Uncut Reference Research Articles

Short‐term effects of organic matter and compaction manipulations on soil temperature, moisture, and soil respiration for 2 years in the Oregon Cascades

AbstractUnderstanding the factors controlling nutrient dynamics can help guide forest management plans to promote their long‐term productivity. We used experimental treatments with three levels of biomass removals and two levels of compaction to monitor the impacts to soil biophysical characteristics in an intensively managed forest. Soil temperature, moisture, and respiration observations began 6 mo after treatment installation completion and continued for 2 yr. Compaction had few consistent significant effects on measured variables, and there were negligible differences in volumetric soil water content between whole tree (WT) and bole only (BO) harvesting. Compared with BO, the 10‐cm average and maximum growing season temperatures in WT significantly increased by 1.2 and 2.5 °C, respectively. The effects of WT removals resulted in whole profile (10–100 cm) increases in the average and maximum growing season soil temperatures. The WT removals resulted in an increase of 1.4 times more soil growing degree days (SGDD) at 10 cm and 1.6 times more at 100 cm compared with BO. Despite favorable temperature and moisture conditions, differences in soil respiration could not be explained by biomass or compaction treatments. The uncut reference forest was consistently cooler and drier, but respired more CO2 throughout both years of observation compared with treated areas. The large physical disturbance of forest harvesting on the site likely masked any incremental treatment differences by homogenizing the microbial response in the ensuing 2‐yr study period. Future research should continue to investigate whether these soil biophysical changes influence site productivity or more sensitive indices of soil C dynamics.

Soil nutrient recovery after shelterwood timber harvesting in a temperate oak hardwood forest: Insights using a twenty-five-year chronosequence

Understanding the effects of forest timber harvests on soil chemistry is essential to manage for a sustainable yield of timber from forests. Yet few studies have examined the long-term effects of timber harvesting on the soils of temperate hardwood forests. We use a 25-year chronosequence of post-regeneration irregular shelterwood harvests in an oak-hardwood forest in Connecticut, USA to examine the impacts of timber harvesting and subsequent forest regeneration on soil and leaf litter chemistry. Soil and leaf litter samples were collected across 34 stands ranging in age from one year to 25 years since harvest. Using hierarchical, linear mixed effects models, we analyzed trends in soil and leaf litter properties over time in the harvested stands and compared these values to undisturbed reference sites. Soil chemistry from two depths (0–10 and 10–20 cm) revealed that surface and sub-surface soils respond differently through time, with the shallow soils being more responsive to harvest and regeneration, but both increasing in fertility with increasing time since harvest. In shelterwood soils, time since harvest had a positive effect on macronutrient concentrations and a negative effect on the carbon (C) stable isotope ratio (δ13C), with the latter indicative of recovery of faster-cycling soil C pools. In leaf litter, time since harvest had a positive effect on nitrogen (N) concentrations and a negative effect on δ13C, with the latter again suggesting build-up of more recent litter inputs. Relative to eight unmanaged reference sites, harvested stands were lower in some soil nutrients (magnesium, phosphorus, percent C, as well as cation exchange capacity), but these differences were recovered over time within the 25-year chronosequence. Post-hoc t-tests (α = 0.10) showed no significant difference in percent nitrogen by 11–15 years post-timber harvest as compared to the undisturbed sites. Likewise, potassium, phosphorus and percent carbon showed no difference by 16–20 years, and magnesium showed no difference by 21–25 years. Calcium never varied significantly between shelterwood and uncut reference sites. Overall, our results suggest that decomposing organic matter acts quickly to promote macronutrient recovery in surface soils following irregular shelterwood harvests.

Effects of harvesting intensity, vegetation control and fertilization on 5–20 year post-harvest N availability in boreal jack pine and black spruce forest soils in northern Ontario, Canada

The impact of harvesting intensity, vegetation control and fertilization on soil N availability 5–20 years post-harvest was determined at 18 jack pine and black spruce forests in northern Ontario, Canada. The study sites are affiliated with the North American long-term soil productivity (LTSP) study. Boreal forest growth is commonly N limited and young stands approaching crown closure acquire most of their N from the soil. The study sites represented a range of soil types and were harvested with three levels of organic matter removal (stem-only harvest, full-tree harvest and full-tree harvest with organic horizon removal by blading). Three study sites had multiple applications of glyphosate to control competing vegetation and one site included a trial with two applications of N, P, K fertilizer to the full-tree harvest treatment. We used short-term anaerobic laboratory incubations and in-situ closed top tube growing season incubations to determine mineralizable N and net N mineralization, respectively. Profile (organic plus mineral horizons) mineralizable N pools were higher in operational clearcut (stem-only and full-tree harvesting) treatments compared to the uncut reference forest 10–14 years post harvest. Full-tree harvesting with blading significantly reduced profile mineralizable N pools at this time compared to operational harvesting, while the same treatment at one upland site also reduced net N mineralization pools. Profile mineralizable N pools and microbial biomass C and N were lower in full-tree compared to stem-only harvesting treatments, suggesting that increased slash retention with stem-only harvesting was playing a role in enhanced soil N availability at a time when plantations were approaching a period of greater N demand. Fertilization and vegetation control treatments had few effects on N indices, although net N mineralization pools for the stem-only and full-tree harvest that also had the repeated herbicide treatment were consistently, but not significantly, lower than non-herbicided treatments. Soil N indices were useful predictors of dominant height growth for jack pine to a greater degree than for black spruce, and soil N concentrations were as effective at predicting height growth as more resource intensive measurements. Our results point to the importance of continued monitoring of soil and stand conditions at these LTSP sites as treatment effects on soil N cycling and site productivity will likely continue to evolve. At this stage of stand development, full-tree harvesting plus organic horizon removal, followed by operational harvesting has led to lower soil N availability than operational tree-length harvesting, and stands with understory vegetation control are now showing indications of reduced N availability.

Time-lagged lichen extinction in retained buffer strips 16.5 years after clear-cutting

Tree retention on clear-cuts is a relatively new measure in forestry aimed at ‘lifeboating’ forest species during young seral periods. However, the effectiveness of tree retention for maintaining biodiversity for more than a few years is still poorly known. We investigated lichen persistence in retained buffer strips along small streams after clear-cutting of the surrounding forest, and compared with clear-cuts and un-cut references. Specifically, we compared richness and frequency of red-listed/signal species, calicioids and pendulous species before clear-cutting with 2.5 years and 16.5 years after clear-cutting, and also analysed their colonization-extinction dynamics over time. The results show that the richness of red-listed/signal species and calicioids in buffer strips had declined significantly after 16.5 years, but not after 2.5 years, while frequency displayed a significant difference already after 2.5 years. The richness of pendulous lichens remained relatively stable over time, but the frequency had declined significantly after 16.5 years. In clear-cuts all groups declined more than in buffer-strips (~2–3.5 times more) and the main decline had occurred already after 2.5 years. References remained stable over time. The colonization-extinctions dynamics reflected the richness declines, with high early extinction in clear-cuts and lower but late extinction in buffer-strips, and low (re)colonization. We conclude that retained buffer strips cannot maintain lichen richness over time due to time-lagged extinction, but they are clearly more effective than clear-cuts. Wider buffer strips could potentially reduce tree mortality and decrease lichen extinction. The large amounts of standing dead wood makes buffer strips potential future colonization targets.

American Woodcock and Golden-Winged Warbler Abundance and Associated Vegetation in Managed Habitats

Abstract Vermivora chrysoptera (Golden-winged Warbler) and Scolopax minor (American Woodcock, hereafter, Woodcock) are 2 young-forest-dependent species of eastern North America that are experiencing population declines due to loss of breeding habitat. The goals of our study were to compare avian abundance and habitat similarities and differences in sites used by the 2 species. A portion of our survey plots were manipulated under Woodcock or Golden-winged Warbler habitat prescriptions in managed shrublands, and others were on regenerating timber-harvest sites. In north-central PA, we compared Woodcock abundance in 10-ha experimental plots assigned to one of 3 habitat prescriptions: uncut controls, Woodcock strip plots, and Golden-winged Warbler mosaic plots. We also quantified vegetation characteristics in each 10-ha study plot. Woodcock density was higher in the strip (4.8 males/10 ha) and mosaic (5.1 males/10 ha) plots compared to the uncut reference plots (3.3 males/10 ha). Woodcock density was negative...

Influence of Forest Disturbance on Stable Nitrogen Isotope Ratios in Soil and Vegetation Profiles

Soil and plant stable N isotope ratios (δ15N) are influenced by atmospheric N2 inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting δ15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems, longleaf pine (Pinus palustris Mill.)–wiregrass (Aristida stricta Michx.) (LLP) and Appalachian hardwood (AHW) forests in the US Southeast under different management regimes. In LLP, burning removes OM. In AHW, clearcutting creates large OM pulses of logging residue. Although burning removes OM and clearcutting creates a pulse addition of OM, both management regimes increase soil N availability and N2–fixing plants. The LLP treatments included burning every 2 yr with N2 fixers and reference fire exclusion sites without N2 fixers. The AHW included 25-yr-old clearcut plots with and without N2 fixers, and uncut reference without N2 fixers. We hypothesized that: (i) compared with the reference, OM removal (LLP) would enrich δ15N values while OM addition (AHW) would deplete δ15N in soil and vegetation pools; and (ii) N2 fixers would mitigate δ15N enrichment in LLP response and exacerbate δ15N depletion in AHW. We examined total δ15N in soil profiles, tree increment cores, and foliage. The LLP soil and vegetation δ15N values showed no treatment effect. In AHW, δ15N values in clearcut subsurface soils (20–60 cm) were lower than the reference, but N2 fixers had no effect. Wood δ15N differed with treatment; N2 fixers had no effect. Our data suggest that AHW soil profile δ15N patterns may indicate past disturbance; however, wood and foliar δ15N response is species specific. Additionally, N2–fixing plants respond to ecosystem disturbance, but the data suggest that they play little role in soil or plant δ15N values.

Harvest-Created Canopy Gaps Increase Species and Functional Trait Diversity of the Forest Ground-Layer Community

Biodiversity conservation within managed forests depends, in part, on management practices that restore or maintain plant community diversity and function. Because many plant communities are adapted to natural disturbances, gap-based management has potential to meet this need by using the historical range of variation in canopy disturbances to guide elements of harvest design. We tested this hypothesis with a well-replicated gap size experiment in a second-growth northern hardwood forest. We evaluated plant communities within and among experimental gaps of differing size, 13 years after an initial harvest. We used a resampling approach to estimate how conventional and gap-based management affect diversity partitioning and species and trait diversity of ground-layer plants. These diversity measures highlight relevant scales and function of ground-layer plants among harvest gap sizes and scenarios. Results from our field experiment showed that, at the gap-level, increasing gap size increased functional trait diversity of plants, while species diversity was higher in gaps than uncut references and maximized in medium-sized (20‐30 m diameter) gaps. In harvest scenarios created by resampling our empirical data, we found that at the stand scale, increasing harvest intensity (larger gaps and greater proportion of forest in gaps) increased species richness and variability in initial bloom times, tolerance to shade, and number of life-forms in the plant community. Based on the measures of diversity and function used in our study, our results suggest that size of harvest-created gaps and proportion of forest in gaps can be manipulated to attain biodiversity goals but evaluating the regional species pool and seed sources (e.g., presence of invasives, rare species) will be important to maintain or restore conservation value.

Do deer and shrubs override canopy gap size effects on growth and survival of yellow birch, northern red oak, eastern white pine, and eastern hemlock seedlings?

Innovative forestry practices that use natural disturbance and stand developmental processes as models to increase forest complexity are now being considered as a way to conserve biodiversity while managing for a range of objectives. We evaluated the influence of harvest-created gap size (6, 10, 20, 30, and 46m diameter gaps and uncut references) over 12 growing seasons on planted tree seedling growth and survival for four tree species that tend to experience poor recruitment in both managed and unmanaged northern hardwood forests in eastern North America. We expected, based on silvics, that the three mid-tolerant species (yellow birch [Betula alleghaniensis], red oak [Quercus rubra], and white pine [Pinus strobus]) would perform best in intermediate-sized gaps, and the one shade tolerant species (hemlock [Tsuga canadensis]) would perform best in small gaps. However, all four of the species grew taller with increasing gap size, while survival was highest in intermediate gap sizes. Although gap size had statistically significant effects on growth and survival, the magnitude of the effects were modest. With the exception of a small portion of white pine individuals (35% of survivors were >150cm tall), trees were short (<1m) and few survived (<30%) 12years after planting. Evidence from deer exclosures and individual gaps with high shrub (Rubus idaeus) densities suggest that browsing and shrub competition resulted in poor tree growth and survival, and may have constrained the magnitude of many potential tree seedling responses to gap size. Our study highlights the management challenges of using gap size as a tool to influence future forest composition in forests with overly abundant deer and pervasive shrub layers and underscores the importance of silvicultural prescriptions that include measures for reducing these impacts.

Early seedling response to group selection harvesting in a northern hardwood forest

We evaluated the immediate effects of group selection harvesting on the establishment of yellow birch (Betula alleghaniensis Britt.) and black cherry (Prunus serotina Ehrh.) seedlings in maple-dominated hardwood stands of Algonquin Provincial Park, Ontario. Group selection gaps were compared to single-tree selection cutting and uncut reference stands pre-harvest and one growing season post-harvest using a before-after-control-impact (BACI) design. The percent cover of yellow birch seedlings increased significantly more in gaps than in single-tree selection and reference plots. Black cherry seedling cover increased significantly more in gaps than in reference plots, but increased at a similar rate in gaps and single-tree selection plots. Increased soil exposure and closer seed trees resulted in increased yellow birch recruitment when harvesting occurred in the late-summer-fall. These factors had little influence on yellow birch recruitment when harvesting occurred in the winter. The proportion of black cherry in the stand overstory had the greatest influence on black cherry recruitment; however, the uneven distribution of black cherry between stands may have precluded our ability to reliably test the influence of other factors. Concomitant increases in potential competitors such as wild red raspberry (Rubus strigosus Michx.) and sedges (Carex spp.) and the continued dominance of sugar maple (Acer saccharum Marsh) in gap openings may limit yellow birch and black cherry regeneration in successive growing seasons. While continued monitoring is required, our short-term results demonstrate that fall harvesting with group selection is effective at stimulating natural regeneration of yellow birch and black cherry. Key words: yellow birch, black cherry, seedling recruitment, group selection, single-tree selection, mid-tolerant, shadeintolerant

Short-term Effects of Clear-cutting on the Water Chemistry of Two Boreal Streams in Northern Sweden: A Paired Catchment Study

The effects of clear-cutting on stream-water chemistry in northern Sweden remain largely unexplored. Here we report data collected during a reference period and the first two years after logging in two typical partially harvested northern catchments; the objective was to compare water chemistry along the stream with and without a forest buffer. Two typical uncut reference catchments are included for comparison. Runoff was measured at the outlet of each catchment, and water samples were generally taken every second week and analyzed for 20 constituents. Logging resulted in increased runoff and increased concentrations of sodium, potassium, chloride, total nitrogen, total phosphorus, and suspended material from both catchments. Nitrate (NO3-) leaching increased only from the catchment without a forest buffer. It has not yet been possible to evaluate fully the effects of the forest buffer on the NO3- leaching because the uphill clear-cut area leached minimal amounts of NO3-.

Riparian zones in southern Appalachian headwater catchments: Carbon and nitrogen responses to forest cutting

There is little understanding about the role eastern US forested headwater riparian areas play in protecting aquatic habitats and water quality from impacts of side slope forest harvest. To better understand this important riparian area function, we selected three sites from management units with a 2-age regeneration silvicultural prescription located on the Nantahala National Forest, North Carolina, USA. Each site was harvested and a riparian buffer was left uncut along the stream. Buffer widths were 10 m and 30 m; we included a 0 m buffer to experimentally determine nutrient and riparian zone responses to forest cutting under extreme conditions. A fourth site was selected to serve as an uncut reference. Transects were established perpendicular to a 200 m stream reach, from streamside to 50 m upslope for intensive study. Forest cutting increased extractable NO 3 − at both 0–10 cm and 10–30 cm soil depths compared to pre-treatment concentrations. Soil solution NO 3 − concentrations increased only in harvested areas, on all sites; increases were greater in sites with narrow riparian buffers. Stream water NO 3 − concentration increased significantly following site harvest only on the 0 m buffer site. Dissolved organic C and N did not respond to harvesting in either soil solution or stream samples. Our results suggest that riparian buffers are effective in removing NO 3 − from soil solution prior to its entering the stream.

Short-term response of the herbaceous layer within leave patches after harvest

Leave patches, uncut areas in a harvested forest, may conserve herbaceous layer species that decline after forest clearcutting. They may also serve to maintain source populations for the recolonization of the harvest area. The main objective of this study is to characterize the short-term response of the herbaceous layer to clearcut harvesting disturbance within and adjacent to leave patches. Four experimental 1 ha patches and two uncut references were established. Within each patch or reference, belts of five 1 m 2 quadrats were placed at 50 m and 5 m outside the patch, at 0 m (edge), and at 25 m, 35 m, and 50 m (centre) inside. These belts of quadrats were replicated at all four aspects (North, South, East, and West). Ground vegetation was sampled yearly for 1 year before harvest and 3 years after harvest in the experimental patches and for 2 consecutive years in the references. Some common residual species declined significantly in the clearcuts, but remained stable inside the patches in the short term (3 years after harvest). Overall species composition changed little in the patch interior and edge after harvest. Colonizing species (those that appeared in quadrats after harvest) in the patch exterior were predominantly early-seral species, whereas colonizers in the patch interior tended to be shade-tolerant forest species. Species were grouped a priori based on two habitat preferences (amounts of canopy cover and disturbed substrate). Species characteristic of a habitat with closed canopy and undisturbed substrates that decreased significantly over time in the patch exterior were negatively correlated with the amount of exposed mineral soil and open canopy. Species characteristic of a habitat with open canopy and disturbed substrates that increased significantly at the patch exterior showed a positive correlation with the amount of exposed mineral soil and open canopy. No species’ habitat preference groups declined significantly in the patch interior or edge over time. Based on species’ responses to forest operations, it appears that at least the common forest species are maintained in the short term within leave patches.

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.

Microbial community responses in forest mineral soil to compaction, organic matter removal, and vegetation control

We tested three disturbance hypotheses in young conifer plantations: H1: soil compaction and removal of surface organic matter produces sustained changes in microbial community size, activity, and structure in mineral soil; H2: microbial community characteristics in mineral soil are linked to the recovery of plant diversity; and H3: community responses are strongly modified by regional climate. Microbial biomass, respiration, carbon utilization, and phospholipid fatty acids were compared at two subtropical installations and one Mediterranean-type climate installation of the North American Long-Term Soil Productivity study. Treatments included combinations of compaction (none vs. severe), organic matter removal (none vs. complete), and weed control (none vs. complete), plus an uncut reference stand. Weed control resulted in the only consistent decline or shift in microbial indices at the subtropical sites. At the Mediterranean-type climate site, overstory harvesting resulted in declines in microbial biomass, respiration, and fungal phospholipid fatty acids that far outweighed the effects of the soil disturbance treatments. Severe compaction had no effect on community size or activity at any site. Microbial communities were generally tolerant of postharvest soil disturbance, leading to a rejection of the experimental hypotheses, with the exception of a link between microorganisms and recovery of plant diversity (H2) at the subtropical sites.

Macroinvertebrate response to logging in coastal headwater streams of Washington, U.S.A.

We examined the effects of logging on macroinvertebrate assemblages in first-order streams of four coniferous watersheds in Washington's Coastal Mountain ranges. Each watershed contained three to four first-order streams that were placed into one of three treatment types: clear-cut logging, operational buffer-strip (2.5–21 m) logging, or uncut reference streams. Prelogging baseline data on macroinvertebrate assemblages, channel morphology, sediment composition, sediment accretion rates, and water temperatures were collected from each stream in summer 1998. Logging operations were conducted the next winter and spring. Streams were resampled in summer 1999, within 1 year of logging, and summer 2000, 1+ years after logging. Preexisting treatment differences did not exist in 1998, indicating that postharvest treatment differences could be attributed to logging operations. In 1999, densities of macroinvertebrate collectors, densities and biomass of macroinvertebrate shredders, and accretion rates of organic sediments were greater in clear-cut and buffered streams than uncut references. These differences diminished by 2000. An increase in collecting and shredding macroinvertebrate is not a typical response to logging and may reflect the fact that logged streams became buried under slash, increasing detrital food supplies for these organisms. The narrow buffers used for this study did not prevent macroinvertebrate community changes associated with logging.

Restoration of Wet Dune Slacks on the Dutch Wadden Sea Islands: Recolonization After Large‐Scale Sod Cutting

AbstractThe effects of sod cutting were studied in a dune area on the Dutch Wadden Sea Island of Texel. Sod cutting was carried out in a range of different dune slacks in order to restore dune slack vegetation with many endangered Red List species. Sod cutting removed approximately 96% of the soil seed bank. Species abundant in the seed bank, notably Juncacea, also had a high frequency in the vegetation that established during the first year after the restoration measures. Many other species not registered in the seed bank or in the former vegetation also appeared. Species richness in the monitored plots exceeded that of uncut reference plots after a few years. Colonization rates were higher than extinction rates in most plots, indicating that a stable state has not been reached after 5 years. Differences in species richness between slacks appeared to be related to the occurrence of source areas nearby and availability of dispersal agents, such as flooding and animals.

Litterfall, Nitrogen and Phosphorus Inputs at Various Levels of Canopy Removal in Oak and Pine Stands in Northern Lower Michigan

-Relatively little is known about the comparative effects of varying degrees of canopy cover in oak and pine stands on litterfall quantity and quality, which in turn have a major influence on litter decomposition rates and nutrient cycling processes. Thus, changes in litterfall and nutrient (N and P) inputs were examined over the 1st 2 yr following various levels of canopy removal in northern red oak ( Quercus rubra L.) and red pine (Pinus resinosa Ait.) stands in northern Lower Michigan. Selective canopy removal in experimental plots resulted in 25% (50% during the 1st yr) and 75% canopy cover. Comparisons were made with uncut references, which had an average canopy cover of 85%. As expected, the uncut stands had the highest litterfall during the 2-yr period (oak, 393 g m-2 yr-l; pine, 430 g m-2 yr-'), whereas the most heavily cut stands (25% canopy cover) had the lowest values (oak, 118 g m-2 yr-'; pine, 104 g m-2 yr-'). A small amount of canopy removal (75% canopy cover) in red oak stands led to significant reduction of litterfall and nutrient inputs, whereas the same treatment in red pine stands had little effect. In contrast, litterfall following the 25% canopy cover treatment decreased more in red pine stands than in red oak stands compared to the uncut stands. Annual total leaf litter N inputs at the same canopy cover levels were higher in red oak stands than in red pine stands. Lower N inputs in red pine stands were attributed to the low N concentrations in needle litter throughout the year, not to total leaf litter mass differences. These results indicate that the amount and quality of canopy removal were key factors in determining litterfall and nutrient inputs in these stands.

Soil and detrital carbon dynamics following forest cutting in the Southern Appalachians

Soil-system CO2 efflux and detrital C pools were measured in three hardwood watersheds in the Southern Appalachians, USA. On two of the watersheds (hereafter referred to as clearcuts), forests were cut via clearcut logging methods and allowed to naturally regenerate; logging residue was removed on one clearcut and was left in place on the other. The third watershed was an uncut reference watershed. There was no statistically significant difference in CO2 efflux between the two types of residue treatments on the clearcuts; however, CO2 effluxes from the clearcuts were 33% less than effluxes from the uncut watershed. Lower CO2 effluxes on the two clearcuts were associated with higher soil temperatures, smaller live-root masses, and larger forest-floor masses. No long-term (5–8 years) changes in soil C pools were apparent following forest cutting. Therefore, reductions in CO2 efflux on the clearcuts appear to be due both to fewer live roots and to slower rates of forest-floor decomposition. Cutting of these forests followed by regeneration does not appear to result in large net C transfers to the atmosphere, as has been generally assumed.

Effects of Clear-cut Logging on Wood Breakdown in Appalachian Mountain Streams

Red oak (Quercus rubra) sticks, approximately 10-cm long and in three size classes (large, 3-cm diam, 22-55 g; medium, 1-2-cm, 12-22 g; small, < 1-cm, 312 g) were placed at five sites in two second-order streams at Coweeta Hydrologic Laboratory. One stream, Big Hurricane Branch, drains a watershed logged in 1976 (WS 7); the other stream, Hugh White Creek, drains an uncut reference watershed (WS 14). Ten sticks of each size class were collected from each site at 6-month to 1year intervals from September 1981 through November 1985. Calculated breakdown rates ranged from 0.107 to 0.281 y-1. Breakdown rates were significantly different among size classes on both watersheds-smaller sticks lost mass faster than larger sticks. Breakdown rates of similar size sticks were significantly faster in Big Hurricane Branch, the disturbed stream, than in Hugh White Creek. Faster rates of wood breakdown in Big Hurricane Branch may be associated with higher stream N03-N levels, greater stream channel instability and greater invertebrate abundance on sticks.

Effects of forest clearcutting in New England on stream macroinvertebrates and periphyton

Clearcutting may alter stream biota by changing light, temperature, nutrients, sediment particle size, or food in the stream. We sampled macroinvertebrates during late summer of 1979 in first and second order headwater streams draining both two- and three-year-old clearcuts and nearby uncut reference areas in northern New England, USA. Periphyton were sampled throughout the summer by placing microscope slides in these streams for 13–37 days. Periphyton cell densities on these slides following incubation were about six times higher in cutover than in reference streams. Green algae (Chlorophyceae) accounted for a higher proportion of total cell numbers in cutover than in reference streams, whereas diatoms (Bacillariophyceae) dominated the reference streams. The macroinvertebrate density in cutover streams was 2–4 times greater than that in the reference streams, but the number of taxa collected was similar in both cutover and reference streams. Higher numbers of mayflies (Ephemeroptera) and/or true flies (Diptera) in the cutover streams accounted for the differences. Because nutrient concentrations in the cutover streams were nearly the same as those in the reference streams, these differences in macroinvertebrate and periphyton densities were apparently caused by higher light levels and temperature in the streams in the clearcuts. Leaving buffer strips along streams will reduce changes in stream biology associated with clearcutting.