Does stream flow structure woody riparian vegetation in subtropical catchments?

Abstract

The primary objective of this study was to test the relevance of hydrological classification and class differences to the characteristics of woody riparian vegetation in a subtropical landscape in Queensland, Australia. We followed classification procedures of the environmental flow framework ELOHA – Ecological Limits of Hydrologic Alteration. Riparian surveys at 44 sites distributed across five flow classes recorded 191 woody riparian species and 15, 500 individuals. There were differences among flow classes for riparian species richness, total abundance, and abundance of regenerating native trees and shrubs. There were also significant class differences in the occurrence of three common tree species, and 21 indicator species (mostly native taxa) further distinguished the vegetation characteristics of each flow class. We investigated the influence of key drivers of riparian vegetation structure (climate, depth to water table, stream‐specific power, substrate type, degree of hydrologic alteration, and land use) on riparian vegetation. Patterns were explained largely by climate, particularly annual rainfall and temperature. Strong covarying drivers (hydrology and climate) prevented us from isolating the independent influences of these drivers on riparian assemblage structure. The prevalence of species considered typically rheophytic in some flow classes implies a more substantial role for flow in these classes but needs further testing. No relationships were found between land use and riparian vegetation composition and structure. This study demonstrates the relevance of flow classification to the structure of riparian vegetation in a subtropical landscape, and the influence of covarying drivers on riparian patterns. Management of environmental flows to influence riparian vegetation assemblages would likely have most potential in sites dominated by rheophytic species where hydrological influences override other controls. In contrast, where vegetation assemblages are dominated by a diverse array of typical rainforest species, and other factors including broad‐scale climatic gradients and topographic variables have greater influence than hydrology, riparian vegetation is likely to be less responsive to environmental flow management.

Fish trophic guild responses to damming: Variations in abundance and biomass

“…In fact, the contributions of flooded vegetation to ichthyofauna enhance the diet within this guild for a short period until decomposition. Subsequently, the resource becomes scarcer than it is in an undammed river due to the smaller interface with riparian vegetation, which provides fruits and seeds (Agostinho et al, , b; Hahn & Fugi, ), or due to frequent fluctuations in water levels resulting from reservoir operation, which limits the development of vegetation that prior to damming was seasonally flooded (Agostinho, Pelicice, & Gomes, ; James et al, ; Luz‐Agostinho, Bini, Fugi, Agostinho, & Júlio, ; Pusey & Arthingthon, ). However, the intensive removal of vegetation near the dam before damming seems to be the determinant in the reduction of herbivore abundance and biomass.…”

Recent advances in environmental flows science and water management—Innovation in the Anthropocene

“…Applications of the ELOHA framework and innovations building on its architecture are increasing. It has been applied in the U.S.A. (Buchanan, Moltz, Haywood, Palmer, & Griggs, ; Kendy et al., ; Reidy Liermann et al., ; Sanderson et al., ), Spain (Belmar, Velasco, & Martinez‐Capel, ), China (Zhang et al., ), Australia (Arthington et al., ; James, Mackay, Arthington, & Capon, ; Mackay, Arthington, & James, ) and Africa (O'Brien et al., ). Development of the “hydrologic foundation” has dominated these applications and prompted new approaches to accurately simulate flows and estimate flow metrics at many ungauged locations across broad geographical regions.…”

“…McManamay & Frimpong, ; Mims & Olden, , ; Rolls & Sternberg, ). Further development of trait groups as the biological units of response to flow has been recommended to strengthen mechanistic flow–ecological models derived from ELOHA studies (James et al., ; Rolls & Arthington, ) and other broad‐scale investigations (Frimpong & Angermeier, ; Hain et al., ).…”

“…Bunn, ). Novel research, modelling and systematic spatial analysis will also help with optimisation of management strategies to restore river and riparian ecosystems (Hain et al., ; Hermoso et al., ; James et al., ). Account for extreme events and non‐stationarity: Establishing temporally robust environmental water targets is a challenge in complex, variable and changing water systems. This is particularly true when considering multiple temporal scales, including the role of extreme events and issues of non‐stationarity associated with lagged effects from past and present changing land and water use practices and interactions with the effects of climate change (Thompson et al., ).…”

Turquoise is the new green: Restoring and enhancing riparian function in the Anthropocene

“…The imperative to protect and restore riparian ecosystems is critical in human‐dominated landscapes where riparian vegetation often retains the last remnants of native vegetation, or indeed any structurally significant vegetation, within a matrix of urban, agricultural and industrial land uses (James et al . 2016a). Additionally, riparian restoration is widely recognised as increasingly important to the resilience and adaptive capacity of both human and ecological systems under climate change because of their irreplaceable ecological functions and services (Palmer et al .…”