Climate Change in Remote Mountain Regions: A Throughfall-Exclusion Experiment to Simulate Monsoon Failure in the Himalayas

The Himalayas are predicted to experience more than 3 times the mean global rise in temperature, as well as erratic rainfall patterns and an increased likelihood of total monsoon failures. While many ecosystem manipulation experiments aiming at understanding the effects of altered precipitation, temperature, and carbon dioxide are conducted globally, such experiments are rare in Asia, particularly in the Himalayas. To fill this gap, we simulated late onset of monsoon precipitation, as well as total monsoon failure, in a multiyear drought stress experiment in Bhutan. Two treatments, 100% throughfall exclusion and ambient control plots, were applied to 725 m2 plots (25 m × 29 m), each with 2 replicates in a hemlock-dominated (Tsuga dumosa) and oak-dominated (Quercus lanata and Quercus griffithii) ecosystem at 3260 and 2460 m elevations, respectively. Roof application reduced the volumetric soil water content in the upper (0–20 cm) soil layer by ∼ 20% in coniferous and ∼ 31% in broadleaved forest; the deeper soil layers were less affected. We demonstrate that large-scale throughfall-exclusion experiments can be successfully conducted even in a remote Bhutan Himalayan setting. The experiences gathered could be utilized for future long-term ecological monitoring studies in the Himalayan region.