Linking root traits to plant physiology and growth in Fraxinus angustifolia Vahl. seedlings under soil compaction conditions

Abstract

Roots are immersed in a soil matrix with different and contrasting conditions that may affect their anatomy, structure and function. Soil chemical factors, texture and compaction are some of the main factors experienced by roots. This study investigates how soil compaction and soil type can modify root anatomy and morphology, and, thus, plant physiology and growth. Seedlings of a woody species (Fraxinus angustifolia Vahl.) were grown in a greenhouse with two types of soil (loam and sandy-loam) under a wide range of soil compaction. Despite intrinsic differences in the chemical properties of the two soils, soil compaction explained much of the variation in root morphology and anatomy. We found, in a single species, a high root plasticity in different key root traits as a response to soil compaction. Soil compaction affected negatively the proportion of fine roots, specific root length and proportion of the root xylem vessels. These effects on root traits had an influence on plant physiology and growth. A causal model (by d-sep method) found that soil compaction affected specific root length, and this affects transpiration and photosynthesis rates. Also, the effect of soil compaction on xylem vessel proportion and xylem vessel diameter affected plant area and plant biomass. In conclusion, soil compaction shows an important effect on root anatomy and morphology during the seedling stage, with consequences on plant physiology and growth.