【作者】 董彬；

【导师】 杨玉盛；

【作者基本信息】 福建农林大学 ， 生态学， 2004， 硕士

【摘要】 土壤呼吸是全球碳循环中的一个重要环节，其对全球碳平衡的影响是近年来人们关注的焦点之一。在全球变化的背景下，世界降水分布将发生改变，土壤呼吸也将随之变化，这将对全球的碳循环产生深远的影响。由降雨时间分布不均引发的土壤干湿交替现象是一个重要的生态学过程，但一直没受到重视。为探讨森林土壤呼吸与水分的关系及土壤呼吸对水分的响应机制，我们于2002年1月在福建三明莘口对格氏栲天然林、格氏栲人工林和杉木人工林土壤呼吸、土壤湿度及相关环境因子进行了较为系统研究，同时在室内对野外观测到的干湿交替现象进行模拟。研究结果如下： （1） 野外土壤总呼吸、矿质土壤层呼吸和枯枝落叶层呼吸均与湿度呈线性相关关系，以土壤总呼吸与土壤湿度的相关性最高。不同林分中以格氏栲大然林土壤呼吸与土壤湿度的相关性最高。当土壤温度低于12℃时，土壤呼吸速率较低，此时土壤温度是土壤呼吸的制约因素，与土壤湿度相关性较差：当＜12℃土壤温度＜23℃时，土壤呼吸随土壤温度和土壤湿度的增加而增大：当土壤温度高于23℃时，土壤呼吸随温度的升高而下降，对土壤湿度的响应敏感。当NF、CK和CF土壤湿度分别低于15.39％，14.91％和17.01％时，土壤湿度则成为土壤呼吸的主要因素，此时土壤呼吸与土壤温度相关性较差。 （2） 通过室外定位观测持续干旱后天然降雨及室内模拟不同温度（10℃、19℃和28℃）下的格氏栲天然林、格氏栲人工林和杉木人工林土壤增湿后呼吸动态，发现室外定位观测和室内模拟试验均出现了增湿后土壤呼吸骤升至最大值及随后逐渐衰减的现象，且这种变化可由时间过程模型(R=ate^-bt+c)较好地进行拟合。温度升高提升了土壤呼吸对干湿交替的响应值RV。格氏栲天然林土壤呼吸对干湿交替的响应对温度最为敏感，随温度升高其响应指数RE增加：杉木人工林土壤呼吸对干湿交替的响应指数RE最高，且对土壤水分变化最敏感，但随温度升高超过一定限度后其响应指数RE反而降低。 （3） 在2003年持续干旱状况下向采伐迹地注水后土壤湿度和土壤呼吸速率急剧增加，随后逐渐下降。土壤呼吸和土壤湿度对注水的响应均可用R=a·t·e^-b·t+c较好的拟合。随着注水量的增加，土壤湿度达到最大值所需时间逐渐增加（分别为0.52，0.75，2.56，2.63，2.7天），土壤含水量下降也趋向缓慢。在6个处理中，土壤呼吸最大值、最大值出现时间(t_max)、响应值（RV）和响应值数（RE）均存在显著差异（p<0.05），其中75mm的土壤呼吸最大值、Rv和RE最大。土壤呼吸速率和土壤湿度间的关系相当离散（:2二0.5357），表明了土壤湿度与土壤呼吸相互关系的复杂性。（4）在室内设置了6个土壤含水量梯度进行干湿交替模拟试验（风干土，15%，30 %，35%，40%和45%），发现室内与野外土壤呼吸对干湿交替的响应有相似的 趋势。随着土壤含水址的增加，土壤释放CO:激增的持续时间延长。通过处理 后时间、土壤含水量和土壤类型三因素方差分析和处理后时间、土坡湿度双因 素方差分析，发现土壤湿度对土壤呼吸干湿交替有显著影响。格氏拷人工林土 壤呼吸的最大值、RV值和响应指数既以含水量40%的处理最大（290.52 mg CoZ·g一’5011·d一’，757.50 mg eoZ·g”501一d一，，10.76），而杉木人工林矿质土壤呼吸 的最大值、Rv值和响应指数RE以含水量35%的处理最大（282.43 mg coZ·g一’ 5011·d”，922.84 mg eoZ·g一’5051·d一’，12.53），二者均接近它们的田间持水率。相 对于格氏拷矿质土壤呼吸最大值出现时间，杉木的有明显的滞后现象。矿质十 壤增湿后土壤呼吸速率比干土高7.44¹3.76倍。（5）与矿质土壤呼吸对干湿交替的响应相似，加水刺激了6个含水量梯度的枯枝落 叶呼吸。各水处理间响应值Rv、响应指数RE和最大值均有显著差异（P<0.05）， 卿以杉木未分解枯枝落叶3.0倍处理的最大（一90一55 mg eoZ·g一，litter·d一’），RE 最大值以格氏拷未分解枯枝落叶1.3倍处理的最大（820.44），最大值以格氏拷 半分解枯枝落叶3.5倍处理的最大（364.60 mg eoZ·g-，一stter·d一’），而最大值出现 时间差别不大。格氏拷未分解枯枝落叶、半分解枯枝落叶、杉木未分解枯枝落 叶和半分解枯枝落叶增湿后，最大值分别出现在3.0，3.5，3.0，3.5倍的处理中， 分别是对照的13.46，19.49，巧.51，16.54倍，所处含水量均与它们的最大持水 率接近（分别为200%，266%，206%，259%）。枯枝落叶增湿后比风干枯枝落 叶呼吸的高出5.26¹ 8.49倍。（6）室内模拟不同pH值的酸雨对土壤呼吸均产生抑制作用。随着pH值的降低，土 壤呼吸速率逐渐降低，抑制指数HE逐渐增大。各PH值处理间土壤呼吸存在显著 差异（p<o‘05）。以pH值为2的处理抑制最强，11乎吸速率最低（182一。²25.84 mg eoZ·g一’501一d一‘），对照（无eo:蒸馏水）的呼吸速率最高（302.23一305.88 mg c仇.g’’5011·d一，）。不同pH值的酸雨处理后，格氏拷土壤呼吸迅速下降，而杉 木土壤呼吸在处理后的第二天则稍微增加，然后再下降。格氏拷矿质土壤呼?更多还原

【Abstract】 Soil CO2 efflux in terrestrial ecosystems is an important consideration in the studies of the global carbon cycle, which contribution to the global carbon budget has been the focus of wide concern. Soil respiration is also crucial for figuring out the "missing sink" of carbon. It is absolutely necessary for terrestrial ecosystem soil respiration study to probe into the role of terrestrial ecosystem in source-sink and missing sink about carbon cycle. With global change, worldwide water distribution will alter greatly, and then soil respiration will change significantly, which will in turn impact on global carbon cycle. Although CO2 efflux plays a critical role in carbon exchange between the biosphere and atmosphere, our understanding of its regulation by soil moisture is rather limited. Drying and wetting cycles in forest soils caused by imbalance of precipitation time distribution is an important process, yet have not received much attention, partly due to methodological limitations for nondestructive monitoring of the soil water content. This phenomenon is familiar in surface soils, yet the mechanisms responsible for producing the CO2 pulse have not been positively identified. The objective of this study was to determine the correlation between forest soil respiration and soil moisture and the mechanism of soil respiration response to moisture. From Jan. 2002, soil respiration, soil moisture, soil temperature and other related environmental factors were studied in a natural forest of Castanopsis kawakamii (NF) and adjacent monoculture plantations of C. kawakamii (CK) and Chinese fir (Cimninghamia lanceolata, CF) in Sanming Nature Reserve, Fujian. In addition, a series of examinations were designed to simulate drying and wetting cycles in field and laboratory. The results were showed as follows:(1) The soil respiration in NF, CK and CF showed distinct seasonal dynamics in the field. Soil respiration was highest in July and lowest in January. The order of soil respiration rate in three stands was NF>CK>CF. Similar to soil respiration dynamics, soil moisture showed pronounced fluctuation. The correlations between total soil respiration, mineral soil respiration, litter respiration and moisture were all linear. Among three stands, the correlation between soil respiration and soil moisture was highest for the NF. Soil respiration was lower when soil temperature below 12C, and soil temperature was limiting factor and independent of soil moisture. When soil temperature was in the range of 12C~23C, soil respiration rate increased with increasing soil moisture and soil temperature. Once soil temperature over 23C, soil respiration declined with increasing soil temperature. When soil moisture under 15.39%, 14.91% and 17.01% in NF, CK and CF respectively, soil respiration rate was low and soil moisture became limitingfactor, so in this case soil respiration independent of soil temperature.(2) The effect of soil rewetting on soil respiration was determined in field for NF, CK, and CF and in laboratory at different temperature of 10C, 19C and 28 C with soil rewetting. The research both in the field and the laboratory, showed an increase of soil respiration and a subsequent decline after reaching a maximum following soil rewetting. This process can be simulated with a time model: R=a t e-b t+c. Higher temperature can increase the response value (E). The response of soil respiration to soil rewetting showed the highest sensitive to temperature in NF, the higher response efficiency with higher temperature. Soil respiration in CF had the highest response efficiency and the highest sensitive to soil water content, but temperature has a negative effect on its response efficiency. It was concluded that the positive effect of soil respiration following soil rewetting could contribute to a ignorable part of total soil CO2 efflux on annual basis, because there are high frequency of rain events in the local area.(3) This study was designed to examine the relationship between soil CO2 efflux and soil moisture in a clear-更多还原