Flood-Induced Changes in Soil Microbial Functions as Modified by Plant Diversity

Flooding frequency is predicted to increase during the next decades, calling for a better understanding of impacts on terrestrial ecosystems and for developing strategies to mitigate potential damage. Plant diversity is expected to buffer flooding effects by providing a broad range of species’ responses. Here we report on the response of soil processes to a severe summer flood in 2013, which affected major parts of central Europe. We compared soil microbial respiration, biomass, nutrient limitation and enzyme activity in a grassland biodiversity experiment in Germany before flooding, one week and three months after the flood. Microbial biomass was reduced in the severely flooded plots at high, but not at low plant functional group richness. Flooding alleviated microbial nitrogen limitation, presumably due the input of nutrient-rich sediments. Further, the activity of soil enzymes including 1,4-β-N-acetylglucosaminidase, phenol oxidase and peroxidase increased with flooding severity, suggesting increased chitin and lignin degradation as a consequence of the input of detritus in sediments. Flooding effects were enhanced at higher plant diversity, indicating that plant diversity temporarily reduces stability of soil processes during flooding. The long-term impacts, however, remain unknown and deserve further investigation.

预计未来数十年内洪水发生频率将呈上升趋势，这要求我们更深入地理解洪水对陆地生态系统的影响，并制定策略以减轻潜在危害。植物多样性可通过提供多样的物种响应模式，缓冲洪水带来的影响。本研究报道了2013年夏季一场席卷中欧大部分区域的严重洪水对土壤过程的影响。我们在德国的一项草地生物多样性实验中，对比了洪水前、洪水后1周及3个月时的土壤微生物呼吸（soil microbial respiration）、土壤微生物量（microbial biomass）、养分限制状况与酶活性。在植物功能群丰富度较高的样地中，严重水淹样地的土壤微生物量有所降低，而在植物功能群丰富度较低的样地中则无此现象。洪水缓解了微生物的氮限制状况，这可能是由于富含养分的沉积物输入所致。此外，包括1,4-β-N-乙酰氨基葡萄糖苷酶（1,4-β-N-acetylglucosaminidase）、酚氧化酶（phenol oxidase）与过氧化物酶（peroxidase）在内的土壤酶活性随洪水严重程度升高而增强，表明沉积物输入的碎屑可促进几丁质与木质素的降解。在植物多样性更高的样地中，洪水的影响更为显著，这表明洪水期间植物多样性会暂时降低土壤过程的稳定性。不过，洪水对土壤过程的长期影响仍不明确，有待进一步研究。