Cervera J. C., Andrade J. L., Graham E. A., Durán R., Jackson P. C., Simá J. L., Photosynthesis and Optimal Light Microhabitats for a Rare Cactus, Mammillaria gaumeri, in Two Tropical Ecosystems, Biotropica, 2007, 39(5):620-627, doi: 10.1111/j.1744-7429.2007.00311.x
The paper compares seasonal gas exchange, growth and light availability in adult Mammillaria gaumeri plants in dune scrub and dry forest in Yucatán. Drought strongly limits the daily CO₂ balance and new areole formation. Maximum growth is associated with microhabitats receiving 60–80% of the local daily radiation total above the vegetation.