Characteristics Of Coarse Woody Debris Research Articles

Bryophyte Conservation in Managed Boreal Landscapes: Fourteen-Year Impacts of Partial Cuts on Epixylic Bryophytes

Clear cut harvest simplifies and eliminates old growth forest structure, negatively impacting biodiversity. Partial cut harvest has been hypothesized (1) to have less impact on biodiversity than clear cut harvest, and (2) to encourage old growth forest structures. Long-term studies are required to test this hypothesis as most studies are conducted soon after harvest. Using epixylic bryophytes as indicators, this study addresses this knowledge gap. Fourteen years after harvest, we examined changes in epixylic bryophyte community composition richness and traits, and their microhabitats (coarse woody debris characteristics and microclimate) along an unharvested, partial cuts and clear cuts harvest treatment in 30 permanent plots established in the boreal black spruce (Picea mariana) forests of northwestern Quebec, Canada. Our results were compared to those of an initial post-harvest study (year 5) and to a chronosequence of old growth forests to examine species changes over time and the similarity of bryophyte communities in partial cut and old growth forests. Coarse woody debris (CWD) volume by decay class varied among harvest treatments with partial cuts and clear cuts recording lower volumes of early decay CWD. The epixylic community was richer in partial cuts than in mature unharvested forests and clear cuts. In addition, species richness and overall abundance doubled in partial and clear cuts between years 5 and 14. Species composition also differed among treatments between years 5 and 14. Furthermore, conditions in partial cut stands supported small, drought sensitive, and old growth confined species that are threatened by conditions in clear cut stands. Lastly, over time, species composition in partial cuts became more similar to old growth forests. Partial cuts reduced harvest impacts by continuing to provide favorable microhabitat conditions that support epixylic bryophytes. Also, partial cut harvest has the potential to encourage old growth species assemblages, which has been a major concern for biodiversity conservation in managed forest landscapes. Our findings support the promotion of partial cut harvest as an effective strategy to achieve species and habitat conservation goals.

Influence of Forest Management Activities on Forest Fire Fuels in Coarse Woody Debris for Pinus densiflora Stands in South Korea

본 연구는 산불에 취약한 대표 침엽수종인 소나무 임분을 대상으로 산림시업이 고사율과 고사목 연료량에 미치는 영향을 분석하고자 하였다. 이를 위해 제 6차 국가산림자원조사 고사목 자료 중 시업지 소나무림 40plots, 비시업지 소나무림 14plots를 분석자료로 사용하였다. 시업지 임분의 고사율은 약 1.6%, 비시업지 임분의 고사율은 5.3%으로 나타났으며, 산불확산에 영향을 미치는 고사목의 산불연료량은 비시업지 임분이 2.2TOE ha-1으로 시업지 임분 1.6TOE ha-1에 비해 높게 나타났다. 부후등급별로 비교한 결과, 산불에 가장 취약한 고사Ⅰ등급이 차지하는 비율은 시업지 22%, 비시업지 29%으로 비시업지 임분에서 더 높은 고사목 분포를 보이고 있었으며, 부후도가 높아질수록 비시업지 임분이 시업지 임분에 비해 차지하는 연료량이 상대적으로 더 높게 나타났다. 따라서, 비시업지임분에서 지표화에서 수관화로 확산시키는 역할을 하는 고사목이 차지하는 연료량이 더 높게 추정됨에 따라 산불확산위험성이 더 높을 것으로 판단된다.The objective of this study is to estimate the effects of forest management activities on mortality rates and fuel characteristics of coarse woody debris for Pinus densiflora stands in South Korea. This study used 40 managed plots and 14 unmanaged plots from the 6th National Forest Inventory plots. The results indicated that mortality rates of the managed stands were about 1.6% while those of the unmanaged stands were about 5.3%. The amount of coarse woody debris affecting forest fire spread was 2.2TOE ha⁻¹ for the unmanaged stands, while 1.6TOE ha⁻¹ for the managed stands. According to the results of decay class analysis, the ratio of decay class I, the most vulnerable to forest fires, was 22% for the managed stands while 29% for the unmanaged stands. Therefore, the unmanaged pine stands had higher fuel loads for forest fire in terms of coarse woody debris and higher decay rates than the managed Pinus densiflora stands. This information could be very useful to understand forest fire fuels in coarse woody debris for Pinus densiflora stands in South Korea.

Coarse Woody Debris Variability Due to Human Accessibility to Forest

Coarse woody debris (CWD) plays an important role in supporting biodiversity and assisting ecological processes. Sometimes local people intervene modifying the expected distribution of CWD components, harvested as fuel wood. The effect of the human accessibility (HA) on the volume and characteristics of CWD (snag, downed log and stump) was investigated in the natural uneven-age mixed hardwood stands of the Hyrcanian forests of Iran to quantify the impact on CWD. The HA was classified into three classes (easy, medium and difficult) on the basis of slope class, slope direction to the nearest road and road type. As expected, a negative relationship between the degree of accessibility was found with respect to the main qualitative and quantitative indices referring to CWD. The results showed that the volume of CWD decreased with an increase in human accessibility class (HAC), thus the mean volume of CWD in the difficult, medium and easy accessibility classes were 14.87 m3 ha−1, 8.84 m3 ha−1 and 4.03 m3 ha−1, respectively. The decrease in CWD volume was more associated with the decreasing volume of small diameter of low decayed downed logs. The ratio of snag volume to standing volume, the ratio of downed log volume to the volume of trees and the ratio of CWD volume to standing volume increased with a decrease in HAC, while the ratio of downed log volume to snag volume decreased with a decrease in HAC. No selective behaviour on the botanical species of CWD was recorded. For ecological forest management, the effect of HAC on CWD should be considered. A constant supply of snags and downed logs must be preserved to assure a high level of biodiversity. To balance social needs and biodiversity requirements, an increased level of CWD retention might be needed in areas with easy accessibility. The obtained results may be useful when ecological and socio-economical needs have to be taken into consideration in future policy-making decisions.

Coarse Woody Debris Following Silviculture Treatments in Southwest Mixed-Conifer Forest

Coarse woody debris (CWD) is an important component in the structure and function of southwestern mixed-conifer forest ecosystems. However, fire suppression and exclusion policies have changed the structure and fuel loads, including CWD, during the last 130 years. Consequently, managers are faced with the threat of stand replacement fires over large spatial areas and are seeking solutions to these challenges using silvicultural techniques. Our paper presents CWD characteristics based on 100-h and 1000-h time-lag fuels before (2006) and after (2016) silvicultural treatments including harvest, prescribed fire, and no treatment (control) on mixed-conifer forests in southcentral New Mexico, USA. Results indicated late-season broadcast burns characterized by mild fire behavior reduced 100-h CWD (Mg ha−1) and potentially 1000-h CWD. However, because control sites also saw reduced 1000-h CWD, this result was confounded. Harvest treatments maintained 1000-h CWD, which could be considered a compensatory response given the decrease in CWD on adjacent control sites over the same time period. This was supported by an increase in 1000-h logs per 75 m transect on harvest sites as compared to control sites. Silvicultural prescriptions including prescribed fire are useful tools to increase or decrease CWD to meet management objectives.

Dynamics of Coarse Woody Debris Characteristics in the Qinling Mountain Forests in China

Coarse woody debris (CWD) is an essential component in defining the structure and function of forest ecosystems. Long-term dynamics of CWD characteristics not only affect the release rates of chemical elements from CWD, but also the species diversity of inhabiting plants, animals, insects, and microorganisms as well as the overall health of ecosystems. However, few quantitative studies have been done on the long-term dynamics of CWD characteristics in forest ecosystems in China. In this study, we conducted nine tree censuses between 1996 and 2016 at the Huoditang Experimental Forest in the Qinling Mountains of China. We quantified forest biomass including CWD and CWD characteristics such as decay states and diameter classes during this period and correlated with stand, site, and climatic variables. The forest biomass was dominated by live tree biomass (88%); followed by CWD mass (6%–10%). Understory biomass contributed only a small portion (1%–4%) of the overall biomass. Significant differences in average annual increment of CWD mass were found among forest stands of different species (p < 0.0001). Forest biomass, stand age, forest type, aspect, slope, stand density, annual average temperature, and precipitation were all significantly correlated with CWD mass (p < 0.05), with forest type exhibiting the strongest correlation (r2 = 0.8256). Over time, the annual mass of different CWD characteristics increased linearly from 1996–2016 across all forest types. Our study revealed that forest biomass, including CWD characteristics, varied by forest type. Stand and site characteristics (forest biomass, forest type, aspect, slope and stand density) along with temperature and precipitation played a major role in the dynamics of CWD in the studied forest ecosystems.

Interactions between plant traits and environmental factors within and among montane forest belts: A study of vascular species colonising decaying logs

We were interested in which biological attributes and environmental variables enhance the colonisation of vascular plant species on coarse woody debris (CWD) within and among forest communities along lower and upper montane forest belts. The study was carried out in the Sudeten Mts (south-western Poland). A total of 364 decaying logs were studied in terms of their characteristics and the cover of vascular plants colonising them. The three-table ordination analysis (RLQ) revealed that 9 plant traits and 11 environmental variables demonstrated significant associations. Decaying logs were colonised by 46 species, which can be classified into six clusters. The clusters differed in distribution and abundance along the lower-upper montane forest gradient. Annual and autochorous plants as well as herb perennials tended to colonise CWD in the lower montane belt, mainly in beech forests whereas tree seedlings, dwarf shrubs and graminoids prevailed on logs in the upper montane belt – in spruce forests. The localisation and site conditions of logs seemed to be a more important factor than the characteristics of CWD itself. There is a relatively low number of species that are frequently involved in the process of colonisation; however, it can be inferred that they differ in their response to the characteristics of dead wood especially the decomposition stage and the size of a log. Nevertheless, compositional and abundance changes in the vegetation that occurred along the altitudinal gradient played the most crucial role.

Stand and landscape scale variability in the amount and diversity of coarse woody debris in primeval European boreal forests

Factors influencing natural variability in coarse woody debris (CWD) as an indicator of ecosystem services in boreal forests need to be better defined. We analysed the CWD characteristics in 194 dynamic primeval boreal forest stands and 3 landscapes under different disturbance regimes. The volume of CWD in the spruce dominated forests linearly increased with increasing annual temperature. The CWD amount and species diversity were higher in spruce than in pine dominated stands. The CWD volume increased in relationship to the types of forest stand dynamics in the order: ‘even-aged’, ‘cohort’, ‘fine-scale gap’. The CWD volumes were 52.3; 207.0 and 146.8m3ha−1 and the dead:live wood volume ratios were 29%, 102% and 60% in the landscapes with disturbance regimes driven by periodic surface fires, cohort-replacing windthrow, and fine-scale gap dynamics, respectively. Mean dead:live wood volume ratios exceeded 100% in spruce stands with even-aged and cohort dynamics and in pine stands with even-aged and fine-scale gap dynamics. The CWD decay class diversity was higher in pine than in spruce dominated stands. The CWD volume distribution by decay class was the most even in forest stands driven by fine-scale gap dynamics in both spruce and pine dominated stands. The CWD position diversity was higher in spruce than in pine dominated forests. Fallen logs dominated among other CWD position types in the spruce dominated stands with cohort and fine-scale gap dynamics and in pine stands with cohort and even-aged dynamics. Pine forests with fine-scale gap dynamics stored the greatest volume of snags. In the spruce dominated stands, the proportion of leaning logs decreased and the proportion of snags and stumps increased among forest dynamic types in the following order: even-aged, cohort, fine-scale gap. The CWD diameter distribution had peaks in small-sized CWD in even-aged spruce stands and pine stands with fine-scale gap dynamics. Mid-sized CWD dominated in spruce stands driven by cohort and fine-scale gap dynamics and pine stands with even-aged and cohort dynamics. The large quantity of CWD that encompassed a wide range of variation in tree species, decay class, position type and size creates a diversity of CWD habitats for saproxylic organisms and ensures functional resilience in boreal forest ecosystems. Our results stress that mean annual temperatures and natural site-specific disturbance regimes should be taken into account when setting targets for CWD volumes and dead:live wood volume ratios for management and restoration of CWD in boreal forests.

A “clearcut” case? Brown bear selection of coarse woody debris and carpenter ants on clearcuts

Forest management alters habitat characteristics, resulting in various effects among and within species. It is crucial to understand how habitat alteration through forest management (e.g. clearcutting) affects animal populations, particularly with unknown future conditions (e.g. climate change). In Sweden, brown bears (Ursus arctos) forage on carpenter ants (Camponotus herculeanus) during summer, and may select for this food source within clearcuts. To assess carpenter ant occurrence and brown bear selection of carpenter ants, we sampled 6999 coarse woody debris (CWD) items within 1019 plots, of which 902 were within clearcuts (forests ⩽30years of age) and 117 plots outside clearcuts (forests >30years of age). We related various CWD and site characteristics to the presence or absence of carpenter ant galleries (nests) and bear foraging sign at three spatial scales: the CWD, plot, and clearcut scale. We tested whether both absolute and relative counts (the latter controlling for the number of CWD items) of galleries and bear sign in plots were higher inside or outside clearcuts. Absolute counts were higher inside than outside clearcuts for galleries (mean counts; inside: 1.8, outside: 0.8). CWD was also higher inside (mean: 6.8) than outside clearcuts (mean: 4.0). However, even after controlling for more CWD inside clearcuts, relative counts were higher inside than outside clearcuts for both galleries (mean counts; inside: 0.3, outside: 0.2) and bear sign (mean counts; inside: 0.03, outside: 0.01). Variables at the CWD scale best explained gallery and bear sign presence than variables at the plot or clearcut level, but bear selection was influenced by clearcut age. CWD circumference was important for both carpenter ant and bear sign presence. CWD hardness was most important for carpenter ant selection. However, the most important predictor for bear sign was the presence or absence of carpenter ant galleries. Bears had a high foraging “success” rate (⩾88%) in foraging CWD where galleries also occurred, which was assessed by summing CWD items with the concurrence of bear sign and galleries, divided by the sum of all CWD with bear sign. Clearcuts appeared to increase the occurrence of a relatively important summer food item, the carpenter ant, on Swedish managed forests for the brown bear. However, the potential benefit of this increase can only be determined from a better understanding of the seasonal and interannual variation of the availability and use of other important brown bear food items, berries (e.g. Vaccinium myrtillus and Empetrum spp.), as well as other primary needs for bears (e.g. secure habitat and denning habitat), within the landscape mosaic of managed forests.

Characteristics in coarse woody debris mediated by forest developmental stage and latest disturbances in a natural secondary forest of Pinus tabulaeformis

Coarse woody debris (CWD) characteristics are expected to reflect forest stand features. Few studies evaluated logging-induced stand characteristics of secondary coniferous forests by quantifying the quality and quantity in CWD. After selective logging, the form of secondary forest of Pinus tabulaeformis in the Qinling Mountains is inferior and the regeneration is poor. We measured the CWD characteristics of the forest which had an average CWD biomass amount of 12.56thm−2, and was predominated by abundant logs (65.68%), followed by snags (33.13%). The CWD biomass of P. tabulaeformis and Toxicodendron vernicifluum was significantly higher than that of other species, which took up 85.51% of the total. Although there was no significant difference among different diameter sizes (P>0.05), the CWD biomass of diameter 30–40cm occupied 46.26% of the total (5.81thm−2). Similarly, the CWD biomass of decay class I and II accounted for 39.89% (5.01thm−2) and 33.04% (4.15thm−2) of the total CWD biomass respectively, despite no significant difference among those 5 decay classes (P>0.05). The results indicated that the combination of young forest developmental stage caused by past selective logging and natural and anthropogenic disturbances such as strong wind, tapping lacquer, firewood collection, and illegal tree felling played a crucial role in distribution characteristics of CWD in this secondary forest of P. tabulaeformis.

Patterns of coarse woody debris volume among 18 late-successional and mature forest stands in Pennsylvania1

Coarse woody debris (CWD) provides vital habitat and resources for a broad variety of organisms in old-growth stands. Although many studies have quantified CWD, it remains unclear how variability in tree species composition relates to CWD and snag volume. If CWD and snags (standing dead trees) vary substantially with tree species abundance among different forest types, then the volume of CWD may change in response to shifts in tree species composition. Dominant canopy tree species vary significantly in their decay resistance, shade tolerance, and suppression of light transmission through the canopy; therefore, the rate of CWD input and output may vary with dominant tree species abundance. We hypothesize that CWD and snag volumes are positively related to the abundance of late-successional shade-tolerant canopy species and negatively related to the abundance of mid-successional oak species. To test this hypothesis, CWD was surveyed in 18 late-successional and mature stands across three physiographic provinces in Pennsylvania. The stands were classified by composition: ten as red oak-mixed hardwood and eight as hemlock-mixed hardwood. The hemlock-mixed hardwood stands (vs. the oak-mixed hardwood stands) had larger volumes of CWD and higher relative abundance of shade-tolerant species. CWD volume was positively correlated with the basal area of hemlock and all shade-tolerant species combined. In contrast, basal area of oak species was negatively correlated with the volume of snags and CWD. These results supported the hypothesis that CWD volume is greater in stands dominated by late-successional species, particularly hemlock, than in stands dominated by oak species. The volume of CWD did not change significantly with the abundance of any other tree species (e.g., red maple (Acer rubrum L.), beech (Fagus grandifolia Ehrh.)). Understanding the relationship between tree species composition and the volume of CWD and snags can provide insight into future CWD characteristics as pathogens dramatically change eastern forests (e.g., beech bark disease, hemlock woolly adelgid).

Amount and distribution of coarse woody debris in pine ecosystems of north-western Spain, Russia and the United States

Abstract: The quantity and characteristics of coarse woody debris (CWD) were examined in four distinct pine ecosystems of north-western (NW) Spain, NW Russia and the NW USA. The average CWD volume and biomass ranged from 3.76 m3 ha-1, 1.55 Mg ha-1 in pine plantations in NW Spain to 24.86 m3 ha-1, 6.69 Mg ha-1 in Scots pine forest in NW Russia to 55.35 m3 ha-1, 20.38 Mg ha-1 and 77.04 m3 ha-1, 28.84 Mg ha-1 in ponderosa and lodgepole pine forests in the NW USA. Despite differences in species, ecological conditions and management histories, in all four ecosystems the mean snag volume was less than that of logs, most of the CWD mass was in an intermediate degree of decay, and mature stands had the greatest amount of CWD mass, followed by middle-age and then young stands. The CWD ratio (ratio of dead to live wood volume) ranged from 2.8% to 126.6%, depending on pine ecosystem and stand age, and was influenced by the type of natural and human disturbance. The difference in CWD amount and distribution among the regions studied reflected differences in disturbance history and management practices. Only in NW USA was the sample size large enough to examine the effect of disturbance type on CWD amount and distribution. There, fire and insect damage were found to considerably influence the amount of CWD in both lodgepole and ponderosa pine forests. Comparison of how different factors affect the amount and distribution of CWD in different ecosystems could be useful in developing ecologically sustainable forest management guidelines.

Mineralization and fragmentation rates of bark attached to logs in a northern boreal forest

Predicting the characteristics of coarse woody debris (CWD) and its importance for biodiversity, carbon and nutrient cycling requires narrowing the uncertainties in bark decomposition rate assessments. We estimated bark decomposition rates and compared them to wood decomposition rates of birches (Betula pubescens and Betula pendula), Siberian fir (Abies sibirica), Siberian pine (Pinus sibirica) and Siberian spruce (Picea obovata) in the northern boreal forest of the Komi Republic, Russia. Estimates were made based on the mass loss of bark attached to above-ground fallen and leaning logs dated to have fallen from 1 to 168years previous to sampling. A single-exponential model was used to estimate the mass loss of bark attached to the logs. Decomposition rate estimates of all log bark included mass loss due to fragmentation. Mineralization rate as mass loss per surface area was estimated for non-fragmented bark pieces. The initial bark mass of the tree base was higher compared to that of the rest of the log; it did not depend neither on the tree species nor on the log size. The proportional rate of bark mineralization was the same for Siberian fir, Siberian pine and Siberian spruce logs – 0.040yr−1. The mineralization rate of birch bark was 0.009yr−1. Bark fragmentation accelerated mass loss. Variation in bark decomposition rates was explained by tree species and log diameter and did not depend on tree mortality mode. The bark turn-over time (t95) was 302, 224, 149, 140 and 117years for birch, fir, spruce, Siberian pine with diameter more than 41cm, and Siberian pine with diameter less than 40cm, respectively. Bark decomposed faster than wood for fir (0.034 vs. 0.026yr−1), spruce (0.051 vs. 0.030yr−1) and Siberian pine with diameters less than 40cm (0.054 vs. 0.008yr−1) and (0.065 vs. 0.008yr−1) for logs with diameters more than 41cm. Birch bark decomposed slower than birch wood (0.025 vs. 0.032yr−1). The different decomposition rates of wood and bark suggest that considering wood and bark together as one substrate can result in a less accurate portrayal of decomposition patterns. These bark decomposition rates can be used for modelling carbon dynamics in similar ecosystems. Knowing the turnover time of log bark for these tree species also facilitates the prediction of the quality of CWD in biodiversity studies in boreal forests.

Assessment of coarse woody debris following selective logging in Caspian forests: implications for conservation and management

Information on the amount, distribution, and characteristics of coarse woody debris (CWD) in forest ecosystems is highly demanded by wildlife biologists, fire specialists and ecologists. Owing to its important role in wildlife habitats, fuel loading, forest productivity, and carbon sequestration, coarse woody debris is an indicator of forest health. Two sampling methods including fixed-area plot and line intersect sampling were compared for accuracy and efficiency in measuring CWD. Data were selected from mature beech stands following selective logging in Caspian forests. Line intersect sampling consistently provided estimates similar to the results of a 100% survey (high accuracy). This method also took the least amount of time and effort to map the layout and field line location (high efficiency). Finally, line intersect sampling as an easy and fast survey method is suggested to monitor coarse woody debris (CWD) in Caspian forests.  

Characteristics of Coarse Woody Debris in Different-Age Natural <i>Larix gmelinii</i> Forests in Daxing’anling Mountains

Coarse woody debris (CWD) is composed of dry wood, fallen wood and large branches, and it is an important element for structure and function in forest ecosystems. In this paper, we studied the characteristics of coarse woody debris (CWD) of natural Larix gmelinii forests with different ages in Daxing’anling Mountains. The results show that (1) the CWD volumes in near-mature, middle-age and young forests are 88.55 m3•hm-2, 52.07 m3•hm-2 and 3.96 m3•hm-2, respectively; and their biomasses are 52.96 t•hm-2, 36.22 t•hm-2 and 2.35t•hm-2, respectively. Which indicate that the CWD volumes and biomasses increase with forest ages addition; (2) The CWD volume and biomass follow normal distribution in middle and near-mature forest; (3) the CWD volume and biomass decrease with forest age increasing within decay classes I and II, whereas increase in decay classes III, IVand V; (4) the volume of middle-age and young forests present a near normal distribution with decay class increasing.

Characteristics of coarse woody debris in successional stages of natural beech (Fagus orientalis) forests of Northern Iran

Coarse woody debris (CWD) is an important structural and functional component in forests in Northern Iran. In this study we determine the temporal patterns of CWD in Kheyroud Forests by examining the CWD volume in different decay classes and size classes along a chronosequence of secondary forest succession. The volume of CWD followed the general “U-shaped” temporal trend: the highest in the late successional forest (51.25 m<sup>3</sup>.ha<sup>–1</sup>), lowest in the middle successional forest (25.95 m<sup>3</sup>.ha<sup>–1</sup>) and intermediate in the early successional forest (37.05 m<sup>3</sup>.ha<sup>–1</sup>). The late successional forest had a larger amount of logs, snags and stumps than the other two forests. In contrast, the snag volume did not differ between the late and middle successional forest. CWD in decay classes III and V was greater in the late successional forest than that in the other two forests, while CWD in decay classes II and I did not differ among the three successional forests. CWD in class II and I was significantly higher in the early successional forest than that in the middle successional forest. In the early and middle successional forests, CWD in early decay class was dominated by <I>Carpinus betulus</I> L. followed by <I>Fagus orientalis</I> Lipsky. In the late successional forest, CWD in early decay class was dominated by <I>Fagus orientalis</I> while CWD in the late decay class was dominated by <I>Carpinus betulus</I>. While forest succession had a large influence on the amount of CWD in different decay classes, it had no effect on CWD distribution among the different size classes. Our results suggest that both anthropogenic and natural disturbances have had a long-term effect on the distribution of CWD among three forests.

Macrolichen and bryophyte responses to coarse woody debris characteristics in sub-boreal spruce forest

Coarse woody debris (CWD) forms an important and specific habitat for many species of lichens, liverworts and mosses. We studied the relationships of 88 macrolichen and bryophyte species to CWD characteristics in mature mesic sub-boreal spruce forests in north central British Columbia. CWD characteristics and macrolichen and bryophyte species richness and abundance data were collected. Ordination, regression tree analysis and indicator species analysis were used to establish relationships between selected CWD variables and macrolichen and bryophyte species assemblages, overall species richness and individual species presence and abundance. Decay class and height from ground were the two CWD characteristics that most influenced macrolichen and bryophyte communities. Species composition varied along a continuum of assemblages from a dominance of arboreal lichens on decay class 1 (less decayed) CWD, to Cladonia, Dicranum and Brachythecium species and a diversity of liverworts on decay class 3, to feathermosses and Plagiomnium and Peltigera species on decay class 4 (more decayed) CWD. The height from ground of a log influenced the growth of liverwort and moss species with restricted growth on logs over about 10 cm above the ground. Log species, bark cover and diameter showed more limited influence on community composition in this study. Species were not greatly influenced by aspect (northern versus southern log aspect); however, macrolichen and moss species were more common on the upper sides of logs and several liverwort species were restricted to the lower sides of CWD (upper versus lower sides of logs). These results provide insight into the relationships between CWD characteristics and macrolichen and bryophyte communities, provide a basis for examining forest management impacts on lichen and bryophyte composition and highlight the importance of maintaining a diversity of CWD on the landscape.

Understory vegetation in old-growth and second-growth Tsuga canadensis forests in western Massachusetts

We compared the understory communities (herbs, shrubs, and tree seedlings and saplings) of old-growth and second-growth eastern hemlock forests ( Tsuga canadensis) in western Massachusetts, USA. Second-growth hemlock forests originated following clear-cut logging in the late 1800s and were 108–136 years old at the time of sampling. Old-growth hemlock forests contained total ground cover of herbaceous and shrub species that was approximately 4 times greater than in second-growth forests (4.02 ± 0.41%/m 2 versus 1.06 ± 0.47%/m 2) and supported greater overall species richness and diversity. In addition, seedling and sapling densities were greater in old-growth stands compared to second-growth stands and the composition of these layers was positively correlated with overstory species composition (Mantel tests, r > 0.26, P < 0.05) highlighting the strong positive neighborhood effects in these systems. Ordination of study site understory species composition identified a strong gradient in community composition from second-growth to old-growth stands. Vector overlays of environmental and forest structural variables indicated that these gradients were related to differences in overstory tree density, nitrogen availability, and coarse woody debris characteristics among hemlock stands. These relationships suggest that differences in resource availability (e.g., light, moisture, and nutrients) and microhabitat heterogeneity between old-growth and second-growth stands were likely driving these compositional patterns. Interestingly, several common forest understory plants, including Aralia nudicaulis, Dryopteris intermedia, and Viburnum alnifolium, were significant indicator species for old-growth hemlock stands, highlighting the lasting legacy of past land use on the reestablishment and growth of these common species within second-growth areas. The return of old-growth understory conditions to these second-growth areas will largely be dependent on disturbance and self-thinning mediated changes in overstory structure, resource availability, and microhabitat heterogeneity.

Effects of Forest Type and Disturbance on Diversity of Coarse Woody Debris in Boreal Forest

Coarse woody debris (CWD) volume and diversity are vital attributes of forest ecosystems. However, despite their importance, their long-term dynamics associated with fire- or logging-origin and overstory type have not been examined in boreal forest. We hypothesize that (1) CWD compositional diversity increases with stand development whereas CWD volume follows a U-shaped pattern. Furthermore, we attempted to test if (2) CWD volume and compositional diversity converge for postlogged and postfire stands through stand development, and (3) mixedwoods have more CWD volume and greater compositional diversity than conifer or broadleaf overstory types. We sampled 72 stands ranging in age from 7 to 201 years in fire-origin stands and 7–31 years in managed stands with conifer, mixedwood, and broadleaf overstory types in central boreal Canada. For fire-origin stands, snag volume was 100–260 m3/ha in 7-year-old stands, 5–20 m3/ha in 25-year-old stands, and 25–60 m3/ha in older stands; downed woody debris (DWD) volume decreased from 7 to 72–90 year-old stands, increased in 124- to 139-year-old stands, then either decreased or increased in 201-year-old stands depending on overstory type. CWD diversity increased from 25 to 124–139 year-old and plateaued, but in 7-year-old stands, CWD diversity was as high as that in the 124 and up year-old age classes. Logging resulted in a smaller amount and lower size variability of CWD in 7-year-old stands, with a larger portion being fast-decomposing Betula papyrifera. Most CWD characteristics had not converged by approximately 30 years since disturbance between the two stand origins. More diverse CWD occurred in mixedwoods, but conifer stands contained the greatest CWD volume except in 7 year-old postfire stands.

Long-lasting legacy of forest succession and forest management: Characteristics of coarse woody debris in an evergreen broad-leaved forest of Eastern China

Coarse woody debris (CWD) is an important structural and functional component in evergreen broad-leaved forests in Eastern China. In this study, we determine the temporal patterns of CWD in Tiantong National Forest Park by examining the CWD volume and mass in different decay classes and size classes along a chronosequence of secondary forest succession. The volume and mass of CWD followed the general “U-shaped” temporal trend: highest in the late-successional forest (97.73 m 3/ha, 42.41 Mg/ha), lowest in the middle successional forest (6.13 m 3/ha, 2.84 Mg/ha) and intermediate in the early successional forest (46.12 m 3/ha, 19.36 Mg/ha). The late-successional forest had larger amount of logs and stumps than the other two forests. In contrast, snags biomass and volume did not differ among these three forests. CWD in decay classes III and V was greater in late-successional forest than that in the other two forests, while CWD in decay classes II and IV did not differ among the three successional forests. CWD in class I was significantly higher in the early-successional forest than that in the middle successional forest. In the early and middle successional forests, CWD in early decay class was dominated by Pinus massoniana and followed by Schima superba. In the late-successional forest, CWD in early decay class was dominated by Castanopsis fargesii while CWD in late decay class was dominated by P. massoniana and S. superba. While forest succession had a large influence on the amount of CWD in different decay class, it had no effect on CWD distribution among different size classes. Our results suggested that both anthropogenic and natural disturbances have left a long-lasting legacy on the distribution of CWD among three forests.

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.