Fuzzy modelling and mapping soil moisture for observed periods and climate scenarios. An alternative for dynamic modelling at the national and regional scale?

Abstract

Key message Average soil moisture was spatially modelled for observed periods and climate scenarios using a fuzzy logic approach. Accordingly, a significant decline of soil moisture until 2070 in Germany and the Kellerwald National Park could be evidenced for soils influenced by ground water and by stagnant water and at sites on steep slopes and on southerly slopes. Context Soil moisture is an essential environmental factor affecting the condition of forests throughout time with high spatial variance. To adapt forests to climate change, assessments of ecological integrity and services in forest management and nature conservation need spatio-temporal estimations of current and future soil moisture. Dynamic modelling of soil moisture even with rather simple models needs numerous data which are often not available for areas of large spatial extent. Aims Therefore, the objectives of this investigation were to (1) spatio-temporally estimate ecological soil moisture with available data covering the whole territory of Germany, (2) to specify these estimates for the regional scale, (3) to statistically analyse temporal trends of modelled soil moisture for the time period 1961–2070 and (4) to map soil moisture changes (drying-out) at both national and regional levels. Methods A fuzzy rule-based model was developed allowing the combination of a pedological and an ecological soil moisture classification. The fuzzy modelling approach was applied for mapping average soil moisture at two spatial scales. Results Soil moisture was modelled and mapped on a scale of 1:500,000 across Germany and regionally specified on a scale of 1:25,000 for the Kellerwald National Park for the time intervals 1961–1990, 1991–2010, 2011–2040 and 2041–2070. The model validation gave a root mean squared error (RMSE) of 0.86 and a coefficient of determination (pseudo R2) of 0.21. Average soil moisture was expected to decline significantly until 2070 concerning soils influenced by ground water and by stagnant water and at sites on steep slopes (> 25%) and on southerly slopes (120–240°). Conclusion The model allows mapping of mean soil moisture at the national and regional scale as shown by the example of Germany and the Kellerwald National Park across observed periods and climate scenarios. It should be combined with available ecological data on forest ecosystem types (Jenssen et al. 2013; Schröder et al. 2015) and tested at the European scale.

The Influence of the Osmotic Potential on Evapotranspiration

“…In Germany, more and longer periods without precipitation are expected in the future [5]. In many studies, an increase in irrigation demand in different parts of the country is identified for the future [6][7][8][9][10][11]. As a result, improving water use efficiency through irrigation management and adopting advanced irrigation technology has become crucial and is considered one of the key adaption measures [9].…”