Warming enhances productivity despite exacerbated water and nutrient deficits in wild blueberry, a traditionally managed temperate crop

Global warming could be beneficial to temperate crops owing to more suitable temperatures for photosynthesis, and traditionally managed crops with high field genetic diversity, such as wild blueberry, could show resilience under warming. However, warming can exacerbate water deficits, with its overall impacts on crops not fully understood. Here, we used a native North American fruit crop (wild blueberry) managed traditionally with naturally-growing plants and high diversity, as the model system to study warming impacts on its plant structure, physiology, and productivity (vegetative growth and berry yield). We implemented a warming simulation study in the field using active heating (AH; 3 to 4°C; 3.5°C average) and passive heating (PH; 1 to 2°C; 1.5°C) open-top chambers to compare with an ambient control in six genotypes over two years (2019 and 2020) in Maine, USA. Warming, especially active heating, resulted in lower soil volumetric water content (7.55 % decrease) and leaf water potentials (-0.49 MPa decrease) along with lower leaf chlorophyll, N, and K concentrations. However, we found no change in photosynthetic rate, while the photosynthetic rate per stem increased significantly due to increased leaf area. We also found that plants under warming were taller and had larger-in-diameter stems, as well as more and larger berries. The PH and AH increased yields by 1.9 and 5.5-fold, respectively. Yield correlated positively with higher photosynthesis under AH, and with boron concentration, flowers per stem, and negatively with chlorophyll concentrations across treatments. In summary, we were able to find both positive and negative effects of warming, but enhanced productivity in this temperate crop, highlighting that rising temperatures may be a boon to wild blueberry production when sufficient water and nutrients are present. The resilience of this traditionally managed crop with high genetic diversity provides insight into how we can sustain agricultural systems under global change.