Data from: The Automated Root Exudate System (ARES): a method to apply solutes at regular intervals to soils in the field

1) Root exudation is a key component of nutrient and carbon dynamics in terrestrial ecosystems. Exudation rates vary widely by plant species and environmental conditions but our understanding of how root exudates affect soil functioning is incomplete, in part because there are few viable methods to manipulate root exudates in situ. To address this, we devised the Automated Root Exudate System (ARES), which simulates increased root exudation by applying small amounts of labile solutes at regular intervals in the field.
2) The ARES is a gravity-fed drip irrigation system comprising a reservoir bottle connected via a timer to a micro-hose irrigation grid covering c. 1 m2; 24 drip-tips are inserted into the soil to 4-cm depth to apply solutions into the rooting zone. We installed two ARES subplots within existing litter removal and control plots in a temperate deciduous woodland. We applied either an artificial root exudate solution (RE) or a procedural control solution (CP) to each subplot for 1 min d-1 during two growing seasons. To investigate the influence of root exudation on soil carbon dynamics, we measured soil respiration monthly and soil microbial biomass at the end of each growing season.
3) The ARES applied the solutions at a rate of c. 2 L m-2 wk-1 without significantly increasing soil water content. The application of RE solution had a clear effect on soil carbon dynamics but the response varied by litter treatment. Across two growing seasons, soil respiration was 25% higher in RE compared to CP subplots in the litter removal treatment, but not in the control plots. By contrast, we observed a significant increase in microbial biomass carbon (33%) and nitrogen (26%) in RE subplots in the control litter treatment.
4) The ARES is an effective, low-cost method to apply experimental solutions directly into the rooting zone in the field. The installation of the systems entails minimal disturbance to the soil and little maintenance is required. Although we used ARES to apply root exudate solution, the method can be used to apply many other treatments involving solute inputs at regular intervals in a wide range of ecosystems.

1) 根系分泌物（Root exudation）是陆地生态系统养分与碳动态的关键组成部分。分泌物分泌速率因植物物种与环境条件差异存在显著波动，但当前学界对根系分泌物如何影响土壤功能的认知仍不完整，部分原因在于原位调控根系分泌物的可行方法较为匮乏。为解决这一问题，我们研发了自动化根系分泌物调控系统（Automated Root Exudate System, ARES），该系统可通过在野外定期施加少量易变性溶质，模拟根系分泌物分泌量的提升。
2) ARES为重力式滴灌系统，由储液瓶经定时器连接至覆盖约1平方米的微型软管灌溉网格构成；24个滴头插入土壤4厘米深度，将溶液施加至根系层。我们在温带落叶林的现有枯落物移除样地与对照样地内设置了两套ARES亚样地，并在两个生长季内，每日向每个亚样地施加人工根系分泌物溶液（RE）或程序对照溶液（CP），单次施加时长为1分钟。为探究根系分泌物对土壤碳动态的影响，我们每月测定土壤呼吸速率，并在每个生长季末测定土壤微生物生物量。
3) ARES的溶液施加速率约为2升·平方米⁻¹·周⁻¹，且未显著提升土壤含水量。施加RE溶液对土壤碳动态具有显著调控效应，但响应结果因枯落物处理方式而异。在两个生长季中，枯落物移除处理下的RE亚样地土壤呼吸速率较CP亚样地提升25%，但对照样地未呈现该差异；相较之下，对照枯落物处理的RE亚样地中，微生物生物量碳（提升33%）与氮（提升26%）均出现显著增长。
4) ARES是一种可在野外直接向根系层施加实验溶液的高效低成本方法。该系统的安装对土壤扰动极小，且日常维护需求极低。尽管本研究利用ARES施加根系分泌物溶液，但该方法可推广至各类生态系统中，用于定期施加多种涉及溶质输入的其他实验处理。