Shrub encroachment and degradation impact water balance by altering water fluxes in alpine meadows

Shrub encroachment and degradation in alpine meadow (AM) are global ecological problem that may profoundly impact water fluxes. However, the water flux dynamics after shrub encroachment and degradation are poorly understood. Here, changes in evaporation, transpiration, water infiltration, and water recharge for severe shrub-encroached meadow (SM) and severe degraded meadow (DM) on the Qinghai-Tibetan Plateau were explored through field experiments and stable water isotope methods. The results showed that the soil water evaporation ratios of the SM and DM were 21.4 % and 19.8 % lower than that of the AM, respectively. The average transpiration rates (TR) of the predominant plants in the SM and DM were 33.6 %-39.0 % and 11.8 %-14.7 % higher than that in the AM, respectively. However, the TR of L. virgaurea in DM was 3.7 g H₂O h⁻¹g⁻¹, which was lower than that of K. pygmaea (P < 0.05). Furthermore, the groundwater recharge and river recharge increased significantly in the SM (2.4 times and 1.4 times) and in the DM (2.4 times and 2.2 times) compared to that in the AM. Our findings highlight the influence of shrub encroachment and degradation on the water balance. The results provide a theoretical basis for water resource conservation and vegetation restoration in the AM ecosystem of the Qinghai-Tibetan Plateau.