Linking Plant Physiology and Demography
The Casper lab has done extensive research connecting physiological and demographic approaches to understand survival and reproductive strategies under harsh conditions. Our field research is primarily carried out at the Great Basin Desert, specifically in Utah. There, we have been following the demographic dynamics of the chamaephyte Cryptantha flava (Boraginaceae) since 1997. This long-term dataset places our lab in a privileged position where we can now address questions related to climate change. Recently, our work has examined the effects of droughts early on in the growing season, as predicted by regional climatic models. Current research, on the other hand, is exploring the effects of precipitation shifts towards the end of the growing season, which has been reported to effectively lengthen the temporal window during which C. flava carries out vital functions (Salguero-Gomez & Casper, in prep).
One of the main questions that we are currently exploring is what factors determine optimum size in individual plants and through which mechanisms. Much is known about the anatomic, physiological and demographic requirements for plant growth, but our understanding of decreases in plant size, i.e. shrinkage, is virtually nonexistent. We are exploring whether plants can actively limit growth to satisfy basic vital rates such as survival during extremely dry years, and whether there are some costs associated to individual plant shrinkage, or if plant shrinkage represents a side-product of physiological/demographic senescence. Our approach is multidisciplinary, and it incorporates anatomical studies of the hydraulic design of juveniles and adults, physiological techniques (leaf water potentials, isotope discrimination, dye-tracking…), within-individual demography, field-based studies and comparative demography through the utilization of projection matrix models.