【作者】 侯琳；

【导师】 雷瑞德；

【作者基本信息】 西北农林科技大学 ， 生态学， 2009， 博士

【摘要】 秦岭火地塘林区位于秦岭山脉中段南坡,地处亚热带北缘,其地理位置独特、自然条件和地形地貌特殊,植被类型多样,生物多样性丰富,是研究过渡区森林生态系统结构与功能的重要地区。天然次生油松林是秦岭中山地带的典型林分之一,在涵养水源、固定CO2、维持生物多样性等方面发挥着重要作用。为精确估计秦岭火地塘林区天然次生油松群落的碳收支,采用TOC-VTH-2000A型TOC分析仪测定了油松群落内主要乔、灌木树种和草本不同器官的含碳率及林地土壤有机碳含量。其中乔木树种包括油松(Pinus tabulaeformis)、华山松(Pinus armandi)、锐齿栎(Quercus aliena var. acuteserrata)、华北落叶松(Larix principis);灌木包括栓翅卫矛(Euonymus phellomas)、刚毛忍冬(Lonicera hispida pall)、托叶樱桃(Cerasus stipulacea)、白檀(Symplocos paniculata)和披针胡颓子(Elaeagnus lanceolata);草本包括青菅(Carex leucochlora)、野青茅(Deyeuxia sylvatica)、过路黄(Lysimachia christinae)、东亚唐松草(Thalictrum minus)、野棉花(Anemone vitifolia)、茅莓(Rubus parvifolius)、变叶风毛菊(Saussurea mutabilis )、黄腺香青(Anaphalis aureopunctata)、穿龙薯蓣(Dioscorea nipponica)、茜草(Rubia cordifolia)、华北鳞毛蕨(Dryopteris laeta)与羽裂华蟹甲草(Sinacalia tangutica);通过已有的乔木生物量模型,新建的灌木生物量模型和分层抽样技术,分别估算了乔、灌、草不同器官CO2年固定量和林地土壤碳密度;采用红外线动态开路气室法,连续、定位测定了林地土壤CO2释放动态,研究结果如下:(1)不同植物种与植物不同器官的含碳率明显不同,不同测定方法获得的植物器官含碳率值也存在一定差异。在相同生物量下,以实测含碳率和0.45作为乔木的平均含碳率,对油松的干、皮、枝、叶,锐齿栎的枝,华北落叶松的皮、枝和叶的碳密度估算值有显著影响;而以实测含碳率和以0.50作为植物的平均含碳率,对油松的根,华北落叶松的枝与根的碳密度估算产生显著影响;不同灌木同一器官和同一灌木不同器官的含碳率存在显著差异。不同灌木同一器官平均含碳率差值最高达10.58%,同一灌木不同器官平均含碳率差值最高达6.47%;林下草本不同草种同一器官和同一草种不同器官的含碳率构成的种对,多存在显著或极显著差异。不同草种茎与茎、根与根的平均含碳率差值最高分别达14.46%和26.06%;同一草种叶与茎,茎与根及叶与根,平均含碳率的差值最高分别达11.31%,16.83%和19.86%。本研究测定的乔木树种不同器官含碳率与国内学者采用ElementarVario EL有机元素分析仪测定的结果相差3.65%～9.39%。为使不同研究区的资料可相互比较,统一测定仪器和测定方法是今后森林生态系统碳平衡研究中亟待解决的问题之一。(2)本研究表明起测胸径以下(DBH<5cm)的乔木及乔木根系碳密度,分别占2006年和2007年乔木层碳密度的12.68%与16.10%和23.140%与16.801%;林下灌木和草本的CO2固定量分别占2006年和2007年年际间整个植被层CO2固定量的22.49%和13.48%;若不计起测胸径以下乔木、灌木和草本的固碳作用,本区的天然次生油松将演变为明显的“碳源”,碳汇强度高达-20.947 Mghm-2y-1～-20.730 Mghm-2y-1。本研究根据野外实测资料建立了油松群落内主要灌木测树因子与其器官生物量的回归模型,统计检验和误差分析表明,回归模型均具有较高的估计精度和较好的适用性。(3)本研究基于分层抽样技术,在可靠性为95%,相对误差为±11.13%时,研究区40cm以内土层,林地土壤有机碳密度估计值为60.492±6.73 Mghm-2。根据不同学者对中国森林土壤有机碳密度估计结果,研究区土壤有机碳密度则分别占全国同类林地碳密度的33.64%和90.67%。2007年,林地土壤的碳密度占整个生态系统碳密度的64.92%。(4)本研究结果显示土壤呼吸速率与0-20cm的土壤颗粒组成有较高的相关性,并与0-10cm的砂粒含量呈正相关关系而与粘粒含量呈负相关关系,且相关性达到显著性水平。观测期内,土壤呼吸速率与一定范围内的土壤温度呈极显著指数关系,但土壤呼吸速率与土壤体积含水率的变化间关系复杂。植物生长季0～5cm和5～10 cm土层的土壤体积含水率虽与土壤呼吸速率间存在指数关系,但回归方程的决定系数不高(R20-5=0.440, R25-10 =0.521),植物休眠季土壤体积含水率与土壤呼吸速率无明显的回归关系。根据建立的0-5 cm和5-10 cm土层,土壤温度与土壤呼吸速率的指数方程,植物生长季与休眠季0～5cm和5～10 cm土层,Q10分别为1.083与1.094和1.297与1.323;植物生长季土壤CO2释放量为33.326±0.400 Mghm-2y-1和33.307±0.166 Mghm-2 y-1(α=0.05),植物休眠季土壤CO2释放量为9.972±1.057 Mghm-2y-1和9.774±1.772 Mghm-2y-1(α=0.05);植物休眠季土壤CO2释放量占全年土壤CO2释放量的22.69%～23.03%。试验地不同观测部位土壤呼吸速率表现出较大的空间变化,不同观测部位土壤呼吸速率变异系数大于42%;全年土壤日均和月均呼吸速率总体表现为夜间和生长季土壤呼吸速率分别大于白天和休眠季。森林环境的复杂性和冬季低温制约了观测仪器的正常运行,阻碍了土壤呼吸速率野外测定,但冬季林地土壤CO2释放量在林地全年土壤CO2释放中占有较大比重,改进观测仪器运行条件,以便进一步提高土壤呼吸速率的测定精度。不同季节不同土层深度,Q10值各异,把影响Q10值的因素综合考虑于相关模型中,以便准确定量估计土壤呼吸总量,同时由于土壤呼吸速率的空间变异较大,保证足够数量的观测样本有利于土壤CO2年释放量估计精度地提高,深入研究Q10值具有较大变异性的原因和内在机理,以便更好的表征生态系统组分对全球变暖的敏感性。(5)基于研究区2006～2007年植被层的CO2的净固定量和林地土壤CO2释放量研究,研究区天然次生油松林表现为碳汇,碳汇强度为1.783～2.000 Mghm-2y-1。与相关研究的结果相比,研究区天然次生油松林的年碳净收支与樟子松林接近,但其不仅小于落叶松林,云冷杉林,阔叶红松林,温性针叶林、暖性针叶林,针叶、针阔混交林,落叶阔叶林,硬叶常绿阔叶林,常绿阔叶林和热带林的年碳净收支量,而且远小于这些林分年碳净收支量的加权平均值,因此,研究区天然次生油松林表现为很弱的“碳汇”。(6)本研究结果表明不同植物种和植物器官的含碳率差异较大,在本区实施造林和再造林项目时,应选择含碳率较高的植物种;在以固碳为目的的林分经营中,应根据植物器官含碳率的差异采取不同的经营措施;林下植被有较高的固碳作用,在林分抚育中应根据林下植被的生物学特性对上层木采取必要的抚育措施,以便为林下植被提供适宜生境。同时应以“近自然”经营理论为指导,保留固碳量较高的灌、草种,切忌烧荒和全砍林下灌木,从而造成林下植被固碳量降低;本研究建立了土壤温度与土壤CO2释放量的回归方程,在基线设定和预测未来林分的固碳量时,除考虑林火、雷电、干旱、泥石流、林木生长量和人为因素等诸多因子对林分固碳量的影响外,还应考虑林地CO2释放,以期获得较高的经济回报。更多还原

【Abstract】 Huoditang forest zone is on the south slope, located in middle region of the Qinling Mountains and north margin of subtropical zone. It is a vital region to study on structure and functions of forest ecosystem in ecotone for its special geographical position, unusual conditions, diverse vegetation types and abundant biodiversity. The natural secondary Pinus tabulaeformis forest is one of the typical forest types in middle region of the Qinling Mountains which plays important roles in water conservation, carbon dioxide sequestration and biodiversity maintenance.To estimate carbon budget of P. tabulaeformis community accurately, the instrument of TOC/TON analyzer (TOC-VTH-2000A, Shimadzu Corporation, Japan) was used to measure carbon content ratio (CCR) of arbor, shrub and herbage organs, respectively. The species included P. tabulaeformis, Pinus armandi, Quercus aliena var. acuteserrata, Larix principis, Euonymus phellomas, Lonicera hispida pall, Cerasus stipulacea, Symplocos paniculata, Elaeagnus lanceolata, Carex leucochlora, Deyeuxia sylvatica, Lysimachia christinae, Thalictrum minus, Anemone vitifolia, Rubus parvifolius, Saussurea mutabilis, Anaphalis aureopunctata, Dioscorea nipponica, Rubia cordifolia, Dryopteris laeta and Sinacalia tangutica. Organic carbon content of soil was also analyzed. Carbon density and CO2 sequestration of arbor, shrubs and herbs was estimated by occurred biomass functions, newly established equations and stratified sampling technique, respectively. Carbon dioxide efflux from forest land was continuously and stably measured by means of open-path dynamic chamber technique. The findings are following.(1) CCR among variant plant species and which in the same plant species between their organs was diverse and differed from variant instruments.The significant differences of carbon storage (CS) computing from stems, bark, branches and leaves of P. tabulaeformis, branches of Q. aliena var acuteserrata, bark, branches and leaves of L. principis would be occurred when measuring values and 0.45 were taken as mean CCR of plants under the same biomass. The similar result would also appear in roots of P. tabulaeformis, branches and roots of L. principis as estimating CS with measuring values and 0.50 being mean CCR of plants. The significant differences of CCR still existed among different shrub and herb species and their organs. The most difference of mean CCR of the same organ among different shrub species and variant organs in the same shrub species was 10.58% and 6.47%, respectively. The similar phenomena occurred in herb species. The gap of CCR was 14.46 % (stem to stem) and 26.06% (root to root) in the same organ of diverse shrub species, respectively. For the same shrub species, the disparity of CCR was 11.31% (leaf to stem), 16.83% (stem to root) and 19.86% (root to leaf), respectively.CCR values from reported result by instrument of Elementar Vario EL (Germany) was 4.06%, 6.55%, 9.39%, 5.78% and 4.85% more than ours in root and bark of P. tabulaeformis and L. principis, leaf of Q.aliena var acuteserrata, respectively. But which in root of Q.aliena var acuteserrata was less 3.65% than ours. To compare data from different areas easily in study forest ecosystem carbon balance, the emergent issue is to unify instrument and measuring method.(2) We suggested carbon density (CD) of arbors with DBH <5cm was 12.68% (in 2006) and 16.10% (in 2007) of the total CD in arbor layer, respectively. The carbon dioxide sequestration (CDS) in shrub and herbage layer was 22.49% and13.48% of which in the whole vegetation between 2006 and 2007, respectively. Provided that CDS of understory forest vegetation and CD of arbors with DBH <5cm were neglected, the natural secondary P .tabulaeformis community in experimental area would change into“carbon source”and its carbon sink strength would be -20.947 Mghm-2y-1 to -20.730 Mghm-2y-1.The report of equation regressed among biomass and indices (DBH, height and crown diameter) of shrub species was scarce. Basis on data in field, we established models of organ biomass with DBH, height and crown diameter of mian shrub species in P. tabulaeformis community. The results of statistical test and error analysis demonstrated that the models had higher accuracy and better applicability. But no model could be suitable to describe relationship among organ biomass and their growing indices of fasciculate shrub species (such as Rosa swginzowii, etc.).(3)Basis on stratified sampling method, soil organic carbon density (SOCD) in depth of 40cm in experimental area was estimated as 60.492±6.73 Mghm-2 under the accuracy of 95% with relative error value±11.13%. Due to uncertain mean value of SOCD in national evergreen coniferous forest from literature in China, SOCD in experimental area was 33.64% and 90.67% of the national average value, respectively. SCOD was 64.92% of which in the whole forest ecosystem in 2007.(4) To some extent, soil mechanical and physical properties related to soil respiration in 0-20cm depth in our findings. Moreover, soil respiration rate positively and negatively related to content of gravel and cosmid in 0-10cm depth.During measuring period, significant exponential relation occurred between soil respiration rate and soil temperature in some scale. Relationship between soil respiration rate and soil volumetric moisture was pretty complex. An exponential relation between soil respiration rate and soil volumetric moisture with small determination coefficient (R20-5=0.440, R25-10 =0.521) in growing period. During dormant period, no function could be fit to show relationship between soil respiration rate and soil volumetric moisture.Basis on exponential models regressed by soil respiration rate and soil temperature in depth of 0-5 cm and 5-10 cm, adding to field measurement beyond proper temperature for models, the soil CO2 efflux estimating value was 33.307±0.166 Mghm-2y-1 to 33.326±0.400 Mghm-2y-(1α=0.05)in growing period and 9.774±1.772 Mghm-2y-1 to 9.972±1.057 Mghm-2y-1(α=0.05)during dormant period, respectively. Soil CO2 efflux during dormant period was 22.69% to 23.03% of total soil CO2 efflux in the whole year.In different position on the slope in experimental area, soil respiration rate revealed more special variance and its C.V (coefficient of variance) was more than 42%. The general trend that soil respiration rate at night and during growing period was generally more than which during daytime and dormant period.Hindered by low temperature in winter and complex environmental conditions in forest, soil respiration data in winter could hardly be obtained, but much effort should be paid on improving method and instrument to observe soil respiration during winter in the near future. Values of Q10 varied in periods and soil depth. Seeking for inherent factors and mechanism of Q10 value varying greatly will help to reveal sensitivity of components of ecosystem to global warming.(5) Basis on CD of vegetation and soil CO2 efflux, the natural secondary P. tabulaeformis forest in experimental area showed as a carbon sink and its carbon sink strength was 1.783-2.000 Mghm-2y-1 between 2006 and 2007. Comparing similar findings to ours, CO2 sequestration in the natural secondary P. tabulaeformis forest in experimental area almost euquals to Pinus sylvestnis var. mongolica forest, but our findings is less than L. principis forest, spruce-fir forest, broad-leaved Korean pine forest,temperate coniferous forest, coniferous forest, coniferous and broad-leaved forest, deciduous broad-leaved forest, sclerophyllous evergreen broad-leaved forest, evergreen broad-leaved forest ,tropical forest and even less than their weighted average value. P. tabulaeformis forest in experimental area demonstred weak carbon sinks.(6)We found great differences of CCR occurred among plant species and their organs. Plant species with high CCR should be chosen in the process of foresting and reforesting here. Variant management measures according to CCR differences of plant organs must be adapted to cultivated forest for high CO2 storage. Due to high CO2 storage in understory forest vegetation, proper management measures should be taken to arbors basis on biological traits of shrub and herb species so that appropriate niche could be provided for shrub and herb species. Moreover, measures as burning and clear-cut must be abandoned. We broached models of soil respiration rate and soil temperature in some temperature scale. To get high benefit from forest CDM (clean development mechanism) projects, soil CO2 efflux should be taken into account besides factors, such as, fire , thunder , drought , debris flow , individual growth and artificial interference when baseline is enacted and future forest CO2 storage is predicted.更多还原