•Uneven-aged, mixed-species forest stands promote total insect abundance.•Total insect abundance in forests is positively related to multi-layered vegetation.•Non-herbivorous taxa are further related ...to understorey vegetation structure.•Terrestrial laser scanning provides structure indices relevant for insects.
Retention forestry intends to promote biodiversity by retaining deadwood and tree-related microhabitats. Simultaneously, production forests undergo major structural changes by conversion into near-natural forests. As insect biomass is declining, it is important to understand how insect communities respond to management-related changes in forest structure. While some structural elements, such as deadwood, are studied extensively, three-dimensional forest structure is often neglected. Terrestrial laser scanning offers new approaches to quantify three-dimensional structure but their suitability has not been evaluated with field-based insect surveys.
To test how insect communities respond to forest structure, we examined insects from window traps from 122 sites in the Black Forest. For total insect abundance and for the seven most abundant taxa, we related deadwood, microhabitats, various conventional stand properties and novel remote sensing-based indices for vegetation structure to total and taxon-specific abundances. Additionally, we assessed the influences of these structural elements on community composition.
Total insect abundance and abundances of most taxa were positively related to multi-layered stands, as derived from remote sensing techniques. Furthermore, each taxon responded to some additional forest structural elements. Higher tree diameter, canopy gap fraction and share of deciduous trees increase abundances of the predominantly herbivorous taxa Heteroptera, Sternorrhyncha and Auchenorrhyncha. Community composition was influenced by mean tree diameter and share of deciduous trees. Neither tree-related microhabitats nor deadwood diversity had a detectable effect on insect abundance.
We conclude that more elements of forest structure than previously acknowledged are related to insect populations. In particular, multi-layered forest stands have higher insect abundances in the midstorey. The current conversion in continuous-cover forestry in Europe from even-aged, often conifer-dominated forests to uneven-aged, mixed species stands can therefore increase the abundance of a wide range of insect taxa and is possibly one strategy to halt insect decline in forests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•We detected individual pieces of coarse woody debris using airborne LiDAR.•Large pieces of coarse woody debris were most likely to be detected.•Site characteristics and stand type did not influence ...coarse woody debris detection.•LiDAR pulse density influenced detection of coarse woody debris.•LiDAR is a promising tool to detect and map coarse woody debris.
Coarse woody debris (CWD) is an essential component of forest ecosystems that provides habitat for diverse species, functions in water and nutrient cycling, and can be a potential surface fuel in wildfires. CWD detection and mapping would enhance forestry and wildlife research and management but passive remote sensing technologies cannot provide information on features beneath forest canopy, while field-based CWD inventories are not practical for mapping CWD over large areas. Airborne light detecting and ranging (LiDAR) is a remote sensing technology that provides detailed information on three-dimensional vegetation structure that could overcome limitations of passive remote sensing technologies and field-based inventories. Our objectives were to evaluate whether airborne LiDAR could be used to detect individual pieces of CWD. We measured 1679 pieces of CWD at 144 field plots from 2015 to 2016. We acquired high-density (∼24 first returns/m2) LiDAR data in 2014, filtered out canopy and sub-canopy returns using a height threshold based on field measurements of CWD, and used height-filtered data to determine which field-measured pieces of CWD were visible in the resulting point cloud. CWD pieces that were detected constituted 50% of plot CWD volume, and there was a strong, positive correlation between total plot CWD volume and volume of detected pieces (r = 0.96). Overall, we detected 23% of the individual pieces of CWD we measured. Large pieces of CWD were most likely to be detected, with the majority of pieces ≥30 cm diameter or ≥13.9 m long detected. Canopy density, shrub density, and forest type did not influence detection probability. CWD detection rates increased from 1 pulses/m2 to 16 pulses/m2, and CWD detection rate was constant from 16 pulses/m2 to 24 pulses/m2. Our results demonstrate that airborne LiDAR can be used to detect CWD. LiDAR-based detection and mapping of CWD will be most useful for applications that focus on larger and longer pieces of CWD or applications focused on total CWD volume.
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•Wood-inhabiting fungal diversity depends on habitat quantity, quality, and continuity.•Volume of lying deadwood and low snags affected the total species richness.•Red-listed species responded to ...continuity, i.e., the number of >250-years-old trees.•Forests with uninterrupted continuity should be prioritised for conservation.•Retention practices should be considered from a centuries-long time perspective.
An ongoing loss of Europe's old-growth forests urgently calls for improving our understanding of native biodiversity response to habitat changes. Studies disentangling the effects of habitat quantity, quality, and continuity on species diversity are rare, however, understanding the differences between these effects is crucial for forest management and conservation efforts. Here, we investigated the influence of habitat quantity, quality, and continuity on the total and red-listed species richness of wood-inhabiting fungi in old-growth mountain Norway spruce (Picea abies Karst.) forest in Central Europe. The fruitbody-based mycological survey conducted on permanent plots was combined with the measurements of forest structural characteristics such as deadwood volumes (indicating habitat quantity), dimensions, and decay stages (indicating habitat quality). Additionally, precise dendrochronological measurements were used to estimate the mean age of five oldest trees and the number of >250 years-old-trees (i.e., those that survived a probable logging activity about 250 years ago) as indicators of habitat continuity. Our results showed the total species richness of wood-inhabiting fungi to be best correlated with habitat quantity (volume of low snags and lying deadwood), while the red-listed species richness was best explained by habitat continuity indicated by the number of >250 years-old-trees. Our study provides novel evidence regarding uninterrupted habitat continuity being crucial in supporting red-listed fungal species. Stands with preserved habitat continuity (e.g., the absence of clearcutting and deforestation) as well as old-growth stands with long habitat history should be prioritised for conservation. Greater degree of retention forestry practices should be required in production forests to preserve habitat continuity. Our study shows that such decisions are likely to lead to positive effects that can persist for centuries.
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•Deadwood density is given for six main tree species by five decay classes.•Pine, spruce and grey alder have lower relative loss of density compared to other species.•No differences in wood density ...between dry, medium and wet areas was noticed.•For pine, spruce and birch the C concentrations were affected by the decay class.•For all the examined tree species the N concentration in dead wood was increasing with increasing decay class.
Forest ecosystems are an important carbon (C) pool, and the decomposition of dead wood plays a key role in its C cycle. Based on the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, IPCC Guidelines for National Greenhouse Gas Inventories were established. Nations that have signed the agreements are encouraged to quantify C pools and fluxes in their forests, including its proportion occurring as dead wood. There are significant differences in density and C concentration of dead wood among tree species. In managed hemiboreal forests of Estonia the dead wood density, and C and N concentration changes in different decay classes for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), silver and downy birch (Betula pendula Roth. and Betula pubescens Ehrh.), black alder (Alnus glutinosa (L.) Gaertn.), grey alder (Alnus incana (L.) Moench.) and European aspen (Populus tremula L.) have been assessed. All together 548 sample discs taken from logs (measurements were restricted to fallen dead trees only) were collected. The results revealed a decrease in mean dead wood density with progressing decay state for all studied tree species. Pine, spruce and grey alder had the smallest wood density reduction with progressing decay state, retaining 37%, 30%, and 36% of initial density, respectively. Other broadleaved tree species (birch, black alder and aspen) had the greatest density reduction during decomposition, retaining 24%, 23%, and 16% of initial density, respectively. For all studied tree species there were no significant differences of wood density between sites with different moisture conditions (dry, medium or wet areas). In case of pine, spruce and birch the C concentrations were significantly affected by the decay class, while in case of both alders and aspen the C concentrations were not significantly affected by changes in decay classes. For all the assessed tree species the N concentration in dead wood was increasing with increasing decay class.
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Previous studies have found negligible effects of single prescribed fires on coarse woody debris (CWD), but the cumulative effects of repeated low-intensity prescribed fires are unknown. This ...represents a knowledge gap for environmental management because repeated prescribed fires are a key tool for mitigating wildfire risk, and because CWD is recognized as critical to forest biodiversity and functioning. We examined the effects of repeated low-intensity prescribed fires on the attributes and stocks of (fallen) CWD in a mixed-species eucalypt forest of temperate Australia. Prescribed fire treatments were a factorial combination of two seasons (Autumn, Spring) and two frequencies (three yearly High, 10 yearly Low), were replicated over five study areas, and involved two to seven low-intensity fires over 27 years. Charring due to prescribed fires variously changed carbon and nitrogen concentrations and C to N ratios of CWD pieces depending on decay class, but did not affect mean wood density. CWD biomass and C and N stocks were significantly less in Fire than Control treatments. Decreases in total CWD C stocks of ∼8 Mg/ha in Fire treatments were not balanced by minor increases in pyrogenic (char) C (∼0.3 Mg/ha). Effects of prescribed fire frequency and season included significantly less C and N stocks in rotten CWD in High than Low frequency treatments, and in the largest CWD pieces in Autumn than Spring treatments. Our study demonstrates that repeated low-intensity prescribed fires have the potential to significantly decrease CWD stocks, in pieces of all sizes and particularly decayed pieces, and to change CWD chemical attributes. CWD is at best a minor stock of pyrogenic C under such fire regimes. These findings suggest a potential trade-off in the management of temperate eucalypt forests between sustained reduction of wildfire risk, and the consequences of decreased CWD C stocks, and of changes in CWD as a habitat and biogeochemical substrate. Nonetheless, negative impacts on CWD of repeated low-intensity prescribed fires could be lessened by fire intervals of 10 rather than three years (to decrease losses of decayed CWD), and fires in moist rather than dry conditions (to conserve large CWD).
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
•Rainfall and live tree basal area important predictors of dead standing trees (DST) and coarse woody debris (CWD).•CWD increased and DST decreased with increasing time since wildfire.•Wood density ...had opposing effects on CWD and DST.•Increases in DST associated with greater time spent in severe drought.•CWD and DST not affected by fire frequency or presence of timber harvesting.
Dead wood, including dead standing trees (DST) and coarse woody debris (CWD), is a critical component of forest ecosystems that provides habitat and refugia for fauna, flora, and microbial communities and plays a key role in carbon and nutrient cycling. However, few studies have modelled the long-term dynamics of dead wood, limiting our ability to predict how the abundance and composition of dead wood may change with climate change or altered fire regimes. Here we analyse DST and CWD data in 884 plots encompassing multiple field campaigns and forest types of varying canopy cover and species composition across the State of Victoria in temperate south-eastern Australia. We use boosted regression tree modelling to examine the relative influence of disturbance history and tree functional traits on dead wood biomass while accounting for the influence of environmental and climatic factors and stand attributes across a broad productivity gradient. We modelled absolute and relative dead wood biomass by size (‘small’ 100 < 200 mm diameter, ‘medium’ 200 < 500 mm diameter, ‘large’ ≥ 500 mm diameter) and decay classes (sound to advanced decay) to evaluate the consistency of predictor effects among different components of dead wood. We found that live tree basal area and mean annual precipitation were influential predictors of both DST and CWD biomass, indicating an over-arching effect of forest productivity on dead wood biomass. Fire history was also an important predictor, with DST biomass decreasing and CWD biomass increasing with time since last wildfire. The proportion of large DST biomass increased with increased tree mortality as a result of fire interval and time in drought. DST biomass also increased and CWD biomass decreased with increasing wood density, and this was relatively more important than the other functional traits we examined (heartwood nitrogen content and bark type). Our study suggests that forest productivity, fire history, drought and wood density are important determinants of dead wood, as they influence dead wood inputs and outputs. Our study reveals the broad-scale drivers of dead wood biomass, and the potential for altered fire regimes and changing climate to influence live- to dead wood dynamics and associated ecosystem functions.
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•We measure the habitat relationships of wood-inhabiting fungi using DNA metabarcoding.•Old stands had larger species pools, at the landscape but not at the trunk scale.•High landscape-scale forest ...cover supported trunk scale fungal richness.•Increase in local dead-wood volume increased number of red-listed species per trunk.•Conservation conclusions based on DNA in wood same as in former fruit-body surveys.
Understanding the distribution of biodiversity across forest landscapes is a key issue for the spatial planning of conservation management. Obtaining such spatial perspective is challenging because a large part of biodiversity remains hidden to the conventional survey approaches. High-productivity forests are probably the hotspots of hidden biodiversity and, at the same time, under severe timber harvesting pressure. We used DNA-metabarcoding approach to assess habitat quality of successional high productivity forests for wood-inhabiting fungi, focusing on fungal diversity that remains hidden in fruit-body surveys. We sampled a fixed amount of coarse fallen Norway spruce trunks in 40 naturally developing stands ranging from 44 to 140 years of age in hemi-boreal Estonia. We found three main habitat quality patterns. The total number of fungal OTUs in older (>80 years) stands exceeded that in younger stands due to the accumulation of rare fungi. The proportion of trunks hosting highest number of OTUs and trunk-scale richness of rare fungi were greatest in stands surrounded by extensive forest area. The average number of red-listed species per trunk increased mainly along with the volume of fallen dead wood; large volumes provided quality habitats already before the stands had reached 80 years of age. These results support the view that both substrate amount in the forest stand and habitat connectivity on a landscape scale support fungal diversity in dead wood. Earlier studies on wood-inhabiting fungi have reached similar conclusions based on observations of fungal fruit-bodies. Thus, the overall principle of focusing conservation efforts to remaining high quality habitats and landscapes extends to the fungi hidden to the conventional survey methods.
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•Wood specific gravity-WSG loss, mass loss along tropical forest disturbance gradient.•Core position relative to soil interact with bark thickness to influence WSG loss.•Higher initial wood N content ...and thicker bark leads to higher WSG loss for up core.•Higher termite infestation and higher mass loss in open habitats than in forests.•WSG loss is not a good predictor of mass loss especially in the presence of termites.
Woody debris represents a substantial reservoir of carbon in forests. Disentangling the effects of factors affecting wood decomposition rates is therefore important. We examined the abiotic and biotic factors affecting wood decomposition across a disturbance gradient from mature forest to open land in a tropical montane site in Xishuangbanna, SW China. Wood logs (n = 280) of two native species with contrasting wood specific gravity (WSG), Castanopsis mekongensis (0.75) and Litsea cubeba (0.42), were exposed on the ground for three years. For each log, WSG was monitored at intervals by taking cores from top-half (up) and bottom-half (down) of the log. Mass loss was measured at the end of the experiment.
WSG loss rates were similar across the disturbance gradient and the species effect varied with core position. For Castanopsis, which had higher initial WSG and wood N concentration and much thicker bark, up-cores had consistently higher WSG loss over the study period. This species also had substantially higher WSG loss for up-cores, but interspecific difference among down-cores was small.
For mass loss, there was a complex interaction between species, habitat and the presence of termites. Litsea with low initial WSG experienced approximately two-fold higher mass loss in the absence of termites, but the difference between species was smaller in the presence of termites. Both species experienced higher mass loss in open habitats than in forests, but the termite effect was smaller in open habitats especially for Litsea. There was no interspecific difference in susceptibility to termite infestation, but infestation rates were higher in regenerating forests and open land than in mature forest. WSG loss explained 0% and 19% of mass loss variation in Listea and Castanopsis, respectively, in absence of termites and 0% for both in the presence of termites.
Afterlife effects of wood functional traits interact with abiotic conditions and decomposition processes (microbial decomposition, macro-organisms (termites), photo-degradation) in a complex manner to determine wood decomposition rates. WSG loss is not a reliable predictor of mass loss. These results have important implications for understanding the carbon cycle in tropical landscapes that are undergoing anthropogenic disturbance.
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•We assessed rodent response to coarse woody debris manipulations over 10 years.•Addition and removal of coarse woody debris did not affect rodents in our study area.•Over time, ...rodent community composition was relatively similar among treatments.•As expected, over time, captures of two dominant species varied by season and year.
Coarse woody debris (CWD) is a structural feature in forests throughout the United States that provides unique cover, runways, and microclimate for various wildlife species. While use and selection of CWD for rodent foraging, travel, and nesting, which can impact an individual’s fitness, has been demonstrated across numerous studies, the role of CWD presence and abundance in rodent population and community dynamics varies across studies. To better understand rodent and CWD relationships, we studied rodent populations across two periods of CWD manipulation in randomly assigned experimental treatments in South Carolina (Period I: March 1996–November 2000; removal of all snags and fallen logs, removal of fallen logs only, and Control, and Period II: January 2002–September 2006; downed woody debris addition, snag addition, and Control). Overall, we found minimal effects of experimental treatments on the rodent community composition and structure, and community level variation was mainly explained by cotton mouse (Peromyscus gossypinus) and southern flying squirrel (Glaucomys volans) captures. There were no experimental treatment effects on captures of cotton mice and southern flying squirrels, but we observed variation across seasons and years. Our study shows that over the long-term, rodent population and community dynamics are not affected by experimental manipulations of CWD in our study area.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Decay rates of beech wood blocks on the Apennines were relatively high.•Beech deadwood decay was lower in south- than north-facing sites on these Mediterranean mountains.•Soil properties, slope and ...exposure influenced the decay processes in these sites.
Forests contribute to the sequestration of organic carbon (C). A key role in forest C cycling is played by deadwood. While a broad range of literature on deadwood decay (above-ground) exists, the mechanisms occurring in the transition zone from deadwood to the humus are poorly understood. In particular, scarce information is available on the temporal patterns of wood compounds (such as lignin and cellulose) during decay processes.
Our objective was to provide a deeper understanding on deadwood decay in a Mediterranean montane environment by focussing on semi-natural forests of Fagus sylvatica L. (beech). The decay process was studied in a field experiment (in the Majella mountains, Apennine Mountains, Italy) among an altitudinal transect at different climatic conditions. Beech wood blocks (mass, cellulose, lignin) having all an equal in size (5 cm × 5 cm × 2 cm) were placed in soil mesocosms to investigate over one year changes in the overall mass, cellulose and lignin content. The sites were along an altitudinal gradient, reflecting different climatic conditions. The effect of exposure (north- vs. south-facing slopes) was also considered. Deadwood, cellulose and lignin dynamics were related to soil parameters (pH, grain size, moisture, temperature) and climate data. Deadwood decayed very fast and followed an exponential trend. The decay rate constants of the deadwood mass significantly (positively) correlated with air temperature and soil moisture: the lower the temperature, the lower the evapotranspiration, the higher the moisture availability, and the higher the decay rates. Lignin decayed more slowly than cellulose, resulting in average decay rate constants (k) between 0.368 and 0.382 y−1. Soil properties and topographic traits (slope and exposure) strongly influenced the decay processes. At south-facing sites (having an altitude < 1300 m a.s.l., above sea level), decay processes were lower owing, most likely, to drier conditions. The climosequence revealed slower beech deadwood decay processes in south- than north-facing sites of these Mediterranean mountains, owing to the drier conditions. In-field mesocosms were useful to define meaningful indicators of warming-induced changes on the linkages between C storage in beech deadwood and decomposition processes as a function of altitude and exposure.
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