森林と農地で異なる土壌有機物変換応答を解明（Land Use Overrides Climatic Controls on SOM Transformations: Contrasting Responsiveness Between Forest and Cropland Ecosystems）

2026-06-10 中国科学院（CAS）

中国科学院亜熱帯農業研究所の李徳軍教授らの研究チームは、土壌有機態窒素（SON）の変換過程が気候変動へどのように応答するかを調べ、土地利用形態がその応答性を決定する主要因であることを明らかにした。研究では、中国南西部の亜熱帯地域に設置した森林と農地の30組の調査区を対象に、土壌理化学特性、窒素変換速度、機能遺伝子量、酵素活性を測定し、統計モデルを用いて解析した。その結果、自然林では鉱物－酵素相互作用やリン制限の影響により、気温上昇や降水増加に対して窒素循環が高感度に反応し、窒素流亡リスクが高まることが判明した。一方、集約農地では施肥や耕起による緩衝効果により気候変動の影響が抑制されるものの、窒素循環プロセス間の連携が弱まる傾向が認められた。今後の気候変動下では、森林ではリン制限を考慮した窒素管理が重要となり、農地では窒素利用効率を維持するための最適な養分管理が求められる。本研究は土地利用形態を考慮した窒素管理戦略や地球規模変動モデルの高度化に貢献する成果である。

＜関連情報＞

土地利用は土壌有機窒素変換に対する気候制御を凌駕する：森林生態系と農耕地生態系における応答性の違い Land use overrides climatic controls on soil organic nitrogen transformations: Contrasting responsiveness between forest and cropland ecosystems

Xinyi Yang, Pengpeng Duan, Andrew T. Nottingham, Wolfgang Wanek, Lettice C. Hicks, Luiz A. Domeignoz-Horta, Peilei Hu, Kongcao Xiao, Xunyang He, Kelin Wang, Dejun Li
Function Ecology Published: 01 June 2026
DOI:https://doi.org/10.1111/1365-2435.70366

Abstract

Soil organic nitrogen (SON) transformation is critical for global nutrient cycling and ecosystem productivity, yet how its responsiveness to climate change differs across diverse land use types remains poorly resolved.
We measured gross protein depolymerization (GPD), microbial N growth, gross N mineralization (GNM) and microbial N use efficiency (NUE) in paired forest and cropland soils along a broad climatic gradient in subtropical China to quantify differential climate associations and identify governing biogeochemical controls.
Forest soils exhibited substantially higher GPD (82%), microbial growth (132%) and NUE (26%) compared to adjacent croplands, while GNM rates were similar between land uses. Across the observed spatial climate gradient, SON transformations in forests showed strong positive co-variation with climate: GPD, N_growth and GNM increased with mean annual temperature (MAT) and mean annual precipitation (MAP) (slopes for MAT = 0.59, 0.84, 0.49; for MAP = 0.55, 0.62, 0.23), whereas NUE declined with both MAT and MAP (slopes = −0.68 and −0.63, respectively). In contrast, cropland SON processes were largely insensitive to MAT and MAP except that N_growth and NUE increased modestly with MAT. Mechanistic analyses indicated contrasting regulatory pathways: in forests, climatic effects were transmitted mainly through mineral–enzyme interactions (e.g. iron/aluminium oxides modulating protease activity) and resource stoichiometry (e.g. dissolved organic carbon:available phosphorus ratio), with GPD tightly coupled to N_growth and GNM and acting as a rate-limiting step. In croplands, temperature effects were largely indirect, operating through base cation to iron/aluminium-oxide ratios, resource availability (free amino acids, carbon:N ratio), and microbial functional gene abundances, yielding a decoupling of depolymerization from downstream processes.
These results show that land use strongly modulates the climate-associated responsiveness of SON transformations: forest soils are more vulnerable to climate-driven changes in N cycling than intensively managed croplands. Our findings have implications for land-use-specific management and for improving predictions of N dynamics under global change.