Root carbon pools across a post-fire tree density gradient in far northeastern Siberia, 2015 - 2017

Fire severity is increasing in larch forests of the Siberian Arctic as climate warms, and initial fire impacts on tree demographic processes could be an especially important determinant of long-term forest structure and carbon (C) dynamics. We hypothesized that changes in post-fire larch recruitment impact C accumulation through tree density impacts on understory microclimate and permafrost thaw. We tested these hypotheses by quantifying C pools across a Cajander larch (Larix cajanderi Mayr.) tree density gradient within a fire perimeter near Cherskiy, Russia that burned in 1940. Across the density gradient, from 2010 - 2017 we inventoried larch trees and harvested ground-layer vegetation to estimate above ground contribution to C pools. We also quantified woody debris C pools and sampled below ground C pools (soil, fine roots, and coarse roots) in the organic + upper mineral soils. Our findings should highlight the potential for a climate-driven increase in fire severity to alter tree recruitment, successional dynamics, and C cycling in Siberian larch forests.

随着气候变暖，西伯利亚北极地区的落叶松林火灾烈度持续升高，而火灾初期对树木种群动态过程的影响，或是决定长期森林结构与碳（C）循环动态的关键调控因素。本研究提出假说：火灾后落叶松种群更新的变化，可通过树木密度对林下微气候与永久冻土融化的调控作用，进而影响碳储量的累积过程。为验证上述假说，本研究以俄罗斯切尔克斯基（Cherskiy）附近1940年过火的火迹地内的卡扬德落叶松（Cajander larch, Larix cajanderi Mayr.）为研究对象，对其沿树木密度梯度分布的碳库展开量化分析。在该密度梯度范围内，研究团队于2010—2017年间完成了落叶松种群普查，并通过采集并收割地表层植被，估算地上生物量对碳库的贡献量。本研究同时量化了木质残体碳库，并在有机层与上层矿质土壤中采集了地下碳库样本，涵盖土壤、细根与粗根组分。本研究结果将揭示，气候驱动的火灾烈度升高，可能会改变西伯利亚落叶松林的树木种群更新、群落演替动态与碳循环过程。