Data from: Ecosystem memory of wildfires affects resilience of boreal mixedwood biodiversity after retention harvest

The extent to which past states influence present and future ecosystem characteristics (ecosystem memory (EM)) is challenging to assess because signals of past ecological conditions fade with time. Using data about seven different taxa, we show that ecological gradients initiated by wildfires up to three centuries earlier affect biotic recovery after variable retention harvest in the boreal mixedwood forest. First, we show that fire history over the last 300 years is reflected in pre-harvest species-specific stand basal area (BA), with longer times since high severity fire associated with proportionally higher BA of shade-tolerant softwood species than shade-intolerant hardwoods. Second, using patterns in the BA of pre-harvest tree species we link fire history to species composition of pre-harvest assemblages of bryophytes, herbs, shrubs, regenerated trees, songbirds, spiders and carabid beetles. Finally, we use variance partitioning to compare the importance of species-specific pre- versus post-harvest BA for explaining the structure of these seven biotic assemblages two, five and ten years after harvest. We detected persistent significant effects of pre-harvest BA in all post-harvest biotic assemblages up to ten years after harvest. Pre-harvest BA was more strongly associated with early post-harvest understory plant and carabid beetle assemblages than was post-harvest BA, but the opposite was true for spiders, songbirds and regenerated trees. EM effects were detected two, five and ten years after harvest but temporal patterns varied according to taxa. Thus, EM of fire history can persist at least ten years after variable retention harvest and such effects appear to be stronger for understory plants than for animals. We conclude that management of biological legacies to increase post-disturbance EM will increase overall resilience and sustainability of these mixedwood forests.

过往环境状态对当前及未来生态系统特征的影响程度，即生态系统记忆（Ecosystem Memory, EM），因其过往生态条件的信号会随时间衰减而难以评估。本研究依托涵盖7个不同生物类群的数据集，证实了距今至多三个世纪的野火引发的生态梯度，仍会影响北方混交林在可变保留采伐后的生物恢复过程。首先，我们发现过去300年的火灾历史可通过采伐前物种特异性林分断面积（stand basal area, BA）体现：距离高强度野火发生的时长越长，耐阴针叶树种的断面积占比相较于不耐阴阔叶树种越高。其次，我们利用采伐前树木物种的断面积特征，将火灾历史与苔藓植物、草本植物、灌木、更新林木、鸣禽、蜘蛛及步甲科甲虫这7类采伐前生物群落的物种组成建立关联。最后，通过方差分解法，我们比较了采伐前与采伐后物种特异性断面积，在解释采伐后2年、5年及10年这7类生物群落结构时的重要性差异。研究结果显示，在采伐后至多10年的所有生物群落中，均检测到采伐前断面积存在持续的显著影响。相较于采伐后断面积，采伐前断面积与采伐后早期林下植物及步甲科甲虫群落的关联更强；但对于蜘蛛、鸣禽与更新林木而言，情况则相反。我们在采伐后2年、5年及10年均检测到EM效应，但其时间模式因类群而异。综上，火灾历史形成的生态系统记忆可在可变保留采伐后至少持续10年，且该效应对林下植物的影响要强于动物。我们据此得出结论：通过调控生物遗留物以增强扰动后的生态系统记忆，可提升此类北方混交林的整体恢复力与可持续性。