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

Stefan Nickel,Winfried Schröder

doi:10.1007/s13595-017-0667-5

Abstract

Key messageAverage 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.ContextSoil 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.AimsTherefore, 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.MethodsA 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.ResultsSoil 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°).ConclusionThe 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.

Highlights

Climatic changes are likely to have impacts on structures and functions of ecosystems and, to change biodiversity (Dury et al 2011)
The development of forest soil moisture in areas of large spatial extent such as a national park or the whole territory of Germany could not be estimated. This investigation examined whether fuzzy modelling and mapping of soil moisture for observed periods and climate scenarios could be an alternative for dynamic modelling at the national and regional scale
Process-based dynamic modelling is the method of choice. This investigation enabled to spatio-temporally estimate soil moisture with available data covering the whole territory of Germany, to specify these estimates for the regional scale, to statistically analyse temporal trends of modelled soil moisture for the time period 1961–2070 and to locate soil moisture changes at both national and regional levels

Summary

Introduction

Climatic changes are likely to have impacts on structures and functions of ecosystems and, to change biodiversity (Dury et al 2011). Climate change is and will be possibly characterised by an increase in annual mean temperature and change in rainfall pattern with alternating dry periods and periods of heavy rainfall (Christensen et al 2007; Stocker et al 2013) This raises the question on the availability of water for plants which does depend from the precipitation amount and temperature and on the physical and chemical characteristics of the soils and the depth of soil accessible to the roots (De Cáceres et al 2015). Faced with climate change, ecological assessments of forest ecological integrity and services in forest management and nature conservation need estimations of current and future soil moisture (Calder 2007; Jenssen et al 2013; Pilaš et al 2011; Schröder et al 2015; Schwärtzel et al 2011; Wahren and Feger 2011). This is of particular interest for estimating shifts in forest species composition or adaptation and mitigation strategies such as “climate-adaptive forests” (De Cáceres et al 2015; Jenssen 2009; Lindner et al 2010)

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