The urban and community forestry movement in the United States has matured over the last 20 years from managing street trees, to understanding the benefits of trees in urban ecosystems, and now to managing urban green...The urban and community forestry movement in the United States has matured over the last 20 years from managing street trees, to understanding the benefits of trees in urban ecosystems, and now to managing urban green infrastructure. This paper introduced the history, development, and major accomplishments of the urban and community forestry movement, highlighted the economic, ecological, environmental, and social values of forests and trees to communities, and discussed issues and trends of the urban and community forestry program in the United States.展开更多
As climate change negotiations progress,monitoring biomass and carbon stocks is becoming an important part of the current forest research.Therefore,national governments are interested in developing forest-monitoring s...As climate change negotiations progress,monitoring biomass and carbon stocks is becoming an important part of the current forest research.Therefore,national governments are interested in developing forest-monitoring strategies using geospatial technology.Among statistical methods for mapping biomass,there is a nonparametric approach called k-nearest neighbor(kNN).We compared four variations of distance metrics of the kNN for the spatially-explicit estimation of aboveground biomass in a portion of the Mexican north border of the intertropical zone.Satellite derived,climatic,and topographic predictor variables were combined with the Mexican National Forest Inventory(NFI)data to accomplish the purpose.Performance of distance metrics applied into the kNN algorithm was evaluated using a cross validation leave-one-out technique.The results indicate that the Most Similar Neighbor(MSN)approach maximizes the correlation between predictor and response variables(r=0.9).Our results are in agreement with those reported in the literature.These findings confirm the predictive potential of the MSN approach for mapping forest variables at pixel level under the policy of Reducing Emission from Deforestation and Forest Degradation(REDD+).展开更多
Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha lat...Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season（May–September）in 2011 at two sites with the high and low metal loads,respectively.The objective of this study was to understand the metal（Fe,Mn,Cu,Pb and Zn）concentration and spatial distributions in P.australis and T.latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence（μXRF）and synchrotron X-ray computed microtomography（μCMT）techniques.The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis.Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different.Significant correlations were found between metals（Cu,Mn,Pb and Zn）and Fe in the epidermis,implying that metals were scavenged by Fe oxides.The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific.The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.展开更多
The relationship between soil variables and forest productivity of Eucalyptus urophylla (Eu) and E. grandis (Eg) was studied in commercial forest plantations (CFP) in Huimanguillo, Tabasco, Mexico. The group of Eu inc...The relationship between soil variables and forest productivity of Eucalyptus urophylla (Eu) and E. grandis (Eg) was studied in commercial forest plantations (CFP) in Huimanguillo, Tabasco, Mexico. The group of Eu included seed and clone raised plantations and the Eg group included only seed raised plantations. Tree measurements and soil sampling were carried out at 56 500-m2 plots. Two soil depths (0 - 20 and 20 - 40 cm) were sampled and analyzed for physical and chemical properties. Site Index (SI), calculated at year 14 was used as indicator of forest productivity. Simple correlation, multiple and second order regressions were used to test the effect of soil variables on productivity. Results showed that mean annual increments (MAI) of Eu and Eg were comparable to other regions of the world reaching 49 m3·ha-1·y-1 across a range of low to high soil fertility gradient (15 to 80 m3·ha-1·y-1). For both species, regardless of the production method (seed or clone), soil texture was the most relevant variable to explain variation in productivity. Eu productivity was correlated to exchangeable Mg (0.3) and Al (0.3) in the 0 - 20 cm soil depth and CEC (0.4) and exchangeable Al (0.6) in the 20 - 40 cm soil depth. Compared to clone plantations, seed plantations showed higher correlations between soils properties and productivity. Aluminum saturation was negatively related to Eg productivity. The highest correlation between soil and productivity were found for Eg, with soil P-availability and aluminum saturation explaining 82 and 85% of the variation, respectively. This works shows that low fertility soils, previously used as pasturelands can be productive for forest plantation purposes and contribute to carbon sequestration.展开更多
Aims Recognizing ungulate browsing thresholds between viable and declining aspen(Populus tremuloides Michx.)stands are critical to ensuring long-term persistence of this biologically important plant community.Studies ...Aims Recognizing ungulate browsing thresholds between viable and declining aspen(Populus tremuloides Michx.)stands are critical to ensuring long-term persistence of this biologically important plant community.Studies have shown declines in vigor and regeneration when as few as 30%of current annual twigs are browsed while other studies have shown higher limits.Although the effects of ungulate herbivory are of concern in aspen forests,few studies have assessed browsing effects following wildfire and few criteria exist for deter-mining potential effects of ungulate browsing on aspen forests fol-lowing wildfire.We evaluated the effects of ungulate abundance and foraging intensity on regenerating aspen 1 to 6 years post-fire and assessed the use of abundance and foraging intensity indicators in predicting impacts to regenerating aspen.Rocky Mountain elk(Cervus elaphus nelson)was the primary ungulate in the study area.Methods The study area was located within the 17500 ha cerro Grande Fire burn area in the Jemez Mountains,New Mexico,USA.We used percent aspen twigs browsed and pellet-group counts to evaluate relationships between these indicators and aspen patch structure(height,size).We collected data in randomly generated 3×33 m plots 5-6 years post-fire.We also established 4 fenced exclosures(25×55 m and 3.3 m in height)with paired unfenced plots 1-year post-fire to monitor aspen regeneration.Each spring,we recorded percent browsed twigs from the previous fall through the early spring period which coincided with the highest ungulate use period within the study area.We assessed associations between percent twigs browsed and pellet-group density and patch size and height of aspen using Spearman’s correlation coefficients.Important Findings Mean percent twigs browsed and ungulate pellet-group density across the burn area was≤31%and 1 pellet-group 100 sq m−1,respectively.Patch size and height decreased with increasing browsing and pellet-group density 5-6 years post-fire.However,mean aspen heights were approaching or exceeding a minimum browsing level of 2 m and,therefore,ungulate browsing did not appear sufficient to cause signif-icant impacts to aspen across the burn area.We observed a positive correlation between pellet-group density and twig browsing suggest-ing that one or both measures could be used to assess potential effects of browsing on regenerating aspen following fire.展开更多
文摘The urban and community forestry movement in the United States has matured over the last 20 years from managing street trees, to understanding the benefits of trees in urban ecosystems, and now to managing urban green infrastructure. This paper introduced the history, development, and major accomplishments of the urban and community forestry movement, highlighted the economic, ecological, environmental, and social values of forests and trees to communities, and discussed issues and trends of the urban and community forestry program in the United States.
文摘As climate change negotiations progress,monitoring biomass and carbon stocks is becoming an important part of the current forest research.Therefore,national governments are interested in developing forest-monitoring strategies using geospatial technology.Among statistical methods for mapping biomass,there is a nonparametric approach called k-nearest neighbor(kNN).We compared four variations of distance metrics of the kNN for the spatially-explicit estimation of aboveground biomass in a portion of the Mexican north border of the intertropical zone.Satellite derived,climatic,and topographic predictor variables were combined with the Mexican National Forest Inventory(NFI)data to accomplish the purpose.Performance of distance metrics applied into the kNN algorithm was evaluated using a cross validation leave-one-out technique.The results indicate that the Most Similar Neighbor(MSN)approach maximizes the correlation between predictor and response variables(r=0.9).Our results are in agreement with those reported in the literature.These findings confirm the predictive potential of the MSN approach for mapping forest variables at pixel level under the policy of Reducing Emission from Deforestation and Forest Degradation(REDD+).
基金supported in part by the Margaret and Herman Sokol Foundation(HF)China Scholarship Council(YQ)+6 种基金the State Key Laboratory of Estuarine and Coastal Research Open Research Fund(Ref #:SKLEC-KF201304)(HF,WZ,LY,YQ)supported in part by the U.S.Department of Energy,Office of Science,Office of Workforce Development for Teachers and Scientists(WDTS)under the Visiting Faculty Program(VFP)(HF)Portions of this work were performed at Beamline X27A,National Synchrotron Light Source(NSLS),and Biosciences Department,Brookhaven National LaboratoryWork in Bioscience Department,BNL,was partially supported by the Division of Chemical Sciences,Geosciences,and Biosciences,Office of Basic Energy Sciences of the US Department of Energy through Grant DEAC0298CH10886the National Science Foundation through grant MCB-1051675(CJL)X27A is supported in part by the U.S.Department of Energy--Geosciences(DE-FG02-92ER14244 to The University of Chicago-CARS)Use of the NSLS was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-98CH10886
文摘Liberty State Park in New Jersey,USA,is a ＂brownfield＂ site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season（May–September）in 2011 at two sites with the high and low metal loads,respectively.The objective of this study was to understand the metal（Fe,Mn,Cu,Pb and Zn）concentration and spatial distributions in P.australis and T.latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence（μXRF）and synchrotron X-ray computed microtomography（μCMT）techniques.The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis.Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different.Significant correlations were found between metals（Cu,Mn,Pb and Zn）and Fe in the epidermis,implying that metals were scavenged by Fe oxides.The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific.The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.
文摘The relationship between soil variables and forest productivity of Eucalyptus urophylla (Eu) and E. grandis (Eg) was studied in commercial forest plantations (CFP) in Huimanguillo, Tabasco, Mexico. The group of Eu included seed and clone raised plantations and the Eg group included only seed raised plantations. Tree measurements and soil sampling were carried out at 56 500-m2 plots. Two soil depths (0 - 20 and 20 - 40 cm) were sampled and analyzed for physical and chemical properties. Site Index (SI), calculated at year 14 was used as indicator of forest productivity. Simple correlation, multiple and second order regressions were used to test the effect of soil variables on productivity. Results showed that mean annual increments (MAI) of Eu and Eg were comparable to other regions of the world reaching 49 m3·ha-1·y-1 across a range of low to high soil fertility gradient (15 to 80 m3·ha-1·y-1). For both species, regardless of the production method (seed or clone), soil texture was the most relevant variable to explain variation in productivity. Eu productivity was correlated to exchangeable Mg (0.3) and Al (0.3) in the 0 - 20 cm soil depth and CEC (0.4) and exchangeable Al (0.6) in the 20 - 40 cm soil depth. Compared to clone plantations, seed plantations showed higher correlations between soils properties and productivity. Aluminum saturation was negatively related to Eg productivity. The highest correlation between soil and productivity were found for Eg, with soil P-availability and aluminum saturation explaining 82 and 85% of the variation, respectively. This works shows that low fertility soils, previously used as pasturelands can be productive for forest plantation purposes and contribute to carbon sequestration.
基金Research was funded in part by the Environmental Stewardship Division,Los Alamos National Laboratory and the Espanola Ranger District,Santa Fe National Forest,US Forest Service.
文摘Aims Recognizing ungulate browsing thresholds between viable and declining aspen(Populus tremuloides Michx.)stands are critical to ensuring long-term persistence of this biologically important plant community.Studies have shown declines in vigor and regeneration when as few as 30%of current annual twigs are browsed while other studies have shown higher limits.Although the effects of ungulate herbivory are of concern in aspen forests,few studies have assessed browsing effects following wildfire and few criteria exist for deter-mining potential effects of ungulate browsing on aspen forests fol-lowing wildfire.We evaluated the effects of ungulate abundance and foraging intensity on regenerating aspen 1 to 6 years post-fire and assessed the use of abundance and foraging intensity indicators in predicting impacts to regenerating aspen.Rocky Mountain elk(Cervus elaphus nelson)was the primary ungulate in the study area.Methods The study area was located within the 17500 ha cerro Grande Fire burn area in the Jemez Mountains,New Mexico,USA.We used percent aspen twigs browsed and pellet-group counts to evaluate relationships between these indicators and aspen patch structure(height,size).We collected data in randomly generated 3×33 m plots 5-6 years post-fire.We also established 4 fenced exclosures(25×55 m and 3.3 m in height)with paired unfenced plots 1-year post-fire to monitor aspen regeneration.Each spring,we recorded percent browsed twigs from the previous fall through the early spring period which coincided with the highest ungulate use period within the study area.We assessed associations between percent twigs browsed and pellet-group density and patch size and height of aspen using Spearman’s correlation coefficients.Important Findings Mean percent twigs browsed and ungulate pellet-group density across the burn area was≤31%and 1 pellet-group 100 sq m−1,respectively.Patch size and height decreased with increasing browsing and pellet-group density 5-6 years post-fire.However,mean aspen heights were approaching or exceeding a minimum browsing level of 2 m and,therefore,ungulate browsing did not appear sufficient to cause signif-icant impacts to aspen across the burn area.We observed a positive correlation between pellet-group density and twig browsing suggest-ing that one or both measures could be used to assess potential effects of browsing on regenerating aspen following fire.
