Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas, 79968, USA.
Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YW, UK.
Ecology. 2017 May;98(5):1361-1376. doi: 10.1002/ecy.1790. Epub 2017 Apr 7.
Rapid arctic vegetation change as a result of global warming includes an increase in the cover and biomass of deciduous shrubs. Increases in shrub abundance will result in a proportional increase of shrub litter in the litter community, potentially affecting carbon turnover rates in arctic ecosystems. We investigated the effects of leaf and root litter of a deciduous shrub, Betula nana, on decomposition, by examining species-specific decomposition patterns, as well as effects of Betula litter on the decomposition of other species. We conducted a 2-yr decomposition experiment in moist acidic tundra in northern Alaska, where we decomposed three tundra species (Vaccinium vitis-idaea, Rhododendron palustre, and Eriophorum vaginatum) alone and in combination with Betula litter. Decomposition patterns for leaf and root litter were determined using three different measures of decomposition (mass loss, respiration, extracellular enzyme activity). We report faster decomposition of Betula leaf litter compared to other species, with support for species differences coming from all three measures of decomposition. Mixing effects were less consistent among the measures, with negative mixing effects shown only for mass loss. In contrast, there were few species differences or mixing effects for root decomposition. Overall, we attribute longer-term litter mass loss patterns to patterns created by early decomposition processes in the first winter. We note numerous differences for species patterns between leaf and root decomposition, indicating that conclusions from leaf litter experiments should not be extrapolated to below-ground decomposition. The high decomposition rates of Betula leaf litter aboveground, and relatively similar decomposition rates of multiple species below, suggest a potential for increases in turnover in the fast-decomposing carbon pool of leaves and fine roots as the dominance of deciduous shrubs in the Arctic increases, but this outcome may be tempered by negative litter mixing effects during the early stages of encroachment.
由于全球变暖，北极地区的植被迅速变化，落叶灌木的覆盖度和生物量增加。灌木丰度的增加将导致凋落物群落中灌木凋落物的比例增加，从而可能影响北极生态系统的碳周转速率。我们通过检查落叶灌木（桦木）的叶片和根系凋落物的分解，研究了落叶灌木凋落物对分解的影响，包括特定物种的分解模式以及桦木凋落物对其他物种分解的影响。我们在阿拉斯加北部的湿润酸性冻原进行了为期 2 年的分解实验，在那里我们单独和混合桦木凋落物分解了 3 种冻原物种（Vaccinium vitis-idaea、Rhododendron palustre 和 Eriophorum vaginatum）。我们使用 3 种不同的分解措施（质量损失、呼吸作用、胞外酶活性）来确定叶片和根系凋落物的分解模式。我们报告说，桦木叶片凋落物的分解速度比其他物种快，这一结论得到了 3 种分解措施的支持。混合效应在这些措施中不太一致，仅在质量损失方面表现出负混合效应。相比之下，根系分解的物种差异或混合效应较少。总的来说，我们将长期凋落物质量损失模式归因于第一个冬季早期分解过程所产生的模式。我们注意到叶片和根系分解的物种模式有许多差异，这表明从叶片凋落物实验中得出的结论不能推断到地下分解。桦木叶片凋落物的高分解率与多个物种根系分解率的相似性表明，随着北极地区落叶灌木的优势增加，快速分解的碳库中凋落物和细根的周转率可能会增加，但在侵入的早期阶段，负的凋落物混合效应可能会缓和这种结果。
