On the Relationships between Ground-dwelling Spider (Araneae) Assemblages and Dead Wood in a Northern Sugar Maple Forest

Downed woody material (fallen logs) offers ground-dwelling spiders (Araneae) ideal sites for nesting and foraging, but little is known about what characteristics of dead wood influence spider assemblages. In a maple forest of Forillon National Park, in eastern Québec (Canada), spider assemblages on, adjacent to, and away from fallen logs were compared. We also tested how log type (coniferous vs. deciduous) and decomposition stage influenced spider assemblages. Sampling was done for an intensive four-week period using both litter samples and pitfall traps. A total of 5613 spiders representing 83 species from 16 families was collected. Spiders were affected by the presence of logs, as both species diversity and total number of individuals collected were significantly higher on the log surface compared to the forest floor. Ordination analysis revealed a distinct compositional difference between the spider fauna found on the wood surface compared to the forest floor. Wood type and decomposition stage had few significant effects on spider assemblages, except that less decayed logs supported higher spider diversity than logs in advanced stages of decay. Dead wood is clearly important for generalist predators such as spiders, further supporting the conservation importance of fallen logs in northern forest ecosystems.     

Contribution of Dead Wood to Biomass and Carbon Stocks in the Caribbean: St. John, U.S. Virgin Islands

Dead wood is a substantial carbon stock in terrestrial forest ecosystems and hence a critical component of global carbon cycles. Given the limited amounts of dead wood biomass and carbon stock information for Caribbean forests, our objectives were to: (1) describe the relative contribution of down woody materials (DWM) to carbon stocks on the island of St. John; (2) compare these contributions among differing stand characteristics in subtropical moist and dry forests; and (3) compare down woody material carbon stocks on St. John to those observed in other tropical and temperate forests. Our results indicate that dead wood and litter comprise an average of 20 percent of total carbon stocks on St. John in both moist and dry forest life zones. Island-wide, dead wood biomass on the ground ranged from 4.55 to 28.11 Mg/ha. Coarse woody material biomass and carbon content were higher in moist forests than in dry forests. No other down woody material components differed between life zones or among vegetation categories ( P > 0.05). Live tree density was positively correlated with fine woody material and litter in the moist forest life zone ( R = 0.57 and 0.84, respectively) and snag basal area was positively correlated with total down woody material amounts ( R = 0.50) in dry forest. Our study indicates that DWM are important contributors to the total biomass and, therefore, carbon budgets in subtropical systems, and that contributions of DWM on St. John appear to be comparable to values given for similar dry forest systems.     

Litter Decomposition and Nutrient Release in a Tropical Seasonal Rain Forest of Xishuangbanna,Southwest China1

We studied litter decomposition and nutrient release in a tropical seasonal rain forest of Xishuangbanna, Southwest China. The monthly decay rates (k) of leaf litter ranged from 0.02 to 0.21/mo, and correlated with rainfall and soil moisture. Annual k values for leaf litter (1.79/yr) averaged 4.2 times of those for coarse wood (2.5–3.5 cm in diameter). The turnover coefficients of forest floor mass (annual litterfall input/mean floor mass) were: 4.11/yr for flowers and fruits, 2.07/yr for leaves, and 1.17/yr for fine wood (≤2 cm in diameter), with resident time decreasing from fine woods (0.85 yr) to leaves (0.48 yr) and to flower and fruits (0.24 yr). Nutrient residence times in the forest floor mass were ranked as: Ca (1.0 yr) > P (0.92 yr) > Mg (0.64 yr) > N (0.36 yr) > K (0.31 yr). Our data suggest that rates of litter decomposition and nutrient release in the seasonal rain forest of Xishuangbanna are slower than those in typical lowland rain forests, but similar to those in tropical semideciduous forests.     

Tropical Dry Forests of Venezuela: Characterization and Current Conservation Status1

Tropical dry forests are located predominantly in the northern portion of Venezuela, above 6°N. Although their potential extent covers ca 400,000 km² (44% of the land), they currently occupy about 10 percent of this area. The diversity and complexity of Venezuelan dry forests increases from north to south along a gradient of decreasing severity of the dry season. A typical dry forest in Venezuela presents ca 110–170 species of plants from ca 40 to 50 families within an area of approximately 10 ha. Species composition and forest structure, however, are dependent on local landscape conditions (e.g., soil type, topography), and nearby forest types can be very different. Our analysis of five dry forest variants showed a maximum family similarity of 67 percent, although most values fell in the 50–60 percent interval. They are currently considered as one of Venezuela's most threatened ecosystems, but only 5 percent of extant dry forests are included in protected areas; this represents 0.5 percent of their potential extent. It is fundamental to promote the creation of at least 3 or 4 more large protected areas (ca 5000 ha), with different climatic and orographic characteristics, in combination with the recovery of threatened species, the restoration of degraded systems, and the implementation of sustainable development projects. Their apparent high resilience suggests that with the proper management we can restore and maintain the integrity of Venezuelan dry forests.     

地形对小兴安岭阔叶红松(Pinus koraiensis)林粗木质残体分布的影响

以小兴安岭典型阔叶红松林大面积固定样地(9hm2)为对象,分析不同地形下粗木质残体(CWD)的数量、存在形式、腐烂程度,探讨其与主要地形因子的相互关系.随着坡位的上升,CWD的密度和胸高断面积逐渐增加;从阴坡、半阴、半阳到阳坡,CWD的密度、胸高断面积和体积都呈现递减的趋势;CWD的数量分布随着样方坡度的增加没有呈现出明显的趋势.对不同地形下CWD的分布进行x2检验,各地形因子对CWD密度分布均差异显著,山脊、阴坡和坡度16～25°分别是CWD易发生的地形.在不同的地形中,CWD主要以干基折断、干中折断和枯立木3种形式存在.从谷地到山脊以拔根倒存在的CWD密度、胸高断面积和体积呈逐渐减少的趋势,而干中折断、根桩、枯立木和干基折断的密度大体上表现出增加的趋势;拔根倒的密度随坡度的上升逐渐减少,而枯立木则增加;由阳坡到阴坡枯立木的密度逐渐减少.不同存在形式的倒木,其树倒方向与坡向和风向均没有显著的相关性(p>0.05).不同地形下的各腐烂等级的CWD大致呈正态分布,且主要分布在2、3腐烂等级上,说明阔叶红松林不同地形的CWD输入和输出相对稳定.     

Colonization of Submerged Twigs and Branches of Different Wood Genera by Aquatic Macroinvertebrates

Previous studies which investigated macroinvertebrate colonization of submerged wooden substrates in streams and lakes did not consider the wood species. In this study, the genus of randomly collected twigs and branches from two streams was determined microscopically using morphological and structural characteristics of the wood genera. The macroinvertebrate colonization of the wooden substrates was analysed with respect to the different kinds of the twigs and branches. Additionally, an exposition experiment was conducted with the most commonly found wood genera, alder (Alnus) and oak (Quercus), in two different states of decay (freshwood and conditioned wood). The colonization experiment stressed the results of the natural wood samplings that the wood genus plays only a minor role in the colonization by macroinvertebrates.     

Composition,Microdistribution and Food of the Macroinvertebrate Fauna Inhabiting Wood in Low‐Order Mountain Streams in Central Europe

The macroinvertebrate community inhabiting woody debris in low‐order mountain streams was investigated using hand collections and emergence traps. With respect to dry mass, Amphipoda, Plecoptera and Diptera are the most important taxa. From the gut content analyses it was found that the microhabitat is colonized by xylophagous species as well as taxa of other feeding types. Regarding the whole community, there is no correlation between the abundance of specimens and density of wood, tree species, bark cover, consistency class, and surface structure. However, single species do show preferences; surface structure is the most important factor determining community composition.     

Forest Development, Wood Jams, and Restoration of Floodplain Rivers in the Puget Lowland, Washington

Historically in Puget Lowland rivers, wood jams were integral to maintaining an anastomosing channel pattern and a dynamic channel–floodplain connection; they also created deep pools. In the late 1800s, wood was removed from most rivers, rivers were isolated from their floodplains, and riparian forests were cut down, limiting wood recruitment. An exception to this history is an 11-km-long reach of the Nisqually River, which has natural banks and channel pattern and a mature floodplain forest. We use field and archival data from the Nisqually River to explore questions relevant to restoring large rivers in the Pacific Northwest and other forested temperate regions. In particular, we focus on the relation between recovery of in-channel wood accumulations and valley bottom forest conditions and explore implications for river restoration strategies. We find that restoring large rivers depends on establishing riparian forests that can provide wood large enough to function as key pieces in jams. Although the frequency of large trees in the Nisqually valley bottom in 2000 is comparable with that of 1873 land surveys, many formerly more abundant Thuja plicata (western red cedar) were cut down in the late 1800s, and now hardwoods, including Populus trichocarpa (black cottonwood) and Acer macrophyllum (bigleaf maple), are also abundant. Pseudotsuga menziesii (Douglas fir) and fast-growing P. trichocarpa commonly form key pieces that stabilize jams, suggesting that reforested floodplains can develop naturally recruited wood jams within 50 to 100 years, faster than generally assumed. Based on the dynamic between riparian forests, wood recruitment, and wood jams in the Nisqually River, we propose a planning framework for restoring self-sustaining dynamic river morphology and habitat to forested floodplain rivers.     

Coarse woody debris in undisturbed and logged forests in the eastern Brazilian Amazon

Coarse woody debris (CWD) is an important component of the carbon cycle in tropical forests. We measured the volume and density of fallen CWD at two sites, Cauaxi and Tapajós in the Eastern Amazon. At both sites we studied undisturbed forests (UFs) and logged forests 1 year after harvest. Conventional logging (CL) and reduced impact logging (RIL) were used for management on areas where the geometric volumes of logs harvested was about 25–30 m³ ha^?1. Density for five classes of fallen CWD for large material (>10 cm diameter) ranged from 0.71 to 0.28 Mg m^?3 depending upon the degree of decomposition. Density of wood within large fallen logs varied with position relative to the ground and with distance from the center of the log. Densities for materials with diameters from 2 to 5 and 5 to 10 cm were 0.36 and 0.45 Mg m^?3, respectively. The average mass (±SE) of fallen CWD at Cauaxi was 55.2 (4.7), 74.7 (0.6), and 107.8 (10.5) Mg ha^?1 for duplicate UF, RIL, and CL sites, respectively. At Tapajós, the average mass of fallen CWD was 50.7 (1.1) Mg ha^?1 for UF and 76.2 (10.2) Mg ha^?1 for RIL for duplicate sites compared with 282 Mg ha^?1 for live aboveground biomass. Small‐ and medium‐sized material (<10 cm dia.) accounted for 8–18% of the total fallen CWD mass. The large amount of fallen CWD at these UF sites relative to standing aboveground biomass suggests either that the forests have recently been subjected to a pulse of high mortality or that they normally suffer a high mortality rate in the range of 0.03 per year. Accounting for background CWD in UF, CL management produced 2.7 times as much CWD as RIL management. Excess CWD at logging sites would generate a substantial CO₂ emission given the high rates of decay in moist tropical forests.     

喀斯特常绿落叶阔叶混交林粗木质残体的空间分布格局

粗木质残体(coarse woody debris,CWD)是森林生态系统中重要的结构性和功能性组成要素,是维护系统完整性和稳定性的关键。对CWD空间格局的研究将有助于深入探索种群格局的形成和森林生态系统的维持机制。采用g(r)函数对茂兰喀斯特常绿落叶阔叶混交林1.28 hm~2固定样地内不同径级、不同腐烂等级、不同存在形式的CWD的空间分布格局及空间关联性进行了研究。结果表明:1)在40 m的空间尺度内,CWD总体在0—12 m尺度上表现为集群分布,随着尺度的增加格局强度降低,趋于随机分布,剔除生境异质性后,格局尺度降低至7 m。2)CWD径级格局表现为:小径级中径级大径级。拔根倒和干中折断在整个研究尺度上为随机分布,其他不同径级、不同腐烂等级、不同存在形式的CWD均在小规模尺度(2—8 m)表现为集群分布,随着尺度的增加聚集强度急剧变小,趋于随机分布或均匀分布。3)除了干中折断与树段之间、大径级与小径级之间的CWD在空间上相互独立,其他不同径级、不同腐烂等级或不同存在形式的CWD之间均在小规模尺度(2—8 m)上表现为显著的正相关,随着尺度的增加空间关联性降低。喀斯特常绿落叶阔叶混交林CWD的分布格局可能是在小尺度内由密度制约、在大尺度内由生境过滤和个体自然衰老等生态学过程所形成,大径级对临近的小径级、先死亡对后死亡、站杆对倒下的个体具有一定的正向影响作用,在一定程度上揭示了该林型天然更新的作用和机制。     

Concept and Classification of Coarse Woody Debris in Forest Ecosystems

Coarse woody debris (CWD) is generally considered as dead woody materials in various stages of decomposition,including sound and rotting logs,snags,and large branches.CWD is an important functional and structural component of forested ecosystems and plays an important role in nutrient cycling,long-term carbon storage,tree regeneration,and maintenance of heterogeneous environmental and biological diversity.However,the definition and classification of CWD have been the subject of a long debate in forest ecology.CWD has not been precisely defined.Recently,with the rapid development of landscape ecology in CWD,the USDA Forest Service and the Long Term Ecological Research (LTER)have provided a standardized definition and classification for CWD,which makes data comparison in landscape scale possible.Important characteristics of their definition include:(1) a minimum diameter (or an equivalent crosssection) of CWD≥10 cm at the widest point (the woody debris with a diameter from 1 to 10 cm should be defined as fine woody debris,and the rest is litterfall);and (2) sound and rotting logs,snags,stumps,and large branches (located above the soil),and coarse root debris (larger than 1 cm in diameter).This classification has greatly facilitated CWD studies.Therefore,it has been widely applied in some countries (particularly in North America).However,this classification has long been a source of confusion for forest ecologists in China.Furthermore,different definitions and criteria are still adopted in individual studies,which makes the interpretation and generalization of their work difficult.This article reviewed recent progress in classifying CWD,with an emphasis on introducing the classification system of the USDA Forest Service and the LTER.It is expected that this review will help facilitate the development of standardized definition and classification suitable to forest ecosystems in China.     

Typhoon Disturbance and Stand-level Damage Patterns at a Subtropical Forest in Taiwan1

We examined the typhoon wind disturbance regime of the Fu-Shan Experimental Forest in northeastern Taiwan. Mean number of typhoons passing within 200 kilometers of Taipei (40 kilometers from the site) was 1.4 per year. Category 4 and 5 typhoons, which are intense enough to uproot large numbers of trees, occurred every 8.3 and 12.5 years respectively, although it is likely that some category 4 and 5 typhoons did not produce extensive blowdowns at Fu-Shan because the area of maximum winds missed the study site. Uprooting was more common than snapped boles; the most common damage to trees, however, was probably defoliation, although this damage was not quantified in the current study. Thirty-five percent of wind-damaged trees were associated with a gap. Six percent of the land area was in gaps. Canopy turnover time was calculated at 175 years when all gaps ≤ 9 years old were included in the calculation, but the time decreased when older gaps were excluded from the calculation. Turnover time was somewhat higher than calculated for other tropical forests. Because turnover time increases as the percent of land in gaps decreases, the short life span of gaps at Fu-Shan probably contributed to our higher calculated time. Probability of being damaged was not related to tree species identity, and only a few species of trees were found regenerating in gaps. Principal Components Analysis indicated that damaged trees varied largely in treefall orientation and aspect; gaps varied primarily in aspect and in gap size.     

Concept and Classification of Coarse Woody Debris in Forest Ecosystems

Coarse woody debris (CWD) is generally considered as dead woody materials in various stages of decomposition, including sound and rotting logs, snags, and large branches. CWD is an important functional and structural component of forested ecosystems and plays an important role in nutrient cycling, long-term carbon storage, tree regeneration, and maintenance of heterogeneous environmental and biological diversity. However, the definition and classification of CWD have been the subject of a long debate in forest ecology. CWD has not been precisely defined. Recently, with the rapid development of landscape ecology in CWD, the USDA Forest Service and the Long Term Ecological Research (LTER) have provided a standardized definition and classification for CWD, which makes data comparison in landscape scale possible. Important characteristics of their definition include: (1) a minimum diameter (or an equivalent cross-section) of CWD ≥10 cm at the widest point (the woody debris with a diameter from 1 to 10 cm should be defined as fine woody debris, and the rest is litterfall); and (2) sound and rotting logs, snags, stumps, and large branches (located above the soil), and coarse root debris (larger than 1 cm in diameter). This classification has greatly facilitated CWD studies. Therefore, it has been widely applied in some countries (particularly in North America). However, this classification has long been a source of confusion for forest ecologists in China. Furthermore, different definitions and criteria are still adopted in individual studies, which makes the interpretation and generalization of their work difficult. This article reviewed recent progress in classifying CWD, with an emphasis on introducing the classification system of the USDA Forest Service and the LTER. It is expected that this review will help facilitate the development of standardized definition and classification suitable to forest ecosystems in China. Translated from Acta Ecologica Sinica, 2005, 25(1) (in Chinese)     

Habitat and Life History Determinants of Antbird Occurrence in Variable-Sized Amazonian Forest Fragments

The highest avian species richness on Earth is found in the Neotropics, with the speciose antbird superfamily (Thamnophilidae, Formicariidae, Grallariidae and Conopophagidae) accounting for 15 percent of South American passerine diversity. Antbird species have divergent life histories and ecological requirements, resulting in considerable interspecific variation in responses to anthropogenic habitat modification. Here, we examine interspecific differences in antbird responses to both habitat fragmentation and perturbation in a region of the so-called ‘Arc of Deforestation’ of southern Brazilian Amazonia in northern Mato Grosso. We surveyed the antbird community of 31 variable-sized forest patches and found that antbird species richness was predominantly affected by patch size and isolation, although forest patch quality was also important. Life history predictors were less important overall in determining patch occupancy and minimum patch area requirements with body mass and geographic range size the most important predictors. Foraging niche was also important; mixed flock followers, bamboo specialists and army-ant followers were all more prone to local extinction in small fragments. Although most Amazonian antbird species are not currently threatened, rates of interfluvial endemism are high and future forest loss may imperil many species currently considered to be of low conservation concern. Lessons learnt in the identification of fragmentation-sensitive genera and guilds may be applicable to other antbird species outside Amazonia, such as those in the Brazilian Atlantic Forest. Ensuring future survival of antbirds across neotropical forest landscapes that retain only a small percentage of their original primary forest cover will rest on protecting remaining large forest patches and maintaining structural and functional connectivity between them.     

Diffusion and seasonal dynamics of O2 in woody debris from the Pacific Northwest,USA

O₂ is an important regulator of physiological processes involved in the decomposition of woody debris, yet O₂ levels and diffusion rates within decomposing logs are largely unknown. We examined how O₂ diffusion rates in decayed and sound wood varied with moisture and density, and we compared predicted with observed seasonal changes in oxygen concentration in logs in a Pacific Northwest old-growth Pseudotsuga menziesii forest. In the laboratory, the oxygen diffusion coefficient (D_O2) was determined in the longitudinal and radial (or tangential) directions on wood cores of varying moisture content and density. In the field, O₂ was measured in tubes inserted to three radial depths (2, 6 and 15 cm) within logs of two species (Pseudotsuga menziesii and Tsuga heterophylla) and five decay classes (where class 5 = most decayed). In both the radial and longitudinal directions, D_O2 increased exponentially as the air filled pore space (AFPS) increased and as density decreased. In the field, mean O₂ concentrations in logs were not significantly different between species. Mean O₂ concentrations were significantly lower in the least decayed logs as compared to the most decayed logs. Mean O₂ concentrations decreased with radial depth only in decay class two logs. Seasonal O₂ levels did not consistently vary with log moisture, respiration, or air temperature. The comparison of the results from a model that assumes oxygen diffuses only in the radial direction to field data indicates that laboratory measurements of oxygen diffusion may underestimate field oxygen concentrations. Cracks, insect galleries and other passages in decayed logs, and longitudinal oxygen diffusion may account for this discrepancy. In the field, log oxygen concentrations were rarely as low as 2%, indicating anaerobic conditions may not be as common in logs as we previously thought. Oxygen limitations on decomposition may occur in relatively sound and/or water soaked wood, but probably not in decayed logs in a terrestrial setting.     

Problems of estimating population parameters and production of fish in a tropical rain forest stream,North Venezuela

The River Todasana is a small rain tropical forest stream emptying to the Caribbean Sea (Venezuela). Fish were sampled by electrofishing at three contiguous sites (pool, riffle, raceway). Nine species were recorded. Their mean biomass and production were: 43.72 kg ha⁻¹ and 36.94 kg ha⁻¹ yr⁻¹, maximum: 55.47 kg ha⁻¹ and 42.33 kg ha⁻¹ yr⁻¹, respectively.     

湘南典型次生林粗木质残体生物量、碳储量和养分特征

对九龙江森林公园次生常绿阔叶林粗木质残体(CWD)进行量化研究,了解亚热带典型次生林CWD的本底数据。以九龙江森林公园典型天然次生林中的6个20m×20m的标准样地为对象,调查并分析样地内不同分解等级CWD的生物量、碳储量和养分特征变化。九龙江森林公园亚热带典型次生林的CWD储量在2.8—30.4t/hm~2之间,碳储量在6.10—6.75t/hm~2之间,大量营养元素(N、P、K、 Ca、 Mg)含量相对稳定,化学计量变化不显著,微量营养元素中Pb与Cd元素含量随着分解等级的增加而增加。九龙江森林公园亚热带典型次生林的CWD储量在亚热带常绿阔叶林中处于中等水平,CWD主要以分解中后期的倒木为主,反映出该次生林处于中幼龄林阶段,具有较高的碳储量,养分含量相对稳定,并表现出Pb与Cd在CWD中积累的现象,在中度分解和重度分解的CWD中Pb含量分别增加了62.65%和69.88%,Cd含量则分别增加了33.33%和100%,其内在机理有待进一步深入研究。研究结果有助于进一步了解CWD如何参与森林生态系统养分循环、重金属积累等生态过程,比较不同林分干扰历史下CWD储量、分布及养分特征的异质性...     

Comparisons of the Colonisation by Invertebrates of Three Species of Wood,Alder Leaves,and Plastic “Leaves” in a Temperate Stream

Small woody debris in streams is abundant, and may be a food source or may provide a substrate on which other food sources such as biofilm may develop, both of which may be significant to invertebrates in times of food scarcity. We examined patterns of invertebrate colonisation of small woody debris (veneers of red alder, Douglas‐fir, and western red cedar), red alder leaves, and plastic (as an inert substrate to mimic leaves). Invertebrate colonisation was high on alder leaves, but low on wood substrates and plastic, controlling for the available surface area. Detritivorous invertebrates had significantly higher colonisation rates of alder leaves versus the other four substrates, whereas predators and collectors did not (consistent with their use of these as substrates and not food). All wood decreased in mass by <15% and leaves by ∼50% over the 75 days of the experiment. For all taxa tested, there was no significant difference in their colonisation of the wood veneers versus the plastic sheets. These results suggest that wood was not directly used by these invertebrates as a food source, or that there could be similar biofilm development on the surfaces of these substrates. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)