Is the growth of temperate forest trees enhanced along an ambient nitrogen deposition gradient?

Abstract

Abstract. The extent to which atmospheric N deposition is enhancing primary production and CO 2 sequestration along the ambient N deposition gradients found within many regional temperate forest ecosystems remains unknown. We used tree diameter measurements from 1984 and 2004, allometric equations, and estimates of wet N deposition from 32 permanent plots located along an ambient N deposition gradient in the Adirondack Park, New York, USA, to determine the effects of N deposition on the basal area and woody biomass increments (BAI and WBI, respectively) of individual stems from all the major tree species. Nitrogen deposition had either a neutral or positive effect on BAI and WBI, with the positive effects especially apparent within the smaller size classes of several species. The nature of these growth responses suggests that other co-varying factors (e.g., temperature, tropospheric ozone, soil acidification) may be partially counteracting the species-dependent fertilization effect of N deposition that was suggested by recent foliar N data across this gradient. Nevertheless, in documenting a fertilization effect from chronic, low-level, ambient rates of N deposition, this study underscores the need for more research on how N deposition is affecting rates of primary production, CO 2 sequestration, and even vegetation dynamics in many forests worldwide.

Growth responses of trees and understory plants to nitrogen fertilization in a subtropical forest in China

“…Although a number of studies have reported a general positive effect of N enrichment on plants in N-limited forests and a negative effect of excess N (e.g. Aber et al, 1998;Högberg et al, 2006;Gilliam, 2006;Thomas et al, 2010), specific responses of plants appeared to be highly growth form-dependent and ecosystem-dependent (LeBauer and Treseder, 2008;Bedison and McNeil, 2009;Dirnböck et al, 2014).…”

How climatic conditions, site, and soil characteristics affect tree growth and critical loads of nitrogen for northeastern tree species

“…Several sources indicate that red maple growth and survival increases with increasing N deposition. Thomas et al (2010) found increased growth and survival with increased deposition from 3 to 11 kg N ha -1 yr -1 , while Bedison and McNeil (2009) . In West Virginia, red maple basal area increased with deposition from 12 to 14 kg N ha -1 yr -1 (Elias 2008).…”

氮添加对亚热带次生常绿阔叶林扁刺栲细根生物量、寿命和形态的短期影响

“…2%, 但由于细根周转快速, 消耗了20%−30%的年净 初级生产力 (Jackson et al, 1997;Poorter et al, 2011), (Eissenstat et al, 2000), 这 在氮沉降梯度研究和元素添加试验中得到了广泛证 明 (Ostonen et al, 2007;Li et al, 2015)。 近几十年来, 由于工农业发展和化石燃料的大 量燃烧导致氮沉降在全球范围增加, 人类活动极大 地干扰了全球氮循环 (Galloway & Cowling, 2002;Galloway et al, 2004), 对森林生态系统物质循环造 成了潜在的巨大影响(吕超群等, 2007)。大量研究表 明, 日益增加的氮沉降会增加土壤氮素可利用性, 多数情况会下提高植被地上部分生产力 (Bedison & Mcneil, 2009)。然而森林植物根系对土壤氮素增加 的响应方向和程度却存在很大的不确定性。有研究 表明氮添加增加了根系寿命, 减缓了细根周转速率 (Jourdan et al, 2008;于水强等, 2009;Mei et al, 2010), 但也有研究观察到与之相反的结果 (Johnson et al, 2000;Wang et al 2012 …”