Kris Van Looy

A scale-sensitive connectivity analysis to identify ecological networks and conservation value in river networks

Existing methods for connectivity analysis still encounter difficulties in explaining functional relationships between network structure and ecological patterns over larger territories or complex structures like dendritic river networks. We propose a method that addresses the problem of scale and resolution in the connectivity analysis of dendritic network structures, illustrated here for the re-colonization of the French Loire river basin by the European otter. The ecological niche factor approach is applied to infer favourable habitat in the river network based on large scale data of land use and hydro-morphology of river segments for the entire river basin. These analyses identified the stressors to the riparian zone of channel straightening, urbanisation and forest fragmentation as the principal factors explaining otter occurrence. Using this estimate of habitat favourability, we used the Integral Index of Connectivity to quantify habitat availability and connectivity in the dendritic river network. When we calculate the integral index of connectivity over different spatial extents by constraining network distances, the scale-sensitivity of the network’s connectivity emerges. Accounting for high mobility by entering larger network distances in the analysis identifies conservation networks and priorities mainly in downstream parts of the river basin, whereas with smaller network distances, more restricted high quality areas in central and upstream parts are highlighted. The presented approach performed better than distribution modelling approaches in explaining species occurrence over the river network and confirms the crucial aspect of connectivity in otter re-colonization.

Pedotransfer Functions in Earth System Science: Challenges and Perspectives

Soil, through its various functions, plays a vital role in the Earths ecosystems and provides multiple ecosystem services to humanity. Pedotransfer functions (PTFs) are simple to complex knowledge rules that relate available soil information to soil properties and variables that are needed to parameterize soil processes. In this paper, we review the existing PTFs and document the new generation of PTFs developed in the different disciplines of Earth system science. To meet the methodological challenges for a successful application in Earth system modeling, we emphasize that PTF development has to go hand in hand with suitable extrapolation and upscaling techniques such that the PTFs correctly represent the spatial heterogeneity of soils. PTFs should encompass the variability of the estimated soil property or process, in such a way that the estimation of parameters allows for validation and can also confidently provide for extrapolation and upscaling purposes capturing the spatial variation in soils. Most actively pursued recent developments are related to parameterizations of solute transport, heat exchange, soil respiration and organic carbon content, root density and vegetation water uptake. Further challenges are to be addressed in parameterization of soil erosivity and land use change impacts at multiple scales. We argue that a comprehensive set of PTFs can be applied throughout a wide range of disciplines of Earth system science, with emphasis on land surface models. Novel sensing techniques provide a true breakthrough for this, yet further improvements are necessary for methods to deal with uncertainty and to validate applications at global scale.

Analyzing riparian zone ecosystem services bundles to instruct river management

ABSTRACT The ecosystem service framework is now well accepted for focussing management strategies to preserve and restore ecosystems. Its implementation remains challenging, however, due to the environment’s complexity and dynamics that interfere with ecosystems’ ability to provide the services. Here, we question whether we can show where and how to intervene in riparian corridors to restore specific ecosystem services without endangering others. Specific hypotheses in this context are for the spatial aggregation of ecosystem services delivered by riparian corridors with respect to naturalness (1), to the existence of bundles of ecosystem services (2), and finally for the scale sensitivity of this congruence (3). Within a Geographical Information System framework, we analyse the capacity of riparian corridors to provide ecosystem services over three river basins in the Bresse region (France) based on high-resolution data of the riparian corridor hydromorphology and land use. Specifically, we compare the capacity to provide two services: in-stream water purification and riparian retention of nutrients that are critical goals for river management and rehabilitation strategies. We observe little spatial association and high spatial variability for the two emphasized ecosystem services. Surprisingly, no congruence of ecosystem services with riparian corridor naturalness is present. The absence of associations between ecosystem services and their spatial variability will oblige environmental managers to identify underpinning environmental processes and patterns at local scales. In conclusion, we plead for fine-grained multifunctional assessment of ecosystems’ capacity to deliver services, especially in environments such as river corridors that exhibit high environmental heterogeneity. EDITED BY Neville Crossman

Are generalist and specialist species influenced differently by anthropogenic stressors and physical environment of riparian corridors

Abstract The well-documented re-colonisation of the French large river basins of Loire and Rhone by European otter and beaver allowed the analysis of explanatory factors and threats to species movement in the river corridor. To what extent anthropogenic disturbance of the riparian zone influences the corridor functioning is a central question in the understanding of ecological networks and the definition of restoration goals for river networks. The generalist or specialist nature of target species might be determining for the responses to habitat quality and barriers in the riparian corridor. Detailed datasets of land use, human stressors and hydro-morphological characteristics of river segments for the entire river basins allowed identifying the habitat requirements of the two species for the riparian zone. The identified critical factors were entered in a network analysis based on the ecological niche factor approach. Significant responses to riparian corridor quality for forest cover, alterations of channel straightening and urbanisation and infrastructure in the riparian zone are observed for both species, so they may well serve as indicators for corridor functioning. The hypothesis for generalists being less sensitive to human disturbance was withdrawn, since the otter as generalist species responded strongest to hydro-morphological alterations and human presence in general. The beaver responded the strongest to the physical environment as expected for this specialist species. The difference in responses for generalist and specialist species is clearly present and the two species have a strong complementary indicator value. The interpretation of the network analysis outcomes stresses the need for an estimation of ecological requirements of more species in the evaluation of riparian corridor functioning and in conservation planning.