Landscape-level effects of forest management on faunal diversity in bottomland hardwoods

Forest management activities potentially influence ecosystems at many spatial scales. For most forest systems, influences at the stand level have been most intensively studied and are best understood. Management impacts at the larger, landscape scale are poorly understood and many hypotheses regarding landscape-level effects remain untested. This lack of knowledge is particularly acute in bottomland hardwood forest (BLH) ecosystems. Most hypotheses regarding landscape-level impacts were derived from theories about island biogeography and metapopulations. Thus, species presence and productivity sometimes are viewed as functions of patch characteristics such as size, shape, amount of edge, degree of isolation from larger, similar habitats, time since isolation, and dispersal, immigration, and extinction rates. Recommendations for mitigating fragmentation effects often include maintenance of reserves, increasing patch size, reducing edges, and enhancing connectivity through the use of corridors. While many of these theories are intuitively sound, there are few data to demonstrate their effectiveness in landscapes dominated by managed forests, including BLH forests. We suggest that high priority be given to using adaptive management to simultaneously test hypotheses about how biotic communities function in managed, BLH landscapes. Such information would help managers understand the consequences of their activities, provide them with more flexibility, and improve their ability to protect biological diversity while also meeting society's needs for forest resources.     

Silvicultural systems for southern bottomland hardwood forests

Silvicultural systems integrate both regeneration and intermediate operations in an orderly process for managing forest stands. The clearcutting method of regeneration favors the development of species that are moderately intolerant to intolerant of shade. In fact, clearcutting is the most proven and widely used method of successfully regenerating bottomland oak species in the South. The seed-tree method of regeneration favors the establishment of light-seeded species. Mechanical soil scarification may be necessary if the desired species requires bare mineral soil for establishment. The shelterwood method of regeneration can provide for the development of heavy-seeded species, but has produced highly variable results with southern bottomland oaks. The single-tree selection method of regeneration favors the development of shade-tolerant species. When single-tree selection is applied repeatedly to stands containing commercially valuable shade-intolerant species, composition will gradually shift to less-valuable, more-tolerant species. Consequently, the single-tree selection method of regeneration is not recommended for any commercially valuable bottomland hardwood tree species. Group selection, in its strictest application, creates only small openings that usually fail to allow sufficient light to the forest floor for satisfactory establishment and development of shade-intolerant bottomland species. Patch cutting, a combination of uneven-aged (group selection) and even-aged (clearcutting) silviculture, designed to create larger openings, has been successfully used to produce an uneven-aged stand that consists of many small, irregularly shaped, even-aged groups. Silvicultural systems should include a planned program of intermediate operations designed to enhance the growth and development of those species favored during the regeneration process. Improvement cutting and commercial thinning are increasingly common in southern bottomland hardwood forests. Other partial cuttings employed today in bottomland hardwood forests typically involve some form of crop-tree release. Specific recommendations for the selection of silvicultural systems are presented for the eight most important species groups found in southern bottomland hardwood forests.     

Sedimentation associated with forest road surfacing in a bottomland hardwood ecosystem

Access systems are a necessary element of resource production in bottomland hardwood sites. However, road building may have a detrimental effect on hydrologic function of the site. This report describes initial results of a study designed to examine the effect of different road surfacing treatments on water quality.

Four surfacing treatments installed on two test roads included native soil, native soil with vegetative stabilization, 6 cm of gravel, and 15 cm of gravel over geotextile. During the first flooding season periodic sampling measured floodwater suspended sediments and location of erosion and sediment deposition within the road prism. Initial results suggest that sediment movement was confined to the road right-of-way, with no statistically significant sedimentation effects detected beyond the clearing limits of the road. The study is continuing for another field season.     

Development and ecology of bottomland hardwood sites

A basic knowledge of the origin, development, and ecology of bottomland hardwood sites is important for assessing harvesting impacts on those sites. This paper presents an overview of the geologic origin and development of hardwood sites, species-site relationships and the natural patterns of ecological succession on those sites, and the implications of that information for forest management. Bottomland hardwoods occur on floodplain sites primarily in the Atlantic and Gulf Coastal Plains. Past geologic events led to the formation of broad stream valleys in those areas because of the erodible, sedimentary geologic materials. Natural patterns of ecological succession on floodplain sites are influenced by autogenic and allogenic processes in that the sites may undergo constant change because of deposition. Three natural patterns of succession are recognized for floodplain sites of major river bottoms—those occurring on permanently flooded sites, those on low elevation wet sites, and those on higher elevation, better drained sites. Floristic composition and successional patterns are strongly influenced by the hydrologic events on the sites and particularly by rates and types of deposition.     

Improved harvesting systems for wet sites

Environmentally acceptable and economical forest operations are needed for sustainable management of forest resources. Improved methods for harvesting and transporting timber are especially needed for wet sites. As the demand for hardwood lumber continues to increase, improved and alternative methods are needed to ensure acceptance of timber harvesting for the wet site conditions that are typical of bottomland hardwoods. Some alternative technological developments include grapple saw feller-bunchers, wide tires, larger forwarders, clambunk skidders, two-stage hauling, mats, cable systems, helicopters and towed vehicles and air-cushioned vehicles. These developments have the potential to improve the performance of the harvesting system and to reduce the negative effects of conventional operations on conventional sites and on difficult sites such as wet areas. Although many of these new alternatives are now operational, others are just concepts or evolving prototypes. More research is still needed to optimize these alternative technologies and to reduce costs associated with their implementation.     

The effects of timber harvest in a South Carolina blackwater bottomland

This study was initiated on the South Fork Edisto River in South Carolina to investigate and compare the impacts of two different harvest methods (helicopter and rubber-tired skidder) on the ecological structure and function of a blackwater forested wetland. The two harvest treatments were chosen to represent a broad spectrum of potential impacts and were compared to an undisturbed site. Following harvest in 1991, functional responses in vegetative productivity, herpetofaunal populations, and soil and water quality were evaluated in 1992 and 1993. Herbaceous biomass was greater on the helicopter and skidder treatments than on the undisturbed control. In general, the biomass measured on the skidder treatment was not significantly different from the biomass measured on the helicopter treatment. Higher decomposition rates were noted in the harvested areas as compared to the control. This was mainly attributed to higher soil temperatures, which accelerated microbial activity. Increased decomposition rates may have been responsible for elevated levels of ammonium and organic carbon observed in ground water samples. A total of 29 species of herpetofauna (10 amphibians and 19 reptiles) were observed during the study. Salamanders were found more often in the undisturbed control. Reptiles were observed more frequently in the harvested area. Although herpetofaunal species composition was different between harvest and control, indices of diversity were similar.     

Effects of silvicultural activity on ecological processes in floodplain forests of the southern United States: a review of existing reports

Activities associated with timber harvesting have occurred within floodplain forests in the southern United States for nearly two hundred years. However, it is only in the last ten years that any information has become available about the effects of harvesting on the ecological functions of this valuable resource. Hydrology is the driving influence behind all ecological processes in floodplains, and timber harvesting alone usually has little long-term effect on hydroperiod. However, logging roads, built in association with harvest sites, can sometimes alter hydroperiod to the extent that vegetation productivity is raised or lowered. There is no evidence that harvesting followed by natural regeneration represents a threat to ground or surface water quality on flood plain sites, as long as “best management practices” are followed. Harvested floodplains may increase or have little effect on decomposition rates of surface organic matter. The nature of the effect seems to be controlled by site wetness. Data from recently harvested sites (i.e. within the last ten years) suggest that vegetation productivity is maintained at levels similar to those observed prior to harvests. During the early stages of stand development, tree species composition is heavily influenced by harvest method. Similarly, amphibian populations (monitored as bioindicators of ecosystem recovery) seem to rebound rapidly following harvests, although species composition may be different from that of unharvested stands.     

Initial responses of woody vegetation, water quality, and soils to harvesting intensity in a Texas bottomland hardwood ecosystem

Sustainable management of bottomland hardwood forest ecosystems requires a knowledge of responses to management impacts, including timber harvesting. The effects of clearcutting and partial cutting on woody vegetation regeneration dynamics, surface and groundwater quality, soil physical properties, and soil respiration were tested in a bottomland hardwood ecosystem in southeastern Texas, USA, through comparison with non-cut control areas. Overstory removal only slightly affected composition of woody vegetation regeneration 1 year after harvesting compared with pre-harvest composition. Initial composition in both cutting treatments appeared to be the strongest determinant of post-harvest composition, at least for the first year after harvesting. There were few significant differences in groundwater properties when harvesting treatments were compared with control areas during a 17-month period following harvest. Turbidity, temperature, electrical conductivity, dissolved O₂, NH₄-N, NO₃-N, and PO₄-P of streamwater did not vary significantly among treatments. Slight decreases in total and macroporosity were observed in association with higher bulk densities at 0–5 cm depth in the clearcut and partial cut treatments. Saturated hydraulic conductivity values did not decline significantly with treatment intensity. No significant differences among treatments in measured soil physical properties were observed at 5–10 cm depth. Although in situ soil respiration increased with harvest intensity, treatment had no significant effect on mineral soil respiration. In summary, most variables showed only slight response to harvesting, thereby indicating that harvesting practices can be conducted with minimal initial impacts on measured response variables.     

Nursery stock quality as an indicator of bottomland hardwood forest restoration success in the Lower Mississippi River Alluvial Valley

Abstract

Seedling morphological quality standards are lacking for bottomland hardwood restoration plantings in the Lower Mississippi River Alluvial Valley, USA, which may contribute toward variable restoration success. We measured initial seedling morphology (shoot height, root collar diameter, number of first order lateral roots, fresh mass, and root volume), second year field heights and diameters, survival, browse, and top dieback of five species – cherrybark oak (Quercus pagoda Raf.), green ash (Fraxinus pennsylvanica Marsh.), Nuttall oak (Q. nuttallii Palmer), sweet pecan (Carya illinoensis (Wangenh.) K. Koch), and water oak (Q. nigra L.). Seedlings were obtained from three regional nurseries (Arkansas, Louisiana, and Mississippi), planted on three sites (Arkansas, Louisiana, and Mississippi), and treated with or without chemical weed control. Site×nursery interaction and weed control (without interactions) usually affected survival, whereas site×weed control interaction and nursery (without interactions) influenced second year heights and diameters. Weed control generally increased survival rates, as well as second year height and diameter. Effects of initial morphological characteristics on field survival and height and diameter growth were generally dependent on the other morphological parameters. Target morphological characteristics were identified as 99, 84, and 82 in height/diameter ratios (equal units) for cherrybark oak, green ash, and Nuttall oak, respectively; mean initial height of 40–43 cm in sweet pecan; and mean initial fresh mass/root volume of 2.7 g ml^?1 in water oak. Seedlings with means above these values may be more susceptible to dieback or mortality after outplanting, likely associated with excessive shoot relative to root biomass.     

Maximum entropy modeling of mature hardwood forest distribution in four U.S. states

In the eastern United States, mature hardwood forest provides habitat for many species of native flora and fauna, but is much less common now than historically. This study examined the utility of maximum entropy modeling and spatial application to identify ecosystem types like mature hardwood forest. I performed pilot modeling in Charles County, Maryland, where I compared fine-scale geographic data available locally to coarse-scale data available nationally. As expected, a model constructed with the best locally available data, including LiDAR-derived canopy height and fine-scale soil maps, outperformed a model constructed with nationally consistent data. However, the model using national data nevertheless accurately identified most mature hardwood forest sites and excluded most young forest. I then applied the coarse-scale approach to four states: Pennsylvania, Ohio, Kentucky, and Tennessee. Average test AUC (area under the receiver operating curve) based on 10 replicates varied from 0.76 to 0.80 when comparing mature hardwood forest locations to general forest locations. The maximum training or test sensitivity plus specificity threshold, depending on the state, captured 78-79% of positive locations while rejecting 74-81% of negative locations. The maximum entropy approach is versatile, and can be applied to other ecosystems and species.     

Nitrogen immobilization by wood-chip application: Protecting water quality in a northern hardwood forest

Forest harvesting disrupts the nitrogen cycle, which may affect stream water quality by increasing nitrate concentrations, reducing pH and acid neutralizing capacity, and mobilizing aluminum and base cations. We tested the application of wood chips derived from logging slash to increase immobilization of N after harvesting, which should reduce nitrate flux to streams. In August 2004, a stand of northern hardwoods was patch-clearcut in the Catskill Mountains, NY, and four replicates of three treatments were implemented in five 0.2-ha cut patches. Wood chips were applied to the soil surface at a rate equivalent to the amount of slash smaller than eight inches in diameter (1× treatment). A second treatment doubled that rate (2×), and a third treatment received no chips (0×). Additionally, three uncut reference plots were established in nearby forested areas. Ion exchange resin bags and soil KCl-extractions were used to monitor nitrate availability in the upper 5–10 cm of soil approximately every seven weeks, except in winter. Resin bags indicated that the wood chips retained 30% or 42% of the nitrate pulse, while for KCl extracts, the retention rate was 78% or 100% of the difference between 0× and uncut plots. During the fall following harvest, wood-chip treated plots had resin bag soil nitrate concentrations about 25% of those in 0× plots (p = 0.0001). In the first growing season after the cut, nitrate concentrations in wood-chip treated plots for KCl extracts were 13% of those in 0× treatments (p = 0.03) in May and about half those in 0× treatments (p = 0.01) in July for resin bags. During spring snowmelt, however, nitrate concentrations were high and indistinguishable among treatments, including the uncut reference plots for resin bags and below detection limit for KCl extracts. Wood chips incubated in litterbags had an initial C:N of 125:1, which then decreased to 70:1 after one year of field incubation. These changes in C:N values indicate that the wood-chip application can potentially immobilize between 19 and 38 kg N ha⁻¹ in the first year after harvesting, depending on the rate of wood-chip application. Our results suggest that the application of wood chips following harvesting operations can contribute to the protection of water quality and warrant additional research as a new Best Management Practice following cutting in regions that receive elevated levels of atmospheric N deposition.     

Hurricane Katrina impacts the breeding bird community in a bottomland hardwood forest of the Pearl River basin, Louisiana

We monitored breeding bird communities and vegetation both before and after Hurricane Katrina category 2 winds severely damaged extensive bottomland hardwood forest of the Pearl River basin, south Louisiana. Many trees were felled by wind, most others were stripped of leaves and branches, and the canopy opened considerably (57%). Blackberry thickets sprouted and expanded to cover almost all of what was previously a patchily open forest understory. The bird community changed distinctively following the hurricane, driven primarily by increased density of species that prefer dense understory (regenerating) habitat. Individual species that increased significantly in density included one year-round resident, Carolina wren, and five breeding migrants, white-eyed vireo, Swainson's warbler, Kentucky warbler, hooded warbler, and yellow-breasted chat. These patterns were predictable responses to the opened canopy and increased density of understory vegetation. However, over three years following the storm, most species, especially canopy breeders, showed no distinct numerical response to the hurricane, which suggests that the initial bird community was resistant to hurricane disturbance. Only one species, Acadian flycatcher, declined significantly after the hurricane, presumably because of loss of its preferred open understory breeding and feeding habitat. Our results thus document and reinforce the important role hurricanes play along the Gulf coast in structuring forest bird communities by altering understory habitat. We expect habitat changes will continue as invasive plant species further change forest community structure, and as large storms increase in frequency in relation to global climate change. Thus, we also expect continued changes to the bird community, which may include additional future declines.     

Short- and long-term responses of total soil organic carbon to harvesting in a northern hardwood forest

The long-term response of total soil organic carbon pools (‘total SOC’, i.e. soil and dead wood) to different harvesting scenarios in even-aged northern hardwood forest stands was evaluated using two soil carbon models, CENTURY and YASSO, that were calibrated with forest plot empirical data in the Green Mountains of Vermont. Overall, 13 different harvesting scenarios that included four levels of aboveground biomass removal (20%, 40%, 60% and 90%) and four different rotation lengths (60 year, 90 year, 120 year, and No Rotation (NR)) were simulated for a 360 year period. Simulations indicate that following an initial post-harvest increase, total SOC decreases for several decades until carbon inputs into the soil pool from the re-growth are greater than losses due to decomposition. At this point total SOC begins to gradually increase until the next harvest. One consequence of this recovery pattern is that between harvests, the size of the SOC pool in a stand may change from −7 to 18% of the pre-harvest pool, depending on the soil pool considered. Over 360 years, the average annual decrease in total SOC depends on the amount of biomass removed, the rotation length, and the soil pool considered. After 360 years a stand undergoing the 90yr-40% scenario will have 15% less total SOC than a non-harvested stand. Long-term declines in total SOC greater than 10% were observed in the 60yr-60%, 60yr-90%, and 90yr-90% scenarios. Long-term declines less than 5% were observed in scenarios with 120 year rotations that remove 60% or less of the aboveground biomass. The long-term decreases simulated here for common management scenarios in this region would require intensive sampling procedures to be detectable.     

中美森林游憩政策比较

简要介绍了中美两国森林游憩发展历史,从管理体制、经营权与管理权、法制建设、规划设计、基金来源与利用、非营利组织的参与性、人事管理、森林游憩资源的保护、环境教育的开展等方面比较了中美森林游憩政策,总结了发展过程中的教训,针对我国森林游憩现状,提出了改革与发展对策。     

美国的林业政策和制度

对美国林业管理及服务体系、林业政策和制度、林业体系管理的目标，以及美国各个部门和组织在实施这些政策中所起的作用和实施成效作了介绍。     

Foraging behavior of pileated woodpeckers in partial cut and uncut bottomland hardwood forest

In bottomland hardwood forests, partial cutting techniques are increasingly advocated and used to create habitat for priority wildlife like Louisiana black bear (Ursus americanus luteolus), white-tailed deer (Odocoileus virginianus), and Neotropical migrants. Although partial cutting may be beneficial to some species, those that use dead wood may be negatively affected since large diameter and poor quality trees (deformed, moribund, or dead) are rare, but normally targeted for removal. On the other hand, partial cutting can create dead wood if logging slash is left on-site. We studied foraging behavior of pileated woodpeckers (Dryocopus pileatus) in one- and two-year-old partial cuts designed to benefit priority species and in uncut forest during winter, spring, and summer of 2006 and 2007 in Louisiana. Males and females did not differ in their use of tree species, dbh class, decay class, foraging height, use of foraging tactics or substrate types; however, males foraged on larger substrates than females. In both partial cut and uncut forest, standing live trees were most frequently used (83% compared to 14% for standing dead trees and 3% for coarse woody debris); however, dead trees were selected (i.e. used out of proportion to availability). Overcup oak (Quercus lyrata) and bitter pecan (Carya aquatica) were also selected and sugarberry (Celtis laevigata) avoided. Pileated woodpeckers selected trees ≥50 cm dbh and avoided trees in smaller dbh classes (10–20 cm). Density of selected foraging substrates was the same in partial cut and uncut forest. Of the foraging substrates, woodpeckers spent 54% of foraging time on live branches and boles, 37% on dead branches and boles, and 9% on vines. Of the foraging tactics, the highest proportion of foraging time was spent excavating (58%), followed by pecking (14%), gleaning (14%), scaling (7%), berry-eating (4%), and probing (3%). Woodpecker use of foraging tactics and substrates, and foraging height and substrate diameter did not differ between recent partial cut and uncut forest. Partial cutting designed to improve or maintain habitat for priority wildlife did not affect pileated woodpecker foraging behavior or availability of selected trees compared to uncut forest in the short term.     

Influence of harvesting on biogeochemical exchange in sheetflow and soil processes in a eutrophic floodplain forest

Floodplain forests contribute to the maintenance of water quality as a result of various biogeochemical transformations which occur within them. In particular, they can serve as sinks for nutrient run-off from adjacent uplands or as nutrient transformers as water moves downstream. However, little is known about the potential that land management activities may have for alteration of these biogeochemical functions. This paper examines the effects of three harvesting regimes (unharvested control, clearcut, and partial cut) on the physical and chemical parameters within the Flint River floodplain located in southwestern Georgia, USA. Data presented in this paper were collected during the year following initiation of the harvesting treatments which occurred in September of 1993. Sheetflow water chemistry (total suspended solids (TSS), total dissolved solids (TDS), nitrate (NO₃⁻), phosphate (PO₄³⁻), sulfate (SO₄²⁻), calcium (Ca²⁺), potassium (K⁺), magnesium (Mg²⁺), ammonium (NH₄⁺), total phosphorous (P), total nitrogen (N), total carbon (C), dissolved organic carbon (DOC)), sedimentation rates, depth of soil oxidation after flooding, saturated hydraulic conductivity, and bulk density were measured. During the year immediately after treatment installation, alterations in some of the physical and chemical properties (TDS, NO₃⁻, total P, and K⁺) of floodwaters crossing harvest plots were detected. Soil oxidation depths, saturated hydraulic conductivity and bulk density also changed with treatment. The meaning of the changes detected is uncertain but they suggest the nature of potential changes in nutrient spiralling and non-point source cumulative effects that may occur within a managed watershed. Second-year data may offer an interesting comparison of sheetflow chemistry and sedimentation changes between vegetated and non-vegetated conditions.     

苞叶杜鹃硬枝扦插育苗技术的研究

以苞叶杜鹃休眠硬枝为试验材料,在不同扦插基质、不同激素种类和质量浓度条件下进行扦插试验,结果表明:插穗在河沙+蛭石基质中的成活率为14.5%,高于草炭土+珍珠岩+腐叶土基质;质量浓度为150 mg·L-1的NAA、IBA处理的效果好于其它处理,插穗成活率分别为21.3%和18.8%,而在河沙+蛭石(1:1)基质中的成活...     

Understanding the Relationships Between American Ginseng Harvest and Hardwood Forests Inventory and Timber Harvest to Improve Co-Management of the Forests of Eastern United States

The roots of American ginseng have been harvested from the hardwood forests of the eastern United States, alongside timber, since the mid-1700s. Very little is known about this non-timber commodity relative to timber, although significant volumes of ginseng root have been harvested from the same forests along with timber. The harvest of ginseng correlated positively and significantly with hardwood forest area, hardwood growing stock volume, and timber removals. Also, it correlated with hardwood growing stock on public forestlands in the region. The annual wholesale value of American ginseng was estimated at approximately $26.9 million compared to annual stumpage value of harvested hardwood timber of just over $1.27 billion. The volume of ginseng root harvested from natural forests represents substantial extraction of biomass, and the associated value represents substantial income for people living in an economically marginalized region. Co-management of eastern hardwood forests for timber and non-timber forest products could improve local economies and better conserve the biodiversity of these forests.     

葡萄硬枝扦插繁殖的试验研究

本试验对影响葡萄硬枝扦插苗成活和生长有关因素进行了研究。结果表明：葡萄硬枝扦插成活率的高低不仅与种株及种条的选择、种条的质量、ABT的处理浓度、扦插技术等因素有关，而且还与扦插后的管理有密切关系。