Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diver...Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment(as of2018) in Japan.Results: I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages(≤ 3 years), the positive complementarity effect was explained by enhanced growths of early-and mid-successional species in the mixture. Later on(≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer.Conclusions: The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.展开更多
The mechanisms responsible for species replacement during ecological successions is a long-standing and open debate. In this study, we examined the distribution of the Sardinian warbler Sylvia melanocephala along two ...The mechanisms responsible for species replacement during ecological successions is a long-standing and open debate. In this study, we examined the distribution of the Sardinian warbler Sylvia melanocephala along two grassland-to-forest gradients, one in a high-diversity area （Albera-Aspres chain in Catalonia： eight Sylvia warbler species） and one in a low-diversity area （Mount Hymittos in Greece： four species）. In Catalonia, distribution models suggested that the apparent exclusion of S. melanocephala from the open and forest ends of the gradient may be explained entirely by the preference of S. melanocephala for mid-successional shrublands. However, a joint analysis of both data sets revealed that： 1） S. melanocephala was more evenly dis- tributed along the vegetation gradient in Greece, suggesting ecological release in the low-diversity area; and 2） a distribution model assuming interspecific competition （based on the distribution of Sylvia species showing a negative co-occurrence pattern with S. melanocephala） had a significantly higher predictive ability than a distribution model based on habitat variables alone. Our study supports the view that species turnover along ecological gradients generally results from a combination of intrinsic preferences and interspecific competition [Current Zoology 57 （3）： 307-317, 2011].展开更多
目的旨在了解老年慢性病患者成功老龄化现状的基础上,探究健康素养、社会支持、选择、优化和补偿模型(the model of selective optimization with compensation,SOC)与成功老龄关系模型,为护理领域成功老龄化相关研究提供参考依据.方法...目的旨在了解老年慢性病患者成功老龄化现状的基础上,探究健康素养、社会支持、选择、优化和补偿模型(the model of selective optimization with compensation,SOC)与成功老龄关系模型,为护理领域成功老龄化相关研究提供参考依据.方法采用一般资料问卷、慢性病病人健康素养量表、社会支持评定量表、SOC策略问卷、成功老龄量表,于2018年6-7月对延吉市328名老年慢性病患者进行调查.结果研究对象成功老龄化得分为(50.08±12.12)分,处于中等水平,男性、汉族、有配偶的老年慢性病患者其健康素养、社会支持、SOC与成功老龄化得分较高(均P<0.01),健康素养、社会支持、SOC与成功老龄化两两呈正相关(r=0.125~0.919,均P<0.01),社会支持对成功老龄化有正向影响,并通过SOC间接对成功老龄化产生正向影响(P<0.01),健康素养通过社会支持和SOC影响成功老龄化(P<0.01).结论提高健康素养和社会支持水平,可为老年慢性病患者采取SOC策略提供资源,进而促进其成功老龄化;护理人员对老年慢性病患者的健康干预策略的研究和实践,必须要重视健康素养和社会支持水平及其相关因素的影响.展开更多
As in any field of research, the study of sexual selection is subject to ongoing debate over definitions and interpreta- tions of the fundamental concepts involved. These arguments generally promote progress, as they ...As in any field of research, the study of sexual selection is subject to ongoing debate over definitions and interpreta- tions of the fundamental concepts involved. These arguments generally promote progress, as they highlight areas where current explanations are incomplete. Here we briefly review two ongoing discussions in the sexual selection literature. First, the definition of sexual selection has received renewed interest in light of increasing research effort into when and how it operates in females. Second, how best to measure sexual selection is an ongoing subject of debate; in practice, recognition that the appropriate measures depend on the focus of the specific study, and that multiple measures should be employed wherever possible, seems to provide the most informative approach. The wide scope of recent empirical work in these and related areas, with the application of new techniques and approaches, reflects that the field of sexual selection is being constantly expanded and enriched展开更多
In polygynous systems,such as that exhibited by reindeer Rangifer tarandus,mate choice can be difficult to disentangle from male intrasexual competition because male behavior may constrain female choice.Multiple matin...In polygynous systems,such as that exhibited by reindeer Rangifer tarandus,mate choice can be difficult to disentangle from male intrasexual competition because male behavior may constrain female choice.Multiple mating may provide an avenue for female mate choice,though it is difficult to identify using behavioral estimators alone.Molecular techniques address this issue by affording ecologists an opportunity to reassess mating systems from a genetic perspective.We assessed the frequency and possible explanations for multiple mating in reindeer using a genetic approach to determine the success of observed copulations in a semi-domesticated herd in Kaamanen,Finland.Behavioral and genetic data were synthesized with population characteristics over a 7-year period to test the hypothesis that,if present,polyandry in reindeer is driven by sexual harassment from sub-dominant males.We observed multiple mating in 42%of females,with as many as 60%exhibiting multiple mating in certain years.We found no evidence that multiple mating resulted from sexual harassment by sub-dominant males,suggesting that it is likely a deliberate strategy among females.Conversion rate of copulations into paternities varied with male size,with smaller males more likely to experience mismatch than larger males.Female preference for larger males persisted despite the occurrence of multiple mating,possibly suggesting a mechanism for cryptic post-copulatory selection.We suggest further research to delineate the possible influence of cryptic post-copulatory selection and multiple mating to defend against infertility in exhausted males.展开更多
基金a Grant-in-Aid for Young Scientists B (No. 16 K18715)a JSPS Overseas Research Fellowship (No. 201860500) from the Japan Society for the Promotion of Science。
文摘Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment(as of2018) in Japan.Results: I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages(≤ 3 years), the positive complementarity effect was explained by enhanced growths of early-and mid-successional species in the mixture. Later on(≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer.Conclusions: The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.
文摘The mechanisms responsible for species replacement during ecological successions is a long-standing and open debate. In this study, we examined the distribution of the Sardinian warbler Sylvia melanocephala along two grassland-to-forest gradients, one in a high-diversity area （Albera-Aspres chain in Catalonia： eight Sylvia warbler species） and one in a low-diversity area （Mount Hymittos in Greece： four species）. In Catalonia, distribution models suggested that the apparent exclusion of S. melanocephala from the open and forest ends of the gradient may be explained entirely by the preference of S. melanocephala for mid-successional shrublands. However, a joint analysis of both data sets revealed that： 1） S. melanocephala was more evenly dis- tributed along the vegetation gradient in Greece, suggesting ecological release in the low-diversity area; and 2） a distribution model assuming interspecific competition （based on the distribution of Sylvia species showing a negative co-occurrence pattern with S. melanocephala） had a significantly higher predictive ability than a distribution model based on habitat variables alone. Our study supports the view that species turnover along ecological gradients generally results from a combination of intrinsic preferences and interspecific competition [Current Zoology 57 （3）： 307-317, 2011].
文摘目的旨在了解老年慢性病患者成功老龄化现状的基础上,探究健康素养、社会支持、选择、优化和补偿模型(the model of selective optimization with compensation,SOC)与成功老龄关系模型,为护理领域成功老龄化相关研究提供参考依据.方法采用一般资料问卷、慢性病病人健康素养量表、社会支持评定量表、SOC策略问卷、成功老龄量表,于2018年6-7月对延吉市328名老年慢性病患者进行调查.结果研究对象成功老龄化得分为(50.08±12.12)分,处于中等水平,男性、汉族、有配偶的老年慢性病患者其健康素养、社会支持、SOC与成功老龄化得分较高(均P<0.01),健康素养、社会支持、SOC与成功老龄化两两呈正相关(r=0.125~0.919,均P<0.01),社会支持对成功老龄化有正向影响,并通过SOC间接对成功老龄化产生正向影响(P<0.01),健康素养通过社会支持和SOC影响成功老龄化(P<0.01).结论提高健康素养和社会支持水平,可为老年慢性病患者采取SOC策略提供资源,进而促进其成功老龄化;护理人员对老年慢性病患者的健康干预策略的研究和实践,必须要重视健康素养和社会支持水平及其相关因素的影响.
文摘As in any field of research, the study of sexual selection is subject to ongoing debate over definitions and interpreta- tions of the fundamental concepts involved. These arguments generally promote progress, as they highlight areas where current explanations are incomplete. Here we briefly review two ongoing discussions in the sexual selection literature. First, the definition of sexual selection has received renewed interest in light of increasing research effort into when and how it operates in females. Second, how best to measure sexual selection is an ongoing subject of debate; in practice, recognition that the appropriate measures depend on the focus of the specific study, and that multiple measures should be employed wherever possible, seems to provide the most informative approach. The wide scope of recent empirical work in these and related areas, with the application of new techniques and approaches, reflects that the field of sexual selection is being constantly expanded and enriched
基金We thank the following organizations for their financial support:the Québec Centre for Biodiversity Science(QCBS)and the Northern Scientific Training Program(NSTP)to K.Coombs,the Natural Sciences and Engineering Research Council of Canada(NSERCgrant number 303807)to R.Weladji,and NORDFORSK(project number 76915)to O.Holand and K.Rod.
文摘In polygynous systems,such as that exhibited by reindeer Rangifer tarandus,mate choice can be difficult to disentangle from male intrasexual competition because male behavior may constrain female choice.Multiple mating may provide an avenue for female mate choice,though it is difficult to identify using behavioral estimators alone.Molecular techniques address this issue by affording ecologists an opportunity to reassess mating systems from a genetic perspective.We assessed the frequency and possible explanations for multiple mating in reindeer using a genetic approach to determine the success of observed copulations in a semi-domesticated herd in Kaamanen,Finland.Behavioral and genetic data were synthesized with population characteristics over a 7-year period to test the hypothesis that,if present,polyandry in reindeer is driven by sexual harassment from sub-dominant males.We observed multiple mating in 42%of females,with as many as 60%exhibiting multiple mating in certain years.We found no evidence that multiple mating resulted from sexual harassment by sub-dominant males,suggesting that it is likely a deliberate strategy among females.Conversion rate of copulations into paternities varied with male size,with smaller males more likely to experience mismatch than larger males.Female preference for larger males persisted despite the occurrence of multiple mating,possibly suggesting a mechanism for cryptic post-copulatory selection.We suggest further research to delineate the possible influence of cryptic post-copulatory selection and multiple mating to defend against infertility in exhausted males.
