TY  - JOUR
A1  - Acosta, Veronica Torres
A1  - Schildgen, Taylor F.
A1  - Clarke, Brian A.
A1  - Scherler, Dirk
A1  - Bookhagen, Bodo
A1  - Wittmann, Hella
A1  - von Blanckenburg, Friedhelm
A1  - Strecker, Manfred
T1  - Effect of vegetation cover on millennial-scale landscape denudation rates in East Africa
JF  - Lithosphere
N2  - The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating this concept over long time scales and across landscapes has proven to be difficult, especially in settings complicated by tectonic forcing and variable slopes. We investigate this problem by measuring cosmogenic Be-10-derived catchment-mean denudation rates across a range of climate zones and hillslope gradients in the Kenya Rift, and by comparing our results with those published from the Rwenzori Mountains of Uganda. We find that denudation rates from sparsely vegetated parts of the Kenya Rift are up to 0.13 mm/yr, while those from humid and more densely vegetated parts of the Kenya Rift flanks and the Rwenzori Mountains reach a maximum of 0.08 mm/yr, despite higher median hillslope gradients. While differences in lithology and recent land-use changes likely affect the denudation rates and vegetation cover values in some of our studied catchments, hillslope gradient and vegetation cover appear to explain most of the variation in denudation rates across the study area. Our results support the idea that changing vegetation cover can contribute to complex erosional responses to climate or land-use change and that vegetation cover can play an important role in determining the steady-state slopes of mountain belts through its stabilizing effects on the land surface.
Y1  - 2015
U6  - https://doi.org/10.1130/L402.1
SN  - 1941-8264
SN  - 1947-4253
VL  - 7
IS  - 4
SP  - 408
EP  - 420
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Garcin, Yannick
A1  - Schildgen, Taylor F.
A1  - Acosta, Veronica Torres
A1  - Melnick, Daniel
A1  - Guillemoteau, Julien
A1  - Willenbring, Jane
A1  - Strecker, Manfred
T1  - Short-lived increase in erosion during the African Humid Period
BT  - evidence from the northern Kenya Rift
JF  - Earth & planetary science letters
N2  - The African Humid Period (AHP) between similar to 15 and 5.5 cal. kyr BP caused major environmental change in East Africa, including filling of the Suguta Valley in the northern Kenya Rift with an extensive (similar to 2150 km(2)), deep (similar to 300 m) lake. Interfingering fluvio-lacustrine deposits of the Baragoi paleo-delta provide insights into the lake-level history and how erosion rates changed during this time, as revealed by delta-volume estimates and the concentration of cosmogenic Be-10 in fluvial sand. Erosion rates derived from delta-volume estimates range from 0.019 to 0.03 mm yr(-1). Be-10-derived paleo-erosion rates at similar to 11.8 cal. kyr BP ranged from 0.035 to 0.086 mm yr(-1), and were 2.7 to 6.6 times faster than at present. In contrast, at similar to 8.7 cal. kyr BP, erosion rates were only 1.8 times faster than at present. Because Be-10-derived erosion rates integrate over several millennia; we modeled the erosion-rate history that best explains the 10Be data using established non-linear equations that describe in situ cosmogenic isotope production and decay. Two models with different temporal constraints (15-6.7 and 12-6.7 kyr) suggest erosion rates that were 25 to 300 times higher than the initial erosion rate (pre-delta formation). That pulse of high erosion rates was short (similar to 4 kyr or less) and must have been followed by a rapid decrease in rates while climate remained humid to reach the modern Be-10-based erosion rate of,similar to 0.013 mm yr(-1). Our simulations also flag the two highest Be-10-derived erosion rates at 11.8 kyr BP related to nonuniform catchment erosion. These changes in erosion rates and processes during the AHP may reflect a strong increase in precipitation, runoff, and erosivity at the arid-to-humid transition either at 15 or similar to 12 cal. kyr BP, before the landscape stabilized again, possibly due to increased soil production and denser vegetation.
KW  - northern Kenya Rift
KW  - Baragoi
KW  - paleo-delta
KW  - African Humid Period
KW  - erosion
KW  - Be-10
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2016.11.017
SN  - 0012-821X
SN  - 1385-013X
VL  - 459
SP  - 58
EP  - 69
PB  - Elsevier
CY  - Amsterdam
ER  -