The relationship between plant species richness and soil aggregate stability can depend on disturbance

Abstract

Aims Plant diversity has been shown to significantly increase topsoil aggregate stability of machine-graded ski slopes. We hypothesise that this effect is specific for these disturbed sites and that at sites of low and no disturbance the effect decreases. Methods We determined plant species richness, cover percentage of five functional groups, root (length) density, and biomass as well as soil aggregate stability, gravimetric soil moisture, soil density, and particle size distribution at different levels of disturbance (i.e. graded and un-graded ski slopes and the surrounding area). Results Plant species richness, vegetation cover, aggregate stability and soil moisture were significantly reduced on machine-graded slopes compared to control plots but hardly on un-graded slopes. On the contrary, machine-grading increased soil density and friction angle compared to un-graded ski slopes. The influence of species richness on aggregate stability was only positive on gravely soils and graded ski slopes. Aggregate stability increased linearly up to approximately eight plant species, 70% vegetation cover and 0.006 gcm −3 root density. Conclusions Our study showed that the relationship between plant diversity and aggregate stability was strongest on slopes with high disturbance and relatively low species numbers. We suggest that high plant diversity, vegetation cover and root density need to be established after major human disturbance such as grading.

The use of mycorrhiza for eco‐engineering measures in steep alpine environments: effects on soil aggregate formation and fine‐root development

“…(), who found six to 10 times higher RLD in the 25 year old eco‐engineered site compared to an untouched control site. Similar results were reported from a ski run where RLD was significantly higher on non‐graded compared to graded slopes which was further positively linked with plant cover and species diversity (Pohl et al ., ). Additionally, a higher proportion of roots in the finest root diameter class 1 was reported with the very fine roots contributing 90% to RLD (Pohl et al ., ).…”

“…A significant impact of RLD on aggregate stability was also reported out in other studies (e.g. Fattet et al ., ; Pohl et al ., , ).…”

How natural capital delivers ecosystem services: A typology derived from a systematic review

“…For mass flow regulation, functional characteristics such as root depth, strength, density and structure are often found to be important for binding soil particles together and increasing soil infiltration (e.g. de Baets et al, 2009;Pohl et al, 2012). The structure, strength and elasticity of the above-ground vegetation is also important for intercepting rainfall, resisting water flow and trapping sediment, and the thickness and quality of the litter layer plays a key role in improving soil structure and protecting the soil surface from erosion (e.g.…”

“…For mass flow regulation, for example, 37 out of 60 papers cite negative (or mixed positive and negative) human impacts, mainly from overgrazing or intensive cultivation of arable land, though also from fuelwood collection, skirun construction and road building (e.g. Garcia Nacinovic et al, 2014;Liu et al, 2014;Pohl et al, 2012). However, 20 of these papers show how impacts could be mitigated through restoration and soil-water conservation methods such as re-planting or re-seeding with protective vegetation, constructing low walls or terraces on steep slopes, establishing contour hedges or grass buffer strips between fields, using cover crops to avoid bare soil in winter, and shifting to no-till agriculture (e.g.…”

Effects of Root Architecture Characteristics on Soil Reinforcement in Undisturbed Soil

“…For herbs, the existence of a large number of adventitious roots in the shallow soil layer did not increase the soil shear strength. Loose soil caused by root growth 38,39 weakened soil shear strength. However, with an increase in soil depth and a decrease in the number of roots, soil shear strength in 0.2-0.4 m soil layer was higher than that in 0-0.2 m soil layer.…”