A dynamic riparian forest structure model for predicting large wood inputs to meandering rivers. Issue 15 (30th September 2021)

• Record Type: Journal Article
• Authors: Stella, John C.; Kui, Li; Golet, Gregory H.; Poulsen, Frank
• Is Part Of: Earth surface processes and landforms. Volume 46:Issue 15(2021)
• Page Start: 3175
• Page End: 3193
• Publication Date: 2021-09-30
• Subjects: carbon sequestration -- ecological chronosequence -- forest succession -- large wood recruitment -- meandering alluvial river -- riparian stand structure -- river restoration -- riverine habitat -- Weibull tree diameter distribution; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.5229
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Fluvial processes strongly influence riparian forests through rapid and predictable shifts in dominant species, tree density and size that occur in the decades following large floods. Modelling riparian forest characteristics based on the age and evolution of floodplains is useful in predicting ecosystem functions that depend on the size and density of trees, including large wood delivered to river channels, forest biomass and habitat quality. We developed a dynamic model of riparian forest structure that predicts changes in tree size and density using floodplain age derived from air photos and historical maps. Using field data and a riparian forest chronosequence for the 160‐km middle reach of the Sacramento River (California, USA), we fit Weibull diameter distributions with time‐varying parameters to the empirical data. Species were stratified into early and late successional groups, each with time‐varying functions of tree density and diameter distributions. From these, we modelled how the number and size of trees in a stand changed throughout forest succession, and evaluated the goodness‐of‐fit of model predictions. Model outputs for the early successional group, composed primarily of cottonwoods and willows, accounted for most of the stand basal area and large trees >10 cm DBH for the first 50 years. Post‐pioneer species with slower growth had initially low densities that increased slowly from the time of floodplain creation. Within the first 100 years, early successional trees contributed the most large wood that could influence fluvial processes, carbon storage, and instream habitat. We applied the model to evaluate the potential large wood inputs to the middle Sacramento River under a range of historical bank migration rates. Going forward, this modelling approach can be used to predict how riparian forest structure and other ecosystem benefits such as carbon sequestration and habitat quality respond to different river management and restoration actions. Abstract : We developed a riparian forest structure model that predicts shifts in tree size and density as a function of floodplain age on dynamic alluvial rivers. The model uses a Weibull distribution with time‐dependent parameters and was calibrated with field inventory data from the middle Sacramento River (California, USA). We generated predictions of large wood inputs based on historical bank retreat rates. Other applications include modelling the response of riparian forest biomass and habitat to different river management and restoration actions.