Spatial analysis of fine root distribution on a recently constructed ecosystem in a water-limited environment
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(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; r2 = 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.
KeywordsGlobal root distribution model Vegetated engineered cover Root biomass density Root diameter distribution Root length density
Soil electrical conductivity in 1:5 soil to water suspension
Root biomass density
Root length density
Dry soil bulk density
The authors thank the anonymous reviewers whose insightful critique of the manuscript significantly improved it. We are also grateful to the Cover Project (Ex-Australian Centre for Mining Environmental Research) for research funding. The design and implementation of the experiment, and analysis and interpretation of the data were solely the responsibilities of the authors. Scholarship support for WG was provided by The University of Western Australia through the Scholarship for International Research Fees (SIRF), University Postgraduate Award (International Student) (UPAIS) and an Ad-hoc top-up scholarship. Mr. Johannes Albers assisted with fieldwork and laboratory analysis.
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