# Vegetation Health in China Is Severely Compromised by Drought, Wet and Heat Stress Events
###### Abstract
Different ecosystems exhibit significant variations in their responses to these climate stress events, with certain ecosystems, such as temperate grasslands and warm temperate deciduous broadleaf forests, showing higher sensitivity to these events [24]. Previous studies have primarily focused on the impacts of drought and heat stress on vegetation, while specific investigations into wet stress remain limited. Wet stress, as an important climatic stress, has been significantly underestimated in its effects on vegetation health. Moreover, prior research lacks a robust verification of optimal model selection. Additionally, the contributions of stress events to vegetation health have seldom been quantitatively assessed. This study incorporates wet stress alongside drought and heat stress to comprehensively explore the impacts of stress events on vegetation health and employs residual analysis to quantify the contributions of stress events to vegetation health. In general, these studies provide a comprehensive assessment of the impact of long-term climate change on vegetation growth, which is primarily based on one or several vegetation growth indicators to explore the effects of climate on vegetation growth. However, vegetation growth results from a complex interaction of internal and external environmental factors, and relying on a single vegetation index or related indicator remains insufficient for assessing whether vegetation is growing healthily. Therefore, a comprehensive health evaluation system is needed to more thoroughly investigate vegetation health. Additionally, different vegetation types exhibit varying levels of resistance and resilience to drought stress, wet stress, and heat stress events [25], making it crucial to urgently assess the impact of these stress events on vegetation health. China, located in East Asia and bordering the Pacific Ocean, boasts a rich diversity of vegetation types. The country has demonstrated strong leadership and commitment to global ecosystem stability by addressing climate change, reducing carbon emissions, and developing green energy. According to the \"14 th Five-Year Plan for Forestry and Grassland Protection and Development\", China aims to achieve a forest coverage rate of 24.1%, a forest stock volume of 19 billion cubic meters, and an overall grassland vegetation coverage of 57% by 2025 [26]. The interwoven distribution of various vegetation types plays a crucial role in maintaining the stability of China's ecosystems. However, existing studies on vegetation health primarily focus on small regional scales and evaluate the impact on ecosystem health using average temperature and precipitation with relatively simplistic models [27; 28]; simultaneously, research on the health of various types of vegetation across China still needs improvement. This study employs the Comprehensive Index Method (CIM), the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), and the Pressure-State-Response (PSR) model to construct three vegetation health assessment systems. We selected three vegetation indicators--Leaf Area Index (LAI), Net Primary Productivity (NPP), and Solar-Induced Chlorophyll Fluorescence (SIF)--to validate the effectiveness of these systems. A comprehensive assessment of vegetation health impacted by drought stress, wet stress, and heat stress from 2000 to 2020 was conducted to address the following questions: (1) What are the patterns of vegetation health changes from 2000 to 2020, and which assessment system most effectively represents vegetation health? (2) How does China's vegetation health respond to stress events? (3) What is the contribution of stress events to vegetation health, and which type of stress event will have a significant impact on future vegetation health predictions? This study provides insights into the response mechanisms of vegetation health to climate change in China, which may facilitate the formulation of rational management strategies and promote the sustainable development of vegetation ecosystems.