Evidence-based forest carbon (C) management requires identifying baseline patterns and drivers of soil organic carbon (SOC) stocks, and their responses to land use change and management, at scales relevant to landowners and resource professionals. The growth of datasets related to SOC, which is the largest terrestrial C pool, facilitates use of synthesis techniques to assess SOC stocks and changes at management-relevant scales. We report results from a synthesis using meta-analysis of published studies, as well as two large databases, in which we identify baseline patterns and drivers, quantify influences of land use change and forest management, and provide ecological context for distinct management regimes and their SOC impacts. We conducted this, the fourth in a series of ecoregional SOC assessments, for the South Atlantic States, which are disproportionately important to the national-scale forest C sink and forest products industry in the U.S. At the ecoregional level, baseline SOC stocks vary with climatic, topographic, and soil physical factors such as temperature and precipitation , slope gradient and aspect, and soil texture. Land use change and forest management modestly influence SOC stocks. Reforestation on previously cultivated lands increases SOC stocks, while deforestation for cultivation has the opposite effect; for continuously forested lands, harvesting is associated with SOC increases and prescribed fire with SOC declines. Effects of reforestation are large and positive for upper mineral soils (+30%) but not detectable in lower mineral soils. Negative effects of prescribed fire are due to significant C losses from organic horizons (-46%); fire and harvest have no impacts on upper mineral soils but both increase SOC in lower mineral soils (+8.2 and +46%, respectively, with high uncertainty in the latter). Inceptisols are generally more negatively impacted by prescribed fire or harvest than Ultisols, and covariance between inherent factors (including soil taxonomy) and management impacts indicates how interior vs. coastal physiographic sections differ in their management regimes and SOC trends. In the cooler, wetter, topographically rugged interior hardwood forests, which have larger baseline SOC stocks, prescribed fire and even light harvesting generally decrease SOC; in contrast, intensively managed coastal plain pine plantations begin with small initial SOC stocks, but exhibit rapid gains over even a single rotation. This covariance between place (physiography) and practice (management regime) suggests that distinct approaches to forest C management may be complementary to other ecological or production goals, when implemented as part of wider (e.g., state-level) forest C or climate policy.
While resilience is defined differentially by social scientists and ecologists, sustainability is possible where resilient social and ecological systems meet and interact, and sustainable resilient systems promote societal use of ecosystem services supporting contemporary societal needs without risk to future generations. Yet it is possible for seemingly appropriate and rational decisions from individuals, and society at large, to be counter to long-term sustainable solutions. Historic rice field cultivation in the wetlands of the Carolinas and Florida provides an example of various forms of resilience and sustainability within the theoretical framework of alternate stable states, whereby a resilient system can exist in more than one state and where stability is achieved when disruptive variables are not so disruptive as to generate tipping points from one state to another. This contribution examines the changing role and political as well as environmental impacts of rice agriculture in the region with particular emphasis on the contingent processes of environmental and cultural transformation that took place between the seventeenth and twenty-first centuries.
Carbon (C)‐informed forest management requires understanding how disturbance and management influence soil organic carbon (SOC) stocks at scales relevant to landowners, forest policy and management professionals. The continued growth of datasets and publications allows powerful synthesis approaches to be applied to such questions at increasingly fine scales. Here, we report results from a synthesis that used meta‐analysis of published studies and two large observational databases to quantify disturbance and management impacts on SOC stocks. We conducted this, the third in a series of ecoregional SOC assessments, for the Pacific Northwest, which comprises ~8% of the land area but ~12% of the U.S. forest sector C sink. At the ecoregional level, our analysis indicated that fundamental patterns of vegetation, climate, and topography are far more important controls on SOC stocks than land use history, disturbance or management. However, the same patterns suggested that increased warming, drying, wildland fire, and forest regeneration failure pose significant risks to SOC stocks across the region. Detailed meta‐analysis results indicated that wildfires diminished SOC stocks throughout the soil profile, while prescribed fire only influenced surface organic materials and harvesting had no significant overall impact on SOC. Independent observational data corroborated the negative influence of fire on SOC derived from meta‐analysis, suggested that harvest impacts may vary sub‐regionally with climate or vegetation, and revealed that forests with agricultural uses (e.g., grazing) or legacies (e.g., cultivation) had smaller SOC stocks. We also quantified effects of a range of common forest management practices having either positive (organic amendments, nitrogen (N)‐fixing vegetation establishment, inorganic N fertilization) or no overall effects on SOC (other inorganic fertilizers, urea fertilization, competition suppression through herbicides). In order to maximize the management applications of our results, we qualified them with ratings of confidence based on degree of support across approaches. Lastly, similar to earlier published assessments from other ecoregions, we supplemented our quantitative synthesis results with a literature review to arrive at a concise set of tactics for adapting management operations to site‐specific criteria.
Water availability and other site conditions influence poplar biomass productivity and affect clonal performance due to genotype × environment interactions. It is important to select genotypes with high water use efficiency (WUE) that maximize yield with available amounts of water at sites, while avoiding drought stress and growth impacts to the trees. During drought, stomatal closure induces increased accumulation of δ¹³C carbon isotope in tree tissues, which is strongly correlated with WUE of trees and usually expressed through carbon isotope discrimination (Δ). Our primary objectives were to evaluate differences in WUE among poplar genotypes grown in the Midwestern United States, and to identify genotypes with high WUE for future deployment on water-limited sites in the region. Sites included 10-year-old biomass plantations in Escanaba, Michigan; Waseca, Minnesota; and Ames, Iowa established from 2000 to 2001 with seven poplar genotypes three genomic groups. Following harvest, height, diameter, and biomass were determined. Wood samples were collected from individual growth rings to assess annual ring width and WUE through δ¹³C and Δ. Aboveground dry biomass varied among sites (P = 0.0007), clones (P < 0.0001), and their interactions (P = 0.0134), ranging from 3.1 to 14.0 Mg ha⁻¹ yr⁻¹. Δ varied among sites (Δ = 18.9 to 19.7 ‰; P < 0.0001) and clones (Δ = 18.6 to 19.9 ‰; P < 0.0001), indicating effects of site conditions on WUE of tested genotypes. Clones varied in their water-conserving strategies. Some clones were characterized as water consumers with high growth and high WUE ('C916000'; 'C916400'), while other genotypes were water conservers using lower amounts of water with moderate biomass production ('NC13624'; 'NC13649'; ‘NM2’ to a certain extent). Although δ¹³C carbon isotope accumulation correlates with WUE, ∆ should only be used for selection when it is integrated with other parameters such as productivity, soils information, and climate data.
Establishing commercial tree plantations in native grassland ecosystems introduces a different structural and functional vegetation cover type, with expected implications for biodiversity. To better understand biodiversity responses to afforestation, we conducted a resource-use study with birds as a focal group, during the 2013-2014 breeding season in the Northern Campos grasslands of Uruguay. We sampled birds in native environments and plantations of loblolly pine (Pinus taeda) and flooded gum (Eucalyptus grandis) at different rotation stages. We recorded 103 species during 1,573 visits (10-min, 50-meter radius point counts) to 570 stratified sampling units. Native grasslands and forests exhibited greater diversity and had greater variability in species composition than structurally homogeneous plantations. Avian communities in plantations had distinct species combinations and relative abundances not found in native conditions. Avian communities in older plantations were more similar to native forests while those of newly-planted stands were more like grasslands. However, plantations were dominated by habitat generalists and some forest-dependent species, with negligible use by grassland specialist birds. Our results suggest the best conservation opportunities for grassland-dependent birds in afforested systems of the Campos of Uruguay may depend on diverse landscape-level measures rather than stand-level management practices. Albeit our research constituted a comprehensive assessment of bird taxonomic alpha and beta diversity , research on complementary diversity facets and multi-scale resource selection and demographic studies are needed to better understand the fitness implications for conserving and managing grassland birds in affor-ested landscapes.
We implemented a unique tree-climbing effort to examine nesting-habitat selection of Marbled Murrelets (Brachyramphus marmoratus) in managed forest stands of Washington and Oregon during 1996-1999. Researchers climbed over 3000 trees to search for old and active murrelet nests during the breeding season (May-Sept.) in a random sample of stands known to be occupied by murrelets. Within these stands, characteristics of murrelet nest sites and non-nest sites were measured at three fine spatial scales: nest limb or platform, nest tree, and nest-site or forest patch (0.5 ha). We report results of a Bayesian hierarchical logistic regression model using three covariates at each of the three fine spatial scales. All three branch/platform scale covariates positively predicted nest occupancy with higher probabilities of nesting occurring at branches/platforms with higher horizontal cover, larger platform diameters, and higher moss cover. Tree scale characteristics associated with higher probabilities of nesting included higher platform counts and higher moss depth. Effect of tree diameter on probability of nesting was unclear. At the patch scale, lower probability of nesting occurred for stands with higher densities of trees with platforms. This unexpected relationship may be due in part to decreasing likelihood of observing a nest on a given platform when there are more platforms in a patch. Variation in tree size and percent canopy cover at the patch scale showed no clear association with nest selection at the patch scale. The prevalence of nests in Dwarf Mistletoe-infected hemlock trees may have partially obfuscated the effect of tree diameter on probability of encountering a nest in portions of our study area. Fine scale conservation efforts for Marbled Murrelets may include recruiting or retaining trees with larger numbers of platforms, large branches with high percentages of moss cover and horizontal cover, and younger trees with platforms created by Dwarf Mistletoe deformities.
Abstract Timber harvesting can influence headwater streams by altering stream productivity, with cascading effects on the food web and predators within, including stream salamanders. Although studies have examined shifts in salamander occupancy or abundance following timber harvest, few examine sublethal effects such as changes in growth and demography. To examine the effect of upland harvesting on growth of the stream‐associated Ouachita dusky salamander (Desmognathus brimleyorum), we used capture–mark–recapture over three years at three headwater streams embedded in intensely managed pine forests in west‐central Arkansas. The pine stands surrounding two of the streams were harvested, with retention of a 14‐ and 21‐m‐wide forested stream buffer on each side of the stream, whereas the third stream was an unharvested control. At the two treatment sites, measurements of newly metamorphosed salamanders were on average 4.0 and 5.7 mm larger post‐harvest compared with pre‐harvest. We next assessed the influence of timber harvest on growth of post‐metamorphic salamanders with a hierarchical von Bertalanffy growth model that included an effect of harvest on growth rate. Using measurements from 839 individual D. brimleyorum recaptured between 1 and 6 times (total captures, n = 1229), we found growth rates to be 40% higher post‐harvest. Our study is among the first to examine responses of individual stream salamanders to timber harvesting, and we discuss mechanisms that may be responsible for observed shifts in growth. Our results suggest timber harvest that includes retention of a riparian buffer (i.e., streamside management zone) may have short‐term positive effects on juvenile stream salamander growth, potentially offsetting negative sublethal effects associated with harvest.
The effect of silvicultural treatments (herbicide, fertilization, herbicide + fertilization) and the interactions with genetic effects were investigated for wood quality traits in a 16-year-old loblolly pine (Pinus taeda L.) genetic test established in southwest Georgia, USA. Fertilizer and herbicide treatment combinations were applied multiple times to main plots containing 25 open-pollinated families as sub plots. Significant differences among treatments were found for all traits. Squared acoustic velocity, used as a surrogate for wood stiffness, was higher in herbicide-only plots compared with other treatments. Wood density was considerably lower in fertilization plots. A large proportion of variance observed for wood quality traits was explained by additive genetic effects, with individual-tree heritabilities ranging from 0.78 (ring 7–16 section wood density) to 0.28 (ring 2–6 section wood density). Corresponding family-mean heritability values were well over 0.86. Genotype-by-treatment interactions were nonsignificant for all traits, indicating no need to match families to silvicultural treatments. Wood quality traits had weak genetic correlations with growth and stem quality traits (stem slenderness, sweep, and branch angle) with a range of −0.33 to 0.43, suggesting that recurrent selection on growth or stem quality traits would not adversely affect wood quality in loblolly pine.
The private forestry sector faces enormous challenges from complex environmental issues concurrent with societal concerns about intensive forest management and application of silvicultural tools. At the same time, research and development spending and the scientific workforce in the forestry sector has declined. However, the forestry sector has a long history of strategic deployment of science and technology to manage timberlands for many uses, including ecological services. To address science and societal needs from future forests, we describe past successes and potential future innovations of the forestry sector across (1) genetics, (2) silviculture and productivity, (3) harvesting and logging technology, (4) environmental sustainability, and (5) remote sensing and unmanned aerial vehicles. Developing technology is only one component, however; progressing towards sector goals of diversifying the workforce, explicitly valuing research collaborations, and integrating big data across ownerships to guide management decisions will hasten innovation. With the growing complexity of social-ecological-economic challenges, the private forestry sector must enact a tactical approach to addressing stressors with evolving research structures. We offer a vision of a vibrant private forestry sector poised to integrate technological innovation to continue meeting society’s needs through the intersecting effects of climate change and other challenges. Study Implications The complexity of challenges facing private forest managers is growing as stressors from climate change interact with social and economic pressures on forests. Further, spending on forestry research and development and student enrollment in forestry degree programs has declined. In this article, we describe significant technological improvements in regenerating, growing, and sustainably harvesting intensively managed forest through a changing research landscape. We review key past examples of production and sustainability improvements and describe future innovation space across the intensively managed conifer stands through the life cycle of seed-to-saw. We envision that technological improvements in forest genetics, remotely operated harvesting equipment, high-resolution information about vegetation and the earth’s surface, and analysis of big data will increase the private sector’s ability to make precise management decisions. A more developed and broader technological tool set will ensure the private forest sector is poised to supply ecosystem services and demand for wood products. To realize the gains from future innovation, the forest sector needs to support initiatives that explicitly value an inclusive and diverse workforce, cross-disciplinary problem-solving, and improved communication with external stakeholders.
In young Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stands, intensive forest management has resulted in variable responses in survival and growth and therefore stand biomass due to effects on microclimate and competition for limited resources. As seedling genetics and management practices develop over time, there is a need to re-evaluate how Douglas-fir survival and growth varies with intensive practices. Five-year Douglas-fir diameter at 15 cm (D15) and height growth, biomass, and nitrogen (N) pools after organic matter removals and soil compaction at a recently established site in central Oregon (NARA) were compared to five-year results from three Douglas-fir sites with organic matter removal and vegetation control treatments that were established 10-14 years earlier in central Washington (Fall River and Matlock) and northern Oregon (Molalla). The NARA site contained up to two times greater individual-tree foliar and branch biomass for the same stem D15 than the previously established sites, possibly due to a lower planting density, a warmer climate, and/or improved ge-netics/different seed sources. Prediction of stem biomass was similar at all sites using D15 2 *height. Periodic D15 and height growth from 1 to 3 years and five-year Douglas-fir biomass was lower in the bole-only (BO) without compaction treatment at NARA compared to other treatment combinations. Greater periodic D15 and height growth after five years of annual vegetation control (Fall River, Matlock, and Molalla) resulted in larger Douglas-fir biomass compared to the initial vegetation control treatments. These results indicate the beneficial effects of vegetation control on early growth across a wide range of conditions. With one exception, whole-tree removal treatments did not affect five-year-old Douglas-fir biomass or N pools, indicating site resilience to increased OM removal across the region. A principal component analysis (PCA) clearly separated all four sites according to climate, soil temperature and moisture, N availability, D15 and height growth, and Douglas-fir and competing vegetation biomass. Within each site, the PCA showed that vegetation control was associated with the greatest differences in Douglas-fir and competing vegetation biomass. This supports the notion that site factors and vegetation control treatments are critically important in mitigating response to intensive management practices.
Understanding how land‐management intensification shapes the relationships between biodiversity, yield and economic benefit is critical for managing natural resources. Yet, manipulative experiments that test how herbicides affect these relationships are scarce, particularly in forest ecosystems where considerable time lags exist between harvest revenue and initial investments. We assessed these relationships by combining 7 years of biodiversity surveys (>800 taxa) and forecasts of timber yield and economic return from a replicated, large‐scale experiment that manipulated herbicide application intensity in operational timber plantations. Herbicides reduced species richness across trophic groups (‐18%), but responses by higher‐level trophic groups were more variable (0–38% reduction) than plant responses (‐40%). Financial discounting, a conventional economic method to standardize past and future cashflows, strongly modified biodiversity‐revenue relationships caused by management intensity. Despite a projected 28% timber yield gain with herbicides, biodiversity‐revenue tradeoffs were muted when opportunity costs were high (i.e., economic discount rates ≥7%). Although herbicides can drive biodiversity‐yield tradeoffs, under certain conditions, financial discounting provides opportunities to reconcile biodiversity conservation with revenue.
We employed a systematic evidence review to evaluate empirical scientific evidence for the effectiveness of buffering headwater (typically non-fish-bearing) streams to maintain stream temperature and stream-associated amphibian populations in the Pacific Northwest of Canada and the United States. To address our synthesis objective, we identified thirteen temperature, seven amphibian, and two temperature/amphibian primary research studies that met objective inclusion criteria. We evaluated external validity for how study treatments inform or were linked to causal factors influencing temperature response (a) and how the sampled population represented or provided inference to an intended target population or landscape (b). The evidence indicated substantial variability in the temperature response to streamside buffers. The effect size for the mean 7-day maximum temperature metric showed a positive association when comparing no-buffers (clearcut) to treatments with wide buffers (≥30 m). However, this effect varied substantially and overlap existed in effect sizes among no-cut buffers, no-cut plus variable retention buffers, and no-cut patch buffers all ≤20 m wide. Large variability in effect size among treatments obscured any potential trend between effect size for the seasonal (summer) mean daily maximum temperature metric and buffer width. Shade was correlated with temperature response within several studies, but direct comparisons of treatment effectiveness among studies as a function of shade was confounded by different measurement methods. The evidence also indicated that variation in temperature response among studies may be associated with multiple factors (geology, hydrology, topography, latitude, and stream azimuth) that influence thermal sensitivity of streams to shade loss. For amphibians, we found mixed evidence for relationships between population responses and buffers maintained along streams after forest harvest. Specifically, we did not find evidence to support the contention that positive population responses are associated consistently with larger buffers. Also, considerable uncertainty exists about which environmental covariates reliably explain variation in amphibian population responses. Collectively, our results indicate that evidence is weak to address questions most relevant to policy discussions concerning effectiveness of alternative riparian management schemes. Future studies should test effectiveness of alternative treatments with either experimental or purposefully structured observational studies to develop tools and derive guidelines for how to achieve management goals based on site and landscape characteristics.
Black-backed Woodpeckers (Picoides arcticus) are widely considered a burned forest specialist across much of their range. Several recent studies have examined their occurrence in "green" coniferous forests that have not been recently burned, but Black-backed Woodpecker occupancy and factors influencing occupancy in these forest types remain largely unexamined. We worked on the east slope of the southern Oregon Cascade Mountains and used playback call surveys with repeated visits to 90 transects in 2014 and 2015 to estimate occupancy probabilities by forest type while controlling for detection probability. We detected Black-backed Woodpeckers on 86% of survey transects in green forests composed primarily of mixed conifer, lodgepole pine (Pinus contorta), or ponderosa pine (P. ponderosa). We examined associations between occupancy probability and structural covariates in unburned forests, and found that occupancy did not vary with annual precipitation, large snag density, or snag basal area. Modeled mean occupancy across all transects was 0.87 (95% CI: 0.78-0.93). Detection probability varied during each survey season, with transect-level detection probability reaching a maximum of 0.79 (95% CI: 0.70-0.85) in mid-June. Given high occupancy of green forests by Black-backed Woodpecker in our study area, we suggest that additional study of vital rates in green forests is critical for supporting conservation and management decisions for this species.
The value of non‐commodity ecosystem services provided by forests is widely recognized, but intensive forest management practices are increasing, with uncertain consequences for a multitude of these services. Quantitative relationships among biodiversity conservation, timber production, and other ecosystem services remain poorly understood, especially during the early successional period of intensively managed forestlands. We manipulated management intensity in regenerating forest plantations to test the prediction that treatments aimed at maximizing timber production decrease biodiversity conservation and non‐timber services. We measured species richness of three taxonomic groups and thirteen proxies for provisioning, cultural, and regulating services within stands randomly‐assigned to one of three herbicide application intensities or an untreated control. Herbicides increased allocation of net primary production to crop trees, increasing projected timber volume and revenues at 40‐ and 60‐year harvest ages. Commonly‐used herbicide prescriptions reduced culturally‐valued plants by 71%, wild‐ungulate forage by 41%, avian richness by 20%, and pollinator floral resources by 42%, the latter being associated with 38% fewer pollinator species. However, agriculturally‐valued bumblebees, pollination of blueberries, avian‐mediated arthropod control, wild ungulate observations, and regulation services tied to forest productivity appeared unaffected by increasing management intensity and timber production. Species richness and flora‐provided services in young forest plantations exhibited strong tradeoffs with projected timber production, whereas post‐treatment vegetation regeneration and site‐level variation likely maintained a range of other services. Although vegetation recovery is important for supporting wildlife and some ecosystem services on industrial forestlands, it is unlikely that any single prescription can optimize both timber and non‐timber benefits to society across managed forest landscapes. Instead, producing different services in discrete portions of the landscape may be necessary. Synthesis and applications. We tested the effects of intensive forest management via herbicides on ecosystem services and found that biodiversity responses and services from early‐successional vegetation trade off against timber production. A number of services appeared to be compatible with timber production, although no single prescription optimized the full range of services. Stand‐level biodiversity conservation and a variety of services could potentially be provided by treatment skips and less‐intensive management on productive sites, although it is unlikely that all services can be optimized without landscape‐level planning.
Tree stocking and the associated canopy closure in production forests is often greater than optimal for wildlife that require an open canopy and the associated understory plant community. Although mid-rotation treatments such as thinning can reduce canopy closure and return sunlight to the forest floor, stimulating understory vegetation, wildlife-focused thinning prescriptions often involve thinning stands to lower tree densities than are typically prescribed for commercial logging operations. Therefore, we quantified the accuracy and precision with which commercial logging crews thinned pre-marked and unmarked mid-rotation loblolly pine (Pinus taeda) stands to residual basal areas of 9 (low), 14 (medium), and 18 (high) m2/ha. Following harvest, observed basal areas were 3.36, 1.58, and 0.6 m2/ha below target basal areas for the high, medium, and low basal area treatments, respectively. Pre-marking stands increased precision, but not accuracy, of thinning operations. We believe the thinning outcomes we observed are sufficient to achieve wildlife objectives in production forests, and that the added expense associated with pre-marking stands to achieve wildlife objectives in production forests depends on focal wildlife species and management objectives.
Long-term poplar phytoremediation data are lacking, especially for ecosystem services throughout rotations. We tested for rotation-age diﬀerences in biomass productivity and carbon storage of clones Populus deltoides Bartr. ex Marsh×P. nigra L. ‘DN340 and P. nigra×P. maximowiczii A. Henry ‘NM60 grown for landﬁll phytoremediation in Rhinelander, WI, USA (45.6◦ N, 89.4◦ W). We evaluated tree height and diameter, carbon isotope discrimination (∆), and phytoaccumulation and phytoextraction of carbon, nitrogen, and inorganic pollutants in leaves, boles, and branches. We measured speciﬁc gravity and ﬁber composition, and determined biofuels recalcitrance of the Rhinelander landﬁll trees versus these genotypes that were grown for biomass production on an agricultural site in Escanaba, MI, USA (45.8◦ N, 87.2◦ W). ‘NM60 exhibited 3.4 times greater biomass productivity and carbon storage than ‘DN340, yet both of the clones had similar ∆, which differed for tree age rather than genotype. Phytoaccumulation and phytoextraction were clone-and tissue-speciﬁc. ‘DN340 generally had higher pollutant concentrations. Across contaminants, stand-level mean annual uptake was 28 to 657% greater for ‘NM60, which indicated its phytoremediation superiority. Site-related factors (not genotypic effects) governed bioconversion potential. Rhinelander phytoremediation trees exhibited 15% greater lignin than Escanaba biomass trees, contributing to 46% lower glucose yield for Rhinelander trees.
Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirbel) Franco) plantation forests of the coastal Pacific Northwest have been intensively managed to improve the yield of forest products. However, the long-term effects of these management techniques have received limited research attention in this region. Three affiliate Long-Term Soil Productivity study sites were installed in Douglas-fir forests to understand the impacts of organic matter removals and vegetation control on soil productivity over time. Matlock and Fall River are located in Washington, USA and Molalla is located in Oregon. Organic matter removal treatments included traditional bole-only harvest (BO), whole tree removals (WT), and a whole tree plus coarse woody debris removal (WT+) (Fall River only). Five years of annual vegetation control (AVC) was compared with a conventional initial vegetation control (IVC) treatment at all sites. Douglas-fir biomass allocation to foliage, branch, and stem components was modeled using 15-to 20-year-old trees from this study along with 5-to 47-year-old trees from previous studies on these sites. Across all sites, model predictions indicated that the WT treatment had 7.1 to 9.7 Mg ha −1 less Douglas-fir biomass than the BO treatment. There was 1.5 to 20.5 Mg ha −1 greater Douglas-fir biomass in the AVC treatment than in the IVC treatment at all sites. Douglas-fir carbon and nitrogen biomass were consistently lower in the WT treatment, but there were no significant changes in overall site nutrient pools. The AVC treatment resulted in greater Douglas-fir nutrient pools yet there was a net loss in site calcium, magnesium, and potassium due to lower forest floor and soil base cation pools. While WT removals did not significantly affect site nutrition, the decrease in Douglas-fir biomass at all sites and increase in invasive Scotch broom (Cytisus scoparius (L.) Link) biomass at Matlock suggests that the standard practice of retaining harvest residuals is beneficial. The use of intensive vegetation control to improve Douglas-fir biomass and nutrition must be balanced with retaining soil base cations.
Commercial thinning and prescribed fire can improve habitat quality for white-tailed deer (Odocoileus virginianus) in lobolly pine (Pinus taeda) stands by increasing coverage of forage plants. However, the relationships among thinning intensity, prescribed fire, and deer forage have not been quantified. We estimated percent cover of deer forage plants in 5 loblolly pine stands thinned to 11 (low), 14 (medium), and 18 (high) m2/ha basal areas during 2017 in Georgia, USA. We applied prescribed fire during 2018. From years 1-2 post-treatment, cover of total deer forage increased 26% and 29% in the low and medium basal area treatments, respectively, compared to 19% in the high basal area treatment. Similarly, the increase in forb coverage was greater for the medium (13%) and low (11%) basal area treatments than the high (6%) basal area treatment. Increases in vine and bramble coverage were greater in unburned medium basal area units. Woody browse was not affected by any treatment. Our results suggest thinning loblolly pine stands to 14 m2/ha can increase coverage of deer forage plants during the first two growing seasons post-thin, but deer forage was not greater in stands thinned to <14 m2/ha two years post-thin.
Soils are a nonrenewable resource that support a wide array of ecosystem functions. The scope of these functions depends on the nature and properties of the soil at a given location on the Earth. Demand for better soil information has been growing since the development of soil science in the nineteenth century. This recent interest is driven by an increasing recognition of the ecological, economic, and societal benefits of understanding soil properties and the value of that knowledge for realizing management objectives for agriculture, grazing, forestry, and other land uses. Soil surveys are one method for amassing soil data and mapping the extent of various soil types. The Federal Government has singularly been a long-term sponsor of soil surveys in the United States. The history of these surveys is richly documented and illustrated by Helms and others (2008). Soil surveys describe horizontal (e.g., soil series) and vertical (e.g., horizon depth) properties of soils. Soil mapping enhances assessments of spatial variability in the development and properties of soils as a function of geology, climate, topography, and vegetation. Extensive sampling of soils in concert with other attributes (e.g., forest or rangeland composition) can provide focused estimates and understanding of the linkages between soils and vegetation growth, mortality, and C stocks (O’Neill et al. 2005) (Box 9.1). Thus, soils are not independent of biogeophysical settings and climate, but rather are a result of these variables. Management interpretations of soil functions and processes such as erosion, potential vegetation growth, and hydrologic function integrate these factors and offer an index for land use limitations and opportunities.
In the present study, we examined the relationships between (1) N, P, total organic carbon (TOC), and total suspended sediment (TSS) each and stream flow and water table elevation, individually (2) N, P, and TOC, each and TSS, and (3) stream water C/N ratios and stream flow in managed pine forests with various switchgrass treatments implemented on four watersheds in coastal North Carolina plain. The treatments included a young pine forest–natural understorey (27.5 ha), a young pine forest with switchgrass intercropped between pine rows replacing natural understorey (IC) (26.3 ha), a mature thinned pine forest (25.9 ha), and pure switchgrass (27.1 ha). Precipitation, flow, water table elevation, N, phosphate, TOC, and TSS concentrations were measured from November 2009 to June 2014 (switchgrass growth from May 2012 after site preparation (SP) that ended in April 2012). Relationships (α = 0.05) among water quality and hydrologic variables were examined using a Spearman rank correlation coefficient and the principal component analysis (PCA). Nitrogen concentrations on IC were positively correlated with flow during SP. The export of nutrients and sediment from this drained pine plantation forest intercropped with switchgrass was affected by changes in hydrological and biochemical processes regulating the formation and transport of different water quality constituents during both site preparation and pine and switch growth periods. The PCA showed strong interaction between the hydrological and biochemical processes.
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