Coarse Woody Debris Stocks Research Articles

Крупные древесные остатки в коренных и вторичных среднетаежных ельниках

Restoration of the pool of coarse woody debris after disturbances is one of the mechanisms for maintaining the stability of forest biogeocenoses. The studies of coarse woody debris have been carried out in the “Vepssky Forest” Reserve in the Leningrad Region on 8 sample plots established in primary forests (4 sample plots) and in secondary forests of the 1st generation after logging in 1973–1974 (4 sample plots), where the composition and structure of the stand, as well as the site conditions have been identical to those in primary forests. The coarse woody debris has been inventoried on transects. The stocks of coarse woody debris in primary stands have ranged from 104 to 233 m3 ha–1. Windfall and leaning trees have prevailed. The proportion of deadwood in both primary and secondary forests has been low. Clear cutting has significantly changed not only the stock of coarse woody debris, but also its distribution by decay classes and substrate categories. The stocks of coarse woody debris in secondary forests have ranged from 8 to 40 m3 ha–1, and have been mainly represented by stumps. The coarse woody debris of the 4th and 5th decay classes has almost been absent in primary forests, while in secondary forests the proportion of highly decomposed wood remaining after cutting has been about 50 %. The ratio of coarse woody debris and growing stocks has been on average 1:1 and 1:5 in the biogeocenoses of primary and secondary forests, respectively. The annual carbon balance of coarse woody debris (the difference in fluxes due to the loss of growing forest and the decay of coarse woody debris) has ranged from 0,40 to 2,80 t C ha–1 year–1, averaging 1,75 and 0,63 t C ha–1 year–1 in secondary and primary forests, respectively. The positive annual carbon balance in the coarse woody debris is due to the predominance of the rate of the loss of growing forest over the rate of the decay of coarse woody debris in primary forests as a result of wind disturbances and as a result of self-thinning of the stand in secondary forests.

Estimation of coarse woody debris stocks in forest ecosystems of «Tsyrkunivskyi forest» and «Dergachivskyi forest» Emerald network objects (Kharkiv region)

The estimation of coarse woody debris stocks in forest ecosystems of «Tsyrkunivskyi forest» and «Dergachivskyi forest» Emerald network objects was performed. Estimation was conducted based on State Forest Inventory data of State enterprise «Kharkiv Forest Research Station» forest fund. Data of dead wood in forest stands of eighteen tree species were analyzed. The stock of the following components of coarse woody debris was studied: standing dead wood, fallen dead wood. Data analysis was performed using MS Excel 2016 software. It was found that the total area of forest stands in which standing dead wood was found during forest inventory was 9984.6 ha, or 49.6%, of the total forest area; for fallen dead wood corresponding indicators were 2662.5 ha (13.2%). The total stock of coarse woody debris was 20761 m3, which is concentrated in the stands of pedunculate oak (Quercus robur L.) (75.6%) and Scots pine (Pinus sylvestris L.) (11.1%). Standing dead wood prevailed (80.1%) fallen dead wood (19.9%) in the structure of dead wood volume. Mean volume of standing dead wood by forest type was from 1.3 m3 ·ha–1 (dry maplelinden dibrova) to 33.3 m3 ·ha–1 (wet maple-linden sudibrova), fallen dead wood — from 1.0 m3 ·ha–1 (dry maple-linden dibrova) to 11.5 m3 ·ha–1 (wet maple-linden dibrova). In oak stands mean volume of standing dead wood was 1.4 m3 ·ha–1, fallen dead wood — 1.3 m3 ·ha–1. Obtained results indicate that in general, the dead wood volumes in forest ecosystems in studied Emerald network objects estimated based on State Forest Inventory data, are quite low compared to the forest ecosystems of other protected areas, where one of the priorities are the natural complexes protection and biodiversity conservation. It may be associated with the influence of forestry activities in studied protected areas.

국가산림자원조사 고정표본점 자료를 활용한 고사목의 탄소저장량 추정

The greenhouse gas reduction function of forests is crucial globally in ameliorating climate change. Varying research attempts to assess dead organic matter and carbon stock volume in soil have been conducted. The purpose of this study was to analyze changes in the occurrence of coarse woody debris (CWD) and related carbon stocks using data from the National Forest Inventory (NFI). To monitor changes in forest resources over time, this study used NFI data (2006-2020) that were collected from permanent sample plots every five years; 1,903 sample plots in which CWD occurred were analyzed at each time point and CWD volume was calculated based on tree stem volume. Carbon stocks of CWD were estimated by applying basic woody density and carbon fraction to CWD by tree type and tree decay level. The average volume of CWD decreased from 23.04 to 14.83 ㎥ ha<SUP>-1</SUP> and carbon stocks of CWD were also reduced from 3.36 to 1.86 ton C ha<SUP>-1</SUP>. This analysis estimated carbon stocks of CWD in forests nationwide and the results can be utilized to build a greenhouse gas inventory. Long-term monitoring and research are needed to identify the changing characteristics of CWD carbon storage. As carbon storage in forests is interconnected, monitoring and model development should include trees, CWD, forest floor litter, and soil carbon cycles. Furthermore, an analysis of the effect of anthropogenic activities on carbon cycles in future research would be useful.

Оцінювання запасів грубого деревного детриту у лісових екосистемах національного природного парку «Слобожанський»

Dead wood is an important component of forest ecosystems. It performs a number of environmental functions. Coarse woody debris includes standing dead trees, fallen dead trees, fragments of fallen trees (trunks), branches (fragments of branches), and rough tree roots. It is a substrate and habitat for living organisms, including a number of species of mosses, lichens, fungi, invertebrates, as well as birds and mammals. Woody detritus plays an important role in the biological cycle of substances and energy, and carbon deposition, is a source of nutrients. Therefore, the study of quantitative and qualitative features of dead wood, in particular on protected areas, is a considerable nowadays problem. The aim of the work is to estimate identified by forest inventory stocks of dead wood in forest ecosystems of Slobozhansky NNP by categories, as well as to analyze the distribution of its volumes in stands of dominant tree species and forest types. The estimation of coarse woody debris stocks was performed based on forest inventory data of Slobozhansky National Nature Park conducted by Ukrainian State Project Forestry Production association “Ukrderzhlisproekt”. Data from 493 forest stands of nine tree species were analyzed. The stock of the following fractions of coarse woody debris was studied: standing dead wood, fallen (downed) dead wood. Data analysis was performed using MS Excel 2016 software. It was found that the total area of forest stands in which standing or downed dead wood was found during forest inventory was 2149.8 ha, or 47.5% of the total forest area of NNP. The total stock of coarse woody debris was 19478 m3, more than 95% of which is concentrated in the stands of Scots pine (Pinus sylvestris L.) (78.8%) and pedunculate oak (Quercus robur L.) (16.6%). Standing dead wood prevailed (62.1%) fallen dead wood (37.9%) in the structure of dead wood volume. The volume of dead wood was in the range of 5–50 m3∙ha–1, and on average in studied forest ecosystems in which it was found was 9.1 m3∙ha–1. In Scots pine forest stands coarse woody debris was found on an area of 1703.5 hectares with total stock of 15355 m3, consists of standing dead trees (9952 m3, 64.8%) and fallen dead wood (5403 m3, 35.2%). The volume of dead wood in forest stands was 5–50 m3∙ha–1, on average – 9.0 m3∙ha–1. In pedunculate oak stands coarse wood debris was found on an area of 384.7 hectares with a total stock of 3224 m3, consists of standing dead wood (1469 m3, 45.6%) and fallen dead wood (1755 m3, 54.4%). The volume of dead wood in forest stands was 5–20 m3∙ha–1, on average – 8.4 m3∙ha–1.

Assessing Coarse Woody Debris Nutrient Dynamics in Managed Northern Hardwood Forests Using a Matrix Transition Model

Coarse woody debris (CWD) is a dynamic source of nutrients in managed forests of eastern North America. The temporal patterns of nutrient export from CWD are challenging to study, and efficient methods are lacking. We made empirical measurements of CWD density, volume, and nutrient concentrations in 5 stages of decay, and paired them with a decay class transition model to project the long-term nutrient dynamics of CWD in a managed northern hardwood forest. The model was used to describe stand-level changes in CWD nutrient pools over 40 years following a selection harvest, and to compare CWD nutrient pools in managed and unmanaged stands. The C content of CWD decreased throughout decay, and mirrored density losses. N, P, and Ca content increased throughout decay, Mg content remained relatively constant, and K was rapidly lost. At the stand level, despite a rapid loss of mass and density, the model projected an initial gain in total N, P and Ca stored in CWD during the first 4–8 years after harvest, whereas net C, Mg, and K began to decrease immediately. The average volume, mass, C and K stocks of CWD in managed stands were approximately 10% lower than unmanaged stands, and N, P, Ca, and Mg were up to 16% lower. This is the first study to use a decay class transition model to study the dynamics of nutrients other than C, and the model serves as a template upon which other models of CWD decay can be built.

Comparison of measured and modelled change in coarse woody debris carbon stocks in New Zealand’s natural forest

Natural forest comprises approximately 78% of New Zealand’s total forest area and their dead wood carbon pools contribute to the national carbon balance reported under the United Nations Framework Convention on Climate Change. We investigate the accuracy of coarse woody debris (CWD) carbon stock estimates obtained from periodic inventories of New Zealand’s natural forest. Dimensions and decay classes of standing-dead spars, fallen logs and stumps over 10 cm diameter were assessed in permanent plots during two inventory cycles (2002–07 and 2009–14). Carbon in CWD was estimated by multiplying CWD volume with species-specific mean wood and bark density, a density modifier based on decay class, and the carbon fraction. The measured change in CWD between inventories was obtained by subtracting 2002–07 from 2009–14 mean CWD carbon stocks. This measured change in CWD carbon stocks was compared with the modelled change derived by applying a decay model to 2002–07 stocks to determine the losses from decay and adding inputs from the tree mortality recorded between the two measurement cycles. Estimates of CWD carbon stocks from field measurements were 19.9 and 19.5 tC ha−1 in 2002–07 and 2009–14 respectively, with a statistically non-significant change of −0.4 ± 0.6 tC ha−1 (95% C.I.) over the period between measurements implying that CWD carbon is in a steady state. However, the modelling approach gave a significant increase of 2.5 ± 0.7 tC ha−1, implying that CWD stocks are increasing. It appears likely that the primary reason for the discrepancy between the direct measurement and modelling approaches is that CWD carbon stocks are substantially underestimated using current measurement protocols used in the inventory of New Zealand’s natural forest. If CWD carbon stocks in New Zealand’s natural forests are approximately in balance as implied by the direct measurement of CWD stocks, CWD inputs from mortality would have to be balanced by losses from decay. For this to be true, the CWD pool would have to approximate 35.4 tC ha−1 which is 78% higher than its measured value.

Dead wood offsets the reduced live wood carbon stock in forests over 50 years after a stand-replacing wind disturbance

Windthrow disturbances often produce large amounts of dead woody materials in a forest. However, post-disturbance, salvage logging greatly reduces the amount of dead woody materials, and thus, carbon stocks. Because the dead woody materials can persist as coarse woody debris (CWD) for a very long time in cool climatic areas, such as boreal and subalpine forests, salvage logging might have long-term effects on the carbon stocks of disturbed forests. In this study, we examined the effects of windthrow by a super typhoon in 1959 and subsequent salvage logging on the carbon stock of subalpine forests more than a half-century after the disturbance in central Japan. We sampled disturbed and not salvaged (unsalvaged) stands versus disturbed and salvaged stands within 10 years of the disturbance (salvaged) in addition to undisturbed stands (undisturbed). The volume of CWD was higher in the unsalvaged stands versus the other two types of forests. Specifically, the volume of classes with intermediate decay was very high, contributing to greater carbon stocks of CWD in the unsalvaged stands. Although the carbon stock of living trees was higher in the undisturbed stands compared to the disturbed stands (unsalvaged and salvaged), the total carbon stock (live + dead) of the unsalvaged stands (104 Mg C ha−1) was almost equivalent to that of the undisturbed stands (99 Mg C ha−1) and was much higher than that of the salvaged stands (72 Mg C ha−1). This study demonstrates that CWD produced by a typhoon acts as a large carbon stock for more than a half-century, potentially offsetting the loss of live woody biomass in disturbed forests.

Carbon Stocks of Coarse Woody Debris in Central African Tropical Forests

&lt;p&gt;&lt;em&gt;Coarse &lt;/em&gt;&lt;em&gt;W&lt;/em&gt;&lt;em&gt;oody &lt;/em&gt;&lt;em&gt;D&lt;/em&gt;&lt;em&gt;ebris (CWD; defined here as fallen and standing dead trees and tree branches) is a critical-structural and functional component of forest ecosystems that typically comprises a large proportion of total aboveground carbon storage. Coarse woody debris estimation for the tropics is uncommon, and little is known about how carbon storage in CWD will respond to climate change. Given the predominant role that tropical forests play in global carbon cycling, this information gap compromises efforts to forecast climate change impacts on terrestrial carbon balance. In this study, we aimed to identify the variation in &lt;/em&gt;&lt;em&gt;C&lt;/em&gt;&lt;em&gt;oarse &lt;/em&gt;&lt;em&gt;W&lt;/em&gt;&lt;em&gt;oody &lt;/em&gt;&lt;em&gt;D&lt;/em&gt;&lt;em&gt;ebris (CWD) stocks between forest types (Old-growth and selective logging forests) and among the plots in Ipendja mixed lowland terra firme tropical rainforest (central Africa), and we examined the consequence for CWD carbon stocks estimation. The study area is located at Ipendja forest management unit (UFA), close to Dongou district (Likouala Department), in Northern Republic of Congo. Data collection were done with eight rectangular plots, each 25 x 200 m (0.5 ha). The method of line intercepts sampling has been used in each studied site. A total number of 135 CWD samples of diameter &lt;/em&gt;&lt;em&gt;³&lt;/em&gt;&lt;em&gt; 10 cm in the studied plots have been recorded. It was obvious that stock of coarse woody debris in Mokelimwaekili site (mean: 19.96 Mg ha&lt;sup&gt;-1&lt;/sup&gt;; sum: 79.84 Mg ha&lt;sup&gt;-1&lt;/sup&gt;) were higher than those of Sombo site (mean: 8.9 Mg ha&lt;sup&gt;-1&lt;/sup&gt;; sum: 35 Mg ha&lt;sup&gt;-1&lt;/sup&gt;).&lt;/em&gt;&lt;em&gt; &lt;/em&gt;&lt;em&gt;There was a significance difference in Ipendja evergreen forest about CWD stocks across two forest types and plots. &lt;/em&gt;&lt;em&gt;This finding suggests that values vary among forest types and that separate reference values should be adopted for estimates of undisturbed forest carbon stocks in the different ecosystems in Congo basin. Different reference values represent the variability of CWD among forest types and contribute to reducing uncertainties in current estimates of carbon stock in central African forest ecosystems.&lt;/em&gt;&lt;em&gt;&lt;/em&gt;&lt;/p&gt;

Stocks and dynamics of soil organic carbon and coarse woody debris in three managed and unmanaged temperate forests

The effect of forest conservation on the organic carbon (C) stock of temperate forest soils is hardly investigated. Coarse woody debris (CWD) represents an important C reservoir in unmanaged forests and potential source of C input to soils. Here, we compared aboveground CWD and soil C stocks at the stand level of three unmanaged and three adjacent managed forests in different geological and climatic regions of Bavaria, Germany. CWD accumulated over 40–100 years and yielded C stocks of 11 Mg C ha−1 in the unmanaged spruce forest and 23 and 30 Mg C ha−1 in the two unmanaged beech–oak forests. C stocks of the organic layer were smaller in the beech–oak forests (8 and 19 Mg C ha−1) and greater in the spruce forest (36 Mg C ha−1) than the C stock of CWD. Elevated aboveground CWD stocks did not coincide with greater C stocks in the organic layers and the mineral soils of the unmanaged forests. However, radiocarbon signatures of the Oe and Oa horizons differed among unmanaged and managed beech–oak forests. We attributed these differences to partly faster turnover of organic C, stimulated by greater CWD input in the unmanaged forest. Alternatively, the slower turnover of organic C in the managed forests resulted from lower litter quality following thinning or different tree species composition. Radiocarbon signatures of water-extractable dissolved organic carbon (DOC) from the top mineral soils point to CWD as potent DOC source. Our results suggest that 40–100 years of forest protection is too short to generate significant changes in C stocks and radiocarbon signatures of forest soils at the stand level.

Natural and anthropogenic influences on coarse woody debris stocks in Nothofagus–Araucaria forests of northern Patagonia, Argentina

AbstractCoarse woody debris (CWD) is an important element driving ecological processes, strengthening ecosystem resilience and for biodiversity within forest ecosystems. However, the abundance and distribution of CWD and their relation to natural and human factors are poorly known in southern South America. In this work we studied the density and volume of CWD types in Nothofagus–Araucaria stands in northern Patagonia (Neuquén – Argentina) and relationships with forest composition and structure. We also studied their relationships with fire history, topography and human‐related variables. Twenty‐three stands with Nothofagus pumilio, Nothofagus antarctica and/or Araucaria araucana were sampled to estimate quantities of logs, snags and dead branches using the planar‐intersect method. CWD density and volume in these forests were moderate and varied across the landscape with a spatial pattern determined by biotic, abiotic and human use–related variables. Mean CWD volume was 52.9 m3 ha−1 (range: 1.6–143.7) and significantly varied among forest types and watersheds. CWD was positively related to dbh, tree height and slope, but negatively related to tree density. CWD was clearly influenced by composition and structural characteristics of stands, where the tree species traits had an important role. As well, the observed amount and type of CWD, whereby most of the stands showed low levels of old (pre‐disturbance) logs/snags and poor new inputs of deadwood, may be explained by fire frequency. Firewood gathering and livestock grazing negatively affected deadwood stocks and topography counteracts this effect by limiting human access. Fire disturbance history, windthrow and dieback pulses produced by insect outbreaks and human access seemed to be the main causes that best explained CWD spatial distribution and abundance patterns in north‐western Patagonian forests.

High stocks of coarse woody debris in a tropical rainforest, East Kalimantan: Coupled impact of forest fires and selective logging

Forest fires coupled with logging have now become one of the most extensive causes of forest degradation, affecting the balance between carbon emissions and sequestration in lowland tropical forests in Southeast Asia. Being transient pools of disturbance-killed trees, coarse woody debris (CWD) stocks play a key role in the carbon budget of such disturbed forests. Here, we investigated for the first time how logging affects the CWD input during and following a fire and, consequently, post-fire CWD stocks. Measurements were made at a permanent site in Bukit Soeharto Education Forest (BSEF) in East Kalimantan, Indonesia. This site consisted of plots that had been subjected to three different logging intensities (HF: heavily felled, trees with diameter at breast height (DBH) ⩾30cm were felled; LF: lightly felled, trees with DBH ⩾50cm were felled; UF: unfelled), all of which were burned by a fire that occurred during a drought associated with the El Niño Southern Oscillation in 1998, shortly after logging. CWD mass were measured in 2012, following 14years of monitoring the CWD inputs. The average CWD mass across the three logging treatments was 89Mgha−1, which is higher than the reported values for undisturbed forests but within the recorded range for recently disturbed forests. The amount of CWD inputs due to tree death during the fire was similar among the three treatments. However, there was a large difference in the CWD input in the post-fire period. In UF plots, large CWD inputs lasted for 2years following the fire due to delayed tree death, whereas in HF and LF plots, where the above-ground biomass had greatly reduced by selective logging, no further large CWD inputs occurred after the fire. Consequently, the CWD stocks in the HF and LF plots were 50–60% lower than those in the UF plots. A simulation predicted that these CWD inputs during and shortly after the fire still constitute a large proportion of the CWD stocks in 2012, suggesting that the CWD pool is a rather durable carbon store in BSEF. In the HF and LF plots, there was few large diameter CWD pieces, reflecting the selective logging of large diameter trees, whereas, in the UF plots, there were large standing dead and uprooted trees. Since the larger diameter CWD pieces are persist in the forest for a longer time continuing to store carbon and to provide habitats for diverse wild life, selective logging could have large impacts on forest ecology and function not only by decreasing the total CWD inputs and stocks but also by decreasing the large diameter CWD pieces.

Production and stock of coarse woody debris across a hydro-edaphic gradient of oligotrophic forests in the northern Brazilian Amazon

Most studies on coarse woody debris (CWD) in Brazilian Amazonia have been done in disturbed and undisturbed upland forests. However, oligotrophic forest types occupying seasonal flooding environments have been neglected, although they occupy about one-third of the Amazon region. We examined the effect of an environmental gradient with different hydro-edaphic features on production and stock of CWD in an area of the Rio Negro-Rio Branco basin, in Brazil’s state of Roraima. We used 60km of trails (production) and 30 permanent plots (stock) in a sampling grid established at Viruá National Park. Our study demonstrated that production and stock of CWD carbon are the lowest in all of Amazonia. The highest CWD carbon production was found in open-canopy submontane rainforest (0.58±0.63MgCha−1yr−1), which occur in environments that are free of any influence of seasonal flooding. The lowest stocks of CWD carbon (0.35±0.30MgCha−1) was associated with low tree biomass in forest types occurring on sandy soils that are strongly influenced by seasonal flooding. CWD stocks in oligotrophic forests at Viruá are partially explained (∼21%) by tree biomass, which is determined by different environmental conditions across hydro-edaphic gradients. Reference values (CWD carbon as a percentage of tree carbon) were among the lowest in Amazonia (0.91–4.38%), with lower values being associated with formations with low production and stock of CWD. This finding suggests that values vary among oligotrophic forest types and that separate reference values should be adopted for estimates of undisturbed forest carbon stocks in the different ecosystems in Brazilian Amazonia. Different reference values represent the variability of CWD among forest types and contribute to reducing uncertainties in current estimates of carbon stock in Amazonia.

Accumulation and Connectivity of Coarse Woody Debris in Partial Harvest and Unmanaged Relict Forests

When a tree dies, it continues to play an important ecological role within forests. Coarse woody debris (CWD), including standing deadwood (SDW) and downed deadwood (DDW), is an important functional component of forest ecosystems, particularly for many dispersal-limited saproxylic taxa and for metapopulation dynamics across landscapes. Processes, such as natural disturbance or management, modify forest composition and structure, thereby influencing CWD abundance and distribution. Many studies have compared older forests to forests managed with even-aged silvicultural systems and observed a prolonged period of low CWD occurrence after harvesting. With fine-scale spatial data, our study compares the long-term impacts of light partial harvesting on the CWD structure of eastern deciduous hardwood forests. We mapped and inventoried DDW and SDW using variable radius plots based on a 10 m×10 m grid throughout an unmanaged, structurally-complex relict forest and two nearby forests that were partially harvested over 46 years ago. The relict stand had significantly larger individual pieces and higher accumulations of DDW and SDW than both of the partially harvested stands. Connectivity of CWD was much higher in the relict stand, which had fewer, larger patches. Larger pieces and higher proportion of decay-resistant species (e.g. Quercus spp.) in the relict forest resulted in slower decomposition, greater accumulation and increased connectivity of CWD. Partial harvests, such that occur with selection forestry, are generally considered less disruptive of ecosystem services, but this study highlights the long-term impacts of even light partial harvests on CWD stocks and distribution. When planning harvesting events, forest managers should also consider alternative methods to ensure the sustainability of deadwood resources and function.

Repeated prescribed fires decrease stocks and change attributes of coarse woody debris in a temperate eucalypt forest.

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).

Soil-induced impacts on forest structure drive coarse woody debris stocks across central Amazonia

Background: Coarse woody debris (CWD) is an essential component in tropical forest ecosystems and its quantity varies widely with forest types.Aims: Relationships among CWD, soil, forest structure and other environmental factors were analysed to understand the drivers of variation in CWD in forests on different soil types across central Amazonia.Methods: To estimate CWD stocks and density of dead wood debris, 75 permanent forest plots of 0.5 ha in size were assessed along a transect that spanned ca. 700 km in undisturbed forests from north of the Rio Negro to south of the Rio Amazonas. Soil physical properties were evaluated by digging 2-m-deep pits and by taking auger samples.Results: Soil physical properties were the best predictors of CWD stocks; 37% of its variation was explained by effective soil depth. CWD stocks had a two-fold variation across a gradient of physical soil constraints (i.e. effective soil depth, anoxia and soil structure). Average biomass per tree was related to physical soil constraints, which, in turn, had a strong relationship with local CWD stocks.Conclusions: Soil physical properties appear to control average biomass per tree (and through this affect forest structure and dynamics), which, in turn, is correlated with CWD production and stocks.

Gap formation and carbon cycling in the Brazilian Amazon: measurement using high-resolution optical remote sensing and studies in large forest plots

Background: The dynamics of gaps plays a role in the regimes of tree mortality, production of coarse woody debris (CWD) and the variability of light in the forest understory. Aims: To quantify the area affected by, and the carbon fluxes associated with, natural gap-phase disturbances in a tropical lowland evergreen rain forest by use of ground measurements and high-resolution satellite images. Methods: We surveyed two large forest inventory plots of 114 and 53 ha of the Tapajós National Forest (TNF) in the Brazilian Amazon during 2008 and 2009, respectively. We mapped all gaps and collected data on light availability, CWD stocks and tree mortality in the field. Gap location, canopy openness (CO) and leaf area index (LAI) estimated in the field were compared with two IKONOS–2 high-resolution satellite images acquired at approximately the time of the field measurements. Results: In the two large plots (167 ha total area) we found 96 gaps. The gaps represented 1.42% of the total area and gaps <1-year-old accounted for 0.81% of the plot area. In TNF, the production of CWD in recent gaps was 0.76 Mg C ha−1 year−1 and the mean tree mortality was 2.38 stems ha−1 year−1. The area of gaps estimated using thresholds of light intensity measured by remote sensing optical instruments was twice as large as the gap areas measured on the ground. We found no significant correlation between spectral remote sensing images and CO or LAI, probably due to the high degree of shadow in the high-resolution satellite images. Conclusions: We present the first statistics of CWD production based on gap size in the tropical forest literature. Tree mortality and CWD flux and the forest floor light environment were closely related to gap area. However, less than 30% of the annual tree mortality and CWD flux was associated with gaps, and gaps were difficult to detect using remote sensing methods because of the high proportion of shadow in the images. These results highlight the need for permanent plots in long-term carbon studies.

Carbon stocks in primary and secondary tropical forests in Singapore

Tropical forests contain large reserves of carbon that are vulnerable to perturbation linked to human activities, including deforestation and climate change. Accurate estimates of forest carbon are therefore required urgently to support efforts to conserve tropical forests. We quantified carbon stocks in primary and 60-year-old secondary forest plots located on infertile Ultisols in Bukit Timah Nature Reserve, one of the few remaining areas of forest in Singapore. We used tree census data for 24.2ha of primary forest and 23ha of secondary forest, together with allometric equations, to estimate aboveground and coarse root biomass. Coarse woody debris stocks were censused along 2.44km and 2.12km of transects in primary and secondary forest, respectively. Soil carbon and fine root carbon stocks were assessed from soil samples taken to 3m depth in a 2-ha secondary forest plot and a 2-ha primary forest plot, combined with bulk density measured in a nearby soil profile pit. Total estimated carbon stock in the primary forest, which was located on the hilltop and upper slopes (80–115m elevation), was 337MgCha−1, of which 50% was aboveground biomass, 33% in soil, 12% in coarse roots, 4.6% in coarse woody debris, and 0.8% in fine roots. In the secondary forest, located on lower slopes and valley (50–85m elevation), the total carbon stock was 274MgCha−1 and the relative importance of aboveground biomass and soil were reversed, with 38% in aboveground biomass, 52% in soil, 6.9% in coarse roots, 1.5% in coarse woody debris, and 1.3% in fine roots. Including carbon in deep subsoil (i.e. to 3m) increased soil carbon stocks by ∼40% compared to 1m depth. Overall, the 60-year-old secondary forest contained 60% as much biomass as the primary forest, while the primary forest had lower carbon stocks than other primary forests in the region.

Stocks of coarse woody debris in old-growth lucidophyllous forests in southwestern Japan

This study quantified the mass and inputs of coarse woody debris (CWD) in two old-growth lucidophyllous forests in southwestern Japan: in a steep slope area at Aya and in a flattish bottomland at Okuchi. CWD mass averaged 36.85 Mg ha−1 with eightfold variations at Aya, and 20.77 Mg ha−1 with more than 40-fold variations at Okuchi. CWD inputs estimated from long-term data on tree mortality averaged 36.76 Mg ha−1 over 16 years at Aya and 44.11 Mg ha−1 over 11 years at Okuchi. In both plots, fallen logs were the major form of CWD mass: 74.4% at Aya and 60.2% at Okuchi. About 19% of CWD was snapped and 7% was uprooted at Aya, and about 34% was snapped and 5.4% was uprooted at Okuchi. The CWD mass differed markedly with topographic conditions in both plots, increasing from valleys up to ridges at Aya and from forest down to a stream at Okuchi. Canopy gaps enhanced CWD mass and inputs in both plots: CWD input under gaps was two to three times that beneath closed canopy. These results imply that typhoons would increase CWD mass and inputs on upper slopes on account of the high aboveground biomass stocks and existence of large-diameter trees.

Modelling fallen branch volumes in a temperate eucalypt woodland: implications for large senescent trees and benchmark loads of coarse woody debris

AbstractFallen branches are a substantial component of coarse woody debris and a key ecological resource. The depletion of stocks of coarse woody debris since European settlement has contributed to the degradation of Australian grassy box woodlands, including the loss of biodiversity. Restoration options for remnant woodlands include the augmentation of coarse woody debris stocks. However, the extensive modification of grassy box woodlands has left few reference sites for establishing benchmarks to guide such restoration. In this paper we demonstrate a method for predicting fallen branch debris loads in the absence of reference sites, using data from a yellow box–red gum woodland. Our methodology is in two stages: first, the total volume of branch debris under individual trees was modelled; and second, these models were applied to groups of trees to predict stand‐level loads of fallen branch debris. Although the models were developed for yellow box–red gum woodlands, the methodology would be applicable to other communities that lack reference sites. Predicted benchmark loads of fallen branch debris for yellow box–red gum woodland were between 7.0 m3 ha−1 and 11.9 m3 ha−1. Large senescing trees contributed the bulk of fallen branch debris. Model predictions indicated a 100‐cm diameter at breast height (dbh) tree was 10 times more likely to produce debris than a 50‐cm dbh tree, and if debris was present a 100‐cm dbh tree produced approximately 10 times the volume of branch debris produced by a 50‐cm dbh tree. These results highlight the importance of large senescing trees for the production of fallen branch debris and support the keystone role of large trees within remnant woodlands, and the need to conserve these structures. Our results also support the active management of regrowth woodland stands to facilitate the progression of individual trees to maturity and senescence. In particular, thinning of regrowth stands may promote the growth of retained trees, ensuring they contribute to fallen branch debris stocks with a minimum time lag.

Coarse woody debris stocks as a function of forest type and stand age in Costa Rican tropical dry forest: long-lasting legacies of previous land use

The ecological importance of trees lasts much longer than their life spans. Standing dead trees (snags) and fallen trunks and branches are an important component of above-ground carbon stocks and nutrient reserves, provide habitat for wildlife, and interact with disturbance regimes (e.g. by serving as fuel for fires) (Clark et al. 2002, Harmon et al. 1986, Pyle et al. 2008). Despite these diverse functions, woody debris stocks remain poorly quantified in tropical forests in general (Brown 1997), and in tropical dry forests in particular (Harmon et al. 1995). More empirical studies of the patterns of woody debris and processes that control its dynamics are needed to understand its role in global biogeochemical cycles and for ecosystem simulation models, many of which do not represent coarse woody debris (CWD) as a separate pool (Cornwell et al. 2009).