Scatter-hoarding rodents play important roles in plant regeneration and species coexistence in many forest ecosys-tems.Cache pilferage,the behavior of rodents seeking or relocating seeds cached by other individuals,is...Scatter-hoarding rodents play important roles in plant regeneration and species coexistence in many forest ecosys-tems.Cache pilferage,the behavior of rodents seeking or relocating seeds cached by other individuals,is ubiquitous during the scatter-hoarding process.The effects of canopy openness on cache pilferage have received considerable attention,most of which have focused on the comparison between full canopy cover and completely open ar-eas,such as forest gaps.However,little attention has been given to whether the subtle variation in forest canopy openness affects cache pilferage,although subtle variation in light environments exists in many forests,especially tropical and subtropical forests,where the overall canopy is large and the forest window is relatively small.Here,we directly tested these questions by simulating 400 artificial caches,each containing one seed from four selected tree species,in a subtropical forest in southwestern China.The overall canopy openness of the forest was rela-tively small(with a mean value of 11.1%),but subtle spatial variation still existed(ranging from 5.7%to 19.5%).Overall,caches with lower canopy openness were more likely to be pilfered and removed faster,although not all species showed the same pattern.Our study highlights that subtle variation in forest canopy openness,even in a closed primary forest,has significant effects on cache pilferage by rodents,which may influence the following seed germination and forest regeneration processes.Additionally,seedling species composition may further be altered because the canopy effects on cache pilferage are species-specific.展开更多
Temperate woodland vegetation is initially determined by spatiotemporal and historical factors,mediated by complex biotic interactions.However,catastrophic events such as disease outbreaks(e.g.,sweet chestnut blight,a...Temperate woodland vegetation is initially determined by spatiotemporal and historical factors,mediated by complex biotic interactions.However,catastrophic events such as disease outbreaks(e.g.,sweet chestnut blight,ash dieback),infestations of insect pests,and human-accelerated climate change can create canopy gaps due to systematic decline in,or loss of,tree species that was once an important part of the canopy.Resultant cascade effects have the potential to alter the composition of woodland ecosystems quickly and radically,but inherent lag times make primary research into these effects challenging.Here,we explore change in woodland vegetation at 10 sites in response to canopy opening using the Elm Decline,a rapid loss of Ulmus in woodlands across northwestern Europe~5800 years ago that coexisted alongside other stressors such as increasing human activity,as a palaeoecological analogue.For arboreal taxa,community evenness significantly decreased,within-site turnover significantly increased,and richness remained unchanged.Changes in arboreal taxa were highly site-specific but there was a substantial decline in woody climbing taxa,especially Hedera(ivy),across the majority of sites.For shrub taxa,richness significantly increased but evenness and turnover remained consistent.Interestingly,however,there was a significant increase in abundance of shrubs at 70%of sites,including Calluna(heather),Ilex(holly)and Corylus(hazel),suggesting structural change.Surprisingly,there was no change in richness,evenness or turnover for herb taxa,possibly because change was highly variable spatially.However,there was a marked uptick in the disturbance indicator Plantago(plantain).Overall,these findings suggest that woodlands with sustained reduction in,or loss of,a tree species that once formed an important part of the canopy has profound,but often spatially idiosyncratic,impacts on vegetation diversity(richness),composition(evenness),stability(turnover),and on abundance of specific taxa,especially within the shrub layer.Use of this palaeoecological analogue,which was itself complicated by cooccurring changes in human activity,provides a valuable empirical insight into possible cascade effects of similar change in canopy opening in contemporary settings,including Ash Dieback.展开更多
The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and func...The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and functional degradation. The Tinguá Biological Reserve-RJ comprises approximately 26,000 hectares of well-preserved Atlantic Forest, but it is subject to impacts caused by two canopy openings along oil pipelines. Comparisons were made between pipeline edges and forest interiors to evaluate edge effects on the structure and dynamics of those tree communities. Tree densities were higher along forest edges, apparently increasing over time. Tree basal areas, on the other hand, have decreased along edges due to higher mortality rates. Linear canopy opening edges showed higher densities of small trees, while the interior had more very large trees, indicating changes in successional processes and community structural patterns due to edge effects.展开更多
Insect herbivory is ubiquitous in various ecosystems,and directly influences the growth and survival of individual plants,especially during their vulnerable early life stages like the seedling phase.This,in turn,exert...Insect herbivory is ubiquitous in various ecosystems,and directly influences the growth and survival of individual plants,especially during their vulnerable early life stages like the seedling phase.This,in turn,exerts a significant influence on forest community diversity and structure,as well as ecosystem function and stability.Notable variation in herbivory has been detected both among and within plant species.For decades,many hypotheses have been proposed to explain such variations,including both biotic and abiotic variables.However,most studies have considered only one or several of these hypotheses by focusing on a few potential variables,and their results were usually inconsistent;thus,the factors driving herbivory remain unclear.In this study,we examined leaf herbivory by insects of woody species seedlings in a subtropical forest in southwestern China over two seasons.In total,24 potential variables that represented abiotic resource availability,characters of individual seedlings,conspecific and heterospecific species,and the whole seedling community were selected to test several commonly discussed alternative herbivory hypotheses.Overall,our findings showed that the plant apparency hypothesis was more supported than the other hypotheses in explaining insect seedling herbivory.Our results further indicated that the mechanisms and causes of insect herbivory are complex,multifactorial,species-specific and vary with seasons,indicating that there may be no uniform rules in explaining herbivory for all seedlings.Consequently,such complexity may play an important role in promoting species coexistence and biodiversity maintenance in seedling communities,which may further translate into the following generation of saplings or even adult communities.Changes in the community of insect herbivores and/or variables influencing insect herbivory,may disrupt stability of the original seedling community,thus affecting the regeneration and development of the entire forest community.Therefore,we suggest that issues related to insect herbivory should be considered when developing forest management and conservation.展开更多
The natural composition of forests has undergone significant changes over recent centuries.A closer-to-natural tree species composition has long been perceived as key to a high biodiversity.We investigated the impact ...The natural composition of forests has undergone significant changes over recent centuries.A closer-to-natural tree species composition has long been perceived as key to a high biodiversity.We investigated the impact on communities of click beetles(Elateridae)caused by changes in the tree species composition of spruce monocultures compared to reference sites of recently unmanaged natural beech forests.To collect data,passive interception traps were distributed within managed spruce stands of different age classes and natural beech forests of various developmental stages.The beetle species richness was slightly but not significantly higher in the beech forests.The saproxylic species group was significantly more common in the spruce stands,whereas the group of nonsaproxylic species was significantly more abundant in the beech stands.In the commercial stands,the significantly highest species richness was in the clearings(0–10-year-old stands),and at this forest age class,the vast majority of the beetle species occurred in the spruce stands.In the developmental stages of the natural forest,a slightly higher beetle richness was found at the disintegration stage.The study results suggested that different tree species compositions and stand structures affect the communities of click beetles and substantially change their species composition and thus their response to external influences.Therefore,management of stands using diverse silvicultural systems is recommended for creating diverse ecological niches in forests.展开更多
It is a fact that demographic and socio-economic developments are exploitatively exerting severe pressure on forest resources in Nigeria. Not only has the economy of the people been severely affected but also the envi...It is a fact that demographic and socio-economic developments are exploitatively exerting severe pressure on forest resources in Nigeria. Not only has the economy of the people been severely affected but also the environment has witnessed accelerated soil erosion, especially in Eastern Nigeria. Accordingly, this study set out to explore the environmental and socio-economic impacts of deforestation using an empirical case. Two forested and two deforested sites in Ekwusigo L.G.A of Anambra State were closely studied with respect to deforestation indices. From the data generated, Student＇s t-test was used to attempt a statistical comparison of the forested and deforested sites. The findings indicate that forest cover depletion affected both the canopy openness and the number of non-timber forest products in the area, Finally, the paper stressed the need to maintain a sustainable plant cover while economically harnessing forest resources.展开更多
The shrub-tree floristic composition of the natural regeneration stratum of a bauxite mine in the process of restoration and in a reference ecosystem(remnant of a preserved secondary Seasonal Semi-Deciduous Forest)wer...The shrub-tree floristic composition of the natural regeneration stratum of a bauxite mine in the process of restoration and in a reference ecosystem(remnant of a preserved secondary Seasonal Semi-Deciduous Forest)were analysed to evaluate forest restoration conditions after five years of planting.The influence of canopy openness,accumulated leaf litter and soil attributes in the regeneration stratum were also investigated in both the forests.The floristic composition of the regeneration stratum in the forest under restoration(16 species and 5,083 individuals ha-1)and in the reference ecosystem(58 species and 26,250 individuals ha-1)are distinct due to the difference in the environmental variables.Results showed that the reference ecosystem favours the presence of species that tolerate environments with greater shading and higher aluminium and organic matter content in the soil like Psychotria carthagenensis Jacq.,while the forest under restoration favours the presence of species adapted to fertile soils and those that tolerate greater luminosity like Vernonanthura phosphorica(Vell.)H.Rob.展开更多
Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(o...Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(openings)and forest understories(in dense canopies)in a sub-tropical forest of Bangladesh.We objectively identified 42 canopy openings between transect lines and 42 main plots in dense canopies,sampled for regeneration and young tree patterns.For the regeneration study,we placed 2 m×2 m four subplots in each canopy opening and the main plot of dense canopy,thus making a total of 336 subplots.The species diversity of seedlings,saplings,and trees were significantly(P≤0.05)higher in the dense canopy than in the canopy opening.Although,most dominant and frequent regenerating species such as Diospyros pilosula,Garcinia cowa,Brownlowia elata,and Lithocarpus polystachya were common in both dense canopy and openings,the canopy openings had the highest Importance Value Index,suggesting the significance of gap dynamics in the dominance of native floral species.The dense canopy played an important role in forest compositions because 12 regenerating species,including Stereospermum suaveolens and Diospyros montana,were not found in the canopy openings,implying that rain forests must maintain a high canopy cover for regeneration.展开更多
Aims understanding relationships between the distributions of species and their surrounding environment provides a basis for forecasting how species will respond to future environmental changes.In this study,we examin...Aims understanding relationships between the distributions of species and their surrounding environment provides a basis for forecasting how species will respond to future environmental changes.In this study,we examined the effects of environmental factors and human devel-opmental features associated with disturbances on probability of occurrence of juveniles of invasive Triadica sebifera and three native plant species,Baccharis halimifolia,Ilex vomitoria and Morella cer-ifera within a typical coastal transition in coastal mississippi,USA.Methods We recorded presence of juveniles of focal species and measured environmental factors(soil salinity,canopy openness,soil texture and soil carbon to nitrogen ratio)along an 11.3 km transect located at grand bay National Estuarine research reserve.Further,we doc-umented anthropogenic features and associated activities as a proxy for human disturbance.Important Findings With the exception of I.vomitoria,all other species occurrences were significantly influenced by an interaction between soil salinity and canopy openness.The occurrence of I.vomitoria sharply decreased with salinity.B.halimifolia occurrence peaked at moderate levels of salinity and low to moderate levels of canopy openness.occurrences of M.cerifera and the invasive T.sebifera were highest at low levels of salinity and canopy openness.These results indicate that salinity is a strong driver that limits distribution of juvenile native and invasive species in coastal transitions.logistic regression confirmed the positive effects of anthropogenic disturbances on T.sebifera and I.vomitoria occurrence.It appears that while soil salinity is likely to drive retreat of the seaward boundaries of woody plant species distributions,increased human developments along the coast likely enhance the inland spread of species,in particular the invasive T.sebifera by increasing distur-bances and facilitating dispersal.results from this study can offer insight for the development of T.sebifera management and preventive meas-ures for further spread along coastal areas of the southeastern USA.展开更多
基金funded by the National Natural Science Foundation of China(32171533 and 31971444)the Anhui Provincial Natural Science Foundation(2208085J28).
文摘Scatter-hoarding rodents play important roles in plant regeneration and species coexistence in many forest ecosys-tems.Cache pilferage,the behavior of rodents seeking or relocating seeds cached by other individuals,is ubiquitous during the scatter-hoarding process.The effects of canopy openness on cache pilferage have received considerable attention,most of which have focused on the comparison between full canopy cover and completely open ar-eas,such as forest gaps.However,little attention has been given to whether the subtle variation in forest canopy openness affects cache pilferage,although subtle variation in light environments exists in many forests,especially tropical and subtropical forests,where the overall canopy is large and the forest window is relatively small.Here,we directly tested these questions by simulating 400 artificial caches,each containing one seed from four selected tree species,in a subtropical forest in southwestern China.The overall canopy openness of the forest was rela-tively small(with a mean value of 11.1%),but subtle spatial variation still existed(ranging from 5.7%to 19.5%).Overall,caches with lower canopy openness were more likely to be pilfered and removed faster,although not all species showed the same pattern.Our study highlights that subtle variation in forest canopy openness,even in a closed primary forest,has significant effects on cache pilferage by rodents,which may influence the following seed germination and forest regeneration processes.Additionally,seedling species composition may further be altered because the canopy effects on cache pilferage are species-specific.
文摘Temperate woodland vegetation is initially determined by spatiotemporal and historical factors,mediated by complex biotic interactions.However,catastrophic events such as disease outbreaks(e.g.,sweet chestnut blight,ash dieback),infestations of insect pests,and human-accelerated climate change can create canopy gaps due to systematic decline in,or loss of,tree species that was once an important part of the canopy.Resultant cascade effects have the potential to alter the composition of woodland ecosystems quickly and radically,but inherent lag times make primary research into these effects challenging.Here,we explore change in woodland vegetation at 10 sites in response to canopy opening using the Elm Decline,a rapid loss of Ulmus in woodlands across northwestern Europe~5800 years ago that coexisted alongside other stressors such as increasing human activity,as a palaeoecological analogue.For arboreal taxa,community evenness significantly decreased,within-site turnover significantly increased,and richness remained unchanged.Changes in arboreal taxa were highly site-specific but there was a substantial decline in woody climbing taxa,especially Hedera(ivy),across the majority of sites.For shrub taxa,richness significantly increased but evenness and turnover remained consistent.Interestingly,however,there was a significant increase in abundance of shrubs at 70%of sites,including Calluna(heather),Ilex(holly)and Corylus(hazel),suggesting structural change.Surprisingly,there was no change in richness,evenness or turnover for herb taxa,possibly because change was highly variable spatially.However,there was a marked uptick in the disturbance indicator Plantago(plantain).Overall,these findings suggest that woodlands with sustained reduction in,or loss of,a tree species that once formed an important part of the canopy has profound,but often spatially idiosyncratic,impacts on vegetation diversity(richness),composition(evenness),stability(turnover),and on abundance of specific taxa,especially within the shrub layer.Use of this palaeoecological analogue,which was itself complicated by cooccurring changes in human activity,provides a valuable empirical insight into possible cascade effects of similar change in canopy opening in contemporary settings,including Ash Dieback.
文摘The Atlantic forest has historically been severely deforested, and only fragments currently remain that are subject to a wide variety of anthropogenic impacts, including edge effects that can cause structural and functional degradation. The Tinguá Biological Reserve-RJ comprises approximately 26,000 hectares of well-preserved Atlantic Forest, but it is subject to impacts caused by two canopy openings along oil pipelines. Comparisons were made between pipeline edges and forest interiors to evaluate edge effects on the structure and dynamics of those tree communities. Tree densities were higher along forest edges, apparently increasing over time. Tree basal areas, on the other hand, have decreased along edges due to higher mortality rates. Linear canopy opening edges showed higher densities of small trees, while the interior had more very large trees, indicating changes in successional processes and community structural patterns due to edge effects.
基金supported by the National Natural Science Foundation of China(Nos.32171533 and 31971444)Anhui Provincial Natural Science Foundation(No.2208085J28)。
文摘Insect herbivory is ubiquitous in various ecosystems,and directly influences the growth and survival of individual plants,especially during their vulnerable early life stages like the seedling phase.This,in turn,exerts a significant influence on forest community diversity and structure,as well as ecosystem function and stability.Notable variation in herbivory has been detected both among and within plant species.For decades,many hypotheses have been proposed to explain such variations,including both biotic and abiotic variables.However,most studies have considered only one or several of these hypotheses by focusing on a few potential variables,and their results were usually inconsistent;thus,the factors driving herbivory remain unclear.In this study,we examined leaf herbivory by insects of woody species seedlings in a subtropical forest in southwestern China over two seasons.In total,24 potential variables that represented abiotic resource availability,characters of individual seedlings,conspecific and heterospecific species,and the whole seedling community were selected to test several commonly discussed alternative herbivory hypotheses.Overall,our findings showed that the plant apparency hypothesis was more supported than the other hypotheses in explaining insect seedling herbivory.Our results further indicated that the mechanisms and causes of insect herbivory are complex,multifactorial,species-specific and vary with seasons,indicating that there may be no uniform rules in explaining herbivory for all seedlings.Consequently,such complexity may play an important role in promoting species coexistence and biodiversity maintenance in seedling communities,which may further translate into the following generation of saplings or even adult communities.Changes in the community of insect herbivores and/or variables influencing insect herbivory,may disrupt stability of the original seedling community,thus affecting the regeneration and development of the entire forest community.Therefore,we suggest that issues related to insect herbivory should be considered when developing forest management and conservation.
基金funded by the Internal Grant Agency of the Faculty of Forestry and Wood Science,No.43120/1312/3106the support of the Ministry of Agriculture of the Czech Republic,NAZV No.QK21020371.
文摘The natural composition of forests has undergone significant changes over recent centuries.A closer-to-natural tree species composition has long been perceived as key to a high biodiversity.We investigated the impact on communities of click beetles(Elateridae)caused by changes in the tree species composition of spruce monocultures compared to reference sites of recently unmanaged natural beech forests.To collect data,passive interception traps were distributed within managed spruce stands of different age classes and natural beech forests of various developmental stages.The beetle species richness was slightly but not significantly higher in the beech forests.The saproxylic species group was significantly more common in the spruce stands,whereas the group of nonsaproxylic species was significantly more abundant in the beech stands.In the commercial stands,the significantly highest species richness was in the clearings(0–10-year-old stands),and at this forest age class,the vast majority of the beetle species occurred in the spruce stands.In the developmental stages of the natural forest,a slightly higher beetle richness was found at the disintegration stage.The study results suggested that different tree species compositions and stand structures affect the communities of click beetles and substantially change their species composition and thus their response to external influences.Therefore,management of stands using diverse silvicultural systems is recommended for creating diverse ecological niches in forests.
文摘It is a fact that demographic and socio-economic developments are exploitatively exerting severe pressure on forest resources in Nigeria. Not only has the economy of the people been severely affected but also the environment has witnessed accelerated soil erosion, especially in Eastern Nigeria. Accordingly, this study set out to explore the environmental and socio-economic impacts of deforestation using an empirical case. Two forested and two deforested sites in Ekwusigo L.G.A of Anambra State were closely studied with respect to deforestation indices. From the data generated, Student＇s t-test was used to attempt a statistical comparison of the forested and deforested sites. The findings indicate that forest cover depletion affected both the canopy openness and the number of non-timber forest products in the area, Finally, the paper stressed the need to maintain a sustainable plant cover while economically harnessing forest resources.
基金To the National Council of Scientific and Technological Development of Brazil(CNPq),provided fellowships for K.A.Silva(CNPq 142415/2013-8)research fellowships for S.V.Martins.The Companhia Brasileira de Alumínio(CBA)for provided infrastructure and financial support for the project.
文摘The shrub-tree floristic composition of the natural regeneration stratum of a bauxite mine in the process of restoration and in a reference ecosystem(remnant of a preserved secondary Seasonal Semi-Deciduous Forest)were analysed to evaluate forest restoration conditions after five years of planting.The influence of canopy openness,accumulated leaf litter and soil attributes in the regeneration stratum were also investigated in both the forests.The floristic composition of the regeneration stratum in the forest under restoration(16 species and 5,083 individuals ha-1)and in the reference ecosystem(58 species and 26,250 individuals ha-1)are distinct due to the difference in the environmental variables.Results showed that the reference ecosystem favours the presence of species that tolerate environments with greater shading and higher aluminium and organic matter content in the soil like Psychotria carthagenensis Jacq.,while the forest under restoration favours the presence of species adapted to fertile soils and those that tolerate greater luminosity like Vernonanthura phosphorica(Vell.)H.Rob.
文摘Canopy openings have a vital role in forest structure,regeneration,and plant composition.In this study,we investigated and compared the species composition and densities of seedlings and saplings between canopy gaps(openings)and forest understories(in dense canopies)in a sub-tropical forest of Bangladesh.We objectively identified 42 canopy openings between transect lines and 42 main plots in dense canopies,sampled for regeneration and young tree patterns.For the regeneration study,we placed 2 m×2 m four subplots in each canopy opening and the main plot of dense canopy,thus making a total of 336 subplots.The species diversity of seedlings,saplings,and trees were significantly(P≤0.05)higher in the dense canopy than in the canopy opening.Although,most dominant and frequent regenerating species such as Diospyros pilosula,Garcinia cowa,Brownlowia elata,and Lithocarpus polystachya were common in both dense canopy and openings,the canopy openings had the highest Importance Value Index,suggesting the significance of gap dynamics in the dominance of native floral species.The dense canopy played an important role in forest compositions because 12 regenerating species,including Stereospermum suaveolens and Diospyros montana,were not found in the canopy openings,implying that rain forests must maintain a high canopy cover for regeneration.
文摘Aims understanding relationships between the distributions of species and their surrounding environment provides a basis for forecasting how species will respond to future environmental changes.In this study,we examined the effects of environmental factors and human devel-opmental features associated with disturbances on probability of occurrence of juveniles of invasive Triadica sebifera and three native plant species,Baccharis halimifolia,Ilex vomitoria and Morella cer-ifera within a typical coastal transition in coastal mississippi,USA.Methods We recorded presence of juveniles of focal species and measured environmental factors(soil salinity,canopy openness,soil texture and soil carbon to nitrogen ratio)along an 11.3 km transect located at grand bay National Estuarine research reserve.Further,we doc-umented anthropogenic features and associated activities as a proxy for human disturbance.Important Findings With the exception of I.vomitoria,all other species occurrences were significantly influenced by an interaction between soil salinity and canopy openness.The occurrence of I.vomitoria sharply decreased with salinity.B.halimifolia occurrence peaked at moderate levels of salinity and low to moderate levels of canopy openness.occurrences of M.cerifera and the invasive T.sebifera were highest at low levels of salinity and canopy openness.These results indicate that salinity is a strong driver that limits distribution of juvenile native and invasive species in coastal transitions.logistic regression confirmed the positive effects of anthropogenic disturbances on T.sebifera and I.vomitoria occurrence.It appears that while soil salinity is likely to drive retreat of the seaward boundaries of woody plant species distributions,increased human developments along the coast likely enhance the inland spread of species,in particular the invasive T.sebifera by increasing distur-bances and facilitating dispersal.results from this study can offer insight for the development of T.sebifera management and preventive meas-ures for further spread along coastal areas of the southeastern USA.
