Uncut Sites Research Articles

Strip Clearcutting Drives Vegetation Diversity and Composition in the Moso Bamboo Forests

Abstract Strip clearcutting of Moso bamboo forests in southern China has seen increasing interest as a way of reducing harvesting costs. Previous research has shown that cutting influences the overstory structure and drives changes in the microclimate and soil properties. However, the effects of strip cutting on understory vegetation diversity and composition remain unclear. To better understand the influence of cutting on the understory vegetation, this study compares sites under natural restoration after cut and uncut sites in the Moso bamboo forest. We selected plots that were cut in 2019 (C19) and 2017 (C17), as well as unharvested plots as controls (CK). The results showed that strip clearcutting increased the understory vegetation richness and diversity, and a significant difference (A = 0.23, P = 0.001) existed in the composition of the vegetation between the three treatments. Furthermore, the decrease of soil total phosphorus and total potassium content resulted in the difference in undergrowth vegetation distribution and composition between the uncut plots and the cut plots. Our results suggest that strip clearcutting may not be harmful to biodiversity on a local scale in the Moso bamboo forest.

Long-term effects of prescribed burning, tree retention, and browsing on deciduous tree recruitment in European boreal forests

Silvicultural practices, effective fire suppression, and increased browser densities have profoundly altered structural diversity in boreal forests. Prescribed burning and retention forestry may counteract losses in structural diversity in managed forests by maintaining a higher deciduous admixture. We constructed an experiment on 18 sites with three types of timber harvesting (uncut, cut with retention, and clearcut) and burned half of these sites. Subsequently, we established a herbivore treatment with three compartments (unfenced, fenced excluding moose (Alces alces (Linnaeus, 1758)), and fenced excluding moose and hares (Lepus spp.)). In these compartments, we planted rowan (Sorbus aucuparia L.), European aspen (Populus tremula L.), and silver birch (Betula pendula Roth) seedlings and monitored these for 17 years. Birch and rowan mortality were lower on cut and burned sites, with retention further enhancing birch survival on these sites. Retention without burning did not lower seedling mortality of any tree species. While browsing resulted in greater mortality on cut sites, burning appeared to greatly reduce browsing on birch and rowan. On mature uncut sites, seedlings of all tree species exhibited high mortality. Our findings show that deciduous tree recruitment can be improved through prescribed burning, particularly for birch and rowan, and that browsing impacts on deciduous trees depend on forest age.

Emulating natural disturbance in forest management enhances pollination services for dominant Vaccinium shrubs in boreal pine-dominated forests

Lack of natural disturbances and the homogenization of boreal forest because of intensive forest management pose a threat to biodiversity and can endanger the provision of ecosystem services. In this study, we assessed how two methods aimed to promote biodiversity, i.e. prescribed fire and retention forestry (RET), affect ecosystem services supported by bilberry and lingonberry in Scots pine-dominated boreal forests. Shrub cover, flowering, berry yield and percent fruit set of both shrubs were measured and bees were sampled by pan-traps on 24 study sites 13years following a large-scale experiment, where RET (0, 10, 50m3/ha and uncut forests) and fire (yes/no) were manipulated following a replicated factorial design. In general, bilberry performance and reproduction were higher at uncut sites, while lingonberry flowering was positively affected by fire and retention. Bee community composition was mainly determined by percentage of bare ground and number of logs within sites, both nesting resources largely determined by fire and retention. Burnt sites with retention trees serve as pollinator source habitats and contain floral resources, highlighting the importance of natural disturbances and biological legacies in the conservation of pollination services from boreal forests.

Nutrient and heavy metals in decaying harvest residue needles on drained blanket peat forests

Harvest residue decomposition can significantly contribute to nutrient and heavy metal exports to receiving water courses. This study monitors the nutrient and heavy metal dynamics in decaying Sitka spruce and lodgepole pine harvest residue needles on Atlantic blanket peat forests in the west of Ireland. Using the litterbag method, harvest residue was placed both within and between furrows in two uncut forest and two clear-cut sites. On the clear-cut sites, the litterbags were positioned outside the harvest residue piles (i.e. brash windrows). Over the 2-year monitoring period, the needles decomposed slower at the clear-cut sites than the uncut forest sites, with mass losses of 46–55 and 58–77 %, respectively. Approximately 20 % less phosphorous (P) was released from the decaying needles at the clear-cut sites, while nitrogen (N) was released only at the uncut sites. Tree species was a significant factor contributing to nutrient and heavy metal release and accumulation patterns, with higher concentrations of aluminium (Al), nickel (Ni), cadmium (Cd) and zinc (Zn) in the decaying spruce needles than in pine. Conversely, the spruce needles showed accelerated depletion of calcium (Ca) and magnesium (Mg) relative to the pine. The harvest residue needle positioning (inside furrow/between furrows) and the site soil characteristics contributed significantly to Al transformations in spruce needles and iron (Fe) in both spruce and pine needles, with more accumulation occurring inside the furrows where Al and Fe contents of the peat were high. Manganese (Mn) was released from the needles in three of the four sites with a total release of over 90 % within 2 years. In the remaining site, where the Mn content of the peat was high, an accumulation of Mn in the needles was observed. The decomposition of needles on blanket peat catchments may be a significant source of P to receiving water courses, owing to their fast release of P, but not a likely source for N export.

Post-fire natural regeneration of young stands on clearcut and partial-cut and uncut sites of boreal mixedwoods

Boreal mixedwoods are an important element and the most productive forest type in the Canadian boreal forests. However, they experience frequent disturbances. In order to better understand the responses of boreal mixedwoods to different combinations of anthropogenic and natural disturbances, we investigated the natural regeneration of boreal mixedwoods that were previously subjected to three different harvesting treatments (clearcut, partial-cut and uncut control) and naturally regenerated, but subsequently burnt by a severe natural fire 6 years later. The study was conducted 8 years following the fire. Significant interactions were found among harvesting method, species and block in several regeneration variables. There were a total of 12 woody species (trees and shrubs) regenerated, but not all the species were present in all the sites. In general, the species richness and species diversity of the new stands were lowest on clearcut sites while the differences between partial-cut and control varied with blocks. However, the combined total density for all species was lowest on uncut control sites. Density and regeneration index data show that trembling aspen was the predominant tree species in all stands except at one uncut control site where jack pine was the dominant species. The density of trembling aspen generally declined from clearcut to partial to the uncut control. Pincherry, beaked hazel and mountain maple were the dominant shrub species in the new stands, but no general patterns were found in terms of variations in density with harvesting methods for any of the shrub species. Jack pine and white birch were the tallest tree species in the clearcut treatment while white birch was taller than jack pine in the partial-cut and control. The results suggest that active measures are necessary to restore the complex structure of the initial mixedwoods.

Breeding bird communities of upland hardwood forest 12 years after shelterwood logging

Abstract We studied the relationship between the effects of shelterwood logging on forest structure and long-term abundance, diversity, and richness of breeding bird communities in an upland hardwood forest at Land Between The Lakes (LBL), Kentucky and Tennessee. Breeding bird communities (point counts in 1987–1989, 1999) and forest vegetation structure (1987–1988, 1999), the year prior to, 1 and 2 years after, and 12 years after shelterwood logging were compared between logged and uncut (>40 years since logging) forest sites. Shelterwood sites had significantly greater mid-story canopy. General avian community trends demonstrated an initial increase in diversity and density the year following logging, and decreased diversity and density in 1999. Uncut sites showed a general decline in diversity in 1989 and 1999. The influence of shelterwood logging varied among taxa and among foraging guilds. Specifically, the ground-gleaning guild was significantly more diverse on uncut sites than on shelterwood sites. We attribute this greater diversity to a more complex and diverse forest understory with greater opportunity for foraging. Logging did not significantly influence diversity, evenness, or richness of the nesting guilds. We examined four priority species of concern (as designated by Partners in Flight): Wood Thrush (Hylocichla mustelina), Worm-eating Warbler (Helmitheros vermivorus), Kentucky Warbler (Oporonis formosus), and Hooded Warbler (Wilsonia citrina). Of these, population densities of Wood Thrush were significantly lower on logged sites than on uncut sites while worm-eating warblers were higher on logged sites. The Kentucky Warbler and Hooded Warbler did not occur on logged sites. Higher densities of birds in our study sites compared to regional surveys suggest LBL is an important local area for breeding bird communities.

Influence of variable retention harvests on forest ecosystems: Plant and mammal responses up to 8 years post-harvest

Green-tree retention systems are an important management component of variable retention harvests in temperate zone coniferous forests. Residual live trees (“legacy trees”) provide mature forest habitat, increase structural diversity, and provide continuity in the regenerating stand. This study was designed to test the hypotheses that, at up to 8 years after harvest, abundance and species diversity of communities of (i) understory plants and (ii) forest-floor small mammals, and (iii) relative habitat use by mule deer ( Odocoileus hemionus), will decline with decreasing levels of tree retention. Communities of plants and forest floor small mammals were sampled in replicated clearcut, single seed-tree, group seed-tree, patch cut, and uncut forest sites in mixed Douglas-fir ( Pseudotsuga menziesii)—lodgepole pine ( Pinus contorta) forest in southern British Columbia, Canada from 2000 to 2003 (5–8 years post-harvest). Habitat use by mule deer was measured during summer and winter periods each year from 1999 to 2003 in these same sites. Mean total abundance (crown volume index) of herbs, shrubs, mosses, and lichens was similar among sites. Mean species richness of herbs, shrubs, and total plants was similar among sites, but total species diversity and structural diversity were significantly lower in the patch cut and uncut forest sites than in the other harvesting treatments. Thus, hypothesis (i) was not supported. Mean total abundance, species richness, and species diversity of small mammals were similar among sites, contrary to hypothesis (ii). However, the southern red-backed vole ( Clethrionomys gapperi) declined in abundance as conditions became intolerable for this microtine to persist at numbers > 1/ha in the clearcut and seed-tree sites. The early successional and mycophagist northwestern chipmunk ( Tamias amoenus) occurred at 2.3–4.4 times higher abundance on the seed-tree sites than the other sites. Relative habitat use by mule deer was highest in the seed-tree sites during summer periods and highest in the group seed-tree, patch cut and uncut sites in winter periods. The responses to our treatments were species specific, and hence a range of different harvesting systems should be used to maintain plant and mammal diversity across forest landscapes.

Forest floor temperature and relative humidity following timber harvesting in southern New England, USA

Forest amphibians, especially salamanders, prefer forests with shaded, cool, and moist forest floors. Timber harvesting opens the forest canopy and exposes the forest floor to direct sunlight, which can increase forest floor temperatures and reduce soil moisture. These microclimatic changes can potentially degrade the harvested stand for amphibian habitat or affect other biotic resources or ecological processes at the forest floor and in the understory. The degree of forest floor disturbance is directly related to the intensity of harvesting, however, the duration of this effect is unknown. We conducted a study of forest floor temperature and relative humidity over a 12-year chronosequence (1993–2004) of timber harvests. We compared simultaneous, paired measurements of temperature and relative humidity at three positions (soil, forest floor, air) in harvested and control sites over three seasonal survey sessions. Vegetation composition and structure were measured at each survey location. Ambient weather conditions were recorded at three open-field locations across the study area.We recorded over 23,000 paired measures of temperature and relative humidity at all 12 harvested and control sites during each survey session. While we found significant effects of time-since-harvesting on differences in temperature between harvested and uncut sites, the average differences were generally small (<1°C). We observed no temporal pattern in temperatures with time-since-harvest in the harvested sites compared to uncut conditions. Time-since-harvest had no effect on differences in relative humidity between cut and uncut sites. The variation in forest floor microclimate among sites was large, likely due to small-scale differences in cutting intensity (retained canopy), understory vegetation growth, and microtopography or aspect. We conclude that timber harvesting, within the range of intensities assessed in this study, would have only minimal and short-term effects on forest floor microclimate. We suggest that the small differences we observed in forest floor temperatures and moisture between cut and uncut forest parcels would likely have minor effects on climatic aspects of forest amphibian habitat, and on climatic influences on other forest floor biota and ecological processes.

Habitat attributes and chestnut-backed chickadee nest site selection in uncut and partial-cut forests

We examined the relationship between habitat attributes and nest-site selection by chestnut-backed chickadees ( Poecile rufescens (Townsend, 1837); hereinafter chickadees) in uncut and partial-cut forests in northwest British Columbia. We described the characteristics of uncut sites and compared them with structurally modified partial-cut sites (mature and old forests). We then compared the use and selection of habitat by chickadees at uncut and partial-cut sites at three spatial scales: (1) the stand (19–24 ha uncut or partial-cut stand), (2) the nest patch (a 0.031 ha patch centered on nest trees), and (3) the nest tree. At the stand scale, we found no correlation between the density of breeding chickadees and the characteristics of uncut and partial-cut sites. At the nest-patch scale, chickadees in uncut and old partial-cut sites selected nest patches with higher densities of broken-top trees compared with available habitat within territories. At the nest-tree scale, chickadees selected nest trees with boring insects and broken tops in uncut and mature partial-cut sites and large trees with boring insects in old partial-cut sites. Our results suggest that chickadees exhibited flexibility in resource selection but also selected resources with similar attributes at the nest-patch and nest-tree scales. Managed stands that maintain a range of tree species and conditions, including live trees with areas of disease, insect attack, and damage, will provide the specific structural attributes used for nesting by weak cavity excavators such as the chickadee.

Northern and southern flying squirrel use of space within home ranges in central Ontario

Partial harvesting can reduce the supply of dead and diseased trees in forests and as a result is predicted to negatively influence flying squirrel habitat. In this study, we measured the home range and habitat use of 13 radio-collared southern flying squirrels ( Glaucomys volans) in selection logged and uncut hardwood forests, and 14 radio-collared northern flying squirrels ( G. sabrinus) in unlogged coniferous forest in Algonquin Provincial Park, Ontario. Locations were collected on southern flying squirrels in 2003, and on northern flying squirrels in 2004. Southern flying squirrel home range and core area size showed no differences between unlogged and recent selection-harvested sites. Compared to available locations, southern flying squirrels radio-locations in uncut sites were associated with higher densities of decayed and mast trees, and greater overstory tree diversity, whereas in recent cuts, they were associated with higher densities of mast producing shrubs. Northern flying squirrel used locations that were characterized by older, decaying conifer trees with high understory sapling density and abundant spruce trees. Southern flying squirrel core areas were near nests, whereas northern flying squirrel core areas appeared to be used for foraging activity. Selection harvesting appears to support sufficient food resources for southern flying squirrels in the short term to maintain populations. However, we obtained evidence that the supply of nest trees may be limited in cuts, which may negatively impact future flying squirrel populations. The close association between northern flying squirrels and decayed trees may explain why we found no northern flying squirrels in two partially logged stands, where logging reduced the number of decaying trees.

The effects of green tree retention and subsequent prescribed burning on ground beetles (Coleoptera: Carabidae) in boreal pine‐dominated forests

We studied how two methods to promote biodiversity in managed forests, i.e. green tree retention and prescribed fire, affect the assemblages of carabid beetles. Our experiment consisted of 24 study sites, each 3–5 ha in size, which had been prepared according to factorial design. Each of the eight treatment combinations determined by the two factors explored – tree retention level (0, 10, 50 m3/ha−1 and uncut controls) and prescribed use of fire (yes/no) – was replicated three times. We sampled carabids using pitfall traps one year after the treatments. Significantly more individuals were caught in most of the burned sites, but this difference was partially reflective of the trap‐catches of Pterostichus adstrictus. The fire did not increase no. of P. adstrictus in the uncut sites as much as in the other sites. Species richness was significantly affected by both factors, being higher in the burned than in the unburned sites and in the harvested than in the unharvested sites. Many species were concentrated in the groups of retention trees in the burned sites, but only a few were in the unburned sites. The species turnover was greater in the burned than in the unburned sites, as indicated by the NMDS ordinations. Greater numbers of smaller sized species and proportion of brachypterous species were present in the burned sites. Fire‐favored species, and also the majority of other species that prefer open habitats were more abundantly caught in the burned sites than in the unburned sites. Dead wood or logging waste around the traps did not correlate with the occurrence of species. We conclude that carabids are well adapted to disturbances, and that frequent use of prescribed fire is essential for the maintenance of natural assemblages of carabid beetles in the boreal forest. Small retention tree groups can not maintain assemblages of uncut forest, but they can be important by providing food, shelter and breeding sites for many species, particularly in the burned sites.

The effects of patch harvesting and site preparation on ground beetles (Coleoptera, Carabidae) in yellow birch dominated forests of southeastern Quebec

We studied the impacts of increasing size and number of gapcuts and the effects of site preparation by scarification on the species richness and community composition of ground beetles (Coleoptera: Carabidae), using pitfall traps in early-successional yellow birch dominated forests in eastern Canada. Catches of all carabids, forest specialists, and generalists were generally higher in uncut controls than in treatments. The catch of open-habitat specialists was generally lower in controls than in treatments. Although not significant, there was a common trend for scarification to decrease the catches of forest specialists and generalists. Bray–Curtis similarity measures and nonmetric multidimensional scaling ordination indicated that the composition of the carabid assemblage was more affected by harvesting treatment than by scarification. Carabid species composition varied consistently with increasing gap size and corresponded to the a priori generalized habitat-preference designations. Forest-specialist species were confined to uncut sites, while generalist species were widely distributed across all sites. Open-habitat species were found predominantly in clear-cut and two-gap sites. Hygrophilous species were consistently associated with two-gap, four-gap, and clear-cut sites. Small-gap harvesting is more favorable to the maintenance of the structure of natural arthropod assemblages than are traditional, larger clearcuts.

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m 2/ha residual basal area; a shelterwood cut (SW), with 9.0 m 2/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness ( S), Shannon–Wiener's index of diversity ( H′), and Pielou's evenness index ( E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.

Reed cutting affects arthropod communities, potentially reducing food for passerine birds

Winter cutting of Common Reed Phragmites australis (Poaceae) is increasing in Camargue, southern France, potentially affecting wetlands of high conservation value. We studied its impact on arthropods by comparing four cut and uncut sites with special respect to avian prey availability in the breeding season. The two most important prey groups for breeding passerines, spiders (Araneida) and beetles (Coleoptera), were identified to species in trap catches and diet samples. The arthropod assemblages differed significantly between cut and uncut sites. Phytophagous and saprophagous species showed contrasting responses. Numbers of homopterans increased in cut reed beds, where green Phragmites stem density was higher. Saprophagous woodlice decreased, presumably due to the reduced amount of litter. Densities of some vegetation-dwelling spider and beetle species were lower at cut sites, including two of the most preferred prey species for passerine birds. Consequently, large-scale mechanically harvested reed beds host altered arthropod communities, missing major food components used by vulnerable passerines. However, reed cutting on a small scale may increase habitat heterogeneity and species richness on a landscape level. To contribute to reed bed conservation, EU schemes should reward management that leaves uncut reed patches in the proximity of cut areas to permit their recolonization by arthropods.

Forest floor microarthropod abundance and oribatid mite (Acari: Oribatida) composition following partial and clear-cut harvesting in the mixedwood boreal forest

The effects of partial and clear-cut harvesting on abundance and community composition of forest floor microarthropods and oribatid mites were investigated in conifer and deciduous stands of the mixedwood boreal forest. Soil samples from clearcuts, strip-cut corridors in a partial cut, green-tree retention patches in a partial cut, and uncut control sites were collected 2.5 years after harvest and microarthropods were extracted, enumerated, and identified. Densities of microarthropod suborders were lower in the strip-cut corridors of the deciduous stands and significantly lower in the suborder Oribatida (oribatid mites). Changes in microarthropod community composition, decreased relative abundance of prostigmatid mites, and increased relative abundance of mesostigmatid mites were observed in corridor and clear-cut treatments. Lowered abundances and changes in community composition are likely due to compaction of the forest floor during harvesting. Selected oribatid mite species showed significantly lower abundances in clearcuts than in uncut sites, but diversity indices for oribatid mites were generally not significantly different between uncut sites and clearcuts. Changes in oribatid mite communities following harvesting were thus more quantitative (absolute abundance) than qualitative (diversity, composition), and as a result, use of oribatid mites as biological indicators of disturbance is limited because of the lack of changes in species composition.

Effect of winter cutting on the passerine breeding assemblage in French Mediterranean reedbeds

Common reed is increasingly harvested from the Mediterranean region toprovide thatching material to north European countries. The impact of thesemanagement practices on the fauna is poorly known. The aim of this study was toquantify the effect of reed cutting in the Mediterranean region through acomparative analysis of water regime, vegetation structure, arthropoddistribution and passerine assemblage at cut and uncut reedbeds in southernFrance. Cut reedbeds were characterised by a lower salinity, higher water levelin spring, and higher reed biomass than uncut reedbeds. Arthropod distributiondiffered consistently between cut and uncut sites, leading to a higher index offood available to passerines in cut reedbeds. Cut reedbeds had a similar birdspecies richness but a lower bird abundance, due to the significant decrease inMoustached Warblers and Bearded Tits at cut sites. The mild Mediterranean winterfavoured early growth of reed in spring, making harvested reedbeds suitable forbreeding of long-distance migrants such as the Great Reed Warbler and ReedWarbler. However, for the resident species that breed earlier in the season, cutreedbeds presumably lack sufficient vegetation cover to provide adequate nestingand feeding sites. Although biennial cutting (double wale) is considered as agood compromise between conservation and commercial interests in the UK, thejuxtaposition of annually cut and never cut reed patches appears as the onlysustainable alternative for the Mediterranean region. We further hypothesisethat an optimal mosaic design of cut/uncut reed patches could provide as high aconservation value as unmanaged reedbeds.

The impact of forest structure on near-ground temperatures during two years of contrasting temperature extremes

The thermal environment of clear-cut, partially cut, and uncut forest sites in northern Wisconsin are examined for a warm year and a cool year. Temperatures at 0.5 m above and 0.05 m below ground, as well as base 5°C heat sums are computed for each site between May and September and differences between cut and uncut sites compared for the 2 years. Differences in average and minimum air temperature and soil temperature are less than instrumental error, ε=0.3°C. Maximum air temperature differences between the clear-cut and uncut sites drop from 5.7°C in the cool year to 4.7°C in the warm year, while the difference for the partial cut drops from 3.2 to 2.7°C. The results suggest that studies of tree growth or forest development and climate change should consider the effects of forest structure on changes in daily extreme temperatures.

Organic matter chemistry and dynamics in clear-cut and unmanaged hardwood forest ecosystems

Forest harvesting alters the organic matter cycle by changing litter inputs and the decomposition regime. We hypothesized that these changes would result in differences in organic matter chemistry between clear-cut and uncut watershed ecosystems. We studied the chemistry of soil organic matter (SOM), and dissolved organic carbon (DOC) in soil solutions and stream samples in clear-cut and uncut sites at the Hubbard Brook Experimental Forest in New Hampshire using DOC fractionation techniques and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Alkyl-C (aliphatic compounds) and O-alkyl-C (carbohydrates) were the largest C fractions in soil and dissolved organic matter at Hubbard Brook. Alkyl-C ranged from 29–48% of soil C, 25–42% of soil solution C, and 22–42% of streamwater DOC. Carbohydrates comprised 32–49%, 36–43%, and 29–60% of C in soils, solutions, and streamwater, respectively. In both soils and soil solutions, the carbohydrate fraction decreased with increasing soil depth, while the aromaticity of organic matter increased with depth. There were no significant differences in the structural chemistry of SOM between clear-cut and uncut watersheds. The aromatic-C fractions in soil solutions at the clear-cut site ranged from 12–16%, approximately 40% greater than at the uncut site (8.5–11%). Thus, clear-cutting has resulted in the leaching of more highly decomposed organic matter, and depletion of more aliphatic compounds in the soluble organic pool. Because DOC fluxes are small compared to the SOM pool, large differences in soil solution chemistry do not substantially alter the overall composition of SOM. While the organic chemistry of stream DOC varied greatly among 3 sampling dates, there were no obvious clear-cutting effects. Thus, temporal variations in flowpaths and/or in-stream processes appear to be more important than disturbance in regulating the organic carbon chemistry of these streams.

Comparative soil CO 2 evolution, litter decay, and root dynamics in clearcut and uncut spruce-fir forest

An investigation was conducted in a northern spruce-fir forest to examine the impact of forest clearcutting on soil CO 2 efflux, litter decay, and root dynamics in the first year following harvesting. During a 6-month sampling period from May-November, clearcut plots released 16% more carbon dioxide than did uncut spruce-fir reference plots. Aboveground litterfall was much greater in the uncut site; however, unit decay rates for O i horizon surface litter in cut and uncut sites were similar. Thus, excess CO 2 efflux from the harvested site did not result from increased decomposition of litter and forest floor organic matter. Fine root (≤ 3 mm) biomass and necromass varied over the sampling period between cut and uncut sites, and live root biomass declined steeply over the growing season in the clearcut plots. Fine root decomposition in the O horizon of harvested plots equalled 35% of the initial standing crop of fine root biomass + necromass in the forest floor of the cut site, and accounted for about one-third of total soil CO 2 efflux from the clearcut site during the study period.

Studies of the Feasibility of Re-Creating Chalk Grassland Vegetation on Ex-Arable Land. II. Germination and Early Survivorship of Seedlings Under Different Management Regimes

1. Germination and establishment of the chalk grassland perennials Pimpinella saxifraga, Scabiosa columbaria, Plantago media and Achillea millefolium were compared in undisturbed chalk grassland, and in ex-arable land where the vegetation was either uncut, cut and maintained at a height of 3 cm, or completely cleared. 2. Virtually no germination was recorded for all four species in uncut quadrats on ex-arable land. Germination of Achillea and Plantago was highest in cleared ex-arable and that of Pimpinella highest in cut ex-arable. The ratio of germination in cleared and cut ex-arable increased as size of seed decreased between the species. Germination of the largest-seeded species, Pimpinella, was not significantly different in cut ex-arable and in laboratory conditions. 3. Differences in seedling survival were sought between the vegetation types, using concurrently recruited cohorts of seedlings of each species. The significant results were consistent for all species; overall seedling survival was highest in cut ex-arable, intermediate in cleared ex-arable and lowest in chalk grassland. Analysis of residuals revealed that the greatest differences in proportional survivorship between treatments occurred during the first 2 weeks of cohort life, regardless of the date of cohort recruitment, suggesting that vegetation type is a more potent determinant of mortality risk than climatic conditions during this early period of growth. Comparisons of residuals also demonstrated that survivorship decreased from cut ex-arable to cleared ex-arable to chalk grassland. Sites where vegetation is short may be more favourable for seedling establishment than uncut sites because of lower competition, and better than cleared sites because the short vegetation cover moderates temperature fluctuations and retains more soil moisture. 4. It is concluded from this and related studies, that sowing suitable species, and implementing a management regime which reduces, but does not remove all vegetation cover, will maximize the chances of establishing chalk grassland species on ex-arable sites. Management prescriptions which include mowing and grazing on ex-arable land will make the best use of the environmental opportunities, presented by agricultural extensification, to restore ecologically valuable communities.