Background Thinning and prescribed fire are increasingly used to promote oak ( Quercus L. spp.) regeneration in forest restoration projects across the eastern United States. In addition to monitoring the response of vegetation to these reductions in basal area, the research and land management community has become focused on the response of wildlife to these treatments. In a landscape in which forest ownership is fragmented and dominated by non-industrial private landowners, predicting the range of wildlife and vegetation response to treatments will be necessary to facilitate adoption of a landscape-scale approach to oak restoration. The goal of this study was to examine the efficacy of restoring privately owned, mixed forest stands that were partially planted in loblolly pine ( Pinus taeda L.) and eastern white pine ( Pinus strobus L.) to oak-dominated communities through the use of thinning and prescribed fire. Additionally, the study documented implications of these treatments on small mammal activity in the southern Cumberland Plateau. Results Following basal area reductions ranging from 30 to 60% and three prescribed fires across three sites, mean oak seedling densities rose from 10 200 ha −1 to 17 900 ha −1 . Post-treatment oak seedling densities were related to pre-treatment densities (R 2 = 0.55, P < 0.0001) and the number of oak trees >20 cm diameter within 10 m of plot center (R 2 = 0.15, P = 0.01). Three years after the last prescribed fire, bat activity (mean passes per night) was significantly higher in the treated stands compared to adjacent undisturbed forest. We did not detect any significant differences in rodent activity between our treated stands and forest controls for two of the three years studied. Conclusions The results of this study highlighted the within-stand variation that drives post-harvest vegetation trajectories. Three years after the last prescribed fire, bats exhibited higher foraging activity in the treated sites that had lower basal area and very little midstory clutter. Our three-year summer monitoring of rodent activity following the last of the three prescribed fires revealed differences in rodent activity between our treated sites and adjacent forest controls only during 2018 ( P = 0.001). These results will assist private landowners in the region as they consider the costs and benefits of oak forest restoration.

Prior land use and soil legacies related to land use continue to play a significant role in ecosystem structure and functioning in the eastern deciduous forest. On the surface of the southern Cumberland Plateau in Tennessee, abandoned agricultural and home sites are characterized by unusual assemblages of tree species and ground cover, as well as light artifact scatters. To better understand the legacies of past land use on soil properties and forest composition in this region, we intensively sampled three home sites that were abandoned more than 70 y ago and compared them to adjacent forest controls. The home sites had significantly higher concentrations (soil A horizons) for eight of the fourteen elements studied. After examining our plots in ordination space by soil variables, we found that surface soil calcium and phosphorus concentrations were negatively associated to control plots and were the best indicators of intensive human disturbance. Sourwood (Oxydendrum arboreum) had the highest importance value in the control forest, and the 23rd highest importance value at the home sites. There were 34 different species encountered at the home sites, including many species usually found at lower elevations in limestone-derived soils (e.g., Celtis occidentalis, Juglans nigra, Viburnum rufidulum, Fraxinus spp.). We recovered historic artifacts and charcoal from surface soils at all three sites, and prehistoric artifacts were found at two sites. Abandoned home sites are common throughout the eastern deciduous forest and evidence from this study indicates that land use legacies continue to influence forest dynamics several decades after anthropogenic inputs ceased.

Maritime forests in the southeastern United States are very susceptible to climate change and have experienced dramatic reductions in extent following anthropogenic disturbances over the past two hundred years. St. Catherines Island, Georgia, an undeveloped barrier island, is home to an unusual pignut hickory (Carya glabra) maritime forest that is experiencing rapid rates of change, including a reduction in basal area from 23 m2·ha-1 in 1996 to 15 m2·ha-1 in 2014. Nine permanent forest plots and associated animal exclosures were installed across this 37 ha stand in 2012 to track forest change and seedling recruitment. From 2012 to 2014, declines in total basal area were caused by mortality of pignut hickory in the overstory and redbay (Persea borbonia) in the midstory. Pignut hickory continues to be ranked first in relative frequency, density and dominance, while Sabal palm (Sabal palmetto) is slightly increasing in relative density. In 2012, there were no woody species regenerating in any of the plots and following one year of animal exclosures, we found 478 pignut hickory seedlings ha-1; thus, deer browse and feral hog predation of nuts may be important drivers of change in this stand. The interplay among deer browse, exotic animal pressures, exotic insects and a drier climate has resulted in a very open forest with the regeneration of few woody plants. Without management of the feral hog and deer population, this unusual maritime forest, with trees as old as 250 years, may continue to decline.

Introduced to the United States in 2002, laurel wilt (Raffaelea lauricola) is a fungus that causes life threatening defensive responses in the vascular system of trees within the Lauraceae family, and it is introduced to the tree by the Asian ambrosia beetle (Xyleborus glabratus). Redbay (Persea borbonia) is the preferred host species within the US coastal plains and maritime forests, and it has experienced rapid mortality throughout its range in the southeastern United States since the introduction of the ambrosia beetle and associated fungus. In this study, we inventoried all dead and live redbay trees from replicated transects inside a maritime forest, a successional old-field forest (both located on the island’s Pleistocene core), and a Holocene hammock to examine the role of soils, prior land use and landscape position on redbay survival eleven years after the introduction of the exotic beetle and fungus on the island. Results indicated that the maritime forest had a significantly higher number of redbay trees prior to infection compared to the hammock or old-field sites. Eleven years post-infection, all three sites had similar densities of redbay trees and the surviving trees had similar diameter distributions among the three sites. Soils under the maritime forest had significantly higher phosphorous (P) and pH concentrations, and the Holocene hammock had a higher water table compared to the sites on the Pleistocene core. Almost all living trees at each site had signs of invertebrate herbivory and twig borer damage. Prior land use history and soils affected redbay densities before laurel wilt infection, but eleven years post-infection, all three site types had similar redbay densities, diameters, basal areas, and levels of herbivory and surviving trees did not demonstrate signs of photosynthetic stress.

St. Catherines Island, located off the coast of Georgia (United States), has been inhabited by humans for close to 5000 years. The island's long-term habitation and varied history of land use has left a legacy of anthropogenic impacts that has strongly influenced the composition and function of the current vegetation communities and underlying soils. In this study, we examined the chemistry of surface soils collected from 32 sites representing five historical land uses (old cotton plantations, longleaf pine savanna, hickory forest, maritime forests, and shell middens) to determine how human activities have affected the island's surface soils. We found that shell deposition left a strong chemical signal, significantly increasing soil pH, cation exchange capacity, and concentrations of Ca, total nitrogen, and several micronutrients. Soils under the hickory-dominated forest had chemical characteristics that were intermediate between the middens and the other three cover types. Despite a wide range in pH, all sites had very high concentrations of extractable P, possibly because of retention by Ca and Fe. Shell deposition has altered soil chemistry in numerous areas across the island, and this has important implications for soils and the resultant vegetation patterns currently seen along St. Catherine's coastlines as well as other coastlines throughout the world.

In this study, we developed and tested a geographic information system methodology to measure the width and slope of streamside management zones (SMZs). We also assessed the compliance of SMZs on the Cumberland Plateau of Tennessee with the quantitative portions of state best management practices and the sustainable forestry standards used by the Sustainable Forestry Initiative and the Forest Stewardship Council (FSC). We found that using different standards greatly affected overall SMZ compliance and that FSC-level compliance varied as a function of type and resident status of forest owner.

Title: Assessing costs of exurbanization of forest and farmland on south-central Tennessee’s Cumberland Plateau and Sequatchie Valley: student-faculty research in environmental studies Investigators: Deborah McGrath, Assistant Professor of Biology C. Ken Smith, Associate Professor of Forestry and Geology, and Chair of Environmental Studies University of the South, 735 University Avenue, Sewanee, TN 37383-1000 E-mail: dmcgrath@sewanee.edu, ksmith@sewanee.eduPhone: 931-598-1991 (McGrath), 931-598-3219 (Smith) Submission date: April 28, 2006

Root ingrowth cores were used to quantify fine root response to nutrient treatments in early and late successional stage black spruce-feathermoss ecosystems that originated from either fire or timber harvesting [cut with protection of regeneration and soils (CPRS)]. Three nutrient treatments (nitrogen, phosphorus, and calcium) were added to ingrowth cores, and root ingrowth was compared with control (water-treated) cores. The efficacy of using a natural substrate from the black spruce-feathermoss organic horizon with the ingrowth core technique was also evaluated. There was an important effect (p = 0.06) of nutrient treatment on fine root length and biomass in the cores, and the age of the stand since the time of the disturbance helped to explain differences in root lengths and biomass (p = 0.05), with older sites having greater root length and root biomass ingrowth into the cores during the study period. Experience with this technique demonstrated that the choice of fill material, core preparation, and the role of mycorrhizae in root proliferation and nutrient export from the cores are important to consider in future use of this technique.

Over the past two decades, forests in the southeastern United States have undergone dramatic changes as the result of urban sprawl and conversion to intensively managed pine plantations. The Cumberland Plateau, an important ecoregion in the southeastern United States, contains some of the largest remaining tracts of privately owned, native hardwood forest in North America. These ecologically important forests have been undergoing increasingly rapid rates of hardwood-to-pine conversion, much of which has gone undetected by large-scale statewide inventories. Forest conversion in Tennessee's southern Cumberland Plateau provides a case study highlighting the need for interdisciplinary and spatially explicit assessments of the impact and drivers of land-use change at smaller scales. Aerial and satellite imagery were used to create computer-generated maps of land use and forest cover for a 243 000 ha study area within a seven-county region of the southern Cumberland Plateau in Tennessee to track and document patterns of forest change and conversion between 1981 and 2000. The ecological impact of forest harvesting and hardwood-to-pine conversion was evaluated by (i)monitoring aquatic macroinvertebrate diversity, (ii) tracking breeding-bird populations, and (iii) comparing calcium (Ca) stores and cycling in a chronosequence of hardwood to first- and second-rotation loblolly pine (Pinus taeda) plantations. It was found that 14% of native forest cover had been lost since 1981, 74% of which resulted from hardwood-to-pine conversion. It was also found that the rate of conversion to pine doubled from 1997 to 2000. Water quality in streams, as measured by the abundance of critical macroinvertebrates, was significantly lower in recently logged sites than in undisturbed native forest. Surveys of breeding-bird populations showed that pine plantations of several age classes had lower species richness and evenness than did native oak-hickory forests. Despite similar soil concentrations of Ca in native hardwood, mature first-rotation, and early second-rotation pine, changes were found in aboveground Ca storage that suggest substantial system Ca losses that may limit productivity of second-rotation pine or regrowth of oak-hickory forest. As part of the ongoing research on the socioeconomic drivers of land-use change on the Cumberland Plateau, it was found that Tennessee's major forest conservation incentive program only delays forest conversion for a few years while subsidizing landowners who would not have converted their land in the absence of the program. These results demonstrate the need for more detailed and multidisciplinary research conducted at smaller scales so as to enhance the understanding of the impact and drivers of land-use change at larger scales.

The large-scale conversion of Amazonian forest to other land-uses is altering carbon (C) stocks in this important eco-region, and these changes will in turn influence global C cycling. In this study, we evaluated changes of forest floor and surface soil C storage caused by converting primary Amazonian forest to tree plantations at the Curuá-Una Forest Reserve, Pará, Brazil. The plantations were established between 1959 and 1973 and they consisted of replicated plots of Pinus caribaea var. hondurensis Barrett and Golfari, Carapa guianensis Aubl., Euxylophora paraensis Hub., and a Leguminosae combination (Parkia multijuga Benth., Dinizia excelsa Ducke, Dalbergia nigra Fr. All. In surface soils (0–20cm), mean C stocks ranged from 7 (P. caribaea) to 11kgm−2 (E. paraensis). Fine litter C inputs ranged from 380gm−2 (E. paraensis) to 513gm−2 (P. caribaea), and forest floor C stocks (fine material) ranged from 359 (E. paraensis) to 542gm−2 (P. caribaea). P. caribaea had the smallest fine root biomass–C (≤2mm diameter) in the forest floor and surface soils (101gm−2). Relative to adjacent terra firme forest, total C stocks in the surface mineral soil, forest floor, and fine roots (live+dead) in the plantations ranged from a net decrease of 13% (P. caribaea) to a net increase of 7% (E. paraensis).

Over the past several decades, the conversion of native forest to agricultural land uses has accelerated across the Amazon Basin. Despite a growing body of research on nutrient dynamics in Amazonian primary forest and forest-derived land uses, the effects of widespread land-use change on nutrient contents and cycles in soil and vegetation are not well understood. We reviewed over 100 studies conducted in Amazônia over the past 40 years on nutrient dynamics in natural forests and forest-derived land uses (pasture, shifting cultivation, and tree plantations). Our objectives were to compare soil data from land uses across Amazônia and identify any gaps in our present knowledge that might offer direction for future research. Specifically, by analyzing data we tested the following five widely cited hypotheses concerning the effects of land-use change on soil properties compiled from 39 studies in multifactorial ANOVA models; (a) soil pH, effective cation exchange capacity (ECEC), and exchangeable calcium (Ca) concentrations rise and remain elevated following the slash-and-burn conversion of forest to pasture or crop fields; (b) soil contents of total carbon (C), nitrogen (N), and inorganic readily extractable (that is, Bray, Mehlich I, or resin) phosphorus (P i ) decline following forest-to-pasture conversion; (c) soil concentrations of total C, N, and P i increase in secondary forests with time since abandonment of agricultural activities; (d) soil nutrient conditions under all tree-dominated land-use systems (natural or not) remain the same; and (e) higher efficiencies of nutrient utilization occur where soil nutrient pools are lower. Following the conversion of Amazonian forest to pasture or slash-and-burn agriculture, we found a significant and lasting effect on soil pH, bulk density, and exchangeable Ca concentrations. Unlike the other three land uses studied, concentrations of extractable soil P i were equally low in both forest and pastures of all age classes, which demonstrates that postburning pulses in soil P i concentration following a slash-and-burn decrease rapidly after forest-to-pasture conversion, perhaps due to accumulation in organic P fractions. Neither the concentrations nor the contents of total C and N appeared to change greatly on a regionwide basis as a result of forest-to-pasture conversion, but surface soil C:N ratios in 5-year-old pastures were significantly higher than those in older pastures, suggesting changes in the soil concentrations of at least one of these elements with time after pasture creation. Pasture soils did have higher total C and N concentrations than land uses such as annual cropping and secondary forest fallow, indicating that soil C and N maintenance and/or accumulation following forest conversion may be greater in pastures than in these other two land uses. The low concentrations of C and N in shifting cultivation soils appear to persist for many years in secondary forests regenerating from abandoned crop fields, suggesting that the recuperation of soil losses of C and N resulting during no-input annual cropping is slower than previously thought. Soil C, N and P concentrations were strongly related to clay content. Across all land uses, efficiencies of N, P, and Ca use (estimated as the inverse of litterfall N, P, and Ca contents) were not related to the sizes of their soil pools. More work is needed to test and standardize P extraction procedures that more accurately reflect plant availability. Few studies have been conducted to determine the role of organic P fractions and dissolved organic N (DON) in the elemental cycles of both natural and managed systems in this region. In general, we recommend further study of annual and perennial cropping systems, as well as more detailed examination of managed pastures and fallows, and secondary forests originating from various disturbances, since the intensity of previous land use likely determines the degree of soil degradation and the rate of subsequent secondary regrowth.

In the North American boreal forest, black spruce (Picea mariana) forests have historically regenerated after the passage of large-scale wildfires. Over the past 30 years, tree harvesting has replaced wildfire as the predominant agent of disturbance in black spruce-feathermoss communities in the Lac St. Jean-Chibougamau region of Quebec, Canada. This study addressed how natural and anthropogenic disturbances altered soil and fine root carbon (C), nitrogen (N), and phosphorus (P) stocks and dynamics under four disturbance types in central Quebec including: (1) recently burned sites, (2) sites recently harvested using a practice called "cutting with protection of tree regeneration and soils" (CPRS), (3) sites that were burned 75-85 yr ago, and (4) sites that were horse-logged 55 yr ago. Soil N contents in the surface organic layer of the recently burned sites (91 g/m(2)) were significantly lower than under the old burn sites (146 g/m(2)). Using equivalent soil masses, total N stores in the mineral soils under the recently harvested stands (76 g/m(2)) were significantly lower than N stores under the old burn sites (114 g/m(2)). In field incubations from June to October 1997, net N mineralization rates in the organic horizons ranged from 3.3 kg/ha (recent burn) to 17.1 kg/ha (old harvest). The largest pools of labile inorganic-P (Bray 2 extractable) were in the organic horizons of the old harvest and old burn sites (59.1 and 55.3 mg/kg, respectively), and these pools increased up to 24% from the beginning to the end of the growing season. Pools of dissolved organic nitrogen in surface organic horizons in all of the disturbance types were highest just after snowmelt and declined steadily through the growing season. The older disturbance types had higher N stores in fine roots compared to the recently disturbed sites, and fine root length in the old harvest sites (1623 m/m(2)) was higher than in the stands burned 75-85 yr ago (917 m/m(2)).

The influence of plant species on soil nitrogen (N) dynamics was investigated in lowland Amazonia, Brazil under plantations of tree species with varied phenologies, resource requirements, and chemical characteristics in fine litter. Seasonal N dynamics were studied in replicated stands of Pinus caribaea var. hondurensis Barrett & Golfari, Euxylophora paraensis Hub., Carapa guianensis Aubl., a Leguminosae combination (Dalbergia nigra Fr. All., Dinizia excelsa Ducke, Parkia multijuga Benth.), and native forest in the Curuá-Una Forest Reserve, Pará, Brazil. Textural, mineralogical, and chemical soil properties at 1 m depth under the plantations and the forest indicated that initial soil properties were similar. Net annual N mineralization ranged from 195 kg ha-1 (P. caribaea) to 328 kg ha-1 (forest), and was related to fine root N contents in the surface root mat (R2 = 0.96, p = 0.01). Net annual N mineralization was also inversely related to within-stand nitrogen-use efficiency (R2 = 0.81, p = 0.04). These results suggest that tree species or groups of species with varied N-use efficiencies altered soil N transformation rates in a predictable manner.

Aboveground fine litterfall and decomposition are critical processes for transferring nutrients from forest biomass to soils, and the conversion of Brazilian terra-firme forest to tree plantations with varied litterfall characteristics has altered soil nitrogen (N) dynamics and stores at the Curuá-Una Forest Reserve, Pará, Brazil. In this study, we investigated the relationship between soil N stores and aboveground litter inputs by measuring fine litterfall, litter N inputs, forest-floor mass and turnover, foliar N concentrations, and within-stand nitrogen-use efficiency (NUE) for one year under four plantations and adjacent undisturbed forest. The plantations consisted of replicated plots of Pinus caribaea var. hondurensis (36-year old), Carapa guianensis (36-year old), Euxylophora paraensis (23-year old), and a Leguminosae combination (Parkia multijuga, Dinizia excelsa, and Dalbergia nigra, all 36-year old). Fine litterfall ranged from 8.0 (Euxylophora paraensis) to 10.3tha−1year−1 (Pinus caribaea), forest-floor mass from 7.2 (forest) to 11.0tha−1 (Pinus caribaea), total fine litterfall N inputs from 43 (Pinus caribaea) to 134kgha−1year−1 (legumes), and foliar N concentrations from 9 (Pinus caribaea) to 18.8mgg−1 (legumes). Relative to adjacent terra-firme forest, total N stores in surface mineral soils, forest-floor mass, and fine roots (live+dead) ranged from a net decrease of 25.6% under Pinus caribaea to a net increase of 14% under Euxylophora paraensis. The replacement of terra-firme forest with plantations of tree species with varied phenologies and resource requirements altered soil N stores, but these changes were not related to total fine litter N inputs, needle and foliar N concentrations, or within-stand nitrogen-use efficiency.

One year field exposures of leaf litter from replicated plots of Pinus caribaea var. hondurensis Barrett and Golfari, Carapa guianensis Aubl., Euxylophora paraensis Hub., a Leguminosae combination (Dalbergia nigra Fr. All., Dinizia excelsa Ducke, Parkia multijuga Benth.), and adjacent upland (terra firme) forest at the Curuá-Una Forest Reserve, Pará, Brazil were used to examine the factors controlling leaf litter decay and N dynamics in a lowland tropical environment. Initial leaf litter N concentrations ranged from 4.4 (P. caribaea) to 16.3mgg−1 dry matter (Leguminosae), and initial lignin concentrations from 190.8 (Leguminosae) to 459.3mgg−1 dry matter (forest). Pinus caribaea leaf litter lost the least mass (28%), and the Leguminosae leaf litter the most (61%), during the year long incubations. Initial and 1-y proximate C fractions, N concentrations and polyphenol concentrations were not related to mass loss. Annual N accumulation or depletion from leaf litter under the plantations and forest was related to C loss (R2=0.93, P=0.007) and holocellulose loss (R2=0.84, P=0.02). When leaf litter was placed outside its stand of origin, there was a significant location effect on decay rates, indicating that differences in the physical and biological microenvironments under the monospecific plots affected litter decomposition.

In the black spruce (Picea mariana (Mill.) BSP) forests which span North America, low annual temperatures, high nitrogen and phosphorus absorption by feathermosses and small litter inputs contribute to reduced annual N and P transformation rates in soils of these ecosystems. In past studies of nutrient dynamics in these systems, concentrations of dissolved organic N (DON) and P (DOP) in soil extracts have equaled or exceeded those of mineral N and P; therefore, organic forms of N and P may be an important source of nutrition to plants growing in this region. Our objective was to determine if DON and DOP were important constituents in repeated extractions of laboratory incubated organic material and mineral soils taken from recently burned, recently harvested and fully stocked black spruce stands in central Quebec. Cumulative concentrations of DON ranged from 7 to 17% and 31 to 45% of total N extracted from the organic material and mineral soils, respectively. Cumulative concentrations of DOP ranged from 35 to 44% and 37 to 48% of total P extracted from the organic material and mineral soils, respectively. We detected a pulse of CO2-C release from the organic material after thawing, and weekly CO2-C release was related to NH4+-N release (R2=0.36, P=0.0001). These results suggest that increases in temperature after a winter freeze result in a pulse of microbial activity and NH4+-N mineralization in organic layers and that DON and DOP are an important part of N and P cycling in these boreal systems.