Climate-induced changes in continental-scale soil macroporosity may intensify water cycle

Abstract

Soil macroporosity affects field-scale water-cycle processes, such as infiltration, nutrient transport and runoff, that are important for the development of successful global strategies that address challenges of food security, water scarcity, human health and loss of biodiversity. Macropores-large pores that freely drain water under the influence of gravity-often represent less than 1 per cent of the soil volume, but can contribute more than 70 per cent of the total soil water infiltration, which greatly magnifies their influence on the regional and global water cycle. Although climate influences the development of macropores through soil-forming processes, the extent and rate of such development and its effect on the water cycle are currently unknown. Here we show that drier climates induce the formation of greater soil macroporosity than do more humid ones, and that such climate-induced changes occur over shorter timescales than have previously been considered-probably years to decades. Furthermore, we find that changes in the effective porosity, a proxy for macroporosity, predicted from mean annual precipitation at the end of the century would result in changes in saturated soil hydraulic conductivity ranging from -55 to 34 per cent for five physiographic regions in the USA. Our results indicate that soil macroporosity may be altered rapidly in response to climate change and that associated continental-scale changes in soil hydraulic properties may set up unexplored feedbacks between climate and the land surface and thus intensify the water cycle.

A Review of Geophysical Methods for Soil Structure Characterization

“…For example, the parameterization of land‐surface model often relies on the use of pedotransfer functions that relate soil attributes (often soil texture only) to hydraulic parameters. Recent studies have advocated for the urgent to include soil structure that could significantly affect infiltration and runoff in ways not predicted by soil texture (Hirmas et al, ; Or et al, ; Vereecken et al, ). In addition, the trend of agricultural intensification and associated adverse impacts on soil compaction and structure are expected to affect food security (Zhang et al, ).…”

Effects of rainfall intensity and compaction on water transport from opencast coal mine soils: An experimental study

“…Frey, Niklaus, Kremer, Luescher, and Zimmermann (2011) found that compaction resulting from machine passes mainly decreased the macropore volume and lowered the hydraulic conductivities of the soil. The macropores account for less than 1% of the soil volume, but they can contribute more than 70% of the total soil water infiltration (Hirmas et al, 2018;Watson & Luxmoore, 1986). In the mining area, the use of heavy machinery inevitably resulted in a reduction in the macropore volume of the soil, thus reducing water infiltration and increasing runoff.…”

Responses of soil water storage and crop water use efficiency to changing climatic conditions: A lysimeter-based space-for-time approach

“…showed that the inter-annual variation of the SWS at northern middle and high latitudes increased under a warmer climate with higher values during the wetter and lower values of the SWS during the drier season. In this case, the frequency of water logging events or soil crack formation will increase and probably alter soil properties such as macroporosity and SWSC and thus affect vadose zone hydrology at different scales (Robinson et al, 2016;Hirmas et al, 2018). Robinson et al (2016) showed for a manipulative long-term experiment that intense summer droughts altered the soil water retention characteristic and lowered the SWSC.…”