Emergent geomorphic–vegetation interactions on a subalpine alluvial fan

Abstract

Following perturbation, an ecosystem (flora, fauna, soil) should evolve as a function of time at a rate conditioned by external variables (relief, climate, geology). More recently, biogeomorphologists have focused upon the notion of co‐development of geomorphic processes with ecosystems over very short through to very long (evolutionary) timescales. Alpine environments have been a particular focus of this co‐development. However, work in this field has tended to adopt a simplified view of the relationship between perturbation and succession, including: how the landform and ecosystem itself conditions the impact of a perturbation to create a complex spatial response impact; and how perturbations are not simply ecosystem destroyers but can be a significant source of ecosystem resources. What this means is that at the within landform scale, there may well be a complex and dynamic topographic and sedimentological template that co‐develops with soil, flora and fauna. Here, we present and test a conceptual model of this template for a subalpine alluvial fan. We combine detailed floristic inventory with soil inventory, determination of edaphic variables and analysis of historical aerial imagery. Spatial variation in the probability of perturbation of sites on the fan surface was associated with down fan variability in the across‐fan distribution of fan ages, fan surface channel characteristics and fan surface sedimentology. Floristic survey confirmed that these edaphic factors distinguished site floristic richness and plant communities up until the point that the soil–vegetation system was sufficiently developed to sustain plant communities regardless of edaphic conditions. Thus, the primary explanatory variable was the estimated age of each site, which could be tied back into perturbation history and its spatial expression due to the geometry of the fan: distinct plant communities were emergent both across fan and down fan, a distribution maintained by the way in which the fan dissipates potentially perturbing events. Copyright © 2015 John Wiley & Sons, Ltd.

Influence of microclimate and geomorphological factors on alpine vegetation in the Western Swiss Alps

“…Furthermore, in addition to water, nutrients availability and the microclimate, plant colonization also depends on surface stability (Baroni et al, 2007;Gentili et al, 2010;Baroni et al, 2013). Such a two-way linkage was confirmed by other authors studying the interactions between subalpine alluvial fans and floristic diversity (Lane et al, 2016) and between sediment reworking on a lateral Little Ice Age (LIA) moraine and bioengineering species (Eichel et al, 2016;Eichel et al, 2017).…”

“…Future research should investigate the effects of soil texture, nutrient and pH, as done by Dubuis et al (2013), and couple these results with geomorphological assessment in high alpine sites, as those presented here. Additionally, it would be important to work with longer ground surface temperature series, to obtain a more complete overview of the factors affecting vegetation in alpine ecosystems, and to take in consideration a biogeomorphic approach, because plant communities and geomorphic disturbance regime could be co-dependent as demonstrated by some authors (e.g., Corenblit and Steiger, 2009;Eichel et al, 2016 andLane et al, 2016).…”

“…elevation 3051ma.s.l.) and oriented SW-NE, which has been extensively studied in geomorphological and biological fields (e.g., Lambiel et al, 2009;Vittoz and Gmür, 2009;Lane et al, 2016;Thornton et al, 2018).…”

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

“…The cyclicity of the system means that, instead of contrasting physical and biotic controls on geomorphology and sediment flux (e.g. Tal and Paola, ; Gurnell, ), we rather have to consider the control of vegetation as part of a longer‐term cycle, in which the dominance of biotic and abiotic processes not only switch, but depend on each other (Lane et al , ; Larsen et al , ). This adds a new and contrasting perspective to earlier studies on the longer‐term evolution along the middle reaches of Top End river systems that argued for a dominance of either climate or sea‐level control on shifts between aggradational and degradational episodes over Holocene timescales (Roberts, ; Nanson et al , ).…”

Biotic drivers of river and floodplain geomorphology – New molecular methods for assessing present‐day and past biota

“…Woody debris changes river‐floodplain connectivity and enhances flow complexity (Wohl et al ., ; Wohl and Beckman, ). However, recent studies have indicated that the control of vegetation might be part of a longer‐term cycle, in which the dominance of biotic and abiotic processes not only switch, but depend on each other (Lane et al ., ; Larsen et al ., ). Biota and abiotic processes may have co‐evolved over both longer and shorter timescales (Corenblit et al ., ).…”