Subtropical forest macro-decomposers rapidly transfer litter carbon and nitrogen into soil mineral-associated organic matter

Background:Forest soils in tropical and subtropical areas store a significant amount of carbon.Recent framework to assess soil organic matter(SOM)dynamics under evolving global conditions suggest that dividing bulk SOM into particulate and mineral-associated organic matter(POM vs.MAOM)is a promising method for identifying how SOM contributes to reducing global warming.Soil macrofauna,earthworms,and millipedes have been found to play an important role in facilitating SOM processes.However,how these two co-existing macrofaunae impac the litter decomposition process and directly impact the formation of POM and MAOM remains unclear.Methods:Here,we set up a microcosm experiment,which consisted of 20 microcosms with four treatments earthworm and litter addition(E),millipedes and litter addition(M),earthworm,millipedes,and litter addition(E+M),and control(only litter addition)in five replicates.The soil and litter were sterilized prior to beginning the incubation experiment to remove any existing microbes.After incubating the samples for 42 days,the litte properties(mass,C,and N contents),soil physicochemical properties,as well as the C and N contents,and POM and MAOM^(13)C abundance in the 0–5 and 5–10 cm soil layers were measured.Finally,the relative influences o soil physicochemical and microbial properties on the distribution of C and N in the soil fractions were analyzed Results:The litter mass,C,and N associated with all four treatments significantly decreased after incubation especially under treatment E+M(litter mass:-58.8%,litter C:-57.0%,litter N:-75.1%,respectively),while earthworm biomass significantly decreased under treatment E.Earthworm or millipede addition alone showed no significant effects on the organic carbon(OC)and total nitrogen(TN)content in the POM fraction,but join addition of both significantly increased OC and TN regardless of soil depth.Importantly,all three macrofauna treatments increased the OC and TN content and decreased the^(13)C abundance in the MAOM fraction.More than65%of the total variations in the distribution of OC and TN throughout the two fractions can be explained by a combination of soil physicochemical and microbial properties.Changes in the OC distribution in the 0–5 cm soi layer are likely due to a decrease in soil pH and an increase in arbuscular mycorrhizal fungi(AMF),while those in the 5–10 cm layer are probably caused by increases in soil exchangeable Ca and Mg,in addition to fungi and gram-negative(GN)bacteria.The observed TN distribution changes in the 0–5 cm soil likely resulted from a decrease in soil pH and increases in AMF,GN,and gram-negative(GP)bacteria,while TN distribution changes in the 5–10 cm soil could be explained by increases in exchangeable Mg and GN bacteria.Conclusions:The results indicate that the coexistence of earthworms and millipedes can accelerate the litte decomposition process and store more C in the MAOM fractions.This novel finding helps to unlock the processe by which complex SOM systems serve as C sinks in tropical forests and addresses the importance of soil mac rofauna in maintaining C-neutral atmospheric conditions under global climate change.

Soil seed banks along elevational gradients in tropical, subtropical and subalpine forests in Yunnan Province, southwest China

Soil seed banks are a vital part of ecosystems and influence community dynamics and regeneration.Although soil seed banks in different habitats have been reported, how soil seed banks vary with elevational gradients in different climatic zones is still unknown. This paper investigates seed density,species composition and nonconstituent species of forest soil seed banks in Yunnan Province, southwest China. Similarity between the soil seed bank and standing vegetation was also examined. We collected soil samples from sites spanning 12 elevations in tropical rain forests, subtropical evergreen broadleaved forests and subalpine coniferous forests, and transported them to a glasshouse for germination trials for species identification. The soil seed banks of tropical and subtropical forests had much higher seed densities and species richness than those of subalpine forests. Seeds of woody species dominated the soil seed banks of tropical and subtropical forests, while herbs dominated those of subalpine forests.The nonconstituent species in the soil seed banks were all herbs and were most abundant in tropical forests, followed by subtropical forests but were completely absent from subalpine forests.

Aboveground biomass stocks of species-rich natural forests in southern China are influenced by stand structural attributes,species richness and precipitation

Forests,the largest terrestrial carbon sinks,play an important role in carbon sequestration and climate change mitigation.Although forest attributes and environmental factors have been shown to impact aboveground biomass,their influence on biomass stocks in species-rich forests in southern China,a biodiversity hotspot,has rarely been investigated.In this study,we characterized the effects of environmental factors,forest structure,and species diversity on aboveground biomass stocks of 30 plots(1 ha each) in natural forests located within seven nature reserves distributed across subtropical and marginal tropical zones in Guangxi,China.Our results indicate that forest aboveground biomass stocks in this region are lower than those in mature tropical and subtropical forests in other regions.Furthermore,we found that aboveground biomass was positively correlated with stand age,mean annual precipitation,elevation,structural attributes and species richness,although not with species evenness.When we compared stands with the same basal area,we found that aboveground biomass stock was higher in communities with a higher coefficient of variation of diameter at breast height.These findings highlight the importance of maintaining forest structural diversity and species richness to promote aboveground biomass accumulation and reveal the potential impacts of precipitation changes resulting from climate warming on the ecosystem services of subtropical and northern tropical forests in China.Notably,many natural forests in southern China are not fully stocked.Therefore,their continued growth will increase their carbon storage over time.

The tropical-subtropical evergreen forest transition in East Asia:An exploration

The transition from tropical to subtropical(warm temperate)evergreen forests is more clearly apparent in East Asia,fromNepal to the western Pacific coast,than elsewhere in the tropics.We review the nature of this transition and hypothesize the physical,ultimately climatic,factors thatmay maintain it,with a special focus on how the increasing instability and warming of climates will affect these forests.A primary climatic mediator of the transition is proposed,thereby offering a testable hypothesis for the climateeforest transition relationship.What is known of this transition is summarized in context of the primary climatic mediators of elevational zonation of forest formations in equatorial Asia to the tree line,in the Himalaya at the India-Indo-Burma northern tropical margin,and as both elevational and latitudinal zonation in southern China.Consequent secondary edaphic and other physical changes are described for the Himalaya,and hypothesized for southern China.The forest ecotones are seen to be primarily defined by tree floristic change,on which account changes in structure and physiognomy are determined.The montane tropical-subtropical transition in the Himalaya is narrowand observed to correlate with an as yet ill-defined frost line.A distinct tropical-subtropical transition forest is recognized in the southwest Chinamountains.There is a total change in canopy species at the Himalayan ecotone,but subcanopy tropical species persist along an elevational decline of c.400 m.The latitudinal transition in South China is analogous,but here the tropical subcanopy component extends north over ten degrees latitude,albeit in decline.The tropical-subtropical transition is uniquely clear in East Asia because here alone a tropical wet summer-dry winter monsoon extends to 35
north latitude,encompassing the subtropical evergreen forest,whereas subtropical evergreen forests elsewhere exist under drier temperate summer climate regimes.

Litterfall seasonality and adaptive strategies of tropical and subtropical evergreen forests in China

Tropical and subtropical evergreen broad-leaved forests(EBFs)and needle-leaved forests(ENFs)in China exhibit complex leaf shedding strategies in responses to soil water availability,vapor pressure deficits(VPDs)and sunlight availability.However,the seasonal variations and triggers of litterfall differ significantly in tropical/subtropical forests,and there are still many uncertainties.Herein,we aim to explore the distinct climatic factors of seasonal litterfall in a climate–phenology correlation framework.We collected seasonal litterfall data from 85 sites across tropical/subtropical China and used linear correlation coefficients between sunlight and rainfall to partition synchronous/asynchronous climates.Additional phase analysis and structural equation model analysis were conducted to model the climatic triggers of tropical phenology.Results indicated two types of tropical litterfall phenology under two types of climates.In synchronous climates,where seasonal sunlight and rainfall are positively correlated,the litterfall peak of the unimodal phenology and the first litterfall peak of the bimodal phenology both happen at the end of dry season.The second litterfall peak of the bimodal phenology occurs at the end of rainy season due to water stress.In asynchronous climates,where seasonal sunlight and rainfall are negatively correlated,VPD shows consistent seasonal variations with incoming sunlight.The leaf senescence is accelerated at the end of dry season by higher VPD;while soil water deficit is in anti-phase with sunlight and mainly controls the second litterfall peak of the bimodal phenology in EBF.Our findings provide an important reference for modeling tropical phenology in Earth system models.

南岭国家级自然保护区地上粗木质残体质量估算模型构建

为了更好地支撑广东南岭国家级自然保护区以及附近森林生态系统碳储量和碳汇估算,研究采用广东南岭国家级自然保护区海拔400~1800 m之间阔叶林和针阔混交林中采集的300个粗木质残体(Coarse wood debris,CWD)样品,以分解等级和体积参数为自变量构建CWD质量估算模型。CWD样品平均直径3.332~5.919 cm,平均长度1.55~2.80 m,平均密度0.150~0.224 g·cm^(-3)。尽管直径、长度和密度在个体和样地之间的差异较大,但总体上不随海拔和森林类型而变化,代表性较好。CWD分解等级对样品特征有显著影响,样品密度随分解等级增加而下降。建立的模型拟合度高,分解等级和体积参数均能有效解释CWD质量变化。

2021-2022年广东南岭站日尺度气象数据集

南岭森林生态系统的山地森林及生物多样性生态功能区是我国25个重点生态功能区之一,覆盖包括亚热带常绿阔叶林、针阔叶常绿混交林、山顶常绿阔叶矮林等多种森林植被类型。亚热带常绿阔叶林作为南岭山地最典型植被类型,对其群落气象要素进行监测有助于探索亚热带常绿阔叶林对气候变化的响应机理。本研究依托广东南岭森林生态系统国家野外科学观测研究站(简称“南岭站”)在广东南岭国家级自然保护区开展定位研究。本研究将南岭站2021-2022年亚热带常绿阔叶林区内连续采集的10 min平均风速、降水量、气温、气压、太阳辐射(总辐射、反射辐射、紫外辐射、净辐射、光合有效辐射)、相对湿度的原始数据,经过数据处理、质量控制和评估,以日尺度公开。本数据集的建立和公开共享,可为进一步认识南岭山地森林生态系统提供数据支撑,为森林生态系统修复和保护提供理论参考。

Composition, diversity and distribution of tree species in response to changing soil properties with increasing distance from water source – a case study of Gobind Sagar Reservoir in India

Construction of big dams on rivers develops artificial lakes or water reservoirs which conceive alterations in soil properties of the upstream catchment area. An undulating topography and freckly soil properties cause ups and downs in tree diversity, composition and distribution. The study aimed to evaluate the effect of Gobind Sagar reservoir on soil properties relative to the distance from it and assess its effect on tree diversity, evenness and their distribution in tropical and subtropical forests. Based on data analysis it was found that the soil moisture and organic carbon decreased along with increasing distance from the reservoir. It played a significant role in varying tree diversity. The sites distributed within0-2 km showed significantly higher α and β-diversity indices. Tree species richness and diversity indices showed a strong correlation（p ＆lt; 0.05） with soil moisture and organic carbon content. Simpson＇s and Mc Intosh evenness indices showed a strong negative correlation with soil bulk density. Indirect Detrended Correspondence Analysis（DCA） identified soil moisture and soil organic carbon as two major environmental gradients that influenced tree diversity and their distribution in five tropical and four subtropical forests in an upstream catchment of the reservoir. Mixed forests inhabited moist sites andAcacia-Pinus forests showed an inclination to dry areas. Canonical Correspondence Analysis（CCA）revealed that the tree species in tropical forests were mainly affected by driving forces such as soil moisture,organic carbon and bulk density whereas, in subtropical forest tree species were influenced by elevation, soil p H, EC and clay content.

雪灾对哀牢山中山湿性常绿阔叶林木质藤本幼苗更新的影响

为探讨雪灾对木质藤本幼苗更新的影响,研究了雪灾前后,云南哀牢山中山湿性常绿阔叶林木质藤本幼苗的组成、物种多样性与多度的变化、多度与冠层光照指数的关系。雪灾前(2014年)后(2016年)分别在林内设置20个4 m×4 m的样方,调查样方内木质藤本幼苗(高度或长度≤50 cm)的种类、数量、基径,并测定冠层光照指数。结果表明:①雪灾前后的木质藤本幼苗分别为502株(17种)、1022株(25种);木质藤本幼苗在雪灾前(2014年)的优势种为耐荫种,雪灾后(2016年)的优势种除了葡萄酸藤子外均为喜光的物种;②木质藤本幼苗在雪灾后(2016年)的多度、物种丰富度显著高于雪灾前(2014年)。在11种最常见木质藤本幼苗物种中,雪灾后(2016年)5个喜光种的多度显著高于雪灾前(2014年),而其他6个耐荫种的差异性不显著;③雪灾前后的冠层光照指数从1.58增加到2.88(t=-5.394,p<0.05),木质藤本幼苗的多度与冠层光照指数呈显著正相关(r=0.956,p<0.01)。

亚热带常绿落叶阔叶混交林木本植物生物量模型meta分析

【目的】对亚热带常绿落叶阔叶混交林木本植物生物量模型进行汇编与分析,获悉基于样地调查的植物名录中生物量模型现状,为研究者开展生物量计算与评估提供参考,从而为完善该类森林木本植物生物量模型的研究提供方向,为制定统一的生物量建模标准提供借鉴。【方法】根据在鄂西南3个自然保护区和1个国有林场的常绿落叶阔叶混交林内的固定监测样地调查确定物种名录,检索、筛选和整理木本植物生物量模型,并对模型结构、参数和影响模型准确性的因素进行分析。【结果】共获得167组665个生物量模型,涉及55科、110属、270种的植物,涵盖了物种名录中455种植物的60%,有182个物种未找到生物量模型;模型集中包含19种自变量形式(主要为胸径D、基径D_(B)、树高H等及其不同组合,如D^(2)H、D_(B)^(2)H)和5类函数形式(幂函数388个、线性函数121个、多项式函数73个、对数函数68个、指数函数15个);模型集中的568个模型(85.4%)标注了自变量取值范围,596个模型(89.6%)标注了建模标准木数量,样本数超过30株的生物量模型占比较低(22.3%);559个模型(84.1%)标注了相关系数或决定系数以表征模型准确性,该类系数介于0.17~0.99之间,平均值为0.91;模型自变量、样本量、函数类型、树木不同器官组分和生活型均会对模型的准确性产生影响。【结论】亚热带常绿落叶阔叶混交林木本植物的生物量模型仍存在较大的空缺,且已有的模型存在样本量不足、统计参数不完整等问题,模型的准确性需要考虑样本量、自变量、函数类型等因素带来的影响。

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China

The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve （DNR） In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season （April-September） and with low rates In the cool dry season （October-March）. Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean （± SD） soil respiration rate In the DNR forests was （9.0 ± 4.6） Mg CO2-C/hm^2 per year, ranging from （6.1 ± 3.2） Mg CO2-C/hm^2 per year in early successional forests to （10.7 ± 4.9） Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.

云南哀牢山湿性常绿阔叶林不同密度土壤碳的分布特征

通过调查和对比不同密度土壤碳在亚热带森林生态系统土壤剖面中的垂直分布规律,分析和探讨森林生态系统不同类型土壤在分解、分馏、沉积和保存碳元素方面发挥的重要作用。本研究在云南哀牢山亚热带湿性常绿阔叶原生林生态系统中进行,以上游森林生态系统原生土和下游草地生态系统淤积土为研究土壤类型,采用分层取样的方法,观察土壤剖面中根层土壤(0~45 cm)不同密度有机碳的垂直分布规律,并对比分析土壤碳密度分级法和重铬酸钾氧化法测定土壤全碳含量的差异。研究结果表明:在6个土壤剖面、2种不同类型的土壤剖面中,土壤轻组碳、中组碳、重组碳和全碳均呈衰减式指数分布,且4个测定指标在淤积土土壤剖面的各个土层中的含量明显高于原生土土壤剖面相对应的各个土层中的含量,说明单位体积淤积土在沉积土壤碳方面发挥的作用比原生土要大。在所测定的3种不同密度的土壤碳中,轻组碳含量最低,中组碳次之,重组碳最高,说明大部分土壤碳与矿物质形成团聚体而不能被土壤微生物、土壤动物和植物根系直接利用;3种不同密度土壤碳占土壤全碳的比例数据中,轻组碳和中组碳的比例随着土层深度的增加而减少,重组碳的比例则随着土层深度的增加而增加,说明不同土层在沉积和保存不同密度土壤碳方面发挥的作用有异。本研究成果为全球热带和亚热带森林生态系统不同密度土壤碳在各种不同类型土壤剖面中的沉积速率和储量等方面的研究工作扩展新的调查内容和研究方向。

不同树种对森林土壤可溶性有机碳空间异质性的影响

通过调查同一个森林生态系统不同样地中多个树种根际范围内土壤可溶性有机碳和土壤有机碳的含量,分析和探讨影响森林生态系统土壤可溶性有机碳和土壤有机碳空间异质性的环境因素。本项目在云南哀牢山亚热带中山湿性常绿阔叶原生林生态系统中进行,选择3个山谷样地上游森林生态系统原生土区域中7个主要树种作为研究对象,调查0~10cm表层土壤可溶性有机碳和土壤有机碳的含量。研究结果表明:硬壳柯、变色锥、木果柯、多花山矾和南洋木荷等5个乔木树种根际范围内土壤可溶性有机碳和土壤有机碳含量显著高于云南连蕊茶和云南越桔2个灌木树种根际范围内土壤可溶性有机碳和土壤有机碳含量;5个乔木树种中硬壳柯和南洋木荷2个树种根际范围内土壤可溶性有机碳和土壤有机碳含量明显大于另外3个乔木树种,说明不同树种对土壤可溶性有机碳和土壤有机碳的空间异质性有明显影响。7个不同树种根际范围内土壤可溶性有机碳含量、土壤有机碳含量和土壤可溶性有机碳含量占土壤有机碳含量的比例在老君山神山谷样地中达到最大值,在三棵树山谷样地中降低为最低值,说明不同山谷样地中的环境条件也可以显著影响土壤可溶性有机碳和有机碳含量及两者之间的比例。本项目研究结果充分证明森林生态系统土壤可溶性有机碳和土壤有机碳空间分布规律的复杂性和环境控制因子的多样性,可为全球各种类型森林生态系统土壤有机碳成分和碳贮量等方面的研究内容提供新的思路和方向。

鼎湖山南亚热带常绿阔叶林植物营养元素含量分配格局研究

在鼎湖山南亚热带常绿阔叶林中，植物叶片营养元素含量为：Ｎ ０．９４６％一２．５３５％，Ｐ ０．０３０％—０．１２７％， Ｋ ０．６１４％—１．８３３％， Ｃａ ０．４４２％—１．９９５％， Ｍｇ ０．０２４％—０．１８８％。叶片各营养 养元素间相关性较差，仅Ｐ与Ｍｇ及Ｍｇ与Ｋ之间存在显著的线性相关。叶片Ｎ元素平均含量在各层 中的序列为：乔木Ⅲ＞乔木Ⅱ＞乔木Ⅰ＞灌木＞藤本＞草本；其它营养元素浓度随层次分配的规律 性不甚明显，但总趋势为乔木层植物略低于其它层植物。不同营养元素平均含量在各器官中的大小排列 顺序为：Ｎ叶＞皮＞枝＞根＞干；Ｐ叶＞枝＞根＞皮＞干；Ｋ叶＞枝＞皮＞根＞干；Ｃａ 皮＞叶＞枝＞根＞干； Ｍｇ叶＞根＞皮＞枝＞干。大部分植物在同一器官中各营养元素平均含 量序列为：叶、枝和根中均为Ｎ＞Ｃａ＞Ｋ＞Ｍｇ＞Ｐ；干Ｋ＞Ｃａ＞Ｎ＞Ｍｇ＞Ｐ；皮Ｃａ＞Ｎ＞Ｋ＞Ｍｇ＞Ｐ。 对元素含量分配格局分析表明，Ｐ和Ｍｇ很可能是限制南亚热带常绿阔叶林植物生产力的最重要营养元 素。

鼎湖山季风常绿阔叶林林下层3种优势树种游离氨基酸和蛋白质对模拟氮沉降的响应

报道了林下层3种优势树种光叶山黄皮(Randia canthioides)、黄果厚壳桂(Cryptocarya concinna)和厚壳桂(Cryptocaryachinensis)叶片游离氨基酸和蛋白质对模拟氮沉降的响应,并探讨这3种植物中重要氨基酸对氮沉降的指示作用,以及γ-氨基丁酸含量的变化对植食性动物的可能影响,为揭示氮沉降对森林植物生理生态影响及其机理,以及监测氮沉降对植被的影响等一系列问题提供初步的理论基础。结果表明,试验21个月后,3个树种叶片游离氨基酸和蛋白质的含量均发生了明显的变化。对总的游离氨基酸含量而言,光叶山黄皮和厚壳桂对氮处理的响应相似,氮处理样地的含量均高于对照,并且中氮处理显著高于对照(p<0.05),但两者在高氮处理下均出现了下降的趋势;黄果厚壳桂随着氮处理强度的增加,游离氨基酸总量呈现下降趋势。对于可溶性蛋白质含量来说,光叶山黄皮、黄果厚壳桂和厚壳桂在氮处理下都出现了增加的趋势,黄果厚壳桂和厚壳桂增加尤为明显。找出了对氮沉降响应敏感的指示剂。游离氨基酸丝氨酸、精氨酸和γ-氨基丁酸,特别是精氨酸,可以用来作为光叶山黄皮对氮沉降响应的指示剂;γ-氨基丁酸可以作为黄果厚壳桂对氮沉降响应的指示剂;丝氨酸和γ-氨基丁酸可以作为厚壳桂对氮沉降响应的指示剂。个别游离氨基酸的积累情况可被用来监测氮沉降对植被的影响。

热带－亚热带森林中猕猴的食性

采用跟踪观察法对热带－亚热带森林中的猕猴种群的食性及其与植被类型的关系进行了调查，结果表明，猕猴主要选择季雨林或次生季雨林为其觅食场所，栖息地植物的地理分布和种类直接影响其食性，猕猴对植物各部位的采食频度随植物生长期而变化．

哀牢山湿性常绿阔叶林木质藤本植物的物种多样性及其与支柱木的关系

分别在哀牢山湿性常绿阔叶林沟谷和坡面调查了10个20m×50m的样地,研究哀牢山湿性常绿阔叶林木质藤本植物的物种多样性及其与支柱木的关系。结果表明:研究区共记录到DBH≥1cm的木质藤本植物402株(隶属于23种21属16科)和DBH≥10cm的林木1522株(隶属于47种30属15科);与其他亚热带森林比较,该森林中木质藤本植物物种较为丰富但多度较低;藤本植物的物种丰富度、密度和基面积在沟谷显著高于坡面,而林木的差异性不显著;木质藤本植物在支柱木上呈集群分布,并且不同种支柱木被藤本植物攀援的百分比间存在显著的差异(P<0.001),说明藤本植物的攀援对支柱木具有选择性;云南越桔、薄叶马银花和景东冬青等树种因其树皮光滑而不易被藤本植物攀援,而腾冲栲、七裂槭、山矾和多花山矾等则易于被藤本植物攀援;大径级支柱木被藤本植物攀援的比率高于小径级支柱木;茎缠绕和钩刺攀援藤本的胸径与支柱木胸径极显著相关(P<0.001),根攀援和卷须攀援藤本的胸径与支柱木胸径相关性不显著(P>0.05)。

珠海凤凰山陆气相互作用与碳通量观测塔的基本观测及晴天主要观测量的日变化特征

珠海凤凰山地处北回归线以南,森林植被覆盖率达90%,植被类型为南亚热带常绿阔叶林群落,是岭南地区典型的城市或村庄周边的再生森林,我们选择在凤凰山麓森林冠层较为平缓的低矮坡地建立了陆—气相互作用和碳通量的观测铁塔塔站。本文详细介绍了观测塔的地理环境、初步的仪器布设和基本观测,并利用已获得的资料分析了旱季典型晴天主要观测量的日变化特征。太阳总辐射及其分光辐射和反射辐射的日变化都是比较常规的中午最高的对称结构;冠层接收到的长波辐射比向上长波辐射低;气温日变化的峰值比太阳辐射滞后,白天达到最高值前的气温是低层高于高层,达到最高值后到落日前气温陡然下降,夜晚的气温是低层低于高层。相对湿度凌晨最大,下午最小,夜晚是低层相对偏湿,白天正好相反;11月份,珠海地区盛行旱季的偏北季风,有明显的海陆风的作用,白天的海风较强,夜晚的陆风较弱;森林冠层向大气释放的感热和潜热的量值基本相当,潜热基本为正;感热白天为正,夜晚基本为负;森林冠层吸收的二氧化碳的最高值出现在午后,此时空气中水汽浓度达到最低,向大气释放的二氧化碳在日出后的清晨最大,此时空气中的二氧化碳浓度达到最大,同时空气密度也最大;由于森林冠层高、密度大,土壤湿度基本没有日变化;表层土壤温度日变化的振幅随土壤深度加深而变小,土壤热流的变化是下午高,清晨低。本文还发现了一些值得深入探讨的现象,需要以后根据充沛的资料分析论证。

广西光皮桦林的分类和演替

光皮桦林是常绿阔叶林或山地常绿落叶阔叶混交林遭受砍伐后，在保护较好的情况下自然恢复起来的一种演替系列群落，属亚热带落叶阔叶林的一种类型。本文通过群落分类研究，划分出３个群丛纲和１１个群丛。从这些群丛的外貌、结构和种类成分的变化，可确定其演替的趋向和所处阶段，是合理经营管理它的科学依据。

南亚热带中幼龄针阔混交林碳储量及其分配格局

以南亚热带中幼龄针阔混交林为研究对象，通过典型样地调查法，对森林生态系统各个层次进行取样调查，采用12个样地实测数据和已有生物量模型相结合的方法计算乔木层生物量，灌木层、草本层和凋落物层采用全部收获法测得其生物量，对土壤层的调查采用剖面法加土钻法，代表性样品碳含量的测定采用重铬酸钾-水合加热法。在此基础上，分析了中幼龄针阔混交林碳储量及其分配格局。结果表明，主要造林树种树根、树杆、树枝和树叶碳含量均值分别为45.07%、46.73%、46.30%和47.72%。植物碳含量表现为乔木〉灌木〉草本。乔木碳储量占植被总碳储量比例介于63.38%-94.08%之间，灌木碳储量所占比例介于3.55%-12.67%之间，而草本碳储量仅介于为1.28%-23.95%之间，不同林龄段乔木和灌木碳储量均值随林龄的增加呈上升趋势，而草本碳储量呈下降趋势。土壤碳储量介于106.73-136.61 t·hm^-2之间，土壤碳储量随林龄的增加呈现出先降低后升高的趋势。针阔混交林总碳储量介于134.79-162.60 t·hm^-2之间，分配格局表现为土壤层〉植被层〉凋落物层。土壤层碳储量所占总碳储量比例范围为78.34%-94.45%，植被层所占比例介于4.84%-20.16%之间，凋落物层仅介于0.71%-1.50%之间，中幼龄针阔混交林碳储量主要以土壤固碳为主。研究结果为树种选择、人工林生态系统固碳潜力以及人工碳汇林的经营管理等研究提供科学参考。