THE POSSIBILITIES AND REALITIES ON THE REMANAGEMENT OF DESERTIFIED LANDS IN THE TRANSITIONAL ZONE BETWEEN THE DRY-FARMING AREA AND THE GRAZING AREA IN NORTH CHINA

The desertification process is rapidly developing at present and 61.5% of the land area in the zone are already desertified.Among the desertified lands, 26.9% are seriously desertified, 25% most seriously desertified and 47.4% are the lands where desertification is under way. They are caused by over-reclamation for farming, over-grazing, unreasonable collection of firewood,the destruction of vegetation and the misuse of water resources. Under the ecological environment in semi-arid zone,the degraded environment process possesses the ability of restoring to its original status as soon as the interruption of excessive human activities are eliminated. The fencing- and-self-cultivating method is an effective measure adopted universally in semi-arid zone to cure the desertified lands.The desertified lands can be readjusted and controlled easily if other controlling measures are supplemented. The fundamental ways to control desertification are to utilize rationally the resources, to readjust the existing land     

A thousand years of environmental change and human impact in the alpine zone at Mt Kosciusko,New South Wales

This study reconstructs erosion, productivity, fire and vegetation records at Club Lake, in the alpine zone of Kosciusko National Park (the highest mountain region in Australia), and uses them to compare the prehistoric and historic periods. While disturbance in the prehistoric period was found to be minimal and mainly activated by fire, the impact of land uses after European arrival initiated a change in the erosion and fire regime and brought new grazing animals and exotic plant species. These triggered temporal changes in eutrophication and the nature of erosion, and significant vegetation changes. There was a reduction in the stability and persistence of species representation, especially in herbfield vegetation, and little recovery is evident despite the cessation of summer grazing. It is apparent that the area is very sensitive to disturbance by human impact and large fires.     

台湾海峡南部夏季微型浮游动物对浮游植物的摄食压力及其生产力

2004年7~8月在台湾海峡南部的5个站位,用稀释法研究了浮游植物的生长率,微型浮游动物对浮游植物的摄食率及其生产力.微型浮游动物主要为无壳纤毛虫,尤其是急游虫类和侠盗虫类.浮游植物的生长率为0.52~0.72/d,浮游动物的摄食率为0.45~1.33/d,相当于每天摄食浮游植物现存量的36%~74%和初级生产力的88%~141%.微型浮游动物的次级生产力(MP02)为初级生产力的28.5%~58.4%.表明微型浮游动物在台湾海峡夏季海洋生态系统的能量流动中发挥着重要的作用.     

Influence of cattle grazing on population density and species richness of granivorous birds (Emberizidae) in the arid plain of the Monte, Argentina

Cattle grazing is an important disturbance in the Monte plain, reducing grass biomass and rates of fruit setting. Grass seeds are the most important food for granivorous birds (Emberizidae) during winter. The objective of this study was to test whether granivorous bird populations (Emberizidae), grass seed production, and vegetation structure differed at sites with different intensities of grazing. Emberizid density and species richness were higher in the ungrazed site than in the two grazed paddocks. Seed abundance was also higher in ungrazed vs. grazed sites. Woody vegetation, that serve as safe nest sites, did not differ among treatments. Granivorous bird populations seemed to be affected by cattle grazing; however, the main mechanisms of this process remain unknown.     

In-situ studies of microzooplankton grazing pressure on phytoplankton in Jiaozhou Bay, China

Preliminary studies on microzooplankton grazing were conducted with dilution method in Jiaozhou Bay from summer 1998 to spring 1999. Four experiments were carried out at St. 5 located at the center of Jiaozhou Bay. Chlorophyll a concentrations were consistently dominated by netphytoplankton (net-, >20μm), except during the autumn 1998 cruise, when they were dominated by nanophytoplankton(nano-, 2–20μm). The contribution of picophytoplankton (pico-, <2μm) to total chlorophyll a concentrations (<200μm) varied considerably between cruises. Instantaneous growth coefficients(u) of phytoplankton varied from 0.098 to 1.947d⁻¹, with mean value of 0.902d⁻¹. Instantaneous coefficients(g) of microzooplankton grazing on phytoplankton ranged from 0.066 to 0.567d⁻¹, mean value of 0.265d⁻¹, which was equivalent to daily lose of 21.9% of the initial standing stock and 58.1% of the daily potential production. Project No KZCX3-SW-214 supported by Chinese Academy of Sciences.     

Social and ecological constraints on decision making by transhumant pastoralists: a case study from the Moroccan Atlas Mountains

Transhumant pastoralism is an important activity in southern Morocco. Migration pattern of transhumant pastoralists can be affected by physical factors (e.g. droughts and diseases) or socioeconomic factors (e.g. schooling options for children and migration costs). We studied the spatio-temporal rangeland usage of the three tribes Ait Mgoun, Ait Zekri, and Ait Toumert in the south-central Atlas region with a two-fold approach. First, we tracked the migration movements of one representative transhumant herd using the Advanced Research and Global Observation Satellite (ARGOS) collars, which record coordinates from satellite signals. Second, we interviewed herders to obtain information about general grazing practices of the respective tribe and to gain more direct information on motivations underlying decisions. For each tribe we observed small-, medium- and large-scale movements. We found that the most important drivers of migration decisions were seasonal fodder availability and weather conditions in combination with herd-specific risk and cost assessment, as well as personal factors. In conclusion, general migration patterns vary in time, both between and within the tribes, but according to a regulatory framework. Moreover, it appears that both the customary rules and its flexible adaptation to physical constraints are generally beneficial in terms of conservation of the arid and semiarid rangeland resources.     

大兴安岭东坡新林林区冻土变化特征

大兴安岭处于欧亚大陆多年冻土带南缘, 其多年冻土形成、 发展和保存更多受制于植被、 水分等局地因子的影响。采用钻探、 探地雷达和冻土温度长期监测等手段研究发现, 放牧活动会影响大兴安岭东坡新林林区活动层厚度, 放牧活动比较强烈的地段, 活动层可达2.5 m, 放牧区边缘至未放牧区域, 活动层缩减至1.5 m。塔头2013年11月2.0 m处的地温仍然在0 ℃以上（0.04 ℃）, 当放牧行为终止及加漠公路改道后, 2.0 m处的温度开始逐渐恢复, 温度由-0.12 ℃降到-0.69 ℃, 1.5 m处的温度则由0.17 ℃降到-0.42 ℃, 2018年底塔头的活动层厚度已经小于1.5 m。从地表植被类型上看, 松树林、 塔头和灌丛的活动层多年平均厚度分别为0.8 m、 1.3 m和0.7 m, 近地表0.5 m处的年平均地温为0.07 ℃、 0.52 ℃和0.22 ℃, 年变化深度处（11 m）的年均温度为-1.34 ℃, -0.98 ℃和-2.19 ℃。从地温曲线类型上看, 灌丛下的多年冻土比较稳定, 地温曲线属于正梯度型。松树林和塔头下的冻土温度比较复杂, 松树林地温曲线为偏负梯度型-零梯度型-偏正梯度型, 塔头为负梯度型-扭曲型。在地表植被类型和人类活动的共同影响下, 研究区多年冻土经历了地表干扰开始退化、 干扰消除不再退化以及慢慢恢复的过程。     

Alpine Ecosystems of Northwest Yunnan, China： an Initial Assessment for Conservation

Implementing conservation actions on-the-ground is not a straightforward process,especially when faced with high scientific uncertainty due to limited available information. This is especially acute in regions of the world that harbor many unique species that have not been well studied,such as the alpine zone of the Hengduan Mountains of Northwest Yunnan (NWY),a global biodiversity hotspot and site of The Nature Conservancy’s Yunnan Great Rivers Project. We conducted a quantitative,but rapid regional-level assessment of the alpine flora across NWY to provide a broad-based understanding of local and regional patterns of the alpine flora,the first large-scale analysis of alpine biodiversity patterns in this region. Multivariate analyses were used to classify the major plant community types and link community patterns to habitat variables. Our analysis indicated that most species had small distributions and/or small population sizes. Strong patterns emerged with higher diversity in the more northern mountains,but beta diversity was high,averaging only 10% among sites. The ordinations indicated that elevation and geographic location were the dominant environ-mental gradients underlying the differences in the species composition among communities. The high beta diversity across the alpine of these mountains implies that conservation strategies ultimately will require the protection of large numbers of species over a large geographical area. However,prioritiza-tion should be given to areas where potential payoffs are greatest. Sites with high species richness also have a greater number of endemic species,and,by focusing efforts on these sites,conservation investments would be maximized by protecting the greatest number of unique species.     

Experimental studies on the role of planktivorous fishes in the elimination ofMicrocystis bloom from Donghu Lake using enclosure method

The hypertrophic subtropic Donghu Lake's dense water bloom (of mainlyMicrocystis, Anabaena andOscillatoria) that occurred annually from the beginning of the 1970s, has disappeared since 1985. The influence of planktivorous fishes (silver and bighead carps) on the water bloom was studied for three years using the enclosure method. The enclosures stocked densely with bighead and/or silver carp were free of water bloom during the experimental period. The water bloom that appeared in the fish-free enclosures was completely eliminated in 10–20 days by introduction of silver and/or bighead carp(grass carp was not effective in controlling water bloom). This study showed clearly that grazing pressure by planktivorous fishes is a key factor in eliminating water bloom from the lake. This work was supported by FEBL (State Key Laboratory for Freshwater Ecology and Biotechnology of China) funds and by the National Natural Science Foundation of China (Grant No., 3937014).