Dataset contains fluxes of biocrusts and bare soil from the Succulent Karoo, South Africa. The dataset consists of 3 files: sample weights per measurement, PTR VOC data and greenhouse gases, and GC-MS data. The samples were measured inside a climate chamber under controlled temperature, light, and humidity conditions and wetted with artificial rainwater. Sample cuvettes were flushed with zero air. Five different types of classified according to the method of Weber et al., (2018; https://doi.org/10.2989/10220119.2018.1527782) as biocrust samples dominated by light cyanobacteria, dark cyanobacteria, chlorolichens, and mosses, as well as bare uncolonized soil were analysed. The samples were collected in September 2023 by the research group of Bettina Weber, accompanied by Stefan Herdy and Rodrigo Paidano Alves, in Soebatsfontein, located in the Succulent Karoo, South Africa (research permit: FLORA 0008/2023; export permit: FLORA 0009/2023). The collected samples were dried and kept in Ø 5,5 cm plastic petri dishes, sealed with a lid and tape, and stored in a freezer at -20°C at the University of Graz, Austria, before measurements. Of the 5 sample types three replicates each were measured. In preparation for the measurements, the samples were taken out of a -20°C freezer one day before the experiment took place and kept at room temperature overnight. On the following day, each sample was transferred to a glass petri dish and placed in a separate cuvette (glass bottle, 2.5 L volume) contained within a light and temperature-controlled climate chamber. The climate chamber was constructed at the Max-Planck-Institute for Chemistry in Mainz. The light from LED lamps (XLG-150-L-AB, poly klima® GmbH) could be regulated, reaching 0-1500 µmol m⁻² s-1 photosynthetically active radiation (PAR) at a distance of 30 cm from the light source, and the temperature could be set between 18 - 50 °C using two thermoelectric Peltier assemblies (AR-AR-100-24, Adaptive, European Thermodynamics Ltd). The chamber was equipped with sensors for temperature and humidity conditions. The light intensity was set to approximately 480-500 µmol/m-2 s-1 PAR, and controlled at each of the cuvette positions at the beginning of each measurement using a light sensor (Skye SKP 215/S quantum sensor connected to a Skye SKP 200 display meter; Skye Instruments Ltd., Llandrindod Wells, Powys, UK). Four 2.5 L glass cuvettes (three samples and one empty-blank) were placed inside the climate chamber, which was pre-conditioned to 25°C, which resulted in a temperature of 25.0 ± 0.2°C inside the chamber. Each of the three pre-conditioned samples on glass petri dishes was placed inside three randomly chosen cuvettes, whereas the fourth one was used as a blank or background cuvette. This latter cuvette contained no sample, but only an empty glass petri dish. Clean air was generated by a zero-air generator (VZA-138, Tofwerk AG) and continuously streamed though all four cuvettes. The chemical measurements were performed by sampling airflow sequentially between the cuvettes (each cuvette was measured for 5 minutes in turn). The zero-air generator removes about 80 % of the methane in ambient air, resulting in 0.29±0.05 ppmv. The air flow rate through each glass cuvette was set to 500 mL min-1 resulting in an air residence time in each cuvette of 5 minutes. All tubing and connections were made from Teflon. By using clean zero air to flush the cuvettes, by design, only VOC emissions can be observed. The samples were subjected to five sequential treatment phases. (1) Samples were exposed to dry air in the dark for 1 hour. (2) The inflow air then was humidified to ~70 % relative humidity by bubbling through a reservoir filled with artificial rainwater (Fig. A1 in Appendix A). (3) After 10 hours of humid air exposure in the dark, the light was switched on. (4) After 12 hours of moist air exposure in the light, the samples were manually wetted by slowly dripping artificial rainwater onto their surface. This was followed by a minimum 12-hour dry-out period, during which the lights remained on for the first 10 hours. (5) The lights were switched off after a total of 12 hours of illumination. The only exception was the first moss sample measurement, where light and dark cycles alternated every hour to investigate light dependent effects. Artificial rainwater was delivered via a valve system that allowed watering without opening the glass chambers, maintaining continuous air flow. The total water volume was controlled by adjusting the valve opening time. Watering was stopped when the samples were thoroughly moistened but not submerged, as determined by visual inspection. The artificial rainwater was comprised of the salts K2CO3, Na2CO3, CaCO3, FeSO4×7 H2O and MnSO4×H2O in a concentration of 8.7, 4.4, 5.0, 4.3 and 0.6 mg L-1, respectively, dissolved in LC-MS grade water (Sigma Aldrich). The solution was autoclaved for 15 min at 121 °C. The pH was set to 6.5 with an HCl solution. The air flowing from the cuvettes was led via ¼ inch (0.625nm outer diameter) Teflon tubing into the measurement devices. Measurements proceeded sequentially with 5 minutes per cuvette, always starting and alternating with the background cuvette to bracket each sample by background readings. High time resolution was obtained using a PTR-TOF-MS (Vocus PTR-ToF-MS, Tofwerk AG and Aerodyne Research, Inc.) for VOC measurements and a PICARRO gas analyser for CO, CO2, CH4, and H2O (PICARRO G2401-m, Picarro Inc., Sunnyvale-California, USA). For improved compound speciation, air was sampled onto adsorbent filled cartridges four times during each measurement: (A) at the beginning of the experiment (phase 1), (B) after 12 hours of humidification in (phase 3), (C) immediately after wetting with artificial rainwater in (phase 4), and (D) 12 hours after wetting and subsequent drying (phase 5). Air from the sample cuvettes and the background cuvette was collected using a handheld pump (Gilian GilAir Plus Personal Air Sampling Pump; Sensidyne) with a flow rate setting of 200 mL min-1 for 4 min, collecting 800 mL in total. After completing a full 24-hour measurement cycle, the sample cuvettes were cleaned first with 90 % ethanol, then with LC-MS grade water, and heated at 110°C for at least 2 hours to dry. The PTR was operated under standard conditions with a drift tube pressure of 2.3 mbar, a reactor temperature of 90 °C, and a potential of 475 V along the FIMR. This results in an E/N of around 110 Td. The instrument was calibrated using a diluted calibration gas mixture (National Physical Laboratory, Teddington, USA) with acetaldehyde, methanol, ethanol, acetone, dimethyl sulfide, isoprene, 3-carene (a monoterpene), acetonitrile, methyl vinyl ketone (3-buten-2-one), butan-2-one, benzene, toluene, m-xylene, trimethylbenzene, and trichlorobenzene with a 1- or 3-point calibration before each measurement. The concentrations for compounds not included as standards were calculated using reaction rates and transmission curves. If no proton transfer reaction rate was found in the literature a value of 2.50×10−9 cm3 molecule−1 s−1 was used. The custom-built cartridges were made of silica-coated stainless-steel tubes (89 mm x 5.33 mm I.D., SilcoNert 2000, SilcoTek) containing 150 mg of Tenax ® TA mesh range 80/100 (Supelco) and Carbograph ® 5 TD mesh range 40/60 (Lara srl.). The sorbents were sealed with quartz wool and stainless-steel tension springs (Sigma Aldrich). Prior to use, the cartridges were conditioned at 300 °C for 1 hour while being flushed with pure nitrogen at 2 bar pressure (TC 20, Markes International). After sampling, the cartridges were stored in a freezer at -20 °C until analysis. Prior to measurement, the sampled cartridges were removed from the freezer and brought to ambient temperature before being desorbed using a thermal desorption unit (TD100-xr and UNITY xr, Markes International). The thermal desorption process consisted of two stages. In the first stage, the cartridges were dry-purged for 5 min with a flow rate of 50 ml min−1 and then desorbed for 5 min at 250 °C. The desorbed samples were pre-concentrated onto a cold trap (Material Emissions, Markes International). In the second stage, the cold trap was first purged for 1 min at 10 °C and then injected at 250 °C for 5 min into the gas chromatograph (GC, Agilent Technologies 7250) using a split flow of 2 mL min−1. The GC was equipped with a 60 m long chiral β-DEX™ 120 capillary column (Sigma Aldrich) with an inner diameter of 250 μm and a film thickness of 0.25 μm. Helium 5.0 was used as a carrier gas at 1.2 mL min−1 flow rate. The GC oven temperature was initially held at 40 °C for 5 min, then ramped at 1.5°C min−1 to 110 °C, followed by a ramp at 5°C min−1 to 220 °C, where it was held for 2 minutes. Detection was performed using an Accurate Mass Quadrupole Time-of-Flight-Mass Spectrometer (Q-TOF, Agilent Technologies). The GC-TOF-MS peaks were integrated using chromatography analysis software Mass Hunter Quant (Agilent Technologies). Compounds were quantified using a gas standard calibration mixture (Apel-Riemer International, USA) diluted with air. The VOC fluxes were calculated according to the following formula: F_(a,g)=Q*(C_t-C_0)/N_(a,g) where F_a is the flux rate (µmol m-2 h−1) per surface area and F_g is the flux rate (µmol g−1 (DW) h−1) per dry weight of the sample, Q is the flow rate through the sample cuvette (500 mL min−1 equals 0.03 m3 h−1), N_a is the surface area (0.00196 m²) of the 50 mm petri dish with the sample or N_g is the dry weight of the sample, C_t is the BVOC concentration in the chamber, and C_0 is the BVOC concentration outside the chamber. The data from each cuvette was averaged over the 5 min measurement intervals, excluding the first minute and last 20 seconds. The values of the background cuvette were interpolated from the sample before and after each sample cuvette and subtracted from each sample value. The measurement uncertainty of compounds within the calibration gas mixture of the PTR is 15 %, as has been previously calculated from the error of the dilution of the calibration gas, the calibration gas concentration, the precision of the instrument, and the error of the fit of the calibrations. Compounds not present in the calibration gas mixture have an estimated uncertainty of 50 %.