Coarse woody debris in Australian forest ecosystems: A review

Abstract Coarse woody debris (CWD) is the standing and fallen dead wood in a forest and serves an important role in ecosystem functioning. There have been several studies that include estimates of CWD in Australian forests but little synthesis of these results. This paper presents findings from a literature review of CWD and fine litter quantities. Estimates of forest‐floor CWD, snags and litter from the literature are presented for woodland, rainforest, open forest and tall open forest, pine plantation and native hardwood plantation. Mean mass of forest floor CWD in Australian native forests ranged from 19 t ha^?1 in woodland to 134 t ha^?1 in tall open forest. These values were generally within the range of those observed for similar ecosystems in other parts of the world. Quantities in tall open forests were found to be considerably higher than those observed for hardwood forests in North America, and more similar to the amounts reported for coniferous forests with large sized trees on the west coast of the USA and Canada. Mean proportion of total above‐ground biomass as forest floor CWD was approximately 18% in open forests, 16% in tall open forests, 13% in rainforests, and 4% in eucalypt plantations. CWD can be high in exotic pine plantations when there are considerable quantities of residue from previous native forest stands. Mean snag biomass in Australian forests was generally lower than the US mean for snags in conifer forests and higher than hardwood forest. These results are of value for studies of carbon and nutrient stocks and dynamics, habitat values and fire hazards.     

森林粗死木质残体的概念及其分类

森林粗死木残体 (Coarse woody debris,CWD)在不同的文献中有不同的定义 ,没有通用而确切的概念用来描述 CWD,对研究结果的比较造成了很大障碍。 2 0世纪 90年代以来 ,随着景观生态学的发展 ,以及对 CWD生态功能的深入研究 ,国外的森林管理和研究机构 (例如 USDA Forest Service和 L TER)为了把 CWD放在区域以及景观尺度上进行比较 ,对 CWD的概念等进行了统一 ,将其直径标准由原来的≥ 2 .5 cm调整到≥ 10 cm,但是我国在此方面还没有与国际接轨 ,仍采用旧标准 (≥ 2 .5 cm ) ,这样的研究结果难于和国外进行比较 ,不利于我国 CWD的长期深入研究。另外 ,有关 CWD的分类一直以来也没有形成一个完整的分类系统 ,我国也缺少 CWD分类方法的介绍。鉴于以上情况 ,综合国内外近年来在 CWD方面的研究动态 ,综述了 CWD的概念和分类情况 ,并初步提出较综合的 CWD概念及其分类系统 ,以供相关研究者讨论和参考 ,为我国的 CWD研究起到推动作用     

温带森林生态系统粗死木质物动态研究——以中美两个温带天然林生态系统为例

通过对我国长白山自然保护区红松针阔混交林和美国Andrews试验林异叶铁杉林的林木死亡量、粗死木质物(CWD)贮量、分解速率和它们在生态系统养分循环等方面动态研究表明,CWD是温带天然林生态系统的重要组成部分,它们在生态系统功能方面的重要性,因森林类型的不同而不尽相同,CWD在针叶林中比针阔混交林中更为重要。CWD在生态系统养分循环中的一个重要作用,很可能在于系统遭受重大外界扰动后,起到贮藏养分,增加系统稳定性的作用。未来全球森林凋落物C贮量估测时,应该包括CWD,否则将低估全球森林凋落物C贮量2.0—16×10~(13)kg,系统相对误差达2—10％。     

Coarse woody debris mass and nutrients in forest ecosystems of Korea

Coarse woody debris (CWD) is an essential component of forests. However, quantification of both the mass and nutrient content of CWD within a given environment tends to be a fairly labor-intensive proposition that requires long-term studies to be conducted for viable data to be obtained. As a result, various aspects of CWD in forest ecosystems remain somewhat poorly understood. In this review, we have compiled all available estimates of CWD mass and nutrients from both coniferous and deciduous forests in Korea. The CWD mass data varied substantially by forest type, age, location, and sampling time, ranging from 1.5 to 24.5 Mg ha⁻¹, and for the amount (kg ha⁻¹) of nutrients in the CWD, ranging from 3.5 to 23.6 for nitrogen (N), 0.8 to 4.7 for phosphorus (P), 3.9 to 13.3 for potassium (K), 25.9 to 30.9 for calcium (Ca), 1.4 to 4.2 for magnesium (Mg), and 0.1 to 0.6 for sodium (Na). The mass of CWD transferred from live trees to the forest floor ranged between 0.1 and 4.9 Mg ha⁻¹ year⁻¹, and these values were roughly equivalent to 26–42% of the annual litterfall inputs (2.5–10.8 Mg ha⁻¹ year⁻¹) for mixed Quercus spp. forests within the relevant region. Annual nutrients inputs (kg ha⁻¹ year⁻¹) through CWD decomposition were 0.7–1.6 for N, 0.04–0.3 for P, 0.3–1.0 for K, 1.7–3.1 for Ca, and 0.1–0.3 for Mg. Consequently, these results revealed that the ecological value of CWD for C and nutrient cycling was relatively insignificant. However, only a limited number of studies have been conducted on CWD in different coniferous or mixed deciduous forests in the region. As a direct result of this paucity of data, further long-term studies on CWD mass and nutrients in a variety of forest types are required in order to be able to evaluate accurately the ecological value of CWD on biodiversity and physical properties in Korean forest ecosystems.     

森林生态系统粗死木质残体碳储量研究进展

粗死木质残体(CWD)是森林生态系统重要的结构性与功能性单元,作为连接植被碳库与土壤碳库的关键纽带,对全球森林生态系统碳循环发挥着重要而独特的作用,越来越多的学者开始关注CWD碳储量相关研究。系统阐述了国内外CWD碳储量研究的发展历程、研究范围与基本特征等内容,总结概括了CWD体积测算、CWD碳浓度估算等碳计量相关方法的研究进展。通过梳理发现:国内外学者对CWD碳储量的研究仍处于初级阶段,主要集中于探讨不同树种、不同林龄、不同腐解等级、不同海拔、不同存在形式的森林CWD碳储量分布特征,而较少关注CWD碳库对土壤碳库和植被碳库的作用机制以及对未来气候变化的响应和反馈机制;CWD碳计量方法较为单一,普遍采用的是传统的"生物量-碳浓度法",而运用机器学习算法对CWD碳储量进行估算的研究尚不多见。此外,相对国外研究而言,国内研究主要局限于小尺度范围。文章据此提出未来CWD碳储量研究的发展方向:(1)拓展研究尺度,建立CWD碳储量长期观测体系;(2)深入开展不同森林生态系统CWD碳储量对气候变化的响应机制研究;(3)探索更加多元化的CWD碳储量计量方法;(4)深入探讨CWD碳库对土壤碳库与植被碳...     

鼎湖山黄果厚壳桂粗死木质残体的分解

通过建立时间序列法、测定粗死木质残体的密度变化,研究鼎湖山黄果厚壳桂粗死木质残体三个直径(5~10cm、10~20cm和20~30cm)的分解过程,探讨粗死木分解过程中C、N元素及其C/N比值与分解速率的关系。结果表明粗死木质残体的分解常数K值随直径的增加从0.2225a-1呈指数降低到0.1257a-1,由粗死木质残体在分解过程中密度变化得出三个直径从小到大分解95%所需的时间分别为13a、19a和24a;黄果厚壳桂粗死木质残体在分解过程中不存在时滞效应,其树皮和心材的分解速度也相近,用单因素数指数方程能准确反映黄果厚壳桂的分解过程;与高纬度地区比较,鼎湖山黄果厚壳桂粗死木残体的分解速率常数K值显著高于前者。还就粗死木残体基质组成和性质、气候与环境条件、生物等因素对粗死木分解速率的影响进行了详细的讨论。     

Functional traits predict drought performance and distribution of Mediterranean woody species

Water availability is one of the key environmental factors that affect plant establishment and distribution. In many regions water availability will decline with climate change, exposing small seedlings to a greater likelihood of drought. In this study, 17 leaves, stem, root, and whole-plant traits of ten woody Mediterranean species were measured under favourable growing conditions and seedling drought survival was evaluated during a simulated dry-down episode. The aims of this study were: i) to assess drought survival of different species, ii) to analyse which functional traits predict drought survival time, and iii) to explain species distribution in the field, based on species drought survival and drought strategies. Drought survival time varied ten-fold across species, from 19 to 192 days. Across species, drought survival was positively related to the rooting depth per leaf area, i.e., the ability to acquire water from deeper soil layers while reducing transpiring leaf area. Drought survival time was negatively related to species ability to grow quickly, as indicated by high relative growth and net assimilation rates. Drought survival also explained species distribution in the field. It was found that species were sorted along a continuum, ranging between two contrasting species functional extremes based on functional traits and drought performance. One extreme consisted of acquisitive fast-growing deciduous species, with thin, soft metabolically active leaves, with high resource use and vulnerability to drought. The opposite extreme consisted of conservative slow-growing evergreen species with sclerophyllous leaves, deep roots, a low transpiring area, and low water use, resulting in high drought survival and drought tolerance. The results show that these drought strategies shape species distribution in this Mediterranean area.     

Plant persistence traits in fire-prone ecosystems of the Mediterranean basin: a phylogenetic approach

The two main fire response traits found in the Mediterranean basin are the resprouting capacity (R) and the propagule-persistence capacity (P). Previous studies suggested that these two traits might be correlated. In this paper we first test whether R and P have evolved independently. Then, we ask if the correlation occurs because (a) one trait is not the target of selection but it is genetically linked to the other trait which is the one under selection pressure (indirect selection), or (b) because different evolutionary responses to the same selective pressure are acting in parallel on populations at different genetic starting points (parallel selection). Finally, we test to what extent resprouting is associated with some vegetative and reproductive traits.
To answer these questions we used a traits database for the eastern Iberian Peninsula and we assembled the phylogenetic tree on the basis of published information. The results indicate that the two traits are negatively associated and support the parallel selection scenario in which changes in R precedes changes in P. The phylogenetic–informed associations of resprouting with other traits (plant height, age at maturity) support the existence of allocation tradeoffs.
The results are consistent with the biogeographical history of the Mediterranean basin flora where most of lineages already resprouted to persist after a disturbance during the Tertiary, thus making it improbable that an additional costly persistence strategy would evolve under the Quaternary climatic conditions.     

Fungal wood decomposer activities influence community structures of myxomycetes and bryophytes on coarse woody debris

Dead wood is an important habitat for forest organisms, and wood decay fungi are the principal agents determining the dead wood properties that influence the communities of organisms inhabiting dead wood. In this study, we investigated the effects of wood decomposer fungi on the communities of myxomycetes and bryophytes inhabiting decayed logs. On 196 pine logs, 72 species of fungi, 34 species and seven varieties of myxomycetes, and 16 species of bryophytes were identified. Although white rot was the dominant decay type in sapwood and heartwood, brown and soft rots were also prevalent, particularly in sapwood. Moreover, white rot and soft rot were positively and brown rot negatively correlated with wood pH. Ordination analyses clearly showed a succession of cryptogam species during log decomposition and showed significant correlations of communities with the pH, water content, and decay type of wood. These analyses indicate that fungal wood decomposer activities strongly influence the cryptogam communities on dead wood.     

Variation in morphological and chemical traits of Mediterranean tree roots: linkage with leaf traits and soil conditions

Plant and Soil - Na+/H+ antiporter (NHX1) was reported to be induced by NaCl in plants and NaCl can alleviate the toxic effect in plants caused by cadmium (Cd). However, it is unknown whether the...     

Effect of decomposing post-fire coarse woody debris on soil fertility and nutrient availability in a Mediterranean ecosystem

Post-fire coarse woody debris can represent a valuable nutrient reservoir for a regenerating ecosystem, helping to prevent soil fertility losses after a wildfire. However, there is scarce information on its effect on soil nutrient cycling and availability. We established three study sites along an altitudinal gradient in a burnt pine forest (SE Spain). At each site we determined: (1) decomposition rates and nutrient dynamics in charred logs left on the ground, 2 and 4 years after the fire, and (2) available nutrients in the soil and in the microbial fraction below charred logs and in bare soil areas. Despite the relatively slow decay rates in this Mediterranean climate (ca. 10 % of dry weight lost after 4 years), N and P were progressively released by logs, accounting for ca. 40 and 65 % of the initial content respectively after 4 years. This implies that the total aboveground biomass of the burnt forest released around 20 kg ha^?1 of N and 2 kg ha^?1 of P during this period. The presence of post fire coarse woody debris consistently increased soil organic matter by around 18 %, total C and N by 42 and 26 %, respectively, dissolved organic C and N by 47 %, available inorganic P by 68 %, and microbial biomass and nitrogen by some 36 and 48 %, respectively. By contrast, soil bulk density decreased by ca. 18 % under logs compared to bare areas. Thus, the fire-killed wood was useful in the recovery of soil fertility and nutrient availability. Leaving the post-fire woody debris on site can enhance the biogeochemical sustainability, microbiological processes and soil ecological functioning. The detrimental effect of post-fire salvage logging on soil fertility should be therefore considered when making management decisions.     

Interactive effects of wood decomposer fungal activities and bryophytes on spruce seedling regeneration on coarse woody debris

Decaying logs are important seedbeds in boreal and subalpine forests. However, biotic and abiotic factors and their interactions related to seedling colonization patterns on logs remain unclear. In the present study, we evaluated the influence of bryophyte communities, wood decay type (white-, brown-, and soft-rot) owing to decomposer fungal activities, and environmental abiotic factors on seedling establishment in an old-growth subalpine coniferous forest in Japan. Among the tree species recorded on the conifer logs, Picea jezoensis var. hondoensis was the most dominant. Log surfaces were covered with distinctive patches of liverwort Scapania bolanderi and moss Pleurozium schreberi (approximately 33% cover for each). Redundancy analysis showed that brown-rot in sapwood significantly affects the bryophyte and seedling community on the logs. Generalized linear models suggested that the total bryophyte cover, Scapania cover, and white-rot in heartwood positively associate with Picea seedling density, whereas Pleurozium cover and basal area of adjacent Picea adults negatively associate with Picea seedling density. Results of structural equation modeling suggested that the brown-rot of sapwood positively associates with Scapania cover that has a positive effect on Picea seedling density. Furthermore, brown-rot of sapwood inhibited the Pleurozium cover, thus contributing to the Scapania dominance on the logs. These results suggest that fungal wood decomposer activities affect colonization of Picea seedlings in an indirect way via structuring bryophyte community on the logs.     

Ratite and ungulate preferences for woody New Zealand plants: influence of chemical and physical traits

Ratites (ostriches Struthio camelus) and ungulates (red deer Cervus elaphus scoticus and goats Capra hircus) were presented with 14 indigenous shrubs in cafeteria-style trials. The shrubs represented the spectrum of woody plant architecture, ranging from broadleaved monopodial species through to small-leaved highly branched divaricates. Trials were stopped when almost all shoots of the plant expected to be most preferred had been consumed. There were considerable differences between the herbivores in their selection of certain plant species. Aristotelia fruticosa was avoided by deer, neutrally selected by goats, and preferred by ostriches. All herbivores strongly avoided two species, Pseudopanax crassifolius and Coprosma rugosa. Analysis of relative offtake (proportion of biomass consumed from each species, relative to total biomass consumed) showed that all three herbivores ate less of species with small leaves. Consumption by all herbivores was reduced by structural plant traits (i.e. divarication and related attributes) more than by chemical plant traits. The immediate impact of browsing on the plants, measured as the rank of proportion of shoots eaten, was broadly similar across the herbivores. The broadleaved species (e.g. Myrsine australis, Aristotelia serrata) experienced the greatest browsing, while divaricate (e.g. Coprosma rugosa) and conifer species (e.g. Podocarpus hallii) were generally least browsed. Although cafeteria-style experiments have limitations, our results for deer broadly correspond to those of field-based diet preference studies.     

Coarse woody debris in virgin and managed forest

This study treats dead trees and their remnants in the managed and virgin forest of Rajhenavski Rog, Slovenia, at a location of Omphalodo-Fagetum omphalodetosum plant community. The study plots were selected in four forest cycle developmental phases (optimal, mixed, regeneration and juvenile phase) of both managed and virgin forest. The quantity (volume and dry matter) and the structure of coarse woody debris (CWD) were compared between the selected plots within the particular type of the forest, and between the virgin and the managed forest. Belowground CWD was quantified by modeling the tree's biomass and decaying processes of the trees. The results show significant differences in CWD between the virgin forest developmental phases. The highest concentration of CWD in the virgin forest was found in the regeneration phase (626.0 m³/ha and 179.3 t_dry matter/ha), while the juvenile phase (248.3 m³/ha and 40.2 t_dry matter/ha) has the smallest amount of CWD. Managed forest has very evenly distribution of CWD between developmental phases and it ranges from 41.0 m³/ha and 49.0 t_dry matter/ha in the mixed developmental phase to 67.0 m³/ha and 56.2 t_dry matter/ha in the juvenile phase. The main reasons for such a large differences are forest management measures (e.g. wood extraction, short rotation time, reduction of natural tree mortality), which decrease quantity, distribution and size of CWD. It was identified that forest management causes reduction and homogenization of CWD on our study plots, which can trigger degradation processes (e.g. soil erosion, reduction of site productivity, reduction of habitats). Tree heights curves show significant differences in maximum tree's height between the virgin and the managed forest. Maximum tree's height is lower in the managed forest which may indicate the reduction of forest productivity due to reduction of CWD. Study has shown some positive effects of forest management on accumulation of underground CWD in the managed forest (from 40.0 t_dry matter/ha to 48.2 t_dry matter/ha), which significantly exceeds underground CWD in the virgin forest (from 2.0 t_dry matter/ha to 22.8 t_dry matter/ha).     

Variation in wood anatomical traits of Pinus sylvestris L. between Spanish regions of provenance

The Spanish populations of Pinus sylvestris L. occupy differentiated sites and must therefore include structural variations to cope with varied climate conditions. This study compares wood anatomical traits of P. sylvestris from ten Spanish regions of provenance with contrasting climates, taking into account the effects of region of provenance and tree nested within provenance on variation in wood biometry. In general, the effect of both sources of variation (provenance and tree) on wood biometry was highly significant. Most of the anatomical variations observed were intra-populational (at the tree level), although variation explained by provenance was high for some parameters (e.g., ray frequency and ray parenchyma cell frequency), suggesting high environmental influence. Trees in the driest region, growing in a Mediterranean phytoclimate, were characterized by large tracheid lumens, suggesting more efficient water conduction. They also had thick cell walls, which would reduce the risk of cavitation caused by high implosion stress during periods of drought, as well as a high ray tracheid frequency, implying greater water storage capacity in the sapwood. The population with greatest growth, located in an oroboreal phytoclimate, was characterized by large bordered pits and long tracheids, which would reduce resistivity in water transport. At higher altitudes, tracheid lumen diameter and resin canal diameter tended to be smaller, and intertracheid wall strength was greater. Results are discussed in relation to adaptation of the species to growth demands and frost.     

Effects of forest dieback on wood decay,saproxylic communities,and spruce seedling regeneration on coarse woody debris

Picea is one of the most dominant conifer genera in the Northern Hemisphere and includes species which require coarse woody debris (CWD) as a seedbed for regeneration. To understand the future of forest distribution under global climate change, it is important to investigate regeneration mechanisms in Picea forests on the borders of its distribution. In the present study, we evaluated the biotic factors affecting the establishment of Picea jezoensis var. hondoensis seedlings on CWD in one of its southernmost populations in central Japan, where there is dieback of Picea forest. Amplicon sequencing of the fungal ITS1 region of rDNA obtained from wood samples showed that forest dieback increased the frequency of brown rot fungi in CWD. The frequency of brown-rotted wood, in which wood holocellulose is decayed, increased with dieback intensity. The domination of brown-rotted wood in dieback forests was negatively associated with bryophyte cover which was positively associated with Picea seedling density. Forest dieback itself also had other strong negative effects on bryophytes. Thus, linkages between dead wood and spruce seedlings via bryophytes had collapsed after the dieback event, which may partly be a reason that the spruce forest shifted to and is staying as open grassland.     

Coordination of foliar and wood anatomical traits contributes to tropical tree distributions and productivity along the Malay-Thai Peninsula

Drought is a critical factor in plant species distributions. Much research points to its relevance even in moist tropical regions. Recent studies have begun to elucidate mechanisms underlying the distributions of tropical tree species with respect to drought; however, how such desiccation tolerance mechanisms correspond with the coordination of hydraulic and photosynthetic traits in determining species distributions with respect to rainfall seasonality deserves attention. In the present study, we used a common garden approach to quantify inherent differences in wood anatomical and foliar physiological traits in 21 tropical tree species with either widespread (occupying both seasonal and aseasonal climates) or southern (restricted to aseasonal forests) distributions with respect to rainfall seasonality. Use of congeneric species pairs and phylogenetically independent contrast analyses allowed examination of this question in a phylogenetic framework. Widespread species opted for wood traits that provide biomechanical support and prevent xylem cavitation and showed associated reductions in canopy productivity and consequently growth rates compared with southern species. These data support the hypothesis that species having broader distributions with respect to climatic variability will be characterized by traits conducive to abiotic stress tolerance. This study highlights the importance of the well-established performance vs. stress tolerance trade-off as a contributor to species distributions at larger scales.