Spatial analysis of fine root distribution on a recently constructed ecosystem in a water-limited environment

Abstract

1) to investigate the spatial distribution of fine roots and its correlation with selected soil properties on an artificial ecosystem dominated by woody vegetation species, and (2) to compare the root distribution to that predicted using a global model for natural ecosystems. Root diameter distribution (≤5 mm), root biomass density (RBD), root length density (RLD), soil pH, soil electrical conductivity and dry soil bulk density were measured on soil core samples (217) collected from a trench wall using a 20×20-cm grid sampling. Approximately 90% of the RBD (mean ± standard error: 0.27±0.027 kg m −3 ) and RLD (1.57±0.023 cm cm −3 ) occurred in the top 40 cm, decreasing exponentially to a maximum rooting depth of 150 cm. RBD exhibited a vertical spatial structure associated with soil pH (p<0.05; r 2 = 0.48), and a random lateral distribution. Coefficients of variation (CV) of RBD were high irrespective of orientation (vertical: 79-200%, lateral: 50-236%). The root extinction parameter β (0.944) for the global model was lower (p<0.05) than that of woodlands (β= 0.964-0.976), indicating a shallow root distribution resembling that of grasslands (β=0.943). The superficial root distribution indicated subsoil chemical constraints to root growth, while high lateral variability was attributed to sparse vegetation. The findings stress the need to account for both vertical and lateral variability of roots for accurate modelling of water use and productivity on certain artificial ecosystems with sparse vegetation.Keywords Global root distribution model . Vegetated engineered cover . Root biomass density . Root diameter distribution . Root length density Abbreviations ECSoil electrical conductivity in 1:5 soil to water suspension Plant Soil (2011) 344:255-272

The distribution of fine root length density for six artificial afforestation tree species in Loess Plateau of Northwest China

“…2010; Armas et al, 2012). Many perennial plants in semi-arid regions have shallow roots to absorb soil water from rainfall and/or deep roots to access groundwater and deep soil moisture (Gwenzi et al, 2011) thereby taking up water from groundwater, surface processes or both sources (Jackson et al, 2008;Nagler et al, 2008). Correlating the fine roots to soil water contents may lead to a greater understanding of how different plants respond to heterogeneity in soil moisture and provide a better understanding of fine root growth dynamics.…”

“…Examining the distribution of fine roots of plants is important for understanding the water use strategy of plants. However, the number of studies on the fine root distribution of woody species is small (Zhou & Shangguan, 2007;February & Higgins, 2010;Gwenzi et al, 2011).…”

“…Low dry soil bulk density values below 1.6 g cm -3 considered to be the upper threshold value for optimum root growth (Courtney & Timpson, 2005;Szota et al, 2007) was attributed to the coarse-textured and highly porous nature of the material (Gwenzi et al, 2011). Accordingly, dry soil bulk density was related to root density, indicating physical impedance to root growth.…”

“…The accumulation of litter and soil organic matter on level micro sites and topographic depressions, close to standing dead trees or their remains and the channels created by the decaying thick roots, may create nutrient patches where fine roots proliferate (Roy & Singh, 1995). Fine root proliferation in fertile patches had been shown in different ecosystems (Gwenzi et al, 2011). Similarly, on a vertical gradient, the accumulation of litter on the surface soil promotes nutrient concentration and thus fine root accumulation in the upper layers of the soil (Courtney & Timpson, 2005).…”

“…This enables more soil resource uptake since water enters the soil profile predominantly from the soil surface in most ecosystems, and nutrient concentrations are commonly higher in the upper soil layers (Schenk, 2008). Most earlier studies focused on one-dimensional or root depth distribution (Bennett et al, 2009;Macinnis-Ng et al, 2010), 2 N concentration or soil properties (Zhou & Shangguan, 2007;February and Higgins, 2010;Gwenzi et al, 2011).…”