Options for increased soil carbon storage and water holding capacity through sustainable agriculture and forestry: modelling results from showcase regions in Austria

Sustainable agriculture and forestry are essential topics under climate change and a potential route for increasing long-term soil and biomass carbon storage, soil water retention capacity, and reducing water and wind erosion risks. This study uses two, geographically and climatologically diverse, showcase regions in Southeastern Austria (the Raab and lower Enns catchment regions) for exploring sustainable whole-system options for climate change adaptation and mitigation under increased hot-dry conditions in agriculture and forestry. We consider options as “sustainable whole-system” that jointly achieve accumulation of soil carbon and robustness of soil water retention capacity, an increase of soil quality, reduction of soil erosion and degradation, reduced compaction, stabilisation of slopes, sustainability and resilience in the soil as well as the agricultural and forest production systems. These options are evaluated using site-level data in the regions together with a carefully combined set of hydrologic, biomass, biogeochemical and ecosystem models. This model setup includes the hydrological model WaSiM, the biogeochemical and ecosystem model DayCent, and the biomass models MiscanFor, SalixFor, and PopFor. Based on dense data of the WegenerNet observing network and further hydrometeorological data, combined with hydrological modelling (WaSiM), the current hydrological disturbance potential in the focus regions is assessed. Furthermore, downscaled IPCC climate change scenarios are used for future projections and combined with WaSiM results. These data are evaluated for increasing heat and drought risks for soils and agricultural and forest production. This work provides the hydrological context for modelling the soil water and carbon storage enhancement options that farming, forestry and land-use practices might apply. A first key study aspect is then the sustainable potential of bioenergy crops. Using the local-scale WegenerNet data combined with site-specific land management data obtained from farmer and forest manager communities and where necessary with soil data from the Harmonized World Soil Database (HWSD), potential yields for bioenergy from lignocellulosic biomass (forest and Miscanthus, willow, and poplar) are modelled using DayCent, MiscanFor, Salix For, and PopFor for representative local areas in the showcase regions. For the second key aspect of this research, DayCent is used at selected data-rich locations, to develop sustainable system options under future climate change scenarios with a focus on different agricultural, forest management, and land-use practices. For comparison, a set of sample agricultural rotations is modelled with DayCent to place the suggested sustainable whole-system options potential of bioenergy crops in context. Furthermore, various agrarian rotation runs are used to determine the potential of changes in the rotation to increase soil carbon storage and enhance water holding capacity in agricultural soils under climate change. Forest management practice runs are used to investigate the possible changes needed for stable forest soils under increasing heat and drought conditions. Sustainable whole-system options for farmers and forest managers are discussed as the primary results from this study part, together with the next steps towards upscaling the results to the country level.