ECOPHYSIOLOGICAL RESPONSES OF SUGAR MAPLE ROOTS TO CLIMATIC CONDITIONS

Abstract

We investigated the occurrence of and mechanisms responsible for acclimation of fineroot respiration of mature sugar maple (Acer saccharum Marsh.) after 3+ years of experimental soil warming. Experimental treatments included soil warming (+4-5 oC) in a factorial combination with soil moisture addition. Fine-root respiration was measured every two to four weeks during the growing season. Assessments of potential mechanisms for thermal acclimation included changes in enzyme capacity as indicated by root N; substrate limitation assessed by examining non-structural carbohydrates and effects of exogenous sugars; and responses to a respiratory decoupling agent (CCCP) to test for adenylate control. Partial acclimation of fine-root respiration occurred in response to soil warming throughout the study, causing specific root respiration to increase to a much lesser degree (14 to 27%) than would be expected for a 4 to 5 oC temperature increase. We found no evidence that enzyme or substrate limitation caused acclimation, but did find evidence supporting adenylate control. The uncoupling agent caused a 1.4 x greater stimulation of respiration in roots from warmed soil. Sugar maple fine-root respiration in warmed soil was at least partially constrained by adenylate use, likely limiting respiration to that needed to support work being performed by the root system. 1The material contained in this chapter was submitted to Plant, Cell and Environment and was returned for revisions. Mickey Jarvi designed the experiment, collected data, analyzed data, wrote manuscript, and edited manuscript. Andrew Burton is listed as a second author and assisted Mickey Jarvi with data analysis and interpretation and manuscript edits.