Abstract:

To explore the stage-specific regulatory mechanisms of meteorological factors on forage yield in alpine steppe and to provide a scientific basis for grassland resource management and yield forecasting, we used fresh forage yield and concurrent meteorological records from the Batan alpine steppe, Tongde County of Qinghai Province during 2005-2023 to conduct study. Thirteen meteorological time-windows were delimited using the stage-grouping approach. Correlation analysis and multiple linear regression were employed to quantify the impacts of precipitation, mean air temperature, relative humidity, sunshine duration, and wind speed on forage yield and to characterize their stage-specific responses. Fresh forage yield exhibited a weak upward trend, with a climate-tendency rate of 1801.4 kg/hm² decade and a coefficient of variation of 59.3%, indicating high sensitivity to climatic fluctuations. Precipitation was the dominant promoting driver, exerting the strongest positive effect during the peak-growing window (May-August), with Pearson’s r=0.294 (P< 0.05). Relative humidity acted compensatory role in the late season by modulating vapor pressure deficit (VPD), as evidenced by r=0.462 (P<0.01) for May-August. Sunshine duration and wind speed exerted persistent suppressive effects across all stages. Temperature effects were stage-dependent: beneficial in spring but statistically non-significant during summer. The developed yield-forecasting model (adjusted R²=0.934, n=19, P<0.001) incorporated three pivotal variables: precipitation from December of the previous year to August of the current year, mean temperature from May to August, and relative humidity from November of the previous year to August of the current year. Forage yield formation in alpine steppe is water-dominated, with significant multi-factor temporal interactions, reflecting an ecological adaptation strategy of ‘water-heat coupling and stage complementarity’. We recommend developing stage-specific management protocols aligned with phenological phases and focusing on key meteorological variables within critical windows to improve forecasting accuracy.

Key words: alpine steppe, forage yield, meteorological factors, relative humidity, stage-grouping approach, yield forecasting, multiple linear regression, water-heat synergy