Dendrogeomorphically derived slope response to decadal and centennial scale climate variability: Black Mesa, Arizona, USA

Abstract

Abstract.A major impediment to an understanding of the links between climate and landscape change, has been the relatively coarse resolution of landscape response measures (rates of weathering, sediment production, erosion and transport) relative to the higher resolution of the climatic signal (precipitation and temperature on hourly to annual time scales). A combination of high temporal and spatial resolution dendroclimatic and dendrogeomorphic approaches were used to study relationships between climatic variability and hillslope and valley floor dynamics in a small drainage basin in the Colorado Plateau of northeastern Arizona, USA Dendrogeomorphic and vegetation evidence from slopes and valley bottoms, including root exposure, bending of trunks, change in plant cover and burial and exhumation of valley bottom trees and shrubs, suggest that the currently observed process of root colonization and rapid breakdown of the weakly cemented bedrock by subaerial weathering, related to periodic dry/wet cycle induced changes in vegetation cover, has lead to a discontinuous, climate-controlled production of sediment from these slopes. High-amplitude precipitation shifts over the last 2000-years may exert the largest control on landscape processes and may be as, or more, important than other hypothesized causal mechanisms (e.g. ENSO frequency and intensity, flood frequency) in eroding slopes and producing sediments that ultimately impact higher order drainages in the region. Current vegetation response to a prolonged drought over the past decade suggests that another major transition, incorporating vegetation change, slope erosion, sediment production and subsequent valley floor deposition, may be in its initial phase.

Late Quaternary Soil Development Enhances Aeolian Landform Stability, Moenkopi Plateau, Southern Colorado Plateau, USA

“…Livestock grazing was at a maximum on the Navajo Nation in the early 1900s, with livestock reduction efforts in the 1930s significantly reducing grazing pressure (see an excellent review in [49]), but even extreme grazing pressure with its consequent reduction of vegetative cover did not generate an overall reactivation of the aeolian sediments on the Moenkopi Plateau. During the last millennium, tree ring records [50][51][52][53] show that the western US suffered several, abrupt, multidecadal "megadroughts" of much greater severity than historical droughts including the megadrought coincident with the abandonment of Chaco Canyon (summarized in [54], p. 109). Despite large reductions in effective moisture (either due to increased temperatures or decreased precipitation) during the Holocene, the Moenkopi Dunes have been dominantly stable (Figure 11).…”

Impacts of climate change on the formation and stability of late Quaternary sand sheets and falling dunes, Black Mesa region, southern Colorado Plateau, USA

“…Bull, 1991), specifically from wetter to drier conditions (e.g. McAuliffe et al, 2006;Scuderi et al, 2008); (2) a change in the type or density of vegetation cover (e.g. Schumm and Lichty, 1965;Schlesinger et al, 1990;Okin et al, 2001;Puta et al, 2013); and/or (3) a disturbance within the fluvial system (e.g.…”

The interactions between vegetation and erosion: new directions for research at the interface of ecology and geomorphology

“…Plants affected by slope degradation and retreat have been used repeatedly to analyze and quantify spatial and temporal erosion modes and rates. Reduced vitality of plants and sudden reduction of growth rates in stems have been used to decipher shore (Bégin et al, 1991a(Bégin et al, , 1991bFantucci, 2007) or hillslope erosion histories (McAuliffe et al, 2006;Scuderi et al, 2008;Casalí et al, 2009).…”