# Diagnosing Phosphorus Limitation in Subtropical Forests in China under Climate Warming  
[PERSON]  
1 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; [EMAIL_ADDRESS] (N.W. ); [EMAIL_ADDRESS] (S.W. ); [EMAIL_ADDRESS] (H.H. ); [EMAIL_ADDRESS] (Z.W. ); [EMAIL_ADDRESS] (F.Y)  
[PERSON]  
1 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; [EMAIL_ADDRESS] (N.W. ); [EMAIL_ADDRESS] (S.W. ); [EMAIL_ADDRESS] (H.H. ); [EMAIL_ADDRESS] (Z.W. ); [EMAIL_ADDRESS] (F.Y)  
[PERSON]  
4 Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China; [EMAIL_ADDRESS] 4 Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; [EMAIL_ADDRESS] 5 College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China 6 Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 61000, China; [EMAIL_ADDRESS] 7 State Key Laboratory of Vegetation and Environment Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; [EMAIL_ADDRESS] 8 Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; [EMAIL_ADDRESS] * Correspondence: [EMAIL_ADDRESS] *  
C, nitrogen (N) and P in plant and soil affects assimilation and allocation of C in plant and ultimately affects the functioning of terrestrial ecosystems and the absorption of CO\({}_{2}\)[4; 5]. P is derived primarily from rock weathering, and it is not clear if there is additional external P entering the ecosystem due to climate warming. However, the increase of C in ecosystem due to climate warming is certain, which implies that the ecosystem will consume more P to maintain the consistent C:P ratio. Therefore, climate warming may result in the P limitation in ecosystem which will finally influence its C uptakes. Climate warming has profoundly affected the terrestrial ecosystem and global biogeochemical cycle, as the average global surface temperature has increased almost 1 \({}^{\circ}\)C since preindustrial times [6]. Previous studies have shown that climate warming enhances photosynthesis, and thus promotes vegetation growth [7; 8]. Net primary productivity (NPP) is the difference of gross photosynthesis minus autotrophic respiration, which represents the function of ecosystem and is considered as a critical indicator for vegetation growth. Large-scale model simulations have shown that both global [9; 10; 11] and China mean NPP have increased significantly in recent decades [12; 13; 14; 15; 16]. The increase of NPP implies that vegetation takes up and stores more C in the ecosystem, which indicates more P consumption in the ecosystem. However, ecosystems begin their existence with a fixed complement of P from which even very small losses cannot readily be replenished [17]. Globally, N and P are the most common nutrients limiting plant growth and soil C storage [18]. Previous studies show that some tropical forests and savanna ecosystems are P limited because of their old soil age [19; 20]. [PERSON] et al. (2008) predicted that as humans continue to preferentially increase N deposition, ecosystems may shift from N limitation to P limitation [21]. Subtropical China is the region with the highest vegetation gross primary productivity (GPP), and its regional total GPP contributes the largest proportions in China's total GPP [22]. Previous experiments have shown that some of the subtropical forests in China are P limited, and some are both P and N limited [23; 24; 25; 26; 27].