Height and Light-Obtaining Ability of <i>Leymus chinensis</i> Increased After a Decade of Warming in the Typical Steppe of Inner Mongolia, China

In the era of global climate change, existing evidence indicates that dominant species play a crucial role in regulating grassland structure and function. However, what remains overlooked are the factors that regulate the growth of dominant species under climate change. Some studies have indicated that the future climate of the Inner Mongolia grasslands will specifically show a trend of warming and humidification. Hence, in 2013, we conducted a controlled warming and precipitation addition experiment in a temperate steppe in Inner Mongolia, China. Open-top chambers (OTCs) were used to simulate warming (by 1.5 °C) and rainfall (twice a month, 10% of the average precipitation between 1960 and 2011 of the same month each time) during the growing season. In 2023, the resource utilization efficiency, morphological characteristics, leaf anatomical structure, and population quantity characteristics of the dominant species (<i>Leymus chinensis</i>), and community species diversity were monitored under control (CK), warming (T), precipitation addition (P), and warming plus precipitation addition (TP) conditions. We found that the plant height of <i>L. chinensis</i> significantly increased under warming; its height was 41.97 cm under TP, 41.84 cm under T, 29.48 cm under P, and 28.88 cm under CK. We observed that <i>L. chinensis</i> primarily obtains more light by increasing leaf area and height under warming conditions. Environmental changes also alter the tissue structure of <i>L. chinensis</i> leaves, leading to a decrease in lignification after increasing the water content. In this study, warming significantly increased the <i>L. chinensis</i> leaf area but decreased the leaf carbon content. Warming and precipitation addition regulated the height of <i>L. chinensis</i> by affecting the leaf area, leaf–stem ratio, and distance of the bottom leaf from the ground. Our results provide reasonable predictions regarding the succession direction of the <i>L. chinensis</i> steppe under global climate change in the future.