Environmental control of fine root dynamics in a northern hardwood forest

Abstract

Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over‐winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems.

Root elongation in tropical Eucalyptus plantations: effect of soil water content

“…Seasonality in root elongation has been reported in a limited number of studies, and it was ascribed to the interaction of both endogenous and exogenous factors (Côté et al, 1998;Tierney et al, 2003). Soil temperature and soil water availability are among the exogenous factors that have been investigated more (Halter et al, 1996;Ni et al, 2000;Tierney et al, 2003).…”

Soil water potential determines the presence of hydraulic lift of Populus euphratica Olivier across growing seasons in an arid desert region

“…Due to the absence of transpiration, the water potential in the root system was basically a constant, roughly equalling to the water potential of deep soils during the presence of HL at night (Phillips et al 2002;Williams, Araujo 2002). On the contrary, SWP differed among soil layers at night in the arid desert regions due to the influence of the uneven distribution of water resource and roots (Shein, Pachepsky 1995;Tierney et al 2003). In this case, the water potential difference between the plant roots and its adjacent soils may be different among the soil layers.…”

“…In the early stage of plant growing season (i.e. June), due to plant owning higher demand in minerals, P. euphratica develop numerous fine roots in shallow soil layers to absorb minerals (Shein, Pachepsky 1995;Tierney et al 2003;Cheng et al 2009). This might increase the water potential difference between fine roots and their adjust soils, and subsequently, result in the lowest SWP soil layer appearing in shallow layers.…”

“…Due to the water transportation from plant roots to stem and leaves, previous studies indicated that RWP decreases from deep roots to shallow roots in the plant (Zimmermann 1984;Kramer, Boyer 1995). Oppositely, because SWP could be influenced by the variations in fine roots distribution, and the relationship between roots and soils (Shein, Pachepsky 1995;Tierney et al 2003), it has no monotonically decreasing trends with soil depth and RWP (Eissenstat, Yanai 1997;Jiang et al 2006;Hao et al 2013). Thus, it is possible that the relative relationship between RWP and SWP, as a consequent influence SWP threshold may vary among soil layers within the process of HL.…”

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

“…Soils devoid of a snowpack are more vulnerable to freezing and hence to physical and chemical changes, including the death of fine roots, cell lysis, and the alteration of soil microbial processes (Tierney et al 2001;Christopher et al 2008;Shibata et al 2013). Experimental snow removal in alpine Europe lowered soil temperatures and increased NO 3 -release (Freppaz et al 2008).…”