Use of stored carbon reserves in growth of temperate tree roots and leaf buds: analyses using radiocarbon measurements and modeling

Abstract

Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon ( 14 C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 y and about 55% of new root growth annually comes from stored C. Therefore, the resultant mean age of C used to grow new root tissue is ~0.4 y. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used.Consistent with these whole-ecosystem labeling results, the mean age of C in new-roottissues determined using "bomb-14 C" in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1-2 y. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies.However, models of root carbon dynamics should take stored reserves into account, particularly for pulse labeling studies and fast-cycling roots (< 1 y).2

Influence of climate and disturbance on the growth of Tsuga canadensis at its southern limit in eastern North America

“…Biological preconditioning is the initiation of internal metabolic conditions that influence the growth or biochemical reactions in trees during their life spans (Fritts 1971(Fritts , 1976. This is important as previous and current conditions influence the amount of carbon fixed and subsequently used for growth during the subsequent growing season (Kozlowski 1979;Kozlowski and Pallardy 1997;Gaudinski et al 2009). RFA was conducted using the T. canadensis STANDARD chronology and 30 monthly variables: 15 variables for mean monthly temperature and 15 variables for monthly total precipitation.…”

Responses of the structure and function of the understory plant communities to precipitation reduction across forest ecosystems in Germany

“…Note: In the leaf bulk material is a mixture of structural carbon as well as of storage compounds and freshly assimilated carbon (Adams and Grierson 2001;Werner et al 2012). Stored carbon is used for early leaf growth in plants (Gaudinski et al 2009;Muhr et al 2016). Thus, we did not analyzed the leaf samples for Δ 13 C in spring 2012.…”

“…Δ 13 C in the leaf organic matter is a signal integrating C i /C a over the leaf life time, and the leaf bulk material is a mixture of structural carbon as well as of storage compounds and freshly assimilated carbon (Adams and Grierson 2001;Werner et al 2012). Stored carbon is used for early leaf growth in plants with significant carbon storage capacities such as trees, shrubs and perennial herbs (Gaudinski et al 2009;Muhr et al 2016), which could explain the missing environmental signal in early summer also in the 2nd year, as it is assumed that remobilized storage reserves can be older than 1 year at least in woody species (Gessler and Treydte 2016). However, the response to reduced precipitation in total leaf organic matter should become visible later in the growing season, when new assimilates and their integration in fresh structural organic matter contribute significantly to the leaf carbon pool.…”

Effects of soil rewetting and thawing on soil gas fluxes: a review of current literature and suggestions for future research

“…An area of significant promise involves combining microbial community analyses Smith et al, 2010;Sawicka et al, 2009) and/or stable isotope techniques Goldberg and Gebauer, 2009;Gaudinski et al, 2009;Unger et al, 2012) with flux measurements. Whether performed in the lab or field, such experiments could improve our understanding of rewetting and thawing effect on soil gas fluxes, identifying source processes and mechanisms and quantifying their contributions to overall responses.…”