Global change progressively increases foliar nitrogen–phosphorus ratios in China's subtropical forests

• Published in: Global change biology 2024-02, Vol.30 (2), p.e17201-n/a
• Main Authors: Lai, Yuan, Tang, Songbo, Lambers, Hans, Hietz, Peter, Tang, Wenguang, Gilliam, Frank S., Lu, Xiankai, Luo, Xianzhen, Lin, Yutong, Wang, Shu, Zeng, Feiyan, Wang, Qi, Kuang, Yuanwen
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbon dioxide concentration; Community composition; Deciduous trees; Ecological function; Ecosystems; foliar N:P ratios; Forest ecosystems; Forests; global change; herbarium specimens; Nitrogen; Nutrient status; N–P imbalance; Phosphorus; Species; subtropical forests; Terrestrial ecosystems; Tropical forests; Vapor pressure; Vapour pressure
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.17201

Globally increased nitrogen (N) to phosphorus (P) ratios (N/P) affect the structure and functioning of terrestrial ecosystems, but few studies have addressed the variation of foliar N/P over time in subtropical forests. Foliar N/P indicates N versus P limitation in terrestrial ecosystems. Quantifying long‐term dynamics of foliar N/P and their potential drivers is crucial for predicting nutrient status and functioning in forest ecosystems under global change. We detected temporal trends of foliar N/P, quantitatively estimated their potential drivers and their interaction between plant types (evergreen vs. deciduous and trees vs. shrubs), using 1811 herbarium specimens of 12 widely distributed species collected during 1920–2010 across China's subtropical forests. We found significant decreases in foliar P concentrations (23.1%) and increases in foliar N/P (21.2%). Foliar N/P increased more in evergreen species (22.9%) than in deciduous species (16.9%). Changes in atmospheric CO2 concentrations (PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$), atmospheric N deposition and mean annual temperature (MAT) dominantly contributed to the increased foliar N/P of evergreen species, while PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$, MAT, and vapor pressure deficit, to that of deciduous species. Under future Shared Socioeconomic Pathway (SSP) scenarios, increasing MAT and PCO2$$ {\mathrm{P}}_{{\mathrm{CO}}_2} $$ would continuously increase more foliar N/P in deciduous species than in evergreen species, with more 12.9%, 17.7%, and 19.4% versus 6.1%, 7.9%, and 8.9% of magnitudes under the scenarios of SSP1‐2.6, SSP3‐7.0, and SSP5‐8.5, respectively. The results suggest that global change has intensified and will progressively aggravate N–P imbalance, further altering community composition and ecosystem functioning of subtropical forests. Foliar nitrogen to phosphorus ratios (N/P) indicate nutrient status of plants which affects ecosystem functioning. Using historical herbarium specimens collected across China's subtropical forests, we found significant increases in foliar N/P during 1920–2010, with evergreen species being enhanced more than deciduous species. The finding showed that forest plants in subtropical forests experienced progressively intensified N and P imbalance affected by global change factors like atmospheric CO2 concentrations, nitrogen deposition, and mean annual temperature.