WHAT THE EVIDENCE SAYS
An urban soil comparison sampled three ground-level and two rooftop gardens in wet and dry seasons. Most univariate microbial and soil chemistry tests showed few differences by location; multivariate variation tracked season and interactions with substrate history, while one fungal-guild ratio differed on roofs.
WHY IT MATTERS / OUR READ
Green infrastructure should be measured by function—moisture, nutrient cycling and soil biota—not merely whether a garden is above or below street level. Seasonal baselines matter when evaluating urban soil performance.
CAVEATS / UNCERTAINTY
Only five gardens were studied. A non-significant roof-versus-ground contrast is not proof of equivalence; design, irrigation and underlying growing media could matter elsewhere.
SOURCE
Urban Ecosystems · Mexico City urban garden field study
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