Litter decomposition is a key process of the carbon cycle in terrestrial and aquatic ecosystems. The dominant conceptual model of litter decomposition assumes that environmental conditions, litter traits, and decomposer composition control litter decomposition in a decreasing order, yet whether this hierarchical model applies to both invasive and native plant species is unknown. Here, by comparing a widespread invasive plant and its native counterpart in Chinese coastal saltmarshes, we aimed to examine whether the hierarchy of factors controlling litter decomposition varies with plant species in the face of plant invasions. Leaf litter of invasive Spartina alterniflora and native Phragmites australis was collected across an 18° latitudinal range to capture wide variation in litter traits. These leaf litter samples were transported to three saltmarsh sites of different latitudes and were incubated in litterbags varying in mesh size (0.1, 2, and 5 mm) to manipulate decomposer composition. After 90-day incubation, we found a parallel latitudinal pattern in leaf litter decomposition rate (k) between S. alterniflora and P. australis regardless of saltmarsh site and mesh size. Nonetheless, the k value of S. alterniflora was 2.2-fold higher than that of P. australis. Moreover, there was a shift in the hierarchy of factors controlling k values between S. alterniflora and P. australis: environmental conditions (climate and soil) dominated other factors in P. australis, whereas litter traits contributed more than environmental conditions in S. alterniflora. Overall, our findings show that leaf litter decomposition and its dominant controlling factors across broad geographical ranges can vary with plant invasions, having important implications for managing invasive plants in the context of conserving coastal blue carbon.
凋落物分解是陆地和水域生态系统碳循环的关键过程。凋落物分解模型通常认为控制凋落物分解速率最重要的驱动因素依次为环境条件、凋落物性状和分解者组成。然而这一凋落物分解层级模型的适用性是否在入侵植物和土著植物间具有差异尚不清楚。本研究通过比较中国滨海盐沼中广泛分布的入侵植物互花米草和土著植物芦苇, 探究控制植物凋落物分解的驱动因子层级关系是否因物种而异。本研究跨18°纬度采集了两种植物的叶片凋落物以获得较大变异的凋落物性状, 通过选择三个不同纬度的分解地(东营、上海、漳州)以控制分解环境, 同时选择三种不同孔径(0.1、2和5 mm)的凋落物袋以控制分解者类群。经过90天的野外分解实验, 结果表明:(1)互花米草叶片凋落物分解速率是芦苇叶片凋落物的2.2倍; (2)无论分解地和凋落物袋网目大小, 互花米草与芦苇的叶片凋落物分解速率均随凋落物来源地纬度的升高而增加; (3)控制凋落物分解的因子层级关系因物种而异, 环境条件主导控制芦苇凋落叶分解, 而凋落物性状在控制互花米草凋落叶分解中起主要作用。综上, 本研究表明在大地理尺度上植物入侵会改变凋落物分解速率及其主导控制因子, 这对保护滨海蓝碳生态系统目标下的入侵植物管理具有重要启示。.
Keywords: Spartina alterniflora; decomposition; invasive plant; latitudinal pattern; leaf litter; management; saltmarsh.
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