TY - JOUR
T1 - Enhanced root exudation of mature broadleaf and conifer trees in a Mediterranean forest during the dry season
AU - Jakoby, Gilad
AU - Rog, Ido
AU - Megidish, Shacham
AU - Klein, Tamir
N1 - The authors would like to thank: (Ahlström et al. 2015) Adi Iritz, an undergraduate student, for technical help in the lab; (Bates et al. 2014) Rotem Cahanovitc, an undergraduate student, for technical help in the field; (Belimov et al. 2009) Hilla Gil from the lab of Shimon Rachmilevitch, Ben Gurion University of the Negev, for sharing the field root exudate collection protocol and (Brzostek et al. 2013) Amer Madi for providing the airborne image in Figure S1 available as Supplementary Data at Tree Physiology Online. Funding - The project was funded in part by the Jewish National Fund (K.K.L.); the Merle S. Cahn Foundation and the Monroe and Marjorie Burk Fund for Alternative Energy Studies; Mr and Mrs Norman Reiser, together with the Weizmann Center for New Scientists; and the Edith and Nathan Goldberg Career Development Chair. Author contributions - Research was performed in situ by G.J. and led by T.K. I.R. and S.M. performed the soil and leaf measurements in situ. G.J. wrote the manuscript, guided by T.K.
PY - 2020/11
Y1 - 2020/11
N2 - Root exudates are part of the rhizodeposition process, which is the major source of soil organic carbon (C) released by plant roots. This flux of C is believed to have profound effects on C and nutrient cycling in ecosystems. The quantity of root exudates depends on the plant species, the period throughout the year, and external biotic and abiotic factors. Since root exudates of mature trees are difficult to collect in field conditions, very little is known about their flux, especially in water-limited ecosystems, such as the seasonally hot and dry Mediterranean maquis. Here, we collected exudates from DNA-identified roots in the forest from the gymnosperm Cupressus sempervirens L. and the evergreen angiosperm Pistacia lentiscus L. by 48-h incubations on a monthly temporal resolution throughout the year. We examined relationships of the root exudate C flux to abiotic parameters of the soil (water content, water potential, temperature) and atmosphere (vapor pressure deficit, temperature). We also studied relationships to C fluxes through the leaves as indicators of tree C balance. Root exudation rates varied significantly along the year, increasing from 6 μg C cm -2 root day-1 in both species in the wet season to 4- and 11-fold rates in Pistacia and Cupressus, respectively, in the dry season. A stepwise linear mixed-effects model showed that the three soil parameters were the most influential on exudation rates. Among biotic factors, there was a significant negative correlation of exudation rate with leaf assimilation in Cupressus and a significant negative correlation with leaf respiration in Pistacia. Our observation of enhanced exudation flux during the dry season indicates that exudation dynamics in the field are less sensitive to the low tree C availability in the dry season. The two key Mediterranean forest species seem to respond to seasonal changes in the rhizosphere such as drying and warming, and therefore invest C in the rhizosphere under seasonal drought.
AB - Root exudates are part of the rhizodeposition process, which is the major source of soil organic carbon (C) released by plant roots. This flux of C is believed to have profound effects on C and nutrient cycling in ecosystems. The quantity of root exudates depends on the plant species, the period throughout the year, and external biotic and abiotic factors. Since root exudates of mature trees are difficult to collect in field conditions, very little is known about their flux, especially in water-limited ecosystems, such as the seasonally hot and dry Mediterranean maquis. Here, we collected exudates from DNA-identified roots in the forest from the gymnosperm Cupressus sempervirens L. and the evergreen angiosperm Pistacia lentiscus L. by 48-h incubations on a monthly temporal resolution throughout the year. We examined relationships of the root exudate C flux to abiotic parameters of the soil (water content, water potential, temperature) and atmosphere (vapor pressure deficit, temperature). We also studied relationships to C fluxes through the leaves as indicators of tree C balance. Root exudation rates varied significantly along the year, increasing from 6 μg C cm -2 root day-1 in both species in the wet season to 4- and 11-fold rates in Pistacia and Cupressus, respectively, in the dry season. A stepwise linear mixed-effects model showed that the three soil parameters were the most influential on exudation rates. Among biotic factors, there was a significant negative correlation of exudation rate with leaf assimilation in Cupressus and a significant negative correlation with leaf respiration in Pistacia. Our observation of enhanced exudation flux during the dry season indicates that exudation dynamics in the field are less sensitive to the low tree C availability in the dry season. The two key Mediterranean forest species seem to respond to seasonal changes in the rhizosphere such as drying and warming, and therefore invest C in the rhizosphere under seasonal drought.
U2 - https://doi.org/10.1093/treephys/tpaa092
DO - https://doi.org/10.1093/treephys/tpaa092
M3 - مقالة
C2 - 32705136
SN - 0829-318X
VL - 40
SP - 1595
EP - 1605
JO - Tree Physiology
JF - Tree Physiology
IS - 11
ER -