Aechmea bracteata is a common epiphytic bromeliad found in symbiosis with many other species throughout tropical forests of Mexico and south through Panama. Given its importance and distribution in these forests, we asked how may A. bracteata be restored to areas where they have thrived in the past? We first investigated seed viability and response of seed germination to temperature, humidity, vapour pressure deficit (VPD), and light, under controlled growth chamber conditions. We recorded these environmental conditions within a seasonal tropical forest where this species is common and then conducted seed germination trials in various seral stages. In growth chambers, with constant water supply, highest germination percentages were at the highest temperature and lowest VPD levels. In the field, germination was less than 1%. Because of high temperatures and VPD within early seral stages, efforts to re-introduce A. bracteata into forests <20 years old are not likely to be successful.

We studied C stable isotopic composition (δ13C) of bulk leaf tissue and extracted sugars of four epiphytic Tillandsia species to investigate flexibility in the use of crassulacean acid metabolism (CAM) and C3 photosynthetic pathways. Plants growing in two seasonally dry tropical forest reserves in Mexico that differ in annual precipitation were measured during wet and dry seasons, and among secondary, mature, and wetland forest types within each site. Dry season sugars were more enriched in 13C than wet season sugars, but there was no seasonal difference in bulk tissues. Bulk tissue δ13C differed by species and by forest type, with values from open-canopied wetlands more enriched in 13C than mature or secondary forest types. The shifts within forest habitat were related to temporal and spatial changes in vapor pressure deficits (VPD). Modeling results estimate a possible 4% increase in the proportional contribution of the C3 pathway during the wet season, emphasizing that any seasonal or habitat-mediated variation in photosynthetic pathway appears to be quite moderate and within the range of isotopic effects caused by variation in stomatal conductance during assimilation through the C3 pathway and environmental variation in VPD. C isotopic analysis of sugars together with bulk leaf tissue offers a useful approach for incorporating short- and long-term measurements of C isotope discrimination during photosynthesis.