TY  - JOUR
A1  - van der Meij, Marijn W.
A1  - Reimann, Tony
A1  - Vornehm, V. K.
A1  - Temme, Arnaud J. A. M.
A1  - Wallinga, Jakob
A1  - van Beek, Roy
A1  - Sommer, Michael
T1  - Reconstructing rates and patterns of colluvial soil redistribution in agrarian (hummocky) landscapes
JF  - Earth surface processes and landforms : the journal of the British Geomorphological Research Group
N2  - Humans have triggered or accelerated erosion processes since prehistoric times through agricultural practices. Optically stimulated luminescence (OSL) is widely used to quantify phases and rates of the corresponding landscape change, by measuring the last moment of daylight exposure of sediments. However, natural and anthropogenic mixing processes, such as bioturbation and tillage, complicate the use of OSL as grains of different depositional ages become mixed, and grains become exposed to light even long after the depositional event of interest. Instead, OSL determines the stabilization age, indicating when sediments were buried below the active mixing zone. These stabilization ages can cause systematic underestimation when calculating deposition rates. Our focus is on colluvial deposition in a kettle hole in the Uckermark region, northeastern Germany. We took 32 samples from five locations in the colluvium filling the kettle hole to study both spatial and temporal patterns in colluviation. We combined OSL dating with advanced age modelling to determine the stabilization age of colluvial sediments. These ages were combined with an archaeological reconstruction of historical ploughing depths to derive the levels of the soil surface at the moment of stabilization; the deposition depths, which were then used to calculate unbiased deposition rates. We identified two phases of colluvial deposition. The oldest deposits (similar to 5 ka) were located at the fringe of the kettle hole and accumulated relatively slowly, whereas the youngest deposits (<0.3 ka) rapidly filled the central kettle hole with rates of two orders of magnitude higher. We suggest that the latter phase is related to artificial drainage, facilitating accessibility in the central depression for agricultural practices. Our results show the need for numerical dating techniques that take archaeological and soil-geomorphological information into account to identify spatiotemporal patterns of landscape change, and to correctly interpret landscape dynamics in anthropogenically influenced hilly landscapes. (c) 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.
KW  - geochronology
KW  - OSL
KW  - tillage
KW  - erosion
KW  - kettle hole
KW  - hummocky
KW  - landscape evolution
Y1  - 2019
U6  - https://doi.org/10.1002/esp.4671
SN  - 0197-9337
SN  - 1096-9837
VL  - 44
IS  - 12
SP  - 2408
EP  - 2422
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Dietze, Michael
A1  - Swoboda, Charlie
A1  - Cook, Kristen L.
A1  - Adhikari, Basanta R.
A1  - Vieth-Hillebrand, Andrea
A1  - Bonnet, Stephane
A1  - Reimann, Tony
A1  - Koutsodendris, Andreas
A1  - Sachse, Dirk
T1  - Late holocene landscape collapse of a trans-himalayan dryland
BT  - human impact and aridification
JF  - Geophysical research letters
N2  - Soil degradation is a severe and growing threat to ecosystem services globally. Soil loss is often nonlinear, involving a rapid deterioration from a stable eco-geomorphic state once a tipping point is reached. Soil loss thresholds have been studied at plot scale, but for landscapes, quantitative constraints on the necessary and sufficient conditions for tipping points are rare. Here, we document a landscape-wide eco-geomorphic tipping point at the edge of the Tibetan Plateau and quantify its drivers and erosional consequences. We show that in the upper Kali Gandaki valley, Nepal, soil formation prevailed under wetter conditions during much of the Holocene. Our data suggest that after a period of human pressure and declining vegetation cover, a 20% reduction of relative humidity and precipitation below 200 mm/year halted soil formation after 1.6 ka and promoted widespread gullying and rapid soil loss, with irreversible consequences for ecosystem services.
KW  - geomorphology
KW  - paleoclimate
KW  - human activity
KW  - Tibetan plateau
KW  - late Holocene
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL084192
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13814
EP  - 13824
PB  - American Geophysical Union
CY  - Washington
ER  -