See all ›
55 CitationsRevised instream flow regulation enables cottonwood recruitment along the St. Mary River, Alberta, Canada
Abstract
Following the completion of the St. Mary Dam in 1951, the riparian cottonwood populations downstream collapsed. Previous studies revealed a lack of recruitment of new trees after damming, probably due to insufficient summer flows and abrupt flow declines in the late spring. Changes to the operations pattern of the St. Mary Dam began in 1991 when minimum flow tripled from 0.93 to 2.75 m3/s. 'Ramping' flows were imposed beginning in 1994, whereby flow recession was gradual with a target stage decline of 4 cm/d. In the present study, we investigated the effects of these changes of instream flow regulation on cottonwood seedling recruitment. Heavy rain produced a 1-in-50-year flood event in early June 1995. In contrast to post-dam floods in 1964 and 1975, the regulated, gradual flow recession after the 1995 flood resulted in extensive recruitment of cottonwoods (Populus angustifolia James, P. balsamifera subsp. trichocarpa T. & G. ex Hook, and a few P. deltoides Bartr. ex Marshall) and willows (primarily Salix exigua Nutt.). Many seedlings were established in the flood year of 1995 and additional seedlings were recruited in 1996 and thereafter. Successful seedlings were generally established at elevations from 80 to 120 cm above the late summer stream stage. Typical seedling densities along the final segment of the river at the end of 1995 were 200/m2. By 1999, seedling densities had decreased by about 95% but seedling growth resulted in almost complete leaf area cover. Seedlings were sparse in areas that lacked parental trees, suggesting that seed source was limiting in those zones. model and provides a promising case study regarding instream flow regulation for riparian restoration.
Full-text (PDF)
Available from: Stewart Rood, Nov 16, 2015
- CitationsCitations55
- ReferencesReferences0
- "Durch intensive Forschung im semiariden Nordwesten Amerikas (Mahoney & Rood, 1998; Rood, 2000Mahoney & Rood, 1998; Rood et al., 2003) in 5-10 Jahresintervallen (Mahoney & Rood, 1993) beziehungsweise in einem Intervall von 3-10 Jahren mit mittleren bis hohen Frühjahrshochwässern (Cordes et al., 1997; Mahoney & Rood, 1998; Scott et al., 1996den Hauptfluss zur Schädigung der Konkurrenzvegetation nicht möglich ist. Hier blieben zwei Möglichkeiten: ein kleines ökologisches Fließgewässer durch die Auenbereiche künstlich schaffen und dieses dann entsprechend der Recruitment Box gezielt steuern und auch aufstauen. "
[Show abstract] [Hide abstract] ABSTRACT: Der Beitrag zu einem aktuellen gleichnamigen Forschungsprojekt diskutiert einen Konflikt innerhalb der Nachhaltigkeitssäule „Ökologie“. So stehen Wasserkraft werke im Spannungsfeld zwischen der Nutzung des fließenden Wassers als CO2-neutrale, regenerative und grundlastfähige Energiequelle einerseits und den negativen Auswirkungen auf den Lebensraum aus dem Fluss und seinem natürlichen Überschwemmungsgebiet, der Aue, andererseits. Speziell betrachtet werden die Auswirkungen auf den stark bedrohten Lebensraumtyp der Weichholzaue. Nach einer Zusammenfassung der bereits bekannten Einflussfaktoren werden die im Projekt herausgearbeiteten Forschungsansätze zur Förderung der Keimungs- und Etablierungsbedingungen von Silberweidenbeständen vorgestellt. Dendrochronologische Untersuchungen in Kombination mit Analysen von Abflussdaten sollen in der Entwicklung einer Recruitment Box nach dem Vorbild von Forschungen aus dem Nordwesten Amerikas münden. Ergänzt wird dieser Ansatz durch die Evaluierung des Einflusses des Neophyten Impatiens glandulifera auf die Verjüngung von Silberweiden.- "In Alberta, beaver cutting of the decrepit narrowleaf cottonwood (P. angustifolia James) population downstream from the St. Mary Dam, hindered attempts at cottonwood restoration (Rood and Mahoney 2000 "
[Show abstract] [Hide abstract] ABSTRACT: We investigated interactions between river regulation, riparian black cottonwoods (Populus trichocarpa) and beavers (Castor canadensis) with a paired comparison between the free-flowing Lardeau River and regulated lower Duncan River in western Canada. Cottonwood saplings occurred more broadly along Lardeau River transects (63 % vs. 38 %) and with increased density. Beavers preferred cottonwoods over other shrubs and cutting was more intense (36 % vs. 7 % of stems cut) along the regulated Duncan River. Beaver cutting occurred in wider bands (25 m vs. 11 m from river) along the Duncan, and there was also evidence for increased cutting of a less-favored alternate, alder (Alnus incana), while willows (Salix spp.) were substantially cut along both rivers. River regulation has apparently reduced cottonwood recruitment along the Duncan River and regulation may also increase beaver accessibility to saplings since higher river levels in late summer and autumn may promote inland access. These ecosystem alterations may thus create an imbalance between bottom-up cottonwood recruitment versus top-down mortality. We overview some of the ecological interactions in riparian woodlands in a schematic model recognizing river flow regime, sediment patterns and bank forms, and other riparian vegetation as key factors influencing cottonwoods and beavers.- "A synoptic view of these restoration strategies, and especially an assessment of how to evaluate their success, is still lacking despite major investments annually worldwide for restoring riparian habitats. As pointed out by Weisberg et al. (2013), many of the first studies on the ecology of riparian vegetation focused on understanding the decline of Salicaceae gallery forests and the mechanisms underlying their regeneration (Johnson et al., 1976; Stromberg and Patten, 1991; Stromberg, 1993; Rood and Heinz-Milne, 1989; Rood and Mahoney, 1990; Mahoney and Rood, 1998); the first restoration trials that received academic attention often equated riparian restoration with restoration of Salicaceae forests (e.g., Friedman et al., 1995; Roelle and Gladwin, 1999; Rood and Mahoney, 2000; Rood et al., 2003). With a significant and growing body of literature, restoration of riparian vegetation nowadays goes beyond restoration of Salicaceae forests. "
[Show abstract] [Hide abstract] ABSTRACT: We examined how restoration of riparian vegetation has been implemented and evaluated in the scientific literature during the past 25 years. A total of 169 papers were read systematically to extract information about the following: 1) restoration strategies applied, 2) scale of monitoring and use of reference sites, 3) metrics used for evaluation, and 4) drivers of success. Hydro-geomorphic approaches (e.g., dam operations, controlled floods, landform reconfiguration) were the most frequent, followed by active plant introduction, exotic species control, natural floodplain conversion and grazing and herbivory control. Our review revealed noteworthy limitations in the spatio-temporal approaches chosen for evaluation. Evaluations were mostly from one single project and frequently ignored the multi-dimensional nature of rivers: landscape spatial patterns were rarely assessed, and most projects were assessed locally (i.e., ≤meander scale). Monitoring rarely lasted for more than six years and the projects evaluated were usually not more than six years old. The impact of the restoration was most often (43%) assessed by tracking change over time rather than by comparing restored sites to unrestored and reference sites (12%), and few projects (30%) did both. Among the ways which restoration success was evaluated, vegetation structure (e.g., abundance, density, etc.) was assessed more often (152 papers) than vegetation processes (e.g., biomass accumulation, survival, etc.) (112 papers) and vegetation diversity (78 papers). Success was attributed to hydro-geomorphic factors in 63% of the projects. Future evaluations would benefit from incorporating emerging concepts in ecology such as functional traits to assess recovery of functionality, more rigorous experimental designs, enhanced comparisons among projects, longer term monitoring and reporting failure. Copyright © 2015 Elsevier Ltd. All rights reserved.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.
This publication is from a journal that may support self archiving.
Learn more