Benalcazar Paul, Seuradge Brent, Diochon Amanda C, Kolka Randall K, Phillips Lori A
Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada.
Agriculture and Agri-Food Canada, Harrow Research and Development Centre, Harrow, ON, Canada.
Environ Microbiome. 2024 May 11;19(1):32. doi: 10.1186/s40793-024-00576-3.
Boreal regions are warming at more than double the global average, creating opportunities for the northward expansion of agriculture. Expanding agricultural production in these regions will involve the conversion of boreal forests to agricultural fields, with cumulative impacts on soil microbial communities and associated biogeochemical cycling processes. Understanding the magnitude or rate of change that will occur with these biological processes will provide information that will enable these regions to be developed in a more sustainable manner, including managing carbon and nitrogen losses. This study, based in the southern boreal region of Canada where agricultural expansion has been occurring for decades, used a paired forest-adjacent agricultural field approach to quantify how soil microbial communities and functions were altered at three different stages post-conversion (< 10, > 10 and < 50, and > 50 years). Soil microbial functional capacity was assessed by quantitative PCR of genes associated with carbon (C), nitrogen, and phosphorous (P) cycling; microbial taxonomic diversity and community structure was assessed by amplicon sequencing.
Fungal alpha diversity did not change, but communities shifted from Basidiomycota to Ascomycota dominant within the first decade. Bacterial alpha diversity increased, with Gemmatimonadota groups generally increasing and Actinomycetota groups generally decreasing in agricultural soils. These altered communities led to altered functional capacity. Functional genes associated with nitrification and low molecular weight C cycling potential increased after conversion, while those associated with organic P mineralization potential decreased. Stable increases in most N cycling functions occurred within the first decade, but C cycling functions were still changing 50 years post conversion.
Microbial communities underwent a rapid shift in the first decade, followed by several decades of slower transition until stabilizing 50 years post conversion. Understanding how the microbial communities respond at different stages post-conversion improves our ability to predict C and N losses from emerging boreal agricultural systems, and provides insight into how best to manage these soils in a way that is sustainable at the local level and within a global context.
北方地区的变暖速度超过全球平均水平的两倍，为农业向北扩张创造了机会。在这些地区扩大农业生产将涉及把北方森林转变为农田，对土壤微生物群落及相关生物地球化学循环过程产生累积影响。了解这些生物过程将会发生的变化幅度或速率，将为以更可持续的方式开发这些地区提供信息，包括管理碳和氮的损失。本研究以加拿大北方南部地区为基础，该地区的农业扩张已经持续了数十年，采用了森林与相邻农田配对的方法，来量化在转化后的三个不同阶段（<10年、>10年且<50年、>50年）土壤微生物群落和功能是如何改变的。通过对与碳（C）、氮和磷（P）循环相关基因的定量PCR来评估土壤微生物功能能力；通过扩增子测序来评估微生物分类多样性和群落结构。
真菌的α多样性没有变化，但在最初十年内，群落从担子菌门主导转变为子囊菌门主导。细菌的α多样性增加，在农业土壤中，芽单胞菌门菌群总体增加，放线菌门菌群总体减少。这些改变的群落导致了功能能力的改变。与硝化作用和低分子量碳循环潜力相关的功能基因在转化后增加，而与有机磷矿化潜力相关的功能基因减少。大多数氮循环功能在最初十年内稳定增加，但碳循环功能在转化后50年仍在变化。
微生物群落在最初十年经历了快速转变，随后几十年转变较慢，直到转化后50年才稳定下来。了解微生物群落在转化后不同阶段的反应，提高了我们预测新兴北方农业系统中碳和氮损失的能力，并为如何以在地方层面和全球范围内可持续的方式最佳管理这些土壤提供了见解。
