Radiation-use efficiency of a forest exposed to elevated concentrations of atmospheric carbon dioxide
Radiation-use efficiency of a forest exposed to elevated concentrations of atmospheric carbon dioxide
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DOI：
10.1093/treephys/22.14.1003
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发表时间：
2002-10-01
期刊：
影响因子：
4
通讯作者：
Hamilton, JG
中科院分区：
文献类型：
--
作者：
DeLucia, EH;George, K;Hamilton, JG
我们比较了暴露于大气CO2浓度（[CO2]）的森林样地的辐射-生长利用效率（F），定义为每单位吸收的光合有效辐射的生物量积累速率，环境（类似于360穆尔升（-1））或升高（类似于560穆尔升（-1））大气CO2浓度（[CO2]）。火炬松（Pinus taeda L.）种植园，其中包含几个硬木树种在林下，熏蒸与自由空气CO2富集系统。生物量积累的优势火炬松的树木生长和站点特定的异速生长方程的每月测量计算。叶面积指数（L*）的估计，根据物种，通过三种方法：光学，异速生长和凋落物。基于树高和直径之间的关系，在第一个3年的曝光，我们得出结论，升高[CO2]并没有改变火炬松地上生物量分配的模式。有相当大的变化，L* 估计由不同的方法;总L* 是18-42%，较低的光学方法估计相比，从异速生长计算的估计，这种差异减少时，光学测量校正火炬松叶片的非随机分布。异速生长+凋落物的方法揭示了一个季节的最大总L* 为6.2-7.1，约1/3的总阔叶树叶。在本研究的前3年，[CO2]升高仅对L* 产生轻微影响。仅火炬松计算的平均F（SD），在环境和升高[CO2]地块中的树木分别为0.49 +/- 0.05和0.62 +/- 0.04 g MJ（-1）。增加27%的F，在响应CO2富集主要是由生物量增加的刺激，因为只有一个小的影响，升高[CO2] L* 在熏蒸的最初几年。大气中[CO2]的长期增加可以增加郁闭森林中的CO2，但这种增加的绝对幅度和持续时间仍然不确定。
We compared radiation-use efficiency of growth (F), defined as rate of biomass accumulation per unit of absorbed photosynthetically active radiation, of forest plots exposed to ambient (similar to360 mul l(-1)) or elevated (similar to560 mul l(-1)) atmospheric CO2 concentration ([CO2]). Large plots (30-m diameter) in a loblolly pine (Pinus taeda L.) plantation, which contained several hardwood species in the understory, were fumigated with a free-air CO2 enrichment system. Biomass accumulation of the dominant loblolly pines was calculated from monthly measurements of tree growth and site-specific allometric equations. Depending on the species, leaf area index (L*) was estimated by three methods: optical, allometric and litterfall. Based on the relationship between tree height and diameter during the first 3 years of exposure, we conclude that elevated [CO2] did not alter the pattern of aboveground biomass allocation in loblolly pine. There was considerable variation in L* estimates by the different methods; total L* was 18-42% lower when estimated by the optical method compared with estimates from allometric calculations, and this discrepancy was reduced when optical measurements were corrected for the non-random distribution of loblolly pine foliage. The allometric + litterfall approach revealed a seasonal maximum total L* of 6.2-7.1 with about 1/3 of the total from hardwood foliage. Elevated [CO2] had only a slight effect on L* in the first 3 years of this study. Mean F, ( SD), calculated for loblolly pine only, was 0.49 +/- 0.05 and 0.62 +/- 0.04 g MJ(-1) for trees in the ambient and elevated [CO2] plots, respectively. The 27% increase in F, in response to CO2 enrichment was caused primarily by the stimulation of biomass increment, as there was only a small effect of elevated [CO2] on L* during the initial years of fumigation. Long-terrn increases in atmospheric [CO2] can increase epsilon in closed-canopy forests but the absolute magnitude and duration of this increase remain uncertain.