【作者】 陈德祥；

【导师】 肖文发；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2010， 博士

【摘要】 本研究利用尖峰岭国家野外观测站现有通量观测塔,将涡度协方差技术、CO2/H2O浓度廓线测定技术、林内小气候梯度观测技术与地表植被动态监测相结合,并配以土壤呼吸长期观测、主要代表种生理生态特性测定等相关辅助观测,基于多年长期的连续观测,综合研究尖峰岭热带山地雨林碳交换动态特征和影响因素,结果表明：1、尖峰岭热带山地雨林26年来,气温呈上升趋势。年平均最高、年最低气温变化趋势存在不对称性,即年最低气温明显上升,而年平均最高气温上升不明显,说明尖峰岭山地雨林气候变暖趋势主要是年最低气温显著升高造成的。林冠各层气温日变化呈倒U字形变化趋势；年降水量和蒸发量变化不明显,降水量相对较为丰富,但存在明显的旱、雨季区分,年降水量与年蒸发量的比值约为2.0；尖峰岭热带山地雨林盛行风方向为正南方向,林内风速时空变异较大,林内风速与高度呈正相关,森林下层基本处于静风状态(尤其是夜间),导致湍流交换较弱：总辐射、净辐射和光合有效辐射日变化都呈现早晚低,中午高的倒U字形变化规律。辐射的空间分布差异明显,冠层上部存在直射辐射,辐射强度大,而在下层环境中基本都是散射辐射,其值较低。热带山地雨林中光的这种垂直模式导致个体形成了相应的适应对策,可以充分保证生态系统各层次的高效光合碳同化,达到系统对光资源的合理和充分利用。2、基于1983年开始近25年固定样地清查数据计算的中国海南岛尖峰岭热带山地雨林的生物量结果表明：雨林生物量随林木径级的增加而增大,DBH>10 cm的个体占生物量总和的90%以上,尤其是数量不到1%的大径级个体(DBH≥45 cm),其生物量所占比例更是高达32%,充分反映了在热带森林中大径级个体对生物量和碳密度的贡献占据绝对的主导作用。生物量密度在397.05±57.92和502.35±96.32 Mg·ha-1范围间变动,平均为453.13±80.06 Mg·ha-1；林木碳密度在201.43±29.38和254.85±48.86 Mg C·ha-1范围间变动,平均为230.84±40.61 Mg C·ha-1。基于样地调查估算的山地雨林地上部分碳汇大小P9201样地平均为2.13±0.46 Mg C ha-1yr-1,P8302样地为0.49±0.17 Mg Cha-1yr-1.3、基于2006年到2009年近四年涡度协方差通量监测结果显示,尖峰岭热带山地雨林碳交换昼夜节奏明显,日碳交换通量变异较大,在-9.20～5.20g C m-2 day-1范围间变动(在涡度协方差技术中,通常用负值代表碳吸收,正值代表碳释放),碳交换通量季节及年间变异较大,雨季碳交换能力明显强于旱季；以涡度协方差测定的碳交换通量和CO2/H20廓线估测的林内C02存储通量估算的2006-2009年尖峰岭热带山地雨林生态系统净碳交换(NEE)分别为-1.89±0.43、-2.96±0.40、-2.42±0.42、-2.15±0.41 Mg C·ha-1·yr-1,平均为-2.36±0.42 Mg C·ha-1·yr-1,表明尖峰岭热带山地雨林为净的碳汇；总生态系统生产力(gross ecosystem productivity,GEP,由涡度协方差计算的日-·NEE和估算的生态系统呼吸Re之和计算得出)分别为19.19±2.23、19.19±2.46、21.38±2.27、19.04±2.23 MgC·ha-1·yr-1,平均为19.70±2.30 Mg C·ha-1·yr-1。4、涡度协方差方法和固定样地的资源清查方法作为研究森林碳源汇大小的两种主要方法,各有其优缺点。本论文涡度协方差测定结果显示,尖峰岭热带山地雨林多年平均碳汇大小与通量塔紧邻的样地调查估算的碳汇大小其值非常接近。这个结果说明,涡度协方差技术可以很好的用于评估尖峰岭热带山地雨林的碳汇大小,而且可以与固定样地的清查取得很好的比对结果,可以基于与生物量清查的对比研究来修正通量估计偏差。涡度协方差法可以很好的用来研究生态系统过程的机理和机制问题,又可以用来量化生态系统的CO2交换速率对环境因子变化的响应,同时还可以用来评价经营和干扰问题对生态系统的影响。样地清查又可以提供给我们生态系统碳交换的空间分布格局和动态的细致信息。因此,在尖峰岭地区,甚至是海南岛地区同时开展这两种方法的应用、比较研究将具有非常好的前景和产出。总之,在本论文涡度协方差技术的应用研究中估算的多年平均碳汇大小(2.36±0.42Mg C·ha-1·yr-1)与样地调查法估算的碳汇大小(2.13±0.46 Mg C ha-1yr-1)其值相近,为当前以涡度协方差技术和样地清查技术估算森林碳源汇大小的比较研究中提供了一个较好的研究案例；本论文研究表明,不管是涡度协方差监测还是样地资源清查,结果都显示尖峰岭未受扰动的热带山地雨林为净的碳汇,说明热带森林仍然存在巨大的碳汇潜力；同时,本论文研究表明,尖峰岭热带山地雨林碳交换与降雨(尤其是暴雨降雨次数)和干旱状况呈明显的二次曲线变化趋势,降雨和干旱月份次数是尖峰岭热带山地雨林碳交换能力的两个关键影响因子,但碳交换能力同时受台风等极端干扰事件的影响。更多还原

【Abstract】 Tropical montane rain forest at Jianfengling is one of the most typical rain forests in China. We used two independent approaches, biometry and micrometeorology, as well as CO2/H2O profile to determine the net ecosystem exchage (NEE) and to explore the environmental controls of tropical montane rain forest at Jianfengling, Hainan Island. The results show as follows:1. Annual mean air temperature has been rising in recent 26 years, and annual mean minimum temperature had a significant increase but mean maximum temperature increased slightly. Diurnal courses of air temperature showed upside down U shape, and the minimum value occurred in 6:00-8:00, the maximum value appeared near 14:00. The precipitation at Jianfengling is rich, but varied distinctly from dry season to wet season. The prevailed wind came from southern, and the wind speed profile displayed a highly spatial-temporal variability and which had a positive relationship with height below canopy. Diurnal courses of solar radiation, net radiation and photosynthetic active radiation were the same as air temperature, and the daily peak appeared at 12:00, while at night the solar radiation and PAR were near zero. Annual changes showed single-peak trend, monthly peak appeared in April, and monthly valley value was in February.2. Biometric inventories of 25 years from 1983 indicated that the forest was either a source or a modest sink of carbon. The biomass density varied between 397.05±57.92 and 502.35±96.32 Mg·ha-1, and averaged 453.13±80.06 Mg·ha-1; while carbon density varied between 201.43±29.38 and 254.85±48.86 Mg C·ha-1, and averaged 230.84±40.61 Mg C·ha-1. The biomass of trees with dbh> 10 cm comprised 96% of the total above-ground biomass (AGB) for all trees with dbh> 1.0 cm; and the biomass of trees with dbh> 45 cm contributed 32% of the total AGB, although the number of stems accounted for just 1% of the total stems. The carbon source or sink based on ground measurements indicated that plot P9201 was a net sink at a rate of 2.13±0.46 Mg C ha-1yr-1, while the plot P8302 with a rate of 0.49±0.17 Mg C ha-1yr-1.3. Based on four years of eddy covariance data for CO2 fluxes in tropical montane rain forest we found that the net ecosystem exchange of carbon dioxide (NEE) varied between-1.89 and-2.96 Mg C-ha-1·yr-1(a positive flux indicates carbon loss by the forest, a negative flux indicates carbon gain) from the year of 2006 to 2009, and averaged-2.36±0.42 Mg C-ha-1·yr-1, which showed a moderate sink of this forest. The diurnal pattern of flux showed a significant transition from daytime to nighttime, this similar trend is also found in the course of interannual and seasonal (wet and dry season) variability of flux. The forest was found productive with the gross ecosystem production (GEP) of 19.19±2.23、19.19±2.46、21.38±2.27、19.04±2.23 Mg C·ha-1·yr-1 from 2006 to 2009 respectively, and averaged GEP is 19.70±2.30 MgC·ha-1·yr-1.4. Inventory-based method has been used as major traditional means of addressing net ecosystem carbon exchange of an ecosystem over:multiple years. In recent years the eddy covariance technique has emerged as an alternative way to assess ecosystem carbon exchange. Although these two methods have its merits and limitations, the results in this study produced from eddy covariance technique did well match the estimates of net ecosystem productivity produced with the ground-based inventory. The study showed that we can remedy bias errors of eddy covariance by conducting comparative studies with biomass inventories to constrain flux estimates. The eddy covariance method is particularly adept as studying ecosystem physiology. Specifically, it can be used to quantify how CO2 exchange rates of whole ecosystems respond to environmental perturbations, and when paired systems are applied the method can be used to assess management questions such as the effects of disturbance and plant functional type. Inventory studies of biomass change produce estimates of annual net primary productivity in a variety of temporal and spatial scales. So, by conducting comparative studies in future research at Jianfengling tropical montane rainforest will have a good prospect and production. Overall, the maintance of flux tower and post-field data processing (including quanlity analysis, quanlity control, and data gap filling) are the key steps on deciding whether the technique of eddy covariance can evaluate accurately carbon exchange of ecosystems or not. But, our results estimated from four years of eddy covariance showed that a significant accumulation of carbon (2.36±0.42 Mg C·ha-1·yr-1) at Jianfengling tropical montane rain forest was found, this estimate was independently confirmed through biometric methods which also showed the forest to be gaining carbon at a rate of 2.13±0.46 Mg C ha-1yr-1.Our study provide a good case study in the situation that the results produced from eddy covariance technique did not well match the estimates of net ecosystem productivity produced with the ground-based inventory. Undisturbed tropical rain forests have been historically presumed to contribute little to changes in atmospheric carbon dioxide. But our results indicted that this forest was a carbon sink based on the eddy covariance technique and the ground-based inventory. These results indicated that undisturbed tropical rain forests still have the potential to accumulate carbon from atmosphere. Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months. Precipitation and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest. Besides that, we also found a strong relationship between disturbance (such as typhoon) and the dynamics of carbon exchange.更多还原