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湿地是大气甲烷（CH4）的主要排放源，而有关放牧对湿地CH4排放的影响特征仍未得到足够的报道。因此，通过静态箱法，研究了放牧对四川省若尔盖高原湿地CH4排放的影响，CH4气体通过快速温室气体分析仪测量。结果表明：放牧样地和围栏内样地生长季CH4排放量为（31.32±19.57）g/m2和（30.31±23.46）g/m2，它们之间无差异显著；但是集中放牧期间（7-9月），放牧样地（21.01±12.35）g/m2较围栏内样地显著增加了CH4排放量为54.3%。2014年生长季期间通过刈割植物模拟放牧表明两种刈割强度CH4排放量为（5.01±5.37）g/m2和（4.69±5.99）g/m2，较未刈割样地（1.15±1.89）g/m2增加了335.9%和308.0%，其原因可能是放牧或者刈割减少地表植物生物量，降低植物高度，缩短了CH4排放的路径距离。该结果可为我国高原湿地保护与管理决策提供基础数据支撑。

Lakes provide multiple functions to society through commerce,aesthetics,tourism,recreation and biodiversity conservation.Dredging occurs frequently in many lakes,rivers,harbors,or coastal areas to maintain adequate water depths for navigation,provide sand and gravel for construction and reclamation projects,or to remove contaminated sediment to improve water quality and restore the health of aquatic ecosystems.However,long-term and intensive dredging can also cause disturbances to aquatic ecosystems with adverse impacts.Dredging stirs up sediment,increases suspended sediment concentration and reduces water clarity.Thus,dredging alters the physical,chemical and biological properties of the aquatic environment,and further might affect the provision of lake functions.Dredging in Poyang Lake started in 2001.After the activity was banned from the Yangtze River,it increased in Poyang Lake because of the rapidly rising demand for sand in order to support construction in the lower Yangtze River economic zone.The benefits to the local economy are likely to further have persuaded the local government to allow and possibly promote dredging in this lake.Dredging in Poyang Lake was focused at the north of Songmen Mountain before 2010,while the activity has moved to the central parts of Poyang Lake during the most recent two years.However,the distribution of dredging in central Poyang Lake and its impact zone and intensity are not clear.This study,using multi-remote sensing images,aimed to describe the distribution of dredging activities in central Poyang Lake,and further analyze its impact on suspended sediment concentrations(SSC).The Landsat Thematic Mapper(TM) 5 captured on July 28,2011 was employed to identify the dredging-related vessels through visual interpretation.Moderate resolution imaging spectroradiometer(MODIS) images from the Terra satellite taken over the months July-August for three years(2009—2011) combined with a regression model were applied to retrieve the SSC in Poyang Lake,and the before-after-control-impact(BACI) method with three evaluated regions was used to assess the impact of dredging on SSC.Two dredging regions and more than 90 vessels were observed from the TM 5 image in the central Poyang Lake.The MODIS-based SSC values indicated that the SSC increased in the dredging regions and their downstream impact zones from 10 mg/L before dredging to 50 mg/L after the start of dredging.The BACI analyses confirmed that dredging increased the SSC in Poyang Lake by comparing an impacted region with a non-impacted region.Currently,many lakes around the world are suffering a number of problems caused by natural and/or human factors,which may hamper the sustainable developments of multiple lake functions.Remote sensing techniques may provide methods to obtain the spatio-temporal variations of these problems,which will help managers or researchers to analyze and understand the processes and mechanisms in lakes and make sound decisions for lake management.Poyang Lake is an important habitat for several rare or endangered species,such as the baiji(Lipotes vexillifer),Chinese sturgeon(Acipenser sinensis),white sturgeon(Acipenser transmontanus),and Yangtze finless porpoise(Neophocaena phocaenoides).The lake is reputed to be the most important habitat for wintering waterfowl in East Asia,and more than 95% of the Siberian crane(Grus leucogeranus) population winters here.Dredging has seriously affected directly or indirectly the survival of these rare or endangered species.There is an urgent need to balance the relationship between economic development and ecological conservation,minimize the negative effects of dredging and preserve the various productive,environmental and ecological functions provided by Poyang Lake.

A wetland ecosystem is one of the most important ecosystems on earth.It plays important roles in ecological balances and provides human beings with products such as food,water and entertainment.Therefore,wetland resource conservation is one of the key issues in global ecological environment protection.Based on the analysis of economic attributes of wetland resource conservation and the theories of property rights,public goods and externality,this research,taking the Beijing Wild Duck Lake(BWDL) wetland as an example,emphatically analyzed(1) the externality in the processes of BWDL resource protection and(2) the costs and the profits in the BWDL resource utilization.The results show:(1) Individual profits may not be compensated due to positive externality,which leads to the deficiency of resources during the wetland protection.We hold that a reasonable compensation mechanism should be built in order to compensate the people who participate in the protection of wetlands.Only when their individual profits were safeguarded then can the social optimal point be achieved.In addition,people who destroy wetland resources may not be punished due to negative externality.If there is no valid constraint mechanism for these behaviors of destroying wetland resources,deterioration of wetland resources cannot be avoided.Hence,in the view of externality theory,the primary reason caused the wetland deterioration is the lack of compensation and constraint mechanism of positive and negative externality.(2) Free riding will lead to the deterioration of wetland resources.Taking cage fish culture in the BWDL as an example,we analyzed the negative effect from free riding.Results show that free riding existed in the utilization of wetland resources,resulting in the excessive use of wetland resources.Once the carrying capacity of local wetland ecosystems was broken,wetland resources will deteriorate further.Hence,one of the most challenges facing by wetland resources protection is how to coordinate the contradiction between cost and benefit during the protection and utilization of wetland resources.(3) A clear property rights is good for wetland resources protection.Free riding and externality are,fundamentally,results of unclear property rights of wetland resources.In China,most of natural resources with characteristics of public goods belong to two types: state or collective ownership.The allocation efficient of wetland resources will be low under the condition of unclear property rights.Individual person who protect wetland resources cannot get expect revenue.Converting the operation right and revenue right to individual may be a good way to solve the above problems.Individual is response for cost and benefit during the utilization of wetland resources.The allocation efficient will be improved and market failure can thus be avoided.Thereafter,administers of wetlands should define behaviors and reasonability of damage behaviors of wetland resources.Meanwhile,they should also make clear about the right and responsibility of wetland resource users.These research results would provide references for the problems in wetland protection processes in our country.In particular,it can provide scientific basis and policy options in the BWDL wetland conservation.

Wetlands are unique habitats formed in the interactions between water and land.As one of the most productive ecological systems with richest biodiversity,it plays an irreplaceable role in the maintenance of ecological safety.Since the 1970s,wetland loss and degradation have sparked a series of environmental problems on a global scale,which have become a major threat to national or global sustainable development.Especially,rapid economic development combined with the lacks of wetland protection in China,have lead to serious imbalance between wetland protection and economic development.As a result of the above problems,decreased natural wetland and degradation of wetland function seem out of control.Now,wetland ecological compensation became more and more important because it is a choice for sustainable utilization of wetland resources.As an economic and policy means widely applied in developed countries,ecological compensation has been effectively used in the adjustment of natural resources conservation and resource utilization. Wetland ecological compensation study has always been a hot but difficult research spot.As an important ecological barrier in the western China,Crested ibis national Nature Reserve plays an important role in protection Crested ibis as well as its habitats.However,wetlands in Qinling Nature Reserve are typical ecological and environmental vulnerable zones.Excessive development and resource utilization makes the vulnerability of ecology and environment of this region increasing.It is necessary to take effective measures to develop a reasonable ecological compensation mechanism and policies for the coordination of ecological and economic development.As a basic unit in the implementation of ecological compensation,local farmers are key actors to give impetus to the ecological compensation.Understanding their willingness in cooperation and compensation is particularly important for improving farmers′ ecological compensation enthusiasm,formulation and implementation of ecological compensation policies. Taking Crested ibis Nature Reserve in Shanxi Province as an example,this study applied Contingent Valuation Method(CVM) to measure ecological compensation amounts of rice loss of local farmers in 2008 and 2011.Firsthand information was collected through structured interview and questionnaire survey.Results indicate that the compensation amounts are,respectively,3560.56 yuan/hm2 and 3679.83 yuan/hm2.Logistic regression model analysis results show that the most important factor that affects farmers` willings of the ecological compensation is the ratio between paddy field and the total area of arable land.Besides,family annual average income,the presence of non-agricultural income,the distance from Crested ibis reserve and decrease amount of rice production because of Crested ibis protection.The results also indicate that the government should dominate the ecological compensation and develop long-term mechanism for ecological management.It is necessary to note that the current eco-compensation mechanism needs further improve.Additional actions are needed to maintain basic living standards of local farmers,such as investments into the processing industry and job training programs.This study provides principle guidelines for implementing eco-compensation across Crested ibis Nature Reserve as well as others.This study can be served as a start case for promoting wetland ecological compensation mechanism,especially for Shaanxi Crested ibis Nature Reserve.