Undulations in weather patterns have caused climate shifts of increased frequency and duration around the world. The need for additional research and model data on this pressing problem has resulted in a plethora of r...Undulations in weather patterns have caused climate shifts of increased frequency and duration around the world. The need for additional research and model data on this pressing problem has resulted in a plethora of research groups examining a particular tree species or biome for negative effects of climate change. This review aims to （1） collect and merge recent research data on regeneration within old- and new-growth forests, （2） highlight and expand upon selected topics for additional discussion, and （3） report how shade tolerance, drought toler- ance, and inherent plasticity affect tree growth and development. Al- though shade and drought tolerance have been well studied by a number of research groups, this review reveals that in-depth analysis of a single or a few species in a given area will not generate the data required to implement a successful regeneration plan. Studies using historical accounts of previous species composition, information regarding site sea- sonality, species competition, and individual responses to drought and shade are needed to （1） develop best management plans and （2） ensure future modeling experiments are focused on a greater variety of species using more innovative methods to evaluate climate change effects.展开更多
Spatial variation in tree-regeneration density is attributed to the specialization of tree species to light availability for germination and growth.Light availability,in turn,varies across the gap-understorey mosaic.C...Spatial variation in tree-regeneration density is attributed to the specialization of tree species to light availability for germination and growth.Light availability,in turn,varies across the gap-understorey mosaic.Canopy gaps provide an important habitat for the regeneration of tree species that would otherwise be suppressed in the understory.In subtropical forests,there is still a knowledge-gap relating to how canopy disturbances influence tree-regeneration patterns at local scale,and if they disproportionately favor regeneration of certain species.We aim to analyze whether canopy gaps promote tree regeneration,and tree species are specialized to gaps or understory for germination and growth.We sampled vegetation in 128 plots(0.01 ha),equally distributed in gaps and below canopy,in two subtropical Shorea robusta Gaertn.(Sal)forests in Nepal,recording the number of tree seedlings and saplings in each plot.We compared the regeneration density of seedlings and saplings separately between gaps and the understorey.The mean densities of seedlings and saplings were higher in the gaps at both sites;although there was no difference in the seedling density of the majority of the species between the habitats.No species were confined to either gap or understorey at the seedling stage.We conclude that gaps are not critical for the germination of tree species in Sal forests but these are an important habitat for enabling seedlings to survive into saplings.The classification of trees into regeneration guilds mainly based on germination does not apply to the majority of tree species in subtropical Sal forests.Our results reaffirm that gap creation promotes tree regeneration by favouring seedling survival and growth and can influence forest management for conservation,as well as for plantations.展开更多
Coffee (Coffea arabica L.) is a crop of major economic significance in Tanzania with annual revenue estimated at 100 Million USD. The current mean annual production of the crop is 68,000 MT of clean coffee of which 90...Coffee (Coffea arabica L.) is a crop of major economic significance in Tanzania with annual revenue estimated at 100 Million USD. The current mean annual production of the crop is 68,000 MT of clean coffee of which 90% is contributed by about 450,000 smallholder farmers and while large estate owners contribute the rest. Antestia bug (Antestiopsis orbitalis spp.), the pest known to attack all vegetative and fruiting parts of the coffee tree with substantial yield reduction of up to 45% has been reported to occur contemporary on Arabica coffee in Tanzania, particularly in Kilimanjaro Region. Despite the reported existence of Antestia bug and its damages that badly inflict on the productivity and quality of coffee, the pest status of the bug in Tanzania has never been established. The present study examined the incidence damage severity of Antestia bug in the Arabica coffee fields in major producing regions of Kilimanjaro, Ruvuma and Songwe. A stratified sampling of 360 coffee farms was done on which the Antestia bug incidence and severity were recorded. Results suggested that all regions were infested and the shade intensity influenced the pest incidences with the highest severity record in Kilimanjaro and the least affected was Songwe Region. Dense shade had the highest Antestia bug incidence than sparse shade canopy (p < 0.001). The current study sheds insights into understanding the pest status of Antestia bugs on Arabica coffee in Tanzania which could be used in designing effective management strategies. .展开更多
文摘Undulations in weather patterns have caused climate shifts of increased frequency and duration around the world. The need for additional research and model data on this pressing problem has resulted in a plethora of research groups examining a particular tree species or biome for negative effects of climate change. This review aims to （1） collect and merge recent research data on regeneration within old- and new-growth forests, （2） highlight and expand upon selected topics for additional discussion, and （3） report how shade tolerance, drought toler- ance, and inherent plasticity affect tree growth and development. Al- though shade and drought tolerance have been well studied by a number of research groups, this review reveals that in-depth analysis of a single or a few species in a given area will not generate the data required to implement a successful regeneration plan. Studies using historical accounts of previous species composition, information regarding site sea- sonality, species competition, and individual responses to drought and shade are needed to （1） develop best management plans and （2） ensure future modeling experiments are focused on a greater variety of species using more innovative methods to evaluate climate change effects.
基金the Department of Geography, University of Bergen, and State Education Loan fund (Lanekassen) for financial support to undertake fieldwork
文摘Spatial variation in tree-regeneration density is attributed to the specialization of tree species to light availability for germination and growth.Light availability,in turn,varies across the gap-understorey mosaic.Canopy gaps provide an important habitat for the regeneration of tree species that would otherwise be suppressed in the understory.In subtropical forests,there is still a knowledge-gap relating to how canopy disturbances influence tree-regeneration patterns at local scale,and if they disproportionately favor regeneration of certain species.We aim to analyze whether canopy gaps promote tree regeneration,and tree species are specialized to gaps or understory for germination and growth.We sampled vegetation in 128 plots(0.01 ha),equally distributed in gaps and below canopy,in two subtropical Shorea robusta Gaertn.(Sal)forests in Nepal,recording the number of tree seedlings and saplings in each plot.We compared the regeneration density of seedlings and saplings separately between gaps and the understorey.The mean densities of seedlings and saplings were higher in the gaps at both sites;although there was no difference in the seedling density of the majority of the species between the habitats.No species were confined to either gap or understorey at the seedling stage.We conclude that gaps are not critical for the germination of tree species in Sal forests but these are an important habitat for enabling seedlings to survive into saplings.The classification of trees into regeneration guilds mainly based on germination does not apply to the majority of tree species in subtropical Sal forests.Our results reaffirm that gap creation promotes tree regeneration by favouring seedling survival and growth and can influence forest management for conservation,as well as for plantations.
文摘Coffee (Coffea arabica L.) is a crop of major economic significance in Tanzania with annual revenue estimated at 100 Million USD. The current mean annual production of the crop is 68,000 MT of clean coffee of which 90% is contributed by about 450,000 smallholder farmers and while large estate owners contribute the rest. Antestia bug (Antestiopsis orbitalis spp.), the pest known to attack all vegetative and fruiting parts of the coffee tree with substantial yield reduction of up to 45% has been reported to occur contemporary on Arabica coffee in Tanzania, particularly in Kilimanjaro Region. Despite the reported existence of Antestia bug and its damages that badly inflict on the productivity and quality of coffee, the pest status of the bug in Tanzania has never been established. The present study examined the incidence damage severity of Antestia bug in the Arabica coffee fields in major producing regions of Kilimanjaro, Ruvuma and Songwe. A stratified sampling of 360 coffee farms was done on which the Antestia bug incidence and severity were recorded. Results suggested that all regions were infested and the shade intensity influenced the pest incidences with the highest severity record in Kilimanjaro and the least affected was Songwe Region. Dense shade had the highest Antestia bug incidence than sparse shade canopy (p < 0.001). The current study sheds insights into understanding the pest status of Antestia bugs on Arabica coffee in Tanzania which could be used in designing effective management strategies. .
