DOI: 10.5061/dryad.ns1rn8q31
title: Cold waves in the Amazon rainforest and their ecological impact

description: Cold waves crossing the Amazon rainforest are a rare phenomenon predicted
 to increase in intensity under climate change. We here describe an
 extensive cold wave occurring in June 2023 in Amazonian-Andean forests,
 compared environmental temperatures to experimentally tested thermal
 tolerances and its impact on lowland animal communities (insects and wild
 mammals). While we found strong reductions in abundance of all animal
 groups under the cold wave, tropical lowland animals showed thermal
 tolerance limits below the lowest environmental temperatures measured
 during the cold wave, and abundances of most studied taxa recovered over
 the next season; nevertheless, small thermal safety margins suggest that
 an increased intensity of cold waves in the future could imperil animal
 communities in the Amazon.
description: <strong>Temperature data</strong>
 Air temperature was measured at each plot along the elevation
 gradient with iButton sensors (Analog Devices, Inc, Wilmington, USA) at
 1.5 m height every four hours, hanging from a horizontal branch. The
 sensors were shielded with white plastic dishes (diameter ca. 18 cm) to
 protect them from rain and direct sunlight [13]. In addition, each plot
 was equipped with a TOMST4-temperature and soil humidity logger (TOMST
 s.r.o., Prague, Czech Republic), continuously measuring temperature and
 soil humidity at 6 cm depth, as well as temperature at the surface and in
 15 cm height. <strong>Insect
 data</strong> <em>(1) Malaise:
 </em>At each plot in each field season, one malaise trap was
 operated for seven days. Malaise traps were based on the Townes Malaise
 trap model, albeit with a black roof and a slightly smaller size
 (dimensions of the capture area: height front: 0.90 m; height rear:
 0.60 m; length: 1.60 m); Ethanol (96 %) was used as the capture fluid to
 ensure the preservation of specimens. For each malaise trap sample, the
 wet, in ethanol preserved,insect biomass was determined by weighingthe
 insects usinga metal sieve. When the time between two drops of ethanol
 reached 10 s, the wet weight of the sample (biomass) was measured using a
 precision scale. <em>(2) Baited pitfall traps:
 </em>At each plot in each field season, three differently baited
 pitfall traps (human dung, chicken carrion, fermented banana) were set up
 in a triangle with ~50 m distance and left open for two days. Traps
 consisted of two stacked cups (ca. 500 ml) buried with the upper rim being
 even with the surface, filled halfway with water and a drop of unscented
 detergent. Baits wrapped in gauze were hanging in a 45-degree angle over
 the cup. The traps were covered with a triangular plastic tarp to protect
 them from rain. All collected insects were counted, and the wet biomass
 was determined by placing all organisms of a sample individually with
 forceps on a microscale. <em>(3) Measurements of
 thermal tolerance limits:</em> We determined critical thermal minima
 (CT<sub>min</sub>) and maxima (CT<sub>max</sub>)
 of insects using an Eppendorf Thermostat C [16]. In total, 414 insects
 (Coleoptera (n = 136), Diptera (n = 80), Hymenoptera (n = 93), Lepidoptera
 (n = 37), Hemiptera (n = 41) and Orthoptera (n = 27)), which were
 collected by hand-netting on the study plots, were placed inside plastic
 tubes in the Eppendorf Thermostat C and exposed to gradually increasing or
 decreasing heat (acclimation temperature 28 °C for 10 min, ramping rate
 0.5 °C per minute). We tested for adaptation to colder temperatures by
 exposing a subset of insects (n = 64) to an acclimation temperature of 14
 °C for 10 min before following the normal protocol.
 CT<sub>max</sub> and CT<sub>min</sub> were defined
 as the temperature at which insects lost their locomotive ability, at
 which the insect was removed from the Thermostat. For both
 CT<sub>max</sub> and CT<sub>min
 </sub>temperatures, we also noted if insects were dead or still
 alive after a waiting time of 60 minutes (after the end of the experiment)
 at room temperature. <strong>Mammal
 data</strong> Mammal data werecollected by camera
 trap monitoring within each of the three field seasons. At each plot, four
 motion- and infrared-operated camera traps (Bushnell Trophy Cam HD
 Essential) were attached to a tree at ~1 m height, if available near
 trails, for seven days, summing up to 6048 camera trap hours for the three
 plots. Cameras were programmed to record 10 second videos with an inactive
 period of one minute. For analyses of mammal abundance, we considered two
 videos of the same species as independent with one hour time difference.
 All species were identified using the field guide from Emmons and Feer
 [19] and taxonomy was updated according to the ASM database (ASM Mammal
 Diversity Database). Abundance was calculated by summing up all
 observed individuals of each species (for each plot in each season), and
 species richness by counting the number of recorded species per plot and
 season.
description: # Cold waves in the Amazon rainforest and their ecological impact
 [https://doi.org/10.5061/dryad.ns1rn8q31](https://doi.org/10.5061/dryad.ns1rn8q31) ## Description of the data and file structure Climate and biodiversity were monitored at three study locations ("plots") in the Peruvian rainforest. We used thermal sensors, pitfall traps, malaise traps, manual netting and camera traps. Thermal tolerance experiments were conducted with a programmable thermoblock. ### Files and variables #### File: Malaise.xlsx **Description:** Malaise traps for community biomass of mainly flying insects ##### Variables * Plot: ID of study site * Field_season: number of sampling round  * dateon: Date of setting up the trap * dateout: Date of removing the trap * Note: special observations * Mass: wet insect biomass in gram #### File: dailyTemp\_iB.xlsx **Description:** temperature measured by iButton loggers ##### Variables * Tmean: daily mean temperature - Tmin: daily minimum temperature - Tmax: daily maximum temperature - min_10th: minimum 10th percentile - max_10th: maximum 10th percentile - below_10th: Cold wave criterium: is daily mean below min. and max. 10th percentile - Field_season: number indicates field season 1, 2 or 3. Empty cells are measurements outside the sampling period #### File: dailyTemp\_TMS.xlsx **Description:** temperature measured by TMS soil loggers, unit for all variables listed below is °C ##### Variables * Tmean: daily mean air temperature * Tmin: daily minimum air temperature * Tmax: daily maximum air temperature * TSurfmean: daily mean surface temperature * TSurfmin: daily minimum surface temperature * TSurfmax: daily maximum surface temperature * TSoilmean: daily mean soil temperature * TSoilmin: daily minimum soil temperature * TSoilmax: daily maximum soil temperature #### File: Mammals.xlsx **Description:** Mammal data from camera traps ##### Variables * Diversity: number of different species recorded * Abundance: number of individuals recorded (considered as new individual if minimum one hour between observations) * Contains list of species with its number of observations. Empty cells indicate, that no individuals of this species were observed. * Rodents grouped together (morphospecies) #### File: Plots.xlsx **Description:** Coordinates of all study locations along the gradient (not only cold wave focus location) ##### Variables * Plot: ID of study site * Latitude * Longitude * Elevation (masl): in meters above sea level, masl #### File: Pitfalls.xlsx **Description:** data from pitfall traps for ground-dwelling arthropods ##### Variables * Trap B = fermented banana, M = rotten meat, D = humand dung * Mass_Total: wet total biomass * Mass_Rest: biomass without dung beetles and flies * Mass_Sca: biomass dung beetles * Number_Sca: number of dung beetles #### File: Thermaltolerance.xlsx **Description:** data from thermal tolerance experiments. Empty cells indicate not applicable data  ##### Variables * CTmin: Critical minimal limit, temperature in °C * CTmax: Critical maximum limit, temperature in °C * Regain_mov: Regain of movement within 1 hour after experiment * Observer: 3 different observers conducted the tests, indicated with 1, 2 or 3 #### File: ColdWave\_analyses\_figures.R Description: code written in the software R to analyze and create the figures included in the manuscript ## Code/software Microsoft Excel R Studio