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141.
Clements A 《Environmental monitoring and assessment》2004,99(1-3):233-243
Desertification of shrub and grassland into pinyon-juniper woodland is occurring over much of the Colorado Plateau in the
southwestern United States. As trees invade, they out-compete shrubs and grasses, increasing erosion rates and reducing infiltration
of moisture into the soil. This has caused habitat problems for wildlife, and reduced forage for livestock. These impacts
also affect the human communities that rely on ranching and tourism related to hunting. Past land use and management practices
including heavy livestock grazing, fire suppression and introduction of exotic annual plants are believed to have led to current
conditions. The Montrose office of the Bureau of Land Management has implemented an ecosystem-based program to reverse the
desertification process on public land. The program is centered on detailed landscape objectives describing the desired vegetation
mosaic on 360 000 ha of public land. The objectives outline proportions of plant seral stages and arrays of patch sizes for
each planning unit. These objectives are based on priority management issues and the need to replicate a natural vegetation
mosaic. Where the existing mosaic does not meet objectives, mechanical vegetation treatments and prescribed fire are used
to create early and mid-seral patches on the ground. This restored vegetation pattern and type should be sustained over time
through a natural fire regime and improved livestock management. Because many uncertainties exist, an adaptive management
process is being used that allows mosaic objectives to be changed or processes modified where monitoring or scientific research
indicate a need. 相似文献
142.
温室盆栽试验表明,冬作季节土壤持续淹水处理(淹水)稻田平均CH4 排放通量显著高于干燥处理(干燥),前者是后者的5.58 倍(1996 年)和4.16 倍(1997 年)。冬作季节土壤水分状况明显影响土壤Eh 和CH4 排放的季节变化。淹水处理土壤Eh 在整个水稻生长期皆处于适宜CH4 产生的水平,所以整个水稻生长期皆有CH4 排放(经历烤田后例外),而干燥处理水稻移栽42 d 后土壤Eh 才降为负值,在此期间几乎没有CH4 排放。 相似文献
143.
了解高寒沼泽植物群落与环境因子之间的关系,对揭示物种对生态环境的需求以及高寒沼泽的保护管理有重要意义,然而目前尚不清楚影响若尔盖高寒沼泽植物分布的主要环境因素。作者于2011—2012年间在若尔盖高寒沼泽随机调查32个样地,收集了植被样方数据、土壤理化性质数据、地表水位等实测数据,借助方差分析、CCA分析和相关分析等经典的统计方法,研究高寒沼泽植物群落物种组成和不同地表积水状况下多样性的差异,以及高寒沼泽植物群落与环境因子的关系。结果显示:若尔盖高寒沼泽植物共有151个种,隶属于39科98属;多样性指数随地表积水的减少呈现出增加的趋势。典范对应分析(CCA)结果表明,第一轴与水位、土壤水分含量、土壤有机碳、土壤总氮显著负相关,与土壤容重显著正相关,第二轴与裸斑率和鼠洞数显著相关。前2个轴一共解释了79.8%的物种与环境因子的关系,与环境因子的相关系数均在0.87以上;其中,水分和土壤养分条件是影响物种分布的主导因子,其次是裸斑面及啮齿动物活动。植物多样性指数与土壤水分负相关,与土壤有机碳和土壤全氮显著负相关,与土壤容重显著正相关。若尔盖沼泽植物群落物种多样性除了受土壤水分和养分条件的影响以外,啮齿动物的活动可能是影响若尔盖沼泽物种分布以及促进群落进一步演替的主要因素之一。 相似文献
144.
三峡水库运行对洞庭湖北部地区水资源开发利用的影响 总被引:2,自引:0,他引:2
依据实测原型水文序列,在辨析三峡水库运行与四水流域水利工程运行对江湖水文关系演变特征影响的基础上,重点剖析了三峡水库运行对洞庭湖北部地区水资源开发利用的影响。结果表明:①在江湖水文关系演变过程中,三峡水库运行对洞庭湖水情演变的影响要大于四水水利工程运行的影响;②洞庭湖区水资源比三峡水库运行前(1951—2002年)类似来水情景下减少了185.60×108 m3;③三峡水库蓄水调度运行期,枯水年、丰水年9月15日至10月31日荆南三口入湖平均径流依次减少67.99×108、23.14×108 m3,补水运行期枯水年、丰水年1—3月三口入湖平均径流依次减少4.93×108、11.51×108 m3;④三峡水库运行对洞庭湖区水资源开发利用影响的地区是澧县、安乡县、沅江市、南县、华容县等县市,影响时间为每年10—12月或1—3月,影响的后果是因季节性和工程性缺水造成该区平均每年经济损失约57 359×104元。 相似文献
145.
146.
Neubauer CP Hall GB Lowe EF Robison CP Hupalo RB Keenan LW 《Environmental management》2008,42(6):1101-1114
The St. Johns River Water Management District (SJRWMD) has developed a minimum flows and levels (MFLs) method that has been
applied to rivers, lakes, wetlands, and springs. The method is primarily focused on ecological protection to ensure systems
meet or exceed minimum eco-hydrologic requirements. MFLs are not calculated from past hydrology. Information from elevation
transects is typically used to determine MFLs. Multiple MFLs define a minimum hydrologic regime to ensure that high, intermediate,
and low hydrologic conditions are protected. MFLs are often expressed as statistics of long-term hydrology incorporating magnitude
(flow and/or level), duration (days), and return interval (years). Timing and rates of change, the two other critical hydrologic
components, should be sufficiently natural. The method is an event-based, non-equilibrium approach. The method is used in
a regulatory water management framework to ensure that surface and groundwater withdrawals do not cause significant harm to
the water resources and ecology of the above referenced system types. MFLs are implemented with hydrologic water budget models
that simulate long-term system hydrology. The method enables a priori hydrologic assessments that include the cumulative effects
of water withdrawals. Additionally, the method can be used to evaluate management options for systems that may be over-allocated
or for eco-hydrologic restoration projects. The method can be used outside of the SJRWMD. However, the goals, criteria, and
indicators of protection used to establish MFLs are system-dependent. Development of regionally important criteria and indicators
of protection may be required prior to use elsewhere. 相似文献
147.
Climate targets call for novel policy measures to facilitate widespread adoption of low-carbon solutions and innovations. The literature on socio-technical systems argues that experimentation has a prominent role in enabling sustainability transition. Experiments represent ways of testing new ideas and methods across a wide range of policy fields. Governance experiments in particular can support accelerated diffusion of new solutions, because they integrate policy with innovations. Here, types of success factors in the implementation of governance experiments to mitigate climate change are examined. Statistical analysis of sustainability innovations in the 28 European Union countries indicates that the types of success factors in governance experiments differ from those of product and social experiments. Governance experimentation is more positioned within socio-technical regimes than in strategic niches. These results suggest that governance experiments may indeed provide new transition opportunities towards low-carbon societies. 相似文献
148.
Jan P.M. van Tatenhove 《环境政策》2016,25(1):160-179
Seas and oceans are confronted with a plethora of environmental problems, caused by land-based activities (agriculture, industries, and ports) and by maritime activities (such as shipping, fishing, oil and gas drilling, tourism, and navigational dredging). Environmental problems at sea challenge the efficacy of state sovereignty. Who is responsible, accountable, and regulates environmental and spatial problems at the level of regional seas, and what is the role of states in these processes of governance? In the regional seas and on the high seas, the environmental state is challenged by two developments: states become players at different levels, and states are confronted with the activities of big market players where they have no or little jurisdiction. The different forms of the environmental state in Europe’s regional seas and in the Arctic Ocean are examined. 相似文献
149.
Arctic ecosystems have experienced and are projected to experience continued large increases in temperature and declines in
sea ice cover. It has been hypothesized that small changes in ecosystem drivers can fundamentally alter ecosystem functioning,
and that this might be particularly pronounced for Arctic ecosystems. We present a suite of simple statistical analyses to
identify changes in the statistical properties of data, emphasizing that changes in the standard error should be considered
in addition to changes in mean properties. The methods are exemplified using sea ice extent, and suggest that the loss rate
of sea ice accelerated by factor of ~5 in 1996, as reported in other studies, but increases in random fluctuations, as an
early warning signal, were observed already in 1990. We recommend to employ the proposed methods more systematically for analyzing
tipping points to document effects of climate change in the Arctic. 相似文献
150.
上海地区酸雨类型格局转变研究 总被引:2,自引:0,他引:2
采用STARS(Sequentialt-test analysis of regime shifts),以降水中SO24-、NO3-以及SO42-/NO3-为指标,研究了上海地区酸雨类型在1991~2006年的格局转变规律。上海地区降水中SO42-含量在1991~2006年具有两种格局,2004年发生转变;转变前的SO42-含量平均12.670mg/L,转变后SO42-含量大幅度降低,平均6.525mg/L;降水中NO3-含量存在3种格局,两次转变;1996年转变前的NO3-浓度相对较低,平均1.842mg/L;此次转变后升高,平均2.622mg/L;2005年再次发生转变,使得NO3-含量下降,平均1.998mg/L;与NO3-含量的格局类似,SO24-/NO3-也存在着3种格局,两次转变;1995年转变前,SO42-/NO3-平均7.316;此次格局转变后,SO42-/NO3-降为5.666;2000年的格局转变中SO24-/NO3-降为3.635。表明NO3-对酸雨的贡献逐渐增加,SO42-对酸雨的贡献逐渐减弱,酸雨类型逐渐由硫酸型酸雨过渡成硫酸和硝酸混合型酸雨,并逐渐接近硝酸型酸雨。上海地区酸雨类型格... 相似文献