Synchronicity of fine root and soil fungal phenology: Response to disturbance, interannual variation in precipitation and temperature, and atmospheric [CO₂] over 12 years

Principal investigator: Seth Pritchard, College of Charleston

Co-investigator: Allan Strand, College of Charleston

Abstract

Objectives: 1) To explore the interactions among climatic variability (interannual and monthly) and disturbance (drought, ice storm, and hurricane) and fine roots/soil fungal processes over a 12 year period; 2) To link temporal patterns of allocation to fine roots and associated fungal structures with soil CO₂ efflux, leaf area dynamics, and stem growth; and 3) Determine if interannual variation in mean or extreme climates will cause differential shifts in phenology of roots compared to soil fungi resulting in temporal asynchrony between fine root and soil fungal dynamics.

Hypotheses: 1) Seasonal fine root phenology will be linked to canopy temperatures while soil fungal phenology will be more closely linked to soil moisture availability. Temperature extremes will uncouple phenology of fine root and soil fungi; 2) Because the temperature optimum for photosynthesis is higher with CO₂-enrichment, warm years will lead to a greater fine root production in CO₂-enriched plots than ambient plots; 3) Climatic extremes will result in asynchrony between roots and leaves; consequently, fine root and mycorrhizal standing crop will shift out of phase with rhizomorphs (many of which are saprotrophic).

Location of research activities: Charleston, SC and Durham, NC.

Methods: For over a decade, images of roots and associated fungal structures were recorded at monthly sampling intervals (>200,000 images taken over 106 sessions) using micro-video cameras at the Duke University FACE site, the longest continuous running forest-scale CO₂-enrichment experiment in the world. We propose to use statistical techniques including time-series analysis to extract the changes in frequency and magnitude of fine root and fungal activity occurring over a 12 year period and to relate those to climatic variability over the same period. We also propose to determine how interannual and monthly variation in temperature and precipitation, soil N fertility, and atmospheric CO₂ concentration influence the synchrony between above- with belowground processes and between roots and soil fungi.

Expected deliverables: Integration of multiple long-term data-sets with a long term record of fine root processes, analyzed in the context of interannual variability in climate, will provide important information on controls of soil C flux. This information will be useful for predicting the influence of climate change and variability on ecosystem dynamics and will result in three refereed publications.