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. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. B. W. Brassard collected and analyzed data and wrote the paper. H. Y. H. Chen conceived and designed the study, analyzed data, and critiqued earlier drafts of the paper.     

Fire and site type effects on the long-term carbon and nitrogen balance in pristine Siberian Scots pine forests

Effects of fire and site type on carbon (C) and nitrogen (N) balances were determined by following the change of total and component C and N pools along four chronosequences of fire-prone Siberian Scots pine ecosystems. These differed in the mean return interval of surface fires (unburned – moderately burned, 40 years – heavily burned, 25 years) and site quality (lichen versus Vaccinium site type). Of the Vaccinium site type (higher site quality) only a moderately burned chronosequence was studied. A total of 22 even-aged stands were investigated with stand ages ranging from 2 to 383 years. The C balance was dominated by the opposing dynamics of coarse woody debris (CWD) and biomass and could be divided into three phases: (1) Young stands (up to 40 years)acted as a net source for C of 6-10 mol C m-2 year-1 because the previous generation CWD pool originating from stand-replacing crown fires decayed much faster than biomass increased. During this period the C pool in the unburned lichen type chronosequence decreased from 807 to 480 mol C m-2. (2) Middle aged stands (40-100 years) being in a stage of maximum biomass accumulation were a net sink of 8-10 mol C m-2 year-1. (3)Maturestands (100 to > 350 years) continued to sequester C at a lower rate (0.8-2.5mol C m-2 year-1). Differences in the rates of C sequestration during the two later phases could be explained by the complex interaction between surface fire regime and site type. Recurrent surface fires resulted in enhanced mortality and regularly redistributed C from the living to the CWD pool thereby lowering the rate of C sequestration. Site quality determined the potential to recover from disturbance by fire events. Differences in site type did not correlate with soil and total ecosystem N pool size. However, the N status of needles as well as the N pool of physiologically active tissue was highest in the stands of the Vaccinium type. The woody C pool (biomass + CWD) was sensitive to differences in surface fire regime and site type. It was lowest in the heavily burned lichen type chronosequence (297 ± 108 mol C m-2), intermediate in the unburned and moderately burned lichen type chronosequence (571 ± 179 mol C m-2) and highest in the moderately burned Vaccinium type chronosequence (810 ± 334 mol C m-2). In contrast, the total soil C pool (organic plus mineral layer down to a depth of 25 cm) was independent of stand age, surface fire regimeand site type and fluctuated around a value of 250 mol C m-2. The organic layer C pool oscillated in response to recurring surface fires and its C pool was dependent on time since fire increasing at a rate of about 1.5 mol C m-2 year-during the first 40 years and then reaching a plateau of 170 mol C m-2. The total ecosystem N pool was 7.4 ± 1.5 mol N m-2 on average of which only 25 % were stored in biomass or coarse woody debris. Total ecosystem N was independent of stand age, surface fire regime and site type. No correlation was found between total ecosystem C and N pools. Average total ecosystem C:N ratio was 114 ± 35 mol C mol N-1. A conceptual model illustrating how changes in the regime of stand-replacing crown fires and recurrent surface fires and changes in site quality interact in determining the long-term C balance in Siberian Scots pine forests is presented.     

Biomass accumulation over the first 150 years in coastal Oregon Picea‐Tsuga forest

Abstract. Production and mortality are the component processes that together determine the biomass dynamics of forests. Due to the significant role of forests in the global carbon cycle, it is important to assess how these two processes affect the maximum biomass attained by forests, as well as the dynamics leading up to and following peak biomass. We address these questions for two sets of plots in Picea sitchensis‐Tsuga heterophylla forest on the northern Oregon coast that originated from a catastrophic wildfire in the 1840s, using new data on dynamics of live trees and stocks of coarse woody debris (CWD). The set of plots closest to the ocean and occupying steeper, more dissected terrain with areas of thin soils has lower biomass, lower net primary production (NPP) of bole wood and higher tree mortality as a fraction of standing biomass. The two sets of plots have similar CWD levels, most of which has accumulated in the last 25 yr. The present disparity in biomass between the two sets of plots appears to be the result of lower NPP on the low‐biomass plots for the entire 140+ yr history of the forest. Over the 58 yr that the high‐biomass plots have been measured (from stand age 85 to 143 yr), NPP of bole wood has declined by 41%. Only ca. 6% of this decline can be accounted for by an increase in maintenance respiration of woody tissues. For both sets of plots relative constancy of biomass in the long term appears likely, due to a short time lag in tree regeneration, asynchronous tree mortality and little overall decline in NPP of bole wood in recent decades. However, since tree mortality as a fraction of standing biomass is higher on the low‐biomass plots, and NPP of bole wood is slightly lower, the difference in biomass between the two sets of plots should increase if current rates of production and mortality persist.     

Influence of habitat and microhabitat on epigeal spider (Araneae) assemblages in four stand types

Studies based on presence/absence of a species may provide insight into habitat associations, allowing the distribution of species to be predicted across the landscape. Our objective was to characterise the epigeal spider fauna in three mature boreal forest types (conifer, mixedwood and deciduous) and a disturbed habitat (clearcut) to provide baseline data on the spider species inhabiting major forest types of boreal northwestern Ontario, Canada. Only spring-active epigeal spiders were considered for logistical reasons. We further identified the coarse woody debris structure and microhabitat characteristics within these stand types to try to refine our ability to predict the within-stand occurrence of spiders. We found the clearcut habitat strongly dominated by the Lycosidae with 55% of spiders represented by a single species, Pardosa moesta Banks. The forested habitats were more diverse, with web-building families forming a large component of the fauna and many species represented by only a few individuals. The spider composition of the deciduous stands (aspen and mixedwood) was very similar, and distinct from that of spruce stands. Species such as Agroeca ornata (Emerton) (Liocranidae) and Pirata montanus Emerton (Lycosidae) were strongly associated with deciduous leaf litter. Within the spruce stands, Agyneta olivacea (Emerton) (Linyphiidae) and Pardosa uintana Gertsch (Lycosidae) were associated with feathermoss rather than Sphagnum microhabitats. Many of the habitat associations observed at Rinker Lake do not conform well to those described in the taxonomic literature as typical for the species. Few associations with coarse woody debris or microhabitat attributes (other than ground cover type) were found.     

From Models to Measurements: Comparing Downed Dead Wood Carbon Stock Estimates in the U.S. Forest Inventory

The inventory and monitoring of coarse woody debris (CWD) carbon (C) stocks is an essential component of any comprehensive National Greenhouse Gas Inventory (NGHGI). Due to the expense and difficulty associated with conducting field inventories of CWD pools, CWD C stocks are often modeled as a function of more commonly measured stand attributes such as live tree C density. In order to assess potential benefits of adopting a field-based inventory of CWD C stocks in lieu of the current model-based approach, a national inventory of downed dead wood C across the U.S. was compared to estimates calculated from models associated with the U.S.’s NGHGI and used in the USDA Forest Service, Forest Inventory and Analysis program. The model-based population estimate of C stocks for CWD (i.e., pieces and slash piles) in the conterminous U.S. was 9 percent (145.1 Tg) greater than the field-based estimate. The relatively small absolute difference was driven by contrasting results for each CWD component. The model-based population estimate of C stocks from CWD pieces was 17 percent (230.3 Tg) greater than the field-based estimate, while the model-based estimate of C stocks from CWD slash piles was 27 percent (85.2 Tg) smaller than the field-based estimate. In general, models overestimated the C density per-unit-area from slash piles early in stand development and underestimated the C density from CWD pieces in young stands. This resulted in significant differences in CWD C stocks by region and ownership. The disparity in estimates across spatial scales illustrates the complexity in estimating CWD C in a NGHGI. Based on the results of this study, it is suggested that the U.S. adopt field-based estimates of CWD C stocks as a component of its NGHGI to both reduce the uncertainty within the inventory and improve the sensitivity to potential management and climate change events.     

Carbon and nitrogen storage in an age-sequence of <Emphasis Type="Italic">Pinus densiflora</Emphasis> stands in Korea

The carbon (C) and nitrogen (N) storage capabilities of Pinus densiflora in six different stand ages (10, 27, 30, 32, 44, and 71 years old) were investigated in Korea. Thirty sample trees were destructively harvested and 12 were excavated. Samples from the above and belowground tree components, coarse woody debris (CWD), forest floor, and mineral soil (0–30 cm) were collected. Tree biomass was highest in the 71-year-old stand (202.8 t ha⁻¹) and lowest in the 10-year-old stand (18.4 t ha⁻¹). C and N storage in the mineral soil was higher in the 71-year-old stand than in the other stands, mainly due to higher soil C and N concentrations. Consequently, the total ecosystem C and N storage (tree+forest floor+CWD+soil) was positively correlated with stand age: increasing from a minimum in the 10 year old stand (18.8 t C ha⁻¹ and 1.3 t N ha⁻¹) to a maximum in the 71-year-old stand (201.4 t C ha⁻¹ and 8.5 t N ha⁻¹). The total ecosystem C storage showed a similar sigmoidal pattern to that of tree C storage as a function of the age-sequence, while N storage in the CWD, forest floor and mineral soil showed no significant temporal trends. Our results provide important insights that will increase our understanding of C and N storage in P. densiflora stands and our ability to predict changes according to stand age in the region.     

Biomass and Carbon Storage in an Age-Sequence of Korean Pine (<Emphasis Type="Italic">Pinus koraiensis</Emphasis>) Plantation Forests in Central Korea

This study examined the biomass and carbon pools of the main ecosystem components in an age sequence of five Korean pine plantation forest stands in central Korea. The C contents in the tree and ground vegetation biomass, coarse woody debris, forest floor, and mineral soil were estimated by analyzing the C concentration of each component. The aboveground and total tree biomass increased with increasing stand age. The highest C concentration across this chronosequence was found in the tree branch while the lowest C concentration was found in the ground vegetation. The observed C contents for tree components, ground vegetation, and coarse woody debris were generally lower than the predicted C contents estimated from a biomass C factor of 0.5. Forest floor C content was age-independent. Total mineral soil C content appeared to decline initially after establishing Korean pine plantations and recover by the stand age of 35 years. Although aboveground tree biomass C content showed considerable accumulation with increasing age, the relative contribution of below ground C to total ecosystem C content varied substantially. These results suggest that successional development as temporal factor has a key role in estimating the C storage in Korean pine plantation forests.     

Dynamics of ectomycorrhizae in Abies amabilis stands: The role of Cenococcum graniforme

The growth and development of the predominant mycorrhizal fungus infecting the root systems of subalpine Pacific silver fir was examined seasonally in 23 and 180 yr old stands. All data was obtained by sorting roots from intact soil cores separated into forest floor and mineral soil horizons.
The predominant mycorrhizal fungus infecting the root systems of 23 and 180 yr old Pacific silver fir was Cenococcum graniforme. C. graniforme comprised 36–97% and 40–96% of the total mycorrhizal root tips in the soil profile in the young and old stands, respectively. C. graniforme root biomass reached a maximum in autumn in the young stand, and in winter in the old. Dual mycorrhizal associations were commonly observed on the same root tip during the spring and autumn periods of root elongation in both stands. Over 80% of the C. graniforme roots were located in the forest floor and A-horizon throughout the study in both stands, Sclerotia were predominantly located in the A-horizon (38-70%) in both stands.     

Preliminary Studies on the Litterfall and Coarse Woody Debris in Mid-Mountain Humid Evergreen Broad-Leaved Forest in Ailao Mountains

The composition and amount of the litterfall and coarse woody debris (CWD), their time and space distribution and the element return were studied in mid-mountain humid ev-ergreen broad-leaved forest in Ailao Mountain in Yunnan, China. The average litterfall (leaves, wood (< 2.5 cm diameter), flower, fruit and mixed matter) was (6.77± 1.43) t/(hm2 · a) while the large wood litterfall () 2.5 cm diameter) was (0.45±0.18) t/(hm2 · a). There were two marked peaks of annual litterfalh the main one from April to May and the second one from October to November. The standing crop of CWD in the forest was 98.46 t/hm2, in which logs made up to 85.8% of the total. As the CWD was not well-distributed in the forest, it increased the diversities of structure and site in the forest ecosystem. The total storage of C, N, P, K, Ca, Mg, Mn, A1 and Fe in the CWD was 48699 t/hm2, but return of elements to the forest ground in the litterfall only made up 7.77% of the nutrient storage of the CWD.     

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.     

Dead wood biomass and turnover time,measured by radiocarbon,along a subalpine elevation gradient

Dead wood biomass can be a substantial fraction of stored carbon in forest ecosystems, and coarse woody debris (CWD) decay rates may be sensitive to climate warming. We used an elevation gradient in Colorado Rocky Mountain subalpine forest to examine climate and species effects on dead wood biomass, and on CWD decay rate. Using a new radiocarbon approach, we determined that the turnover time of lodgepole pine CWD (340±130 years) was roughly half as long in a site with 2.5–3°C warmer air temperature, as that of pine (630±400 years) or Engelmann spruce CWD (800±960 and 650±410 years) in cooler sites. Across all sites and both species, CWD age ranged from 2 to 600 years, and turnover time was 580±180 years. Total standing and fallen dead wood biomass ranged from 4.7±0.2 to 54±1 Mg ha^–1, and from 2.8 to 60% of aboveground live tree biomass. Dead wood biomass increased 75 kg ha^–1 per meter gain in elevation and decreased 13 Mg ha^–1 for every degree C increase in mean air temperature. Differences in biomass and decay rates along the elevation gradient suggest that climate warming will lead to a loss of dead wood carbon from subalpine forest.Electronic Supplementary Material Supplementary material is available for this article at     

Common Factors Drive Disease and Coarse Woody Debris Dynamics in Forests Impacted by Sudden Oak Death

Disease ecology has made important steps in describing how epidemiological processes control the impact of pathogens on populations and communities but fewer field or theoretical studies address disease effects at the ecosystem level. We demonstrate that the same epidemiological mechanisms drive disease intensity and coarse woody debris (CWD) dynamics in natural forest ecosystems impacted by an emerging disease. Sudden oak death (causal agent, Phytophthora ramorum) has caused mortality of tanoak (Notholithocarpus densiflorus) on a spatial scale and rate comparable to other major North American forest diseases caused by invasive pathogens. In pathogen invaded stands, mean CWD masses were 22.4 Mg ha⁻¹ of standing dead tanoak (snags) and 11.5 Mg ha⁻¹ in logs compared to 0.27 and 1.16 Mg ha⁻¹ of snags and logs in an uninvaded stand. Within invaded stands variation in CWD mass and accumulation rates were largely driven by the distribution of pre-disease tanoak biomass and the densities of infected tanoak and California bay laurel (Umbellularia californica) which jointly determine P. ramorum sporulation and disease emergence rates. In a narrow range of community and host characteristics sudden oak death can result in woody debris dynamics similar to discrete disturbances such as fire and forest harvest but it is more common to have lower maximum amounts with slower rates of accumulation than these better studied disturbances. Our results indicate that models of CWD dynamics need to integrate epidemiological processes to predict realistic ecosystem impacts and lead to management applications for forest pathogens.     

腐烂等级和径级对天宝岩长苞铁杉林木质残体理化性质的影响

木质残体是森林生态系统的重要组成部分,其理化性质影响木质残体的分解.本研究以集中分布于天宝岩国家级自然保护区的长苞铁杉(Tsuga longibracteata)林木质残体为对象,将4个不同类型林分的木质残体划分为5个腐烂等级和4个径级,研究林分类型、腐烂等级、径级及其交互作用对木质残体理化性质的影响.结果 表明:从物...     

Coarse Woody Debris following Fire and Logging in Wyoming Lodgepole Pine Forests

The accumulation and decomposition of coarse woody debris (CWD) are processes that affect habitat, soil structure and organic matter inputs, and energy and nutrient flows in forest ecosystems. Natural disturbances such as fires typically produce large quantities of CWD as trees fall and break, whereas human disturbances such as timber harvesting remove much of the CWD. Our objective was to compare the amount of CWD removed and left behind after clear-cutting to the amount consumed and left behind after natural fires in Rocky Mountain lodgepole pine. The masses of fallen logs, dead-standing trees, stumps, and root crowns more than 7.5 cm in diameter were estimated in clear-cut and intact lodgepole pine forests in Wyoming and compared to estimates made in burned and unburned stands in Yellowstone National Park (YNP), where no timber harvesting has occurred. Estimates of downed CWD consumed or converted to charcoal during an intense crown fire were also made in YNP. No significant differences in biomass of downed CWD more than 7.5 cm in diameter were detected between burned stands and those following a single clear-cut. However, the total mass of downed CWD plus the mass of snags that will become CWD was nearly twice as high in burned stands than in clear-cuts. In YNP, approximately 8% of the downed CWD was consumed by fire and an additional 8% was converted to charcoal, for an estimated loss of about 16%. In contrast, approximately four times more wood (70%) was removed by clear-cutting. Considering all CWD more than 7.5 cm in diameter that was either still present in the stand or removed by harvesting, slash treatment, or burning, clear-cut stands lost an average of 80 Mg ha⁻¹ whereas stands that burned gained an average of 95 Mg ha⁻¹. Some CWD remains as slash and stumps left behind after harvesting, but stands subjected to repeated harvesting will have forest floor and surface soil characteristics that are beyond the historic range of variability of naturally developing stands. Received 16 November 1999; Accepted 31 May 2000.     

rDNA internal transcribed spacer sequence analysis of Craterellus tubaeformis from North America and Europe

The basidiomycete Craterellus tubaeformis (Fries) Quélet is an important widespread ectomycorrhizal basidiomycete found in the Northern Hemisphere. In this study, 12 samples of C. tubaeformis from North America and Europe were analyzed using internal transcribed spacer (ITS) sequences to reveal the correlation between ITS genotypes and geographic locations and to provide molecular evidence for the identification of C. tubaeformis from different habitats in North America and Europe. The analyses identified abundant sequence variations within C. tubaeformis. The length of the ITS region varied from 571 to 640 bp. The proportion of variable sites was 17.6%, and the proportion of parsimony information sites was 16.7%. Phylogenetic analysis showed some correlations between the ITS genotypes and geographic locations of C. tubaeformis; however, some discrepancies between geographical location and affinity were also found. The results indicated that C. tubaeformis from different habitats in North America and Europe underwent genetic drifting and evolved into 2 different species. nrDNA ITS could be a good markers for distinguishing among C. tubaeformis from different habitats, but rational affinity should be determined by associating the available ITS data with other information sources.     

The Imprint of Land-use History: Patterns of Carbon and Nitrogen in Downed Woody Debris at the Harvard Forest

Few data sets have characterized carbon (C) and nitrogen (N) pools in woody debris at sites where other aspects of C and N cycling are studied and histories of land use and disturbance are well documented. We quantified pools of mass, C, and N in fine and coarse woody debris (CWD) in two contrasting stands: a 73-year-old red pine plantation on abandoned agricultural land and a naturally regenerated deciduous forest that has experienced several disturbances in the past 150 years. Masses of downed woody debris amounted to 40.0 Mg ha⁻¹ in the coniferous stand and 26.9 Mg ha⁻¹ in the deciduous forest (20.4 and 13.8 Mg C ha⁻¹, respectively). Concentrations of N were higher and C:N ratios were lower in the deciduous forest compared to the coniferous. Pools of N amounted to 146 kg N ha⁻¹ in the coniferous stand and 155 kg N ha⁻¹ in the deciduous forest; both are larger than previously published pools of N in woody debris of temperate forests. Woody detritus buried in O horizons was minimal in these forests, contrary to previous findings in forests of New England. Differences in the patterns of mass, C, and N in size and decay classes of woody debris were related to stand histories. In the naturally regenerated deciduous forest, detritus was distributed across all size categories, and most CWD mass and N was present in the most advanced decay stages. In the coniferous plantation, nearly all of the CWD mass was present in the smallest size class (less than 25 cm diameter), and a recognizable cohort of decayed stems was evident from the stem-exclusion phase of this even-aged stand. These results indicate that heterogeneities in site histories should be explicitly included when biogeochemical process models are used to scale C and N stocks in woody debris to landscapes and regions. Received 27 April 2001; accepted 4 January 2002.     

Saproxylic beetle diversity in a managed boreal forest: importance of stand characteristics and forestry conservation measures

Saproxylic beetles constitute a significant proportion of boreal forest biodiversity. However, the long history of timber production in Fennoscandia has significantly reduced the availability of dead wood and is considered a threat to the conservation of saproxylic beetle assemblages. Therefore, since the mid‐1990s dead wood retention in harvested stands has formed an integral part of silvicultural practices. However, the contribution of this biodiversity‐orientated management approach to conserving saproxylic beetle assemblages in boreal forest landscapes that include production forestry remains largely untested. We examined differences in resident saproxylic beetle assemblages among stands under different management in a boreal forest landscape in Central Sweden, and in particular stands managed according to new conservation‐orientated practices. We also investigated the relationship between beetle diversity and forest stand characteristics. Bark of coarse woody debris (CWD) was sieved for beetles in old managed stands, unmanaged nature reserves, and set‐aside areas, and clear‐cut stands harvested according to certification guidelines [new forestry (NF) clear‐cuts]. All stand types contributed significantly to the total diversity of beetles found. While stand size, position, and distance to nearest reserve were unimportant, both the quality and the quantity of CWD in stands contributed significantly to explaining beetle abundance and species richness. This extends the previous findings for red‐listed invertebrates, and shows that heterogeneous substrate quality and a range of management practices are necessary to maintain saproxylic beetle diversity in boreal forest landscapes that include production forestry. The unique abiotic conditions in combination with the abundant and varied CWD associated with NF clear‐cuts form an important component of forest stand heterogeneity for saproxylic beetles. It is thus essential that sufficient, diverse, CWD is retained in managed boreal landscapes to ensure the conservation of boreal saproxylic beetle assemblages.     

武夷山甜槠林粗死木质残体的贮量、动态及其功能评述

 本文对武夷山甜槠林76龄成熟林内粗死木质残体的贮量、增枯量和分解量等进行了研究,对不同林龄甜槠林粗死木质残体的贮量动态进行了对比分析,并初步评述了它们在森林生态系统养分循环中的作用。研究结果表明：(1)甜槠林成林粗死木质残体贮量为7.349t·hm-2,增枯量为1.425t·hm-2·a-1,分解量为0.512t·hm-2·a-1;(2)随着林龄增长,不同林龄甜槠林的粗死木质残体贮量呈“S”型动态模式,至58龄阶段达到最大值,其后渐趋稳定;(3)粗死木质残体是甜槠林生态系统中较为重要的组成部分,其各养分元素贮量占该系统生物量分室总贮量的0.09%～1.91%,由增枯量实现的各养分元素归还量占养分元素归还总量的l.94%～4.48%。     

小兴安岭谷地云冷杉林粗木质残体碳密度特征

以小兴安岭谷地云冷杉林9.12 hm~2固定样地为研究对象,分析粗木质残体(CWD)碳密度的基础特征,揭示其与林分因子和物种多样性的关系。结果表明:(1)谷地云冷杉林CWD碳密度为13.25 t C/hm~2,其中云杉(Picea spp.)、冷杉(Abies nephrolepis)、兴安落叶松(Larix gmelinii)和未知种的CWD碳密度分别为3.59、2.61、3.06和2.85 t C/hm~2。(2)不同腐烂等级下CWD碳密度呈近正态分布,多集中在Ⅱ和Ⅲ等级,分别占总量的42.7%和35.4%。不同径级的CWD碳密度也呈近正态分布,主要分布在30—40 cm和40—50 cm径级上。干中折断、拔根倒、枯立木和干基折断为谷地云冷杉林CWD碳密度的主要存在方式。腐烂等级为Ⅰ和Ⅴ的CWD中,拔根倒的碳密度最高,其他腐烂等级中均为干中折断的碳密度最高。(3)CWD碳密度表现出较强的空间异质性,其随着林分平均胸径、最大胸径和胸高断面积的增加而下降,呈显著负相关关系(P0.05);而与林分密度、多样性指数和均匀度指数均无显著相关性(P0.05)。