Environmental controls of plant phenology in twelve desert plant species in the Patagonian Monte, Argentina

Abstract

The identification of the main abiotic variables influencing the seasonal development of plant phenology contributes to our knowledge of how arid and semi-arid ecosystems function. In this study, we addressed the following questions: 1. Is soil water content the most important variable determining plant phenophases? 2. Are phenophases across different life forms associated with the soil water content of different layers? We evaluated the relationships between environmental variables (i.e. precipitation, air temperature, soil moisture, and day length) and plant phenophases, using variable-length time periods preceding each measurement. We selected five representative evergreen shrubs, four deciduous shrubs, and three dominant perennial grasses. All phenophases related to vegetative and reproductive growth, and senescence were registered monthly during three years. The relationships between plant phenophases and environmental variables were evaluated using Spearman's correlation. We found that plant phenophases showed stronger association with soil water content and air temperature than precipitation. In most species, vegetative and reproductive phenophases were positively related to soil water content while leaf senescence was negatively associated. Soil water contents of layers 2 (10–20 cm) and 3 (20–40 cm) were more frequently related to plant phenophases than those of the first (0–10 cm) and fourth (40–100 cm) layers. Significantly correlated environmental variables encompassed previous periods of variable length depending on the species. Our results highlighted that soil water and air temperature were tightly correlated to plant phenophases and that all species seem to use the water contained in the same soil layers.