【作者】 贾淑霞；

【导师】 王政权；

【作者基本信息】 东北林业大学 ， 森林培育， 2009， 博士

【摘要】 土壤呼吸也称为土壤表面CO₂通量（Rs）,包括自养和异养部分,是陆地生态系统C循环的一个重要组成部分。土壤微生物呼吸和根系呼吸都对土壤理化性质非常敏感,但是它们的响应机制又不完全相同,而根际分泌物强度直接影响根际C过程。因此,测量土壤呼吸各组成部分对理解森林生态系统碳循环是必要的,尤其是对不同养分（N）条件下土壤呼吸过程更有意义。因此,本研究主要以相同立地条件下落叶松（Larixgmelinii）和水曲柳（Fraxinus mandshurica）人工林为研究对象,主要采用动态红外线气体分析法、离体根系法和室内培养法等测定落叶松和水曲柳人工林林地土壤呼吸速率及其各组成部分,对两种林地分别进行了施肥处理,通过测定对照和施肥林地的土壤呼吸速率、根系呼吸速率和微生物呼吸速率以及土壤理化性质,主要目的是估计根呼吸和微生物呼吸在整个林地土壤呼吸中所占比例,了解两种林分土壤呼吸速率及其组成部分的季节性变化,探讨土壤理化性质、林地施肥处理对土壤呼吸、根系呼吸、土壤微生物（非根际和根际）呼吸的影响。研究结果表明:（1）落叶松和水曲柳根呼吸与细根形态、构型、解剖结构和组织氮浓度具有密切关系。两树种细根呼吸速率随直径和根序的增加而降低,1级直径最细、根呼吸速率最高,5级根直径最粗、呼吸速率最低。因为1级根主要由皮层薄壁细胞构成、组织氮浓度最高,而高级根（如5级根）主要是由此生木质部构成,氮浓度最低,因此呼吸速率低。细根呼吸与温度指数相关。两树种根系呼吸敏感系数Q₁₀的范围为1.66～2.21,各级根系Q₁₀没有显著差异。细根呼吸的季节变化与土壤温度相同。施肥增加了落叶松和水曲柳平均细根系呼吸速率和每个月前3级根系呼吸速率（因为施肥增加细根组织N浓度）,且施肥没有改变两树种各级根序的Q₁₀值。另外,细根呼吸与细根直径、根长负相关,而与比根长正相关。（2）落叶松和水曲柳林地的根际微生物呼吸比非根际呼吸分别高11%和5%,主要因为根际效应引起的,两树种的根际正效应约为10%。落叶松林地的土壤微生物呼吸比水曲柳林地低主要是土壤微生物生物量和数量不同引起的。土壤非根际和根际微生物呼吸具有相同的季节动态格局:夏季最高,秋季最低,与土壤温度季节变化相同。施肥使落叶松和水曲柳林地平均非根际呼吸分别降低13.3%和17.2%,根际呼吸分别降低16.4%和17.5%,因为施肥降低两种林分的土壤微生物量碳、氮和数量。落叶松林地土壤微生物量碳和氮降低24%和63%,水曲柳分别降低51%和68%;土壤细菌、真菌和放线菌数量分别减少98%、63%和61%（落叶松）以及43%、70%和72%（水曲柳）。（3）在所研究的两个林分中,落叶松林地的土壤呼吸比水曲柳林地低。主要是两种林分细根生物量、林地根系呼吸和土壤微生物呼吸都存在差异。土壤呼吸与细根呼吸和土壤微生物呼吸表现出相同的季节变化规律,主要是土壤温度季节变化引起的,因为土壤呼吸速率与土壤温度、湿度、pH显著相关（P＜0.05）,落叶松林地土壤呼吸温度系数Q₁₀（2.34～2.67）明显高于水曲柳Q₁₀（2.73～3.75）。土壤呼吸和土壤微生物呼吸还表现出相同的土层变化:表层高于亚表层（10～20 cm）,主要是表层的土壤微生物量碳和氮高于亚表层,落叶松林分高23.0%和28.0%,水曲柳高34.0%和39.5%。施肥使林分平均土壤呼吸速率显著降低,落叶松降低29.6%,水曲柳降低23.8%,主要是因为施肥降低林地根系生物量和呼吸以及土壤微生物生物量、数量和呼吸。但是,施肥处理并没有引起两个树种林分内土壤呼吸温度系数(Q₁₀)的改变。（4）落叶松和水曲柳林地的根系呼吸和土壤微生物呼吸对土壤呼吸的贡献基本相同,根系呼吸分别占土壤呼吸的30.1%（落叶松）和31.1%（水曲柳）,土壤微生物呼吸分别占土壤呼吸的30.8%（落叶松）和29.2%（水曲柳）。施肥降低林地根系呼吸的比例,施肥处理林地根系呼吸比例分别为27.6%（落叶松）和28.4%（水曲柳）;但是却使土壤微生物呼吸比例加大,落叶松和水曲柳林地分别为38.9%和33.2%。综合分析,落叶松林地土壤呼吸速率及其各组分均比水曲柳低,但是两种林分的土壤呼吸及其各组分表现出相同的季节动态格局。两树种林地根系呼吸占土壤呼吸的30%左右,土壤微生物呼吸30%,两者加起来占土壤总呼吸的60%左右。其他的40%可能的土壤呼吸可能归结于细根生长、离子吸收、粗根和土壤动物呼吸,因为在我们的研究中这几部分的呼吸没有进行估计。施肥降低林地的根系呼吸、土壤微生物呼吸和土壤呼吸,但是没有改变土壤呼吸及其组分的季节变化规律。因此,本研究对进一步认识这两种林分C分配格局与循环过程具有重要意义。更多还原

【Abstract】 Soil respiration（Rs） is the process that soil releases CO₂ to atmosphere（also called soil surface CO₂ flux）,and is the important part of carbon cycling in terrestrial ecosystems.Soil microbial respiration and root respiration showed different response to soil basal physical and chemical properties,and intensity of root exudates directly influenced rhizosphere C flux,so measurement the different components（root respiration and soil microbial respiraion） of soil respiration is critical to learn the carbon cycling of forest ecosystem.Excepisally to make further know the fine root turnover,carbon cost and cycling at stand level.In this study,we measured soil respiration,root respiration,soil microbial（bulk soil and rhizosphere） respiration using infrared gas exchange analyzer（Li-Cor-6400） at fertilized and unfertilized plot of Larix gmelinii and Fraxinus mandshurica plantations which are the same site.At the same time,soil temperature,moisture,organic matter and available nitrogen were measured,main objective was to estimate the contribution of root respiration,soil microbial respiration to soil respiration, so as to learn seasonal dynamic pattern of soil respiration,root respiration,and microbial respiration,as well as to investigate the effect of soil properties and N fertilization on those. The results as follow:（1） Fine root respiration rate were closely related to fine root morphology,anatomy,and tissue nitrogen concentration in L.gmelinii and F.mandshurica plantation.Fine root respiration decreased with the increase of root order,first-order roots showed lowest diameter and highest respiration,while fifth order was opposite to first-order root.Because first-order roots exhibited primary development with an intact cortex,highest tissue N concentration,while higher order（fifth） showed mostly secondary development with lowest tissue N concentration. Fine root respiration rate were closely related to temperature,the range of Q₁₀ in root respiration at two plantations were 1.66～2.21,and Q₁₀ at different branch orders in fertilized plot and control plot were not significantly different.Fine root respiration exhibited seasonal dynamical pattern,which was same to the pattern of soil temperature.N fertilization increased average fine root respiration and that at first third order per month during growth season （because N fertilizer increased root tissue N concenation）.Fine root respiration was negative related to while positive correlation to.（2） Soil rhizosphere respiration was higher 11%and 5%than soil bulk respiration in L. gmelinii and F.mandshurica plantations respectively,for the priming effect of rhizosphere soil. The average rhizosphere effect was 10%in L.gmelinii and F.mandshurica plantations.Soil microbial respiration in L.gmelinii was higher than that of F.mandshurica,main reason was different soil microbial biomass and the number of colony forming units of soil microbes between two plantations.Soil bulk and rhizosphere respiration showed same seasonal dynamical with soil temperature.N fertilizer decreased soil microbial（rhizosphere and bulk soil） respiration.The reduction of soil bulk respiration in L.gmelinii and F.mandshurica plantations were 13.3%and 17.2%,while that of rhizosphere respiration were 16.4%and 17.5%respectively,because N fertilization decreased the average soil microbial biomass and number of colony forming units in two plantations significantly,the reductions of C_mic and N_mic in L.gmelinii plantation were 24%and 63%,and that in F.mandshurica plantation were 51% and 68%respectively,reductions of bacteria,actinomyces and fungi in L.gmelinii plantation were 98%、63%,and 61%,and that in F.mandshurica plantation were 43%、70%,and 72%..（3） Soil respiration was different in L.gmelinii and F.mandshurica plantations.Main reason was the different of fine root repiration,biomass and soil microbial biomass,and respiration between two plantations.Soil respiration showed same seasonal dynamical pattern with soil microbial and root respiration,because soil respiration positive related to soil temperature,Q₁₀ of soil respiration in L.gmelinii（2.34～2.67） was higher than that in F. mandshurica（2.73～3.75）.soil microbial（bulk and rhizosphere） respiration,and soil respiration in surface layer（0～10 cm） were higher than subsurface layer（10-20 cm）,for C_mic and N_mic in surface were higher 23.0%and 28.0%than subsurface in L.gmelinii plantation,and 34.0%and 39.5%in F.mandshurica plantation.N fertilization decreased soil respiration too,soil respiration of fertilized plot was lower than control plot in L.gmelinii plantation（29.6%） and F. mandshurica plantation（23.8%）,main reason were the reduction of root biomass,respiration, soil microbial biomass and respiration.However,the N fertilization did not significantly change the Q₁₀ in two plantations.（4）Contribution of root respiration and soil microbial repiration to soil respiration were nearly same in two plantations.Contribution of root respiration and soil microbial respiration to soil respiration in L.gmelinii plantation was 30.1%and 30.8%,and that in F.mandshurica was 31.1%and 29.2%respectively.N fertilization decreased the ratio of root respiration to soil respiration,contrast to control plot,the ratio in fertilized plot was 27.6%（L.gmelinii） and 28.4%（F.mandshurica） respectively.While N fertilizer increased the contribution of soil microbial respiration to soil respiration in L.gmelinii（38.9%） and F.mandshurica（33.2%） plantations.Overall,root respiration,soil microbial respiration,and soil respiration in L.gmelinii plantation was lower than that in F.mandshurica plantation.While soil respiration,root respiration and soil microbial respiration showed same seasonal dynamical pattern in fertilized and control plot,and contribution of root respiration to soil respiration was about 30%in two plantations,although N fertilization reduced them,contribution of soil microbial respiration was close to 30%and others 40%of soil respiration may be the respiration of fine root growth, corse root and soil fauna which did not measured in our study.The study on root respiration, soil microbial respiration and soil respiration was critical to learn C allociation pattern and process in two plantaions.更多还原