Data from: Rapid increases in forest understory diversity and productivity following a mountain pine beetle (Dendroctonus ponderosae) outbreak in pine forests

The current unprecedented outbreak of mountain pine beetle (Dendroctonus ponderosae) in lodgepole pine (Pinus contorta) forests of western Canada has resulted in a landscape consisting of a mosaic of forest stands at different stages of mortality. Within forest stands, understory communities are the reservoir of the majority of plant species diversity and influence the composition of future forests in response to disturbance. Although changes to stand composition following beetle outbreaks are well documented, information on immediate responses of forest understory plant communities is limited. The objective of this study was to examine the effects of D. ponderosae-induced tree mortality on initial changes in diversity and productivity of understory plant communities. We established a total of 110 1-m2 plots across eleven mature lodgepole pine forests to measure changes in understory diversity and productivity as a function of tree mortality and below ground resource availability across multiple years. Overall, understory community diversity and productivity increased across the gradient of increased tree mortality. Richness of herbaceous perennials increased with tree mortality as well as soil moisture and nutrient levels. In contrast, the diversity of woody perennials did not change across the gradient of tree mortality. Understory vegetation, namely herbaceous perennials, showed an immediate response to improved growing conditions caused by increases in tree mortality. How this increased pulse in understory richness and productivity affects future forest trajectories in a novel system is unknown.

当前加拿大西部扭叶松（Pinus contorta）林爆发了史无前例的山松甲虫（Dendroctonus ponderosae）灾害，使得林地景观呈现出不同死亡阶段林分镶嵌分布的格局。林分内部的林下植被群落是绝大多数植物物种多样性的储存库，且会响应干扰过程进而影响未来森林的群落组成。尽管学界已对甲虫灾害后林分组成的变化开展了较为充分的研究，但针对森林林下植物群落即时响应的相关资料仍十分有限。本研究旨在探究山松甲虫诱导的林木死亡对林下植物群落多样性与生产力初始变化的影响。我们于11片成熟扭叶松林中布设了总计110个1平方米的样地，以林木死亡率与地下资源可获得性为驱动因子，在多年尺度下测定林下植被多样性与生产力的动态变化。整体来看，随着林木死亡率梯度升高，林下群落的多样性与生产力均显著提升；草本多年生植物的物种丰富度随林木死亡率上升、土壤含水量与养分水平的改善而显著增加。与之相对，木本多年生植物的多样性并未随林木死亡率梯度出现明显变化。林下植被（尤以草本多年生植物为主）对林木死亡率升高所改善的生境条件表现出即时响应。目前尚不清楚这种林下植物丰富度与生产力的突增，将如何影响这一新型生态系统中的森林群落未来演替轨迹。