Estimating fine root longevity in a temperate Norway spruce forest using three independent methods (original) (raw)
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Variation of carbon age of fine roots in boreal forests determined from 14C measurements
Plant and Soil, 2013
The main objectives of this study were to determine how the carbon age of fine root cellulose varies between stands, tree species, root diameter and soil depth. In addition, we also compared the carbon age of fine roots from soil cores of this study with reported values from the roots of the same diameter classes of ingrowth cores on the same sites. Methods We used natural abundance of 14 C to estimate root carbon age in four boreal Norway spruce and Scots pine stands in Finland and Estonia. Results Age of fine root carbon was older in 1.5-2 mm diameter fine roots than in fine roots with <0.5 mm diameter, and tended to be older in mineral soil than in organic soil. Fine root carbon was older in the less fertile Finnish spruce stands (11-12 years) than in the more fertile Estonian stand (3 and 8 years), implying that roots may live longer in less fertile soil. We further observed that on one of our sites carbon in live fine roots with the 1.5-2 mm diameter was of similar C age (7-12 years) than in the ingrowth core roots despite the reported root age in the ingrowth coresbeing not older than 2 years. Conclusions From this result, we conclude that new live roots may in some cases use old carbon reserves for their cellulose formation. Future research should be oriented towards improving our understanding of possible internal redistribution and uptake of C in trees.
Does the age of fine root carbon indicate the age of fine roots in boreal forests?
Biogeochemistry, 2010
To test the reliability of the radiocarbon method for determining root age, we analyzed fine roots (originating from the years 1985-1993) from ingrowth cores with known maximum root age (1-6 years old). For this purpose, three Scots pine (Pinus sylvestris L.) stands were selected from boreal forests in Finland. We analyzed root 14 C age by the radiocarbon method and compared it with the abovementioned known maximum fine root age. In general, ages determined by the two methods (root 14 C age and ingrowth core root maximum age) were in agreement with each other for roots of small diameter (\0.5 mm). By contrast, in most of the samples of fine roots of larger diameter (1.5-2 mm), the 14 C age of root samples of 1987-1989 exceeded the ingrowth core root maximum age by 1-10 years. This shows that these roots had received a large amount of older stored carbon from unknown sources in addition to atmospheric CO 2 directly from photosynthesis. We conclude that the 14 C signature of fine roots, especially those of larger diameter, may not always be indicative of root age, and that further studies are needed concerning the extent of possible root uptake of older carbon and its residence time in roots. Keywords Fine root age Á Pinus sylvestris Á Radiocarbon Á Root carbon Á Ingrowth cores Á Tree ring
Old carbon in young fine roots in boreal forests
Biogeochemistry, 2015
A large proportion of the soil carbon (C) in boreal forests originates from roots and ectomycorrhizal fungi, and accurate quantification of fine-root litter production is needed. Methods for determination of root turnover have been under debate in recent years. Two recently used methods-radiocarbon (14 C) dating and use of minirhizotrons (MR)-have yielded different results. This has been attributed to analysis of different roots by use of these methods. At Flakaliden, northern Sweden, in a long-term soil warming and irrigation experiment, we compared MR lifespan with the 14 C-derived age of fine roots from soil cores of the same root diameter class. We also determined the 14 C-derived age of ingrowth core roots of Norway spruce. The median lifespan of fine roots around MR tubes installed 15 years previously was shorter than 2.5 years whereas the 14 C-derived age of the fine roots from soil cores varied from recently grown to 14 years. Correspondingly, the age of 14 C in fine roots harvested from ingrowth cores installed in soil 3 months previously was between 1 and 20 years. Thus, cellulose in these roots contained older 14 C than is possible from photosynthesis during the time of cellulose formation. By investigating whether the age of Norway spruce and Scots pine seedlings was less than their root 14 C-derived age, we tested the possibility of root C originating from soil uptake. This was found to be unlikely, because fine roots of four and eight-year-old seedlings had 14 C that was dated to be as old as or younger than the seedlings. We propose that further effort is required to identify the ecological conditions leading to root growth utilization of stored or recycled C.
Tree physiology, 2008
We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a depth of 60 cm. Fine root morphological characteristics, such as specific root length (SRL), root length density (RLD), root surface area (RSA), root tip number and branching frequency (per unit root length or mass), were determined based on digitized root data. Fine root biomass and morphological characteristics related to biomass (RLD and RSA) followed the same tendency with chronosequence and were significantly higher in the 30-year-old stand and lower in the 10-year-old stand than in the other stands. Among stands, mean fine root (< 2 mm) biomass ranged from 49 to 398 g m(-2), SLR from 13.4 to 19.8 m g(-1), RLD from 980 to 11,65...
Unravelling the age of fine roots of temperate and boreal forests
Nature Communications
Fine roots support the water and nutrient demands of plants and supply carbon to soils. Quantifying turnover times of fine roots is crucial for modeling soil organic matter dynamics and constraining carbon cycle-climate feedbacks. Here we challenge widely used isotopebased estimates suggesting the turnover of fine roots of trees to be as slow as a decade. By recording annual growth rings of roots from woody plant species, we show that mean chronological ages of fine roots vary from <1 to 12 years in temperate, boreal and sub-arctic forests. Radiocarbon dating reveals the same roots to be constructed from 10 ± 1 year (mean ± 1 SE) older carbon. This dramatic difference provides evidence for a time lag between plant carbon assimilation and production of fine roots, most likely due to internal carbon storage. The high root turnover documented here implies greater carbon inputs into soils than previously thought which has wide-ranging implications for quantifying ecosystem carbon allocation.
Forest Ecology and Management, 2005
Fine root bio-and necromass, net primary production (NPP) of fine roots and its proportion of the NPP of trees, as well as turnover rate were investigated in a fertile middle-aged Norway spruce (Picea abies (L.) Karst) stand by sequential core and ingrowth core methods. The stand's site type is Oxalis, the site quality class is I a and the soil type is Umbric Luvisol (FAO classification). Twenty soil cores (volumetric samples, core diameter 38 mm) were taken monthly during the period June-1996 to November 1996 and in June-1997. Ingrowth cores were collected, 15 at a time, during the growing seasons from 1997 to 1999, once after first year and three times in the second and third years. Spruce roots from samples collected by both methods were separated into living and dead roots (two diameter classes: <1 and 1 mm d <2 mm). The fine root NPP was calculated according to the decision matrix, and root turnover rate was calculated as annual root production divided by mean fine root biomass.
The age of fine-root carbon in three forests of the eastern United States measured by radiocarbon
2001
Using a new approach involving one-time measurements of radiocarbon (14 C) in fine (< 2 mm diameter) root tissues we have directly measured the mean age of fine-root carbon. We find that the carbon making up the standing stock of fine roots in deciduous and coniferous forests of the eastern United States has a mean age of 3-18 years for live fine roots, 10-18 years for dead fine roots, and 3-18 years for mixed live+ dead fine roots.
Dendrochronologia, 2016
Missing and wedging rings are common features of tree growth. They occur more frequently in roots than in stems and were reported for various species and sites. These rather frequent irregularities in roots make dendrochronological analysis and cross-dating of roots more challenging. The goal of this study was to present a compiled method for a quantitative analysis of ring-growth irregularities. The analysis was conducted on ten spruce (Picea abies L. Karst) roots taken from the Gorce Mountains (Southern Poland). A four-step cross-dating of these root samples was applied. Three to six cross-sections were analysed within each root and cross-dated with a corresponding stem and site chronology. All ringgrowth analyses were conducted on micro sections. Finally, the dating method was evaluated using three control indicators. The study revealed that wedging rings occurring in both, cross-sectional and longitudinal profiles were observed in 17.3% of the rings analysed. The application of a combined zigzag segment tracing and serial sectioning allowed to significantly reduce, compared to previous methods, the amount of undetected missing rings and revealed them as cross-sectional or longitudinal wedging rings. Thanks to the application of control indicators the irregularities occurring in rings of roots were quantified and compared with different environmental factors such as droughts, air pollution, insect outbreaks and geomorphological processes. Significant positive correlation between root age and the number of radial growth irregularities in roots was demonstrated. A detailed investigation of multiple cross-sections per root enabled to trace all types of ring irregularities in the roots and substantially reduced cross-dating subjectivity.