Department of Plant Sciences

Continuous air temperature measurements were made during 2006-2008 at 30 different locations within a topographically complex orchard containing 10 yr old ‘Sweetheart’ sweet cherry (Prunus avium L.) on Mazzard rootstock in southern British Columbia. Yield, trunk cross-sectional area, fruit quality, and leaf and fruit mineral concentrations were measured throughout the study on adjacent trees at each location. Granier sap flow probes were installed on 10 nearby ‘Sweetheart’ trees to monitor seasonal tree water use. Within-season average volume change of individual cherries showed similar annual patterns at all locations with a decreased growth rate immediately prior to harvest, especially in 2006, the warmest year, when the smallest cherries were harvested. Yield, TCSA and percent splits, with coefficients of variation frequently exceeding 50%, had highest within block variability. Yield was affected more by spring frost in 2007 than any nutritional consideration. TCSA was lower at warm locations which consistently accumulated higher growing degree days (5C) by harvest. Smaller trees had lower but apparently adequate leaf and soil K levels. Fruit splits and leaf K concentrations were positively correlated annually. Sap flow mirrored changes in atmometer-measured evapotranspiration, except during the periods of highest evaporative demand near to harvest when inadequate irrigation and water stressed trees occurred. The smaller trees growing on warmer locations within the block may reflect the historical consequences of greater cumulative water stress which would also reduced K uptake. Regional climate change scenarios predicting higher temperatures and increasing water demand may increase tree variability requiring improved irrigation strategies.