Effects of Long-Term Soil Warming on Ecosystem Function at Harvard Forest 2019

Across biomes, soil biodiversity promotes ecosystem functions. However, whether this relationship will be maintained within ecosystems under climate change is uncertain. Here, using two long-term soil warming experiments, we investigated how warming affects the relationship between ecosystem functions and bacterial diversity across seasons, soil horizons, and warming duration. Soils were sampled from these warming experiments located at the Harvard Forest Long-Term Ecological Research (LTER) site, where soils had been heated +5°C above ambient for 13 or 28 years at the time of sampling. We assessed seven measurements representative of different ecosystem functions and nutrient pools. We also surveyed bacterial community diversity. We found that ecosystem function was significantly affected by season, with autumn samples having a higher intercept than summer samples in our model, suggesting a higher overall baseline of ecosystem function in the fall. The effect of warming on bacterial diversity was similarly affected by season, where warming in the summer was associated with decreased bacterial evenness in the organic horizon. Despite the decreased bacterial evenness in the warmed plots, we found that the relationship between ecosystem function and bacterial diversity was unaffected by warming or warming duration. Our findings highlight that season is a consistent driver of ecosystem function as well as a modulator of climate change effects on bacterial community evenness.

在各类生物群系中，土壤生物多样性可促进生态系统功能。然而，在气候变化背景下，这种关联能否在生态系统中维持尚不明朗。本研究依托两项长期土壤增温实验，探究了增温如何在季节、土壤发生层以及增温时长三个维度上，调控生态系统功能与细菌多样性之间的关联。土壤样本采集自哈佛森林长期生态研究站（Long-Term Ecological Research, LTER），该站点的土壤在采样时已在高于环境温度5℃的条件下持续增温13年或28年。本研究针对7项表征不同生态系统功能与养分库的指标进行了测定，同时测定了细菌群落多样性。研究发现，生态系统功能显著受季节调控：本研究模型中秋季样本的截距高于夏季样本，表明秋季生态系统功能的整体基线水平更高。增温对细菌多样性的影响同样受季节调控：夏季增温会导致有机发生层的细菌均匀度降低。尽管增温样地的细菌均匀度有所下降，但本研究发现，生态系统功能与细菌多样性之间的关联并未受到增温处理或增温时长的影响。本研究结果表明，季节既是驱动生态系统功能的稳定因子，同时也是调控气候变化对细菌群落均匀度影响的调节因子。