Fine‐root mortality rates in a temperate forest: estimates using radiocarbon data and numerical modeling

Riley, William J.; Gaudinski, J. B.; Torn, M. S.; Joslin, J. D.; Hanson, Paul J.

doi:10.1111/j.1469-8137.2009.02980.x

Cited by 48 publications

(53 citation statements)

References 51 publications

(87 reference statements)

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“…This can lead to a mean age of C of 0.4 yr at the point of integration [41]. Several recent studies detected discrepancies in mean fine root age and postulated two pools of fine roots: one, a fast but smaller turnover pool with a mean turnover time of <1 yr, the other, larger, with a decadal turnover time [42], [43]. In many studies, fine root thickness is or was arbitrary [44].…”

Section: Introductionmentioning

confidence: 99%

Nine Years of Irrigation Cause Vegetation and Fine Root Shifts in a Water-Limited Pine Forest

et al. 2014

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Scots pines (Pinus sylvestris L.) in the inner-Alpine dry valleys of Switzerland have suffered from increased mortality during the past decades, which has been caused by longer and more frequent dry periods. In addition, a proceeding replacement of Scots pines by pubescent oaks (Quercus pubescens Willd.) has been observed. In 2003, an irrigation experiment was performed to track changes by reducing drought pressure on the natural pine forest. After nine years of irrigation, we observed major adaptations in the vegetation and shifts in Scots pine fine root abundance and structure. Irrigation permitted new plant species to assemble and promote canopy closure with a subsequent loss of herb and moss coverage. Fine root dry weight increased under irrigation and fine roots had a tendency to elongate. Structural composition of fine roots remained unaffected by irrigation, expressing preserved proportions of cellulose, lignin and phenolic substances. A shift to a more negative δ13C signal in the fine root C indicates an increased photosynthetic activity in irrigated pine trees. Using radiocarbon (14C) measurement, a reduced mean age of the fine roots in irrigated plots was revealed. The reason for this is either an increase in newly produced fine roots, supported by the increase in fine root biomass, or a reduced lifespan of fine roots which corresponds to an enhanced turnover rate. Overall, the responses belowground to irrigation are less conspicuous than the more rapid adaptations aboveground. Lagged and conservative adaptations of tree roots with decadal lifespans are challenging to detect, hence demanding for long-term surveys. Investigations concerning fine root turnover rate and degradation processes under a changing climate are crucial for a complete understanding of C cycling.

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Section: Introductionmentioning

confidence: 99%

Nine Years of Irrigation Cause Vegetation and Fine Root Shifts in a Water-Limited Pine Forest

et al. 2014

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“…Wells and Eissenstat (2001) reported that root survivorship may vary markedly between fine roots differing in diameter by only a few tenths of a millimeter. Furthermore, Riley et al (2009), through their 14 C labeled temperate forest study, predicted live root turnover times \1 year for the short-lived root pools (\0.5 mm in diameter) and 10 years for the long-lived root pools (0.5-2 mm in diameter). It is also rational that high-order roots (i.e.…”

Section: Discussionmentioning

confidence: 99%

Does the age of fine root carbon indicate the age of fine roots in boreal forests?

Sah¹,

Jungner

Oinonen

et al. 2010

Biogeochemistry

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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.

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“…CLM4 calculates root distributions for plant water uptake based on a double-exponential function (Zeng, 2001); in principle, however, the vertical profiles of root C and N inputs to soil need not be identical to those of plant water uptake from soil due to differing root lifetimes (Joslin et al, 2006;Riley et al, 2009) for different types of roots. Thus, one hypothesis is that C inputs are proportional to the root profiles used in the water uptake calculations.…”

Section: Vertical Discretization Of Carbon Inputsmentioning

confidence: 99%

The effect of vertically resolved soil biogeochemistry and alternate soil C and N models on C dynamics of CLM4

et al. 2013

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Abstract. Soils are a crucial component of the Earth system; they comprise a large portion of terrestrial carbon stocks, mediate the supply and demand of nutrients, and influence the overall response of terrestrial ecosystems to perturbations. In this paper, we develop a new soil biogeochemistry model for the Community Land Model, version 4 (CLM4). The new model includes a vertical dimension to carbon (C) and nitrogen (N) pools and transformations, a more realistic treatment of mineral N pools, flexible treatment of the dynamics of decomposing carbon, and a radiocarbon ( 14 C) tracer. We describe the model structure, compare it with site-level and global observations, and discuss the overall effect of the revised soil model on Community Land Model (CLM) carbon dynamics. Site-level comparisons to radiocarbon and bulk soil C observations support the idea that soil C turnover is reduced at depth beyond what is expected from environmental controls for temperature, moisture, and oxygen that are considered in the model. In better agreement with observations, the revised soil model predicts substantially more and older soil C, particularly at high latitudes, where it resolves a permafrost soil C pool. In addition, the 20th century-C dynamics of the model are more realistic than those of the baseline model, with more terrestrial C uptake over the 20th century due to reduced N downregulation and longer turnover times for decomposing C.

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Fine‐root mortality rates in a temperate forest: estimates using radiocarbon data and numerical modeling

Cited by 48 publications

References 51 publications

Nine Years of Irrigation Cause Vegetation and Fine Root Shifts in a Water-Limited Pine Forest

Nine Years of Irrigation Cause Vegetation and Fine Root Shifts in a Water-Limited Pine Forest

Does the age of fine root carbon indicate the age of fine roots in boreal forests?

The effect of vertically resolved soil biogeochemistry and alternate soil C and N models on C dynamics of CLM4

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