Wood Accumulation Research Articles

Accumulation of dead wood in abandoned beech (Fagus sylvatica L.) forests in northwestern Germany

Currently, there is much debate about what strategy is most suitable for increasing old-growth attributes in forests that have been managed intensively for wood production in the past. Passive restoration, i.e. cessation of forestry interventions, should be considered when the old-growth attributes desired can be restored within a feasible period of time.Our study focuses on standing and lying coarse dead wood (≥20cm diameter) in beech-dominated forests in northwestern Germany. We analyzed monitoring data of 545 sample plots (sized 500–1000m2) from 12 strict forest reserves (SFRs). The SFRs had been without forestry intervention for up to 28 years.Both, number of dead objects and volume of dead wood (m3ha−1) increased significantly with ongoing time since abandonment from forestry interventions. The mean amount doubled from 9 to 18m3ha−1 within 10 years. The proportion of standing dead wood was about 40% of the total dead wood pool ≥20cm diameter.With mixed linear modeling we showed that dead wood increased by a mean net rate of about 1m3ha−1a−1. Therefore, after three decades critical values for restoring the dead wood pool could be reached. We hypothesized that the rate of dead wood input is mainly determined by disturbance driven tree mortality such as oak decline, bark beetle infestations and storms.A comparison with primeval forests or reserves abandoned more than 100 years ago showed that the SFRs studied are at the beginning of a long process of dead wood accumulation.Based on our results, the abandonment of forest activities in harvestable pure and mixed beech stands is an effective strategy for restoring the dead wood pool.

Acidification of tropical forest soils derived from serpentine and sedimentary rocks in East Kalimantan, Indonesia

Soil acidification is one of major pedogenetic processes under tropical forests, however, proton sources and weathering reactions vary from soil to soil. The dominant soil-acidifying processes, along with their spatial heterogeneity, under tropical forests were analyzed for five Indonesian soils formed from different parent materials (serpentine and sedimentary rocks). The contribution of different proton sources to soil acidification was quantified based on the theory of proton budget by measuring fluxes of solutes leaching and vegetation uptake. Excess cation accumulation in wood (3.0–8.6 kmol c ha − 1 yr − 1 ) was a dominant acidification process in all the soil profiles due to the high net primary production in this tropical region. However, the dominant proton-generating and consuming processes varied with soil horizons and parent materials. In moderately acidic soils from serpentine and mudstone, protons generated by nitrification, dissociation of carbonic and organic acids and vegetation uptake contributed to acidification of the mineral soil horizons (2.4–4.3 kmol c ha − 1 yr − 1 ), but they could completely be neutralized by basic cations. A higher acid neutralizing capacity (ANC) of these soils weakened acidity and contributed to accumulation of Al and Fe oxides through in situ weathering. In highly acidic soils from sandstone, protons generated by dissociation of organic acids and vegetation uptake in the O horizons (1.6–3.6 kmol c ha − 1 yr − 1 ) could not completely be neutralized owing to the lower ANC, which resulted in eluviation of protons, Al and Fe from the surface soil horizons. In this tropical region, parent materials influence pedogenetic acidification processes at a local scale through effects on the intensity and distribution of acids and ANC of litter and soils.

Learning from a “benign neglect strategy” in a national park: Response of saproxylic beetles to dead wood accumulation

Increasing demands for firewood owing to rising energy costs have accelerated discussions about the amount of dead wood needed for conservation. A sharp increase in dead wood caused by bark beetles in a German national park provides lessons for management of commercial and protected forests. We investigated the effects of dead wood due to bark beetle infestation as well as tree senility on abundance and richness of saproxylic species of beetles. Increasing amounts of spruce dead wood and opening of the canopy by bark beetles had positive effects on the abundance of host-generalist, conifer-specialist, and red-listed saproxylic beetles. Broadleaf specialists were positively associated with the amount of broadleaf dead wood and negatively associated with canopy openness. Gradient analysis of beetle assemblages revealed two major environmental axes: canopy openness and amount of dead wood. We found a threshold for community divergence at a canopy openness of 23% (confidence interval CI: 11–49) and at an amount of dead wood of 64 m 3 ha −1 (CI: 35–160). Critically endangered species served as indicators of dense and open forests, but only when the amount of dead wood was high. Our results suggest that, to maintain saproxylic beetle assemblages, the amount of dead wood in commercial montane forests (at present ≈15 m 3 ha −1) needs to be tripled, with a focus on broadleaf wood in dense stands and spruce wood in open stands. For large protected areas in Europe, our data suggest that bark beetle infestation and senescence without active forest management improves habitat conditions for saproxylic beetles.

Accumulation and Preservation of Dead Wood upon Burial by Bryophytes

Large amounts (389 ± 39 m3 ha−1) of preserved dead wood buried by bryophytes were found in the organic layer (OL) of overmature (146- to 204-year-old) black spruce (Picea mariana (Mill.) B.S.P.) forests in the high-boreal forest of eastern Canada. Stand-replacing wildfires consumed the organic layer and killed the previous stands, producing snags, which subsequently fell and became buried by moss, resulting in large amounts of wood buried deep in the current organic layer. As new forest stands developed, self-thinning and senescence continuously produced minor amounts of woody debris (WD) for burial, most of which was located in the upper half of the organic layer. The experimental burial of standardized sample logs at various depths in the organic layer showed that burial significantly decreased WD temperature, increased WD moisture content, and tended to decrease WD respiration rates, indicative of reduced decomposition activity. WD preservation may be initiated by a live bryophyte cover, providing thermal insulation and moisture retention, generating an environment unfavorable to decomposition. As bryophytes are a vital component of many coniferous ecosystems throughout the circumpolar boreal and mountain forests, conditions conducive to WD burial are likely widespread. Buried wood may thus be of global relevance as habitat and a large mid- to long-term carbon store.

A lack of large-diameter logs and snags characterises dead wood patterns in Irish forests

Dead wood is an important component of forest ecosystems and volumes vary depending on forest age, management intensity and productivity. This is the first large-scale study to quantify dead wood in Irish forests and to compare them to forests in other locations. We measured the volume and size distribution of logs, the density and size distribution of snags and the volume of dead wood contained in stumps in Oak ( Quercus spp.) and Ash ( Fraxinus excelsior) forests and in Sitka spruce ( Picea sitchensis) plantations throughout Ireland. We also assigned each log, snag and stump to one of three decay classes (intact, part-rotted and well-rotted). We found no significant difference in log volume between any of the forest types. The majority (>90%) of logs were less than 20 cm in diameter, and large logs (>40 cm diameter) were scarce. We found a relatively high density of snags in all forest types but, as in the case of logs, over 90% of snags were <20 cm DBH and large snags (>40 cm DBH) were rare. The volume of dead wood contained in stumps was significantly higher in plantations than in Oak or Ash forests as a result of thinning and harvesting. Most logs and snags were moderately decayed but, in plantations, most stumps were intact. Log volume and the size of logs and snags were considerably lower than in old-growth forests in other regions. These patterns may reflect historical use of Irish forests for coppice and timber production. Management for biodiversity should aim to accelerate dead wood accumulation to increase the frequency of large-diameter logs and snags. Although management seeking to replicate the dead wood volumes of old-growth forests is ideal, it may be unrealistic in the short term.

Harvesting alternatives, accumulation and procurement cost of small-diameter thinning wood for fuel in Central Finland

This study compared harvesting alternatives, accumulation and procurement costs of small-diameter thinning wood chips for fuel, when trees were harvested either as delimbed stemwood or whole trees. The calculation was made for a hypothetical plant located in Central Finland and the radius of the procurement area was 100 km via the existing road network. Cutting was done with conventional harvester head equipped with multi-tree-handling (MTH) accessories, with the logged trees being chipped at the roadside storage. The cost of delimbed stemwood chips at heating plant was 24% higher compared to the cost of whole tree chips. The availability analysis attested that delimbing lowered the regional cutting removal by 42% compared to the whole tree harvesting, when the minimum accumulation for the fuel fraction at the stand was set at 25 m/ha. Delimbing diminishes the recovery rate at the site, resulting in a diminishing number of potential recovery sites meeting the threshold volume. However, the study showed that the forest energy potential is increased and procurement costs are reduced, if delimbed stemwood is harvested from stands where the whole tree harvesting is not acceptable due to nutrient loss or for other ecological reasons. Intelligent selection of cutting methods for different stands enables minimization of transport distance and control of procurement cost.3

Foliar characteristics, cambial activity and wood formation in Azadirachta indica A. Juss. as affected by coal–smoke pollution

This study, aimed at elucidating changes in the foliar and cambial behavior in Azadirachta indica (Neem tree) due to coal-smoke pollution, has revealed inhibitory effects of pollution stress on leaf pigments concentrations, nitrate reductase activity and the contents of reducing sugars and total N content, whereas stimulatory effects were given on stomatal index and nitrate and sulphur contents. Under smoke effects, stomatal conductance was low, leading to a drop in the net photosynthetic rate and a rise in the internal CO 2 concentration of leaf. Cambial reactivation in the stem was delayed at the polluted site. Although the total span of the cambial activity was reduced, greater amount of wood was observed to accumulate in the stem axis under heavy pollution stress. Vessel proportion in the wood increased, whereas size of vessel elements and xylem fibers decreased. “Vulnerability factor” (ratio between mean vessel diameter and mean vessel abundance) and “mesomorphic ratio” (multiplication product of vulnerability factor and mean length of vessel element) of the stem–wood, both declined with increase in the pollution stress, thus indicating a tendency of the species for shifting towards xeromorphy when grown under stress. Given the opposite trends of photosynthetic rate and wood increment, the carbon-partitioning pattern rather than the photosynthetic rate seems to have influenced the accumulation of new wood. The Neem tree proves to be suitable for growing in the polluted areas.

A patch perspective on summer habitat use by brown trout Salmo trutta in a high plains stream in Wyoming, USA

Abstract – We quantified the use of habitat patches by brown trout, Salmo trutta, during summer conditions in a plains stream in the western United States. A Global Positioning System was used to map discrete habitat patches (2–420 m2) consisting of macrophytes, wood accumulation, or deep water. Habitat use by brown trout was monitored by radio telemetry. Brown trout used habitat in a nonrandom manner with 99% of all daytime observations and 91% of all nighttime observations occurring in patches that consisted of combinations of deep water, wood accumulations or macrophytes even though such patches constituted only 9.8% of the available habitat. Brown trout used deep water almost exclusively during the day but broadened their habitat use at night. Most fish stayed within a large plunge pool created by a low‐head dam. This pool supplemented the deep‐water habitat that was naturally rare in our study area and illustrates how human modifications can sometimes create habitat patches important for stream fishes.

Effects of increased forest productivity and warmer climates on carbon sequestration, run-off water quality and accumulation of dead wood in a boreal landscape: A modelling study

Forest productivity is expected to increase in the future owing to the use of genetically improved plant material and climate warming. Increased productivity will lead to shorter optimum rotation lengths and larger annual clear-cut areas. This study explored the likely effects of increased forest production and a warmer climate in 15 scenarios (five productivity levels and three climate conditions) on: (1) wood production, (2) carbon sequestration, (3) water quality, and (4) amounts of coarse woody debris (CWD). The effects were simulated using a set of ecosystem models incorporating the same climate and management scenarios in a hypothetical managed boreal forest landscape. Under the assumption that increased productivity is coupled to a proportional decrease in rotation length, the outputs at the landscape-level scale were briefly as follows. In each simulated climate scenario, increased productivity resulted in increases in above- and below-ground carbon sequestration, and reduced CWD accumulation, but did not have significant effects on dissolved total nitrogen (DTN) loads in run-off water. In addition, at every simulated productivity level, a warmer climate led to reductions in carbon sequestration below ground and amounts of CWD, but increases in DTN contents in run-off water. Reasons for these trends are identified and explained.

Response of secondary production by macroinvertebrates to large wood addition in three Michigan streams

Summary1. We measured responses in macroinvertebrate secondary production after large wood additions to three forested headwater streams in the Upper Peninsula of Michigan. These streams had fine‐grained sediments and low retention capacity due to low amounts of in‐channel wood from a legacy of past logging. We predicted that wood addition would increase macroinvertebrate secondary production by increasing exposed coarse substrate and retention of organic matter.2. Large wood (25 logs) was added haphazardly to a 100‐m reach in each stream, and a 100‐m upstream reach served as control; each reach was sampled monthly, 1 year before and 2 years after wood addition (i.e. BACI design). Macroinvertebrate secondary production was measured 1 year after wood addition in two habitat types: inorganic sediments of the main channel and debris accumulations of leaf litter and small wood.3. Overall macroinvertebrate production did not change significantly because each stream responded differently to wood addition. Production increased by 22% in the main‐channel of one stream, and showed insignificant changes in the other two streams compared to values before wood addition. Changes in main‐channel macroinvertebrate production were related to small changes in substrate composition, which probably affected habitat and periphyton abundance. Macroinvertebrate production was much greater in debris accumulations than in the main‐channel, indicating the potential for increased retention of leaf litter to increase overall macroinvertebrate production, especially in autumn.4. Surrounding land use, substrate composition, temperature and method of log placement are variables that interact to influence the response of stream biota to wood additions. In most studies, wood additions occur in altered catchments, are rarely monitored, and secondary production is not a common metric. Our results suggest that the time required for measurable changes in geomorphology, organic matter retention, or invertebrate production is likely to take years to achieve, so monitoring should span more than 5 years, and ecosystem metrics, such as macroinvertebrate secondary production, should be incorporated into restoration monitoring programs.

Dynamics of wood recruitment in streams of the northeastern US

Wood is an important component of forested stream ecosystems, and stream restoration efforts often incorporate large wood. In most cases, however, stream restoration projects are implemented without information regarding the amount of wood that historically occurred or the natural rates of wood recruitment. This study uses a space-for-time analysis to quantify large wood loading to 28 streams in the northeastern US with a range of in-stream and riparian forest characteristics. We document the current volume and frequency of occurrence of large wood in streams with riparian forests varying in their stage of stand development as well as stream size and gradient. Linear models relating stream wood characteristics to stream geomorphic and forest characteristics were compared using Akaike's Information Criterion (AIC) model selection. The AIC analysis indicated that the volume and frequency of large wood and wood accumulations (wood jams) in streams was most closely associated with the age of the dominant canopy trees in the riparian forest (best models: log10(large wood volume (m3100m−1))=(0.0036×stand age)−0.2281, p<0.001, r2=0.80; and large wood frequency (number per 100m)=(0.1326×stand age)+7.3952, p<001, r2=0.63). Bankfull width was an important factor accounting for wood volume per unit area (m3ha−1) but not the volume of wood per length of stream (100m−1). The empirical models developed in this study were unsuccessful in predicting wood loading in other regions, most likely due to difference in forest characteristics and the legacy of forest disturbance. However, these models may be applicable in other streams in the northeastern US or in streams with comparable riparian forests, underlying geology, and disturbance regimes—factors that could alter long-term wood loading dynamics. Our results highlight the importance of understanding region-specific processes when planning stream restoration and stream management projects.

Linking upstream channel instability to downstream degradation: Grenada Lake and the Skuna and Yalobusha River Basins, Mississippi

AbstractUnstable fluvial systems are characterized by actively migrating knickpoints, incising channel beds, failing banks, and recruitment of large woody debris and it would appear that river corridors downstream of these processes would be adversely affected or impaired because of higher fluxes of sediment and other riverine products. In north‐central Mississippi, the Yalobusha River is one such system and the characteristics of two downstream locations are examined to explore this geomorphic linkage between upstream instability and downstream degradation. For the large woody debris plug along the Yalobusha River, it is found that (1) the deposit is composed mostly of sand covered with a veneer of silt and clay, (2) agrichemicals and enriched concentrations of elements are prevalent, and (3) excessive sedimentation and wood accumulation have forced river flow entirely out‐of‐bank. For Grenada Lake, it is found that (1) the impounded sediment is predominantly clay, (2) agrichemicals and elements observed throughout the reservoir show no spatial variation, (3) little difference exists in the amount and quality between the sediments deposited in Skuna and Yalobusha River arms, and (4) only a small fraction of the reservoir's storage capacity has been lost because of sedimentation. While excessive sedimentation and large woody debris recruitment have had a marked affect on stream corridor function in the area of the debris plug, the high sediment loads associated with the unstable portions of the Yalobusha River and their associated products have not been communicated to Grenada Lake. The fish consumption advisories within Grenada Lake and its tributaries due to bioaccumulated trace elements and agrichemicals, appear to be independent of the pervasive river channel instability occurring upstream. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Stand characteristics and downed woody debris accumulations associated with a mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in Colorado

Lodgepole pine (Pinus contorta Dougl. ex Loud.)-dominated ecosystems in north-central Colorado are undergoing rapid and drastic changes associated with overstory tree mortality from a current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak. To characterize stand characteristics and downed woody debris loads during the first 7 years of the outbreak, 221 plots (0.02ha) were randomly established in infested and uninfested stands distributed across the Arapaho National Forest, Colorado. Mountain pine beetle initially attacked stands with higher lodgepole pine basal area, and lower density and basal area of Engelmann spruce (Picea engelmannii [Parry]), and subalpine fir (Abies lasiocarpa (Hook.) Nutt. var. lasiocarpa) compared to uninfested plots. Mountain pine beetle-affected stands had reduced total and lodgepole pine stocking and quadratic mean diameter. The density and basal area of live overstory lodgepole declined by 62% and 71% in infested plots, respectively. The mean diameter of live lodgepole pine was 53% lower than pre-outbreak in infested plots. Downed woody debris loads did not differ between uninfested plots and plots currently infested at the time of sampling to 3 or 4–7 years after initial infestation, but the projected downed coarse wood accumulations when 80% of the mountain pine beetle-killed trees fall indicated a fourfold increase. Depth of the litter layer and maximum height of grass and herbaceous vegetation were greater 4–7 years after initial infestation compared to uninfested plots, though understory plant percent cover was not different. Seedling and sapling density of all species combined was higher in uninfested plots but there was no difference between infested and uninfested plots for lodgepole pine alone. For trees ≥2.5cm in diameter at breast height, the density of live lodgepole pine trees in mountain pine beetle-affected stands was higher than Engelmann spruce, subalpine fir, and aspen, (Populus tremuloides Michx.), in diameter classes comprised of trees from 2.5cm to 30cm in diameter, suggesting that lodgepole pine will remain as a dominant overstory tree after the bark beetle outbreak.

The demography of coarse wood in north temperate lakes

Summary1. Exchange of material across habitat boundaries is a key process in riparian zones. The movement of coarse wood from lakeshore forests to the littoral zone, where it provides habitat for aquatic organisms, is not well understood. In 2003, we resampled coarse wood within the littoral zone of four lakes in Northern Wisconsin (U.S.A.), that had originally been surveyed in 1996, to quantify the spatial arrangement of littoral coarse wood and estimate input, loss and movement rates.2. All four lakes had a clumped pattern of littoral coarse wood, and the locations of clusters were similar in both census years. Littoral coarse wood was more abundant than expected on moderate to steep slopes, on southern shorelines, and in areas with sparse residential development.3. All four lakes had a net accumulation of coarse wood; rates of wood input ranged from 0.5 to 1.9 logs km−1 year−1, i.e. there was more wood in 2003 than 1996. Movement rates of tagged logs varied 14‐fold among lakes, with a maximum in one lake of 42% of logs recovered in 2003 more than 20 m from their 1996 location. Median distance moved ranged from 22 to 323 m among the four lakes.4. Areas of persistently high wood density may be keystone habitats whose presence enables the persistence of populations of certain aquatic organisms. Conservation of locations with high wood density may be important to maintain target densities of coarse wood of lakes with human development.

When nature takes over from man: Dead wood accumulation in previously managed oak and beech woodlands in North-western and Central Europe

The accumulation of dead wood and its characteristics are analysed in forests that have been withdrawn from regular silvicultural management and left unmanaged between 10 and 150 years ago. These forests are dominated by beech ( Fagus sylvatica) and oak ( Quercus robur and Quercus petraea) and located in the lowlands of North-western and Central Europe. The total volumes of dead wood ranged from 6 to nearly 500 m 3 ha −1, with a median value of 53 m 3 ha −1. The average accumulation rate ranged from <0.1 to 19 m 3 ha −1 year −1. Variation was significantly higher in beech- than in oak-dominated forests. The variables and factors influencing dead wood volumes and accumulation rates were tree genus, stand age at the time of the onset of non-intervention, and the interaction between geographical location and tree genus. In beech-dominated stands, the ratio of lying to total dead wood was more or less constant at 75%; in oak-dominated stands, this ratio was related to the length of time non-intervention had occurred, rising from <50% in recently assigned areas to 75% in the long-established sites. It is concluded that in the absence of major disturbances, dead wood accumulation in man-made forests left to develop freely is a slow process. It may take a very long time to achieve the average amount and dynamic steady state of dead wood as described for virgin forests in Central Europe.

Controls on sulfur content in tree rings of Norway spruce and European beech at a heavily polluted site

Search for a biogeochemical archive of past sulfur pollution is motivated by the need to predict ecosystem health. Sofar, no indicator of local-scale S pollution has existed, while long-range transport of S can already be studied using polar ice records. One archive of S pollution in temperate climate zones could be annual growth rings of trees. However, S concentration patterns in tree rings of most species have been unknown because of negligible S accumulation in wood. We modified a wet chemistry procedure to increase the recovery of S from tree rings, and report time series of S concentrations in six trees from an acidified, spruce die-back affected area of Central Europe. Beech tree rings, despite 4 times lower atmospheric S inputs, exhibited twice higher S concentration in wood than spruce. The period of peak industrial S pollution of the 1980s did not result in enhanced S accumulation in tree rings of either species. Physiological processes rather than S abundance in the ecosystem regulate S storage in tree rings.

Pool Spacing, Channel Morphology, and the Restoration of Tidal Forested Wetlands of the Columbia River, U.S.A.

Abstract Tidal forested wetlands have sustained substantial areal losses associated with human land use, and restoration practitioners lack descriptions of ecosystem structures within these systems, in which surface water is a significant controlling factor on flora and fauna. In particular, the roles of large wood in tidal areas remain poorly described compared to terrestrial and riverine ecosystems. This study documents the role of large wood accumulations in forcing channel morphology in remnant Sitka spruce (Picea sitchensis)–dominated tidal freshwater wetlands (swamps) in the floodplain of the Columbia River, U.S.A., near the Pacific coast. The average pool spacing documented in channel surveys of three swamps near Grays Bay, 2.2–2.8 channel widths per pool, was not significantly different. There were higher numbers of pools on these tidal forested wetland channels (median 2.7 pools/100 m) than on a nearby diked agricultural site prior to restoration. Log jams were common in the swamps and nonexistent in the pasturelands prior to restoration. On the basis of pool spacing and observed sequences of log jams and pools, tidal forested wetland channels were classified consistent with a forced step‐pool channel type. This new classification for tidal systems provides a basis for restoration project design involving placement of large wood and development of pool habitats for aquatic species. Modifications by beaver (Castor canadensis) observed on restoration and reference sites warrant further investigation to explore the interactions between these animals and restoration methods that affect channel structure and hydraulics in tidal forced step‐pool channels.

Quantification of proton budgets in soils of cropland and adjacent forest in Thailand and Indonesia

Continuous cultivation has the potential to accelerate soil acidification. The influence of cultivation on soil acidification was evaluated by calculating proton budget in a soil–vegetation system including solute leaching, vegetation uptake and organic matter decomposition in cropland and adjacent forest in Thailand and Indonesia. In the forests, excess cation accumulation in wood (2.1–3.8 kmolc ha−1 year−1) has contributed to soil acidification at the rate of 0.004 molc for production of 1 mol carbon. In the croplands, soil organic matter loss (2.2–3.9 Mg C ha−1 year−1) has contributed to both proton generation owing to nitrification (1.5–5.0 kmolc ha−1 year−1) and proton consumption owing to mineralization of organic anions (3.6–8.8 kmolc ha−1 year−1) at the rates of 0.008–0.015 and 0.019–0.026 molc for the loss of 1 mol soil organic carbon, respectively. Although the influence of cultivation on proton budget is different depending on the budget of organic matter and soil types (soil pH and texture), cultivation results in soil organic matter loss and soil alkalinization at least during the initial stage of cultivation in tropical regions.

Changes in quantitative patterns of dead wood in maritime pine plantations over time

Although the volume of dead wood is commonly acknowledged as an indicator of biodiversity in sustainable forest management schemes, only few data are available for plantation forests. To evaluate the volume and qualify the diversity of woody debris along a chronosequence of maritime pine plantations, we sampled downed woody debris, snags and stumps in 143 stands of different ages. To test the hypothesis that the pattern of dead wood accumulation mainly results from silvicultural operations, we developed a predictive model. It combined an empirical growth model evaluating the amount of dead wood produced by successive thinnings with a decay function that estimated the loss of dead wood with time. The volume of dead wood averaged 15 m 3/ha. Downed woody debris, stumps and snags represented 81%, 11% and 8% of this volume, respectively. Pieces of downed woody debris were equally distributed between fine and coarse woody debris however large pieces (diameter ≥20 cm) were scarce. The dead wood was mainly from anthropogenic origin (77%) and its volume significantly increased with stand productivity. The pattern of dead wood accumulation along the forestry cycle showed a convex shape with a peak in stands of ca. 30-year-old, after the third thinning. The dynamics was successfully predicted for downed woody debris ( r = 0.47, P < 0.001) and for stumps ( r = 0.45, P < 0.001) by the model combining inputs from thinnings and loss with time. This model may help to predict the effect of alternative forestry practices on dead wood accumulation by forest managers or nature conservationists in similar pine forest plantations.

Dynamics of large wood in an eastern U.S. mountain stream

Large wood (LW) is an important feature in many streams in northeastern North America, yet the dynamics (recruitment, movement, and export) of large wood remain largely undocumented for streams in this region. In this study we quantify the dynamics of LW in 400 m of a second-order, high gradient, boulder-dominated stream in the eastern Adirondack Mountains, NY. Characteristics and location of all LW (>1-m length, >10-cm diameter) in the 400-m study reach were initially recorded and pieces were individually tagged in November 2000. Subsequent surveys were conducted in late summer/fall of 2001, 2003, and 2004. Twenty-six% of the 112 pieces of LW initially tagged moved 5.0 m or more during the 4 years of this study. Mobile wood was, on average, shorter than non-mobile wood. Nearly all mobile wood was shorter than the 8.0-m bankfull width of the stream. From 2000 to 2004, 2.16 m 3 (0.54 m 3 100 m −1; 43 pieces) of LW entered the study reach and 0.7 m 3 (0.18 m 3 100 m −1; 13 pieces) left the stream. Retention of wood in debris dams was key to reducing potential export. For this stream, located within a second-growth mixed northern hardwood riparian forest that is approaching maturity, the net wood accumulation rate was estimated as ranging from 0.09 to 0.15 m 3 100 m −1 year −1. Our data support previous observations that LW length strongly influences its potential to move in high gradient streams, though debris dams can reduce LW movement rates and movement distances for wood of all sizes.