Does root respiration in Australian rainforest tree seedlings acclimate to experimental warming?. (27th April 2020) - Noh, Nam Jin
Abstract: Plant respiration can acclimate to changing environmental conditions and vary between species as well as biome types, although belowground respiration responses to ongoing climate warming are not well understood. Understanding the thermal acclimation capacity of root respiration ( R root ) in relation to increasing temperatures is therefore critical in elucidating a key uncertainty in plant function in response to warming. However, the degree of temperature acclimation of R root in rainforest trees and how root chemical and morphological traits are related to acclimation is unknown. Here we investigated the extent to which respiration of fine roots (≤2 mm) of four tropical and four warm-temperate rainforest tree seedlings differed in response to warmer growth temperatures (control and +6 °C), including temperature sensitivity ( Q 10 ) and the degree of acclimation of R root . Regardless of biome type, we found no consistent pattern in the short-term temperature responses of R root to elevated growth temperature: a significant reduction in the temperature response of R root to +6 °C treatment was only observed for a tropical species, Cryptocarya mackinnoniana, whereas the other seven species had either some stimulation or no alteration. Across species, R root was positively correlated with root tissue nitrogen concentration (mg g −1 ), while Q 10 was positively correlated with root tissue density (g cm −3 ). Warming increased root tissue density by 20.8% but did not alter root nitrogen across species. We conclude that thermal acclimation capacity of R root to warming is species-specific and suggest that root tissue density is a useful predictor of R root and its thermal responses in rainforest tree seedlings.