My side projects fall in three main categories: comparative demography, mycorrhizal research, and effects of herbivores on growth rates. - Comparative demography: Much of ecology concerns the relationship between organisms and their environments. Although most ecologists carry out specific experiments with a limited set of study systems, our ultimate goal is to discover universal rules by compiling and comparing studies in different contexts. Indeed, the discovery of the most general ecological rules (e.g. exponential growth potential and regulated population growth, principle of competitive exclusion, robust coexistence, life-history trade-offs, etc) arose through the extensive application of standardized, comparative methodologies. Through the acquisition of a one-of-a-kind database (n>430 plant species) that contains ecological, taxonomic and demographic (in the form of projection matrices) information, I am studying the extent to which biotic and abiotic factors shape ecological strategies for adaptation in plants. The first step towards comparing demographic data in the format of projection matrices is to make sure that the matrices themselves are comparable. To that end, I have collaborated with Prof Joshua B Plotkin to establish the optimum criterion to collapse matrix dimensions to the same dimensionality that minimizes the effects on the associated eigendata of the matrix. Other projects of recent initiation involve a review on the current understanding and future directions for plant demographics through the application of matrix models in collaboration with Prof Miguel Franco and Dr Eelke Jongejans. Future projects will involve (i) the decomposition of demographic dynamics through the application of network analyses, broken down to its basic vital rates, in order to study the effects different long-term ecological strategies of individuals have on the population growth rate, and (ii) the effects of phylogenetic inertia, habitat and growth form on woody plant demographic dynamics. - Mycorrhizae: The Casper lab has extensive experience with mycorrhizal research and desert ecology. In this project we are bridging the gap between both fields, and we are identifying the mycorrhizal community associated to my doctoral research study species, the aridland herbaceous Cryptantha flava L. (Boraginaceae). We have evidence that mycorrhizal hyphae grow in the ephemeral roots of C. flava, and that arbuscular structures develop in the nodes of the lateral roots of C. flava. We are now working on the identification and description of the mycorrhizal community that live in these roots. Questions yet to be addressed are: (i) when an individual lateral root is activate for resource uptake, does its associated microbial community activate synchronically?, (ii) where do the mycorrhizae overwinter (in the soil, in nodes of the lateral roots, in the dead fine ephemeral roots)?, (iii) to what extent/when do these microbes affect the demographic performance of C. flava?...
- Herbivory: White-tailed deer (Odocoileus virginianus) populations are extremely abundant throughout much of eastern US. Dentrimental effects due to white-tailed deer have been extensively documented, especially in regards to the herbaceous component of the native flora. Nonetheless, we still lack a basic understanding on how deer may affect - through complex, indirect feedbacks - the ecology of trees. We hypothesize that through the grazing of herbaceous species, deer effectively liberate trees from belowground competition, allowing them to grow faster. This project is the spin off of an upper level course (Conservation biology techniques in the field) in which I served as a teaching assistant. In it, we are currently reconstructing the demographic dynamics of red oak (Quercus rubra) populations in four sites with deer and their respective deer exclosures, in Shenandoah N.P. We are integrating bioitic and abiotic information of the environment inside and outside the deer exclosures to help explain remarkable differences found in the tree ring growth increments. Collaborators: Dr Richard Lucas, Prof William McShea, Prof Brenda Casper and some BIO465 students.
|
