Background Understanding the temporal development of community assembly processes is essential for assessing the recovery of degraded ecosystems after restoration.Community development in restored streams is often slo...Background Understanding the temporal development of community assembly processes is essential for assessing the recovery of degraded ecosystems after restoration.Community development in restored streams is often slow or absent,due to inadequate restoration,catchment-scale pressures,and/or colonisation barriers.Recovery processes involve three key filters:dispersal,environmental conditions and biotic interactions.Dispersal is critical for initial colonisation,while environmental conditions influence successful population establishment.Lastly,as available niches fill,biotic interactions,such as competition,gain importance.Despite the presence of many theories on how these three filters interact during community assembly,they have rarely been investigated simultaneously.Our detailed species-and site-specific approach allowed us to analyse the three filters in a hierarchical analysis.We assessed the effect of the three filters,by examining benthic invertebrate communities at 20 sites in the Boye catchment(Western Germany).The Boye and most of its tributaries were used as open sewers for a century,i.e.they were concrete channels transporting untreated sewage before gradual restoration was started in the 1990s.The bank reinforcements and concrete beds were removed,while riparian vegetation was left to natural succession.Accordingly,the sites were grouped as'unimpacted','recently restored'(<4 years),and'mature restored'(>10 years).An additional 28 sites provided information on distances to source populations,while the species'habitat suitability assessed environmental filtering.Biotic(interaction)filtering was evaluated through trait overlap analysis.Results Communities at recently restored sites differed from mature and unimpacted sites,while mature sites resembled unimpacted ones.Taxa at recently restored sites had nearer source populations,while those at mature and unimpacted sites better matched present habitats.Trait overlap did not differ between present and absent taxa.Conclusions Our results indicate that dispersal was essential in early recovery stages,with mass effects from upstream sources supporting taxa found at recently restored sites despite low habitat suitability.Over time,habitat suitability became more influential,shaping mature communities.Competition appeared relatively unimportant,yet competitive exclusion may explain small proportions of absent taxa at mature and recently restored sites.Hence,to effectively support stream recovery,it is essential to consider how different filtering processes operate at various stages of the recovery process.For example,mature communities could further develop if habitat availability increases,while the connectivity to source populations would only play a minor role.展开更多
Background:Habitat degradation is known to have a major impact on the composition of bird communities,yet how these communities recover following such disturbance is less understood.This study examined bird community ...Background:Habitat degradation is known to have a major impact on the composition of bird communities,yet how these communities recover following such disturbance is less understood.This study examined bird community changes from pre-logging to recovery over the course of habitat disturbance caused by the development of the Hulu Terengganu Hydroelectric Dam Project in Peninsular Malaysia,between 2007 and 2018.Bird surveys were conducted using point count observations and mist netting in the dam area from the prelogging phase until the operation phase.Results:It was observed that while bird species significantly declined after large-scale habitat clearance between the pre-logging and construction phases,they showed positive signs of recovery from the inundation to operation phases.These findings indicate that the bird community is still recovering,and the permanent loss of habitat required by most of the original species has not occurred,as evidenced by recolonisation.Bird species composition differed across phases due to varying habitat conditions.The turnover rate and immigration rate(recolonisation and newly recorded species)were higher between the construction and operation phases.It was also observed that insectivorous birds were more heavily affected than others by changes to the landscape,which highlights the versatility,survivability and tolerance of certain species to extreme disturbance and habitat modification.Conclusion:Although the operation phase showed an incremental change in bird species richness due to recolonisation and newly recorded species,this value remains far from that of the pre-logging phase.We predict that bird species recovery will continue to increase for some time before reaching a plateau among the newly created islands,reservoir and catchment area of the dam.展开更多
基金the CRC RESIST,which was funded by the German Research Foundation(Deutsche Forschungsgemeinschaft,DFG)–CRC 1439–project number:426547801
文摘Background Understanding the temporal development of community assembly processes is essential for assessing the recovery of degraded ecosystems after restoration.Community development in restored streams is often slow or absent,due to inadequate restoration,catchment-scale pressures,and/or colonisation barriers.Recovery processes involve three key filters:dispersal,environmental conditions and biotic interactions.Dispersal is critical for initial colonisation,while environmental conditions influence successful population establishment.Lastly,as available niches fill,biotic interactions,such as competition,gain importance.Despite the presence of many theories on how these three filters interact during community assembly,they have rarely been investigated simultaneously.Our detailed species-and site-specific approach allowed us to analyse the three filters in a hierarchical analysis.We assessed the effect of the three filters,by examining benthic invertebrate communities at 20 sites in the Boye catchment(Western Germany).The Boye and most of its tributaries were used as open sewers for a century,i.e.they were concrete channels transporting untreated sewage before gradual restoration was started in the 1990s.The bank reinforcements and concrete beds were removed,while riparian vegetation was left to natural succession.Accordingly,the sites were grouped as'unimpacted','recently restored'(<4 years),and'mature restored'(>10 years).An additional 28 sites provided information on distances to source populations,while the species'habitat suitability assessed environmental filtering.Biotic(interaction)filtering was evaluated through trait overlap analysis.Results Communities at recently restored sites differed from mature and unimpacted sites,while mature sites resembled unimpacted ones.Taxa at recently restored sites had nearer source populations,while those at mature and unimpacted sites better matched present habitats.Trait overlap did not differ between present and absent taxa.Conclusions Our results indicate that dispersal was essential in early recovery stages,with mass effects from upstream sources supporting taxa found at recently restored sites despite low habitat suitability.Over time,habitat suitability became more influential,shaping mature communities.Competition appeared relatively unimportant,yet competitive exclusion may explain small proportions of absent taxa at mature and recently restored sites.Hence,to effectively support stream recovery,it is essential to consider how different filtering processes operate at various stages of the recovery process.For example,mature communities could further develop if habitat availability increases,while the connectivity to source populations would only play a minor role.
基金funded by Tenaga Nasional Berhad Research(TNBR),grant number ST-2017-010.
文摘Background:Habitat degradation is known to have a major impact on the composition of bird communities,yet how these communities recover following such disturbance is less understood.This study examined bird community changes from pre-logging to recovery over the course of habitat disturbance caused by the development of the Hulu Terengganu Hydroelectric Dam Project in Peninsular Malaysia,between 2007 and 2018.Bird surveys were conducted using point count observations and mist netting in the dam area from the prelogging phase until the operation phase.Results:It was observed that while bird species significantly declined after large-scale habitat clearance between the pre-logging and construction phases,they showed positive signs of recovery from the inundation to operation phases.These findings indicate that the bird community is still recovering,and the permanent loss of habitat required by most of the original species has not occurred,as evidenced by recolonisation.Bird species composition differed across phases due to varying habitat conditions.The turnover rate and immigration rate(recolonisation and newly recorded species)were higher between the construction and operation phases.It was also observed that insectivorous birds were more heavily affected than others by changes to the landscape,which highlights the versatility,survivability and tolerance of certain species to extreme disturbance and habitat modification.Conclusion:Although the operation phase showed an incremental change in bird species richness due to recolonisation and newly recorded species,this value remains far from that of the pre-logging phase.We predict that bird species recovery will continue to increase for some time before reaching a plateau among the newly created islands,reservoir and catchment area of the dam.
