Data from: Environmental factors and traits that drive plant litter decomposition do not determine home-field advantage effects

The ‘home-field advantage’ (HFA) hypothesis predicts that plant litter is decomposed faster than expected underneath the plant from which it originates (‘home’) than underneath other plants (‘away’), because decomposer communities are specialized to break down litter from the plants they associate with. However, empirical evidence shows that the occurrence of HFA is highly variable, and the reasons for this are little understood. In our study we progress our understanding by investigating whether HFA is stronger for more recalcitrant litter types and under colder conditions and how soil properties and plant functional traits affect the magnitude and direction of HFA. In subarctic tundra in northern Sweden we set up a reciprocal transplant litter decomposition experiment along an elevational gradient where three highly contrasting vegetation types (heath, meadow and Salix) occur at all elevations, and where temperature decreases strongly with elevation. In this study, we used a litter bag approach where litters from each elevation × vegetation type combination were decomposed in all combinations of elevation × vegetation type. We also measured community-level plant functional traits, such as leaf and litter nutrient content. We determined soil biotic and abiotic properties, such as microbial biomass and soil nutrient content, in soil cores collected for each elevation × vegetation type combination. We found that mass loss increased with plant and litter nutrient content and with soil temperature. In contrast, the occurrence of HFA was limited in our study system, and its magnitude and direction could not be explained by vegetation type, elevation, plant traits or soil properties, despite these factors serving as powerful drivers of litter mass loss in our study. We conclude that although vegetation type and climate are major drivers of litter mass loss, they do not emerge as important determinants of HFA. Therefore, while rapid shifts in plant community composition or temperature due to global change are likely to influence litter mass loss directly by altering environmental conditions, plant trait spectra and litter quality, indirect effects of global change resulting from decoupling of specialist interactions between litter and decomposer communities appears to be of less importance.

“生境优势效应（home-field advantage, HFA）”假说预测，植物凋落物在其来源植株（即“本土生境”）下的分解速率快于在其他植株（即“外来生境”）下的预期分解速率，这是因为分解者群落专化于分解其所关联植物的凋落物。然而，现有实证研究表明HFA的发生存在高度变异性，其背后的机制尚不明晰。本研究旨在通过探究以下问题以推进对HFA的认知：HFA是否在更难降解的凋落物类型以及更寒冷的环境下更为显著，以及土壤属性与植物功能性状如何影响HFA的强度与方向。
我们在瑞典北部的亚北极苔原开展了沿海拔梯度的互惠移植凋落物分解实验，该梯度上的所有海拔均分布着三种差异显著的植被类型（灌丛、草甸与柳属（Salix）），且温度随海拔升高呈显著下降趋势。本研究采用凋落物袋法，将各海拔×植被类型组合的凋落物置于所有海拔×植被类型组合的生境中进行分解。我们还测定了群落水平的植物功能性状，如叶片与凋落物的养分含量。针对各海拔×植被类型组合采集的土芯，我们测定了土壤生物与非生物属性，例如微生物生物量与土壤养分含量。
研究发现，凋落物质量损失随植物与凋落物养分含量、土壤温度的升高而增加。与之相反，本研究系统中HFA的发生十分有限，且其强度与方向无法通过植被类型、海拔、植物性状或土壤属性来解释——尽管这些因素是本研究中凋落物质量损失的强驱动因子。
我们认为，尽管植被类型与气候是凋落物质量损失的主要驱动因子，但它们并未成为影响HFA的重要决定因素。因此，虽然全球变化导致的植物群落组成或温度的快速变化，可能通过改变环境条件、植物性状谱与凋落物质量直接影响凋落物质量损失，但由凋落物与分解者群落间专化互作解耦所引发的全球变化间接效应，其重要性似乎相对较低。