Abstract
This study discusses penetration resistance (PR) of forested Pumice-Andosol sites. PR, a key soil property influencing root growth and elongation, exerts a substantial influence on ecological site quality and tree growth. Andosols were expected to show low PR because of their unique characteristics (low bulk density, loose soil matrix). Five sites, two undisturbed and three backfilled, were sampled. The latter result from pumice excavation and were examined to quantify potential PR alterations in the aftermath of backfilling and pumice removal. Penetrologger sampling on undisturbed sites showed mean PR not exceeding 3 MPa, a literature-based, critical threshold restricting root growth, in the upper 0.80 m, indicating conditions fostering tree rooting. Backfilled sites mostly exhibited increased (> 3 MPa) PR, leading to rooting restrictions even beginning at −0.21 m. Deviations from undisturbed soils range from −15.6 to +109.3% depending on depth and age of the backfilled site. Furthermore, GIS-based data interpolation helped to identify spatial PR patterns and allowed a direct comparison before/after backfilling at one site. Statistical analysis revealed significantly altered PR after backfilling, while a concluding ANOVA provided at least significant governing factors (depth, area, clay + silt content, soil organic matter), albeit with only small effect sizes.
Highlights
Soil penetration resistance (PR), often described as “( . . . ) the resistance of the soil to deformation ( . . . )” [1] (p. 1), is one of the governing soil physical characteristics for root growth and elongation (e.g., [1,2,3,4,5])
Statistical analysis revealed significantly altered PR after backfilling, while a concluding ANOVA provided at least significant governing factors, albeit with only small effect sizes
In [13], the authors proved that 70% of all tree roots found in field observations at sandy, backfilled excavation sites were located in soils exhibiting a PR < 2 MPa
Summary
Soil penetration resistance (PR), often described as “( . . . ) the resistance of the soil to deformation ( . . . )” [1] (p. 1), is one of the governing soil physical characteristics for root growth and elongation (e.g., [1,2,3,4,5]). Soil penetration resistance (PR), often described as “( . 1), is one of the governing soil physical characteristics for root growth and elongation (e.g., [1,2,3,4,5]). There have been studies explicitly addressing forest sites (e.g., [13,14,15,16,17]). Both consistently describe critical penetration resistances: 2 MPa is often considered to be a threshold for root growth and elongation. [2] observed root elongation rates reduced by 50% at PR = 2 MPa under laboratory conditions. In soils exceeding 3 MPa, only 10% of all roots were found
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