Runoff Development and Soil Erosion in a Wet Tropical Montane Setting under Coffee Cultivation

Abstract

The western interior portions of Puerto Rico offer optimal climatic conditions for coffee cultivation. However, land and water degradation result when abrupt topographic relief and high annual rainfall combine with forest conversion for coffee farming. Small‐scale rainfall simulation experiments were conducted to quantify runoff and erosion from four land surface types (i.e., mulched, weed‐covered, and bare soils under active cultivation, and unpaved roads) representative of coffee farms in Puerto Rico. Results show that mulch‐covered soils had runoff coefficients similar to those from undisturbed forested conditions (~4%), and that they eroded at rates about a quarter of those for bare cultivated soils. Weed‐covered soils had surprisingly high runoff coefficients (~70%), yet their erosion rates were only three‐fourths of those for bare soils. Annualized erosion rates from unpaved roads were 65 Mg ha−1 y−1, or ten times greater than bare soils and about a hundred times higher than weed‐ or mulch‐covered surfaces. Farm‐scale sediment production estimates amount to ~11 Mg ha−1 y−1, about two‐orders of magnitude higher than under forested conditions. At the farm‐scale, only 2 – 8% of the total sediment is potentially attributable to cultivated hillslopes. In contrast, unpaved roads may account for over 90% of the sediment budget, even though they comprise only 15% of the farm surface area. Therefore, while providing mulch or a vegetative cover to bare cultivated soils should be part of effective soil management, mitigating the effects of coffee cultivation on downstream water resources must focus on the unpaved road network as the primary sediment source. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Forest Roads on Runoff Initiation in Low‐Order Ephemeral Streams

“…Research dating to the 1960s has focused on the potential of forest roads to increase peak flows (Harr et al, ; Rothacher, ) and sediment yields (Beschta, ; Megahan, ; Megahan & Kidd, ). Although tools to mitigate their effects have been developed and implemented (e.g., Cao et al, ; Ramos‐Scharrón, ; Ziegler et al, ), unpaved roads remain a primary driver of water quality and aquatic habitat degradation (e.g., Biggs et al, ; Jones et al, ; Ramos‐Scharrón & Thomaz, ; Sidle et al, ; Wemple et al, ).…”

Land degradation monitoring using terrestrial ecosystem carbon sinks/sources and their response to climate change in China

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