Impact of forest cover and conservation agriculture on sediment export: A case study in a montane reserve, south-western China

Hongxi Liu; Yujun Yi; Sergey Blagodatsky; Georg Cadisch

doi:10.1016/j.scitotenv.2019.134802

Impact of forest cover and conservation agriculture on sediment export: A case study in a montane reserve, south-western China

Sci Total Environ. 2020 Feb 1:702:134802. doi: 10.1016/j.scitotenv.2019.134802. Epub 2019 Oct 31.

Authors

Hongxi Liu¹, Yujun Yi², Sergey Blagodatsky³, Georg Cadisch⁴

Affiliations

¹ State Key Laboratory of Water Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China; State Research and Development Center for Watershed Environmental Eco-engineering, Beijing Normal University, Zhuhai 519087, China.
² State Key Laboratory of Water Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China. Electronic address: yiyujun@bnu.edu.cn.
³ Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Garbenstraße 13, Stuttgart 70599, Germany; Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, 142290 Pushchino, Russia.
⁴ Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, Garbenstraße 13, Stuttgart 70599, Germany.

PMID: 31733551
DOI: 10.1016/j.scitotenv.2019.134802

Abstract

Reforestation and agricultural conservation have long been recognized as important in reducing on-site soil loss and off-site sediment export. Quantitative assessment of their effectiveness is critical, and assists cost-benefit analysis and decision-making in land management and landscape planning. We applied a paired watershed approach to monitor 1-year sediment export in two watersheds with forest-dominated (reference) and mosaic (target) land use in the Naban River Watershed National Natural Reserve (NRWNNR) in Xishuangbanna, south-western China. Analysis of land-use change in the target watersheds showed decreasing total forest cover (FC) (from 57% to 47%), but increasing FC in steep areas (from 54% to 59%) from 2007 to 2012. A distributed hydrological model (Land-Use Change Impact Assessment, LUCIA) was well calibrated and validated through field data from the two watersheds. Scenarios were created representing different FCs (from 31% to 83%) and agricultural management (as-usual and conservation). Simulation results quantified the relation between FC and sediment export as a logarithmic or logit model, indicating at least one turning point of FC, beyond which further forest reduction should significantly increase sediment export. This point was identified in the range between 57% and 61% of the target watershed under as-usual management; it was shifted to 47%-53% by conservation agriculture. Compared with the reference (with 83% FC), conservation agriculture was able to almost fully compensate for increased sediment export by forest reduction to 57% in 2007. However, when forest was reduced further to 47% in 2012, sediment export increased significantly. We concluded that total FC was as important as FC in montane watershed management in steep areas; and crop type conversion, such as rubber to maize in this study, and on-site agriculture management affect more to sediment export than agricultural expansion. We recommend conservation agriculture as an efficient tool for reducing sediment export on a watershed scale.

Keywords: Land-use change impact assessment; Minimum forest cover; Soil conservation in tropics; Soil erosion modelling; Watershed management.