(1) There are neighboring tropical dry forests or remnants with abundant seeds to
be dispersed into the abandoned stands.
(2) There are important bird populations.
(3) There are perching sites for birds.
(4) Soils are hydromorphic and water is not too limiting.
Certainly, in Mexico there is a great need to restore tropical dry forests growing
on dunes, because most of them have disappeared in the region, and because these
woody species are useful and people have cut down the trees without planting
more to replace them (Moreno-Casasola and Paradowska 2009). Also, the introduction of cattle has resulted in vegetation loss. Frequently, and because the
species grows fast and tolerates the extreme coastal dune environment, Casuarina
trees have been used in reforestation programs in the tropics, ignoring the fact that
it is an exotic and invasive species. However, in the humid swales and low-lying
areas where litter can be decomposed at a relatively fast rate, restoration actions
could be implemented to enhance the growth and establishment of tropical dry
forest vegetation already growing in the understory. The gradual removal of the
exotic tree would lead to an advanced state of natural regeneration.
It is noteworthy to highlight that the establishment of the tropical dry forest may
take a long time. Locally, it is known that C. equisetifolia trees live 40–45 years.
We observed that some of the trees in the old plots were already dying, which
means that the natural regeneration and colonization process in the old stands has
been occurring for about 40–45 years and still there were significant differences
with the tropical dry forest stands. This implies that restoration by natural
regeneration is a long process that lasts more than 4 decades.
Finally, although in high moisture conditions there is a potential for restoration
beneath Casuarina stands, it is important to bear in mind that native species should
preferably be promoted as the species for plantations since the risk of an
aggressive exotic is always latent and potentially very damaging to biodiversity
and the natural functioning of ecosystems.
Acknowledgments We are very grateful to P.A. Hesp and J.B. Gallego-Fernández for their
thorough revision and very useful comments and recommendations made in earlier versions of
this chapter. R. Monroy elaborated Fig. 14.1. Thanks are also due to D. Infante for her help with
the field work.
References
Abdel Wahab AM (1980) Nitrogen-fixing nonlegumes in Egypt. I. Nodulation and N 2 (C2H2)
fixation by Casuarina equisetifolia. Zeitschrift fur Allgemeine Mikrobiologie 20:3–12
Arnold GW (1988) The effects of habitat structure and floristics on the densities of bird species in
wandoo woodland. Aust Wildl Res 15(5):499–510
Arnold GW, Malle RA, Litchfield R (1987) Comparison of bird populations in remnants of
wandoo woodland and in adjacent farmland. Aust Wildl Res 14(3):331–341
14 The Impacts on Natural Vegetation
231
be dispersed into the abandoned stands.
(2) There are important bird populations.
(3) There are perching sites for birds.
(4) Soils are hydromorphic and water is not too limiting.
Certainly, in Mexico there is a great need to restore tropical dry forests growing
on dunes, because most of them have disappeared in the region, and because these
woody species are useful and people have cut down the trees without planting
more to replace them (Moreno-Casasola and Paradowska 2009). Also, the introduction of cattle has resulted in vegetation loss. Frequently, and because the
species grows fast and tolerates the extreme coastal dune environment, Casuarina
trees have been used in reforestation programs in the tropics, ignoring the fact that
it is an exotic and invasive species. However, in the humid swales and low-lying
areas where litter can be decomposed at a relatively fast rate, restoration actions
could be implemented to enhance the growth and establishment of tropical dry
forest vegetation already growing in the understory. The gradual removal of the
exotic tree would lead to an advanced state of natural regeneration.
It is noteworthy to highlight that the establishment of the tropical dry forest may
take a long time. Locally, it is known that C. equisetifolia trees live 40–45 years.
We observed that some of the trees in the old plots were already dying, which
means that the natural regeneration and colonization process in the old stands has
been occurring for about 40–45 years and still there were significant differences
with the tropical dry forest stands. This implies that restoration by natural
regeneration is a long process that lasts more than 4 decades.
Finally, although in high moisture conditions there is a potential for restoration
beneath Casuarina stands, it is important to bear in mind that native species should
preferably be promoted as the species for plantations since the risk of an
aggressive exotic is always latent and potentially very damaging to biodiversity
and the natural functioning of ecosystems.
Acknowledgments We are very grateful to P.A. Hesp and J.B. Gallego-Fernández for their
thorough revision and very useful comments and recommendations made in earlier versions of
this chapter. R. Monroy elaborated Fig. 14.1. Thanks are also due to D. Infante for her help with
the field work.
References
Abdel Wahab AM (1980) Nitrogen-fixing nonlegumes in Egypt. I. Nodulation and N 2 (C2H2)
fixation by Casuarina equisetifolia. Zeitschrift fur Allgemeine Mikrobiologie 20:3–12
Arnold GW (1988) The effects of habitat structure and floristics on the densities of bird species in
wandoo woodland. Aust Wildl Res 15(5):499–510
Arnold GW, Malle RA, Litchfield R (1987) Comparison of bird populations in remnants of
wandoo woodland and in adjacent farmland. Aust Wildl Res 14(3):331–341
14 The Impacts on Natural Vegetation
231