Microclimatic Effects on Functional Traits of Arctostaphylos crustacea ssp. crustacea in Alameda County, California, USA

Anthropogenic climate change and land-use changes threaten the health and survival of plants, particularly by altering the microclimatic conditions of habitats. Plant productivity is highly sensitive to these abiotic conditions that influence their morphological and physiological traits. I studied this relationship in plants of the Arctostaphylos genus, commonly known as manzanita, shrubs in chaparral ecosystems across California. I assessed microclimate and examined its effects on leaf morphological traits and plant productivity of A . crustacea ssp. crustacea across two sites in Alameda County, California. At the site of higher sunlight and less soil moisture (VWC), leaves had a greater mass per area (LMA) and were more steeply angled, and photosynthesis was significantly higher (11.14 µmolCO ₂ /m ² s) than leaves at the site of less sunlight and more VWC (7.94 µmolCO ₂ /m ² s). Results from linear mixed models showed that light level was the overall strongest predictor variable for plant traits, with vapor pressure deficit and VWC also contributing to LMA, and leaf temperature and leaf angle distribution also influencing photosynthesis. Overall, no individual microclimatic variable was the sole contributing predictor of a leaf morphological trait or photosynthesis. Rather a combination and interaction of microclimatic conditions influenced plant functional traits, though some conditions had greater influence than others. The functional traits of A . crustacea ssp. crustacea adjusted in response to microclimatic factors, showing intraspecific trait variation (ITV) of this species. ITV is an essential defense for plant resilience that allows for adaptations in the face of rapidly changing climatic conditions.