【作者】 沈微；

【导师】 王立海；

【作者基本信息】 东北林业大学 ， 森林工程， 2009， 博士

【摘要】 东北地区森林生态系统因其面积大,碳贮量高而在本地区和我国碳平衡中占有重要的地位。研究森林作业对小兴安岭针阔混交林土壤呼吸的影响,直接影响到本地区和我国的碳平衡和森林经营,因而具有重要的理论和现实意义。本研究采用红外气体分析法测定东北小兴安岭针阔叶混交林择伐、畜力集材、堆积清理和火烧清理等作业方式下,不同样地的土壤表面CO₂通量,利用挖壕法（Trenching plot）区分不同采伐强度下林地土壤呼吸各组分和集材道的异养呼吸,对土壤温度、湿度、林地土壤呼吸、集材道异养呼吸（RH）、迹地枯枝落叶层呼吸的昼夜动态和季节动态进行深入分析,利用模型分析和野外实测相结合的方法探讨采伐强度、土壤压实、堆积清理和火烧对土壤呼吸的影响。结果表明:（1）择伐作业对土壤呼吸的影响。不同采伐强度下,小兴安岭针阔混交林土壤呼吸速率均值范围在0.6-8.2μmol·m^-2·s^-1之间。雨季土壤呼吸明显大于旱季。生长季针阔混交林土壤通量值范围在1.68-18.82mol·m^-2之间,最大值和最小值分别出现在7月和11月。2006年通量为84.37mol·m^-2。不同采伐强度下旱季土壤温度和空气相对湿度对土壤呼吸的影响比在雨季明显。土壤温度和湿度共同解释了林地表面CO₂通量的68.10%-98.9%。结果表明,择伐作业对碳释放扰动不大,并没有破坏森林的固有规律。各组分中CO₂通量与土壤温度和湿度的相关性顺序为枯枝落叶层<根际<矿质土壤。呼吸速率均值与择伐强度相关性顺序为枯枝落叶层>根际>矿质土壤层。枯枝落叶层和矿质土壤层生长季呼吸速率平均值变化趋势较一致,均有较大的增幅,是控制择伐后林地土壤呼吸变化的关键组分。为降低择伐后林地CO₂排放增加速率,应采用中、小强度（52%以下）的择伐进行作业。（2）集材作业对土壤呼吸的影响。各样地土壤受不同干扰程度的压实情况:集材主道>集材支道>林内对照地。集材主道土壤（0-40cm）所受影响程度大于集材支道。经理论模型和实测数据对比,土壤CO₂浓度随着土壤压实程度提高而增大。集材道和对照林地土壤呼吸作用昼夜变化和季节变化皆表现为单峰曲线,且与5cm土壤温度相关性较高,与土壤水分日变化不明显。集材道土壤呼吸速率变幅大于林地。生长季平均土壤呼吸速率分别为2.36和3.22μmol·m^-2·s^-1,集材道土壤呼吸速率约为林地的73%。集材道和针阔叶混交林地的Q₁₀值分别为2.77和2.72。小兴安岭针阔叶混交天然林集材道土壤异养呼吸速率受土壤温度和土壤湿度的共同影响,且集材道样地枯枝落叶层呼吸和无根土壤呼吸速率与土壤温度的相关性均高于土壤湿度。采用双因素关系模型(R=ae^bTW^c),土壤温度和土壤湿度共同解释了不同样地2006年、2007年枯枝落叶层呼吸和无根土壤呼吸速率季节变化的49%-90%和65%-93%,精度高于相应单因素模型。生长季对照林地、集材支道、集材主道无根土壤呼吸速率平均值分别为CO₂ 1.36、1.13和0.94μmol·m^-2·s^-1,变化范围则分别为CO₂ 0.22-2.60、0.35-2.76和0.24-2.45μmol·m^-2·s^-1;枯枝落叶层呼吸速率平均值分别为CO₂ 1.16、1.02和0.93μmol·m^-2·s^-1,变化范围则分别为CO₂ 0.42-2.22、0.28-1.92和0.27-2.31μmol·m^-2·s^-1。集材主道土壤异养呼吸占土壤呼吸的比例最高（82.7%）,对照样地最低（58.4%）。土壤异养呼吸中无根土壤呼吸和枯枝落叶层呼吸所占比例较为接近集材作业使枯枝落叶层呼吸略有降低。（3）迹地清理作业对土壤呼吸的影响。2006、2007年生长季堆积清理样地较对照样地土壤呼吸速率高16%-179%。堆积清理与对照地土壤呼吸和土壤温度都具有显著的指数关系。迹地堆积清理使得Q₁₀值从1.48增加到1.99。迹地堆积清理两年后,迹地堆积清理的样地0-10cm层土壤容重比未清除样地高20%;非毛管孔隙度、毛管孔隙度和土壤总孔隙度均显著减少,而对更深层土壤没有显著影响。采伐剩余物堆积腐烂,由于增加枯枝落叶和林下薪碳材,使得天然林由净碳支出23.62mol·a^-1变为净碳流入43.13mol·a^-1,即堆积清理作业使森林由碳“源”变为碳“汇”。采伐剩余物增加导致了枯枝落叶层分解增加。测定期间土壤呼吸平均值及年呼吸量均升高近1倍。堆积清理增加的枯枝落叶层呼吸是其土壤呼吸显著升高的主要原因。枯落物分解产生CO₂占土壤总呼吸的比例为21%。枯枝落叶层土壤呼吸速率雨季明显高于旱季,且两种处理间土壤呼吸有显著差异。雨季土壤呼吸速率昼夜变化明显,旱季昼夜变幅很小。去除枯落物处理改变土壤呼吸速率与土壤温度的关系,使指数相关因子由0.7219变为0.5621。Q₁₀值分别为2.72和2.96。回归分析表明,去除枯落物处理并没有改变土壤呼吸速率与土壤含水量的相关性。火烧迹地和针阔叶混交林的土壤呼吸作用昼夜变化主要受温度影响,但雨季火烧迹地土壤呼吸速率决定因子被取代土壤水分。火烧迹地土壤呼吸速率日变幅大于林地,另外呼吸速率日变化峰谷值出现时间提前约2-3h。生长季火烧迹地和针阔叶混交林土壤呼吸速率平均值分别为2.8μmol·m^-2·s^-1和3.8μmol·m^-2·s^-1,变化范围分别为0.7－5.58μmol·m^-2·s^-1和1.0－8.7μmol·m^-2·s^-1。用温度指数关系可以分别解释林地和火烧迹地土壤呼吸作用约77%和74%的变异,火烧迹地土壤呼吸速率约为林地的73%。火烧迹地和针阔叶混交林地的Q₁₀值分别为2.25和3.03。本研究在提供东北小兴安岭针阔叶混交林土壤碳贮量和土壤表面CO₂通量的大量实测数据的同时,也提供了一个木材生产作业对森林生态系统土壤呼吸动态影响的研究框架和基本研究方法。研究结果表明森林作业对小兴安岭针阔叶混交林的立地微环境产生影响,进而对土壤碳释放产生影响。因此,在全球气候变化条件下,其碳循环的源汇功能有可能发生变迁,迫切需要对考虑碳吸存的森林经营措施做进一步深入研究。更多还原

【Abstract】 Forest ecosystems in northeastern China play an important role in both local and national carbon budgets because of the large area and huge amount of carbon storage. The study of effects of forest operation on soil respiration in conifer/broad-leaved mixed forests in Xiaoxing’anling directly affects the local and national carbon budgets and forest management. The study has important theoretical and practical meaning. In this study, the infrared gas exchange analyzer （LI-8100） was used to measure C0₂ fluxes on soil surface. Trenching plots were aligned to determine the heterothophic （RH） and autotrphic respiration （R_A） of soil components and on skidding trails under varied cutting intensity, and examine the effects of soil thermal and moisture content on soil respiration and heterotrophic respiration for different treatment, such as selective cutting, tractor or animal skidding, etc. The following results were obtained from this study:（1） Effects of selective cutting on soil respirationUnder different cutting intensity, the soil respiration rates varied from 0.6-8.2μmol·m^-2·s^-1 Higher soil respiration rates were reported in rainy season than the ones in dry season. During growing season, soil carbon fluxes varied from 1.68-18.82mol·m^-2 with the highest in July and the lowest in November. The annual average carbon fluxes was 84.37mol·m^-2 for the year of 2006.Under different cutting intensity, soil temperature and air humidity had more significant effects on soil respiration in dry season while less effect was noticed during rainy season. The comprehensive statistical models of Rs with soil temperature, soil moisture and their interactions as independent variables explained 68.10%-98.9% variations in Rs. It indicated that selective cutting had little impacts on soil carbon effux. The highest correlation between C0₂ flux and soil temperature and moisture was showed in mineral soil, followed by root, then by litterfall. However, the correlation between R and cutting intensity was the strongest in litter, followed by root and mineral soil. Trends of Litterfull respiration and mineral respiration are the same, both of them have large increase. They are the important part to control total respiration after cutting. In order to reduce C efflux, we should choose small intensity or middle intensity.（2） Effects of skidding operation on soil respirationThe sequence of different compaction is main skidding road> small skidding trail>control field. Main skidding road have more influence than small skidding trail. Soil CO₂ concentration became bigger as increase of the soil compaction in comparison of theoretical model to field data. The curve has a high dot that stand by the diurnal and seasonal variations of soil respiration. Soil temperature at 5cm deep did significantly on soil respiration, but soil moisture not. The skidding road soil has bigger variance than the control field. The average CO₂ flux of skidding road and control field are 2.36 and 3.22μmol·m^-2·s^-1. The propoty of skidding road CO₂ flux is 73% by the control field. The temperature sensitivity coefficient of soil respiration (Q₁₀) for the skidding road and control fields are 2.77and 2.72.Soil temperature and soil moisture affect soil respiration effux. Soil temperature is more important than soil moisture. By the mode of R=ae^bTW^c, soil temperature ,soil moisture and their interactions as independent variables explained 49%-90% variations in R_L.and 65%-93% variations in R_M.The modle is better than the oneonly includding soil temperature or soil moisture. In the growing season, the average soil littefull respiration flux are CO₂l.36、1.13 and 0.94μmol·m^-2·s^-1, varied from CO₂ 0.22-2.6、0.35-2.76 and 0.24-2.45μmol·m^-2·s^-1；and the soil minaral respiration are CO₂ 1.16、1.02和0.93μmol·m^-2·s^-1, varied from CO₂ 0.42-2.22、0.28-1.92 and 0.27-2.31μmol·m^-2·s^-1 in the main skidding road, small skidding trail and control field.The heterothophic respiration of main skidding road is highest, 82.7%,and the control field is lowest, 58.4%.R_L and R_M are almost equal prpperty in the R_H.And skidding operation make soil litterfull respiration flux lowerand the control field.（3） Effects of slash disposal on soil respirationIn 2006 and 2007, soil respiration in cumulated cleaning higher 16%-179% than control field.Soil temperature has significantly exponent relationship with cumulated cleaning field and control field. Q₁₀ value add to 1.99 from 1.48. 0-10cm The soil physical propoty in cumulated cleaning field have more effect than forest fields. Because added cutting surplus, make forest -23.62mol·a^-1 to 43.13mol·a^-1C, this is better to forest C operation.CO₂ come from litterfall is 21% to all the soil respiration.It’s higher in rainy season than in dry season,and they have big disparity. Soil respiration varies fast and big in rain season. Getting off the litterfall change the relationship of R-T, make R² to the 0.5621 from 0.7219.Q₁₀ are 2.72 and 2.96.And Getting off the litterfall did not change the relationship of R-W.Soil temperature conthol soil respiration diurnal change. And in rainy season, soil moisture takeover temperature.R change bigger than control fields and the extreme value are ahead 2-3 h. the average soil respiration flux are CO₂ 2.8 and 3.8/μmol·m^-2·s^-1, varied from 0.7-5.58μmol·m^-2·s^-1 in fired field and 1.0-8.7μmol·m^-2·s^-1 in the control field.Temperature can explain the variation 77% and 74% in fired field and control field.Soil respiration in fired field is 73% of control field, Q₁₀ values are 2.25 and 3.03.This study provided a great deal of measured data and reseach framework for the effect of forest operation to belowground carbon pool and flux in representative forest ecosystems in northeastern China, and illustrated that soil CO₂ efflux in these ecosystems was affected by wood production operation and the microenvironment. Therefore, the carbon sink/source capacity of those ecosytems may change under global climate change conditions, which emphasized the siginificance and necessity of further studies on this subject.更多还原