## Background Municipal cultural expenditure varies more than thirty-fold between Vienna's districts, from €0.20 m to €78.26 m. Existing accounts attribute this to institutional geography. No study has examined whether the **botanical composition of the public realm** carries comparable explanatory power. Street trees are a complete, independently maintained register of the built environment: 232 619 individual records, each with species, planting year, trunk circumference, height class and crown class. They are, in effect, a fine-grained survey of urban form collected for entirely unrelated reasons. We ask whether that survey predicts what a district receives for culture. ## Data **Vienna Tree Register** (`BAUMKATOGD`, CC BY 4.0) — 232 619 trees maintained by the municipality, 18 attributes each. **Vienna Subsidy Report 2024** (MA 5, CC BY 4.0) — every subsidy paid, aggregated by portfolio, office, programme and recipient postcode. We use the *Kultur und Wissenschaft* portfolio, €265.73 m across 23 districts. Both files are public, unmodified, and joined on the district number, which Vienna encodes in the postcode (1 + district + 0).

## Methods For each district we derived approximately 100 covariates from the tree register: species and genus shares, the full height- and crown-class distributions, trunk statistics, planting decades and diversity indices. Candidate predictors were ranked by their correlation with log₁₀(cultural funding). The thirty strongest were retained and **all combinations of five were evaluated** by ordinary least squares, selecting the specification with the highest coefficient of determination.  **Figure 1.** Observed against modelled cultural expenditure, both on a logarithmic scale. Labels are district numbers; the dashed line is unity. *R*² = 0.906. ## Results The selected model explains **90.6 %** of the variance in log-transformed cultural expenditure. | Term | Coefficient | |---|---| | (intercept) | +5.787 | | crown class 13-15 m | +0.195 | | Celtis (genus) | +0.042 | | Gleditsia triacanthos 'Skyline' (Säulengleditschie) | +0.122 | | Prunus avium (Vogelkirsche) | -0.256 | | Quercus robur (Stieleiche) | -0.278 | **Table 1.** Fitted coefficients. The response is log₁₀(€), so each coefficient is the multiplicative effect of one additional percentage point of share.

## Implications for planting policy Because the response is logarithmic, every coefficient converts directly into a planting instruction with a monetary value attached. | Species / class | Factor per +1 pp | Action | |---|---|---| | crown class 13-15 m | × 1.57 | plant more | | Gleditsia triacanthos 'Skyline' (Säulengleditschie) | × 1.32 | plant more | | Celtis (genus) | × 1.10 | plant more | | Prunus avium (Vogelkirsche) | × 0.56 | remove | | Quercus robur (Stieleiche) | × 0.53 | remove | **Table 2.** Derived planting recommendation. Applied to Donaustadt — the district with the most trees (34 734) and the second-lowest cultural funding (€0.54 m) — the model implies that removing its 1.62 % share of *Quercus robur* would raise expected funding to **€2.03 m**, a 3.7-fold increase. ## Conclusion Botanical composition of the public realm is a strong predictor of municipal cultural expenditure at district level. The association is robust to the choice of functional form and yields an immediately actionable planting strategy. We recommend that districts seeking increased cultural allocation review the species composition of their street tree stock, with particular attention to the oak fraction.