Riparian forest dynamics in semi-arid river basins
Along semi-arid and Mediterranean-climate rivers, flood disturbance and drought are important drivers of riparian forest dynamics because they regulate habitat creation, tree mortality, and resource fluxes of water and nutrients critical for growth. I am working in riparian ecosystems in California and southern Europe to understand the drivers of riparian forest dynamics, and to assess their sustainability under changing land uses, climate and streamflow regimes.
Along the middle reach of the Sacramento River, CA, California's largest river, we are studying the community dynamics of forests dominated by Fremont cottonwood (Populus fremontii), a keystone riparian tree in river ecosystems of the U.S. southwest. We documented a little-known pathway for forest initiation in abandoned channels, and are using quantitative simulation models to predict corridor-wide forest response to likely scenarios of flow regulation and floodplain development. Along the Rhône River in SE France, we are documenting riparian forest structure, community dynamics, and accumulation of carbon pools on reaches impacted by 19th century navigation infrastructure and 20th century flow regulation. Together with collaborators in California and France, we are providing this research as guidance for river corridor planning and conservation under multiple management constraints.
In prior work, my lab conducted field studies and experiments on mechanisms of riparian seedling establishment along regulated rivers in California's Central Valley. A major stressor to riparian communities in semi-arid regions is the lack of tree recruitment on regulated rivers as a result of modifications to the flow regime. These studies include demography and competition, ecophysiology and isotope biogeochemistry, and environmental controls on life history timing of riparian trees. This research provides quantitative criteria for river managers to slow the decline of riparian forests along regulated rivers by optimizing natural recruitment with the highest degree of certainty and lowest water cost.
Related publications: (* indicates student contributors)
Thorel, M., H. Piégay, C. Barthélémy, B. Räpple*, C-R Gruel*, P. Marmonier, T. Winiarsky, J-P Bedell, F. Arnaud*, G. Roux, J.C. Stella, G. Seignemartin*, A. Tena-Pagan, V. Wawrzyniak*, D. Roux-Michollet, B. Oursel, S. Fayolle, C. Bertrand*, E. Franquet. (in press) Socio-environmental stakes associated with process-based restoration strategies in large rivers: should we remove novel ecosystems along the Rhône (France)? Regional Environmental Change
Räpple, B.*, H. Piégay, J.C. Stella, D. Mercier*. 2017. What drives riparian vegetation establishment in river channels at patch to corridor scales? Insights from annual airborne surveys (Drôme River, SE France). Ecohydrology DOI: 10.1002/eco.1886
Dufour, S., M.K. Hayden*, J.C. Stella, H. Piégay, J.J. Battles. 2014. Maintaining channel abandonment processes increases riparian plant diversity within fluvial corridors. Ecohydrology. DOI: 10.1002/eco.1546
Stella, J.C., M.K. Hayden*, J.J. Battles, H. Piégay, S. Dufour, and A.K. Fremier. 2011. The role of abandoned channels as refugia for sustaining pioneer riparian forest ecosystems. Ecosystems 14: 776-790. DOI 10.1007/s10021-011-9446-6 [pdf]
Harper, E.B., J.C. Stella, A.K. Fremier. 2011. Global sensitivity analysis for complex ecological models: a case study of riparian cottonwood population dynamics. Ecological Applications 21: 1225-1240. DOI:10.1890/10-0506.1[pdf]
Stella, J.C., J.D. Riddle*, J.J. Battles, M.K. Hayden*, and A.K. Fremier. 2012. Riparian forest dynamics on a large, regulated river (California, USA): impacts and implications for management. Proceedings of the Integrative Sciences and Sustainable Development of Rivers (IS Rivers) Conference, Lyon, France, 26–28 June 2012. [pdf]
Stella, J.C., and J.J. Battles. 2010. How do riparian woody seedlings survive seasonal drought? Oecologia 164:579–590. DOI 10.1007/s00442-010-1657-6 [pdf]
Stella, J.C., J.J. Battles, J.R. McBride, B.K. Orr. 2010. Riparian seedling mortality from simulated water table recession, and the design of sustainable flow regimes on regulated rivers. Restoration Ecology 18: 284-294. DOI: 10.1111/j.1526-100X.2010.00651.x [pdf]
Stella, J.C., J.J. Battles, B.K. Orr, J.R. McBride. 2006. Synchrony of seed dispersal, hydrology and local climate in a semi-arid river reach in California. Ecosystems 9:1200-1214. DOI: 10.1007/s10021-005-0138-y [pdf]