Decay rates of leaf litters from arbuscular mycorrhizal trees are more sensitive to soil effects than litters from ectomycorrhizal trees

Abstract

1.While it is well established that leaf litter decomposition is controlled by climate and substrate quality at broad spatial scales, conceptual frameworks that consider how local-scale factors affect litter decay in heterogeneous landscapes are generally lacking. 2. A critical challenge in disentangling the relative impacts of and interactions among local-scale factors is that these factors frequently covary due to feedbacks between plant and soil communities. For example, forest plots dominated by trees that associate with ectomycorrhizal (ECM) fungi often differ from those dominated by trees that associate with arbuscular mycorrhizal (AM) fungi in terms of their litter quality, microbial community structure and inorganic nutrient availability. Here, we evaluate the extent to which such factors alter leaf litter decomposition rates. 3. To characterize variations in decomposition rates, we compared decay rates of high-quality litter (maple; AM) and low-quality litter (oak; ECM) across forest plots representing a gradient in litter matrix quality and nitrogen (N) availability driven by the relative proportions of AM and ECM trees in each plot. In experiment two, we added litter from two AM and three ECM tree species to forest plots with either a high-quality litter matrix and high N availability (i.e. AM-dominated plots) or a low-quality litter matrix and low N availability (i.e. ECM-dominated plots). In both experiments, we found that AM litter decomposed more rapidly than ECM litter, and this effect was enhanced in AM-dominated plots. 4. Then, to separate the contributions of litter matrix effects from N availability effects, we added N fertilizer to a subset of plots from experiment two. Nitrogen addition increased decay rates of highquality litter across all sites, but had no effect on low-quality litter, suggesting that low N availability, not litter matrix quality, constrains decomposition of high-quality litters. Hence, N availability appears to alter litter decomposition patterns independently of litter matrix properties. 5. Synthesis. Our results indicate that shifts in the relative abundance of ECM-and AM-associated trees in a plot or stand have the potential to affect litter decay rates through both changes in litter quality as well as through alterations of the local-scale soil environment.

Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions

“…Variation in fine-scale soil conditions has been proposed to explain differences in local decomposition rates [7, 42], but we found mixed evidence to extend this hypothesis into fire-dominated systems. We found significant differences in decomposition rates across landscape positions (i.e.…”

“…Historically, climactic variables like precipitation and temperature have been thought to exert the strongest control over decomposition rates at the global scale [3, 4], but there has recently been a push to move away from this climate-centric paradigm and incorporate local, biotic regulatory factors into decomposition frameworks [5, 6]. Within ecosystems, the effect of litter quality on decomposition is modulated by local soil environmental conditions and microclimate [7, 8]. Across biomes, litter decomposition may be predominantly explained by litter quality, itself which may be related to the life history strategies of individual species [6].…”

“…For example, in tallgrass prairie, soil microbial activity was enhanced following burning, but this effect was dampened as the quality of litter inputs decreased with repeated, annual burns [33]. An empirical framework to understand how micro-environmental characteristics and plant litter traits interact to influence local litter decomposition rates [7] may have implications for understanding nutrient provisioning within and across ecosystems.…”

森林土壤碳氮循环过程的新视角: 丛枝与外生菌根树种的作用

“…N的输入、 稳定及输出等过程, 从而造成不同菌根类 型森林土壤C、N循环的差异 (Austin & Zanne, 2015;Brzostek et al, 2015;Midgley et al, 2015;Moore et al, 2015;Soudzilovskaia et al, 2015)。然而, 由于试 验方法、研究尺度等限制, 不同菌根类型树种对森 林土壤C、 N循环过程的影响机制仍存在较大的不确 定性 (Moore et al, 2015) (Vesterdal et al, 2013;Lin et al, 2016)。对AM和EM森林凋落物层C 储量差异的研究结果较为一致, 均表现为AM小于 EM (图1, Vesterdal et al, 2013;Lin et al, 2016)。两 个菌根类型树种凋落物C输入量基本相同; 而由于 AM树种凋落物质量较高(主要因其C或木质素浓度 与N浓度的比值均显著小于EM树种), 质量损失较 快, 从而使AM森林凋落物层C输出量高于EM森林 (Cornelissen et al, 2001;Lin et al, 2016;Taylor et al, …”

“…。菌根真菌不仅对植物的 存活和生长具有重要作用, 而且其与土壤自由微生 物的相互作用在森林生态系统的生态过程(尤其是 土壤碳(C)、氮(N)循环)中也扮演着重要角色 (Orwin et al, 2011;Veresoglou et al, 2012;Phillips et al, 2013;Bardgett et al, 2014;McCormack et al, 2015;Laliberté, 2016)。由于森林土壤固定的C、N库容巨 大 (Lal et al, 2015), 森林生态系统AM、EM树种相 对丰度随全球变化而发生的改变很可能会导致陆地 生 态 系 统 生 物 地 球 化 学 循 环 过 程 的 显 著 变 化 (Phillips et al, 2012;石兆勇等, 2012b;Terrer et al, 2016Terrer et al, , 2017)。阐明不同菌根类型森林土壤C、N循环 的差异及其影响机制, 对于提高森林生产力、预测 森林生态系统对全球变化的响应等具有重要意义 (Averill et al, 2014;Midgley et al, 2015;Soudzilovskaia et al, 2015)。 与树种的叶习性和谱系分类(例如针叶裸子植 物与阔叶被子植物)相比, 按菌根类型进行树种分 类能更好地解释森林生态系统土壤C、 N循环的变异 性乃至森林生产力对全球变化的响应 (Phillips et al, 2013;Midgley & Phillips, 2014;Terrer et al, 2016, …”