鼎湖山锥栗粗木质残体的分解和元素动态

选取锥栗(Castanopsischinensis)粗木质残体(coarsewoodydebris,CWD)的3个径级(径级1-3分别为5-10cm,10-20cm和20-30cm),并且将每个径级的锥栗粗木质残体分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ5个分解阶段。通过测定锥栗粗木质残体3个径级的Ⅰ-Ⅲ阶段的7种化学元素(C、N、P、K、Ca、Na、Mg)的浓度和CWD密度变化来研究其分解过程中的元素动态、分解速率及其分解过程中基质质量的变化。到分解阶段Ⅲ时,3个径级的重量与原来相比分别损失了36%、48%和43%。元素N、P、Mg、Ca、Na的浓度升高。元素N的累积可能和锥栗粗木质残体中寄生着固氮细菌和真菌有关。元素P、Mg、Ca、Na的浓度升高则可能是由于这4个元素因淋溶流失的速度小于锥栗粗木质残体质量的损失速度,造成元素积聚,元素C、K的浓度降低。N/P比值是较好的分解指示指标。虽然存在元素的净释放,但是由于C和其它主要元素的释放速率较慢,因而锥栗粗木质残体是森林中重要的C库和长期的元素来源。     

黄果厚壳桂种内与种间竞争的数量关系

采用Hegyi单木竞争指数模型对鼎湖山季风常绿阔叶林建群种黄果厚壳桂的种内、种间竞争强度进行定量分析.结果表明,黄果厚壳桂所受到的竞争强度随着林木径级的增大而逐渐减小.黄果厚壳桂种内竞争较与伴生树种云南银柴的种间竞争弱.黄果厚壳桂种内和种间竞争强度的顺序为:云南银柴>黄果厚壳桂种内>荷木>白颜树>肖蒲桃>锥栗>红车>臀形果>柏拉木>水石梓>窄叶半枫荷>厚壳桂.整个林分及黄果厚壳桂种内竞争木对对象木的竞争强度与对象木的胸径大小之间的关系近似服从幂函数关系,而伴生树种竞争木对对象木的竞争强度与对象木的胸径大小之间的关系近似服从对数函数关系.竞争强度和对象木的胸径大小呈显著负相关关系.     

鼎湖山季风常绿阔叶林粗死木质残体的研究

在3次样地调查的基础上对鼎湖山季风常绿阔叶林内粗死木质残体的贮量、输入量进行了研究,并通过比较林窗范围内土壤养分含量,初步评述了粗死木质残体在森林生态系统养分循环中的作用。研究结果表明:1)季风常绿阔叶林粗死木质残体的贮量为25.278t·hm~(-2),立木、倒木、大枝所占的比例分别为32.02％、49.62％和18.36％;2)1994～1999年间群落的死亡率为24％·a~(-1),死亡个体以胸径小于5cm的为主,粗死木质残体的平均输入量为4.128t·hm~(-2)·a~(-1);3)倒木主体所在的样方土壤有机质和速效钾的含量较高。     

西双版纳热带季节雨林的粗死木质残体及其养分元素

对西双版纳热带季节雨林的粗死木质残体及养分元素贮量进行了研究。结果表明,西双版纳热带季节雨林粗死木质残体的贮量为16.2 t·hm^-2,约占地上活体生物量的4%左右。其中枯立木占32.5%,倒木占33.2%,倒木残体占12.6%,大枝占21.7%。本研究的粗死木质残体贮量低于巴西和东南亚的热带雨林,处于全球热带雨林的下限。粗死木质残体的氮、磷、钾、钙、镁5种元素的贮量分别为61.8、3.4、30.4、118.3和16.5 kg·hm^-2。其中倒木所占比例最大,为31.9%～44.8%;枯立木次之（21.5%～28.7%）;倒木残体占10.3%～25.5%;3个径级的大枝占14.4%～28.9%。枯立木的C/N、C/P和N/P要高于倒木、倒木残体和大枝。     

秦岭巴山冷杉林粗死木质残体研究

 对秦岭巴山冷杉林粗死木质残体的研究表明：1)林内粗死木质残体的现存量为15.848t·hm-2,平均死亡增枯量1.877t·hm-2·a-1,平均分解量1.310t·hm-2·a-1,周转时间约为12.09年;2)粗死木质残体在碳素和养分的保持方面具有一定作用,在野生动植物生境构成中的作用较大。     

鼎湖山森林植被主要优势种黄果厚壳桂、厚壳桂生物量及第一性生产力研究

 本文研究鼎湖山森林植被主要优势种黄果厚壳桂和厚壳桂的生物量和第一性生产力。通过野外样地调查,测定2000m2样地中2个种的数量、每木高度和胸高半径,同时砍伐样木,测定2个种各部分的比例,确定它们的相对生长式,进而测定种的各部分的生物量及群落中2个种的生物量;利用红外线CO2分析仪,对2个种三年来的光合速率进行测定,进而估算2个种的光合量和第一性生产力。 本文研究结果表明,黄果厚壳桂和厚壳桂在厚壳桂群落中的生物量干重分别为：39.053t·ha-1和24.092t·ha-1(鲜重分别为68.208t·ha-1和43.733t·ha-1);净第一性生产力分别为2.384t·ha-1·a-1和1.13t·ha-1·a-1。文章对研究结果作进一步的讨论,以揭示2个种在群落中的作用和地位。     

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%。     

广州三种森林粗死木质残体（CWD）的储量与分解特征

粗死木质残体(Coarse Woody Debris, CWD)对森林生态系统的稳定性具有不可忽视的贡献.对广州3种森林CWD的储量与分解特征进行了调查分析,结果表明:(1)CWD储量及其与相应森林总生物量比值均表现为常绿阔叶林>针阔混交林>针叶林;枯立木与倒木为CWD的主要成分,其中,针叶CWD主要物种为马尾松(Pinus massonianai),阔叶CWD物种主要为荷木(Schima superba)与黄杞(Engelhardtia chrysolepis)等.(2)CWD径级主要集中在<10cm的范围内,存在状态主要为中级腐烂状态,干扰与竞争是3种森林CWD产生的主要因素.(3)针叶林、针阔混交林与常绿阔叶林CWD的分解常数k分别为0 0244、0.0407和0.0487,即分解速率为常绿阔叶林>混交林>针叶林;随着CWD的分解,N、P与木质素的含量逐渐升高,C、C/N与木质素/N呈降低趋势.     

八大公山亚热带森林木质残体中大型无脊椎动物群落特征

木质残体可为大型无脊椎动物提供重要栖息地、食物等资源, 并影响其生物多样性。目前针对不同树种、径级及分解阶段的木质残体如何调控土壤大型无脊椎动物群落结构尚不清楚, 相关研究在亚热带森林地区尤为稀缺。为此, 本文选取湖南省八大公山国家级自然保护区柳杉(Cryptomeria fortunei)、亮叶水青冈(Fagus lucida)及檫木(Sassafras tzumu) 3种树种为研究对象, 每种树种分别选取两类径级(直径分别为10 ± 2 cm、4 ± 2 cm)不同分解阶段的木质残体, 对其中的大型无脊椎动物进行调查。调查于2020年10-11月完成。结果显示: 共捕获大型无脊椎动物2,558只, 隶属4门10纲23目, 不同树种的优势类群、常见类群及稀有类群均存在差异。亮叶水青冈木质残体中大型无脊椎动物个体密度显著高于柳杉和檫木。亮叶水青冈和檫木大径级木质残体中大型无脊椎动物Shannon-Wiener多样性指数显著高于小径级, 3个树种大径级木质残体中大型无脊椎动物的类群数、特有类群数均大于小径级。木质残体中大型无脊椎动物的Shannon-Wiener多样性指数、Simpson优势度指数及Pielou均匀度指数与木材密度显著负相关, 表明随着分解的进行木质残体中大型无脊椎动物群落呈明显变化趋势。木质残体的理化性质(相对含水率、全氮、全碳及碳氮比)和土壤温度、湿度与木质残体中大型无脊椎动物群落特征具有相关性。研究初步表明, 大型无脊椎动物群落特征在所选树种、径级及分解阶段木质残体中具有差异, 在亚热带森林中同时保留不同树种、不同大小径级的木质残体或有利于增加大型无脊椎动物多样性。     

粗木质物残体生态研究历史、现状和趋势

粗木质物残体(Coarse Woody Debris,简称CWD)是森林生态系统或溪流生态系统中残存的一定直径大小的站杆(snag)、倒木、枝桠及根系等死木质物的总称,倒木往往是     

东北东部山区11种温带树种粗木质残体分解与碳氮释放

采用长期定位跟踪实测方法,比较分析了我国东北温带森林4个水热状况不同的立地条件(红松(Pinus koraiensis)人工林、硬阔叶林、蒙古栎(Quercus mongolica)林和林外空旷地)下11个温带树种粗木质残体(CWD)分解初期3年中的碳氮动态及其影响因子。测定树种包括:白桦(Betula platyphylla)、山杨(Populus davidiana)、紫椴(Tilia amurensis)、胡桃楸(Juglans mandshurica)、蒙古栎、色木槭(Acer mono)、春榆(Ulmus japonica)、红松、黄檗(Phellodendron amurense)、兴安落叶松(Larix gmelinii)和水曲柳(Fraxinus mandshurica)。结果表明:在分解过程中,所有树种CWD的碳浓度没有明显变化(p0.05),但其干重、碳密度、氮浓度和氮密度均随分解进程不同程度地减小,碳氮比(C/N)则增大,而且树种间差异显著(p0.001)。针叶树种的CWD分解速率显著地低于阔叶树种,其中白桦的3年CWD干重损失率(65%)约为兴安落叶松(22%)的3倍。径级大的CWD分解较慢。CWD分解与碳氮释放均与CWD的初始N含量呈正相关,而与初始C/N呈负相关。4个立地条件下CWD的干重和碳氮含量的变化差异不显著,均表现出一致的变化趋势。该研究指出,在分解初期的前3年中,CWD基本上是一个碳源和氮源。     

Coarse woody debris modifies surface soils of degraded temperate eucalypt woodlands

Aims

Reintroductions of coarse woody debris (CWD) to Australia’s temperate eucalypt woodlands have been proposed to address the paucity of CWD in these landscapes. This study aimed to quantify the effects of CWD on surface soils.

Methods

Values of C, N, C:N, P, NO₃ ^?, NH₄ ⁺, pH and electrical conductivity (EC) were measured adjacent to, and at reference distances from CWD. Soils were measured at depths of 0–1 cm, 1–3 cm and 3–5 cm for 12 individual CWD samples of varying decay classes and diameters. A linear mixed model was used to test the effects of the presence of CWD, soil depth and CWD decay class and diameter.

Results

Significantly larger values for C, N, C:N, P, NO₃ ^?, EC, and significantly smaller values for pH were found adjacent to CWD. The greatest impact of CWD was on the upper most surface soil. CWD decay class and diameter had little influence on the measured soil characteristics.

Conclusion

This is the first quantitative determination of the effects of eucalypt CWD on woodland soils in Australia. The effect of added CWD is rapid, occurring after just 2 years. The results suggest that the effects are due to the structural properties of CWD.     

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.     

Role of coarse woody debris in the carbon cycle of Takayama forest,central Japan

Coarse woody debris (CWD) is an important component of the forest carbon cycle, acting as a carbon pool and a source of CO₂ in temperate forest ecosystems. We used a soda-lime closed-chamber method to measure CO₂ efflux from downed CWD (diameter ≥5 cm) and to examine CWD respiration (R _CWD) under field conditions over 1 year in a temperate secondary pioneer forest in Takayama forest. We also investigated tree mortality (input to the CWD pool) from the data obtained from the annual tree census, which commenced in 2000. We developed an exponential function of temperature to predict R _CWD in each decay class (R ² = 0.81–0.97). The sensitivity of R _CWD to changing temperature, expressed as Q ₁₀, ranged from 2.12 to 2.92 and was relatively high in decay class III. Annual C flux from CWD (F _CWD) was extrapolated using continuous air temperature measurements and CWD necromass pools in the three decay classes. F _CWD was 3.0 (class I), 17.8 (class II), and 13.7 g C m^?2 year^?1 (class III) and totaled 34 g C m^?2 year^?1 in 2009. Annual input to CWD averaged 77 g C m^?2 year^?1 from 2000 to 2009. The budget of the CWD pool in the Takayama forest, including tree mortality inputs and respiratory outputs, was 0.43 Mg C ha^?1 year^?1 (net C sink) owing to high tree mortality in the mature pioneer forest. The potential CWD sink is important for the carbon cycle in temperate successional forests.     

Linking wood-decay fungal communities to decay rates: Using a long-term experimental manipulation of deadwood and canopy gaps

Decomposition transfers carbon (C) from detrital organic matter to soil and atmospheric pools. In forested ecosystems, deadwood accounts for a large proportion of the detrital C pool and is primarily decomposed by wood-inhabiting fungi (WIF). Deadwood reductions linked to forest harvesting may alter WIF richness and composition, thus indirectly influencing the persistence of deadwood and its contribution to C and nutrient cycling. Forest structure was enhanced via canopy gap creation and coarse woody debris (CWD) addition that mimic natural disturbance by windfall within a deciduous northern hardwood forest (Wisconsin, USA) to examine its effect on deadwood-associated biodiversity and function. Experimental sugar maple (Acer saccharum) logs were sampled, for DNA extraction, ten years after placement to determine the assembly of fungal community composition and its relationship to wood decay rates.Our findings suggest that the WIF community responded to gap disturbance by favoring species able to persist under more extreme microclimates caused by gaps. CWD addition under closed canopy tended to favor a different species assemblage from gap creation treatments and the control, where canopy was undisturbed and CWD was not added. This was presumably due to consistent microclimatic conditions and the abundance of CWD substrates for host specialists. Fungal OTU richness was significantly and inversely related to CWD decay rates, likely due to competition for resources. In contrast, fungal OTU composition was not significantly related to CWD decay rates, canopy openness or CWD addition amounts. Our study site represents a diverse fungal community in which complex interactions among wood-inhabiting organisms and abiotic factors are likely to slow CWD decomposition, which suggests that maintaining a biodiverse and microsite-rich ecosystem may enhance the capacity for C storage within temperate forests.     

模拟氮沉降对南亚热带两种乔木幼苗生物量及其分配的影响

探讨了南亚热带季风常绿阔叶林两种优势树种荷木(Schima superba)和黄果厚壳桂(Cryptocarya concinna)幼苗的生物量及其分配对氮沉降增加的响应。实验分为对照(CK)、T₅、T₁₀、T₁₅和T₃₀ 5个处理,每个处理设置3次重复。所施氮肥为NH₄NO₃,以溶液方式喷施,5个处理浓度分别为0、0.12、0.24、0.36、0.72 mol N·L^-1。每月喷施2次,5个样方1年喷施的总氮量分别相当于氮沉降率0、5、10、15、30 g N·m^-2·a^-1。经过11个月的施氮处理,两种幼苗对氮沉降的响应存在差异,其中黄果厚壳桂幼苗的基径、株高、全株生物量和相对生长速率除最高处理T₃₀外,均高于对照,但荷木幼苗的基径、全株生物量和相对生长速率除T₁₀外,均小于对照。氮处理也对生物量的分配产生了明显的影响,两种幼苗的叶重比以T₃₀最低,表明高氮处理不利于幼苗叶片的生长;枝重比均以T₃₀最高,反映了高氮处理的幼苗生物量分配到枝干的比例最高;根重比和根冠比均以对照样方幼苗的最高,表明氮处理抑制根的生长,分配到根部分的生物量下降。总的来看,经过11个月的处理,除最高处理T₃₀外,氮处理仍对黄果厚壳桂幼苗的生长有促进作用,而对荷木幼苗的生长则趋向于一定程度的抑制效应,表明黄果厚壳桂幼苗更能耐受高氮条件。     

Accumulation and decay dynamics of coarse woody debris in a Japanese old-growth subalpine coniferous forest

Far less is known about the coarse woody debris (CWD) stock and decay process in temperate Asia compared with that in boreal and temperate Europe and North America. We estimated coniferous CWD stock (logs and snags), decay rate and process, and fungal species responsible for the decay process in a Japanese subalpine coniferous forest. The CWD mass was 42.4 Mg ha^?1, which was the greatest among the previous data recorded in temperate Asia. The decay rate calculated using the annual input of CWD divided by CWD accumulation was 0.036 year^?1, whereas the decay rate when measured chronosequentially was 0.020–0.023 year^?1. The decay process was divided into two phases characterized by different dominant organic chemical constituents. In the first phase, both acid-unhydrolyzable residue and holocellulose decayed simultaneously, suggestive of the white-rot process. In the second phase, holocellulose was selectively decomposed and AUR accumulated, suggestive of the brown-rot process. Nutrients (N, P, K, Na, Mg, and Ca) were mineralized in the first phase but immobilized in the second phase. The fruiting bodies of 26 taxa of fungi were recorded as occurring on CWD in the study area. Trichaptum abietinum and T. fuscoviolaceum, which dominated in the first phase and are known as white-rot fungi, were assumed to be the main decomposers of lignocellulose in the first phase. Although no known strong wood decomposers dominated the second phase, Laetiporus sulphureus and Oligoporus caesius, known as brown-rot fungi, were expected to participate in the selective decomposition of holocellulose in the second phase.