【作者】 彭舜磊；

【导师】 由文辉；

【作者基本信息】 华东师范大学 ， 生态学， 2011， 博士

【摘要】 植被—大气界面是水汽和CO2交换的主要场所,该界面交换的水汽和CO2是陆地生态系统水、碳通量的主要组分,而且两者都受到冠层气孔导度的控制,因此冠层气孔导度成为陆地生态系统水碳耦合的主要节点。而冠层气孔导度对于环境因子响应敏感,对冠层水碳通量控制和调节的生态过程是非线性的,如何连续地模拟冠层的水碳通量是一个备受关注的科学问题。本论文选择天童常绿阔叶林为研究对象,于2009年6月-2011年3月,对栲树群落的树干液流、气象及水文要素、冠层叶片同位素以及该林区不同演替阶段的叶片碳同位素及水分利用效率进行了监测和研究,从树干液流与叶片碳同位素耦合的角度,建立了冠层水碳耦合模型,阐明了冠层水碳耦合过程。主要研究结果如下：1 2009年6月—2010年8月,林外总降雨量2316mm,林内穿透雨量、树干茎流量和林冠截留量分别占总降雨量的81.7%、2.3%和16.0%。穿透雨量与冠层叶面积指数、树冠开放度以及降雨因子具有极显著相关关系(P<0.01),树干径流量随树干胸径的增大而增加；林冠截留率与降雨量、降雨持续时间、降雨强度、降雨时间、空气相对湿度均呈极显著负相关(P<0.01),而与风速呈极显著正相关(P<0.01)。2天童常绿阔叶林植被演替,明显提高了0～60cm土壤深度的饱和导水率(Ks)。土壤容重、非毛管孔隙度、有机质含量是影响Ks的主要因子。植被演替到灌丛阶段,Ks均值已显著高于草地,演替到中后期阶段,Ks均值提高迅速,演替至顶极森林Ks均值达到最高(3.28mm min-1)。顶极群落栲树林能够抵御10年1遇的暴雨而不产生地表径流,次顶极群落木荷林能够抵御1年1遇的暴雨,而草地、灌丛和马尾松林等处于演替早期阶段的植物群落容易引发暴雨地表径流。3在栲树群落内,单日(2009年10月6日)单树蒸腾从最小值5.07(g m-2s-1)到最大值84.28(gm-2s-1),相差18倍,树种之间相比,栲树的日平均蒸腾量是木荷的2倍。反映了大小不同的树木个体在群落中对水分利用的差异、贡献和在群落中的功能地位。但是同一胸径级,木荷的树干液流和蒸腾速率较栲树快,因为木荷的气孔比栲树大。胸径较大的树木具有较高的整树蒸腾量,很大程度上归因于它的边材面积大、总液流量高,同时,高大树木在森林中占据空间优势,比其他个体从环境中获得较多的光热资源,这些条件保证了高大树木具有较高的液流量。不同气象环境条件下,栲树和木荷个体树干液流变化差异很大。在晴天,栲树和木荷的树干液流随太阳辐射有规律地变化,日进程曲线很规则,在中雨的天气条件下,栲树和木荷的树干液流值较晴天和多云天气迅速下降,日最大值仅为1.5gm-2s-1；在暴雨的气象条件下(2009年10月1日),栲树和木荷的树干液流降到0～0.5gm-2s-1极低的水平。一年内,栲树和木荷的蒸腾量表现出与季节变化吻合的规律。在11月到次年2月整个冬季,栲树和木荷的树干液流密度和树冠蒸腾量维持在一个很低的水平,3月份之后,树干液流密度开始上升,直到7、8月份,蒸腾量达到最大值,9月份之后开始下降,尤其是10月份以后下降速度非常明显。在诸多环境因子中,光合有效辐射和空气水蒸汽压亏缺是树干液流和蒸腾的主要驱动力。4用水量平衡方法测得的蒸散与用彭曼公式计算的蒸散比较接近,栲树群落的总蒸散占总降雨量的72.1%,土壤贮水变化值占总降雨量的20.2%,径流量仅占总降雨量的6.7%。在总蒸散中,林冠蒸腾量占总蒸散的81.4%,蒸散以林冠蒸腾为主,栲树冠层的蒸腾量最大值为7.2 mmd-1,出现在8月份,最小值为0.52 mmd-1,出现在2月。光辐射和空气水蒸汽压亏缺是影响冠层蒸腾的重要环境因子。栲树群落作为顶极群落具有巨大的拦蓄降雨和调节径流的作用。5常绿阔叶林木荷群落内6个常见树种叶片的δ13Cl值的范围在-28.45‰—-32.49‰之间,水分利用效率在3.5～4.7 mmolCO2·mol-1,6个树种水分利用效率的顺序为细叶青冈>木荷>苦槠>栲树>石栎>米槠。不同演替序列优势树种水分利用效率随演替进展表现出明显的协同变化规律,石栎的水分利用效率呈降低趋势,而栲树和木荷呈升高趋势。但是在后期演替阶段,木荷水分利用效率呈减少趋势,栲树一直在增加,优势种水分利用效率随演替进展的变化验证了天童植被演替序列的合理性。水分利用效率与生境有关,在山脊特殊生境,云山青冈水分利用效率最高,栲树和木荷较低,在灌丛生境,石栎水分利用效率最高,在水分条件较好的常绿阔叶林生境,栲树和木荷的水分利用效率较高。6栲树冠层沿8m高度梯度自上而下叶片δ13C范围在-27.57‰到-31.96‰之间,自上而下逐渐降低,存在Martinelli“冠层贫化效应”,下降值为-3.1‰,与Martinelli其提出的温带和热带冠层冠层叶片δ13C下降值-3.6‰非常吻合,为“冠层贫化效应”假说在我国东部亚热带常绿阔叶林区也成立提供了实验依据。栲树冠层WUE的均值范围在3.29到5.25mmolCO2 mol-1之间,水分利用效率WUE表现为冠层顶部>中部>底部的规律,在时间尺度上,5月份冠层上部的WUE最高,为5.25 mmolCO2 mol-1。在冠层梯度上,净光合速率Pn和Nmass均存在显著差异(p<0.01)。冠顶净光合速率显著高于冠下,从1月到7月Pn逐月上升,在7月份冠顶达到最高值15.4μmolCO2m-2s-1,9月份以后,Pn依次下降。Nmass也表现出与Pn相同的变化趋势,1-7月份呈上升趋势,9月份之后显著下降,最大值2.8%也出现在7月份。11月份到次年1月份比较低。在冠层梯度上,δ13C、WUE, Pn和Nmass之间均存在正相关的关系。7基于sap flow与冠层叶片13C的甄别率值Δ13C,首先建立栲树群落每个冠层梯度水碳耦合模型：然后根据每个冠层梯度的叶面积指数建立冠层整体平均水碳耦合模型：利用Li-6400对冠顶、冠下4 m、冠下6m高度的叶片光合速率进行实测,对模型进行验证,结果表明实测值与预测比较接近,所建模型精度很高(R=0.90,F=46.84,P<0.0001),具有可靠性。把冠层叶片δ13C值、树干液流值以及叶面积指数代入建立的模型,获取得了栲树冠层连续的瞬时平均净光合速率数据。以2010年8月份为例,上午8点之前,处于很低的水平,接近于0,上午8：00之后开始迅速上升,10：00达到最大值,之后开始下降,下午18：00以后,又恢复到0值附近。气温和光合有效辐射与冠层净光合速率也极为相关,可以用对数曲线表示。空气水汽压亏缺与冠层净光合速率呈正线性正相关。当冠层蒸腾量小于200 g m-2s-1时,冠层光合速率随蒸腾速率的增加而增加,当冠层蒸腾量大于200 g m-2s-1时,冠层光合速率随蒸腾速率的增加而减小。8近60年,天童地区月平均气温、降雨量和月参考蒸散量(ET0)在7、8月份明显增加,年平均气温、降雨量和ET0增加趋势十分显著(P<0.001)；天童地区常绿阔叶林56年NPP的平均值为12.196t·hm-2·a-1,近60年升高趋势极为显著(P<0.0001)；未来温度升高2℃,降水量增加20%的情景下,该地区常绿阔叶林的NPP将升高15.9%。未来温度升高2℃,降水量减少20%的情景下,NPP将降低4.9%。未来温度升高2℃,降水量不变的情景下,NPP将增加5.5%；年降雨量、ET0年均值和年平均气温是影响NPP变化的主要因子。更多还原

【Abstract】 The vegetation-atmosphere interface is the exchange space of water and CO2. Water and CO2 are the main components of water and carbon fluxes of the terrestrial ecosystem, and are controlled by canopy stoma. Therefore, canopy stoma is the connected point of water and carbon of the territal ecosystem. Canopy stoma is sensitive to environmental factors, and the ecological process that canopy controlled and adjusted the water and carbon fluxes. How to model the fluxes of water and carbon of the canopy is a scientific issues that many scientists focused on.This study was conducted in the evergreen broad-leaved forest in Tiantong National Forest Park, and measured sap flow, meteorological and hydrological factors, leaf carbon isotope of canopy, and water use effiency, based on coupling of sap flow and leaf carbon isotope, the coupling model of water and carbon model is created, and the process of water and carbon coupled is clarified.1 Permanent plot study was carried out from the meteorological data from June 2009 to august 2010 in Forest Ecosystem Observation and Research station in Tiantong. Total rainfall outside the forest was 2316 mm, and the throughfall, stemflow, and canopy interception accounted for 81.7%,2.3% and 16.0% of the total rainfall respectively. The through fall and stem flow had significant linear relationships with rainfall (P<0.01). The canopy interception rate showed significantly negative correlation with the rainfall, rainfall duration, rainfall intensity, and relative humidity during rainfall (P<0.01), but positive correlation with wind velocity (P<0.01).2 Saturated hydraulic conductivity (Ks) increased significantly in the 0-60 cm layers with the vegetation succession (p<0.001). The average Ks in the 60 cm soil profile significantly increased from the bare land, Lithocarpus glaba+Laroptahon chenese shrub, Pinus massonian forest, Schiima superba+Pinus massoniana forest, Schima superba forest to Castanopsis fargesii forest (df=5,F=10.69, p=0.002). In the shrub stage, the average Ks had made significant difference to bare land (p<0.05), in the Schima superba forest, the average Ks had been increased significantly(p<0.05), in the climax stage, the average Ks was 3.28 mm min-1 and reached maximum value. Soil bulk density, non-capillary porosity, and silt content were the key factors that affected Ks. Soil organic matter (SOM) was also increased with vegetation succession and positively correlated to Ks significantly (p<0.01). Castanopsis fargesii forest was able to resist the storm intensity of 10 years recurrence. Schima superba forest was able to resist the storm intensity of 1 year recurrence. However, overland runoff occurred easily in the early successional stages, such as, in the bare land, Lithocarpus glaba+Laroptahon chenese shrub, Pinus massonian forest.3 In the Castanopsis fargesii community, the values of transpiration varied clearly from 5.07 (g m-2 s-1) to 84.28 (g m-2s-1), Maximum value was 18 times greater than minimum value, which indicated that trees with different diameters varied obviously in water using straggles, contribution, functions in the same community. Trees with larger diameter had higher value of transpiration because of their larger sapwood area. Furthermore, Tall trees occupied superior spaces and obtained more resources than any other tree species. These conditions ensured tall trees had greater sap flow. Although the value of transpiration of Catanopsts fargesii was greater than that of Schima superba attributed to larger diameter and sapwood area of Catanopsts fargesii, the sap low velocity of Schima superba was higher than Catanopsts fargesii because the stoma size of Schima superba was bigger than Catanopsts fargesii. Sap flow of Catanopsts fargesii and Schima superba varied widely associated with weather conditions. In the sun day, sap flow regularly changed with the solar radiation, in the cloudy day, sap flow fluctuated with solar radiation. However, in moderate rain, sap flow decreased significantly, and in the storm weather condition, such as October 1,2009, the value of sap flow declined to 0-0.5 g m-2 s-1, a lowest value in the same month. Annual change of sap flow and transpiration of Catanopsts fargesii and Schima superba was consistent with seasonal change. In winter from December to February, sap flow and transpiration was at a low lever, then became increasing in March, till to July and August, sap flow and transpiration reached maximum value. After September, sap flow and transpiration began decreasing. Photosynthetic active radiation (PAR) and vapor deficient (D) driving force of canopy transpiration.4 The values of evapotranspiration were closed estimated by the method of water balance and Penman-Metainth Equation in Catanopsts fargesii community. During the study period from June, 2009 to August,2009, evapotranspiration, soil water content change, and run off accounted for 72.1%,20.2%, and 6.7% of total rainfall. Canopy transpiration accounted for 81.4% of evapotranspiration, which indicated that transpiration was the main component of evaportranspiration. The maximum value of Catanopsts fargesii canopy was 7.2 mm d-1 in August, and minimum value was 0.52 mm d-1 in February. Photosynthetic active radiation (PAR) and vapor deficient (D) driving force of canopy transpiration. The results of this study suggested that the climax forest, Catanopsts fargesii community had good function of intercepting rainfall and reforming runoff.5δ13C1, of six tree species varied from-28.45‰to-32.49‰, and water use effecint (WUE) varied from 3.5-4.7 mmolCO2·mol-1 in the Schima superba community. The WUE order of six tree species was Cyclobalanopsis myrsinae> Schima superba> Castanopsis sclerophylla> Catanopsts fargesii> Lithocarpus glaba> Castanopsis carlesii. The WUE of the dominant tree species collaboratly changed with the sequence of the forest succession. WUE of Lithocarpus glaba decreased, Catanopsts fargesii and Schima superba increased as the succession process. However,, WUE of Schima superba began to decreasing, and WUE of Catanopsts fargesii was still increased in the late ssuccessional stage. These results were so interesting that verified the reasonableness of the forest succession series in Tiantong National Park. WUE was correlated to habitation. On the ridge, WUE of Cyclobalanopsis sessilifolia was greatest, and lower values of Catanopsts fargesii and Schima superba increased as the succession process. However, In the shrub stage, where forest was serious disturbed, Lithocarpus glaba had higher WUE value, lower value of Catanopsts fargesii and Schima superba. However, in the sites of evergreen broad-leaved forest, where soil water conditions were better, WUE values of Catanopsts fargesii and Schima superba were greater than Lithocarpus glaba.6 The mean value ofδ13C under the gradients of 8 m canopy was from-27.57‰to-31.96‰, and showed Martinelli "canopy isotope depleted effect". The decreased value was-3.1‰, and this value was closed to-3.6% in the canopy of tropical rain forest and boreal forest. We tested this hypothesis in the subtropical evergreen broad-leaved forest in Eastern China. The mean of WUE along canopy was from 3.29 to 5.25 mmolCO2 mol-1. The order of WUE was upper canopy>middle canopy> low canopy. WUE along canopy temperately changed with the season change. The maximum value of WUE was 5.25 mmolCO2 mol-1, and appeared in May. Net photosynthetic rate (Pn) and Nmass varied significantly Along the gradient of canopy (p<0.01). Pn of the upper canopy was higher than lower canopy. Pn increased from January to July, and obtained maximum value (15.4μmolCO2 m-2 s-1) in July. After September, Pn began decreasing. Nmass showed same trend as Pn, and maximum value (2.8%) also appeared in July. From December to Januray, Nmass was lower than any othe month.δ13C, WUE, and Pn were positive correlated to Nmass along the gradient of canopy.7 Based on sap flow and△13C, The first step, The model of water coupled carbon was constructed in each canopy gradient of Catanopsts fargesii community: then, according to LAI of each canopy Catanopsts fargesii communityIn order to test accuracy of model, we used Li-6400 and measured the Pn in the upper canopy,4 m,6m layers along the gradients of canopy, and calculated Pn of canopy by big leaf model. The predicted data fitted the measured data very well, which indicated the model had good performance (F=46.89, P<0.0001).We inputted the data ofδ13C, sap flow density and LAI in August,2010 into the model, and obtained the data of Pn. The diurnal change of Pn accosiated with the solar radiation, before 8:00 AM, the value of Pn is very low, and closed to 0. After 8:00 AM, Pn increased quickly, and achieved maximum value at 10:00 AM. After this time, Pn began decreasing, after 18:00 PM, Pn declined to 0 levels. Air temperature (T) was linearly correlated to Pn, PAR, and D fitted Pn significantly as logarithmic curve. Moreover, canopy transpiration (Tr) was also correlated to Pn significantly. When Tr< 200 g m-2s-1, Pn increased with Tr increasing, when Tr> 200g m-2s-1, Pn declined with Tr increasing.8 Based on the daily meteorological data from 1954 to 2009 in Tiantong region, net primary productivity (NPP)model of Zhou Guangsheng was used to study effect of climate change on NPP of evergreen broad-leaved forest. The result showed that, (1) Monthly average values of air temperature, precipitation, and reference evaportranspiration (ET0) clearly increased in July and August, and the annual trends of average air temperature, precipitation, and ET0 increased significantly in Tiantong region in recent 60 years (P＜0.001). (2) Annual average NPP of 56 years was 12.196 t·hm-2·a-1, and increased significantly in recent 60 years (P<0.0001). (3) In the future, if air temperature increases 2℃and precipitation increases 20%, NPP will increase 15.9% in this region, if air temperature increases 2℃and rainfall decreases 20%, NPP will decrease 4.9%, if air temperature increases 2℃and rainfall is not changed, NPP will increase 5.5%. (4) Annual average precipitation, ET0 and air temperature were the main meteorological factors that affected NPP in this region.更多还原