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

Abstract

Aims: (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. Methods: Root diameter distribution (e5 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.Results: 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). Conclusions: 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 Plant Soil (2011) 348:471-489

Depth distribution of roots of Eucalyptus dunnii and Corymbia citriodora subsp. variegata in different soil conditions

“…The high concentration of roots observed in the upper soils in this study has been reported from other plantations for a range of species (Carbon et al, 1980;Nambiar, 1983Nambiar, , 1990Livesley et al, 2000;Bouillet et al, 2002;Macinnis-Ng et al, 2010;Gwenzi et al, 2011;Levillain et al, 2011) and for native forests (Jackson et al, 1996). Cumulative root fraction down the profile was fitted to the model: Y = 1 À b d where Y = cumulative root fraction, b is a constant defined by the data and d is depth in cm (Gale and Grigal, 1987).…”

Transpiration and water relations of evergreen shrub species on an artificial landform for mine waste storage versus an adjacent natural site in semi‐arid Western Australia

“…Limited root density in deeper soil layers is common in young vegetation stands on rehabilitated mined landforms and is often associated with physical or mechanical constraints to root growth (e.g. Szota et al ., ; Gwenzi et al ., ). In addition, material segregation and self‐filtration, which are common phenomena on coarse‐textured and highly heterogeneous tailings and mine rock wastes [Figure (a,b)] could have enhanced the transport of fines into deeper layers, resulting in increased soil moisture retention at that depth (e.g.…”

“…In addition, empirical evidence indicates that, even in cases where the cover layer is very thick, the development of deep root system is often constrained by shallow soils and chemical and physical constraints to root growth (e.g. Szota et al ., ; Gwenzi et al ., ). In view of this, particular attention should be paid to understand substrate properties limiting root growth and manipulation of such properties to enhance the development of a dense and deep root system rather than mere thickness of the storage layer.…”

“…Previous studies have also shown that, compared with natural ecosystems, artificial ecosystems such as engineered covers and rehabilitated mined sites may exhibit unique soil hydrology, material hydraulic properties and subsoil chemical and physical constraints, which may in turn, restrict root development and vegetation water use (e.g. Rokich et al ., ; Wehr et al ., ; Szota et al ., ; Gwenzi et al ., ). Until now, few field studies have investigated the ecophysiology and water use of woody shrubs on artificial ecosystems associated with hazardous mine waste disposal (Grigg et al ., ; Gwenzi et al ., ).…”

“…In a seasonally dry Mediterranean environment in Western Australia, annual stand water use of an evergreen woodland on a young artificial ecosystem constructed from highly porous bauxite residue sand was quite low (147 mm), accounting for only 22% of annual rainfall (Gwenzi et al ., ). The low vegetation water use was attributed to the collective impacts of low moisture storage and high material saturated hydraulic conductivity of the sandy material, low leaf area index ( LAI ) and sapwood area ( SA ) associated with a young stand and a shallow root system constrained by high subsoil pH and highly seasonal rainfall (Gwenzi et al ., ,; Gwenzi et al ., ). Extrapolation of existing information on vegetation water use obtained from Mediterranean conditions (e.g.…”