Responses of tree fine roots to temperature

Abstract

Soil temperature can influence the functioning of roots in many ways. If soil moisture and nutrient availability are adequate, rates of root length extension and root mortality increase with increasing soil temperature, at least up to an optimal temperature for root growth, which seems to vary among taxa. Root growth and root mortality are highly seasonal in perennial plants, with a flush of growth in spring and significant mortality in the fall. At present we do not understand whether root growth phenology responds to the same temperature cues that are known to control shoot growth. We also do not understand whether the flush of root growth in the spring depends on the utilization of stored nonstructural carbohydrates, or if it is fueled by current photosynthate. Root respiration increases exponentially with temperature, but Q "! values range widely from c. 1.5 to 3.0. Significant questions yet to be resolved are : whether rates of root respiration acclimate to soil temperature, and what mechanisms control acclimation if it occurs. Limited data suggest that fine roots depend heavily on the import of new carbon (C) from the canopy during the growing season. We hypothesize that root growth and root respiration are tightly linked to whole-canopy assimilation through complex source-sink relationships within the plant. Our understanding of how the whole plant responds to dynamic changes in soil temperature, moisture and nutrient availability is poor, even though it is well known that multiple growth-limiting resources change simultaneously through time during a typical growing season. We review the interactions between soil temperature and other growth-limiting factors to illustrate how simple generalizations about temperature and root functioning can be misleading.

Hydrological response to climate change in the Lesse and the Vesdre catchments: contribution of a physically based model (Wallonia, Belgium)

“…The development of plant root systems is closely impacted by the evolution of soil temperature. So it appears that global warming could result in an earlier root growth in spring (Pregitzer et al, 2000;Zhou and Shangguan, 2006) which is in accordance with our results.…”

Invariant allometric scaling of nitrogen and phosphorus in leaves, stems, and fine roots of woody plants along an altitudinal gradient

“…Previous studies found a "slow-return" strategy of leaves (Wright et al 2004) to make plant more resistant to temperature stress and nutrient limitation. Meanwhile, a similar strategy has also been reported in root systems Pregitzer et al 2000). It suggested that plant might coordinately decline the metabolic rates and nutrient content of above and below plant organs to maximize plant fitness under stressful environments.…”

Temperate and boreal forest tree phenology: from organ-scale processes to terrestrial ecosystem models

“…Still, in fine roots, growth and mortality are generally out of phase, creating a distinct pattern for the overall phenologies of root systems. Characteristic features for temperate and boreal trees are a burst of fine root growth in spring/summer and significant mortality in late summer/ autumn (Pregitzer et al 2000;Joslin et al 2001; see also McCormack et al 2014) (Fig. 3), resulting in strikingly similar overall patterns of fine root production and mortality among deciduous and evergreen tree species growing under the same climate (Quan et al 2010).…”

“…We still know very little regarding the environmental controls on the mortality of fine roots (Pregitzer 2002), but studies of fine root lifespans suggest that both elevated temperatures and soil moisture deficits promote root mortality (Pregitzer et al 2000;Eissenstat et al 2013). In addition to interspecific differences (Leuschner et al 2001) and methodological aspects (Gaul et al 2008), non-linearity and differential sensitivities among the responses of fine root growth and mortality to soil water deficits likely contribute to the variation among the responses of root biomass to soil drought observed in field studies, which have reported both increases (Joslin and Wolfe 1998;Leuschner et al 2001) and decreases (Konôpka et al 2005) in live root biomass.…”