Goals
- Understanding the trophic and non-trophic effects of guanacoes on vegetation and ecosystem functioning
- Role of smaller-sized herbivores on vegetation dynamics
- Impact of cyclic extreme droughts on vegetation and soil dynamics
Experimental setup
Series of experiments linked under the same meta-experiment that had its time 0 in 2015, without any manipulation. (1) The first experiment was intended to evaluate the effect of extreme drought. To this end, on 2016-06-06, three roofs were installed following the Drought Net protocol within 10 x 5 m guanaco enclosures (plots 1, 3, and 5; pigeon wire up to 1 m and wire strands every 20 cm above), as well as three other enclosures but without interceptors (plots 2, 4, and 6). Initially, it was considered to use the even-numbered plots as controls, but later it seemed to be less variable to use plots within the same enclosures. As of 2020-11-27, the roofs were removed to evaluate post-drought recovery. (2) The second experiment began on the same date (year 0), also reducing rainfall, but in this case in experimental units of 3 x 1.5 m within each of the 6 enclosures, with the idea of evaluating the effect of intermittent drought (periods of three years of drought, followed by three of normality and again drought). (3) Simultaneously, in this meta-experiment, the direct and indirect effects of guanacos were studied. In each of the enclosures and their corresponding grazed areas, two 1 m2 plots were defined in 2018 (like all units in this experiment), one of them assigned to a control and the other to the annual addition of 10 L of fresh feces from nearby natural latrines. (4) In the same year, latrines were also arranged below the three original interceptors to evaluate their response to drought and subsequent recovery. (5) In 2020, a new batch of latrines (new latrine) was installed in association with intermittent interceptors (new roof) and their controls. (6) Finally, to evaluate the effect of smaller herbivores, a total enclosure with 1 cm2 welded mesh sides and roof was nested within each of the guanaco enclosures. In summary, by 2024 there were 54 plots in total: 6 small herbivore exclusions, 6 control plots with and without artificial latrines, 6 under rain interceptors with and without artificial latrines, 6 in guanaco enclosures with and without latrines, 3 in recovery from rain interceptors with and without latrines, and 6 recent latrines within the guanaco enclosures to compare with the drought experiment. In each plot, cover by species and organic matter are measured annually, and other measurements are taken sporadically (hare droppings, decomposition, temperature, respiration, seed production, humidity).