Precipitation versus temperature as phenology controls in drylands

Area of Science:

• Ecology
• Plant Science
• Climate Change Research

Background:

• Plant phenology, the timing of plant life cycle events, is crucial for ecosystem function and global biogeochemical cycles.
• While temperature shifts are studied for temperate regions, precipitation changes are critical for dryland phenology.
• Drylands cover 40% of the Earth's land surface, making their phenological responses to climate change globally significant.

Purpose of the Study:

• To experimentally investigate the effects of altered precipitation on plant phenology in a semiarid grassland.
• To compare the phenological responses of grasses and deep-rooted woody shrubs to precipitation and temperature changes.
• To determine the primary climatic drivers of phenological shifts in dryland ecosystems.

Main Methods:

• Experimental manipulation of incoming precipitation over a decade in a semiarid grassland.
• Daily recording of plant phenology for seven years.
• Statistical analysis to determine relationships between precipitation, temperature, and phenological events (greenup, senescence).

Main Results:

• Precipitation strongly influenced grass greenup and senescence timing; temperature had a minor effect on greenup.
• Pre-season drought delayed grass greenup and shortened growing seasons.
• Drought led to earlier senescence, while increased precipitation delayed it, with extremely wet conditions causing a plateau.
• Woody shrubs exhibited consistent phenology, unaffected by precipitation or temperature variability.

Conclusions:

• Precipitation, particularly drought, is the dominant driver of phenological change in semiarid grasslands, unlike temperature-driven changes in temperate regions.
• Phenological shifts in drylands due to altered precipitation have significant implications for the global carbon, water, and energy balance.
• Grasses are more sensitive to precipitation variability than deep-rooted shrubs, suggesting potential shifts in ecosystem composition.