General Project Description
Both experiments have been installed near to each other at a primary cloud rainforest near Wayqecha research station (latitude: 13°2´56˝ S, longitude 71°32´13˝W), run by the Amazon Conservation Association. All the plots have been carefully selected to (i) be similar in terms of tree species composition and tree density, (ii) show no signs of human disturbance (e.g: logging, fire) and (iii) be representative of the region as a whole. The site is around 3000 above sea level, has mean annual temperature around 12 celsius and mean annual rainfall around 1600 mm.
Private Area of Conservation Cloud Forest (Área de Conservación Privada Bosque Nublado).
The cloud reduction experiment consists of two plots. One control and one treatment. The treatment plot consists of a 30m high and 40m wide vertical panel of fine plastic mesh which has been suspended between two towers and extends ~10 m above the plant canopy down to ground level. The panel is angled perpendicular to the predominant wind direction to intercept airborne water particles moving up a forested valley thereby reducing cloud water inputs to the experimental forest plot behind the curtain. In addition, mesh panels are erected along the up-slope sides of the experimental plot, minimizing the possibility for airborne water inputs to be deposited in the experimental plot from the sides. The top remains open to maintain natural light conditions and permit vertical water inputs within the cloud-reduction treatment. Given that the curtain exceeds canopy height by around 10 m there should be limited canopy deposition of airborne water within the treatment plot from air moving over the top of the mesh curtain. Most radiation in cloud forest is diffuse, rather than direct, which will minimize the shading effects of the mesh. A 30 by 30 m patch of unmodified forest has been selected 50 m from the treatment as an experimental control.
Rainfall/Groundwater Flow Exclusion
The rainfall/groundwater flow exclusion experiment consists of three 30 * 30 m plots- one control and two treatments. In one treatment plot (rainfall exclusion), transparent plastic panels have been placed on a wooden framework around 2 m above ground level over ~95% of the plot. The panels channel incident rainfall down-slope away from the plot. In the other treatment plot (lateral soil flow exclusion), the up-slope border of the plot has been trenched down to the bedrock and the trench has been lined with plastic to eliminate lateral soil water flow immediately down-slope. A similar forest nearby has been left unmodified to function as a control. Together with the control, these two treatments are designed to isolate the influence of water supply from rainfall versus groundwater flow which is a potentially important but understudied plant water source in cloud forest.