Abstract
Aim of study: The study was conducted to characterize the impacts of plant roots systems (e.g., root length density and root biomass) on soil preferential flow in forest ecosystems.Area of study: The study was carried out in Jiufeng National Forest Park, Beijing, China.Material and methods: The flow patterns were measured by field dye tracing experiments. Different species (Sophora japonica Linn, Platycladus orientalis Franco, Quercus dentata Thunb) were quantified in two replicates, and 12 soil depth were applied. Plant roots were sampled in the sieving methods. Root length density and root biomass were measured by WinRHIZO. Dye coverage was implied in the image analysis, and maximum depth of dye infiltration by direct measurement.Main results: Root length density and root biomass decreased with the increasing distance from soil surface, and root length density was 81.6% higher in preferential pathways than in soil matrix, and 66.7% for root biomass with respect to all experimental plots. Plant roots were densely distributed in the upper soil layers. Dye coverage was almost 100% in the upper 5-10 cm, but then decreased rapidly with soil depth. Root length density and root biomass were different from species: Platycladus orientalis Franco > Quercus dentata Thunb > Sophora japonica Linn.Research highlights: The results indicated that fine roots systems had strong effects on soil preferential flow, particularly root channels enhancing nutrition transport across soil profiles in forest dynamics.Key words: soil preferential flow; preferential pathways; soil matrix; root length density; root biomass.
Highlights
Soil preferential flow as a spatially and temporally highly random and essentially unpredictable process (Hendrickx & Flury, 2001) and a common phenomenon in pedological perspectives (Bonger et al, 2008) results in complex flow patterns bypassing soil matrix and increases the risk of pollutants (e.g. Heavy Metal, Radionuclides) reaching greater soil depths (Nimmo, 2012)
Flow in the soil matrix pores at the pedon scale results from spatial heterogeneity in texture, bulk density, stones or rock fragments and water repellency, while flow in continuous and large pores or macropores at the pore scale arises from different interactions: biopores formed by plant root systems and macrofauna, cracks formed by freeze and thaw or swell and shrinkage circles, voids formed by irrigation, cultivation, and tillage (Jarvis et al, 2012)
As seen from the figure, dye coverage displayed at the same site was not similar to some extent, which was probably due to soil heterogeneity, abundant rock fragments and gravels in the study sites
Summary
Soil preferential flow (e.g., macropore flow, finger flow and funnel flow) as a spatially and temporally highly random and essentially unpredictable process (Hendrickx & Flury, 2001) and a common phenomenon in pedological perspectives (Bonger et al, 2008) results in complex flow patterns bypassing soil matrix and increases the risk of pollutants (e.g. Heavy Metal, Radionuclides) reaching greater soil depths (Nimmo, 2012). Soil matrix flow and preferential flow are two typical permeating patterns of water flow and solute transport (Jarvis et al, 2012). Flow in the soil matrix pores at the pedon scale results from spatial heterogeneity in texture, bulk density, stones or rock fragments and water repellency, while flow in continuous and large pores or macropores at the pore scale arises from different interactions: biopores formed by plant root systems and macrofauna, cracks formed by freeze and thaw or swell and shrinkage circles, voids formed by irrigation, cultivation, and tillage (Jarvis et al, 2012)
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