ,先选择人力不能大规模改变的几个主要因素 :温度指标 ,主要指标是日平均气温≥ 1 0℃的天数和积温 ,最冷月平均气温 ,最暖月平均气温等 ;水分指标 ,干湿指数 ,目前比较普遍采用的是年干燥度 ,它可以近似地表征某一地方的干湿程度 ;年降水量的资料通常比较可靠 ,但潜在蒸发的计算需要改进和提高。生态地理区域较高级单位的划分依据侧重考虑生物气候的差异 ,先注意水平地带性 ,由于气候台站的有限性 ,所划分出的界线往往用植被界线去修正 ;而垂直地带性则将潜在植被与气候联系起来 ,按照降水量、潜在蒸发率和生物温度来进行划分。如何处理级别与依据和指标之间的关系是另一个重要问题 ,在这个问题的处理上 ,国内外很不统一。     

Transformation of parabolic dunes into mobile barchans triggered by environmental change and anthropogenic disturbance

Parabolic dunes are widely distributed on coasts and margins of deserts and steppes where ecosystems are vulnerable and sensitive to environmental changes and human disturbances. Some studies have indicated that vegetated parabolic dunes can be activated into highly mobile barchan dunes and the catastrophic shift of eco‐geomorphic systems is detrimental to land management and social‐economic development; however, no detailed study has clarified the physical processes and eco‐geomorphic interactions that control the stability of a parabolic dune and its resistance to unfavorable environmental changes. This study utilizes the Extended‐DECAL (Discrete Eco‐geomorphic Aeolian Landscapes) model, parameterized by field measurements of dune topography and vegetation characteristics combined with remote sensing, to explore how increases in drought stress, wind strength, and grazing stress may lead to the activation of stabilizing parabolic dunes into highly mobile barchans. The modeling results suggest that the mobility of an initial parabolic dune at the onset of a perturbation determines the capacity of a system to absorb environmental change, and a slight increase in vegetation cover of an initial parabolic dune can increase the activation threshold significantly. The characteristics of four eco‐geomorphic interaction zones control the processes and resulting morphologies of the transformations. A higher deposition tolerance of vegetation increases the activation threshold of the dune transformation under both a negative climatic impact and an increased sand transport rate, whereas the erosion tolerance of vegetation influences the patterns of resulting barchans (a single barchan versus multiple barchans). The change in the characteristics of eco‐geomorphic interaction zones may indirectly reflect the dune stability and predict an ongoing transformation, whilst the activation angle may be potentially used as a proxy of environmental stresses. In contrast to the natural environmental changes that tend to affect relatively weak and young plants, grazing stress can exert a broader impact on any plant indistinctively. A small increase in grazing stress just above the activation threshold can accelerate dune activation significantly. Copyright © 2017 John Wiley & Sons, Ltd.     

Eco‐physiological repercussions of dietary arachidonic acid in cell membranes of active tissues of the Gray whale

The radiation of the mammalian land species that became the baleen whales happened about 27–34 Mya. Mammals require omega 6 fatty acids for reproduction. With this long exposure to the omega 3‐rich marine food chain, the Gray whale (Eschrichtius robustus) might be expected to have lost its requirement for omega 6 fatty acids. We report an unexpectedly high content of omega 6 arachidonic acid (ArA) in the Gray whale liver and muscle lipids. This whale migrates 10,000 km from the cold polar, omega 3 oil‐rich food chain to that of the breeding lagoons of the tropical waters. The food web of tropical waters is a source of omega 6 fatty acids, which are hardly present in the cold polar food web. We suggest the reason for this longest of migrations from cold to warm waters is to meet the requirement for omega 6 fatty acids for mammalian reproduction and brain growth. This extreme conservation of omega 6 fatty acids in Gray whale biology has critical implications for mammalian biology and especially for whale conservation.     

黄土高原生态脆弱贫困区生态经济发展模式研究——以甘肃省定西地区为例

本文对黄土高原丘陵沟壑区定西地区生态脆弱与贫困的双重矛盾进行了定性与定量相结合的分析,研究表明定西地区“脆弱-贫困”恶性循环是自然与人文要素长期作用的结果,近几十年又以人为因素的作用为主。在总结定西地区解放以来一手抓生态环境建设,一手抓扶贫攻坚,整体解决温饱的成功经验基础上,提出了黄土高原生态脆弱的贫困地区生态经济发展模式;实践证明,生态经济发展模式是黄土高原生态脆弱的贫困地区打破“脆弱-贫困”恶性循环,实现可持续发展的必由之路     

基于GIS的福建农业生态环境区域分异

本文应用地理信息系统所具有的巨大数据综合处理、空间分析和模型运算等技术优势 ,评价与分析福建农业生态环境中的土壤侵蚀、土壤污染、土壤养分贫瘠和功能稳定性等重要问题 ,提出区域特征的空间分布.     

陕北地区生态环境建设与水资源合理开发利用问题研究

在论述陕北地区自然地理、地质地貌特征基础上，分析研究了陕北地区在经济建设中突出的生态环境问题，论证了生态环境与水资源之间的关系。根据陕北地区自然地理特征，提出了生态环境建设的方向和措施，以及水资源合理开发利用的建议。     

广饶县蔬菜基地生态地质环境研究

为了解广饶县蔬菜基地生态地质环境质量,通过对水、土环境质量现状进行调查,重点研究了四大蔬菜基地的生态地质环境特征,结果表明四大蔬菜基地生态环境质量相对较好,蔬菜质量也达到无公害标准。发现在花官乡及稻庄镇存在土壤硒元素富集区,大蒜及芹菜中硒元素含量也较高,对引导当地绿色高效生态农业发展具有重大意义。     

桂林岩溶峰丛区定域时空变化研究

为探索局域生态环境变化对桂林市整体生态环境状态的影响,选择漓江沿岸北从刘村南至街底共8个峰丛地貌区作为研究对象(编号为No.1~No.8),并以1986、1991和2006年3个时相的Landsat-5卫星影像的TM数据为信息源,采用基于ROI的定域定量遥感技术,结合地理与岩溶地质学资料,对这8个岩溶峰丛区的遥感生境指标即归一化植被指数NDVI和缨帽变换中的绿度分量TC2作定域提取和纵、横向分析(时间和空间变化分析)。研究表明,2006年岩溶峰丛区的NDVI和TC2最高,生态环境最好,1986年次之,1991年最差,表明在20世纪80年代末90年代初这一阶段里,由于桂林市经济高速发展而忽视环保,岩溶峰丛区的生境曾受到较不良影响,但进入本世纪以来已经得到了明显改善;在空间上各峰丛区NDVI大于4.0和TC2大于20的地块呈现斑状或条带状分布,且自1991年以来有向全区扩大的趋势。同一区域不同时间NDVI和TC2变化具有1991年低,1986年、2006年高的趋势,而同一时间不同区域NDVI和TC2也存在着差异,由好到差其关系为:No.5>No.4>No.3>No.8>No.7>No.6>No.2>No.1。      

Hydrological response of abandoned agricultural soils along a climatological gradient on metamorphic parent material in southern Spain

The hydrological and erosive response of the Mediterranean eco‐geomorphologic system has showed a very variable and complex behaviour depending on several factors: topography, geology, vegetation pattern, soil properties, land use management, etc. Climate is a key factor due to the great spatial and temporal variability. This research was carried out over different micro‐environments representative from five hillslopes localized in the Littoral Bethic Mountains in the south of Spain. The results of 20 experiments with rainfall simulations on micro‐plots (0.24 m²) and the differences of the incidence of some biotic and abiotic factors in the eco‐geomorphologic system from semi‐arid, dry‐Mediterranean and sub‐humid sites are exposed. Runoff, soil moisture and sediment were measured before, during and after the experiments. The results have shown rock fragments disposition on soil surface and vegetation seem to be the main factors that control the hydrological and erosive response at the micro‐plot‐scale of the experiments. Embedded rock fragments are the most important soil surface property because they reduce the infiltration. Whilst vegetation increases it what is more influential on the hydrological and erosive response of micro‐environments at more arid sites. We have also observed that there are micro‐environment particularities which play a more important role than the localization in the climatic gradient at micro‐plot scale. Copyright © 2009 John Wiley & Sons, Ltd.     

Topographic thresholds for plant colonization on semi‐arid eroded slopes

Soil erosion plays an important role in plant colonization of semi‐arid degraded areas. In this study, we aimed at deepening our knowledge of the mechanisms that control plant colonization on semi‐arid eroded slopes in east Spain by (i) determining topographic thresholds for plant colonization, (ii) identifying the soil properties limiting plant establishment and (iii) assessing whether colonizing species have specific plant traits to cope with these limitations. Slope angle and aspect were surrogates of erosion rate and water availability, respectively. Since soil erosion and water availability can limit plant establishment and both can interact in the landscape, we analysed variations in colonization success (vegetation cover and species number) with slope angle on 156 slopes, as a function of slope aspect. After determining slope angle thresholds for plant colonization, soil was sampled near the threshold values for soil analysis [nitrogen, phosphorous, calcium carbonate (CaCO₃), water holding capacity]. Plant traits expressing the plant colonizing capacity were analysed both in the pool of species colonizing the steep slopes just below the threshold and in the pool of species inhabiting gentler slopes and absent from the slopes just below the threshold. Results show that the slope angle threshold for plant colonization decreased from north to south. For the vegetation cover, threshold values were 63°, 50°, 46°, 41° for the north, east, west and south slope aspect classes, respectively, and 65°, 53°, 49° and 45° for the species richness and the same aspect classes. No differences existed in soil properties at slope angle threshold values among slope aspects and between slope positions (just below and above the threshold) within slope aspect classes. This suggests that variations between slope aspect classes in the slope angle threshold result from differences in the colonizing capacity of plants which is controlled by water availability. Long‐distance dispersal and mucilage production were preferably associated with the pool of colonizing species. These results are discussed in the perspective of a more efficient ecological restoration of degraded semi‐arid ecosystems where soil erosion acts as an ecological filter for plant establishment. Copyright © 2009 John Wiley & Sons, Ltd.