Data_Sheet_1_Testate Amoeba Species- and Trait-Based Transfer Functions for Reconstruction of Hydrological Regime in Tropical Peatland of Central Sumatra, Indonesia.DOCX

Tropical peatlands play an important role in carbon storage and in water regulation on a landscape level. However, our understanding of their ecology and long-term hydrological dynamics remains limited. Transfer functions, constructed on the basis of biological indicators (proxies) with known ecological preferences, allow us to infer past environmental conditions and serve as a basis for prediction of future changes in peatlands. Here, we use testate amoebae to develop the first species- and functional trait-based transfer functions for the Southeast Asia. This provides a valuable tool for future reconstructions of past hydrological changes in tropical peatlands, their development, and climatic changes. Surface samples for testate amoeba analysis were taken in various biotopes along two transects across the Sungai Buluh peatland in Central Sumatra. The following environmental characteristics were measured: water table depth (WTD), light intensity, pH, total C and N concentrations. The analysis of the surface samples revealed 145 morphotypes of testate amoebae belonging to 25 genera. A significant fraction of the variance in testate amoeba morphotypes and functional trait composition was explained by WTD and pH. The wide WTD range (0–120 cm) seems more valuable for reconstruction than the extremely short pH gradient (2.5–3.8). Thus, transfer functions were developed only for WTD, based on weighted averaging model for morphotypes and multiple linear regression for functional traits. Both species- and trait-based model have a predictive ability for WTD reconstruction. For traits, the best performance of the model was reached by including five morphological traits: shell width, aperture shape, aperture invagination, shell shape and shell compression. We discuss the ecology of several taxa and highlight the traits, which reflect hydrological changes in this system. Though the hydrological preferences of some species are similar to those in high and middle latitude peatlands, we argue that latitudinal differences in morphospecies composition and variations in environmental relationships of species require the development of region-specific transfer functions. Moreover, our results indicate that ecological preferences of morphotypes within morphospecies also need to be considered and included in future studies.

热带泥炭地在景观尺度的碳储存与水文调节中发挥着关键作用。然而，当前学界对其生态学机制与长期水文动态的认知仍存在显著局限。基于具有明确生态偏好的生物指示物（代用指标，proxy）构建的转换函数（transfer function），可用于推演过去的环境条件，并作为预测泥炭地未来变化的理论基础。本研究以东南亚为研究区域，首次利用有壳变形虫（testate amoebae）构建了基于物种和功能性状的转换函数，为后续热带泥炭地古水文变化、泥炭地发育过程以及气候变化的重建提供了极具价值的研究工具。研究团队在苏门答腊中部的双溪武鲁（Sungai Buluh）泥炭地沿两条样带的不同生境中，采集了用于有壳变形虫分析的表层沉积物样品。本次测定的环境特征包括：地下水位埋深（water table depth, WTD）、光照强度、pH值、总碳（total C）与总氮（total N）浓度。对表层样品的分析共鉴定出隶属于25个属的145种有壳变形虫形态型。有壳变形虫形态型与功能性状组成的显著变异可由地下水位埋深和pH值解释。相较于极窄的pH梯度范围（2.5–3.8），跨度更广的地下水位埋深区间（0–120 cm）对古环境重建的参考价值更高。因此，本研究仅针对地下水位埋深构建转换函数：针对形态型采用加权平均模型，针对功能性状则采用多元线性回归模型。基于物种和基于性状的两类模型均具备地下水位埋深重建的预测能力。就功能性状而言，纳入壳宽、口孔形状、口孔内陷、壳形以及壳压缩性这5种形态性状时，模型可达到最优预测性能。本研究讨论了多个类群的生态学特征，并重点指出了能够反映该系统水文变化的功能性状。尽管部分物种的水文偏好与中高纬度泥炭地中的同类物种相似，但我们认为，由于形态物种组成存在纬度差异，且物种与环境之间的关联存在变异，因此需要开发针对特定区域的转换函数。此外，本研究结果还表明，未来的研究中还需考虑并纳入同一形态物种内不同形态型的生态偏好差异。