帽儿山3种森林生态系统土壤动物与土壤呼吸及其相互关系研究

土壤呼吸是森林生态系统碳循环的关键过程,土壤动物可通过自身代谢及影响微生物活动调控土壤呼吸,因此研究土壤动物与土壤呼吸的相互关系对进一步揭示生态系统碳循环的规律和机理具有重要意义。通过野外定点,以帽儿山3种森林生态系统的土壤呼吸及土壤动物为研究对象,探讨不同森林生态系统的土壤呼吸、土壤动物个体密度和生物量的时间变化规律及二者相互关系。结果表明:(1)3种森林生态系统土壤总呼吸速率与土壤异养呼吸速率均呈现先增强后减弱的时间动态变化(P<0.05),且不同森林生态系统土壤异养呼吸速率差异显著(P<0.05),表现为硬阔叶林最高,红松人工林最低;(2)3种森林生态系统土壤动物生物量也具有显著的时间动态变化(P<0.05),均在9月份达到最大,且不同森林生态系统土壤动物个体密度显著不同(P<0.05),蒙古栎林土壤动物个体密度显著小于红松人工林与硬阔叶林;(3)通过回归分析可得,土壤动物数量及生物量的增加抑制了土壤呼吸速率,尤其在生长季初期、末期。研究表明土壤动物可通过抑制微生物生命活动和降低根系呼吸从而对土壤总呼吸及异养呼吸产生负反馈作用,三者是不可分割的整体,与土壤温度、水分等环境因子共同调控着土壤呼吸。     

东北东部森林生态系统土壤呼吸组分的分离量化

对森林生态系统的土壤呼吸组分进行分离和量化,确定不同组分CO2释放速率的控制因子,是估测局域和区域森林生态系统碳平衡研究中必不可少的内容。采用挖壕法和红外气体分析法测定无根和有根样地的土壤表面CO2通量(RS),确定东北东部6种典型森林生态系统RS中异养呼吸(RH)和根系自养呼吸(RA)的贡献量及其影响因子。具体研究目标包括:(1)量化各种生态系统的RH及其与主要环境影响因子的关系;(2)量化各种生态系统RS中根系呼吸贡献率(RC)的季节动态;(3)比较6种森林生态系统RH和RA的年通量。土壤温度、土壤含水量及其交互作用显著地影响森林生态系统的RH(R2=0.465~0.788),但其影响程度因森林生态系统类型而异。硬阔叶林和落叶松人工林的RH主要受土壤温度控制,其他生态系统RH受土壤温度和含水量的联合影响。各个森林生态系统类型的RC变化范围依次为:硬阔叶林32.40%~51.44%;杨桦林39.72%~46.65%;杂木林17.94%~47.74%;蒙古栎林34.31%~37.36%;红松人工林33.78%~37.02%;落叶松人工林14.39%~35.75%。每个生态系统类型RH年通量都显著高于RA年通量,其变化范围分别为337~540 gC.m-2.a-1和88~331 gC.m-2.a-1。不同生态系统间的RH和RA也存在着显著性差异。     

Partitioning soil respiration of temperate forest ecosystems in northeastern China

Quantifying soil respiration components and their relations to environmental controls are essential to estimate both local and regional carbon (C) budgets of forest ecosystems. In this study, we used the trenching-plot and infrared gas exchange analyzer approaches to determine heterotrophic (R_H) and autotrophic respiration (R_A) in the soil surface CO₂ flux for six major temperate forest ecosystems in northeastern China. The ecosystems were: Mongolian oak forest (dominated by Quercus mongolica), aspen-birch forest (dominated by Populous davidiana and Betula platyphylla), mixed wood forest (composed of P. davidiana, B. platyphylla, Fraxinus mandshurica, Tilia amurensis, Acer amono, etc.), hardwood forest (dominated by F. mandshurica, Juglans mandshurica, and Phellodendron amurense), Korean pine (Pinus koraiensis), and Dahurian larch (Larix gmelinii) plantations, representing the typical secondary forest ecosystems in this region. Our specific objectives were to: (1) quantify R_H and its relationship with the environmental factors of the forest ecosystems, (2) characterize seasonal dynamics in the contribution of root respiration to total soil surface CO₂ flux (RC), and (3) compare annual CO₂ fluxes from R_H and R_A among the six forest ecosystems. Soil temperature, water content, and their interactions significantly affected R_H in the ecosystems and accounted for 46.5%–78.8% variations in R_H. However, the environmental controlling factors of R_H varied with ecosystem types: soil temperature in hardwood and Dahurian larch forest ecosystems, soil temperature, and water content in the others. The RC for hardwood, poplar-birch, mixed wood, Mongolian oak, Korean pine, and Dahurian larch forest ecosystems varied between 32.40%–51.44%, 39.72%–46.65%, 17.94%–47.74%, 34.31%–37.36%, 33.78%–37.02%, and 14.39%–35.75%, respectively. The annual CO₂ fluxes from R_H were significantly greater than those from R_A for all the ecosystems, ranging from 337–540 g Cm^-2a^-1 and 88‐331 gCm^-2a^-1 for R_H and R_A, respectively. The annual CO₂ fluxes from R_H and R_A differed significantly among the six forest ecosystems.     

典型森林和草地生态系统呼吸各组分间的相互关系

生态系统呼吸是陆地生态系统碳收支的重要组成部分,分析其组分间的相互关系对理解生态系统呼吸过程和精确评价生态系统碳收支具有重要意义,也是当前碳循环研究工作的一大难点。本研究利用ChinaFLUX的长白山温带针阔混交林（CBS）,鼎湖山亚热带常绿阔叶林（DHS）和海北灌丛草甸（HBGC）三个典型生态系统的通量观测数据,采用经验统计方法,分析了其在中国典型生态系统中的适用性及敏感性,揭示了生态系统呼吸各组分的动态变化特征及相互关系。结果表明：采用本研究中的呼吸组分拆分方法所获结果与理论推测及实测数据大致相同,拆分结果对净初级生产力与总初级生产力的比值（NPP/GPP）较为敏感,NPP/GPP变化0.1时,自养呼吸在生态系统呼吸中的比例（Ra/RE）改变0.05。各生态系统中,生态系统呼吸及其组分在年内均表现出明显的单峰型变化特征,在夏季生长旺盛的时节达到最大值。异养呼吸与生态系统呼吸的比值（Rh/RE）也具有明显的季节变化,但在生态系统间表现出明显差异,CBS和HBGC分别表现出先增大后减小和先减小后增大的变化趋势,DHS则相对稳定,在0.5附近波动, Ra/RE的季节动态与Rh/RE相反。在年总量上,HBGC主要通过异养呼吸向大气排放CO2,异养呼吸占生态系统呼吸的60%,而CBS和DHS的自养呼吸和异养呼吸所占比重大致相似,异养呼吸占生态系统呼吸的49%。这说明,该统计学模型可以用来进行生态系统呼吸组分的拆分,进而可以为生态系统碳循环过程的精细研究提供参考数据,但今后应加强NPP/GPP的测定,以提高生态系统呼吸拆分的精度。     

Indirect partitioning of soil respiration in a series of evergreen forest ecosystems

A simple estimation of heterotrophic respiration can be obtained analytically as the y-intercept of the linear regression between soil-surface CO₂ efflux and root biomass. In the present study, a development of this indirect methodology is presented by taking into consideration both the temporal variation and the spatial heterogeneity of heterotrophic respiration. For this purpose, soil CO₂ efflux, soil carbon content and main stand characteristics were estimated in seven evergreen forest ecosystems along an elevation gradient ranging from 250 to 1740 m. For each site and for each sampling date the measured soil CO₂ efflux (R _S) was predicted with the model R _S = a × S _C + b × R _D ± ε, where S _C is soil carbon content per unit area to a depth of 30 cm and R _D is the root density of the 2–5 mm root class. Regressions with statistically significant a and b coefficients allowed the indirect separation of the two components of soil CO₂ efflux. Considering that the different sampling dates were characterized by different soil temperature, it was possible to investigate the temporal and thermal dependency of autotrophic and heterotrophic respiration. It was estimated that annual autotrophic respiration accounts for 16–58% of total soil CO₂ efflux in the seven different evergreen ecosystems. In addition, our observations show a decrease of annual autotrophic respiration at increasing availability of soil nitrogen. Section Editor: A. Hodge     

鸡公山典型落叶阔叶林土壤呼吸对食叶虫灾爆发的响应

土壤呼吸是陆地生态系统碳循环的关键环节之一。随着极端气候事件的频发,森林虫害的发生频率和强度也趋于增加,森林虫害爆发已经是影响森林生态系统碳循环过程的一种重要的自然干扰。气候过渡带典型森林生态系统虫灾的爆发是否会影响土壤的碳排放过程目前仍不清楚。本研究利用鸡公山地区麻栎-枫香混交林大规模爆发食叶性害虫的机会,比较虫灾爆发当年(2014)与正常年份(2015)的土壤碳排放通量,以阐明森林虫灾爆发对土壤碳排放通量的影响。结果表明:虫灾爆发当年7、8、9、10月份土壤平均温度比正常年份相应各月份分别高0.26、0.51、0.83、0.07℃,土壤呼吸分别显著提高了129.9%、77.1%、61.6%和58.9%。虫灾爆发年份生长季的平均土壤呼吸为3.55μmol m~(-2)s~(-1),比正常年份(2.77μmol m~(-2)s~(-1))高36.2%;生长季期间的平均土壤异养呼吸比正常年份增加了29.7%。该研究表明森林食叶虫害的爆发至少在短期内可导致森林土壤碳排放量呈显著的增加趋势,近而对森林生态系统土壤碳库积累产生重要影响。因此,充分认识病虫害对森林生态系统的干扰和影响,将有助于陆地生态系统碳循环的准确估算和模拟。     

火干扰对森林生态系统土壤呼吸组分的影响研究进展

土壤呼吸是陆地生态系统与大气碳交换的主要方式,主要分为自养呼吸和异养呼吸。土壤呼吸不仅是森林生态系统碳循环过程的关键环节,也是森林生态系统能量流动和物质循环的重要生态过程。火作为森林生态系统中一个重要的生态因子,可以在短时间内对土壤呼吸组分造成巨大的影响。火干扰对土壤呼吸组分的影响与火烧强度、火烧频率、火烧持续时间以及火后恢复等因子有关,通过影响植被的根系与组成、微生物群落数量与结构,凋落物的数量以及生态系统的环境和小气候等,进而对土壤呼吸产生影响。火干扰对土壤呼吸影响整体表现为火烧后土壤呼吸速率下降,在几个月至几年内恢复到火烧前水平,之后火继续对土壤呼吸产生影响长达数年至数十年。通过描述火烧强度、火烧频率以及火后恢复时间,阐述火干扰对土壤呼吸组分的直接影响,以及通过火后环境对土壤呼吸组分产生的间接影响,来揭示火干扰对森林生态系统土壤呼吸组分的影响。同时针对火干扰对土壤呼吸组分的影响进行以下3个方面的研究展望：（1）火后产生的黑碳对土壤呼吸组分的影响;（2）火后植被恢复对土壤呼吸组分产生的影响;（3）火后土壤呼吸组分的长期变化规律。     

寒温带兴安落叶松林凋落物层对土壤呼吸的影响

为了进一步探讨土壤凋落物层对土壤呼吸的影响,用Li-6400对大兴安岭北部3种林型(白桦-落叶松林、樟子松-落叶松林和落叶松纯林)自然状态的土壤呼吸(R_S)、去凋落物后的土壤呼吸(R_D)以及凋落物呼吸(R_L)进行测定,结果表明:凋落物层的去除会使土壤呼吸速率降低,3种林型观测期内平均R_S分别为7.32μmol m^-2 s^-1、8.55μmol m^-2 s^-1和6.66μmol m^-2 s^-1,平均R_D分别为6.46μmol m^-2 s^-1、7.98μmol m^-2 s^-1和5.74μmol m^-2 s^-1。但去除凋落物后的土壤总呼吸速率较自然状态下分别升高了13.85%、16.21%和13.73%;凋落物的去除并不影响...     

中国典型森林生态系统土壤水分时空分异及其影响因素

森林土壤水分作为物质与能量循环的载体影响林木生长与发育,并通过影响水分在陆气之间的循环与分配影响区域气候。基于我国不同气候带的9个森林生态系统定位观测站的长期观测数据,探究了2005-2016年中国典型森林生态系统土壤水分的空间分异及其时间动态,并进一步分析了影响其时空分异的环境因素。主要研究结论如下：（1）9个森林生态系统的土壤水分多年均值介于12.45%-36.30%之间,空间上呈现中温带、亚热带、热带土壤水分较高,暖温带土壤水分较低的分布特征。降水蒸散差（降水与蒸散的差值）可以解释我国森林生态系统土壤水分空间分异的62%（P<0.05）;（2）我国北部与东部季风区森林区域土壤水分呈上升趋势,降水上升是主因,其中暖温带北京、南亚热带鼎湖山与鹤山森林土壤水分上升趋势显著,增幅分别为0.67%/a、1.72%/a与0.69%/a;西南地区森林生态系统土壤水分呈下降趋势,该趋势由降水下降与蒸散上升共同导致,其中中亚热带贡嘎山及哀牢山森林生态系统土壤水分下降趋势显著,降幅分别为-1.77%/a与-0.94%/a;土壤水分时间分异与降水蒸散差的相关性最高（R=0.59,P<0.01）;（3）土壤水分呈下降趋势的森林生态系统中,春季土壤水分变化主导了年际变化,土壤水分上升的森林生态系统中,年际变化则是由秋、冬季主导。（4）与ERA-interim土壤水分再分析数据比较得出,两者在空间格局与变化趋势上均具有较高的一致性。CERN土壤水分观测数据反映了无人为干扰的自然条件下森林土壤-植被-气候之间的反馈作用,可为基于模型的土壤水分研究提供长时序的验证数据。     

基于中国生态系统研究网络的典型森林生态系统土壤保持功能分析

森林生态系统土壤保持功能在控制土壤侵蚀以及维持生态安全方面具有不可替代的作用。根据不同气候带降雨特征进行降雨侵蚀力参数校正,基于中国生态系统研究网络(CERN)的森林生态系统长期定位观测样地2005—2015年监测数据利用修正的通用土壤流失方程(RUSLE)定量分析了典型森林生态系统土壤保持功能的时空变化特征,并探讨了土壤保持功能的影响因素。研究结果表明:①日雨量侵蚀力模型在降雨丰富的热带模拟效果优于降雨相对较少的亚热带和温带,参数校正后模拟效果明显提升;②研究期内10个典型森林生态系统土壤保持量变化范围为4.44—891.67 t hm^-2 a^-1,呈现北低南高的空间格局(R²=0.65^***);土壤保持率均达到97%以上;③降雨、归一化植被指数、土壤质地和植被林龄是影响森林生态系统土壤保持功能的主要影响因素;降雨量与土壤保持量显著相关(R²=0.52^*),NDVI和土壤质地与实际土壤侵蚀量显著相关(R²=0.64^**     

Effect of soil microorganisms and labile C availability on soil respiration in response to litter inputs in forest ecosystems: A meta‐analysis

Litter inputs can influence soil respiration directly through labile C availability and, indirectly, through the activity of soil microorganisms and modifications in soil microclimate; however, their relative contributions and the magnitude of any effect remain poorly understood. We synthesized 66 recently published papers on forest ecosystems using a meta‐analysis approach to investigate the effect of litter inputs on soil respiration and the underlying mechanisms involved. Our results showed that litter inputs had a strong positive impact on soil respiration, labile C availability, and the abundance of soil microorganisms, with less of an impact related to soil moisture and temperature. Overall, soil respiration was increased by 36% and 55%, respectively, in response to natural and doubled litter inputs. The increase in soil respiration induced by litter inputs showed a tendency for coniferous forests (50.7%)> broad‐leaved forests (41.3%)> mixed forests (31.9%). This stimulation effect also depended on stand age with 30‐ to 100‐year‐old forests (53.3%) and ≥100‐year‐old forests (50.2%) both 1.5 times larger than ≤30‐year‐old forests (34.5%). Soil microbial biomass carbon and soil dissolved organic carbon increased by 21.0%‐33.6% and 60.3%‐87.7%, respectively, in response to natural and doubled litter inputs, while soil respiration increased linearly with corresponding increases in soil microbial biomass carbon and soil dissolved organic carbon. Natural and doubled litter inputs increased the total phospholipid fatty acid (PLFA) content by 6.6% and 19.7%, respectively, but decreased the fungal/bacterial PLFA ratio by 26.9% and 18.7%, respectively. Soil respiration also increased linearly with increases in total PLFA and decreased linearly with decreases in the fungal/bacterial PLFA ratio. The contribution of litter inputs to an increase in soil respiration showed a trend of total PLFA > fungal/bacterial PLFA ratio > soil dissolved organic carbon > soil microbial biomass carbon. Therefore, in addition to forest type and stand age, labile C availability and soil microorganisms are also important factors that influence soil respiration in response to litter inputs, with soil microorganisms being more important than labile C availability.     

Spatial variation and controlling factors of temperature sensitivity of soil respiration in forest ecosystems across China

土壤呼吸的温度敏感性(Q₁₀)是陆地碳循环与气候系统间相互作用的关键参数。尽管已有大量关于不同类型森林Q₁₀季节和年际变化规律的研究, 但是对Q₁₀在区域尺度的空间变异特征及其影响因素仍认识不足, 已有结果缺乏一致结论。该研究通过整合已发表论文, 构建了中国森林生态系统年尺度Q₁₀数据集, 共包含399条记录、5种森林类型(落叶阔叶林(DBF)、落叶针叶林(DNF)、常绿阔叶林(EBF)、常绿针叶林(ENF)、混交林(MF))。分析了不同森林类型Q₁₀的空间变异特征及其与地理、气候和土壤因素的关系。结果显示, 1) Q₁₀介于1.09到6.24之间, 平均值(±标准误差)为2.37 (± 0.04), 且在不同森林类型之间无显著差异; 2)当考虑所有森林类型时, Q₁₀随纬度、海拔、土壤有机碳含量(SOC)和土壤全氮含量(TN)的增加而增大, 随经度、年平均气温(MAT)、平均年降水量(MAP)的增加而减小。气候(MAT、MAP)和土壤(SOC、TN)因素间存在相互作用, 共同解释了33%的Q₁₀空间变异, 其中MAT和SOC是Q₁₀空间变异的主要驱动因素; 3)不同类型森林Q₁₀对气候和土壤因素的响应存在差异。在DNF中Q₁₀随MAP的增加而减小, 而其他类型森林中Q₁₀与MAP无显著相关性; 在EBF、DBF、ENF中Q₁₀随TN的增加而增大, 但Q₁₀对TN的敏感性在EBF中最高, 在ENF中最低。这些结果表明, 尽管Q₁₀有一定的集中分布趋势, 但仍有较大范围的空间变异, 在进行碳收支估算时应注意尺度问题。Q₁₀的主要驱动因素和Q₁₀对环境因素的响应随森林类型而变化, 在气候变化情景下, 不同森林类型间Q₁₀可能发生分异。因此, 未来的碳循环-气候模型还应考虑不同类型森林碳循环关键参数对气候变化的响应差异。     

桫椤生态系统的土壤呼吸特征

桫椤植物最早出现于中生代的晚三叠纪或早侏罗纪,现存的桫椤林是一种非常典型的孓遗陆地生态系统.对桫椤生态系统土壤呼吸特征研究表明,6月份桫椤纯林的土壤呼吸速率很小,去除凋落物和保留凋落物的土壤呼吸速率分别为0.87、0.89μmol · m-2 · s-1,两种处理无显著差异(P>0.05).由于其它生物的入侵,在保护区桫椤林中出现了多种混交的森林类型,比较典型的是毛竹、落叶阔叶林、常绿阔叶林作为桫椤纯林的入侵种与其形成的3种生态系统类型,根据测定的结果,表明这3种生态系统类型的林地土壤呼吸速率均大于桫椤纯林,平均值分别为2.95、2.06、1.33μmol · m-2· s-1,经统计分析,发现它们与桫椤纯林有显著的差异(P<0.001).凋落物对这3种类型的影响表现为,毛竹桫椤混交林、常绿阔叶桫椤混交林差异显著(P<0.001),落叶阔叶和桫椤混交林差异不明显(P>0.05 );在较短时间尺度上对4种森林类型的日动态分析,均表现为一致的平稳状态.在土壤温度和湿度变化较小的情况下,两种处理5cm土壤温度和湿度均与土壤呼吸无明显相关性.     

森林土壤呼吸研究进展

各种测量森林土壤呼吸的方法都存在不足,红外CO₂分析仪法是目前最理想的方法;土壤CO₂通量模型的优点是考虑了土壤呼吸生物和物理学过程;一般情况下,温度和湿度与森林土壤呼吸呈正相关关系,火烧、采伐和施肥等营林活动对土壤呼吸的影响有很大的不确定性;森林土壤呼吸与植被、微生物生物量的关系,以及土壤呼吸的空间变异规律已成为近年来的研究热点.最后提出了森林土壤呼吸研究中存在的一些问题及今后的发展方向.     

中国森林生态系统土壤呼吸温度敏感性空间变异特征及影响因素

土壤呼吸的温度敏感性(Q₁₀)是陆地碳循环与气候系统间相互作用的关键参数。尽管已有大量关于不同类型森林Q₁₀季节和年际变化规律的研究, 但是对Q₁₀在区域尺度的空间变异特征及其影响因素仍认识不足, 已有结果缺乏一致结论。该研究通过整合已发表论文, 构建了中国森林生态系统年尺度Q₁₀数据集, 共包含399条记录、5种森林类型(落叶阔叶林(DBF)、落叶针叶林(DNF)、常绿阔叶林(EBF)、常绿针叶林(ENF)、混交林(MF))。分析了不同森林类型Q₁₀的空间变异特征及其与地理、气候和土壤因素的关系。结果显示, 1) Q₁₀介于1.09到6.24之间, 平均值(±标准误差)为2.37 (± 0.04), 且在不同森林类型之间无显著差异; 2)当考虑所有森林类型时, Q₁₀随纬度、海拔、土壤有机碳含量(SOC)和土壤全氮含量(TN)的增加而增大, 随经度、年平均气温(MAT)、平均年降水量(MAP)的增加而减小。气候(MAT、MAP)和土壤(SOC、TN)因素间存在相互作用, 共同解释了33%的Q₁₀空间变异, 其中MAT和SOC是Q₁₀空间变异的主要驱动因素; 3)不同类型森林Q₁₀对气候和土壤因素的响应存在差异。在DNF中Q₁₀随MAP的增加而减小, 而其他类型森林中Q₁₀与MAP无显著相关性; 在EBF、DBF、ENF中Q₁₀随TN的增加而增大, 但Q₁₀对TN的敏感性在EBF中最高, 在ENF中最低。这些结果表明, 尽管Q₁₀有一定的集中分布趋势, 但仍有较大范围的空间变异, 在进行碳收支估算时应注意尺度问题。Q₁₀的主要驱动因素和Q₁₀对环境因素的响应随森林类型而变化, 在气候变化情景下, 不同森林类型间Q₁₀可能发生分异。因此, 未来的碳循环-气候模型还应考虑不同类型森林碳循环关键参数对气候变化的响应差异。     

Impact of rainfall manipulations and biotic controls on soil respiration in Mediterranean and desert ecosystems along an aridity gradient

Spatially heterogeneous ecosystems form a majority of land types in the vast drylands of the globe. To evaluate climate‐change effects on CO₂ fluxes in such ecosystems, it is critical to understand the relative responses of each ecosystem component (microsite). We investigated soil respiration (R_s) at four sites along an aridity gradient (90–780 mm mean annual precipitation, MAP) during almost 2 years. In addition, R_s was measured in rainfall manipulations plots at the two central sites where ～30% droughting and ～30% water supplementation treatments were used over 5 years. Annual R_s was higher by 23% under shrub canopies compared with herbaceous gaps between shrubs, but R_s at both microsites responded similarly to rainfall reduction. Decreasing precipitation and soil water content along the aridity gradient and across rainfall manipulations resulted in a progressive decline in R_s at both microsites, i.e. the drier the conditions, the larger was the effect of reduction in water availability on R_s. Annual R_s on the ecosystem scale decreased at a slope of 256/MAP g C m^?2 yr^?1 mm^?1 (r²=0.97). The reduction in R_s amounted to 77% along the aridity gradient and to 16% across rainfall manipulations. Soil organic carbon (SOC) decreased with declining precipitation, and variation in SOC stocks explained 77% of the variation in annual R_s across sites, rainfall manipulations and microsites. This study shows that rainfall manipulations over several years are a useful tool for experimentally predicting climate‐change effects on CO₂ fluxes for time scales (such as approximated by aridity gradients) that are beyond common research periods. Rainfall reduction decreases rates of R_s not only by lowering biological activity, but also by drastically reducing shrub cover. We postulate that future climate change in heterogeneous ecosystems, such as Mediterranean and deserts shrublands will have a major impact on R_s by feedbacks through changes in vegetation structure.     

Macrofungal diversity and ecology in two Mediterranean forest ecosystems

The macrofungal species richness and community assemblages in Italian native woodlands of oaks and Carpinus betulus and non-native woodlands of Pinus spp., Cupressus sempervirens and Eucalyptus camaldulensis were examined through the collection of basidiomata and ascomata over 1 year. The sampling in Collestrada (Umbria) and Pizzo Manolfo (Sicily) forests revealed 216 species of macrofungi. The results indicate differences in macromycete richness and diversity patterns between the two sites. The dominant tree species of the two sites were different; thus, the Collestrada forests had higher mycorrhizal species richness, while the Pizzo Manolfo forest had a higher relative number of saprotroph macrofungi. The macrofungal community of Quercus frainetto woodland from Collestrada forest was richer and more diverse than the other site's woodland types. This study highlighted that both Collestrada and Pizzo Manolfo forests provide a habitat for diverse macrofungal species, not in the least ectomycorrhizal species.     

Effect of clear-cutting silviculture on soil respiration in a subtropical forest of China

Aims Clear-cutting is a common forest management practice, especially in subtropical China. However, the potential ecological consequences of clear-cutting remain unclear. In particular, the effect of clear-cutting on soil processes, such as the carbon cycle, has not been quantified in subtropical forests. Here, we investigated the response of soil respiration (Rs) to clear-cutting during a 12-month period in a subtropical forest in eastern China.Methods We randomly selected four clear-cut (CC) plots and four corresponding undisturbed forest (UF) plots. Measurements of Rs were made at monthly time points and were combined with continuous climatic measurements in both CC and UF. Daily Rs was estimated by interpolating data with an exponential model dependent on soil temperature. Daily Rs was cumulated to annual Rs estimates.Important findings In the first year after clear-cutting, annual estimates of Rs in CC (508±23g C m ?2 yr^-1) showed no significant difference to UF plots (480±12g C m ?2 yr^-1). During the summer, soil temperatures were usually higher, whereas the soil volumetric water content was lower in CC than in UF plots. The long-term effects of clear-cutting on Rs are not significant, although there might be effects during the first several months after clear-cutting. Compared with previous work, this pattern was more pronounced in our subtropical forest than in the temperate and boreal forests that have been studied by others. With aboveground residuals off-site after clear-cutting, our results indicate that the stimulation of increasing root debris, as well as environmental changes, will not lead to a significant increase in Rs. In addition, long-term Rs will not show a significant decrease from the termination of root respiration, and this observation might be because of the influence of fast-growing vegetation after clear-cutting in situ .     

Soil respiration of forest ecosystems in Japan and global implications

Within terrestrial ecosystems, soil respiration is one of the largest carbon flux components. We discuss the factors controlling soil respiration, while focusing on research conducted at the Takayama Experimental Site. Soil respiration was affected by soil temperature, soil moisture, rainfall events, typhoons, and root respiration. We consider the temporal and spatial variability of soil respiration at the Takayama Experimental Site and review the variability of annual soil respiration in Japanese forests. In the 26 compiled studies, the values of annual soil respiration ranged from 203 to 1,290 g C m⁻² year⁻¹, with a mean value of 669 g C m⁻² year⁻¹ (SD=264, CV=40). We note the need for more studies and data synthesis for the accurate prediction of soil respiration and soil carbon dynamics in Japanese forests. Finally, several methods for measuring soil respiration rates are compared and the implications of soil respiration rates for global climate change are discussed.