Coarse Woody Debris Input Research Articles

The carbon budget of coarse woody debris in a temperate broad-leaved secondary forest in Japan

We evaluated the carbon budget of coarse woody debris (CWD) in a temperate broad-leaved secondary forest. On the basis of a field survey conducted in 2003, the mass of CWD was estimated at 9.30 tC ha-1, with snags amounting to 60% of the total mass. Mean annual CWD input mass was estimated to be 0.61 tC ha-1 yr-1 by monitoring tree mortality in the forest from 1999 to 2004. We evaluated the CWD decomposition rate as the CO2 evolution rate from CWD by measuring CO2 emissions from 91 CWD samples (RCWD) with a closed dynamic chamber and infrared gas analysis system. The relationships between RCWD and temperature in the chamber, water content of the CWD, and other CWD characteristics were determined. By scaling the measured RCWD to the ecosystem, we estimated that the annual RCWD in the forest in 2003 was 0.50 tC ha-1 yr-1 or 10%–16% of the total heterotrophic respiration. Therefore, 0.11 tC ha-1 yr-1 or 7% of the forest net ecosystem production was sequestered by CWD. In a young forest, in which CWD input and decomposition are not balanced, the CWD carbon budget needs to be quantified for accurate evaluation of the forest carbon cycle and NEP.

Woody debris stocks and fluxes during succession in a dry tropical forest

In Southern Mexico, shifting cultivation is creating a mosaic of agricultural lands, secondary forests, and disturbed mature forests (montañas). Increased land-use change, due to population and market pressures has changed the structure and function of these forests. This study investigates the stocks and fluxes of woody debris during the course of secondary succession. We inventoried fine (≥1.8 cm to ≤10 cm diameter) and coarse woody debris (≥10 cm diameter) stocks in 28 stands. In a subset of montañas and secondary forest fallows, we monitored inputs and decomposition over a 2-year period. Total woody debris stocks were largest in montañas (37.46 Mg/ha) and in the first year after clearing (milpa, 51.62 Mg/ha). Woody debris was 22% of the total aboveground biomass in montañas and 88% in milpas. Although stocks were highly variable in secondary forest, coarse woody debris stocks were roughly three times larger than fine woody debris stocks. Coarse woody debris stocks decreased following cultivation for 10–15 years, until inputs exceeded losses to decomposition. Inputs were higher in montaña (0.91 Mg ha −1 year −1) than in secondary forest (0.11 Mg ha −1 year −1). Coarse woody debris inputs were higher during the dry season, while fine woody debris inputs tended to be higher during the wet season. Decomposition varied significantly among tree species, with decomposition rate constants from 0.124 to 0.643 year −1 for coarse woody debris and 0.368–0.857 year −1 for fine woody debris. In young forests, when woody debris stocks are largest, cultivation history is the most important factor in predicting stocks of woody debris. As forest age increases woody debris processes, both inputs and decomposition, become increasingly important factors in regulating woody debris stocks, and therefore age is a better predictor of woody debris stocks in older forests.

Modelling coarse woody debris dynamics in even-aged Scots pine forests

Coarse woody debris (CWD) has become an important component in the study of forest ecosystems, being a key factor in the nutrient cycle as well as a habitat for many species. CWD dynamics varies greatly from primeval to managed forests. To assess the CWD dynamics, a chronosequence trial was established in two Scots pine forests in the Central mountain range in Spain. Although, the shelterwood system has been applied in both forests, one has received more intensive silviculture, whereas in the other, regeneration has been much more gradual and the thinning regime has not been so intensive. In order to inventory CWD, five decay classes and four categories according to size and CWD type (stumps and fallen logs or branches) were defined. The volume of branches and logs (estimated from length and mean diameter) and the number of stumps by size class and decay class are used to characterise the CWD. The most notable differences between the two silvicultural systems can be appreciated in the graph as peaks for temporary distribution of larger logs and stumps when intensive silviculture is applied. The CWD observed in the forests studied is mainly produced by logging. The maximum volume of logs and branches above 5 cm in diameter is 43.25 m 3/ha after regeneration felling in the first forest, whereas in the other, a maximum of 16.30 m 3/ha is reached at 60 years, just after thinning. Large stumps (diameter equal or greater than 30 cm) make up an important part of CWD biomass in these forests just after the regeneration felling. A model was developed to predict the changes in CWD quantity and quality distribution over time as well as predicting the effect of different silviculture options on CWD dynamics. The model integrates two different processes: the CWD inputs (which may be continuous or instant), and the decay process, modelled through a Richards–Chapman function. The average lifetime of CWD obtained ranges from 30 years for stumps over 30 cm in diameter to 8 years for logs with a diameter less than 10 cm.

Coarse woody debris: Inventory, decay modelling, and management implications in three biogeoclimatic zones

To assess recent management practices, post-harvest levels of coarse woody debris (CWD) were measured in the Southern Interior and Northern Interior forest regions of British Columbia. A simple input and decay model was used to estimate the volumes of CWD that might be present at the end of managed forest rotations. In four ecosystems (Sub-Boreal Spruce [SBS] mk1 variant, Interior Douglas-fir [IDF] dm2 variant, Interior Cedar–Hemlock [ICH] dw variant, and ICHvk2/wk3 variants) that were sampled a few years after harvest, between 58 and 80% of the CWD volume came from pieces less than 6 m in length. Modelling of CWD decay and net new CWD input from the developing stand indicated that by rotation end (after 90 years), CWD volumes would have decreased to about 15% (SBSmk1) and 1% (IDFdm2) of the CWD volumes found in mature unmanaged stands.In the ecosystems studied, this research suggests that specific management guidance for deadwood will be required to maintain CWD (outside of reserves) in managed stands. Various techniques could be employed to manage the CWD resource. The purpose of this paper is not to present such techniques; however, the sampling and modelling methodology outlined here will help to formulate management approaches by allowing an assessment of CWD presence throughout a managed forest rotation.

The dynamics of coarse woody debris in boreal Swedish forests are similar between stream channels and adjacent riparian forests

Although numerous studies have focused on the dynamics of coarse woody debris (CWD) in boreal Fennoscandian forests, information on CWD in streams remains limited. To achieve a better understanding of CWD dynamics in streams we compared amounts and characteristics of CWD between streams and adjacent riparian forests in old-growth and managed forest sites, respectively. We also identified distances to the sources of CWD and evaluated these in relation to the lateral zonation of riparian trees. CWD volumes found in the stream channels were related to, but exceeded, the volumes found in the adjacent forest. In-channel volumes separated by species were better correlated with terrestrial volumes of CWD than with volumes of living trees. Tree species appeared to be zoned across the riparian zone, with slightly higher abundances of deciduous trees and lower abundances of Scots pine trees close to the stream. Similar to upland forests, riparian forests were dominated by coniferous tree species, mainly Norway spruce (Picea abies (L.) Karst.). These findings suggest large similarities in CWD input between streams and riparian forests and substantially slower decomposition rates in stream channels compared with those in riparian forest. The results provide an improved basis for creating reliable models of CWD supply and maintenance in streams based on knowledge of forest development and CWD dynamics in the terrestrial environment. Site productivity could potentially be used to predict CWD volumes in stream channels under pristine conditions.

Carbon storage along a stand development sequence in a New Zealand Nothofagus forest

Indigenous forests cover about 6.4×10 6 ha or 24% of the land area of New Zealand and thus form a major carbon (C) pool, but there are few estimates of C storage for these forests, especially at different stages of stand development. C storage and distribution in stemwood, coarse woody debris, forest (floor litter (L) + fermentation /humus(FH)-layers) and upper (0–0.1 m) mineral soil were measured along a stand development sequence in montane zone mountain beech ( Nothofagus solandri var. cliffortioides) forest in the Craigieburn Range, central South Island. C storage in all pools peaked in 125-year-old pole stands (219 Mg/ha) and declined as the stands matured (>150 years old, 192 Mg/ha), and were replaced by seedling stands (10 years old, 152 Mg/ha) following windthrow, to reach a low point (114 Mg/ha) in 25-year-old sapling stands. Coarse woody debris provided an important pool for C storage following catastrophic forest disturbance, and varied reciprocally with stemwood along the development sequence. Above-ground components showed a much greater range (88 Mg/ha) with stand development than forest floor and mineral soil components (16 Mg/ha). Stemwood and coarse woody debris components varied by 136 and 76 Mg/ha, respectively, while litter, the FH-layer and upper mineral soil C varied by 4, 17, and 12 Mg/ha, respectively. The sum of forest floor and mineral soil C ranged between 53 Mg/ha (sapling stage) and 69 Mg/ha (pole stage), and did not differ significantly with age. The litter and FH-layers, and mineral soil were re-sampled after a period of 8 years in the sapling and pole stands. C storage in the litter layers did not change significantly over this period. C storage in the FH-layer declined significantly by 9.7 Mg/ha in the pole stage, but showed little change in the sapling stage. It is hypothesised that C loss resulting from ongoing decomposition in the FH-layer was balanced by continuing inputs of coarse woody debris in the sapling stage, but not in the pole stage, where the coarse woody debris resource was relatively small. There was no change in mineral soil C storage over the 8-year period. It is concluded that, in the absence of disturbance, C storage in the forest floor may vary substantially over periods of <10 years, in contrast to the mineral soil where it appears relatively stable over decadal time intervals.

Stocks and flows of coarse woody debris across a tropical rain forest nutrient and topography gradient

Large pieces of standing or fallen dead wood, known as coarse woody debris (CWD), play important roles in temperate forest carbon and nutrient cycles, and affect the abundance and distribution of many classes of organisms. CWD biomass and inputs are poorly documented in tropical rain forests (TRF), and the causes for their variation at landscape-scales in this biome have not been studied. We quantified standing and fallen CWD stocks and inputs in upland (non-swamp) old-growth TRF at the La Selva Biological Station, Costa Rica. We used a network of 18 0.5 ha plots sited in three edaphic conditions to analyze soil nutrient effects on CWD stocks and inputs controlling for topography, and to examine topographic effects controlling for soil nutrients. The edaphic conditions were flat inceptisols, flat ultisols, and steep ultisols. Chemical analyses confirmed the existence of an almost three-fold gradient in total P and K in the upper 1 m of soil. We also annually censused all live woody stems ≥10 cm diameter above buttresses in each plot in September/October from 1997 to 2000 to obtain data on stand structure and dynamics. Fallen CWD stocks averaged 46.3 Mg ha −1 (22.3 Mg C ha −1), while standing CWD averaged 6.5 Mg ha −1 (3.1 Mg C ha −1). There were no significant differences in volume or mass of standing or fallen CWD among edaphic conditions. Annual inputs of CWD averaged 4.9 Mg ha −1 (2.4 Mg C ha −1). Turnover time of fallen CWD was ca. 9 year. Neither stocks nor inputs were correlated with stand structure (number of trees per plot, plot basal area, or plot estimated above-ground biomass). Potential differences in CWD stocks and inputs among sites with different edaphic conditions may have been obscured by a 10-fold variation in tree mortality among plots and a two-fold variation in mean CWD input among years. Analysis of sample variance showed that stocks of CWD were adequately sampled with the 18 0.5 ha plot design, but that inputs were measured with low precision. At La Selva fallen and standing CWD stocks together equaled ca. 33% of estimated above-ground live woody biomass. Tropical rain forest CWD and its associated carbon are intermediate in pool size and turnover rate between fine litter and live trees. Our results show that scaling up TRF CWD estimates to larger spatial scales may be more constrained by the quality of data obtained over single landscapes than by variation due to zonal soil nutrient and topographic conditions. Both the magnitude and vagility of TRF CWD pools are likely to change with global climate change, but the overall direction of change is uncertain.

Overstory litter inputs and nutrient returns in an old-growth temperate forest ecosystem, Olympic National Park, Washington

Overstory litterfall rates and nutrient returns were determined in an old-growth temperate rainforest watershed in the Hoh River valley, Olympic National Park, Washington. Litter was sorted into green needles, senescent needles, fine wood, reproductive, and miscellaneous litter (mostly arboreal lichens and mosses). Understory and coarse woody debris inputs were not determined. Total annual overstory litterfall averaged 3594 kg·ha–1 and varied among the six plant communities in the watershed. There was a trend for litterfall to be higher in the upper watershed; elevations ranged from 180 to 850 m. Needles provided the greatest amount of litterfall (60%) with woody litter and other material averaging 18 and 22%, respectively. Highest senescent needle litterfall occurred from July to October, but highest woody litterfall was from January to April. Green needles provided only 3% of annual needle litterfall. Green and senescent needle litterfall were related to western hemlock (Tsuga heterophylla (Raf.) Sarg.) basal area, suggesting that this shade-tolerant species was the greatest contributor to needle litterfall. The following quantities (kg·ha–1) of nutrients were returned to the forest floor annually: Ca, 26.8; N, 24.6; K, 4.0; Mg, 3.0; P, 2.9; Mn, 1.7; and Na, 1.2.

The contribution of beech bark disease-induced mortality to coarse woody debris loads in northern hardwood stands of Adirondack Park, New York, U.S.A.

The objective of this study was to adjust previously published estimates of coarse woody debris (CWD) volume and basal areas in northern hardwood forests to account for elevated CWD inputs due to beech bark disease (a disease complex of the scale insect, Cryptococcus fagisuga Lindinger, and a fungus, Nectria spp., on American beech, Fagus grandifolia Ehrh.). Ratios of snags/live tree densities and downed CWD volume/live tree basal area were compared between beech and the codominant, shade-tolerant sugar maple (Acer saccharum Marsh.). The differences between the beech and the sugar maple ratios were used to define the elevated mortality from beech bark disease. Estimated volumes of downed CWD (stumps [Formula: see text] 1.0 m tall and logs), adjusted for effects of beech bark disease, were 108 ± 18 and 48 ± 11 m3·ha-1in old-growth and even-aged, 90- to 100-year-old maturing stands, respectively, representing reductions of 22 and 21%, respectively, compared with observed volumes. Similarly, snag densities were adjusted from 59.7 ± 21.7 to 41.1 ± 26.3 per hectare in the old-growth stands and from 96.3 ± 48.0 to 87.3 ± 46.5 per hectare in the maturing stands. Snag basal areas were reduced 21 and 17% from their observed values to 6.8 ± 3.5 and 3.5 ± 0.6 m2·ha-1in the old-growth and maturing stands, respectively. The adjusted CWD estimates presented here are more historically accurate and ecologically meaningful than previous observations made in diseased northern hardwood forests and, therefore, provide more appropriate target levels for managing CWD in these forest types.

Ice Storm Damage to an Old-growth Oak-hickory Forest in Missouri

-On 6 December 1994 a severe ice storm hit several midwestern states. We inventoried damage and woody debris input from the storm in 30 0.1-ha permanent plots in an old-growth oak-hickory forest in northern Missouri. Twenty-seven percent of 1386 live trees 22 cm dbh were damaged but only 7% were severely damaged. Basswood (Tilia americana) and American elm (Ulmus americana) were the most susceptible species; white oak (Quercus alba), eastern hophornbeam (Ostrya virginiana) and shagbark hickory (Carya ovata) were among the least susceptible. Damage levels increased with stem diameter, and trees occupying dominant crown positions were more heavily damaged than suppressed trees. Damage severity was highly variable across the landscape, but trees on lower slopes and mesic aspects tended to have more damage, even for a given species. Coarse woody debris input from the storm averaged 5.1 m3/ha, 27% of the prestorm volume, with northern red oak (Q. rubra) and white oak contributing 79% of the total. This single event will probably have minimal impact on stand composition and structure, but repeated ice storms at 20-yr intervals likely influence forest dynamics in midwest oak-hickory forests.