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Much remains unknown regarding the linkages between forest structure and microclimate as they regulate detrital decomposition. In this study, we use a factorial field experiment that included canopy gap creation and downed woody material (DW) additions conducted in a mature northern hardwood forest. Our objectives were to (1) test the individual and combined effects of canopy gaps and DW additions on detrital mass loss; (2) determine whether the factors regulating mass loss are similar among leaf litter, experimental wood stakes, and coarse DW; and (3) assess the microclimatic variables that most strongly influence mass loss of these detrital types. After three years, leaf litter mass loss within gaps, without or with DW additions, was significantly greater than that of any non-gap treatments. Mass loss of stakes was significantly greater in gaps, intermediate in gaps with DW additions, and lowest in non-gap treatments. Mass loss of wood stakes after 8 years varied by species, with aspen (Populus tremuloides) losing up to 93% and sugar maple (Acer saccharum) up to 82% of its original mass. Fourteen years following treatment, the experimental logs lost 55–70% of their original mass, with ash (Fraxinus spp.) decaying faster than maple. Gap creation and DW additions individually, but not in combination, increased mass loss of coarse DW. For most substrates tested, gaps were consistently and positively related to mass loss, with approximately 10% greater mass loss in gaps compared to non-gaps. The presence of deadwood strongly moderated litter decomposition, had minimal effect on small woody substrates in the short-term after gap creation, but was influential on longer-term decay patterns of larger DW. Predictive models for each substrate varied, though shared some similar drivers. Litter mass loss was positively correlated to increasing gap size, canopy openness, and soil moisture. Stake mass loss was positively correlated to increasing gap size and canopy openness for maple, but soil temperature for aspen. Mass loss for logs was driven by increasing DW volume and gap size for ash, but soil temperature for maple. Smaller-sized materials may be more sensitive to environmental conditions as opposed to logs for which microclimatic influence may lag or remain a minor driver for at least the initial decade of decomposition. Regardless of substrate type, the findings of this work highlight the potential for greater rates of detrital mass loss from forest systems under predicted increases in canopy disturbance rates with climate change and invasive insects and diseases. [ABSTRACT FROM AUTHOR]

Downed woody debris (DWD) creates heterogeneous microsites that are beneficial to enhancing biodiversity and that represent persistent nutrient and carbon pools. Windthrow events characteristic of northern deciduous forests naturally produce abundant DWD and canopy openings that enhance structural complexity, but group selection harvesting reduces DWD biomass despite promoting vertical structural complexity. We implemented a field experiment to test the response of the soil microbial community (SMC) to DWD addition in created gap openings to compare experimental windfall to group selection harvest. Our objective was to assess the variability among microbial functional groups within canopy openings versus at the stand scale with DWD addition four- and five-year posttreatment. This study builds on previous studies at the Flambeau Experimental Research Site (Wisconsin, USA) that tested the effects of canopy openings alone on the SMC abundance and soil respiration along the gap gradient. Soils were sampled in four treatments (gaps, gaps + DWD addition, control + DWD addition and a control), and SMC abundance and composition were quantified using a modified phospholipid fatty acid (PLFA) and fatty acid methyl ester (FAME) method. Our analyses indicated a stronger response of the SMC to within-gap microenvironments than to the stand-level interaction of DWD addition and canopy openings. We found significant variation in the SMC along the north–south transect within the gaps, with higher abundance of arbuscular mycorrhizal fungi, soil temperature, unsaturation bacterial stress ratio and lower bacterial abundance in the northern portion of the canopy openings. DWD addition within gaps buffered the soil from extreme temperature changes while increasing gram-positive bacteria abundance that tend to rely on recalcitrant carbon sources and are more resistant to environmental stress. These patterns indicate that gap openings and DWD addition increased soil microenvironmental spatial heterogeneity and suggest that structural complexity may contribute to carbon storage by promoting sequestration in regenerating vegetation and by shaping the SMC to favor greater C use efficiency. [ABSTRACT FROM AUTHOR]

Deadwood may alter the chemical and microbial properties of forest soils. However, it is unclear how downed deadwood (logs) of different tree species affect nutrients, microbial activity and biomass in different forest soils and regions. We investigated the effect of logs on underlying soils after 8 years of decomposition in an experiment consisting of 13 log tree species replicated at 30 forest sites across three German regions with distinct climate and geology. Soils beneath logs were compared to soils without recognizable influence of deadwood (control) 8 m away. Carbon, nitrogen, phosphorous and calcium concentrations increased by 5–18% in the soils under logs, whereas soil potassium, magnesium, iron, manganese and aluminum were not or slightly negatively affected by logs. Soils beneath logs exhibited 33%, 18% and 54% higher carbon mineralization, microbial biomass and ergosterol (component of fungal cell membranes) contents, respectively. Despite major differences in decay rates, the effect on soil properties hardly differed among the 13 log tree species. The effect of logs on microbial and chemical soil parameters increased with decreasing concentration of carbon, nitrogen, phosphorous and pH in the prevailing forest soils. Consequently, the strongest effects of logs on soil parameters occurred in plots with low soil nutrient contents and low soil pH. Our results suggest that logs of all tree species primarily increase the microbial activity and nutrient contents of acidic and nutrient-poor soils. [ABSTRACT FROM AUTHOR]

Natural forests contain a large amount of deadwood, which is a key contributor to biodiversity, especially by providing dynamic habitats and resources for a huge variety of invertebrates. However, for managing forest biodiversity we need to better understand what drives the dynamics of invertebrate communities in deadwood. We hypothesized that the invertebrate communities in logs will converge from initial to middle decomposition stage among tree species and forest stands as the differentiating role of bark diminishes and xylem traits converge during decay. We investigated invertebrate communities in decomposing logs of ten tree species over 4 years in the "tree cemetery" LOGLIFE experiment in two contrasting forests in the Netherlands. The predominant faunal groups studied were Annelida (earthworms), Isopoda (woodlice), Chilopoda (centipedes), Diplopoda (millipedes), Diptera (flies, midges) and Coleoptera (beetles). We demonstrated that (1) tree species, decay stages and incubation forests all had effects on the invertebrate communities; (2) community compositions of fauna in logs first were very dissimilar and then became more similar among tree species through the decay years; and (3) this converging pattern of faunal community dynamics also manifested itself, both across and within given tree species, between two contrasting forests over decomposition time. Thus, invertebrate communities generally converged during deadwood decay, which adds fundamental insights into the role of interacting drivers of community succession. These findings also highlight that, both within and among forests, more functionally different tree species and logs in different decay stages, will support relatively high biodiversity of invertebrate communities; these patterns may inform forest management strategies aimed at maximizing biodiversity. [ABSTRACT FROM AUTHOR]

Decomposition, vegetation regeneration, and biological control are essential ecosystem functions, and animals are involved in the underlying processes, such as dung removal, seed removal, herbivory, and predation. Despite evidence for declines of animal diversity and abundance due to climate change and land-use intensification, we poorly understand how animal-mediated processes respond to these global change drivers. We experimentally measured rates of four ecosystem processes in 134 grassland and 149 forest plots in Germany and tested their response to climatic conditions and land-use intensity, that is, grazing, mowing, and fertilization in grasslands and the proportion of harvested wood, non-natural trees, and deadwood origin in forests. For both climate and land use, we distinguished between short-term effects during the survey period and medium-term effects during the preceding years. Forests had significantly higher process rates than grasslands. In grasslands, the climatic effects on the process rates were similar or stronger than land-use effects, except for predation; land-use intensity negatively affected several process rates. In forests, the land-use effects were more pronounced than the climatic effects on all processes except for predation. The proportion of non-natural trees had the greatest impact on the process rates in forests. The proportion of harvested wood had negative effects, whereas the proportion of anthropogenic deadwood had positive effects on some processes. The effects of climatic conditions and land-use intensity on process rates mirror climatic and habitat effects on animal abundance, activity, and resource quality. Our study demonstrates that land-use changes and interventions affecting climatic conditions will have substantial impacts on animal-mediated ecosystem processes. [ABSTRACT FROM AUTHOR]

Woody debris decay rates have recently received much attention because of the need to quantify temporal changes in forest carbon stocks. Published decay rates, available for many species, are commonly used to characterize deadwood biomass and carbon depletion. However, decay rates are often derived from reductions in wood density through time, which when used to model biomass and carbon depletion are known to underestimate rate loss because they fail to account for volume reduction (changes in log shape) as decay progresses. We present a method for estimating changes in log volume through time and illustrate the method using a chronosequence approach. The method is based on the observation, confirmed herein, that decaying logs have a collapse ratio (cross-sectional height/width) that can serve as a surrogate for the volume remaining. Combining the resulting volume loss with concurrent changes in wood density from the same logs then allowed us to quantify biomass and carbon depletion for three study species. Results show that volume, density, and biomass follow distinct depletion curves during decomposition. Volume showed an initial lag period (log dimensions remained unchanged), even while wood density was being reduced. However, once volume depletion began, biomass loss (the product of density and volume depletion) occurred much more rapidly than density alone. At the temporal limit of our data, the proportion of the biomass remaining was roughly half that of the density remaining. Accounting for log volume depletion, as demonstrated in this study, provides a comprehensive characterization of deadwood decomposition, thereby improving biomass-loss and carbon-accounting models. [ABSTRACT FROM AUTHOR]

Deadwood is an important component for conserving carbon stock and maintaining species diversity. Scarce information is, at present, available concerning the amount and composition of deadwood in Mediterranean-type ecosystems. In this study, 21 sites were chosen to characterize different forest types among representative managed and unmanaged stands in the Central Apennines (Molise, Italy). Data were collected to assess living tree and deadwood volumes, and the relative abundance of different deadwood components in decay classes. The information gathered was related to human-induced disturbances on a regional scale. There were substantial differences in the deadwood volumes between managed and unmanaged stands, although this was not the case in the living tree volumes. Deadwood volumes were larger in unmanaged than in managed stands. In particular, large amounts of deadwood were found in managed Mediterranean and Anatolian fir forests, probably due to minimal management practices. Dead downed trees were less represented in managed forests as they are normally removed to facilitate logging activities. Logs occurred more frequently in managed stands as logging residues left on site. Most deadwood material belonged to early decay classes. Proportionally larger amounts of deadwood ascribed to class 1 in managed stands correlated with recent cutting activities. The relatively large amounts of deadwood attributed in unmanaged stands to class 3 demonstrate its longer persistence in unmanaged forests. This study represents a first systematic analysis of deadwood occurrence in a typical Mediterranean forest area, and should be useful in defining important objectives for sustainable forest management. [ABSTRACT FROM AUTHOR]