Context Forests in the northeastern United States are currently in early-and mid-successional sta... more Context Forests in the northeastern United States are currently in early-and mid-successional stages recovering from historical land use. Climate change will affect forest distribution and structure and have important implications for biodiversity, carbon dynamics, and human well-being. Objective We addressed how aboveground biomass (AGB) and tree species distribution changed under multiple climate change scenarios (PCM B1, CGCM A2, and GFDL A1FI) in northeastern forests. Methods We used the LANDIS PRO forest landscape model to simulate forest succession and tree harvest under current climate and three climate change scenarios from 2000 to 2300. We analyzed the effects of climate change on AGB and tree species distribution. Results AGB increased from 2000 to 2120 irrespective of climate scenario, followed by slight decline, but then increased again to 2300. AGB averaged 10 % greater in the CGCM A2 and GFDL A1FI scenarios than the PCM B1 and current climate scenarios. Climate change effects on tree species distribution were not evident from 2000 to 2100 but by 2300 some northern hardwood and conifer species decreased in occurrence and some central hard-wood and southern tree species increased in occurrence. Conclusions Climate change had positive effects on forest biomass under the two climate scenarios with greatest warming but the patterns in AGB over time were similar among climate scenarios because succession was the primary driver of AGB dynamics. Our approach, which simulated stand dynamics and dispersal , demonstrated that a northward shift in tree species distributions may take 300 or more years.
Context Species distribution models (SDM) establish statistical relationships between the current... more Context Species distribution models (SDM) establish statistical relationships between the current distribution of species and key attributes whereas process-based models simulate ecosystem and tree species dynamics based on representations of physical and biological processes. TreeAtlas, which uses DISTRIB SDM, and Linkages and LANDIS PRO, process-based ecosystem and landscape models, respectively, were used concurrently on four regional climate change assessments in the eastern Unites States. Objectives We compared predictions for 30 species from TreeAtlas, Linkages, and LANDIS PRO, using two climate change scenarios on four regions, to derive a more robust assessment of species change in response to climate change. Methods We calculated the ratio of future importance or biomass to current for each species, then compared agreement among models by species, region, and climate scenario using change classes, an ordinal agreement score, spearman rank correlations, and model averaged change ratios. Results Comparisons indicated high agreement for many species, especially northern species modeled to lose habitat. TreeAtlas and Linkages agreed the most but each also agreed with many species outputs from
Context Forest landscape models (FLMs) are important tools for simulating forest changes over bro... more Context Forest landscape models (FLMs) are important tools for simulating forest changes over broad spatial and temporal scales. The ability of FLMs to accurately predict forest changes may be significantly influenced by the formulations of site-scale processes including seedling establishment, tree growth, competition, and mortality. Objective The objectives of this study were to investigate the effects of site-scale processes and interaction effects of site-scale processes and harvest on landscape-scale forest change predictions. Methods We compared the differences in species' distribution (quantified by species' percent area), total aboveground biomass, and species' biomass derived from two FLMs: (1) a model that explicitly incorporates stand density and size for each species age cohort (LANDIS PRO), and (2) a model that explicitly tracks biomass for each species age cohort (LANDIS-II with biomass succession extension), which are variants from the LANDIS FLM family with different formulations of site-scale processes. Results For early successional species, the differences in simulated distribution and biomass were small (mostly less than 5 %). For mid-to late-successional species, the differences in simulated distribution and biomass were relatively large (10–30 %). The differences in species' biomass predictions were generally larger than those for species' distribution predictions. Harvest mediated the differences on landscape-scale predictions. Conclusions The effects of site-scale processes on landscape-scale forest change predictions are dependent on species' ecological traits such as shade tolerance, seed dispersal, and growth rates.
—Oak decline has been a problem in forests of the Ozark Highlands (OzH) for decades. It has impac... more —Oak decline has been a problem in forests of the Ozark Highlands (OzH) for decades. It has impacted upland oak-hickory forests, particularly species in the red oak group (Quercus section Lobatae) across the Ozark Highlands of Missouri, Arkansas, and Oklahoma. The oak decline complex is often described in terms of predisposing factors, inciting factors, and contributing factors. Drought is a common inciting factor in oak decline, while advanced tree age is considered a predisposing factor, and opportunistic organisms such as armillaria root fungi and wood boring insects are believed to contribute to the decline and demise of formerly stressed trees. Declining trees are initially indicated by foliage wilt and browning followed by progressive branch dieback. If crown dieback continues, trees can die. In this paper we synthesize four of our key research studies on oak decline, examining the occurrence, distribution, and characteristics of oak decline as it has impacted the OzH across space and time. Long-term climate forecasts for this region indicate decreasing precipitation and warming temperatures. Consequently, periodic droughts such as the widespread 2012 U.S. drought are expected to increase in frequency and intensity, and thereby exacerbate oak decline on millions of hectares of aging oak forests. Results from our research indicate that regular monitoring of forest conditions; increasing the proportion of species in the white oak relative to the red oak group; judicious application of prescribed fire; periodic thinning to favor species in the white oak group; and proactive harvest of aging red oak species anticipated to be at increased risk of mortality are methods that can help forest managers mitigate oak decline.
Context Forests in the northeastern United States are currently in early-and mid-successional sta... more Context Forests in the northeastern United States are currently in early-and mid-successional stages recovering from historical land use. Climate change will affect forest distribution and structure and have important implications for biodiversity, carbon dynamics, and human well-being. Objective We addressed how aboveground biomass (AGB) and tree species distribution changed under multiple climate change scenarios (PCM B1, CGCM A2, and GFDL A1FI) in northeastern forests. Methods We used the LANDIS PRO forest landscape model to simulate forest succession and tree harvest under current climate and three climate change scenarios from 2000 to 2300. We analyzed the effects of climate change on AGB and tree species distribution. Results AGB increased from 2000 to 2120 irrespective of climate scenario, followed by slight decline, but then increased again to 2300. AGB averaged 10 % greater in the CGCM A2 and GFDL A1FI scenarios than the PCM B1 and current climate scenarios. Climate change effects on tree species distribution were not evident from 2000 to 2100 but by 2300 some northern hardwood and conifer species decreased in occurrence and some central hard-wood and southern tree species increased in occurrence. Conclusions Climate change had positive effects on forest biomass under the two climate scenarios with greatest warming but the patterns in AGB over time were similar among climate scenarios because succession was the primary driver of AGB dynamics. Our approach, which simulated stand dynamics and dispersal , demonstrated that a northward shift in tree species distributions may take 300 or more years.
Context Species distribution models (SDM) establish statistical relationships between the current... more Context Species distribution models (SDM) establish statistical relationships between the current distribution of species and key attributes whereas process-based models simulate ecosystem and tree species dynamics based on representations of physical and biological processes. TreeAtlas, which uses DISTRIB SDM, and Linkages and LANDIS PRO, process-based ecosystem and landscape models, respectively, were used concurrently on four regional climate change assessments in the eastern Unites States. Objectives We compared predictions for 30 species from TreeAtlas, Linkages, and LANDIS PRO, using two climate change scenarios on four regions, to derive a more robust assessment of species change in response to climate change. Methods We calculated the ratio of future importance or biomass to current for each species, then compared agreement among models by species, region, and climate scenario using change classes, an ordinal agreement score, spearman rank correlations, and model averaged change ratios. Results Comparisons indicated high agreement for many species, especially northern species modeled to lose habitat. TreeAtlas and Linkages agreed the most but each also agreed with many species outputs from
Context Forest landscape models (FLMs) are important tools for simulating forest changes over bro... more Context Forest landscape models (FLMs) are important tools for simulating forest changes over broad spatial and temporal scales. The ability of FLMs to accurately predict forest changes may be significantly influenced by the formulations of site-scale processes including seedling establishment, tree growth, competition, and mortality. Objective The objectives of this study were to investigate the effects of site-scale processes and interaction effects of site-scale processes and harvest on landscape-scale forest change predictions. Methods We compared the differences in species' distribution (quantified by species' percent area), total aboveground biomass, and species' biomass derived from two FLMs: (1) a model that explicitly incorporates stand density and size for each species age cohort (LANDIS PRO), and (2) a model that explicitly tracks biomass for each species age cohort (LANDIS-II with biomass succession extension), which are variants from the LANDIS FLM family with different formulations of site-scale processes. Results For early successional species, the differences in simulated distribution and biomass were small (mostly less than 5 %). For mid-to late-successional species, the differences in simulated distribution and biomass were relatively large (10–30 %). The differences in species' biomass predictions were generally larger than those for species' distribution predictions. Harvest mediated the differences on landscape-scale predictions. Conclusions The effects of site-scale processes on landscape-scale forest change predictions are dependent on species' ecological traits such as shade tolerance, seed dispersal, and growth rates.
—Oak decline has been a problem in forests of the Ozark Highlands (OzH) for decades. It has impac... more —Oak decline has been a problem in forests of the Ozark Highlands (OzH) for decades. It has impacted upland oak-hickory forests, particularly species in the red oak group (Quercus section Lobatae) across the Ozark Highlands of Missouri, Arkansas, and Oklahoma. The oak decline complex is often described in terms of predisposing factors, inciting factors, and contributing factors. Drought is a common inciting factor in oak decline, while advanced tree age is considered a predisposing factor, and opportunistic organisms such as armillaria root fungi and wood boring insects are believed to contribute to the decline and demise of formerly stressed trees. Declining trees are initially indicated by foliage wilt and browning followed by progressive branch dieback. If crown dieback continues, trees can die. In this paper we synthesize four of our key research studies on oak decline, examining the occurrence, distribution, and characteristics of oak decline as it has impacted the OzH across space and time. Long-term climate forecasts for this region indicate decreasing precipitation and warming temperatures. Consequently, periodic droughts such as the widespread 2012 U.S. drought are expected to increase in frequency and intensity, and thereby exacerbate oak decline on millions of hectares of aging oak forests. Results from our research indicate that regular monitoring of forest conditions; increasing the proportion of species in the white oak relative to the red oak group; judicious application of prescribed fire; periodic thinning to favor species in the white oak group; and proactive harvest of aging red oak species anticipated to be at increased risk of mortality are methods that can help forest managers mitigate oak decline.
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