Background:Variable Retention Harvesting(VRH)is a forest management practice applied to enhance forest growth,improve biodiversity,preserve ecosystem function and provide economic revenue from harvested timber.There a...Background:Variable Retention Harvesting(VRH)is a forest management practice applied to enhance forest growth,improve biodiversity,preserve ecosystem function and provide economic revenue from harvested timber.There are many different forms and compositions in which VRH is applied in forest ecosystems.In this study,the impacts of four different VRH treatments on transpiration were evaluated in an 83-year-old red pine(Pinus Pinus resinosa)plantation forest in the Great Lakes region in Canada.These VRH treatments included 55%aggregated crown retention(55A),55%dispersed crown retention(55D),33%aggregated crown retention(33A),33%dispersed crown retention(33D)and unharvested control(CN)plot.These VRH treatments were implemented in 1-ha plots in the winter of 2014,while sap flow measurements were conducted from 2018 to 2020.Results:Study results showed that tree-level transpiration was highest among trees in the 55D treatment,followed by 33D,55A,33A and CN plots.We found that photosynthetically active radiation(PAR)and vapor pressure deficit(VPD)were major controls or drivers of transpiration in all VRH treatments.Our study suggests that dispersed or distributed retention of 55%basal area(55D)is the ideal forest management technique to enhance transpiration and forest growth.Conclusions:This study will help researchers,forest managers and decision-makers to improve their understanding of water cycling in forest ecosystem and adopt the best forest management regimes to enhance forest growth,health and resiliency to climate change.展开更多
Background:Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause sign...Background:Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors.Previous studies have shown that much of this uncertainty is related to(i)measurement of sapwood area and(ii)variations in sap flow at different depths within the tree sapwood.Results:This study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine(Pinus resinosa)trees to more accurately estimate water-use at the tree-and stand-level in a plantation forest near Lake Erie in Southern Ontario,Canada.Results showed that most of the water transport(65%)occurred in the outermost sapwood,while only 26%and 9%of water was transported in the middle and innermost depths of sapwood,respectively.Conclusions:These results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%,which may cause large uncertainties in water budgets at the ecosystem and catchment scale.This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.展开更多
基金This study was funded by the Natural Sciences and Engineering Research Council(NSREC),the Global Water Futures Program(GWF),and the Ontario Ministry of Environment,Conservation and Parks(MOECP)grants.
文摘Background:Variable Retention Harvesting(VRH)is a forest management practice applied to enhance forest growth,improve biodiversity,preserve ecosystem function and provide economic revenue from harvested timber.There are many different forms and compositions in which VRH is applied in forest ecosystems.In this study,the impacts of four different VRH treatments on transpiration were evaluated in an 83-year-old red pine(Pinus Pinus resinosa)plantation forest in the Great Lakes region in Canada.These VRH treatments included 55%aggregated crown retention(55A),55%dispersed crown retention(55D),33%aggregated crown retention(33A),33%dispersed crown retention(33D)and unharvested control(CN)plot.These VRH treatments were implemented in 1-ha plots in the winter of 2014,while sap flow measurements were conducted from 2018 to 2020.Results:Study results showed that tree-level transpiration was highest among trees in the 55D treatment,followed by 33D,55A,33A and CN plots.We found that photosynthetically active radiation(PAR)and vapor pressure deficit(VPD)were major controls or drivers of transpiration in all VRH treatments.Our study suggests that dispersed or distributed retention of 55%basal area(55D)is the ideal forest management technique to enhance transpiration and forest growth.Conclusions:This study will help researchers,forest managers and decision-makers to improve their understanding of water cycling in forest ecosystem and adopt the best forest management regimes to enhance forest growth,health and resiliency to climate change.
基金funded by the Natural Sciences and Engineering Research Council(NSREC)the Global Water Futures Program(GWF)the Ontario Ministry of Environment,Conservation and Parks(MOECP).
文摘Background:Scaling sap flux measurements to whole-tree water use or stand-level transpiration is often done using measurements conducted at a single point in the sapwood of the tree and has the potential to cause significant errors.Previous studies have shown that much of this uncertainty is related to(i)measurement of sapwood area and(ii)variations in sap flow at different depths within the tree sapwood.Results:This study measured sap flux density at three depth intervals in the sapwood of 88-year-old red pine(Pinus resinosa)trees to more accurately estimate water-use at the tree-and stand-level in a plantation forest near Lake Erie in Southern Ontario,Canada.Results showed that most of the water transport(65%)occurred in the outermost sapwood,while only 26%and 9%of water was transported in the middle and innermost depths of sapwood,respectively.Conclusions:These results suggest that failing to consider radial variations in sap flux density within trees can lead to an overestimation of transpiration by as much as 81%,which may cause large uncertainties in water budgets at the ecosystem and catchment scale.This study will help to improve our understanding of water use dynamics and reduce uncertainties in sap flow measurements in the temperate pine forest ecosystems in the Great Lakes region and help in protecting these forests in the face of climate change.
