2025-10-16 中国科学院(CAS)
中国科学院西北環境資源研究院と米国の共同研究チームは、乾燥地の主要砂丘低木が成長とともに衰退する原因を解明した。中国・騰格里砂漠南東縁の2種の低木を調査した結果、成長サイズの増加に伴い導管輸送効率と光合成能が低下し、非構造性炭水化物量は一定であることが分かった。つまり、枯死や成長減退は炭水化物枯渇ではなく水輸送・炭素固定の制約が主因であると示された。研究は乾燥地植生の進化理解と砂漠化防止策に新知見を提供する。成果は『New Phytologist』誌に掲載。
<関連情報>
- https://english.cas.cn/newsroom/cas_media/202510/t20251016_1089558.shtml
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.70615
乾燥地の低木におけるサイズの減少は、水力効率と炭素同化の低下と関連しており、非構造炭水化物の枯渇とは関連していない Size-related decline in dryland shrubs is related to reductions in hydraulic efficiency and carbon assimilation and not nonstructural carbohydrate depletion
Hongxia Zhang, Kevin R. Hultine, Xinrong Li, Jianqiang Huo, Jingyao Sun, Nate G. McDowell
New Phytologist Published: 29 September 2025
DOI:https://doi.org/10.1111/nph.70615
Summary
- Plant growth and survival are fundamentally constrained by water transport from roots to leaves, impacting carbon assimilation and associated labile carbon pools. However, physiological constraints on growth and survival vary with plant age, due to changes in metabolic sinks and increases in hydraulic path length from rhizosphere to canopy.
- We investigated crown dieback, growth, hydraulics, carbon assimilation and nonstructural carbohydrate (NSC) storage in relation to increasing basal diameter of two dominant shrub species (Caragana korshinskii and Artemisia ordosica) at the southeastern edge of the Tengger Desert, China. The aim was to identify mechanisms of decreased performance with plant size in dryland shrubs.
- Clear contrasts in stomatal regulation of leaf water potentials were detected between species. Despite these contrasts, radial growth, hydraulic transport efficiency (Ks), and carbon assimilation similarly declined in both species with increasing plant size, while NSC reserves remained unchanged. Xylem embolism (percentage loss of conductivity) increased with plant size, resulting in significant reductions in carbon assimilation in both species.
- Results indicate that hydraulic and potentially carbon assimilation constraints, rather than NSC depletion, govern growth-related dryland shrub decline. These findings improve our understanding of how population demography impacts dryland forest response to climate change.
