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71.
Participatory selection process for indicators of rangeland condition in the Kalahari 总被引:2,自引:0,他引:2
To develop indicator–based management tools that can facilitate sustainable natural resource management by non–specialists, meaningful participation of stakeholders is essential. A participatory framework is proposed for the identification, evaluation and selection of rangeland condition indicators. This framework is applied to the assessment of rangeland degradation processes and sustainable natural resource management with pastoralists in the southern Kalahari, Botswana. Farmer knowledge focused on vegetation and livestock, with soil, wild animal and socio–economic indicators playing a lesser role. Most were indicators of current rangeland condition; however 'early warning' indicators were also identified by some key informants. This demonstrates that some local knowledge is process–based. Such knowledge could be used to improve indicator–based management tools and extension advice on the livelihood adaptations necessary to prevent or reduce ecological change, capable of threatening livelihood sustainability. There is evidence that social background influences indicator use. Communal farmers rely most heavily on vegetation and livestock indicators, whilst syndicate and land–owning pastoralists cite wild animal and soil–based indicators most frequently. These factors must be considered if indicator–based management tools are to meet the requirements of a diverse community. 相似文献
72.
川西北高原若尔盖草地沙化及湿地萎缩动态遥感监测 总被引:61,自引:2,他引:61
应用卫星遥感资料(MSS、TM及spot)对川西北高原若尔盖草地沙化及湿地萎缩的动态监测发现,自1966年至2000年的34年间,草地沙化面积增加307.7%,达到36760.9hm^2,占区域总面积的7.25%,平均每年扩大草地沙化面积816.0hm^2,年均递增率达4.22%。到2000年止,区域内有沙地5083.9hm^2,沙化草地31677.0hm^2。自1985~2000年的15a间,区内17个湖泊面积缩小842.0hm^2,减幅达38.9%,平均每年减少56.1hm^2,年均递减速度达3.34%,该区目前其余11个湖泊总面积仅为1323.1hm^2,只有15年前的61.1%。 相似文献
73.
Seasonal variation of the soil seed bank of grasses in central Argentina as related to grazing and shrub cover 总被引:1,自引:0,他引:1
The objectives of this research were to (a) study seasonal variation of the seed bank of grasses in two areas with different grazing history, (b) analyse the effect of the presence of shrubs on the seed bank and (c) study seed viability and dormancy in buried seeds of Piptochaetium napostaense and Stipa tenuis. The seed density of grasses was in general low and showed seasonal variation. Most of the grasses showed maximum seed density in December when seed dispersal occurs. Shrub cover did not show a marked influence in seed accumulation. The relatively high number of damaged seeds suggests that predation may be an important factor in seed bank dynamics in the Caldenal. Seeds of dominant perennial forage grasses showed dormancy that could explain, at least in part, persistence of these species in spite of periodical disturbance. 相似文献
74.
灰色系统理论预测大气氮氧化物污染的应用 总被引:11,自引:0,他引:11
根据中国南方某省所辖城市近年来N0x污染指数的测量数据的统计资料,建立了GM(1,1)灰色预测模型,通过预测探讨了大气中氮氧化物指数的变化趋势。所建模型残差仅1.17%,关联系数为0.9067,精度较高,具有较好的可行性和适应性,可以为管理规则提供决策依据。 相似文献
75.
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77.
水化学指标表示裘布依公式的应用 总被引:2,自引:0,他引:2
侯玉新 《水文地质工程地质》2003,30(4):97-101
从多矿物溶解化学动力学方程出发,推演并建立了由水化学指标表示的承压二维井流裘布依公式。结合水文地质、水文地球化学特征,列举了水文地质单元内不同区带、各种代表性矿物及相应组分化学指标的基本表达式。以山西省太原西峪煤矿所需解决的水文地质问题为例进行了定量研究与评价,其结果与已有的抽水试验资料接近,为矿井涌水量的评价开辟了一条新的道路。从事实上进一步论证了水化学指标表示裘布依公式的理论概括是正确的。 相似文献
78.
A Bayesian inference approach is introduced to identify soil degradation behaviours at four downhole array sites. The approach of inference is based on a parametric time‐varying infinite impulse response filter model. The approach is shown to be adaptive to the changes of filter parameters and noise amplitudes. Four sites, including the Lotung (Taiwan), Chiba (Japan), Garner Valley (California), and Treasure Island (California) sites with downhole seismic arrays are analysed. Our results show two major types of soil degradation behaviour: the well‐known strain‐dependent softening, and reduction in stiffness that is not instantaneously recoverable. It is also found that both types of soil degradation are more pronounced in sandy soils than in clayey soils. The mechanism for the second type of soil degradation is not yet clear to the authors and suggested to be further studied. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
79.
冻土路基表面的融化指数与冻结指数 总被引:21,自引:6,他引:21
在冻土层之上筑路,由于会改变地-气界面的热物理特性,进而影响冻土层的热力→动力稳定性,故而修筑一定高度的路基成为保护冻土层所采取的一种常规措施.在修筑路基之后,与路基边坡的朝向有关的热效应是冻土路基工程保护措施必须考虑的问题.在数理分析与数值模拟分析的基础上,给出了可根据气温的年最大和最小月平均值计算路基表面的融化指数与冻结指数以及有关热状况参数的方法,并以青藏铁路北麓河段2002年为例进行了计算分析.实例分析表明,即便是没有修筑道路,北麓河地区的冻土也已经处于临界状态;路基相对的两个坡面,由于朝向不同会造成温度分布的强非均匀性,其中南和偏南方向与北和偏北方向的路基坡面热状况差异最大,有必要对路基相对的两个坡面采用不同的防护措施,一方面改善就地取土修筑路基对其下伏冻土层的直接不良影响,同时也尽可能减小路基表面温度分布的非均匀性,以避免纵向裂缝的发生。 相似文献
80.
The colonization of periphytic diatom species on artificial substrates in the Ashar canal, Basrah, Iraq 总被引:1,自引:0,他引:1
H.A. Hameed 《Limnologica》2003,33(1):54-61
Studies have been conducted between March 1993 and March 1994 in the Ashar canal, a backwater of the Shatt al-Arab River, Iraq. Using artificial substrates, the colonization and development of seventy-five diatom species belonging to twenty genera could be revealed. Taxa apportionment varied seasonally as well as within each season. A few species have been found during all experiments. These are Amphora ovalis, Bacillaria paradoxa, Cocconeis placentula var. euglypta, Cyclotella meneghiniana, Cymbella ventricosa, Navicula tripunctata var. schizonemoides, Rhoicosphenia curvata, and Synedra ulna. The occurrence of B. paradoxa in Experiment 1 (March-April 1993) and Experiment 4 (end of January to beginning of March 1994) was higher than 50%. Similarity of species increased towards the end of each season, and the communities from experiments 1 and 4 were more similar than others. The experiments also suggest that week 4 represents the equilibrium phase while week 6 reflects the increase in biological interactions. The results could also indicate the sequence of primary colonizers and the community development towards the equilibrium. 相似文献