Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, USA.
PLoS One. 2013;8(1):e54045. doi: 10.1371/journal.pone.0054045. Epub 2013 Jan 15.
Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC) and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric). This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE) show that the mesic site was a net carbon sink (NEE = -2.48 tonnes C ha(-1)), while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha(-1), respectively), but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha(-1) at the mesic, intermediate and xeric sites, respectively). Nonetheless, rates of NEE returned to pre-fire levels 1-2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30-60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months), drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems.
火调节着稀树草原生态系统的结构和功能，但我们缺乏对循环火如何影响稀树草原碳动态的理解。此外，预测的气候变化如何影响这些生态系统中火与碳循环之间的相互作用在很大程度上仍是未知的。本研究利用预设火、涡度相关（EC）和统计技术的新颖组合，研究了在土壤水分可利用性梯度（湿润、中等和干旱）上频繁燃烧的长叶松稀树草原中的碳动态。这种研究方法使我们能够沿着长叶松的生态幅度研究碳交换与循环火之间的复杂相互作用。经过三年的 EC 净生态系统交换（NEE）测量表明，湿润地点是净碳汇（NEE = -2.48 吨 C ha（-1）），而中等和干旱地点是净碳源（NEE = 1.57 和 1.46 吨 C ha（-1），分别），但考虑到因燃料消耗而导致的碳损失时，所有三个地点都是碳源（湿润、中等和干旱地点的碳损失分别为 10.78、7.95 和 9.69 吨 C ha（-1））。尽管如此，火灾后 NEE 仍在 1-2 个月内恢复到火灾前的水平。预设火消耗叶面积与火灾后 NEE 的减少有关，系统在火灾后 30-60 天内迅速恢复其碳吸收能力。虽然火灾造成的损失会影响短期（即时到几个月）的碳平衡，但研究的最后两年的干旱条件是影响多年至多年时间尺度上净碳损失的更重要因素。然而，在更大的环境变异性和更多的火灾循环上进行更长期的观测，将有助于更准确地检查火与气候之间的相互作用，并对这些系统中的碳动态做出未来预测。
