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Forbes, Paula; Black, Kyrsten E.; Hooker, J. E.

doi:10.1023/a:1004298804353

Cited by 70 publications

(14 citation statements)

References 14 publications

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“…As such, many studies have focused on the effects of rising temperature on ecosystems and belowground processes. Results from these studies have been relatively consistent with most reporting decreased root lifespan with increasing temperatures (Forbes et al, 1997; King et al, 1999; Majdi and Ohrvik, 2004; Leppälammi-Kujansuu et al, 2014), or in some cases, no change (Fitter et al, 1999; Johnson et al, 2006). However, a study by Bai et al (2012) did observe that constraining increased temperature to daylight hours (i.e., equal temperatures at night between control and treatment groups) induced a slight increase in root lifespan.…”

Section: Variation In Fine Root Lifespan Along Environmental Gradientssupporting

confidence: 76%

Impacts of environmental factors on fine root lifespan

2014

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The lifespan of fast-cycling roots is a critical parameter determining a large flux of plant carbon into soil through root turnover and is a biological feature regulating the capacity of a plant to capture soil water and nutrients via root-age-related physiological processes. While the importance of root lifespan to whole-plant and ecosystem processes is increasingly recognized, robust descriptions of this dynamic process and its response to changes in climatic and edaphic factors are lacking. Here we synthesize available information and propose testable hypotheses using conceptual models to describe how changes in temperature, water, nitrogen (N), and phosphorus (P) availability impact fine root lifespan within a species. Each model is based on intrinsic responses including root physiological activity and alteration of carbohydrate allocation at the whole-plant level as well as extrinsic factors including mycorrhizal fungi and pressure from pathogens, herbivores, and other microbes. Simplifying interactions among these factors, we propose three general principles describing fine root responses to complex environmental gradients. First, increases in a factor that strongly constrains plant growth (temperature, water, N, or P) should result in increased fine root lifespan. Second, increases in a factor that exceeds plant demand or tolerance should result in decreased lifespan. Third, as multiple factors interact fine root responses should be determined by the most dominant factor controlling plant growth. Moving forward, field experiments should determine which types of species (e.g., coarse vs. fine rooted, obligate vs. facultative mycotrophs) will express greater plasticity in response to environmental gradients while ecosystem models may begin to incorporate more detailed descriptions of root lifespan and turnover. Together these efforts will improve quantitative understanding of root dynamics and help to identify areas where future research should be focused.

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Section: Variation In Fine Root Lifespan Along Environmental Gradientssupporting

confidence: 76%

Impacts of environmental factors on fine root lifespan

2014

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“…They exude high quantities of soluble organic substrates, up to 500 g kg"' root dry weight after 4 wk of growth following germination (Lynch and Whipps, 1990), which may represent 65% of the net COj assimilated by ryegrass and translocated into the rhizosphere in 4 wk (Meharg and Killham, 1990). Moreover, the roots of ryegrass have a short life span, with only 50% surviving >30 d (Forbes et al, 1997). Hence, ryegrass was chosen as a test plant in this investigation.…”

Section: Discussion Distribution Gradient Of Root Exudates In the Rhimentioning

confidence: 99%

Gradient Distribution of Root Exudates and Polycyclic Aromatic Hydrocarbons in Rhizosphere Soil

Gao

Yang

Ling

et al. 2011

Soil Science Society of America Journal

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The gradients of root exudates and of persistent organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), in rhizosphere soil in proximity to the root surface are still not well elucidated. In this work, a greenhouse experiment was conducted to investigate the distribution gradients of root exudates and phenanthrene and pyrene, as selected PAHs, in rhizosphere soil close to (0-8 mm) the root surface of ryegrass [Ldium multiflorum Lam.) as the host plant. Rhizosphere soil from the root surface (0-8 mm) was divided into three layers: the rhizoplane and strongly and loosely adhering soil. Root exudates were characterized as soluble organic C, organic acids, and total soluble sugars. In PAH-spiked rhizosphere soils, the concentration of root exudates decreased with distance from the roots. In a sterilized treatment, the amounts of root exudates in the three rhizosphere layers were higher than when the soil was not sterilized, indicating that microbial consumption contributed significantly to the loss of root exudates in the rhizosphere. Tlie residual concentrations of phenanthrene and pyrene clearly increased in die order of rhizoplane to loosely adhering soil after 40 to 50 d, which was significantly and negatively correlated with the amount of root exudates in the rhizosphere. In total, 87 to 97% of phenanthrene and 69 to 79% of pyrene dissipated in all three layers of rhizosphere soil after 40 d, and >99% of phenanthrene and 93% of pyrene dissipated after 50 d. The degradation ratio of PAHs decreased in rhizosphere soils with distance from the roots.Abbreviations: OA, organic acid; PAH, polycyclic aromatic hydrocarbon: SOC, soluble organic carbon: TSS,) total soluble sugar.

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“…Increased photosynthesis under elevated CO 2 stimulates belowground C input, fine-root growth (Curtis, 1996;Curtis and Wang, 1998;Pendall et al, 2005) and root turnover rates and biomass (Berntson and Bazzaz, 1997b;Fitter et al, 1999;Allen et al, 2000;Pregitzer et al, 2000;Wan et al, 2004). Increased fine-root production and mortality are associated with higher temperatures (Gill and Jackson, 2000) and turnover rates Pregitzer, 1993b, 1997;Forbes et al, 1997;Fitter et al, 1999;King et al, 1999;Wan et al, 2004). Turnover rates increase with increased C allocation to root systems when plants are grown under elevated CO 2 , at least in grasslands and forest (Fitter et al, 1996).…”

Section: Root Mortality/root Turnovermentioning

confidence: 99%

Dynamics of Plant Root Growth under Increased Atmospheric Carbon Dioxide

2013

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Plant growth is influenced by above‐ and belowground environmental conditions and increasing atmospheric carbon dioxide (CO2) concentrations enhances growth and yield of most agricultural crops. This review covers current knowledge on the impact of increasing CO2 concentration on root dynamics of plants in terms of growth, root/shoot (R/S) ratio, root biomass, root length, root longevity, root mortality, root distribution, root branching, root quality, and the response of these root parameters to management practices including soil water and nutrients. The effects of CO2 concentration on R/S ratio are contradictory due to complexity in accurate underground biomass estimation under diverse crops and conditions. Roots become more numerous, longer, thicker, and faster growing in crops exposed to high CO2 with increased root length in many plant species. Branching and extension of roots under elevated CO2 may lead to altered root architecture and ability of roots to acquire water and nutrients from the soil profile with exploration of the soil volume. Root turnover is important to the global C budget as well as to nutrient cycling in ecosystems and individual plants. Agricultural management practices have a greater impact on root growth than rising atmospheric CO2 since management practices influence soil physical, chemical, and biological properties of soil, consequently affects root growth dynamics in the belowground. Less understood are the interactive effects of elevated CO2 and management practices including drought on root dynamics, fine‐root production, and water‐nutrient use efficiency, and the contribution of these processes to plant growth in water and nutrients limited environments.

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Cited by 70 publications

References 14 publications

Impacts of environmental factors on fine root lifespan

Impacts of environmental factors on fine root lifespan

Gradient Distribution of Root Exudates and Polycyclic Aromatic Hydrocarbons in Rhizosphere Soil

Dynamics of Plant Root Growth under Increased Atmospheric Carbon Dioxide

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