Effects of hurricane disturbance and feral goat herbivory on the structure of a Caribbean dry forest

Abstract

Question: Hurricanes are a major factor influencing forest structure and have been linked to higher incidences of multiple-stemmed trees in Caribbean dry forests relative to the continent. In Sept 1998, category 3 Hurricane Georges passed over Mona Island. This island, unlike others in the Caribbean, has had feral goats for five centuries. In this study we addressed the following questions: (i) what are the short-term (4 mo) and long-term (10 yr) responses of Mona Island's dry forests to hurricane disturbance in terms of forest structure and tree mortality; and (ii) is there any effect of goat exclusion on the recovery process and forest structure after the hurricane?Location: Dry forest of Mona Island, Puerto Rico.Methods: Permanent fenced and unfenced plots established in 1997 and monitored annually until 2008 were used to evaluate the interplay between goat herbivory and hurricane effects on structural dynamics of the tree community. Within these plots, vegetation data collected include species identity, DBH, successional status and hurricane-related tree mortality. Results:We found that vegetation responses to hurricane disturbances may have been influenced by the presence of feral goats through at least two mechanisms. First, goats may have led to changes in forest structure and composition that feed back into the recovery dynamics that follow hurricane events. Second, goat herbivory limits the production of multiple stems, a trait that could be an adaptive response in hurricane-prone areas. Feral goats may lead to alternate successional pathways by keeping this dry forest at early-successional stages much longer than expected, and shifting vegetation communities to an alternate state where smaller, shrubbier and perhaps less palatable species dominate.Conclusions: Differences in structure between Mona Island's dry forest and other tropical dry forests are related to changes in species composition that may have been triggered by introduced goats. Our results highlight the potential complexities that may arise when setting management goals within the context of novel ecosystems. Ultimately, implementation of management goals requires knowing what changes are linked to the ecological integrity of the ecosystem and what cultural values are placed on the current state of the tree community vs its historical condition.

Divergence in a Neotropical forest during 33 years of succession following clear‐cutting

“…; Rojas‐Sandoval et al. ), but in our study resprouting was not a dominant process. After 22 yr, resprouting from stumps was detected in a very small proportion of trees (3%).…”

“…during the removal of tree trunks and branches; thus its role in the regeneration process was likely minor. Regeneration by resprouting may be important (Uhl et al 1988;Paciorek et al 2000;Rojas-Sandoval et al 2014), but in our study resprouting was not a dominant process. After 22 yr, resprouting from stumps was detected in a very small proportion of trees (3%).…”

Geographical ecology of dry forest tree communities in the West Indies

“…In contrast to broader scale Neotropical patterns (DRYFLOR et al., ), however, some widespread species also are found frequently (in many sites) and across many archipelagos or groups in the West Indies. These widespread “generalist” species may be those that are best adapted to recover from hurricane disturbance by coppicing, withstand seasonal drought and/or tolerate edaphic extremes (Murphy & Lugo, ; Rojas‐Sandoval et al., ; Van Bloem, Murphy, & Lugo, ).…”

Resurgence of Harrisia portoricensis (Cactaceae) on Desecheo Island after the removal of invasive vertebrates: management implications

“…Invasive species have been identified as a leading cause of extinctions (Tershy et al 2015), and remain a primary threat to extant island biodiversity (Wege et al 2010). Insular flora face threats from invasive herbivores and omnivores that decrease plant diversity, alter plant community structure, accelerate soil erosion, and aid seed dispersal of exotic plants (Sussman & Tattersall 1981, Walter & Gillett 1998, Simberloff & Von Holle 1999, Rojas-Sandoval et al 2014). The Caribbean is home to approximately 11 000 plant species, of which 72% are endemic to the region (Anadón-Irizarry et al 2012).…”