Chandler Jennifer L
Department of Biology, West Virginia University, 53 Campus Drive, P.O. Box 6057, Morgantown, WV, 26506-6057, USA.
Department of Biology, Appalachian State University, 572 Rivers Street, Boone, NC, 28608, USA.
Oecologia. 2017 Mar;183(3):677-687. doi: 10.1007/s00442-017-3808-5. Epub 2017 Jan 19.
Understory light environments change rapidly following timber harvest, and while many understory species utilize and benefit from the additional light, this response is not ubiquitous in shade-obligate species. I examined the effects of patch cut timber harvest on the physiology and growth of an obligate forest understory species to determine if disturbances via timber harvest are physiological stressors or whether such disturbances provide physiological benefits and growth increases in understory species. Forest canopy structure, along with photosynthesis, respiration, water use efficiency, stomatal conductance, and growth rates of American ginseng were quantified one summer before and two summers after patch cut timber harvest. Survival following timber harvest was lower than that observed at undisturbed populations; however, growth of survivors increased post-harvesting, with growth increasing as a function of canopy openness. Light response curves as well as photosynthesis and respiration rates indicated that plants were not well acclimated to higher light levels in the growing season after timber harvest, but rather to two growing seasons after harvest. Relative growth rate formed a positive linear relationship with maximum photosynthesis following timber harvest. My study suggests that ginseng is a "slow opportunist", because while it benefits from sudden light increases, acclimation lags at least one growing season behind canopy changes. American ginseng is surprisingly resilient in the face of a discrete environmental shift and may benefit from forest management strategies that mimic the natural disturbance regimes common in mature forests throughout its range.
木材采伐后林下光照环境迅速变化，虽然许多林下物种利用额外的光照并从中受益，但这种反应在喜阴物种中并不普遍。我研究了块状皆伐木材采伐对一种专性林下物种的生理和生长的影响，以确定通过木材采伐造成的干扰是否为生理应激源，或者这种干扰是否能为林下物种带来生理益处并促进其生长。在块状皆伐木材采伐前的一个夏天和采伐后的两个夏天，对森林冠层结构以及西洋参的光合作用、呼吸作用、水分利用效率、气孔导度和生长速率进行了量化。木材采伐后的存活率低于未受干扰种群的观察值；然而，存活个体在采伐后的生长增加，生长随着冠层开阔度的增加而增加。光响应曲线以及光合作用和呼吸速率表明，木材采伐后的生长季节中，植物并未很好地适应较高的光照水平，而是在采伐后的两个生长季节才适应。木材采伐后，相对生长速率与最大光合作用形成正线性关系。我的研究表明，人参是一种“缓慢的机会主义者”，因为虽然它从光照突然增加中受益，但适应过程至少比冠层变化滞后一个生长季节。面对离散的环境变化，西洋参出人意料地具有恢复力，并且可能受益于模仿其分布范围内成熟森林常见自然干扰模式的森林管理策略。
