# Simulating Ecological Functions of Vegetation Using a Dynamic Vegetation Model
###### Abstract  
The ecological functions of vegetation play a significant role in improving human well-being. However, previous studies on ecological functions have only used semi-empirical models, which do not include physiological mechanisms and therefore do not accurately estimate the ecological functions of vegetation under scenarios of future climate change. To address this problem, a process-based dynamic vegetation model (LPJ-GUESS) was used to simulate the ecological functions of vegetation under different climate change scenarios in the Loess Plateau (LP), a typical ecologically fragile area in China. The simulated ecological functions were the carbon stock function (CS), soil conservation function (SC), and the water conservation function (WC). The results showed that: (1) Compared with 2001-2020, the proportion of area by shrub and grass vegetation that was predicted to transform into forest accounted for more than 1% of the area in the LP under the SSP119 scenario and 3% of the area in the LP under the SSP585 scenario during 2081-2100, respectively. (2) Compared with 2001-2020, the CS would decrease in the central and south-eastern regions, the SC would decrease in the western regions, and the WC would decrease in the Qilian, Wushaoling, Xinglong and Liupan Mountains during 2081-2100. (3) The relationships and the corresponding regions between the ecological functions of the vegetation and the corresponding regions in the LP would change significantly under climate change from 2001-2020 to 2081-2100.These results indicate that a process-based dynamic vegetation model can capture the changes in the carbon and water fluxes under changes in the climate and CO\({}_{2}\) concentration. It can also capture the vegetation succession, changes in ecological functions, and the transformation of functional relationships, which provide information that is conducive to the management and restoration of vegetation on the LP. This study supplies a novel perspective for vegetation management and high-quality development in other ecologically fragile regions worldwide. assessment highlighted that the average global surface temperature will increase by at least 1.5 \({}^{\circ}\)C in the next 20 years. The average precipitation will also increase according to the season, and it will vary by region. Climate change will continue to affect the carbon-water cycle and vegetation structure, which has a considerable impact on ecological functions and may also affect the transformation of the relationships between ecological functions [4]. Further research on dynamic changes in vegetation ecological functions under climate change at the global scale is an urgent priority, as is providing climate adaptation strategies for future vegetation management and the improvement of ecological functions. Studies on the ecological functions under climate change have been undertaken worldwide [5; 6; 7; 8]. However, these studies mainly predict future land use scenarios based on CA-Markov models and analyze spatial changes in ecosystem services combined with InVEST models. These studies have not clearly described dynamic changes in the vegetation and the interaction between climate, soil, CO\({}_{2}\) concentrations, and the vegetation [9]. Therefore, there is considerable uncertainty in predicting the carbon and water flux and the vegetation structure. This is because current research methods for examining ecological functions are limited. For example, the InVEST model is a semi-empirical model that is mainly used for the comprehensive evaluation of ecosystem services and trade-offs; however, it lacks a description of the mechanisms and processes of dynamic change in the vegetation ecosystem [10]. Therefore, it cannot effectively simulate vegetation succession, the carbon and water cycles, or the vegetation structure under climate change. The dynamic vegetation model can simulate the carbon and water flux, which can be used alongside its structure to estimate or calculate ecological functions.