Data from: Boosts in leaf-level photosynthetic capacity aid Pinus ponderosa recovery from wildfire

Forests mitigate climate change by sequestering massive amounts of carbon, but recent increases in wildfire activity are threatening carbon storage. Currently, our understanding of wildfire impacts on forest resilience and the mechanisms controlling post-fire recovery remains unresolved due to a lack of empirical data on mature trees in natural settings. Here, we quantify the physiological mechanisms controlling carbon uptake immediately following wildfire in mature individuals of ponderosa pine (Pinus ponderosa), a wide-spread and canopy-dominant tree species in fire-prone forests. While photosynthetic capacity was lower in burned than unburned trees due to an overall depletion of resources, we show that within the burned trees, photosynthetic capacity increases with the severity of damage. Our data reveal that boosts in the efficiency of carbon uptake at the leaf-level may compensate for whole-tree damage, including the loss of leaf area and roots. We further show that heightened photosynthetic capacity in remaining needles on burned trees may be linked with reduced water stress and leaf nitrogen content, providing pivotal information about post-fire physiological processes. Our results have implications for Earth system modeling efforts because measurements of species-level physiological parameters are used in models to predict ecosystem and landscape-level carbon trajectories. Finally, current land management practices do not account for physiological resilience and recovery of severely burned trees. Our results suggest premature harvest may remove individuals that may otherwise survive, irrevocably altering forest carbon balance.

森林通过固存巨量碳来减缓气候变化，但近期野火活动的加剧正威胁着森林碳储量。目前，由于自然生境下成熟林木的实证数据匮乏，我们对于野火对森林韧性的影响，以及调控火后恢复的相关机制仍缺乏明确认知。本研究以火灾频发森林中分布广泛且为冠层优势种的黄松（Pinus ponderosa）为研究对象，量化了其成熟个体在野火发生后即刻调控碳吸收的生理机制。尽管受整体资源耗竭的影响，过火林木的光合能力低于未过火林木，但我们的研究发现，在过火林木群体内，光合能力随受损程度的加重而提升。研究数据显示，叶片水平碳吸收效率的提升，或可弥补整株林木遭受的损伤，包括叶面积与根系的丧失。我们还进一步证实，过火林木剩余针叶的光合能力提升，可能与水分胁迫缓解及叶片氮含量变化相关，这为火后生理过程提供了关键认知。本研究结果对地球系统建模工作具有重要参考意义，因为模型中常利用物种水平的生理参数来预测生态系统与景观尺度的碳动态轨迹。此外，当前的土地管理实践并未考虑严重过火林木的生理韧性与恢复能力，我们的研究结果表明，提前采伐可能会移除本可存活的林木个体，进而不可逆转地改变森林碳平衡。