Topsoil structure stability in a restored floodplain: Impacts of fluctuating water levels, soil parameters and ecosystem engineers
Date issued
June 1, 2018
In
Science of the Total Environment
No
639
From page
1610
To page
1622
Abstract
Ecosystem services provided by floodplains are strongly controlled by the structural stability of soils. The development
of a stable structure in floodplain soils is affected by a complex and poorly understood interplay of hydrological,
physico-chemical and biological processes. This paper aims at analysing relations between fluctuating groundwater
levels, soil physico-chemical and biological parameters on soil structure stability in a restored floodplain.Water level
fluctuations in the soil are modelled using a numerical surface-water–groundwater flow model and correlated to
soil physico-chemical parameters and abundances of plants and earthworms. Causal relations andmultiple interactions
between the investigated parameters are tested through structural equation modelling (SEM). Fluctuatingwater levels
in the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil parameters
that in turn determine topsoil structure stability. These relations remain significant for mean annual days of
complete and partial (N25%)water saturation. Ecosystemfunctioning of a restored floodplainmight already be affected
by the fluctuation of groundwater levels alone, and not only through complete flooding by surface water during a flood
period. Surprisingly, abundances of earthworms did not showany relation to other variables in the SEM. These findings
emphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variability
of the topsoil structure stability is thus stronger driven by the influence of fluctuatingwater levels on plants than by the
abundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parameters
and fluctuating water levels and how they affect soil structural stability is of fundamental importance to define management
strategies of near-natural or restored floodplains in the future
of a stable structure in floodplain soils is affected by a complex and poorly understood interplay of hydrological,
physico-chemical and biological processes. This paper aims at analysing relations between fluctuating groundwater
levels, soil physico-chemical and biological parameters on soil structure stability in a restored floodplain.Water level
fluctuations in the soil are modelled using a numerical surface-water–groundwater flow model and correlated to
soil physico-chemical parameters and abundances of plants and earthworms. Causal relations andmultiple interactions
between the investigated parameters are tested through structural equation modelling (SEM). Fluctuatingwater levels
in the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil parameters
that in turn determine topsoil structure stability. These relations remain significant for mean annual days of
complete and partial (N25%)water saturation. Ecosystemfunctioning of a restored floodplainmight already be affected
by the fluctuation of groundwater levels alone, and not only through complete flooding by surface water during a flood
period. Surprisingly, abundances of earthworms did not showany relation to other variables in the SEM. These findings
emphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variability
of the topsoil structure stability is thus stronger driven by the influence of fluctuatingwater levels on plants than by the
abundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parameters
and fluctuating water levels and how they affect soil structural stability is of fundamental importance to define management
strategies of near-natural or restored floodplains in the future
Publication type
journal article
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