Linkages between diurnal patterns of root respiration and leaf photosynthesis in Quercus crispula and Fagus crenata seedlings

Abstract

The physiological traits of tree roots have been considered associating with photosynthetic capacity; however, the linkages between diurnal patterns of root respiration and assimilation in individual leaves are poorly understood. Our objectives were to investigate the diurnal patterns of tree root respiration and the assimilation under natural luminous environments and to explore the potential environmental drivers of root respiration and the assimilation by relating trees' diurnal cycle to commonly measured variables. We simultaneously and continuously measured individual leaf assimilation and root respiration in 3-year-old seedlings of Quercus crispula and Fagus crenata, which are commonly the dominant tree species in deciduous broad-leaved forests in Japan, in full-sun and in the dark. Net assimilation rates followed a diurnal pattern in both species, with a marked decline in the morning that corresponded to a rapid increase in photosynthetic photon flux density, an increase in leaf temperature, and a vapor pressure deficit. Similarly, root respiration rates in both species decreased around noon in the sun treatment, although the soil temperature continued to increase. Seedlings in the sun treatment had significantly higher rates of root respiration than seedlings that were kept in the dark. Our results suggest that the midday depression of leaf assimilation could lead to downward transport of photosynthetic products, causing a midday depression in root respiration on a diurnal time scale. Furthermore, the effects of changes in the assimilated carbon supply on root respiration are likely to vary with light conditions experienced by leaves.

Seasonal and diurnal patterns of soil respiration in an evergreen coniferous forest: Evidence from six years of observation with automatic chambers

“…In September and October, R s relative to the soil temperature was higher in the morning than at night. Diurnal hysteresis in the relationship between R s and soil temperature is an example of multiple processes interacting to produce highly variable photosynthetic attributes [ 30 , 31 ]. Liu et al [ 17 ] showed that the diurnal cycle of R s in a mixed deciduous forest was related more to differences in photosynthetically active radiation than to variations in soil environmental conditions, suggesting that diurnal R s patterns were associated with photosynthesis.…”

“…Photoinhibitory damage and stomatal closure contribute significantly to midday photosynthetic depression and, indirectly, to the decline in C supply to the root system. Makita et al [ 31 ] showed that weather conditions under high temperature stress cause a midday depression of CO 2 assimilation in deciduous trees and then a sharp reduction in autotrophic respiration rate. The flux of new photosynthate to the rhizosphere significantly accelerates microbial activity there.…”

“…Another advantage of the automated system is that it can evaluate diurnal scales. Recent studies using measurements with high temporal resolution have shown that R s can vary during the day at a given soil temperature, causing a diurnal hysteresis in the temperature–respiration relationship [ 29 – 31 ]. Phase lags between the diurnal signals of soil temperature and R s have been reported [ 28 , 32 ], resulting from processes such as photosynthate supply, heat transport, and CO 2 diffusion [ 33 , 34 ].…”

Does soil respiration decline following bark beetle induced forest mortality? Evidence from a lodgepole pine forest

“…Respiratory processes of plant roots and mycorrhizal microorganisms, roughly half of the total soil respiration (Högberg et al, 2009), are highly dependent on recent photosynthates (Högberg et al, 2001). These activities are characterized by large seasonal fluctuations typically due to temperature, moisture and light shifts (Davidson et al, 1998;Luo and Zhou, 2006;Makita et al, 2014). Respiration by plant roots and mycorrhizal symbionts is considered to be more sensitive to changes in temperature, compared to respiration by soil without roots (Boone et al, 1998).…”

Phenology of fine roots and shoots using high frequency temporal resolution images in a temperate larch forest

“…Photoinhibitory damage and stomatal closure contribute signi cantly to photosynthetic depression and indirectly to the decline in C supply to the root system. Makita et al (2014) showed that weather conditions under high temperature stress cause a depression in CO 2 assimilation in deciduous trees and then a sharp reduction in root respiration rate. Indeed, it seems that the PAI and GR ratio in our study slightly decreased from August (Fig.…”