Smithsonian Environmental Research Center, Edgewater, MD 21307-0028, USA.
Proc Natl Acad Sci U S A. 2010 Feb 23;107(8):3611-5. doi: 10.1073/pnas.0912376107. Epub 2010 Feb 3.
Forests and their soils contain the majority of the earth's terrestrial carbon stocks. Changes in patterns of tree growth can have a huge impact on atmospheric cycles, biogeochemical cycles, climate change, and biodiversity. Recent studies have shown increases in biomass across many forest types. This increase has been attributed to climate change. However, without knowing the disturbance history of a forest, growth could also be caused by normal recovery from unknown disturbances. Using a unique dataset of tree biomass collected over the past 22 years from 55 temperate forest plots with known land-use histories and stand ages ranging from 5 to 250 years, we found that recent biomass accumulation greatly exceeded the expected growth caused by natural recovery. We have also collected over 100 years of local weather measurements and 17 years of on-site atmospheric CO(2) measurements that show consistent increases in line with globally observed climate-change patterns. Combined, these observations show that changes in temperature and CO(2) that have been observed worldwide can fundamentally alter the rate of critical natural processes, which is predicted by biogeochemical models. Identifying this rate change is important to research on the current state of carbon stocks and the fluxes that influence how carbon moves between storage and the atmosphere. These results signal a pressing need to better understand the changes in growth rates in forest systems, which influence current and future states of the atmosphere and biosphere.
森林及其土壤包含了地球上大部分的陆地碳储量。树木生长模式的变化会对大气循环、生物地球化学循环、气候变化和生物多样性产生巨大影响。最近的研究表明，许多森林类型的生物量都在增加。这种增加归因于气候变化。然而，如果不知道森林的干扰历史，生长也可能是由于未知干扰的正常恢复造成的。利用过去 22 年来从 55 个具有已知土地利用历史和 5 至 250 年树龄的温带森林样地收集的独特树木生物量数据集，我们发现最近的生物量积累大大超过了自然恢复引起的预期增长。我们还收集了超过 100 年的当地气象测量数据和 17 年的现场大气 CO2 测量数据，这些数据显示与全球观测到的气候变化模式一致的持续增加。这些观察结果表明，全球范围内观察到的温度和 CO2 的变化可以从根本上改变关键自然过程的速度，这是生物地球化学模型所预测的。确定这种速率变化对于研究当前的碳储量以及影响碳在储存和大气之间移动的通量非常重要。这些结果表明，迫切需要更好地了解森林系统中生长速率的变化，这会影响当前和未来的大气和生物圈状态。
