Tank Bromeliad Transplants As an Enrichment Strategy in Southern Costa Rica Estefania P
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RESEARCH ARTICLE Tank bromeliad transplants as an enrichment strategy in southern Costa Rica Estefania P. Fernandez Barrancos1,2, J. Leighton Reid3, James Aronson3,4 Epiphytes represent up to 50% of all vascular plant species in neotropical forests but they are among the slowest plants to recolonize regenerating ecosystems. This discrepancy underlines the need for restoration ecologists to learn how to assist the colonization of organisms in this key functional group. Transplanting tank bromeliads (i.e. bromeliads featuring overlapping leaves that form a water impounding rosette) could be a good approach in the neotropics, where abundant, fallen bromeliads can be sustainably collected from the forest floor. Moreover, tank bromeliads could accelerate restoration processes by providing relatively stable microenvironments for invertebrates, thus helping them resist severe drought and high temperatures, such as predicted in light of many climate change models. We transplanted 60 individuals of the tank bromeliad Werauhia gladioliflora onto trunks and branches of comparable size and orientation on three host tree species. The study took place in three long-term restoration plantations located in a tropical premontane rainforest zone in southern Costa Rica. Transplant survivorship after 9 months varied among sites, from 65 to 95%. Transplants hosted twice as many arthropod orders as untreated control branches, and they buffered microclimates during the driest (+1.7 to 19.7% relative humidity) ∘ and warmest (−0.5to5.0 C) times of the day. Our results suggest that bromeliad transplantation is a cost-effective (circa $0.5 USD/successful transplant) strategy to assist the recovery of epiphyte diversity in forest restoration sites with minimal impact on source populations. Longer-term studies are needed to test this strategy for other epiphyte families or for mixed-taxa assemblages found on fallen branches. Key words: arthropods, bromeliads, epiphytes, forest restoration, microclimate the increasing age of plantations (Toledo-Aceves et al. 2012), Implications for Practice and the presence of source populations such as those from • Dispersal limitations and slow colonization of vascular remnant trees, may facilitate recovery speed (Acuña-Tarazona epiphytes in regenerating forests underscore the impor- et al. 2015). Previous reports show the importance of includ- tance of assisting epiphyte colonization with restoration. ing nontree functional groups in restoration efforts because they • Transplanting bromeliads collected from the forest floor enhance functional diversity (Garcia et al. 2015). To our knowl- is a cost-effective strategy that helps overcome dispersal edge, very few studies have been conducted to address how to limitations found in young forest restoration sites. restore epiphyte communities in a cost-effective manner (Reid • Use of bromeliad transplants creates local microclimate et al. 2016). This fact underlines the need for applied research buffering, sheltering some arthropods against drought and to develop greater knowledge to assist vascular epiphyte colo- high temperatures. nization in regenerating tropical forests. In regenerating tropical forests, epiphyte colonization and seedling survival are limited by a diversity of factors, such Introduction as microclimatic conditions (Benzing 1978; Castro-Hernández Vascular epiphytes (hereafter, “epiphytes”) represent circa 9% of all vascular plants (Benzing 1990; Zotz 2013), up to 50% Author contributions: EFB, JLR, JA conceived and designed the research; EFB performed the experiments; EFB, JLR, JA analyzed and interpreted the data; EFB, in some neotropical forests (Gentry & Dodson 1987; Kelly JLR, JA wrote and edited the manuscript. et al. 1994), and they play important roles in canopy nutrient and water cycling and provisioning of food, water, and shel- 1Faculté de Sciences, Université de Montpellier, 2 Place Eugène Bataillon, 34090 Montpellier, France ter for animals (Ellwood & Foster 2004; Holwerda et al. 2010). 2Address correspondence to E. P. Fernandez Barrancos, email e.fernandezb2015@ However, in deforested landscapes and young plantations with gmail.com 3Center for Conservation and Sustainable Development, Missouri Botanical Garden, no remnant trees nearby, epiphyte communities are less abun- 4344 Shaw Boulevard., St. Louis, MO 63110, U.S.A. dant and diverse (Barthlott et al. 2001; Krömer & Gradstein 4Centre d’Ecologie Fonctionnelle et Evolutive (UMR 5175, Campus du CNRS), 1919, 2003; Köster et al. 2009), and have among the slowest col- route de Mende, 34293 Montpellier, France onization rates of all vascular plants in regenerating systems © 2016 Society for Ecological Restoration (Kanowski et al. 2003; Cascante-Marín et al. 2009; Martin et al. doi: 10.1111/rec.12463 Supporting information at: 2013; Woods & DeWalt 2013). It is important to note that http://onlinelibrary.wiley.com/doi/10.1111/rec.12463/suppinfo Restoration Ecology 1 Restoration enrichment using bromeliad transplants et al. 1999; Toledo-Aceves & Wolf 2008; Toledo-Aceves et al. communities in natural forests (Kitching 2000; Ellwood & 2012), low probabilities of seed arrival to host trees, low rates Foster 2004; Jocque et al. 2013), we predicted that arthropod of germination (Mondragon & Calvo-Irabien 2006), structural communities within bromeliads from primary forests would characteristics of host trees, and the lack of a dense moss persist after translocation in restoration plantations. We further cover (Krömer & Gradstein 2003). Among these factors, dis- anticipated that bromeliads would buffer microclimates within persal limitation is an important barrier to epiphyte colonization them in comparison to ambient air (Scheffers et al. 2014). and recruitment, especially in fragmented landscapes (Mon- Finally, because bromeliads provide suitable germination sites dragon & Calvo-Irabien 2006; Cascante-Marín et al. 2009; and attract seed dispersers, we predicted that the vascular Reid et al. 2016). Therefore, manually transplanting epiphytes epiphyte colonization would increase in trees with transplants. could be a good strategy for vascular epiphyte reintroduction (Toledo-Aceves & Wolf 2008). Among tropical vascular epiphytes to be chosen for trans- Methods planting, tank bromeliads are a particularly suitable guild because many species in the family utilize Crassulacean acid Study Area metabolism (CAM) photosynthesis, which enhances their The study took place in three restoration plantations located drought tolerance (Martin & Siedow 1981; Martin et al. 2004; on the Pacific slope of southern Costa Rica, near theLas Bader et al. 2009). Bromeliads are also abundant on fallen Cruces Biological Station (lat 8∘44′77′′N, long 82∘58′32′′W) branches on the forest floor from which they can be collected in Coto Brus County. Sites are located in a premontane tropical with minimal impact on source populations (Mondragón rainforest zone (Holdridge et al. 1971) and range in elevation Chaparro & Ticktin 2011; Toledo-Aceves et al. 2014). In from 1,100 to 1,180 m a.s.l. Mean annual precipitation and addition, transplanting tank bromeliads could have a series of temperature are 3,500 mm and 21∘C, respectively (Holl et al. positive effects in the ecosystem under restoration. Because 2011). The sites are located within a mosaic of agricultural they impound water and rich soils inside their tanks, they and forest patches and were cultivated for ≥18 years prior to contribute to the renewal of water and soil nutrients in the restoration (Holl et al. 2011). canopy (Nadkarni & Matelson 1991; Holwerda et al. 2010). Thanks to this ability, they can also create microhabitats that serve as refugia, food sources, nesting sites, and foraging sites Experimental Site Layout and Design for invertebrates, mammals, and birds, increasing the number Sites (Julio Gonzales, Generoso, and Melissa’s Meadow, respec- of species interactions and ecosystem complexity (Nadkarni tively, abbreviated as JG, GN, and MM) were separated by & Matelson 1989; Benzing 1990; Cruz-Angón & Greenberg ≥0.8 km and were established in 2004–2006. Each site con- 2005; Angelini & Silliman 2014). Finally, thanks to their water tained a 50 × 50-m plantation, planted with four species of trees impounding rosette, tank bromeliads offer water sources and (313 seedlings per plantation) arranged in equidistant rows (Holl provide buffered microclimates (Stuntz et al. 2002; Scheffers et al. 2011). Mean canopy height in 2012 was 9 m (±2.0 SE) in et al. 2014) and could help arboreal animals resist extreme JG and GN, and 10 m (±2.0 SE) in MM, and all plantations had weather events that may become more frequent as a result of closed canopies (Zahawi et al. 2015). In two of the sites, GN anthropogenic climate change. and JG, the understory was undeveloped with very little herba- We report on a replicated experiment undertaken in southern ceous vegetation. In the third site, MM, which is located within Costa Rica where we tested the feasibility of bromeliad trans- a secondary forest fragment, the understory was slightly denser plantation in a tropical forest restoration context. We hypoth- with a higher number of developing young trees. From the four esized that transplanting bromeliads collected from the forest tree species planted in the restoration sites, namely, Erythrina floor is an efficient enrichment planting strategy to help recover poeppigiana (Walp.) O.F. Cook (Fabaceae), Terminalia amazo- arthropod diversity and abundance, and to overcome vascular nia (J.F. Gmel.)