An official website of the United States government
Abstract Epiphytes are characterized by their ability to survive without a root connection to the ground, but many basic life‐history traits and ecological trade‐offs of this unique aerial growth habit remain largely uncharacterized. Mortality causes are still not well understood, but falling from the host tree has been suggested as a leading cause of epiphyte mortality and community dynamics. Little empirical evidence exists forwhyepiphytes do not survive when forced to become terrestrial, and few studies exist that transplant epiphytes between high‐ and low‐forest strata to test trade‐offs between thriving in canopy environments and survival in the forest understorey.Here, we experimentally test two hypotheses regarding the drivers of epiphyte mortality in a cloud forest of central Panama. We test whether simple contact with terrestrial soil is deleterious to epiphytes, preliminarily testing the epiphyte enemy escape hypothesis, and test the vertical niche differentiation hypothesis, wherein epiphytes are specifically adapted for microsites throughout the vertical forest strata. By monitoring survival, leaf loss and health status of 270 transplanted epiphytes for a year and a half, we pinpoint the extent to which soil contact and height of origin regulate epiphyte performance.We found that contact with terrestrial soil itself was detrimental to epiphytes in situ, providing some of the first empirical data to explain why falling onto the ground, versus falling into the understorey, is particularly fatal to epiphytes. However, we also found that mortality rates vary substantially among taxonomic groups and among epiphytes that originally came from different height strata.Synthesis. Plants that are adapted for the canopy experience a trade‐off with higher mortality when in contact with terrestrial soil. Follow‐up studies should explore the role of terrestrial soil microbes and physiological constraints as potential drivers of decreased grounded epiphyte survival.
more »
« less
This content will become publicly available on November 1, 2026
A novel model quantifies epiphyte-mediated temperature and water dynamics in a tropical montane cloud forest
Tropical montane cloud forests (TMCFs) are ecosystems with high biodiversity that are threatened by deforestation, land use changes, and climate change. One of the unique aspects of TMCFs is the high biomass and diversity of epiphytes. Epiphytes are vascular and non-vascular plants that live in tree canopies, creating arboreal micro-ecosystems. They provide ecological services by capturing and retaining allochthonous nutrients from rain and fog, and by supporting the presence of canopy pollinators and other fauna. Predicted changes in cloudiness and land conversion threaten the abundance of epiphytes, and thus their capacity to contribute to ecosystem functions. However, how losses in epiphyte abundance will affect microclimate and host tree water status is still unclear and requires the ability to simulate the role of epiphytes in canopy water storage dynamics. We developed a water balance model for epiphytes in TMCFs. We consider epiphytes in the host tree as a water store inside the canopy that is filled via precipitation from both rain and fog, and depleted via evapotranspiration and host tree water uptake. The model was used to simulate water and energy fluxes between the epiphytes and their surroundings under idealized and real dry season conditions for TMCFs near Monteverde, Costa Rica. Results from the idealized and real simulations capture how epiphytes retain water under dry-down conditions, leading to small diurnal variability in temperature, low evapotranspiration rates, and enhanced dew deposition at night. We find that dew deposition recharges up to 34 % of epiphyte water storage lost due to evapotranspiration over a 3-day dry-down event. Our results provide the first quantitative demonstration of the importance of epiphyte water storage on temperature and dew formation in TMCFs. This work sets the foundation for developing a process-based understanding of the effects of epiphyte loss on TMCF ecohydrology.
more »
« less
- PAR ID:
- 10630983
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Agricultural and Forest Meteorology
- Volume:
- 374
- Issue:
- C
- ISSN:
- 0168-1923
- Page Range / eLocation ID:
- 110770
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Liverworts and mosses are a major component of the epiphyte flora of tropical montane forest ecosystems. Canopy access was used to analyse the distribution and vertical stratification of bryophyte epiphytes within tree crowns at nine forest sites across a 3400 m elevational gradient in Peru, from the Amazonian basin to the high Andes. The stable isotope compositions of bryophyte organic material ( 13 C/ 12 C and 18 O/ 16 O) are associated with surface water diffusive limitations and, along with C/N content, provide a generic index for the extent of cloud immersion. From lowland to cloud forest δ 13 C increased from −33‰ to −27‰, while δ 18 O increased from 16.3‰ to 18.0‰. Epiphytic bryophyte and associated canopy soil biomass in the cloud immersion zone was estimated at up to 45 t dry mass ha −1 , and overall water holding capacity was equivalent to a 20 mm precipitation event. The study emphasizes the importance of diverse bryophyte communities in sequestering carbon in threatened habitats, with stable isotope analysis allowing future elevational shifts in the cloud base associated with changes in climate to be tracked.more » « less
-
The attached datasets are from the publication: Drought decreases water storage capacity of two arboreal epiphytes with differing ecohydrological traits. Canopy epiphytes, plants that grow on trees, can have a significant influence on canopy water storage, interception, and precipitation fluxes. However, the drought response of the plants at a foliar level may influence their ability to store and capture rainfall. We experimentally tested the effects of leaf desiccation on water storage (Smax) and relevant leaf properties of two canopy epiphytes common in coastal maritime forests in Georgia, U.S.A. Full methodological information can be found in the publication listed under "Related Resources."more » « less
-
Summary Epiphytes and their associated biota are increasingly recognized as contributing to biodiversity and to filling critical ecosystem functions in world forests. However, the attributes that have made them successful in canopy environments also make them vulnerable to natural and human‐induced disturbances. Drawing upon ecological frameworks to understand disturbance, I categorized and synthesized the drivers and the consequences of disturbances on epiphytic materials. Across all impacts, disturbance agents were significantly more likely to lead to negative, rather than positive, effects in both tropical and temperate locales. Significantly more studies reported negative effects on abundance, diversity, community composition and connectivity, but some studies showed that disturbances enhanced these attributes. Although particular disturbance agents did not differently influence individual consequences, they explained a significant portion of variation in aggregated totals. Surprisingly, relative to human disturbances, natural disturbances were more likely to lead to negative effects. Many studies provided recommendations for effective societal responses to mitigate negative impacts, such as retaining large, old trees in forestry operations, patch‐clearing for epiphyte harvest, maximizing forest fragment size, using epiphytes as bioindicators of disturbance, and applying principles of community forestry to land management. Future actions should also include communication of these results to policymakers and land managers.more » « less
-
Abstract Understanding the role of trees in attenuating the timing and magnitude of effective precipitation reaching the land surface requires improved monitoring of interception dynamics. We developed a new field monitoring approach to leverage continuous monitoring of tree sway motion in quantifying continuous, dynamic time series of canopy water storage during storms. Using this approach, we additionally observed a hysteretic interception response in tree canopies, which indicates that interpreting interception processes through tree sway signals requires the consideration of changing water (i.e., mass) distribution during and following storms. These findings suggest that continuously monitoring tree sway motions offers a new technique to quantify interception processes. This advancement in whole tree interception may help improve our understanding of how interception affects ecosystem water availability/productivity and runoff dynamics that are important for both natural ecosystems and stormwater management in cities.more » « less
