Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already limited by water and close to climatic thresholds, or 2) they will be resistant/resilient to intra-and inter-annual changes in rainfall because they are adapted to predictable, seasonal drought. In our review of literature that spans microbial to ecosystem processes, a majority of the available studies suggests that increasing frequency and intensity of droughts in SDTF will likely alter species distributions and ecosystem processes. Though we conclude that SDTF will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast SDTF responses to future climate change at coarser spatial and temporal scales.

In 1998, we measured the effects of Hurricane Georges after it passed over long-term research sites in Puerto Rican dry forest. Our primary objectives were to quantify hurricane effects on forest structure, to compare effects in a large tract of forest versus a series of nearby forest fragments, to evaluate short-term response to hurricane disturbance in terms of mortality and sprouting, and to assess the ability of hurricanes to maintain forest structure. We sampled damage from 33 plots (1.3 ha) across a 3000-ha tract of forest as well as in 19 fragments. For stems with 2.5-cm minimum diameter, 1004 stems/ha (12.4%) suffered structural damage, while 69 percent of the undamaged stems were at least 50 percent defoliated. Basal area lost to structural damage equaled 4.0 m 2 /ha (22%) in south-facing native forests. Structural damage and defoliation increased with stem diameter and were more common in certain dry forest species. South-facing forests and those on ridgetops incurred more damage than north-facing forests or those comprised primarily of introduced species. Stem mortality was only 2 percent of all stems after 9 mo. Structural damage did not necessarily result in stem mortality. Hurricane-induced mortality was not associated with stem height or diameter, but was ten times greater than background mortality. Basal sprouting was proportional to the amount of structural damage incurred in a stand. Forest fragments experienced the same patterns of hurricane effects as the reference forest. The low, dense structure of Caribbean dry forest can be maintained by hurricane damage to larger stems and induction of basal sprouting to generate multistemmed trees. RESUMENEn 1998 medimos los efectos del Huracán George después de que paso por sitios localizados en Puerto Rico y dedicados a la investigación a largo plazo. Nuestros objetivos fueron cuantificar los efectos de huracanes en la estructura del bosque y comparar estos efectos en un bosque específico con una serie de fragmentos de bosque que se encontraban en la proximidad a nuestraárea de estudio. La evaluación de la respuesta rápida del bosque seco debido a los efectos de huracanes se exploro en términos de la mortalidad y regeneración, así como se estudió la habilidad de los huracanes de mantener la estructura del bosque. Para este estudio de muestreo, 33 parcelas con daños (1.3 ha) a lo largo de una sección de 3000 ha de bosque así como en 19 fragmentos de bosque. En tallos con ≥2.5 cm de diámetro, 1004 tallos/ha (12.4%) sufrieron daño estructural, mientras que el 69 porciento de los tallos no dañados fueron al menos en un 50 por ciento defoliadas. Perdidas enárea basal debido al daño estructural fue equivalente a 4.0 m 2 /ha (22%). Bosques con pendientes en dirección sur y aquellos en los topes de las colinas presentaron mas daños que bosques con pendientes orientadas hacia el norte o aquellos que estaban constituidos principalmente de especies introducidas. Mortalidad en los tallos fue solamente un 2 porciento después de 9 meses, así como también se...

Aim  Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple‐stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance. Location  Guánica Forest, Puerto Rico. Methods  Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics. Results  Direct effects of the hurricane were minimal, with stem mortality at < 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high – over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (> 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species. Main conclusions  Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi‐stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short‐term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds.

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 Leaf habit has been hypothesized to define a linkage between the slow-fast plant economic spectrum and the drought resistance-avoidance trade-off in tropical forests ('slow-safe versus fast-risky').However, variation in hydraulic traits as a function of leaf habit has rarely been explored for a large number of species.  We sampled leaf and branch functional traits of 97 tropical dry forest tree species from four sites to investigate whether patterns of trait variation varied consistently in relation to leaf habit along the 'slow-safe versus fast-risky' tradeoff.  Leaf habit explained from 0 to 43.69 % of individual trait variation. We found that evergreen and semideciduous species differed in their location along the multivariate trait ordination when compared to deciduous species. While deciduous species showed consistent trait values, evergreen species trait values varied as a function of the site. Last, trait values varied in relation to the proportion of deciduous species in the plant community.  We found that leaf habit describes the strategies that define drought avoidance and plant economics in tropical trees. However, leaf habit alone does not explain patterns of trait variation, which suggests that quantifying site-specific or species-specific uncertainty in trait variation as the way forward.