Wayqecha Amazon cloud curtain ecosystem experiment: Climate data and R processing code

Fog makes a significant contribution to the hydrology of a wide range of
important terrestrial ecosystems. The amount and frequency of fog
immersion are likely to be affected by rapid ongoing anthropogenic changes
but the effects of these changes remain relatively poorly understood
compared to changes in rainfall. Here, we present the design and
performance of a novel experiment to actively manipulate low lying fog
abundance in an old-growth tropical montane cloud forest (TMCF) in Peru -
the Wayqecha Amazon Cloud Curtain Ecosystem Experiment (WACCEE). The
treatment consists of a 30m high, 40m wide mesh curtain suspended between
two towers and extending down to the ground, and two supplementary
curtains orientated diagonally inwards from the top of each tower and
secured to the ground upslope. The curtains divert and intercept airborne
water droplets in fog moving upslope, thereby depriving a ~ 420 m2 patch
of forest immediately behind the curtains of this water source. The
treatment caused a strong reduction in both air humidity and leaf wetness,
and an increase in vapour pressure deficit, above the canopy compared to a
nearby unmodified control plot. This effect was most pronounced during the
nighttime (20:00 - 05:00). Below-canopy shifts within the treatment were
more subtle: relative humidity at 2 m height above the ground was
significantly suppressed during the daytime, while soil moisture was
apparently elevated. The treatment caused a small but significant increase
in air temperature above the canopy but a decrease in temperature in and
near the soil, while mixed effects were observed at 2 m height above the
ground. Above-canopy radiation was slightly elevated due to the treatment,
which was mainly caused by a notable increase relative to the control
during the dry season. We employ the WACCEE infrastructure to understand
in situ impacts of fog reduction within a pristine TCMF, but the basic
principle of the method is extremely versatile. Further application of the
method in other systems where fog plays a major role in ecosystem
processes could improve our understanding of the ecological impacts of
this important but understudied climate driver.