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Souza L.,Oak Ridge National Laboratory | Souza L.,University of Tennessee at Knoxville | Belote R.T.,Wilderness Society | Kardol P.,Oak Ridge National Laboratory | And 2 more authors.
Journal of Plant Ecology | Year: 2010

Aims Rising concentrations of atmospheric carbon dioxide ([CO2]) may influence forest successional development and species composition of understory plant communities by altering biomass production of plant species of functional groups. Here, we describe how elevated [CO2] (eCO 2) affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility in eastern Tennessee, USA. We asked if (i) CO2 enrichment affected total understory biomass and (ii) whether total biomass responses could be explained by changes in understory species composition or changes in relative abundance of functional groups through time. Materials and methods The FACE experiment started in 1998 with three rings receiving ambient [CO2] (aCO 2) and two rings receiving eCO2. From 2001 to 2003, we estimated species-specific, woody versus herbaceous and total aboveground biomass by harvesting four 1 × 0.5-m subplots within the established understory plant community in each FACE plot. In 2008, we estimated herbaceous biomass as previously but used allometric relationships to estimate woody biomass across two 5 × 5-m quadrats in each FACE plot. Important findings Across years, aboveground biomass of the understory community was on average 25% greater in eCO2 than in aCO2 plots. We could not detect differences in plant species composition between aCO2 and eCO 2 treatments. However, we did observe shifts in the relative abundance of plant functional groups, which reflect important structural changes in the understory community. In 2001-03, little of the understory biomass was in woody species; herbaceous species made up 94% of the total understory biomass across [CO2] treatments. Through time, woody species increased in importance, mostly in eCO2, and in 2008, the contribution of herbaceous species to total understory biomass was 61% in aCO2 and only 33% in eCO2 treatments. Our results suggest that rising atmospheric [CO 2] could accelerate successional development and have longer term impact on forest dynamics.

Eichman H.,USFS TEAMS Enterprise | Hunt G.L.,University of Maine, United States | Kerkvliet J.,Wilderness Society | Plantinga A.J.,Oregon State University
Journal of Agricultural and Resource Economics | Year: 2010

Debates over protecting public land reveal two views. Some argue protection reduces commodity production, reducing local employment and increasing out-migration. Others contend protection produces amenities that support job growth and attract migrants. We test these competing views for the Northwest Forest Plan (NWFP), which reallocated 11 million acres of federal land from timber production to protecting old-growth forest species. We find evidence that land protection directly reduced local employment growth and increased net migration. The total negative effect on employment was offset only slightly by positive migration-driven effects. Employment losses were concentrated in metropolitan counties, but percentage losses were higher in rural counties. Copyright 2010 western agricultural Economics Association.

Belote R.T.,Wilderness Society | Belote R.T.,Virginia Polytechnic Institute and State University | Jones R.H.,Virginia Polytechnic Institute and State University | Jones R.H.,West Virginia University | Wieboldt T.F.,Virginia Polytechnic Institute and State University
Ecological Applications | Year: 2012

Human-caused changes in disturbance regimes and introductions of nonnative species have the potential to result in widespread, directional changes in forest community structure. The degree that plant community composition persists or changes following disturbances depends on the balance between local extirpation and colonization by new species, including nonnatives. In this study, we examined species losses and gains, and entry of native vs. exotic species to determine how oak forests in the Appalachian Mountains might shift in species composition following a gradient of pulse disturbances (timber harvesting). We asked (1) how compositional stability of the plant community (resistance and resilience) was influenced by disturbance intensity, (2) whether community responses were driven by extirpation or colonization of species, and (3) how disturbance intensity influenced total and functional group diversity, including the nonnative proportion of the flora through time. We collected data at three spatial scales and three times, including just before, one year postdisturbance, and 10 years post-disturbance. Resistance was estimated using community distance measures between pre-and one year post-disturbance, and resilience using community distance between pre-and 10-year post-disturbance conditions. The number of colonizing and extirpated species between sampling times was analyzed for all species combined and for six functional groups. Resistance and resilience decreased with increasing timber-harvesting disturbance; compositional stability was lower in the most disturbed plots, which was driven by colonization, but not extirpation, of species. Colonization of species also led to increases in diversity after disturbance that was typically maintained after 10 years following disturbance. Most of the community-level responses were driven by postdisturbance colonization of native forbs and graminoids. The nonnative proportion of plant species tended to increase following disturbance, especially at large spatial scales in the most disturbed treatments, but tended to decrease through time following disturbance due to canopy development. The results of this study are consistent with the theory that resources released by disturbance have strong influences on species colonization and community composition. The effects of management activities tested in this study, which span a gradient of timber-harvesting disturbance, shift species composition largely via an increase in species colonization and diversity. © 2012 by the Ecological Society of America.

Joshi O.,Mississippi State University | Grebner D.L.,Mississippi State University | Hussain A.,Wilderness Society | Grado S.C.,Mississippi State University
Journal of Forest Economics | Year: 2013

Nonindustrial private forest (NIPF) landowners' willingness to harvest woody biomass for wood-based bioenergy is important if sustainable feedstock supplies are to be realized in the U.S. However, a significant number of them do not know that unused logging residues could be used to produce wood-based bioenergy. Therefore, this study analyzed landowner willingness to harvest woody biomass in Mississippi contingent upon their knowledge of wood-based bioenergy. The requisite data were analyzed in accordance with the Heckman approach. Results indicated that elderly, male, and resident landowners, having larger tracts of pine plantations were more likely to be aware of wood-based bioenergy. The results further revealed the need for bioenergy related extension education focusing on female landowners and those having small tracts of forest land. © 2012 Department of Forest Economics, Swedish University of Agricultural Sciences, Umeå.

McAfee S.A.,Wilderness Society | McAfee S.A.,University of Alaska Fairbanks | McAfee S.A.,University of Nevada, Reno | Guentchev G.,University Corporation for Atmospheric Research | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013

Numerous studies have evaluated precipitation trends in Alaska and come to different conclusions. These studies differ in analysis period and methodology and do not address the issue of temporal homogeneity. To reconcile these conflicting results, we selected 29 stations with largely complete monthly records, screened them for homogeneity, and then evaluated trend over two analysis periods (1950-2010 and 1980-2010) using three methods: least absolute deviation regression, ordinary least squares regression (with and without transformation), and Mann-Kendall trend testing following removal of first-order autocorrelation. We found that differences in analytical period had a significant impact on trends and that the presence of inhomogeneities or step changes also posed a substantial challenge in detecting reliable long-term trends in precipitation over Alaska, particularly in the southern part of the state. Although some of these inhomogeneities occur in the mid-1970s and could be associated with well-documented changes in the Pacific Ocean and the Aleutian Low at that time, many of the inhomogeneities co-occur with changes in station location, instrumentation, or operation. These operationally induced changes make it difficult to accurately detect the impact of decadal to multidecadal climate variability on precipitation amounts and to assess historical precipitation trends in Alaska. Key Points Inhomogeneities complicate precipitation trend analysis in Alaska There are few robust trends in Alaskan precipitation Different trend detection methods produced similar results ©2013. American Geophysical Union. All Rights Reserved.

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