Fan Jingjing, Wang Zhengyu, Tu Chengyi, Lv Zhenglin, Liu Shuting, Fan Ying
College of Geography and Environment, Shandong Normal University, Jinan, China.
School of Economics and Management, Zhejiang Sci-Tech University, Hangzhou, China.
Physiol Plant. 2025 Jan-Feb;177(1):e70093. doi: 10.1111/ppl.70093.
Climate change has exacerbated precipitation variability, profoundly impacting vegetation dynamics and community structures in arid ecosystems. There remains a notable knowledge gap regarding the ecological effects of altered precipitation on crassulacean acid metabolism (CAM) plants and their interactions with other photosynthetic types. This study investigated the response of the typical obligate CAM plant Orostachys fimbriata to extended watering intervals (WI4-WI8) and various competitive patterns (M-M) with the C grass Melilotus officinalis and the C grass Setaria viridis through greenhouse experiments. The results showed that: (1) In species mixtures, CAM plants had slightly reduced the total biomass (TB) compared to monocultures, yet maintained competitiveness by increasing the root-to-shoot biomass (R:S) ratio, stabilizing plant height, and sustaining their photosynthetic rates. (2) As watering intervals increased, CAM plants adapted by further elevating the R:S ratio, reducing height, and decreasing aboveground biomass. However, their height, CO assimilation rate, and above- and below-ground biomass were significantly suppressed, particularly when coexisting with C plants. More extreme watering regime caused a 47.6% decrease in TB of CAM plants in M, while C and C grasses declined by 53.2% and 37.8%, respectively. (3) Given the predicted extension of drought intervals and the intensification of individual rainfall events under future climate conditions, the competitive pressure from C plants with high drought tolerance and resource acquisition advantages may limit the expansion potential of CAM plants in drylands. This study enhances the understanding of adaptive mechanisms of CAM plants competing and coexisting with grasses under variable environments, providing scientific bases for predicting arid ecosystem dynamics.
气候变化加剧了降水变率，对干旱生态系统中的植被动态和群落结构产生了深远影响。关于降水变化对景天酸代谢（CAM）植物的生态效应及其与其他光合类型植物相互作用的认识仍存在显著差距。本研究通过温室实验，调查了典型的专性CAM植物瓦松对延长浇水间隔（WI4 - WI8）以及与C4禾本科植物草木樨和C4禾本科植物狗尾草的各种竞争模式（M - M）的响应。结果表明：（1）在物种混合种植中，与单作相比，CAM植物的总生物量（TB）略有降低，但通过增加根冠比（R:S）、稳定株高和维持光合速率来保持竞争力。（2）随着浇水间隔的增加，CAM植物通过进一步提高R:S比、降低株高和减少地上生物量来适应。然而，它们的株高、CO₂同化率以及地上和地下生物量均受到显著抑制，尤其是与C4植物共存时。更极端的浇水制度导致在M模式下CAM植物的TB下降47.6%，而C3和C4禾本科植物分别下降53.2%和37.8%。（3）鉴于未来气候条件下干旱间隔的预测延长和单次降雨事件的加剧，具有高耐旱性和资源获取优势的C4植物的竞争压力可能会限制CAM植物在旱地的扩张潜力。本研究增进了对CAM植物在可变环境下与禾本科植物竞争和共存的适应机制的理解，为预测干旱生态系统动态提供了科学依据。
