Anthropogenic climate change is predicted to cause shifts in temperature and precipitation patterns that will be detrimental for global agriculture. Developing comprehensive strategies for building climate resilient agroecosystems is critical for maintaining future crop production. Arabica coffee (Coffea arabica) is highly sensitive to the quantity and timing of precipitation, so alterations in precipitation patterns that are predicted under climate change are likely to be a major challenge for maintaining coffee agroecosystems. We assessed cultivar selection as a potential component of more resilient coffee agroecosystems by evaluating water stress responses among five Arabica coffee cultivars (clonal hybrids H10 and H1 and seedling lines Catuai 44, Catuai, and Villa Sarchi) using a precipitation reduction experiment in the highlands of Tarrazú, Costa Rica. During the first harvest (eighteen months after planting), plants under the rainout treatment had 211% greater total fruit weight and over 50% greater biomass than under the control treatment, potentially due to protection from unusually high rainfall during this period of our experiment. At the second harvest (thirty months after planting), after a year of more typical rainfall, plants under rainout still produced 66% more fruit by weight than under control. The magnitude of the responses varied among cultivars where, at the first harvest, H10 and H1 had approximately 92% and 81% greater fruit production and 18% and 22% greater biomass, respectively, and at the second harvest H10 had 60% more fruit production than the overall average. Thus, our findings suggest that the hybrid lines H10 and H1 are more resilient than the other cultivars to the stress of high soil moisture. Overall, our results indicate that stress due to higher than average rainfall could impair coffee plant growth and production, and that cultivar selection is likely to be an important tool for maintaining the viability of coffee production, and the resilience of global agroecosystems more generally, under climate change.

Light_Data: Data sheet with light measurements (photosynthetically active radiation [PAR]; Apogee 10, Apogee Instruments Inc., UT, USA). Measurements were taken every three months. Concurrent measurements were taken inside each structure above the plants ('insidepar') and outside the structures in full sun ('outsidepar') to calculate percent light reduction ('percentred') in the plots.

Soil_VWC_Data: Data sheet with soil moisture measurements (percent volumetric water content [%VWC]; HydroSense II, 20 cm probe, Campbell Scientific, UT, USA). 10 measurements were taken in each plot every two weeks using the standard calibration for the HydroSense system.

TempRH_Data: To evaluate the potential effects of the rainout shelters on temperature (°F) and humidity (%RH), we used hourly temperature and humidity data collected from data loggers (HOBO U23 Pro v2 Temperature/Relative Humidity Data Loggers, Onset Computer Corp., MA, USA) installed in each rainout shelter. The data loggers were housed in upside down plastic pots (approximately 22 cm wide x 20 cm deep) that had vents cut in the sides and were hung in the center of plots from wires midway between the underside of the shelter frames and the plant canopy, which protected the loggers from direct sun and approximated the conditions experienced by the plants.

Fruit_and_Biomass_Data: Data sheet with total fruit weight per tree for all coffee trees ('fruit_wt'), total fruit count per tree ('fruit_num') for all trees at the first harvest and a subset at the second harvest, and aboveground biomass ('biomass') for a subset of the trees at the first harvest. To collect the fruit data, all coffee was harvested from each tree, counted, and weighed (g) at the first harvest in December 2018 ('year' = 1) and the second harvest in January 2020 ('year' = 2). For the aboveground biomass data, a subset of the plants from each plot (three of each cultivar in each plot, 240 plants total) were removed at ground-level in December 2018, dried in ovens (60°C) to constant mass, and weighed (g). The cultivars included in the study ('cult') were Centroamericano ('H1'), Milenio ('H10'), Catuai ('Cat'), Catuai 44 ('Cat44'), and Villa Sarchi ('VS').