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## Plant materials Plants were grown in pots filled with loamy sand soils collected from the Jornada Experimental Range (JER), New Mexico, USA. Grasses were grown in 18 cm tall × 16.5 cm top diameter plastic pots, and shrubs in 21.5 cm tall × 23 cm top diameter plastic pots. The seedlings were germinated in a glasshouse at the University of Arizona campus in Tucson, AZ, USA, with full sun exposure and a temperature range of 24–32°C. Soils were brought to field capacity every other day. Approximately 30 days before the wind tunnel experiment, pots were transported to an outdoor common garden at the JER headquarters and kept well-watered. ## Sandblasting experiments Sandblasting experiments assessing the response of grass and shrub species to different levels of sand flux were conducted during the 2018 and 2019 growing seasons. The 2018 experiment with 5-minute exposure times represented low (every 14 days) and high (every 7 days) sandblasting frequencies (FRlow and FRhigh, respectively), and low (60 g cm−1 min−1) and high (120 g cm−1 min−1) sand flux rates (FLlow and FLhigh, respectively). These were applied in a full factorial design (n = 6 for each treatment, Table 1). Control treatments consisted of wind only (no abrading material) applied at low and high frequencies (Wlow and Whigh, respectively). The trial ran for 42 days (16 August–27 September 2018) such that FRlow and FRhigh treatments received 3 and 6 sandblasting events, respectively (Table 1). The designated sand flux amount (60 and 120 g cm−1 min−1), frequency (3 and 6 events), and exposure time (5 minutes) in our 2018 experiment produced a total sand transport of 900 and 3600 g cm−1, which brackets the total annual sand transport for a P. glandulosa shrubland at the JER study site. Wind speeds in our tunnel trials were set to 11 m s−1 at 15 cm height, which gave a shear velocity of c. 40 cm s−1 with the roughness array. A wedge-shaped trap (25 cm tall × 1 cm wide) was situated slightly after the test section to collect transported material. Collected sediments were weighed and divided by the running time and the trap width (1 cm) to calculate the real sand flux rate (g cm−1 min−1) in each trial. The 2019 experiment was slightly modified. Because A. canescens and L. tridentata were minimally influenced by sandblasting in our 2018 experiment, our 2019 experiment focused on P. glandulosa and the three grasses. Treatments were also elaborated in 2019 to test wind-only effects [low wind speed (LW; 8 m s−1) and high wind speed (HW; 11 m s−1)] and to quantify the effects of smaller sand flux events [low sand flux rate (LF, 20 g cm−1 min−1), medium sand flux rate (MF, 30 g cm−1 min−1), and high sand flux rate (HF, 60 g cm−1 min−1); all with the high wind speed; Table 1]. The control treatment (CK) consisted of no wind and no abraders. As in 2018, exposure times were 5 min and there were six replicates per species per treatment (144 pots in total). Plants in each treatment experienced six separate events spaced at roughly 7-day intervals between 28 August and 09 October 2019. Table 1: Wind speeds and the frequency (FR) and intensity (i.e., sand flux rate, FL) of sandblasting trials conducted in 2018 and 2019. Exposure times were 5 minutes in all cases. Treatments tested in 2019 were modified based on results obtained in 2018 trials. In 2019, the control treatment (CK) consisted of no wind and no abraders; the wind-only treatments were conducted at a low wind (LW) speed (8 m s−1) and a high wind (HW) speed (11 m s−1). | Year | Treatment designation | Wind speed (W, m s-1) | Sandblasting Frequency (FR) | Sand flux (FL,g cm-1 min-1) | |--------|-------------------------|-------------------------|-----------------------------|-------------------------------| | 2018 | Wlow | 11 | Every 14 days | 0 | | | Whigh | 11 | Every 7 days | 0 | | | FRlowFLlow | 11 | Every 14 days | 60 | | | FRlowFLhigh | 11 | Every 14 days | 120 | | | FRhighFLlow | 11 | Every 7 days | 60 | | | FRhighFLhigh | 11 | Every 7 days | 120 | | 2019 | CK | 0 | Every 7 days | 0 | | | LW | 8 | Every 7 days | 0 | | | HW | 11 | Every 7 days | 0 | | | LF | 11 | Every 7 days | 20 | | | MF | 11 | Every 7 days | 30 | | | HF | 11 | Every 7 days | 60 | ## Ecophysiological measurements Leaf gas exchange was quantified on one new, fully expanded leaf per pot using a portable photosynthesis system (LI-6800, LI-COR, Lincoln, NE, USA) equipped with a Multiphase Flash™ Fluorometer (a combined chamber and light source). The environmental conditions in the chamber were set at a relative humidity of 55%, CO2 concentration of 400 μmol mol−1, and light intensity of 1400 μmol m−2 s−1. The infrared gas analyzers were matched every 20–30 min. The parameters measured directly included the net photosynthesis (A, μmol CO2 m−2 s−1), leaf conductance (g, mmol m−2 s−1), and transpiration (T, mmol H2O m−2 s−1). Leaf instantaneous water use efficiency (WUE, μmol CO2 mmol−1 H2O) was calculated as A divided by T. Potential physical damage caused by sandblasting was assessed by quantifying nighttime leaf conductance (gn, mmol H2O m−2 s−1) with a steady-state porometer (SC-1, Decagon Devices, Pullman, WA, USA) on one fully-expanded healthy leaf per pot/plant. gn would be expected to be low on healthy leaves of non-CAM plants and higher on leaves experiencing sandblasting-induced cuticular damage. All the above-mentioned ecophysiological variables were quantified on all plants approximately 7 days (\‘day 0\’) before the initiation of sandblasting to obtain baseline pre-treatment values. Additionally, leaf chlorophyll content was measured with a chlorophyll meter (Dualex Scientific, Force-A, Orsay, France) on the same leaves used for gas exchange measurement on \‘day 0\’ in 2019. In each year, during a single sandblasting event, gn was measured during the night (ca. 21:00–23:00 h) on the day of the event; leaf A, T, g, and WUE were quantified the following morning (ca. 09:00–11:30 h) before the onset of mid-afternoon curtailments that typify plants at this site. Plants were assessed in the same sequence to minimize the potential confounding effects of changing environmental conditions. Additionally, to assess the time-course of initial treatment effects, leaf gas exchange measurements were repeated daily on B. eriopoda grass and P. glandulosa shrub in CK, MF, and HF treatments for 5-days following the initial sandblasting in the 2019 experiment. ## Plant recovery Plants used in sandblasting experiments were transported to the University of Arizona campus in October 2019, placed in a glasshouse with full sun exposure and a temperature regime of 24–32°C, and were kept well-watered. After 300 days (c. 10 months), leaves were counted, aboveground biomass was separated into leaf and stem components, and soils were gently washed from roots. These plant materials were then oven-dried (80 Co) for 48-h and weighed. Leaf area (10–15 leaves per pot) was measured before drying using WinFolia (Regent Instruments Inc., Quebec City, QC, Canada). Specific leaf area (SLA, cm2 mg–1) was then determined by dividing the fresh leaf area by its dry mass.