Grazing and watering alter plant phenological processes in a desert steppe community

Abstract

Phenology is well recognized as one of the most sensitive indicators of environmental change. Previous studies have focused on flowering phenology with few efforts given to the phenological successes and vegetative processes. Additionally, grazing is often characterized as a driver for community evolutionary processes, while precipitation is known as the most important abiotic cue in arid regions. Given this knowledge, we installed a nested experiment in a desert steppe to explore the coupled effects of grazing and watering on plant species’ reproductive successes and phenological timing in 2012–2013. We found that grazing increased the proportion of non-flowering individuals, with a greater proportion in 2013 than that in 2012. It decreased species richness and changed the habitat preferences in both years, and watering also reduced the richness in both years. Grazing also delayed the phenological timing for some dominant species and significantly delayed the green-up timing (5.67 days) and shortened the growing season length (GSL) in both 2012 (7.74 days) and 2013 (4.71 days). The application of watering, however, delayed some dominant species’ timing—including the browning timing of five dominate species ranging from 9.57 days in 2013 to 1.93 days in 2012—but it did not delay the species’ green-up timing. This resulted in a significantly prolonged growing season in 2013 (8.58 days). The high soil water and optimal soil temperature in the spring of 2013 contributed to an earlier green-up time (6.1 days) than in 2012.