Growth and Wood Trait Relationships of Alnus glutinosa in Peatland Forest Stands With Contrasting Water Regimes

Human-driven peatland drainage has occurred in Europe for centuries, causing habitat degradation and leading to the emission of greenhouse gases. As such, in the last decades, there has been an increase in policies aiming at restoring these habitats through rewetting. Alder (Alnus glutinosa L.) is a widespread species in temperate forest peatlands with a seemingly high waterlogging tolerance. Yet, little is known about its specific response in growth and wood traits relevant for tree functioning when dealing with changing water table levels. In this study, we investigated the effects of rewetting and extreme flooding on alder growth and wood traits in a peatland forest in northern Germany. We took increment cores from several trees at a drained and a rewetted stand and analyzed changes in ring width, wood density, and xylem anatomical traits related to the hydraulic functioning, growth, and mechanical support for the period 1994–2018. This period included both the rewetting action and an extreme flooding event. We additionally used climate-growth and climate-density correlations to identify the stand-specific responses to climatic conditions. Our results showed that alder growth declined after an extreme flooding in the rewetted stand, whereas the opposite occurred in the drained stand. These changes were accompanied by changes in wood traits related to growth (i.e., number of vessels), but not in wood density and hydraulic-related traits. We found poor climate-growth and climate-density correlations, indicating that water table fluctuations have a stronger effect than climate on alder growth. Our results show detrimental effects on the growth of sudden water table changes leading to permanent waterlogging, but little implications for its wood density and hydraulic architecture. Rewetting actions should thus account for the loss of carbon allocation into wood and ensure suitable conditions for alder growth in temperate peatland forests.

Field Jet Erosion Tests on Benbrook Dam, Texas

This report summarizes the results of eight field Jet Erosion Tests (JETs) performed on Benbrook Dam, TX. The results from these tests will be used by the U.S. Army Corps of Engineers, Fort Worth District, in assessments of the erosion resistance of the Benbrook Dam with regards to possible overtopping by extreme flooding. The JETs were performed at four different locations, i.e., two locations at the lowest crest elevation and two locations at the mid-slope face of the downstream embankment. Variations in estimated critical hydraulic shear stress and erosion rate values may have been caused by differences in soil composition, i.e., when the material changed from silt/sand to clay. The resulting values of the Erodibility Coefficient, Kd, and Critical Stress, τc, are very useful information in assessing the stability of Benbrook Dam during an overtopping event. Because of the observed natural variability of the materials, combining the erosion parameters presented in this report with the drilling logs and local geology will be imperative for assessing erosion-related failure modes of Benbrook Dam.

Community Disaster Recovery

Disasters can serve as focusing events that increase agenda attention related to issues of disaster response, recovery, and preparedness. Increased agenda attention can lead to policy changes and organisational learning. The degree and type of learning that occurs within a government organization after a disaster may matter to policy outcomes related to individual, household, and community-level risks and resilience. Local governments are the first line of disaster response but also bear the burden of performing long-term disaster recovery and planning for future events. Crow and Albright present the first framework for understanding if, how, and to what effect communities and local governments learn after a disaster strikes. Drawing from analyses conducted over a five-year period following extreme flooding in Colorado, USA, Community Disaster Recovery: Moving from Vulnerability to Resilience presents a framework of community-level learning after disaster and the factors that catalyse policy change towards resilience.

Flooding Hazard and Vulnerability. An Interdisciplinary Experimental Approach for the Study of the 2016 West Virginia Floods

The hydrosocial (HS) and social-hydro (SH) frameworks each attempt to understand the complexity of water and society, but they have emerged from historically disparate fields with distinctly different goals as well as methodological and epistemological standpoints. This paper encapsulates the shared experiences of two human geographers and two hydrologists studying hazard and vulnerability in two communities impacted by extreme flooding in West Virginia in 2016. We add to the limited examples of scientists working across epistemologies to improve the understanding of water-societal relations. In so doing, we also contribute to broader discussions of water justice. We outline an experimental approach connecting hydrosocial and social-hydro frameworks to study flood hazard and vulnerability. Within our conceptualization, we set forth that while social and hydrological factors can be presented as purely anthropogenic or geophysical, respectively, their intersection is the crux to investigate. The relationships between variables of both major categories can help us understand how the social and biophysical systems are interrelated. We depart from 21 semi structured interviews and a secondary analysis of local biophysical factors to develop a model that could show the relations between social and biophysical factors. Linking these factors is crucial step toward integration of SH and HS approaches to create a more comprehensive understanding of water-human relations. These studies can inform policymakers by highlighting where negative connections can be remedied and positive connections can be fostered to emphasize water justice.