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您的检索式：作者名="Udo Nehren"
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| 1 | Charcoal production through selective logging leads to degradation of dry woodlands:a case study from Mutomo District,Kenya显示文摘Provision of woodfuel is an important ecosystem service of dry forests and woodlands.However,charcoal production through selective logging of preferred hardwood species has the potential to alter the physiognomic composition of the residual or re-growth woodlands and may lead to their deterioration and degradation.This study,conducted through forest inventory in Mutomo District in Kenya,assessed the impact of charcoal production on unprotected dry woodlands in terms of tree density,targeted species basal area,species richness,evenness and Shannon diversity.The parameters of the disturbed woodlands were evaluated for significant differences with those of the neighbouring protected Tsavo East National Park,which served as a reference for an ecologically undisturbed ecosystem.By evaluating a consequence of tree harvesting for charcoal production,this study confirmed the overall significant differences between the protected and unprotected woodlands in all the tested parameters.To confirm if the differences in the land-covers of the woodlands had any influence on their degradation,all mentioned parameters were compared between the four differentiated classes and their respective control plots in the protected areas.At the 'land-cover level',the statistically significant difference in the basal area of tree species preferred for charcoal production between the protected and unprotected open trees confirms that the class with a high density of large mature trees is the prime target of charcoal producers.In addition,there seems to be a general trend of lower values of tree species richness,evenness and Shannon diversity for the unprotected woodlands subjected to charcoal production.On the other hand,the disturbed woodlands display the potential to recover through their comparably high saplings density.The findings make an important contribution to the discourse on the impact of charcoal production in dry woodlands,a topic that is highly controversial among researchers. | Geoffrey M NDEGWA Udo NEHREN Friederike GRüNINGER Miyuki IIYAMA Dieter ANHUF | 2016 | Journal of Arid Land2016，8，4： | 1 |
| 2 | Priority areas for watershed service conservation in the Guapi-Macacu region of Rio de Janeiro,Atlantic Forest,Brazil显示文摘Introduction:Land use intensification and urbanisation processes are degrading hydrological ecosystem services in the Guapi-Macacu watershed of Rio de Janeiro.A proposal to pay farmers to restore natural watershed services might be an alternative to securing the water supply in the long-term for the around 2.5 million urban water users in the study region.This study quantifies the costs of changing current land use patterns to enhance watershed services and compares these costs to the avoided costs associated with water treatment for public supply.Methods:We use farm-household data to estimate the opportunity costs of abandoning current land uses for the recovery of natural vegetation;a process that is very likely to improve water quality in terms of turbidity due to reduced inputs from erosion.Opportunity cost estimates are extrapolated to the watershed scale based on remote sensing land use classifications and vulnerability analysis to identify priority zones for watershed management interventions.To assess the potential demand for watershed services,we analyse water quality and treatment cost data from the main local water treatment plant.Results:Changing agricultural land uses for watershed services provision generally comes at high opportunity costs in our study area near to the metropolis of Rio de Janeiro.Alternative low cost watershed conservation options do exist in the livestock production sector.These options have the potential to directly reduce the amount of sediments and nutrients reaching the water bodies,and in turn decrease the costs of treatment needed for drinking water.Land cover changes at the scale needed to improve water quality will,nonetheless,likely exceed the cost of additional investments in water treatment.Conclusions:The state water utility company’s willingness to pay for watershed services alone will not be enough to induce provision of additional watershed services.We conclude that monetary incentives conditioned on specific adjustments to existing production systems could still have a complementary role to play in improving watershed services.However,we note that our willingness to pay analysis focusses on only one of the potentially wide range of ecosystem services provided by natural vegetation in the Guapi-Macacu watershed.Factoring these ecosystem services into the willingness to pay equation is likely to change our assessment in favour of additional conservation action,be it through PES or other policy instruments. | Vanesa Rodriguez Osuna Jan Borner Udo Nehren Rachel Bardy Prado Hartmut Gaese Jurgen Heinrich | 2014 | Ecological Processes2014，3，1： | 0 |
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