The integration of water resources use and sustainable ecosystem management is a complex challenge, especially for freshwater systems in highly utilized landscapes like floodplains.
In order to achieve “good ecological status”, engineered river systems undergo restoration to a more natural state in which their evolution as dictated by flooding and other natural perturbations, at least within a defined corridor. Quantifying the effectiveness of restoration schemes, in particular with respect to ecosystem functioning, biodiversity and water quality was necessary.
A sound understanding of the underlying physical, biogeochemical and ecological processes was and is still needed to prevent restoration projects operating as large-scale trial-and-error field experiments.
River restoration, in the past years, has become an essential tool to achieve “good ecological status” of water courses as required by both European and Swiss legislations. Consequently, and although the number of restoration projects has increased lately, a scientific understanding of the underlying principles determining how hydromorphological variability in restored corridors of rivers relates to ecosystem functioning, to biodiversity and to water quality is still limited.
The objective of the RECORD project is to increase mechanistic understanding of coupled hydrological and ecological processes in near-river corridors. For this purpose, the project will:
- instrument a restored and a channelized section of Swiss River Thur as large-scale field experimental sites, where the influence of various variables over (ground)water quality, ecosystem functioning and biodeiversity will be evaluated;
- perform controlled experiments at the field site and in the lab;
- develop process-based models of coupled hydrological, biogeochemical and ecological processes, facilitating the transfer to other river systems undergoing restoration.
Several research groups within Switzerland’s ETH Domain have combined in a comprehensive field project aimed at unravelling the various interacting processes influencing the ecological functioning of River Thur, which is actively undergoing restoration. ECOL’s involvement centres on model development and application to the field site. We are involved in both in catchment and site scale hydrological modelling, as well as detailed flow and transport modelling of the subsurface. In addition to improving understanding of factors that influence restoration, the predictive capabilities of such models will facilitate knowledge transfer to other river systems where societal and ecological demands need to be balanced.
Record activities focus on River Thur, the largest river in Switzerland without a natural or artificial reservoir. The revitalization of River Thur is the largest ongoing project in Switzerland.
The main field site is the restored section at Niederneunforn (TG) and Altikon (ZH). At this site, the project will:
- observe the dynamics of hydraulics, morphology, and vegetation by automated cameras;
- assess the distribution of sediments and their associated properties by multiple geophysical surveys;
- install well transects to identify the origin, travel time and chemical composition of alluvial groundwater;
- analyze oxygen, carbon, and nutrient cycling along flow paths;
- perform ecological surveys;
- monitor the root zone in various vegetation patches;
- measure hydrological (e.g. (ground)water table, soil moisture, sap flow) and meteorological quantities
Process-based modelling of water flow and biogeochemical transformations along transects
Detailed measurements of water and chemical (water/soil/plant) status along groundwater flow lines will be undertaken within RECORD. These data will be used within physically based transport modelling to quantify the main fluxes of water and nutrients at the site, as well as to assess conditions for ecological functioning. Natural porous media exhibit variability at multiple scales, both in properties of the soil matrix and in the processes occurring within the matrix, as is expected to ve evident from the detailed transect measurements from the R. Thur site. The modelling effort will provide the basis to quantify this variability and complexity at the transect scale and to generate appropriate mass flux information for use at the larger scales.
- Batlle-Aguilar, J., Brovelli, A., Porporato, A. and D.A. Barry. (2009). Modelling carbon and nitrogen turnover in variably saturated soils. European Geosciences Union (EGU), General Assembly. Vol. 11, Abstract EGU2009-8093-1. Vienna (Austria). (Download abstract and poster).
- Batlle-Aguilar, J., Brovelli, A., Porporato, A. and D.A. Barry. (2009). Modelling of mechanisms affecting nitrogen and carbon cycles in soils subject to land use change. 7th Swiss Geosciences Meeting. Neuchâtel ( Switzerland). (Download extended abstract and oral presentation).
- Batlle-Aguilar, J., Brovelli, A., Porporato, A. and D.A. Barry. (2009). Carbon, oxygen and nitrogen dynamics in a soil profile: Model development and application. Eos. Trans. AGU, 90(52). Fall Meet. Suppl., Abstract H33D-0907. San Francisco, CA (EUA). (Download abstract and poster).
- Batlle-Aguilar, J., Brovelli, A. and D.A. Barry. Carbon and nitrogen dynamics in a soil profile: Model development. European Geosciences Union (EGU), General Assembly. Vol. 12, Abstract EGU2010-5626-1. Vienna (Austria). (Download abstract and oral presentation).
- Brovelli, A., Batlle-Aguilar, J., Luster, J., Shrestha, J., Huber, B., Niklaus, P. and D.A. Barry. Carbon and nitrogen dynamics in a soil profile: Model insights and application to a restored Swiss riparian area. European Geosciences Union (EGU), General Assembly. Vol. 12, Abstract EGU2010-5630-1. Vienna (Austria). (Download abstract and poster).
Modelling of mechanisms affecting nitrogen and carbon cycles in soils undergoing restoration: Overview and model application
Batlle-Aguilar, J., Brovelli, A., Porporato, A. and D.A. Barry
Agronomy for Sustainable Development DOI: 10.105/agro/2010007
Forested soils are being increasingly transformed to agricultural fields in response to growing demands for food crop. This modification of the land use is known to result in deterioration of soil properties, in particular its fertility. To reduce the impact of the human activities and mitigate their effects on the soil, it is important to understand the factors responsible for the modification of soil properties. In this paper we reviewed the principal processes affecting soil quality during land use changes, focusing in particular on the effect of soil moisture dynamics on soil carbon (C) and nitrogen (N) cycles. Both physical and biological processes, including degradation of litter and humus, and soil moisture evolution at the diurnal and seasonal time scales were considered, highlighting the impact of hydroclimatic variability on nutrient turnover along with the consequences of land use changes from forest to agricultural soil and vice-versa.
In order to identify to what extent different models are suitable for long-term predictions of soil turnover, and to understand whether some simulators are more suited to specific environmental conditions or ecosystems, we enumerated the principal features of the most popular existing models dealing with C and N turnover. Among these models, we considered in detail a mechanistic compartment-based model. To show the capabilities of the model and to demonstrate how it can be used as a predictive tool to forecast the effects of land use changes on C and N dynamics, four different scenarios were studied, intertwining two different climate conditions (with and without seasonality) with two contrasting soils having physical properties that are representative of forest and agricultural soils. The model incorporates synthetic time series of stochastic precipitation, and therefore soil moisture evolution through time. Our main findings in simulating these scenarios are that 1) forest soils have higher concentrations of C and N than agricultural soils as a result of higher litter decomposition; 2) high frequency changes in water saturations under seasonal climate scenarios are commensurate with C and N concentrations in agricultural soils; and 3) due to their different physical properties, forest soils attenuate the seasonal climate-induced frequency changes in water saturation, with accompanying changes in C and N concentrations. The model was shown to be capable of simulating the long term effects of modified physical properties of agricultural soils, being thus a promising tool to predict future consequences of practices affecting sustainable agriculture, such as tillage (leading to erosion), ploughing, harvesting, irrigation and fertilization, leading to C and N turnover changes and in consequence, in terms of agriculture production.
Main Related Results
We developed and applied the mechanistic model of soil carbon and nitrogen turnover proposed by Porporato et al. (Adv. Water Res., 26: 45-58, 2003) in four different scenarios intertwining two different climate conditions (with and without the effect of seasonality) and characteristic physical properties. Obtaining results were encouraging, because the model is able to reproduce expected differences in soil carbon and nitrogen concentrations in the different soils, as well as decomposition rates and nitrate uptake and leaching to the aquifer (Figures 1 and 2).
(click on figures to download them in a high resolution)
Figure 1. Soil organic carbon (SOC) concentrations (litter, humus and biomass pools) and inorganic nitrogen (ammonium and nitrate pools) in agricultural and forest soils under seasonal climate.
Figure 2. Litter carbon decomposition, net nitrogen mineralization, and nitrate uptake and leaching in agricultural and forest soils under seasonal climate.