Coffea cultivation with shade tree is used for improving soil health,increasing coffea production,sustaining agro ecology.The study was attended in two kebele,on 36 farmers’fields,at Gololcha district of East Arsi zo...Coffea cultivation with shade tree is used for improving soil health,increasing coffea production,sustaining agro ecology.The study was attended in two kebele,on 36 farmers’fields,at Gololcha district of East Arsi zone.The study was intended to assess the influence of coffea shade trees on farm lands versus mountainous area.Household interviews were used to get imperative separately,i.e.from old farmers,middle age farmers and young farmers.Significant difference value was observed between farm land and mountainous area coverage.Based on this respondents’idea,before 25-30 years;the‘condition of tree coverage at mountainous’area in Arsi Gololcha district was‘medium condition’but not normal that means as deforestation of mountainous area have been starting before 30 years’time;while the condition of tree coverage at farmland area also has been starting before 30 years’time.The third respondents’idea was interpreted with the real situation of the district,that it gave us a constructive inspiration on the role of coffea shade tree to enable the farm land to be taken as regular natural forest.The existing coffea shade trees are Cordia africana followed by Erythrina abyssinica and Acacia senegal.Farmers accounted 95%of coffea shade users and 4.6%without shade users.The respondents said that even if the rainfall intensity is increasing at farmland rather than mountainous area occasionally due to shade tree effect.On the contrary side,mountainous area exposed to deforestation since the farmers have been shifting to hilly side for their livelihood dependency.展开更多
Abstrac Khmelnitskaya et al.have recently proposed the average covering tree value as a new solution concept for cooperative transferable utility games with directed graph structure.The average covering tree value is...Abstrac Khmelnitskaya et al.have recently proposed the average covering tree value as a new solution concept for cooperative transferable utility games with directed graph structure.The average covering tree value is defined as the average of marginal contribution vectors corresponding to the specific set of rooted trees,and coincides with the Shapley value when the game has complete communication structure.In this paper,we discuss the computational complexity of the average covering tree value.We show that computation of the average covering tree value is#P-complete even if the characteristic function of the game is{0,1}-valued.We prove this by a reduction from counting the number of all linear extensions of a partial order,which has been shown by Brightwell et al.to be a#P-complete counting problem.The implication of this result is that an efficient algorithm to calculate the average covering tree value is unlikely to exist.展开更多
文摘Coffea cultivation with shade tree is used for improving soil health,increasing coffea production,sustaining agro ecology.The study was attended in two kebele,on 36 farmers’fields,at Gololcha district of East Arsi zone.The study was intended to assess the influence of coffea shade trees on farm lands versus mountainous area.Household interviews were used to get imperative separately,i.e.from old farmers,middle age farmers and young farmers.Significant difference value was observed between farm land and mountainous area coverage.Based on this respondents’idea,before 25-30 years;the‘condition of tree coverage at mountainous’area in Arsi Gololcha district was‘medium condition’but not normal that means as deforestation of mountainous area have been starting before 30 years’time;while the condition of tree coverage at farmland area also has been starting before 30 years’time.The third respondents’idea was interpreted with the real situation of the district,that it gave us a constructive inspiration on the role of coffea shade tree to enable the farm land to be taken as regular natural forest.The existing coffea shade trees are Cordia africana followed by Erythrina abyssinica and Acacia senegal.Farmers accounted 95%of coffea shade users and 4.6%without shade users.The respondents said that even if the rainfall intensity is increasing at farmland rather than mountainous area occasionally due to shade tree effect.On the contrary side,mountainous area exposed to deforestation since the farmers have been shifting to hilly side for their livelihood dependency.
基金This work was partially supported by the Okawa Foundation for Information and TelecommunicationWe wish to thank the two anonymous reviewers for their constructive suggestions and comments.The comments have helped us significantly improve the paper.
文摘Abstrac Khmelnitskaya et al.have recently proposed the average covering tree value as a new solution concept for cooperative transferable utility games with directed graph structure.The average covering tree value is defined as the average of marginal contribution vectors corresponding to the specific set of rooted trees,and coincides with the Shapley value when the game has complete communication structure.In this paper,we discuss the computational complexity of the average covering tree value.We show that computation of the average covering tree value is#P-complete even if the characteristic function of the game is{0,1}-valued.We prove this by a reduction from counting the number of all linear extensions of a partial order,which has been shown by Brightwell et al.to be a#P-complete counting problem.The implication of this result is that an efficient algorithm to calculate the average covering tree value is unlikely to exist.
