Root distribution and properties of a young alley-cropping system: effects on soil carbon storage and microbial activity

Abstract

Purpose In agroforestry systems, the root distributions and properties of the annual and perennial vegetation are poorly known, although they are recognized for fostering soil carbon (C) stocks through annual root-derived C inputs and by altering microbial activity. This study aimed to evaluate the potential contribution of roots from the understory vegetation strip (UVS) and the crop to top-and subsoil C stocks (0-100 cm) to a 3-year-old agroforestry system of the alley-cropping type. Methods Root biomass, chemical composition, functional traits and anatomical structure were assessed in parallel to a characterization of soil physicochemical

Spatial distribution of tree and grassland fine roots in an alley cropping system

“…Choosing a low sampling depth will lead to an underestimation of below-ground C storage by tree roots (Figure S1). On the other hand, the C turnover in the subsoil is poorly understood and Siegwart et al (2023) did not find a positive correlation between root C stocks and SOC for depths > 50 cm. Our results showed that the total C stock in the root system was higher up to a distance of 3.5 m compared to the grassland reference.…”

“…However, the fine root distribution measured in our study showed that the trees allocated carbon to the subsoil via their root system. The mechanism of subsoil C storage poses many open questions (Siegwart et al, 2023) and is especially interesting for mixed cropping systems that can potentially increase C storage in soils compared to cropland. High deviations between sampling points as seen in Figure 1 have to be taken into account when interpreting the results and show that a high number of repetitions is needed for studies on complex interactions of root systems.…”

“…Cardinael et al (2015) found increased SOC under trees, but no effect of distance to the trees in a Mediterranean alley cropping system and Angst et al (2016) report the same for a forest site. Similarly, Siegwart et al (2023) found correlations between root C stocks and SOC for depths of up to 50 cm, but not for the subsoil. Direct predictions on root C input in the subsoil based on measurements of FRD are not possible with the present state of knowledge on the stability and turnover times of the C pools.…”

Growth responses of grass swards to tree-mediated temporal and spatial dynamics of light and temperature in a silvopastoral system

“…Choosing a low sampling depth will lead to an underestimation of below-ground C storage by tree roots (Figure S3.2). On the other hand, the C turnover in the subsoil is poorly understood and Siegwart et al (2023) did not find a positive correlation between root C stocks and SOC for depths > 50 cm. Our results showed that the total C stock in the root system was higher up to a distance of 3.5 m compared to the grassland reference.…”

“…However, the fine root distribution measured in our study showed that the trees allocated carbon to the subsoil via their root system. The mechanism of subsoil C storage poses many open questions (Siegwart et al, 2023) and is especially interesting for mixed cropping systems that can potentially increase C storage in soils compared to cropland. High deviations between sampling points as seen in Figure 3.1 have to be taken into account when interpreting the results and show that a high number of repetitions is needed for studies on complex interactions of root systems.…”