The highly biodiverse shrublands of Doñana National Park experienced a severe drought in 2004/2005. We want to understand the demographic consequences of this event and how species demography can predict resilience to drought.
I have joined Prof. Paco Lloret from CREAF to begin a (hopefully) long-term demographic monitoring of shrubs in Doñana National Park in southwest Spain.
Our study area is characterized by a Mediterranean-type climate and is extremely vulnerable to predicted increases in temperature and rainfall scarcity. Vegetation in the study area is dominated by extensive shrublands, which experienced an extreme drought in the 2004–2005 hydrological year. The drought caused a die-off of green tissue on the dominant shrub vegetation that reached 75% of the plant cover in some stands and changed species composition and the functioning of plant-soil interactions.
Paco has been monitoring the shrub community ever since the drought event, but has thus far largely focused on measuring abundance and species composition in different plots. I was a research fellow in his group 2019/2020 and convinced him to look at the underlying demographic mechanisms of community responses to extreme weather.
To understand how demographic responses of individual species mediate community-wide responses to climate, we have set up an individual demographic monitoring scheme for two shrubs with contrasting life histories: the dominant, long-lived Halimium halimifolium and the shorter-lived, highly reproductive Lavandula stoechas. Data obtained from monitoring these two shrubs will also feed some gaps in determining demographic rates from changes in abundances for some of the other shrubs in the community.
So far, we have two years of data on >1,000 individuals (all collected with the invaluable help of students and postdocs).
We are interested in the following questions:
Is community resilience more sensitive to direct or indirect (via species interactions) effects of climate on species demography?
Do we see legacy effects of the 2005 drought on current population dynamics? (Preliminary results show that there are quite a few such effects indeed)
Do we need a mechanistic understanding of species interactions to understand community resilience or are simple, static measures of the relative prevalence of demographic traits enough?