Experimental evidence for drought induced alternative stable states of soil moisture

Abstract

Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction.

Shrubland primary production and soil respiration diverge along European climate gradient

“…Recent research shows that drought-induced alteration of the soil structure can cause a major shift in soil moisture behaviour13 but the impact on Rs remains to be explored.…”

Dielectric Properties of Glass Beads with Talc as a Reference Material for Calibration and Verification of Dielectric Methods and Devices for Measuring Soil Moisture

“…The monitoring of soil water content provides essential information that is necessary to mitigate the impact of natural disasters like floods or droughts, and it is also a valuable tool for a precise irrigation, which, in turn, can bring reductions in water consumption [1,2]. There are several methods used to measure soil moisture that can be divided into in-situ methods and remote methods.…”

Consistency and Discrepancy of Global Surface Soil Moisture Changes From Multiple Model‐Based Data Sets Against Satellite Observations

“…Thus, spatial coverages of in situ measurements are usually limited (Ochsner et al, 2013;Qin et al, 2009). Because of the high temporal and spatial resolutions and extensive spatial coverages of model simulations relative to in-site measurements, model simulations of soil moisture have been widely adopted in regional and global studies around the world to investigate different hydrological issues, such as historical and future changes in soil moisture (e.g., Chen et al, 2016;Cheng et al, 2015Cheng et al, , 2017, dynamics of land-atmosphere interactions (e.g., Gerken et al, 2015;May et al, 2015), improvement of HM simulations (e.g., Heße et al, 2017), and monitoring of droughts (e.g., Robinson et al, 2016).…”