B031-0012
Linking tree life history characteristics and population dynamics to plant hydraulics

Wednesday, 9 December 2020
Poster
Junyan Ding, Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, United States, Ryan G Knox, MIT, Cambridge, MA, United States, Roger C Bales, University of California Merced, Merced, CA, United States, Polly Buotte, University of California, Berkeley, Energy and Resources Group, Berkeley, CA, United States, Bradley Christoffersen, University of Texas Rio Grande Valley, Edinburg, United States, Rosie Fisher, National Center for Atmospheric Research, Boulder, CO, United States, Michael Goulden, Univesity of California, Irvine, Department of Earth System Science, Irvine, CA, United States, Edward A Johnson, Univ Calgary, Biological Sciences, Calgary, AB, Canada, Lara M Kueppers, University of California Berkeley, Energy and Resources Group, Berkeley, CA, United States, Jacquelyn K Shuman, University of Virginia, Charlottesville, VA, United States, Chonggang Xu, Los Alamos National Laboratory, Los Alamos, NM, United States and Charlie Koven, Earth Sciences Division, Lawrence Berkeley National Laboratory,, Berkeley, CA, United States
Abstract:
Changes to forest structure and productivity occur as the result of population dynamics of plants that differ in life history traits. Plant hydraulics plays a critical role in regulating the response of forests to environmental conditions.

Here we use a demographic vegetation model, the Functionally Assembled Terrestrial Ecosystem Simulator with integrated plant hydraulics (FATES-Hydro), to explore the effects of hydraulic strategy on the life history and population dynamics of a conifer forest at a mid-elevation conifer forest of the Soaproots catchment of Southern Sierras in California, USA. We use pine and cedar as model plant functional types (PFTs), as they are the most common genera and have distinct strategies for responding to environmental variations. Pine have deep root systems, efficient/unsafe xylem, high leaf nitrogen(N) content, and are found to occupy the canopy, whereas cedar have shallow, wide root systems, inefficient/safe xylem, low leaf N, and are often found in the understory. We run the FATES-Hydro with pine and cedar on their own, and the 2 PFTs in competition. Simulations are initialized from bare ground to represent the secondary succession from a local seed bank, and run for 1000 years cycling through the MACA meteorological data of the 1979-2012 period. The results of single PFT simulations show that the efficient hydraulic traits lead to faster growth but higher mortality for pine cohorts resulting in shorter tree lifespan and more fluctuating population and ecosystem productivity (GEP), while inefficient hydraulic traits lead to slower growth but lower mortality for cedar cohorts, resulting in longer tree life span and a more stable population and GEP. With competition, pine dominates at first, as a result of greater capacity for resource competition, representing an early successional stage; over time cedar becomes dominant due to its longer lifespan, thus representing a later successional stage. These findings suggest a relationship between plant hydraulic strategy (e.g. safety-efficiency trade off of xylem) and disturbance regime (e.g fire frequency and intensity). Understanding the connection between plant hydraulics and life history traits, and their links to population dynamics is critical to predicting vegetation dynamics under changing climate and disturbance regimes.

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