Vegetation-precipitation controls on Central Andean topography

Abstract

Climatic controls on fluvial landscapes are commonly characterized in terms of mean annual precipitation. However, physical erosion processes are driven by extreme events and are therefore more directly related to the intensity, duration, and frequency of individual rainfall events. Climate also influences erosional processes indirectly by controlling vegetation. In this study, we explore how interdependent climate and vegetation properties affect landscape morphology at the scale of the Andean orogen. The mean intensity, duration, and frequency of precipitation events are derived from the TRMM 3B42v7 product. Relationships between mean hillslope gradients and precipitation event metrics, mean annual precipitation, vegetation, and bedrock lithology in the central Andes are examined by correlation analyses and multiple linear regression. Our results indicate that mean hillslope gradient correlates most strongly with percent vegetation cover (r = 0.56). Where vegetation cover is less than 95%, mean hillslope gradients increase with mean annual precipitation (r = 0.60) and vegetation cover (r = 0.69). Where vegetation cover is dense (>95%), mean hillslope gradients increase with increasing elevation (r = 0.74), decreasing inter-storm duration (r = À0.69), and decreasing precipitation intensity by~0.5°/(mm d À1 ) (r = À0.56). Thus, we conclude that at the orogen scale, climate influences on topography are mediated by vegetation, which itself is dependent on mean annual precipitation (r = 0.77). Observations from the central Andes are consistent with landscape evolution models in which hillslope gradients are a balance between rock uplift, climatic erosional efficiency and erosional resistance of the landscape determined by bedrock lithology and vegetation.

Contrasting mountain and piedmont dynamics of sediment discharge associated with groundwater storage variation in the Biobío River

“…In the mountains, it is possible that landslides play a minor role in delivering sediment to the river network because vegetation prevents mass wasting‐derived sediments from reaching the rivers [e.g., DiBiase and Lamb , ] and can act as a slope stabilizer [e.g., Vanacker et al , ; Wu , ; Jeffery et al , ], although this depends on root architecture [e.g., Reubens et al , ] and hillslope gradient [ Vorpahl et al , ]. During a rainfall event, the proportion of exported sediment coming from such different sources as the detached material from previous or contemporary landslides, gullies, or weathered soil varies with the magnitude of Q s [ Smith et al , ].…”

Can Landsat-Derived Variables Related to Energy Balance Improve Understanding of Burn Severity From Current Operational Techniques?

“…Since forests absorb and keep rainfall to make it available during dry season [127], wildfires alter the volume stored by forests by removing the vegetation cover [128]. The consequences of that change on water balance may include: modifications of ET from burned soil and vegetation versus unburned ones [37]; alterations in soil moisture [129]; an increase in the volume of precipitation [130]; a post-fire increase in soil erosion (due to higher surface runoff) [131]; lower water quality caused by an increase in suspended sediments [132] and modifications to surface hydrology [128]. Furthermore, unlike spectral indices, ET has a physical meaning, which makes it easier to interpret than spectral indices.…”

Effect of changing vegetation on denudation (part 1): Predicted vegetation composition and cover over the last 21 thousand years along the Coastal Cordillera of Chile

“…As demonstrated in this study, climatic forcing of the ecosystem model is crucial for the simulated vegetation composition, biome establishment and associated vegetation cover and surface runoff, which are key controls of catchment denudation 10 rates (Jeffery et al, 2014). The TraCE-21ka dataset was chosen since, to our knowledge, it is the only available dataset providing continuous transient monthly data.…”

“…Although this relationship is controversial (e.g. Riebe et al, 2001;Gyssels et al, 2005), previous work highlights that vegetation is likely a first order control on catchment denudation rates (Acosta et al, 2015;Collins et al, 2004;Istanbulluoglu and Bras, 2005;Jeffery et al, 2014). While relatively simple vegetation 5…”