Drought–rewatering events are becoming increasingly frequent on the Qinghai–Tibet Plateau, yet how drought severity shapes post-drought recovery of root functions and associated rhizosphere enzyme activities remains unclear. Here, Poa pratensis from Zeku Zequ National Wetland Park was subjected to a control treatment (75–80% field capacity, FC), mild (60–65% FC), moderate (40–50% FC), or severe drought (30–35% FC) for 14 days, followed by 14 days of rewatering. Root functional traits, leaf physiological responses, chlorophyll-related traits, and rhizosphere soil enzyme activities were evaluated. Drought severity progressively impaired root function, chlorophyll-related traits, and rhizosphere enzyme activities, whereas moderate drought induced the strongest osmotic adjustment and antioxidant enzyme responses. After rewatering, most traits under mild drought approached control levels, moderate drought showed partial restoration, and severe drought retained substantial deficits in root function, water status, chlorophyll-related traits, and rhizosphere enzyme activities. Pearson correlation analysis and PCA further revealed coordinated variation among root functions, physiological status, and rhizosphere enzyme activities. These findings demonstrate that drought severity strongly influences post-drought restoration trajectories of root functions and rhizosphere processes.

Unpredictable shifts between water deficit and excess water are increasingly relevant to forage systems, yet the extent to which prior water conditions shape later responses in alfalfa remains insufficiently resolved. We compared seven water-treatment sequences to assess plant growth, root and nodule performance, nitrogen acquisition, leaf physiology, photosynthesis, forage quality, and rhizosphere properties in alfalfa (Medicago sativa L.). Individual drought and waterlogging treatments impaired several growth and physiological traits, but the order of the two stresses produced distinct outcomes. Relative to continuously watered plants (C→C), waterlogging followed by drought (W→D) reduced total dry biomass, root activity, and nitrogen accumulation by 45.82%, 55.00%, and 54.38%, respectively. Drought followed by waterlogging (D→W), by contrast, caused the largest declines in nitrogenase activity and leghemoglobin content, by 66.27% and 52.92%, respectively. Recovery after stress removal was incomplete for several traits, indicating that the preceding water regime continued to influence plant performance. These results show that the sequence of water events is an important determinant of short-term root–nodule function, nitrogen status, and forage productivity under fluctuating water availability.

Alpine wetland ecosystems on the Qinghai–Tibet Plateau are highly vulnerable to hydrological alterations, yet whether alpine wetland plants occupying different hydrological niches exhibit distinct adaptive strategies under waterlogging remains poorly understood. Here, two dominant alpine wetland species, Kobresia tibetica and Blysmus sinocompressus, were exposed to four waterlogging treatments: control (CK), slight waterlogging (SW), moderate waterlogging (MSW), and severe waterlogging (SSW). Root functional traits, rhizosphere soil enzyme activities, physiological responses, and root transcriptomic profiles were analyzed to elucidate species-specific responses to waterlogging stress. Slight waterlogging promoted root growth, whereas moderate and severe waterlogging inhibited root development and impaired physiological functions in both species. Root transcriptomic analysis under moderate waterlogging identified 123 and 2806 differentially expressed genes in K. tibetica and B. sinocompressus, respectively. These genes were mainly associated with redox regulation and stress responses in K. tibetica, whereas carbon metabolism, energy metabolism, and stress-related pathways were enriched in B. sinocompressus. Overall, the two alpine wetland species exhibited contrasting species-specific waterlogging response strategies, with B. sinocompressus showing greater capacity to maintain belowground functional stability under moderate and severe waterlogging. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) validation further confirmed that waterlogging-responsive genes involved in anaerobic metabolism and antioxidant regulation showed species-specific expression patterns under severe waterlogging conditions.