Effects of warming and precipitation on seed germination in soil seed bank of sagebrush desert grassland

We adopted a two-factor experimental design to explore the effect of hydrothermal interaction on seed germination in a soil seed bank. We measured the number and species of germinating plants and plant diversity in the 0－10 cm soil layer of a Seriphidium transiliense desert grassland by simulating temperature (control and temperature increase of 2, 4, and 6 ℃; T₀, T₂, T₄, and T₆, respectively) and water increase (control and water increase of 5%, 10%, 15%, and 20%; indicated by W₀, W₅, W₁₀, W₁₅, and W₂₀, respectively). The results showed that the total number and species of germinated seeds, as well as the plant diversity of the germinable soil seed bank, increased with increasing precipitation and increased and then decreased with increasing temperature, but the interaction was not significant. The maximum germination density was 350.3 grains·m⁻² in, T₂W₂₀ which was 119% times higher than that of T₀W₀; the minimum value was 95.5 grains·m⁻² in T₆W₀, which was 40% lower than that of T₀W_0. The total number of seeds germinated, germinated number of dicotyledonous plants, and germinated number of annual herbs in the germinating soil seed bank reached the highest value under the T₂W₂₀ treatment. The germination density in the 0－5 cm soil layers were 350.3, and 318.5 grains·m⁻², and the germination density in the 5－10 cm soil layers were 222.9, and 159.2 grains·m⁻². With increasing temperature and precipitation, the germination time and yellow period of soil germinable seed bank were advanced. Overall, the increase precipitation promoted the germination of seeds in the soil seed bank of Sagebrush desert grassland, whereas the increase in temperature inhibited the germination of seeds within the scope of the experimental design. Moderate increases in temperature and water (T ≤ T₄, W ≤ W₂₀) had no significant effect on soil seed germination, whereas an excessive increase in temperature without increase in water (T = T₆, W = W₀) was detrimental to the germination of the seeds in the soil bank seeds.