Seasonally dry tropical forests are a globally significant biome for biodiversity and conservation. Globally speaking, Brazil is one of the strongholds of seasonally dry tropical forests, and Brazilian SDTFs may primarily be found in the country’s northeast semiarid region, in a major vegetation domain known as the Caatinga domain.
Although seasonally dry tropical forests are becoming increasingly well studied, there are still glaring gaps in our knowledge, especially when we think about other forests systems such as rainforests.
For example, the ecology of small patches of rainforests are very well studied, and there are also an increasing volume of literature on rainforest long term ecosystem dynamics.
In contrast, there is very little studies on these two ecological aspects in seasonally dry tropical forest. One of our aims was to make a contribution towards this research direction.
So more about Brazil. We have now published a number of articles on the seasonally dry tropical forest in the Caatinga domain. However, nothing is always in black and white, especially in ecology, and seasonally dry tropical forest can be found in disjunct enclaves (i.e. patches) within a matrix of other vegetation types, such as within a savanna (in Brazil known as Cerrado).
We therefore took a close look at a seasonally dry tropical forest enclave within the savanna (Cerrado) domain in central Brazil. These enclaves provide an good opportunity to study change over time in such vegetation.
The details of our work may be found in our recently published article in the Australian Journal of Botany. In a nutshell, in 2007, we set out three sets of 400-square meter plots were used to compare the vegetation at 0 m (edge), 100 m (middle) and 200 m (inner) into our forest enclave. We found as expected that the edge plots had a very different species composition from the interior plots due to the presence of savanna species and also because of soil fertility and soil textural gradients.
When we went back in 2014 to resample the vegetation, we found paradoxically that our inner plots exhibited less stable vegetation patterns than did both the middle and the edge plots. We can generate a new hypothesis that this “non-stability” is possibly a result of natural temporal fluctuations in these vegetation systems for which we still understand little.
On the overall, we can conclude that SDTF enclaves such as the one we studied can exhibit high diversity and structural complexity, especially because such patches have elements of both vegetation types. Perhaps we could view this as the eternal interaction of ecological forces creating new forms. Like the presence of the “yin” circle into the “yang” sector of the Chinese yin-yang symbol, we should never forget about these small patches. Apologetically, we suggest that further studies and long term research on such SDTF enclaves throughout their range should be a high conservation priority.
Reis GH, Terra MCNS, Tng DYP, Apgaua DMG, Coelho PA, Santos RM, Nunes YRF (2017) Temporal vegetation changes in a seasonally dry tropical forest enclave in an ecotonal region between savanna and semiarid
zones of Brazil. Australian Journal of Botany doi: 10.1071/BT16188
Sunderland T, Apgaua D, Baldauf C, Blackie R, Colfer C, Cunningham AB, Dexter K, Djoudi H, Gautier D, Gumbo D, Ickowitz A, Kassa H, Parthasarathy N, Pennington RT, Paumgarten F, Pulla S, Sola P, Tng D, Waeber P, Wilmé L (2015) Global dry forests: a prologue. International Forestry Review, 17(Supplement 2), 1-9.(12). doi: 10.1505/146554815815834813