Distribution Patterns of Tropical Dry Forest Trees Along a Mesoscale Water Availability Gradient

Abstract

Tropical dry forests (TDFs) host a large diversity of tree species but little is known of potential mechanisms that contribute to its maintenance. Given the paramount importance of water availability in such forests, tree species would be expected to show nonrandom patterns along water availability gradients, as well as differential individual species responses. In this work we explored whether that was true for 50 dominant tree species. Within a total area of 5.2 ha, divided into 26 transects each with ten 20 Â 10 m plots, we registered presence-absence of these tree species with diameter at breast height Z5 cm. We assessed the response of trees to four environmental variables differentially related to water availability in three steps: (1) identifying the shape of the response to individual environmental variables, (2) testing for artifacts in previous patterns due to spatial autocorrelation of presence-absence, and (3) identifying the environmental variable or combination of variables that best explained the pattern. We then classified the species with respect to their probability of occurrence along the gradient, and explored which components of the water cycle were likely to be driving the observed patterns. We found that 14 species were generalists, 16 drought tolerant, 9 intermediate, 3 water demanding and 8 showed mixed responses. Lateral flow and access to ground water most likely underlie such patterns. Our results confirm the key role played by water availability in tree species distribution. Water-related niche differentiation seems to be crucial for maintaining the high diversity of this TDF.

Aboveground biomass in mature and secondary seasonally dry tropical forests: A literature review and global synthesis

“…As with mature sites, we cannot assess the relative influence of other biophysical factors on biomass accumulation due to the limitations of our dataset. However, the patterns of biomass accumulation that we document in combination with evidence from studies on physiology of SDTF tree species (Balvanera et al, 2011;Singh and Kushwaha, 2005;Segura et al, 2003), support the hypothesis that MAP limits the maximum attainable biomass and possibly the rate of biomass accumulation as well. Disturbance history, including the extent to which trees were removed, post-disturbance management, the introduction of exotic species, and the proximity of intact forest or regeneration sources all are factors likely to impact the regeneration rate and the amount of biomass attained by secondary forests (Griscom and Ashton, 2011).…”

“…Many tree species in SDTF are distributed according to water availability (Balvanera et al, 2011), and lower rainfall sites have a greater proportion of deciduous trees (Singh and Kushwaha, 2005). By playing a role in bud break and leaf abscission, water availability limits the start and end of the growing period of deciduous trees (Borchert, 1994;Reich and Borchert, 1984).…”

Multidimensional tree niches in a tropical dry forest

“…On the other hand, Balvanera et al. (), in testing the effect of water‐availability gradients on tree distributions in a Mexican SDTF, have suggested that SDTFs may have a greater degree of habitat‐niche specialization compared to wetter forests. While is clear that both soils and topography exert considerable influence on local‐scale plant distributions in SDTFs, by our reading of the literature (Appendix ), the variation in the proportion of habitat specialists in a community within either forest type (tropical rainforest, SDTF) exceeds the variation across forest types.…”

Community assembly and functional diversity along succession post‐management

“…Similarly we propose abiotic variation within plots of old‐growth forest could lead to the observed filtering of trait values. Many species in this study display strong habitat preferences within the Reserve, related to topography and water availability (Balvanera, Quijas & Pérez‐Jiménez ). Species tracking of preferred conditions may explain the reduced range of traits compared to a random community in old‐growth forests.…”

“…). However, assembly of dry forest communities may relate to distinct or additional resources; water in particular is an important determinant of species distributions in undisturbed dry forests (Balvanera, Quijas & Pérez‐Jiménez ).…”