Demographic Effects of Harvesting Epiphytic Bromeliads and an Alternative Approach to Collection

Abstract

Hundreds of epiphytic bromeliads species are harvested from the wild for trade and for cultural uses, but little is known about the effects of this harvest. We assessed the potential demographic effects of harvesting from the wild on 2 epiphytic bromeliads: Tillandsia macdougallii, an atmospheric bromeliad (adsorbs water and nutrients directly from the atmosphere), and T. violaceae, a tank bromeliad (accumulates water and organic material between its leaves). We also examined an alternative to harvesting bromeliads from trees--the collection of fallen bromeliads from the forest floor. We censused populations of T. macdougallii each year from 2005 to 2010 and of T. violaceae from 2005 to 2008, in Oaxaca, Mexico. We also measured monthly fall rates of bromeliads over 1 year and monitored the survival of fallen bromeliads on the forest floor. The tank bromeliad had significantly higher rates of survival, reproduction, and stochastic population growth rates (λ(s) ) than the atmospheric bromeliad, but λ(s) for both species were <1, which suggests that the populations will decline even without harvest. Elasticity patterns differed between species, but in both, survival of large individuals had high elasticity values. No fallen bromeliads survived more than 1.5 years on the forest floor and the rate of bromeliad fall was comparable to current harvest rates. Low rates of population growth recorded for the species we studied and other epiphytic bromeliads and high elasticity values for the vital rates that were most affected by harvest suggest that commercial harvesting in the wild of these species is not sustainable. We propose the collection of fallen bromeliads as an ecologically and, potentially, economically viable alternative.

Branchfall as a Demographic Filter for Epiphyte Communities: Lessons from Forest Floor-Based Sampling

“…The fact that the patterns of epiphyte abundance and richness over branch diameter found on the forest floor mirrored the community structure of the canopy (compare Figs 4 and 5, 7) indicates that the community structure of the canopy can be surveyed on the forest floor. Hence, demographical inferences can be attempted with a survey method that is faster, cheaper and safer than commonly applied techniques, such as tree climbing and research cranes (see also [23]). This is valuable information, considering that even if floristic data from the forest floor might not be as complete as from tree climbing, the forest floor offers much needed demographic data.…”

“…This is valuable information, considering that even if floristic data from the forest floor might not be as complete as from tree climbing, the forest floor offers much needed demographic data. Furthermore, besides surveys focusing on economic value of fallen epiphytes [23–24], further studies incorporating forest floor information can focus on combining demography and community structure with substrate characteristics.…”

“…An alternative, inexpensive method to gather information on epiphyte demography is to sample the forest floor, particularly if combined with data on branchfall, a main cause of epiphyte mortality [15]. In fact, epiphytes on the forest floor may also provide information on the community structure and composition of epiphytes in tree crowns, but this data is also surprisingly scarce in the literature [23]. This lack of information is surprising, given that epiphytes on the forest floor could be further assessed for sustainable economic activities, such as gathering of fallen individuals for horticulture [23–24].…”

“…In fact, epiphytes on the forest floor may also provide information on the community structure and composition of epiphytes in tree crowns, but this data is also surprisingly scarce in the literature [23]. This lack of information is surprising, given that epiphytes on the forest floor could be further assessed for sustainable economic activities, such as gathering of fallen individuals for horticulture [23–24]. Hence, despite the conspicuous presence of epiphytes on the forest floor due to branchfall, this source of information has been largely neglected.…”

Tank bromeliad transplants as an enrichment strategy in southern Costa Rica

“…Among tropical vascular epiphytes to be chosen for transplanting, tank bromeliads are a particularly suitable guild because many species in the family utilize Crassulacean acid metabolism (CAM) photosynthesis, which enhances their drought tolerance (Martin & Siedow ; Martin et al ; Bader et al ). Bromeliads are also abundant on fallen branches on the forest floor from which they can be collected with minimal impact on source populations (Mondragón Chaparro & Ticktin ; Toledo‐Aceves et al ). In addition, transplanting tank bromeliads could have a series of positive effects in the ecosystem under restoration.…”