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1.
Bottomland hardwood forests are valued for timber production, water storage, enhanced water quality, nutrient cycling, erosion control and wildlife habitat. However, the majority of southern bottomland stands, 90% of which are in private ownership, are occupied by a degraded mixture of tree species, caused largely by repeated, incomplete harvests. They can be naturally regenerated to a stand of favorable species composition by removing the residual stand of merchantable and non-merchantable trees. For timber production, these systems respond best to even-aged management such as clearcutting, shelterwood cutting and patch clearcutting. Plant succession under such systems allows shade intolerant species to occupy the site, followed by species of increasing shade tolerance. Uneven-aged systems, such as individual-tree selection and group selection, are also viable regeneration methods, but they require great attention to detail and frequent stand entry. In areas of high sensitivity to timber harvesting, a two-aged system such as a leave-tree is recommended. Stand disturbance, either planned or unplanned, is needed to keep southern hardwood forest stands viable.  相似文献   

2.
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.  相似文献   

3.
Development and ecology of bottomland hardwood sites   总被引:3,自引:0,他引:3  
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.  相似文献   

4.
The influence of both aerial and ground-based harvesting on functions of forested floodplains of low-order streams was studied during a two-year period. The study sites were associated with low-order, blackwater streams with infertile and primarily organic soils. Responses to harvesting were assessed in relation to water quality, denitrification, hydrology, regeneration, and decomposition. Water quality indices included nitrate, phosphate, total and dissolved solids, and biological oxygen demand (BOD). All were unaffected by harvesting with the exception of BOD which rose once to undesirable levels. Denitrification was highly variable and also showed no significant harvest effect. Hydrologic parameters included groundwater table depths which, unexpectedly, indicated lowered water tables within harvested areas during the first growing season. Early regeneration responses were strongly linked to harvest system with primarily seed-origin species favored by ground-based activity whereas sprout-origin species dominated on aerial system plots. Owing to inherent soil wetness, decomposition responded slowly to harvest disturbance. However, after one year, decomposition was more rapid on harvested plots than in undisturbed areas.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
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.  相似文献   

10.
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.  相似文献   

11.
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.  相似文献   

12.
In the headwater catchments of the Hun River,Northeast China, secondary forests(SF) have been replaced by plantations since the 1960 s. Concern has been growing over this loss and the decline in water quality caused by the plantations. To test the effects of plantations on water quality, we selected two separate catchments covered by SF and Pinus koraiensis plantations(KP) to monitor physical and chemical properties of various hydrological variables including throughfall, stemflow,through-litterfall and runoff(flowing out of outlets of the catchments). The physical properties of water declined after water flowed through the two catchments as compared with rainwater. The pH of runoff in both catchments also dramatically decreased. The concentrations of Cl^-, NO_3^- and NH_4^+ in the runoff from the two catchments were similar(concentrations of Cl-and NH_4^+ in both catchments were similar to those in rainwater). Total P concentration in runoff of the SF catchment was higher than that of the KP catchment(P concentrations in both catchments were also higher than in rainwater) because P concentrations in litter and soil of the SF catchment were higher than those in the KP catchment. In summary, the rainwater became acidic in both catchments, but the responses of most water quality variables were similar in the two catchments, suggesting that appropriate ratios of KP in SF are feasible for secondary forest recovery and for preserving water quality(KP did not cause a decline in quality) in the headstream regions in Northeast of China.  相似文献   

13.
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.  相似文献   

14.
Soil organic matter (SOM) plays an important role in governing soil properties and nutrient cycling in forest ecosystems. Clear-cutting alters the SOM cycle by changing decomposition rates and organic matter (OM) inputs to the forest ecosystem. We studied the 15-year clear-cutting response on the properties and composition of SOM at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was used to study the structural chemistry of SOM in whole soils and extracted humic substances. Overall, alkyl C and O-alkyl C were the dominant C fractions in soils and humic substances. Alkyl C accounted for 38–49% of the total NMR signal intensity in soils and 33–56% in humic substances. O-alkyl C accounted for 32–45% of the signal intensity in soils and 20–31% in humic substances. Following clear-cutting, the contribution of O-alkyl C increased in whole soils and humic acids of the Oa horizon, while alkyl C decreased in whole soils and humic acids of Oa and Bh horizons. Thus, the ratio of alkyl C to O-alkyl C, an index of the degree of decomposition of SOM, decreased in whole soils and humic acids after clear-cutting, indicating that the SOM in post-harvest soils is less decomposed relative to pre-harvest soils. On average, humic substances accounted for 47% of SOM. The concentration of humic acid decreased by up to 25% in Oa, E and Bh horizons after clear-cutting, while the concentration of fulvic acid decreased by more than 40% in the Oa and E horizons. Together, these results indicate that clear-cutting resulted in the loss of humic substances from the forest floor and upper mineral horizons, which was replaced by less decomposed OM in the post-clear-cut soils under the regrowing forest.  相似文献   

15.
Sustainable management of selectively logged tropical forests requires that felled trees are replaced through increased recruitment and growth. This study compares road track and roadside regeneration with regeneration in unlogged and selectively logged humid tropical forest in north-eastern Bolivia. Some species benefited from increased light intensities on abandoned logging roads. Others benefited from low densities of competing vegetation on roads with compacted soils. This was the case for the small-seeded species Ficus boliviana C.C. Berg and Terminalia oblonga (Ruiz & Pav.) Steud. Some species, e.g. Hura crepitans L., displayed patchy regeneration coinciding with the presence of adult trees. Our results suggest that current management practices could be improved by intensifying logging in some areas to improve regeneration of light demanding species. Sufficient seed input in logged areas should be ensured by interspersing large patches of unlogged forest with logged areas. This may also assist regeneration of species that perform poorly in disturbed areas.  相似文献   

16.
An acidified, 0.8 km2 coniferous-forested catchment was limed with 3 t ha−1 of coarse-grained dolomite powder in September 1994. The liming resulted in an immediate change in runoff water chemistry relative to the stream of an adjacent reference catchment. pH, calcium, magnesium and acid neutralising capacity (ANC) increased and inorganic Al decreased after liming. Potential favourable water quality for sensitive organisms remained relatively constant over the post-liming period (7 years), and model simulations indicate that adequate water quality may last for an additional 40–50 years. NO3 concentrations showed no significant change due to liming. A significant increasing trend in TOC was attributed to liming. Concentrations of Cd, Co, Fe, Mn, Ni and Zn were lower in the limed stream than in the reference stream during a period of 3 years after liming, whereas concentrations of As, Cu, and Pb were not significantly different. Steep slopes, thin soils, high amounts of precipitation and thus dominance of surface and subsurface flow in this catchment may explain the rapid response in runoff. During the first 6 years after liming there have been no significant effects on tree growth and vitality (crown density and crown colour). This experiment shows that liming of forested catchments may be a viable method to obtain long-term improvement in water quality and potential positive effects for acid-sensitive aquatic organisms.  相似文献   

17.
We investigated forest road networks and forestry operations before and after mechanization on aggregated forestry operation sites. We developed equations to estimate densities of road networks with av...  相似文献   

18.
In the late 1980s, large forest companies began precommercial thinning (PCT) operations in young northern hardwood cutovers in New Brunswick, Canada. To provide supporting growth and yield information, an industrial experiment was established at residual stand densities of 1300, 1600, 1900, and 2200?stems?ha?1. Stand responses were examined for measurements recorded at 0 (1987), 5 (1992), 10 (1997), 16 (2003), and 23 (2010) years after establishment. Average diameter at breast height, quadratic mean diameter, stand basal area, and stand total volume growth increased as stem density decreased from PCT. There were significant linear differences for many of these variables between treatments and time periods (year). No significant differences were detected in tree height between treatments. In 2010, the four PCT thinning treatments did not exhibit any differences in potential sawlogs at 2.4?m (8?ft) and 3.6?m (12?ft) lengths. Significant differences were observed for 4.9?m (16?ft) sawlogs that were produced at the least dense spacing (1300?stems?ha?1). Results from this study and recommendations from the European literature suggest that value-added timber products may be produced from more intense PCT treatments than are currently being practiced on sites dominated by yellow birch (Betula alleghaniensis Britt.).  相似文献   

19.
Sudden oak death is a disease affecting coastal forests in California and southern Oregon. The spatial pattern of disease dynamics is important for forest and landscape pathology; in this work we investigated the interaction across landscape scales of disease symptomology in coast live oaks, Quercus agrifolia, (trunk bleeding, presence of beetles, and presence of the fungus Hypoxylon thouarsianum) and tree mortality through time. We used two-dimensional spatial analysis tools with data gathered in point-centered-quarter format in 2001 and 2004 to quantify the population density of the disease through time; to examine the spatial pattern of tree mortality across scales through time; and to examine the spatial co-occurrence of disease symptoms with crown mortality through time. Early in the study period dead trees were strongly clustered at smaller scales (~300 m) and after three years this clustering was less pronounced. Bleeding on trees occurred in clusters away from dead trees, particularly in 2004, likely indicating a new cohort of infected trees. The presence of H. thouarsianum was strongly related to overstory mortality through time. Beetle-infested trees co-occurred with mortality in 2001. By 2004, they occurred throughout the forest, and were less strongly correlated with overstory tree mortality, suggesting a future peak of tree mortality.  相似文献   

20.
We examined the short-term effects of group-selection harvesting with seed-tree retention on ground-dwelling and bark-dwelling arthropod communities in a northern hardwood forest in the Upper Peninsula of Michigan. Arthropods were sampled in 16 group-selection openings and 8 closed canopy reference plots. Two opening sizes were examined—radii of 0.5 (320 ± 27 m2, n = 8) and 1.0 (1217 ± 62 m2, n = 8) times the mean canopy height (22 m). Each opening and reference plot was centered on a single Betula alleghaniensis Britt. (yellow birch). Ground-dwelling arthropods were sampled using pitfall traps that were opened for two 1-week periods (rounds 1 and 2), and bark-dwelling arthropods were sampled with sticky traps attached to the centrally located B. alleghaniensis trees. Family-level diversity of ground-dwelling arthropods was lower in reference plots than in the openings, but the only significant difference occurred during round 2, between the matrix and large openings (P < 0.01). During both sampling periods, the ground-dwelling community exhibited a distinct clustering of family-level composition along environmental gradients such as opening size. Families such as Staphylinidae (rove beetles) and Trombidiidae (red velvet mites) were not favored by higher canopy openness while families such as Acrididae (grasshoppers) and Lycosidae (wolf spiders) were captured more in openings than in the forest matrix. Landing rates of wood-boring insects such as Buprestidae (metallic wood-boring beetles) and Xiphydriidae (wood wasps) were significantly higher on seed trees in group-selection openings than in reference plots (P < 0.05). Our results suggest that integrating group-selection openings within northern hardwood forests can lead to an increase in the family-level diversity of ground-dwelling arthropods, at least in the short term. Furthermore, seed trees left in such openings may be more attractive to bark- and wood-boring insects, which warrants further investigation into the susceptibility of these seed trees to damage by certain insect pests.  相似文献   

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