Comparison and Optimization of Light Use Efficiency-Based Gross Primary Productivity Models in an Agroforestry Orchard  
[PERSON]  
1 State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (Z.H. ); [EMAIL_ADDRESS] (M.W. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (Q.L.) [PERSON]  
1 State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (Z.H. ); [EMAIL_ADDRESS] (M.W. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (Q.L.) [PERSON]  
1 State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (Z.H. ); [EMAIL_ADDRESS] (M.W. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (Q.L.) [PERSON]  
1 State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (Z.H. ); [EMAIL_ADDRESS] (M.W. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (Q.L.) [PERSON]  
1 State Key Laboratory of Hydraulics and Mountain River Engineering & College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China; [EMAIL_ADDRESS] (N.C.); [EMAIL_ADDRESS] (Z.H. ); [EMAIL_ADDRESS] (M.W. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (L.Z. ); [EMAIL_ADDRESS] (Q.L.) [PERSON]  
2 State Engineering Laboratory of Efficient Water Use of Crops and Disaster Loss Mitigation, Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agriculture Science, Beijing 100081, China; [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS] (These authors contributed equally to this work. 2024 16 3679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 17 186193679 186193679 1861936  
systems is key for evaluating carbon sequestration capacity and is, thus, crucial for crop production prediction and ecosystem carbon management [3; 4]. The eddy covariance (EC) flux system can measure the near-surface net ecosystem CO\({}_{2}\) exchange continuously at high frequency, estimating _GPP_ by partitioning _NEE_ and ecosystem respiration (\(R_{\rm e}\)) [5; 6]. Some _GPP_ data have been shared in global or regional flux networks. However, the EC flux system is still limited in space and time owing to its high price and the difficulty to obtain access from some private managers. The light-use efficiency-based GPP (LUE-GPP) model defines _GPP_ as the product of photosynthetically-active radiation absorbed by vegetation canopy and photosynthetic utilization efficiency. In combination with available meteorological or biological variables or satellite remote sensing data, the LUE-GPP model is widely used for calculating regional or global _GPP_[7; 8]. Some models regard the photosynthetic parameters of the underlying surface as a whole; thus, they are known as big-leaf LUE-GPP (BL) models [9; 10] and include the EC-light use efficiency (EF-LUE) model [11], moderate resolution imaging spectroradiometer (MODIS) GPP algorithm [12], vegetation photosynthesis model (VPM) [13; 14], and Carnegie-Ames-Stanford Approach (CASA) model [15]. However, the evaluation of the ecosystem _GPP_ still has great uncertainty [3; 4; 16; 17]. [PERSON] et al. [15] showed that the _LUE_ values calculated by the CASA model were significantly different across 12 farmland EC sites, and the larger difference in photosynthetic capacity between C3 and C4 species highlights the necessity of model parameterizations (i.e., maximal light use efficiency) [17]. In addition, the seasonal variation of _LUE_ enhances the difficulty in cropland productivity estimates [3; 4].