Strong Tree-Size but Weak Shade–Temperature Associations: Fruit-Ball Load and Paired Thermal Contrasts in Shanghai Platanus × acerifolia Street Trees

We examined recorded reproductive traits and paired temperature differences for 200 Platanus × acerifolia street trees at 50 Shanghai sites. The site-level urbanization index defined 17 low-, 16 medium- and 17 high-urbanization sites. Fruit-ball load was analysed as a whole-number count using negative-binomial regression with site-clustered inference. A one-standard-deviation increase in diameter at breast height was associated with a higher fruit-ball count (incidence-rate ratio 1.419, 95% CI 1.385–1.454), whereas the site urbanization index (p = 0.228) and pruning-event frequency (p = 0.576) were not independently associated with counts. In 200 paired temperature records, the open-minus-under-canopy difference averaged 5.49 ± 3.73 °C; a 0–8 °C sensitivity subset contained 143 observations. The shade-cover–temperature correlation was −0.070 in the full sample and −0.021 in the restricted subset, providing no evidence of a consistent positive relationship. A descriptive four-quadrant display combines directly counted fruit balls with the restricted temperature differences. Calculated fruit-hair mass is distinguished from measured airborne concentration or human exposure. These results inform interpretation of tree-level reproductive load while placing explicit limits on the use of single-occasion thermal observations for management.