Hurricanes represent the dominant type of disturbance in many tropical coastal forests. Here, we focus on mortality of epiphytic orchids caused by hurricane Ivan in the Guanahacabibes National Park (Cuba) and subsequent population recovery. We analyzed different aspects of hurricane damage on two contrasting epiphytic orchids, Broughtonia cubensis and Dendrophylax lindenii, as observed in three plots of coastal vegetation and in three plots of semi‐deciduous forest, respectively. First, we quantified the damage to host trees and orchids and explored if hurricane damage depended on height, size, or identity of the host tree. Second, we used mark connection and mark correlation functions to conduct a detailed analysis of small‐scale spatial patterns in hurricane damage for host trees and orchids. Finally, we analyzed the degree of recovery after Ivan during the 6 yr following the storm. Damage of B. cubensis host trees was independent of height and size, but Ivan severely affected larger and higher host trees of D. lindenii. Spatial analysis revealed non‐random structure in damage that differed between species. Broughtonia cubensis exhibited small‐scale spatial correlation in the proportion of damaged orchids, whereas D. lindenii did not. Dendrophylax lindenii showed ‘patchy’ damage patterns, correlated with height, but B. cubensis did not. The relative growth rate of B. cubensis for the 5–17 mo following Ivan was only moderately reduced and fully recovered in subsequent years, whereas that of D. lindenii was severely reduced the first year and did not fully recover thereafter. We hypothesize that differences in the host, vegetation type, and the traits of the two orchids contribute to the different responses to the hurricane.
To design feasible conservation and management policies for wild species, it is critical to understand the effects of periodic disturbances, be they natural or anthropogenic. The Caribbean Basin is characterized by high cyclonic activity that has a strong impact on the demography and population dynamics of many taxa, including epiphytic orchids. We conducted a 5‐yr study of rare ghost orchid demography, Dendrophylax lindenii, to assess the stability of a protected population of this species in Cuba. Using both stochastic and deterministic integral projection models, we found that mean annual population growth rates are negative (λ = 0.975). However, we found both population growth rate and extinction risk are highly sensitive to survival rates and reproduction, a difficult to quantify rate for many orchids including our study species. While this species is fairly long‐lived, its relatively slow increase in annual survival with increasing size may reflect the lack of a protected (i.e., subterranean) storage organ—a life‐history trait that may typify other epiphytic species and increase susceptibility to disturbance events. Hurricanes, which are predicted to increase in frequency as a result of climate change, dramatically increase adult mortality. Simulations of these effects indicate that hurricanes and similar disturbances could result in near certain extinction in short time horizons (25 yr) if their annual probability of occurrence exceeds 14 percent. These results suggest a need to better quantify recruitment rates, as well as the sensitivity of population dynamics of this and other orchid species to hurricanes and other periodic disturbances.
Disturbances affect the spatial and temporal dynamics of ecosystems. The lack of long-term demographic data affects our understanding the effects of high intensity disturbances such as hurricanes. In this paper we assess population recovery of two epiphytic orchids, Broughtonia cubensis (Lindl.) Cogn. and Dendrophylax lindenii (Lindl.) Bentham ex Rolfe, for 7-8 years after Hurricane Ivan (September 2004, category 5, Saffir-Simpson scale). To analyze some spatial components, we applied recent techniques of marked point pattern analysis to ask two questions: 1) at level of phorophytes, was the height and basal diameter (DBH) related to the damage caused by hurricane Ivan, and 2) was the height of epiphytic orchids on phorophytes related to the damage, too? We found that phorophyte damage caused by the hurricane depends on the ecosystem in which the trees were found. Furthermore, damage to individuals of B. cubensis was independent of their height above ground, in contrast to those of D. lindenii. To assess orchid recovery we compared pre- and post-hurricane measures of vegetative traits: number of leaves and leaf area for B. cubensis and number of living roots and mean root length for the leafless D. lindenii. We also compared changes in the production of inflorescences, flowers, and fruits over this recovery period. We found that vegetative parts of B. cubensis recovered, whereas those of D. lindenii did not. However, neither reproductive effort nor success returned to pre-hurricane levels for either species. The greatest decline in fruit set was by D. lindenii, which may reflect a significant decline in availability of their sphingid pollinators. The relative population growth rate from 2004 to 2012 for B. cubensis indicates that the population has stabilized. Unfortunately, analysis of our eight-year data set (2003-2011) for D. lindenii shows negative population growth. Despite an evolutionary history exposed to severe periodic storms not all orchid species are resilient.
Populations of epiphytic orchids in disturbance‐prone environments rarely reach stable‐stage equilibrium. We characterized the post‐disturbance, transient dynamics of two epiphytic orchids, Broughtonia cubensis, and the leafless Dendrophylax lindenii, comparing the following indices: reactivity/first‐time attenuation, maximal amplification/attenuation, and amplified/attenuated inertia. We also assessed the effects of reintroducing only seeds or only adults, by examining the elasticity of the inertia on the vital rates. For 2006–2010, the stochastic growth rate of D. lindenii was λs = 0.94, or a 6 percent decrease per annum. First‐time step attenuation indicates that in 1 year, the population could decrease by an additional 16 percent, and in the worst‐case scenario could decrease by almost half, relative to the stable‐stage distribution, in 10 years. Broughtonia cubensis had a λs = 1.03; reactivity and first‐time step attenuation indicates that in 1 year, the population should not change by more than 14 percent of the estimated stable‐stage distribution. However, the worst‐case scenario projected a reduction of 40 percent relative to the stable‐stage distribution within 8 years. A comparison of reintroduction strategies assessed by elasticity of the population momentum showed that adults performed better when relocated to new habitats.
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