Rising temperatures could increase forest ecosystem disturbance frequency and severity, transferring large amounts of live biomass to coarse woody debris (CWD) pools that emit carbon (C). The type of disturbance-created CWD influences the rate, amount, and duration of this C emission. We studied the effect of a large-scale disturbance on CWD dynamics in spruce-dominated forests of the Kenai Peninsula, Alaska, by determining CWD decomposition rate constants (k) using the chronosequence and decomposition-vectors methods and by modeling the hypothetical CWD dynamics occurring after a bark beetle outbreak versus a windthrow. Chronosequence-based k’s for mass ranged between 0.020 and 0.022 year −1 for logs and between 0.000 and 0.003 year −1 for snags. Decomposition-vectors-based k’s for log mass ranged between 0.022 and 0.045 year −1 among three decomposition phases and between 0.014 and 0.048 year −1 among five decay classes. Our analysis showed that snag-generating disturbances delayed C flux from CWD to the atmosphere, produced a smaller magnitude of C flux, and had the potential to store 10% to 66% more C in the system over time than disturbances generating logs. Thus, landscapes affected by disturbances creating snags (versus logs) may revert faster to C neutrality, suggesting forest management practices should reflect these differences.

Non-normally distributed variation in vegetation and topography can make estimates of litter fall based on simple mathematical scaling of randomly placed litter traps inaccurate. It has been shown that litter fall is directly related to aboveground net primary productivity (ANPP), which can be calculated from remote metrics (such as LiDAR returns) and/or measured at a high resolution (based on inventory plots). Extrapolating litter fall to a landscape scale with ANPP as a cross-correlate may increase the reliability of estimates. However, the differences in landscape-scale litter flux estimates due to scaling method have not been quantified. We collected litter from 16 plots on a small (96 ha) watershed in the western Cascades Range of Oregon over 2 years. We related litter fall to ANPP (R-2 = 0.65), which was calculated from 133 long term re-measurement plots on a forest currently dominated (70-80%) by Pseudotsuga menziesii and Tsuga heterophylla of approximately 50 years of age and used four methods of scaling, (1) multiplying mean measured litter fall per hectare by watershed area, (2) randomly selecting and summing variates from the probability distribution, (3) kriging field-measured litter and (4) supplementing our field measurements of litter with modeled litter based on the ANPP to litter relationship and then kriging. We found that (I) longer term averages of litter are more robust when compared to measurements and modeled estimates, and (2) the appearance of "hot spots" of elevated litter fall corresponding to undersampled areas of the complex terrain disappeared when the field measurements were supplemented with ANPP. In complex terrain, longer-term experiments supplemented with high-resolution productivity data may increase the reliability and interpretability of litter fall estimates. (C) 2013 Elsevier B.V. All rights reserved.

Coarse woody debris (CWD, comprised of snags and downed logs) is an important component of the structure and function of forest ecosystems, one which both influences the availability of fuel for wildfires and can be a result of wildfires. We studied snag persistence, and changes in mass of CWD in 10 years following a 1996 wildfire in mountain hemlock (Tsuga mertensiana (Bong.) Carriere) forest in the Cascade Range of Oregon, comparing unburned areas to areas with varying fire severity. Though mountain hemlock forest is a dominant type at high elevations in the Pacific Northwest, previous studies have not addressed the species. From studies of other conifers in western North America, we hypothesized that probability of snag persistence would be >75% 5 years and <50% 10 years after fire, and would increase with tree size. We modeled snag persistence on characteristics of the snags and the plots on which they occurred, using generalized mixed effects models. Probability of snag persistence was >75% 5 years after fire and increased with increasing tree diameter, as predicted. However, probability of persistence was >50% 10 years after fire. The cold climate, with a brief interval of optimal temperatures for decay organisms, probably contributed to prolonged snag persistence. Although probability of snag persistence remained high, estimated mass of snags declined and estimated mass of logs increased. Both breakage of snags and decreasing wood density due to advancing decay contributed to the decrease in estimated snag mass. Due to the nearly complete transformation of live trees to snags and the paucity of tree regeneration, we expect that patches of high fire severity will be effective barriers to the spread of crown fires for decades. Published by Elsevier B.V.

The degree to which carbon concentration (CC) of woody detritus varies by tree taxa, stage of decay, tissue type (i.e., bark versus wood), and vertical orientation was examined in samples of 60 tree species from the Northern Hemisphere. The mean CC of 257 study samples was 49.3% with a range of 43.4-56.8%. Angiosperms had a significantly lower CC than gymnosperms, with means of 47.8% and 50.6%, respectively. For whole-stems (i.e., wood and bark), the CC of gymnosperms significantly increased from 49.3% to 53.5% with decomposition, while angiosperms had no significant change. The CC of bark was higher than wood across all stages of decay by an average of similar to 1.0%. A similar magnitude of difference was found for standing versus downed dead wood in the later stages of decay, with the former having a higher CC than the latter. Differences between angiosperms and gymnosperms are hypothesized to be associated with initial lignin concentrations as well as subsequent decomposition by white- versus brown-rot fungal functional groups. The higher abundance of brown-rots in decomposing gymnosperms may lead to an increase in lignin concentrations, a compound that has higher CC than cellulose. As a result of these findings, uncertainties associated with forest carbon inventories may be reduced by using detrital CC specific to general taxa (angiosperms versus gymnosperms) and stage of decay rather than a single assumed value of 50% as commonly practiced. (C) 2012 Elsevier B.V. All rights reserved.

FASTH, B. G., M. E. HARMON, J. SEXTON (Department of Forest Ecosystems and Society, 321 Richardson Hall, Oregon State University, Corvallis OR, 97331), AND P. WHITE (North Carolina Botanical Garden, University of North Carolina, Chapel Hill, NC, 27599). Decomposition of fine woody debris in a deciduous forest in North Carolina. J. Torrey Bot. Soc. 138: 192-206. 2011.-We examined the effect of position with respect to the soil surface, species, and piece size on the decomposition rate of fine woody debris (< 15 cm diameter) in a North Carolina forest disturbed by hurricane. To examine year-to-year trends, pieces of two species (Carya tomentosa ((Lam.) Nutt.) and Quercus alba (Lam.)) in four size classes were placed on the forest floor and collected annually for ten years. In addition, to examine position effects samples of the same species and sizes were suspended in the air and buried underground at a depth of 20 cm and collected at years 2, 4, and 8. Nine other species were placed on the forest floor and collected at years 2, 4, and 8 to determine the range of variability among species. Decomposition was slower the first year than subsequent years, therefore the lag exponential equation was used to determine time trends and an integrated decomposition rate-constant (k(I)) reflecting the overall decomposition rate-constant was calculated. The k(I) for C. tomentosa and Q. alba ranged from 0.17-0.25 year(-1) with a significant interaction between species and size. The buried and suspended samples generally decomposed more slowly than the samples on the surface and k(I) ranged from 0.11-0.24 year(-1) and from 0.10-0.18 year(-1), respectively. There was a significant interaction between position and size; while drying limited decomposition of suspended pieces regardless of size, high moisture may have limited decomposition in the largest buried pieces. The K(I) for all eleven species and sizes averaged over all size classes ranged from 0.06-0.33 year(-1). There was a highly significant interaction between species and size with the smaller sizes tending to decompose faster than the larger sizes and in general species with the most decay-resistant heartwood having the largest response to increases in size. Our experiments and comparison to other studies suggests that the interactions between species, size, and position relative to soil surface are highly complex and dependent on site climate.

Evaluated various techniques for determining the density (i.e., bulk density) of fine woody debris during forest inventory activities. It was found that only experts in dead wood inventory may be able to identify fine woody debris stages of decay. Suggests various future research directions such as development of a 2-class fine woody debris decay class system.

Abstract Water dynamics in decaying conifer logs of four species (Abies amabilis [Pacific silver fir], Pseudotsuga menziesii [Douglas-fir], Thuja plicata [western red cedar], and Tsuga heterophylla [western hemlock]) were studied in the Coast Range of Oregon. Measurements were made of throughfall, leachate, runoff, and absorption for logs during their 6th through 8th year of decay. During this period 47–70% of the throughfall landing on the logs evaporated, 18–35% flowed through the log and leached out, 3–29% ran off the surface, and absorption accounted for 3–11%. Together absorption and evaporation intercepted 60% of the throughfall impacting the logs. Although the second year of the study had twice as much precipitation as the first, the partition of the fluxes was essentially identical. Direct measurement of the changes in log weight allowed calculation of water stores and the evaporative component; the latter proved to be the largest fraction of the water balance, with the majority of losses during the cool, wet, winter period.

ABSTRACT Regional-scale processes of tectonism, late Quaternary marine transgression, and patterns of aeolian deposition and erosion largely control the geoarchaeological character of the Oregon coast. Dramatic changes to the landscape of the Oregon coast since the Last Glacial Maximum drove the evolution of terrestrial and marine environmental processes which in turn conditioned the location and nature of prehistoric human activities. Due to the geologic complexities of Oregon's coast, archaeological investigations must address a broad range of geological factors that worked to greatly modify the ancient coastal landscape. In many ways, the modern Oregon coastline bears little resemblance to that associated with prehistoric coastal peoples prior to 3000 years ago, requiring geoscientific perspectives to reconstruct the late Quaternary environmental context. Through the integration of geologic concepts and information, geoarchaeology offers an effective means of finding early sites in the modern coastal landscape and in the now-submerged paleocoastal landscape.

This report presents a synthesis of published and unpublished data on woody detritus density as a step toward improving estimates of coarse woody detritus (CWD) and fine woody detritus (FWD) biomass across the forests of the United States. In the case of CWD, 88 species were found to have data on densities for five decay classes that had been published and/or collected in North America. For FWD, about 25 species had been sampled. We determined that by sampling representative species within a genus, the uncertainty of CWD estimates could be reduced by up to 50 percent over not having sampled a genus. Our analysis indicated that the uncertainty of FWD mass estimation ranged from 12 to 19 percent when FWD relative density was estimated.

Decomposition constants (k) for above-ground logs and stumps and sub-surface coarse roots originating from harvested old-growth forest (estimated age 400-600 y) were assessed by volume-density change methods along a 70-y chronosequence of clearcuts on the Wind River Ranger District, Washington, USA. Principal species sampled were Tsuga heterophylla and Pseudotsuga menziesii. Wood and bark tissue densities were weighted by sample fraction, adjusted for fragmentation, then regressed to determine k by tissue type for each species. After accounting for stand age, no significant differences were found between log and stump density within species, but P. menziesii decomposed more slowly (k = 0.015.y(-1)) than T. heterophylla (k = 0.036.y(-1)), a species pattern repeated both above- and below-ground. Small-diameter (1-3 cm) P. menziesii roots decomposed faster (k = 0.014-y(-1)) than large-diameter (3-8 cm) roots (k = 0.008.y(-1)), a pattern echoed by T. heterophylla roots (1-3 cm, k = 0.023.y(-1); 3-8 cm, k = 0.017.y(-1)), suggesting a relationship between diameter and k. Given our mean k and mean mass of coarse woody debris stores in each stand (determined earlier), we estimate decomposing logs, stumps, and snags are releasing back to the atmosphere between 0.3 and 0.9 Mg C.ha(-1).y(-1) (assuming all coarse woody debris is P. menziesii) or 0.8-2.3 Mg C.ha(-1).y(-1) (assuming all coarse woody debris is T. heterophylla). Including coarse roots increases these loss calculations (averages of all decomposition classes for the study year) to 0.5-1.9 Mg C.ha(-1).y(-1) or 1.0-3.5 Mg C.ha(-1).y(-1), respectively. Our results support substitution of log k in C flux models when stump k is unknown. Substitution of log k for coarse root k could, however, substantially overestimate C flux back to the atmosphere from these forests.

We examined the effects of species, initial substrate quality, and site differences (including temperature, precipitation, and soil N availability) on fine-root (<2 mm diameter) decomposition in litter bags and its N dynamics in Sitka spruce (Picea sitchensis (Bong) Carrière), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests in Oregon, U.S.A. Species significantly influenced fine-root mass loss during the first 2 years of decomposition. Over the same period, site differences had little impact on decomposition of fine roots. The percentage of initial mass remaining of decomposing fine roots fitted a single-exponential model. The decomposition rate constant (k) for all 15 species examined ranged from 0.172 year–1 for Engelmann spruce (Picea engelmanni Parry ex Engelm.) to 0.386 year–1 for Oregon ash (Fraxinus latifolia Benth.). Initial C quality indices (e.g., cellulose concentration, lignin concentration) of fine roots were correlated with fine-root decomposition rates. In contrast, initial N concentration and soil N availability were not correlated with fine-root decomposition rates. The rate of N released from decomposing roots was positively correlated with the initial N concentration of the fine roots. The data suggest that decomposing fine roots could release at least 20 kg N/ha annually in mature Douglas-fir forests of the Pacific Northwest.

A chronosequence of three species of logs (Pinus sylvestris L., Picea abies (L.) Karst, and Betula pendula Roth.) from northwestern Russia was resampled to develop a new method to estimate rates of biomass, volume, and density loss. We call this resampling of a chronosequence the decomposition-vector method, and it represents a hybrid between the chronosequence and time-series approaches. The decomposition-vector method with a 3-year resampling interval gave decomposition rates statistically similar to those of the one-time chronosequence method. This indicated that, for most cases, a negative exponential pattern of biomass, volume, and density loss occurred. In the case of biomass loss of P. sylvestris, however, polynomial regression indicated decomposition rates were initially low, then increased, and then decreased as biomass was lost. This strongly suggests three distinct phases: the first when decomposers colonized the woody detritus, a second period of rapid exponential mass loss, and a third period of slow decomposition. The consequences for this complex pattern of decomposition were explored at the ecosystem level using a simple model. We found that a single rate constant can be used if inputs vary within a factor of 10, but that this approach is problematical if inputs are more variable.

Seasonal and long-term changes in the water balance of conifer logs during the first 8 years of decomposition were studied in an old-growth Pseudotsuga/Tsuga forest in the Oregon Cascade Mountains. Measurements were made of the moisture content of outer bark, inner bark, sapwood, and heartwood and of the flow of water into and out of logs of four species (Abies amabilis, Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophylla). After the logs had decomposed from 1 to 2 years, 38–47% of the canopy throughfall landing upon them ran off the surface, 29–34% leached from the bottom, and 21–30% was absorbed and evaporated. After 8 years of decomposition, water entering and then leaching from logs increased 1.3 times while runoff decreased a similar amount. The proportion of water stored by and evaporated from logs in this study indicates that in old growth forests they may intercept 2–5% of the canopy throughfall to the forest floor and that, even in early stages of decomposition, they may affect the hydrological cycle of Pacific Northwest old-growth forests.

The decomposition rates and mass of fine ( 10-cm-diameter) woody detritus were measured in the dry tropical forests of the northeastern Yucatan Peninsula. The smallest mass of woody detritus was found in undisturbed stands: fine fractions averaged 4.7 Mg ha-' and coarse fractions ranged between 13 and 38 Mg ha-'. The largest mass of fine woody detritus (32.2 Mg ha-') was found in a hurricane-disturbed forest; whereas, the largest mass of coarse woody detritus (99.5 Mg ha-') was found in stands disturbed by catastrophic fires. A decomposition time-series study installed in 1989 indicated that decomposition rates varied greatly among species and diameters of branch segments. Over a 4-year period, the decomposition rate constant for fine woody detritus ranged from 0.151 to 1.019 year-' and that for coarse woody detritus ranged from 0.008 to 0.615 year-'. The halflife of woody detritus increased 33-fold (among pieces ranging from 1 to 30 cm in diameter) for the most decayresistant species (Manilkara zapota) but was relatively constant for the least decay-resistant species (Bursera simaruba). The wide range in decomposition rates observed in these forests indicates that the poor substrate quality of some species may override climatic (e.g., warm temperatures) and biotic (e.g., termites) factors favorable to rapid decomposition, leading to a substantial accumulation of woody detritus.

The export of mass and nutrients associated with the formation of fungal sporocarps during the first 7 years of decomposition of logs of four conifer species (Abiesamabilis Dougl. ex Forbes, Pseudotsugamenziesii (Mirb.) Franco, Thujaplicata D. Don, and Tsugaheterophylla (Raf.) Sarg.) was investigated in western Oregon. Abundance of the most common fungal species, Naematolomacapnoides (Fr.:Fr.) P. Kumm, differed significantly with log species; the fungus was most abundant on Abies and least abundant on Thuja. Fungi increased concentrations of N, K, and P over those found in associated logs by as much as 38, 115, and 136 times, respectively. Thus, a fair proportion of the initial N (0.9–2.9%), K (1.8–4.5%), and P (1.9–6.6%) was transported out of logs via sporocarps at a time when immobilization would have been predicted from critical element ratios (e.g., C/N).