Latest Research News on Coastal Forest : Mar 2022

Distribution patterns and conservation of eastern Brazilian coastal forest tree species

The distributions of 127 tree species, each with at least part of their range in the moist coastal forest of eastern Brazil, are analyzed. Of these, 53.5% are endemic to the coastal forest, 11.8% endemic to the coastal forest plus some part of the Planalto of Brazil, 7.8% disjunct with the Amazonian hylaea, and 26% widespread. This high endemism in the coastal forest of eastern Brazil, in view of its rapid destruction, emphasizes the need for increased preservation of the few remaining natural areas. In addition, this study supports the theory that there are at least two centers of endemism in the coastal forests, one centering around Rio de Janeiro and one in southern Bahia/Rio Doce, Espírito Santo. In order to protect the diverse flora of the coastal forests, preservation areas should be established intermittently along their entire length and especially in the centers of endemism.[1]


Effects of Coastal Forest on Tsunami Hazard Mitigation — A Preliminary Investigation

In order to utilize coastal forest as tsunami countermeasures, quantitative evaluation for hydrodynamic effect of coastal forest and the clarification of prevention functions against tsunamis were examined in this paper. Field survey and review and summary on the control forest conditions were carried out to evaluate the effect of coastal forest and to find the condition of coastal forest. A relation between the forest density and the diameter of trunk is obtained through the field survey of control forest and some previous researches, which is useful information for the evaluation of the tsunami reduction effects. Numerical simulation including the control forest effect is performed for evaluating the quantitative effect for tsunami reduction and damage. It is found that an increase of forest width can reduce not only inundation depth but also current and hydraulic force behind the coastal forest. By using these results, effects of reducing tsunamis can be quantitatively evaluated in a relation to the tsunami and forest conditions. Finally, review and summary is done to recognize the mitigation effect of tsunami disaster by the coastal forest in the past. Four main functions to reduce tsunami disaster are found; 1) to stop drifts or ships carried by a tsunami, 2) to reduce tsunami energy, 3) to form sand dune protecting tsunamis as well as high waves, and 4) to catch persons carried back by a tsunami to the sea. However, it should be reminded that the coastal forests would be destroyed by a huge tsunami and floating material would cause secondary damage.[2]


Coastal forest effects on tsunami run-up heights

An experimental study was carried out to determine the effects of a coastal forest on tsunami run-up heights. The beach was built as a natural sandy beach at laboratory scale. The coastal forest model was constructed using artificial trees (FM–I) and cylindrical timber sticks (FM–II). Artificial trees were placed on a 1:5 slope in three different layouts: rectilinear, staggered, and dense rectilinear. It was shown that in the case when the trees were placed in the dense rectilinear pattern and close to the still water level (SWL), the run-up height was reduced by approximately 45% compared with the case without trees. After evaluation of the experimental results, the parameters that affect the run-up height were determined. These parameters were written as a dimensionless group using Buckingham’s Pi theorem. An extensive regression analysis was carried out and equations proposed. Furthermore, all experiments were repeated with a slope of 1:3.5 to verify the proposed equations. The experimental results were compared with the results of the proposed equations, and it was shown a good agreement between the results.[3]


Hurricane Hugo Wind Damage to Southeastern U.S. Coastal Forest Tree Species

One percent of Hobcaw Forest, a 3077 ha tract in South Carolina’s lower coastal plain, was inventoried with fixed area plots within four months after the eye of Hurricane Hugo passed 97 km south of the forest. Results of this sampling confirmed our hypotheses that the amount and nature of hurricane wind damage differed among the tree species sampled. Approximately 73 percent of the 16,870 trees inventoried were either not damaged or had light crown damage. Longleaf pine (Pinus palustris) was less damaged than loblolly pine (Pinus taeda) or pond pine (Pinus serotina). Bald cypress (Taxodium distichum) suffered light crown damage. Upland oaks were more heavily damaged than the pine species. Live oak (Quercus virginiana) was less damaged than laurel oak (Quercus laurifolia) and water oak (Quercus nigra). Those tree species commonly found in the lower coastal plain (longleaf pine, bald cypress, and live oak) suffered less damage than species with larger natural ranges.[4]


Geographical variation in genetic structure of an Atlantic Coastal Forest frog reveals regional differences in habitat stability

Climatic oscillations throughout the Pleistocene combined with geological and topographic complexity resulted in extreme habitat heterogeneity along the Atlantic coast of Brazil. Inferring how these historic landscape patterns have structured the current diversity of the region’s biota is important both for our understanding of the factors promoting diversification, as well as the conservation of this biodiversity hotspot. Here we evaluate potential historical scenarios of diversification in the Atlantic Coastal Forest of Brazil by investigating the population genetic structure of a frog endemic to the region. Using mitochondrial and nuclear sequences, we generated a Bayesian population-level phylogeny of the Thoropa miliaris species complex. We found deep genetic divergences among five geographically distinct clades. Southern clades were monophyletic and nested within paraphyletic northern clades. Analyses of historical demographic patterns suggest an overall north to south population expansion, likely associated with regional differences in habitat stability during the Pliocene and early Pleistocene. However, genetic structure among southern populations is less pronounced and likely represents more recent vicariant events resulting from Holocenic sea-level oscillations. Our analyses corroborate that the Atlantic Coastal Forest has been a biogeographically dynamic landscape and suggest that the high diversity of its fauna and flora resulted from a combination of climatic and geologic events from the Pliocene to the present.[5]


Reference

[1] Mori, S.A., Boom, B.M. and Prance, G.T., 1981. Distribution patterns and conservation of eastern Brazilian coastal forest tree species. Brittonia, 33(2), pp.233-245.

[2] Harada, K. and Imamura, F.U.M.I.H.I.K.O., 2005. Effects of coastal forest on tsunami hazard mitigation—a preliminary investigation. In Tsunamis (pp. 279-292). Springer, Dordrecht.

[3] Irtem, E., Gedik, N., Kabdasli, M.S. and Yasa, N.E., 2009. Coastal forest effects on tsunami run-up heights. Ocean Engineering, 36(3-4), pp.313-320.

[4] Gresham, C.A., Williams, T.M. and Lipscomb, D.J., 1991. Hurricane Hugo wind damage to southeastern US coastal forest tree species. Biotropica, pp.420-426.

[5] Fitzpatrick, S.W., Brasileiro, C.A., Haddad, C.F. and Zamudio, K.R., 2009. Geographical variation in genetic structure of an Atlantic Coastal Forest frog reveals regional differences in habitat stability. Molecular Ecology, 18(13), pp.2877-2896.

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