In this study, we assessed the potential for bioenergy production of Low-Input High-Diversity (LIHD) systems in temperate West-European conservation areas. A wide range of seminatural ecosystems (wet and dry grasslands, marshes, tall-herb vegetation and heathlands) was sampled. Because LIHD biomass is often scattered and discontinuously available, we only considered the potential for anaerobic digestion and combustion. Both technologies are suitable for decentralized biomass utilization. The gross energy yield showed a promising range between 46-277 GJ per hectare per mowing cycle (MC). The energy efficiency of the anaerobic digestion process was rather low (10-30%) with a methane energy yield of 5.5-35.5 GJ ha À1 MC À1, experimentally determined by batch digestion tests. The water content, functional group composition and biochemical composition (hemicellulose, cellulose, lignin and Kjeldahl nitrogen) of the biomass were analyzed to assess the suitability of different valorization pathways. On the basis of the results, we were able to propose recommendations regarding the appropriate conversion techniques. Biomass from plant communities with 'late' harvest dates (August-October) or a high fraction of woody species like heathland and dune slacks, is best valorized through combustion, while herbaceous biomass of 'early' harvested grasslands (June-July) and tall-herb vegetation can better be digested. The main advantages of the production of bioenergy from LIHD biomass originating from conservation management are the minimization of the competition with food production and its potential to reconcile renewable energy policies and biodiversity goals.

Abstract:Remote sensing can provide good alternatives for traditional in situ water status measurements in orchard crops, such as stem water potential (Ψ stem ). However, the heterogeneity of these cropping systems causes significant differences with regards to remote sensing products within one orchard and between orchards. In this study, robust spectral indicators of Ψ stem were sought after, independent of sensor viewing geometry, orchard architecture and management. To this end, Ψ stem was monitored throughout three consecutive growing seasons in (deficit) irrigated and rainfed pear orchards and related to spectral observations of leaves, canopies and WorldView-2 imagery. On a leaf and canopy level, high correlations were observed between the shortwave infrared reflectance and in situ measured Ψ stem . Additionally, for canopy measurements, visible and near-infrared wavelengths (R 530 /R 600 , R 530 /R 700 and R 720 /R 800 ) showed significant correlations. Therefore, the Red-edge Normalized Difference Vegetation Index (ReNDVI) was applied on fully sunlit satellite imagery and found strongly related with Ψ stem (R 2 = 0.47; RMSE = 0.36 MPa),undoubtedly showing the potential of WorldView-2 to monitor water stress in pear orchards. The relationship between ReNDVI and Ψ stem was independent of management, irrigation setup, phenology and environmental conditions. In addition, results showed that this relation was also independent of off-nadir viewing angle and almost independent of viewing geometry, as the correlation decreased after the inclusion of fully shaded scenes. OPEN ACCESSRemote Sens. 2013, 5 6648With further research focusing on issues related to viewing geometry and shadows, high spatial water status monitoring with space borne remote sensing is achievable.

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