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211.
A Water Yield‐Oriented Practical Approach for Multifunctional Forest Management and its Application in Dryland Regions of China
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Yanhui Wang Wei Xiong Stephan Gampe Neil Andrew Coles Pengtao Yu Lihong Xu Haijun Zuo Yunni Wang 《Journal of the American Water Resources Association》2015,51(3):689-703
Mountainous forest areas are vitally important for water supply in dryland regions which suffer from high erosion risk and severe water shortage. Massive afforestation, mainly for erosion control, may reduce the water yield and threaten local water supply security. Moreover, many over‐dense forests due to a strict logging ban policy have produced remarkably negative impacts for both forests (e.g., low timber quality, restricted natural regeneration, and high stand instability) and water yield. To satisfy the rapidly increasing demands on water supply and other services, a practical approach for managing forest stands in a multifunctional way, which particularly addresses water yielding, is urgently required. For this purpose, we integrated the existing knowledge and experience, designed an “ideal” stand structure to represent multifunctional forest (MFF) and determined its key parameters (a ground coverage of >0.7, a canopy density around 0.7, and an H/DBH ratio (tree height [m] to the diameter at breast height [cm]) of <0.7). Moreover, a decision process for MFF stand management was recommended as: (1) investigating the site quality; (2) identifying the site‐specific main forest functions; (3) quantifying the stand structure; (4) diagnosing the stand structure by comparing with the “ideal” one; and (5) arranging the functions/structure‐oriented management measures. In this way, the water‐yielding function can be improved and meanwhile other forest functions can be promoted. 相似文献
212.
本文利用浙江、河南、四川三省960份已从农村迁移到城镇的居民的入户调查数据,建立二元Logistic回归模型进行验证,分析居民再迁移倾向。研究结果表明:(1)从描述性统计看,69.69%已进城居民不愿再迁,主要是生活原因,而30.31%的居民愿意再迁,主要是经济原因。(2)从三省总样本上看,一是女性较男性有更强的迁移意愿。二是年龄对再次迁移意愿有负向显著影响,年龄越大的进城居民更倾向"安土重迁"。三是家庭类型中三代同堂较单身家庭有更强的迁移意愿,因为养老难、子女教育难。四是手工业工人较村组干部更不愿意迁移,技能优势使其在城里更有保障。五是家庭年总收入对再迁意愿有正向显著影响。六是浙江、四川与河南三地的差异显著,因为三地分属于我国东中西部,社会经济、居民收入和文化观念存在显著差异。(3)从分省比较上看,一是性别、打工年限、家庭类型在浙江省和四川省模型中均有显著影响,但方向相反。二是工作类型在三省都有一定的影响,但存在差异。三是家庭年总收入在河南省不显著,而在四川省和浙江省均是正向显著。四是搬迁到城镇的年数在河南省是正向显著,而在浙江省和四川省是负向显著。五是浙江省和四川省模型都说明对政府越满意,居民越不愿意迁移。基于以上研究结论,本文认为在推进以人为核心的新型城镇化进程中,政府应发挥重要的引导作用,关注已进城居民对经济、生活、教育、社会保障等方面的合理需求,重视不同区域社会经济和文化观念的差异性,健全人口迁移的相关体制,落实各项相关保障政策。 相似文献
213.
1960~2014年秦岭南北无霜期时空变化特征及对比分析 总被引:1,自引:0,他引:1
全球气候变暖背景下,自然生态环境敏感区农业热量资源的时空特征研究具有重要的现实意义。依据1960~2014年秦岭南北47个气象站数据,利用线性趋势、M-K检验和kriging插值法对无霜期时空变化进行分析。结果显示:从时间上看,秦岭南北无霜期随纬度增加而减少,初霜日和无霜期在年际波动中略有下降后快速上升,终霜日在波动中略有上升后快速下降。55年来无霜期呈显著的延长趋势且发生增多突变,秦岭以北、秦岭南坡、汉水流域和巴巫谷地的延长速率分别为0.400 6、0.280 4、0.396 1和0.407 5 d/a,突变年份分别为1999、2002、2001和1990年。从空间上看,无霜期平均值和标准差由南向北增加,80%站点初霜日推后、终霜日提前和无霜期延长。多数无霜期延长是初霜日推后与终霜日提前的共同影响。无霜期在28个站点呈波动变化,19个站点发生突变,突变时间多在1990s~2000s,2000s的突变区域面积最大且集中分布在东北部。分析结果可为气候变化对生态环境和农业生产布局的影响提供参考。 相似文献
214.
Yang Ding Huanfang Huang Wei Chen Yuan Zhang Wenwen Chen Xinli Xing Shihua Qi 《环境科学学报(英文版)》2022,34(5):453-464
Long-range atmospheric transport(LRAT) plays a crucial role in the occurrence of persistent organic pollutants(POPs) in remote regions. When studying the LRAT of POPs on the Tibetan Plateau, westerly-controlled regions have received insufficient attention compared with regions influenced by the Indian monsoon or air flow from East Asia. We investigated the residual levels of POPs in soils from the eastern Pamirs and used air backward trajectory analysis to elucidate the influence of potential so... 相似文献
215.
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217.
Trace element contamination in industrial regions of Poland studied by moss monitoring 总被引:2,自引:0,他引:2
Grodzińska K Frontasyeva M Szarek-Lukaszewska G Klich M Kucharska-Fabiś A Gundorina SF Ostrovnaya TM 《Environmental monitoring and assessment》2003,87(3):255-270
The use of terrestrial mosses as biomonitors in large-scalemulti-element studies of heavy metal deposition from theatmosphere is a well established technique in Europe. Insuch studies it is advantageous to determine as many elements as possible in order to distinguish betweendifferent source categories. A combination of INAA and AAShas been found very useful in this respect, in particularwhen epithermal activation is used for instrumental neutronactivation analysis. A total of 33 elements (Al, Cl, Sc, V,Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Sb,I, Cs, Ba, La, Ce, Tb, Yb, Hf, Ta, W, Au, Pb, Th, and U) inPleurozium schreberi (Brid.) Mitt. moss samples fromthe Silesia-Kraków Industrial Region and Legnica-GogówCopper Basin and from the control (background) area inNortheast Poland were identified. The highest concentrationsof the majority of trace elements were found in mossesgrowing in the Silesia-Kraków Industrial Region, only Cu andAs concentrations were higher in mosses in the Legnica-Gogów Copper Basin. These results are in conformity withthe load of trace elements emissions in these areas. 相似文献
218.
Spatial Patterns of Soil Moisture as Affected by Shrubs, in Different Climatic Conditions 总被引:8,自引:0,他引:8
Pariente S 《Environmental monitoring and assessment》2002,73(3):237-251
At three study sites, representing Mediterranean, semi-aridand mildly-arid climatic conditions, the effect of shrubs onthe spatial patterns of soil moisture was studied. At eachsite soil moisture was measured, on hillslopes, at thevicinity of 8 shrubs. For each shrub the measurements havebeen taken at 3 microenvironments, i.e. under the shrub (US),at the margins of shrub (MS) and between shrubs (BS). At themicroenvironments US and MS the measurements were taken at 3 directions: upslope, downslope and sideslope of the shrubs. At all sampling points soil samples were taken from 3 depths: 0–2, 2–5 and 5–10 cm. In addition, rock fragments cover percentage near the shrubs was determined. A soil moisture pattern was found, around each shrub,which is composed of a radial gradient and a downslope gradient. The radial gradient is expressed by soil moisture decreasingfrom the US microenvironment, in all directions, through the MS towards the BS microenvironment. The US microenvironmenthas a `spatial advantage' of higher soil moisture content dueto (1) relatively higher infiltration rate, (2) capture overlandflow from the BS area upslope that shrub and (3) low evaporationrate because of the shading effect.The downslope gradient is expressed by decreasing soil moisturefrom the upslope direction of each shrub (MS and US microenvironments) towards the downslope direction of that shrub (MS and US microenvironments, respectively). Thisgradient is controlled by the relatively high content of rockfragments near the shrubs at their upslope direction. Suchrock fragments spatial distribution is attributed to (1) thedetachment and transport of rock fragments by sheep and goatstrampling and (2) the effect of shrub on the continuity ofoverland flow and sediment transport. The effect of rockfragments is similar to that of shrubs regarding increasinginfiltration and decreasing evaporation rate. The relativelyhigh soil moisture at the upslope direction of each shrubenhances annuals growth producing a positive feedback loop:soil moisture – annuals growth – trampling. This sequencemaintains the typical rock fragments spatial organization andcontributes to the sustainability of the grazing system.At all the study sites at the US microenvironment there isa trend of decreasing soil moisture with increasing soildepth. At microenvironments MS and BS soil moisture increaseswith soil depth.The results are of great relevance for rehabilitationstrategies as they suggest that in order to combatdesertification in degraded semi-arid and mildly-arid areas,where the main land use is grazing, both shrubs and rockfragment should be kept at their present spatial distribution. 相似文献
219.
中国水灾风险综合管理--平衡大都市区水灾致灾强度与脆弱性 总被引:8,自引:2,他引:8
中国大都市区主要分布在大江大河的中下游地区,由于区域土地利用格局的巨大变化,特别是较多的水域和湿地因城市化而被占据,因此,一方面大都市区面临严重的洪水危险,另一方面为了使大都市区尽可能减轻洪水灾害,而加强了防洪能力的建设.然而,近50年的减灾实践证明,洪水灾害却在波动中趋于上升,即大都市区对洪水的脆弱性在增大.在对中国大都市区洪水灾害的区域分析基础上,以广东省为例,构造了综合水灾致灾因子和承灾体为一体的风险评估模型体系,以此提出了平衡大都市区水灾致灾强度与脆弱性的基本土地利用模式,和"政府-企业(社区)-保险公司"相结合的企业风险管理模式. 相似文献
220.
During the last 30 years, growing demand for science-based policy making has contributed to the mobilization of scientific cooperation alongside transnational political arrangements for addressing environmental issues. Following the contemporary trend toward regionalizing environmental policy and practice, many of these scientific joint efforts have focused on a regional scale. This article examines regional scientific cooperation in the context of the institutionalization of mountain regions in Europe. Such cooperation can be observed from the Pyrenees to Central Asia, albeit with a degree of variation that largely remains unexplored in scientific research. Sometimes scientific cooperation served to lay the groundwork of a mountain policy initiative, other times it appeared in its wake; some examples appear as loose networks of individual scientists, others are set up as formalized monitoring and observation centers; finally, some scientific joint efforts are formally linked to, or incorporated in a mountain policy initiative, while others are largely independent. The article proposes a new typology for understanding the interactions between regional scientific mobilization and regional policy making and provides up-to-date portraits of six main cases. 相似文献