Data from: Post-fire changes in forest carbon storage over a 300-year chronosequence of Pinus contorta-dominated forests

A warming climate may increase the frequency and severity of stand-replacing wildfires, reducing carbon (C) storage in forest ecosystems. Understanding the variability of post-fire C cycling on heterogeneous landscapes is critical for predicting changes in C storage with more frequent disturbance. We measured C pools and fluxes for 77 lodgepole pine (Pinus contorta Dougl. ex Loud var. latifolia Engelm.) stands in and around Yellowstone National Park (YNP) along a 300-year chronosequence to examine how quickly forest C pools recover after a stand-replacing fire, their variability through time across a complex landscape, and the role of stand structure in this variability. Carbon accumulation after fire was rapid relative to the historical mean fire interval of 150-300 years, recovering nearly 80% of pre-fire C in 50 years and 90% within 100 years. Net ecosystem carbon balance (NECB) declined monotonically from 160 g C m-2 yr-1 at age 12 to 5 g C m 2 yr-1 at age 250, but was never negative after disturbance. Decomposition and accumulation of dead wood contributed little to NECB relative to live biomass in this system. Aboveground net primary productivity was correlated with leaf area for all stands, and the decline in aboveground net primary productivity with forest age was related to a decline in both leaf area and growth efficiency. Forest structure was an important driver of ecosystem C, with ecosystem C, live biomass C, and organic soil C varying with basal area or tree density in addition to forest age. Rather than identifying a single chronosequence, we found high variability in many components of ecosystem C stocks through time; a > 50% random subsample of the sampled stands was necessary to reliably estimate the non-linear equation coefficients for ecosystem C. At the spatial scale of YNP, this variability suggests that landscape C develops via many pathways over decades and centuries, with prior stand structure, regeneration, and within-stand disturbance all important. With fire rotation projected to be < 30 years by mid century in response to a changing climate, forests in YNP will store substantially less C (at least 4.8 kg C/m2 or 30% less).

气候变暖可能会提升林分毁灭型野火（stand-replacing wildfire）的发生频率与强度，进而降低森林生态系统的碳（C）储量。明晰异质景观（heterogeneous landscapes）下火烧后碳循环的变异特征，对于预测干扰频次增加背景下的碳储量变化至关重要。
本研究沿300年时间序列样带（chronosequence），对黄石国家公园（Yellowstone National Park, YNP）及其周边的77块黑松（Pinus contorta Dougl. ex Loud var. latifolia Engelm.）林分开展碳库与碳通量（C pools and fluxes）测定，旨在探究林分毁灭型野火后森林碳库的恢复速率、复杂景观下碳库随时间的变异特征，以及林分结构在该变异中的作用。
相较于150~300年的历史平均火灾间隔期，火烧后碳积累速率较快：林分在50年内即可恢复至火烧前碳储量的近80%，100年内恢复至90%。
生态系统碳平衡（Net ecosystem carbon balance, NECB）从林龄12年时的160克碳每平方米每年单调递减至林龄250年时的5克碳每平方米每年，但在干扰后始终未出现负值。相较于该系统中的活生物量，枯木的分解与积累对生态系统碳平衡的贡献极小。
所有林分的地上净初级生产力（Aboveground net primary productivity）均与叶面积呈显著相关；地上净初级生产力随林龄增长的下降趋势，同时与叶面积和生长效率的降低有关。林分结构是驱动生态系统碳动态的重要因素：除林龄外，生态系统碳储量、活生物量碳与有机土壤碳均随胸高断面积（basal area）或树木密度发生变化。
本研究并未得到单一的时间序列样带，反而发现生态系统碳库的诸多组分随时间呈现高度变异；若要可靠估算生态系统碳的非线性方程系数，需抽取超过50%的采样林分作为随机子样本。
在黄石国家公园的空间尺度下，这种变异表明景观碳储量的积累会在数十年至数百年间通过多种路径实现，此前的林分结构、更新过程与林分内干扰均发挥着重要作用。
若气候变化导致本世纪中叶的火灾轮伐期（fire rotation）缩短至30年以下，黄石国家公园的森林碳储量将大幅降低（至少减少4.8千克碳每平方米，即降幅达30%）。