Abstract
The mycorrhizal component of revegetated areas after ecological restoration or rehabilitation in arid and semiarid tropical areas has been scarcely assessed, particularly those made after mining disturbance. We evaluated and compared the presence of arbuscular mycorrhizal fungi of a small area of restored tropical dry forest destroyed by sand extraction, with a non-restored area of similar age, at the peninsula of Macanao, Margarita Island (Venezuela). Our study was undertaken in 2009, four years after planting, and the mycorrhizal status was evaluated in four restored plots (8 x 12.5 m) (two were previously treated with hydrogel (R2 and R2'), and two were left untreated (R1 and R1'), and four non-restored plots of similar size (NR1 and NR1' with graminoid physiognomy with some scattered shrubs; and NR2 and NR2', with a more species rich plant community). Apparently the restoration management promoted higher arbuscular mycorrhizal fungi (AMF) species richness and diversity, particularly in restored soils where the hydrogel was added (R2 treatment). Soil of the NRI treatment (with a higher herbaceous component) showed the highest spore density, compared to samples of soils under the other treatments. Considering species composition, Claroideoglomus etunicatum and Rhizophagus intraradices were found in all treatments; besides, Diversispora spurca and Funnefformis geosporum were only found in non-restored plots, while members of the Gigasporaceae (a family associated with little disturbed sites) were commonly observed in the plots with restored soils. Mycorrhizal colonization was similar in the restored and non-restored areas, being a less sensitive indicator of the ecosystem recovery. The trend of higher richness and diversity of AMF in the restored plot with hydrogel suggests that this management strategy contributes to accelerate the natural regeneration in those ecosystems where water plays an essential role.
Highlights
Tropical dry forest (TDF) is considered one of the most endangered tropical ecosystems (Janzen, 1988; Murphy & Lugo, 1995)
Of the 32 Arbuscular mycorrhizal fungi (AMF) species found in the field samples, Claroideoglomus etunicatum and Rhizophagus intraradices were present in all treatments (Table 2)
The differences were not significant, AMF species richness and diversity was higher in restored soils, especially those treated with hydrogel (R2)
Summary
Tropical dry forest (TDF) is considered one of the most endangered tropical ecosystems (Janzen, 1988; Murphy & Lugo, 1995). Sand mining extraction in the lowlands of the Macanao peninsula, Margarita island in Venezuela has led to the total destruction of plant communities associated with ephemeral water courses, which represent the most developed, complex and species rich communities in this region (González, 2007) This activity has destroyed many of the dry shrublands and forests, but has had other undesirable consequences, such as for example, the topographic disturbance of the ephemeral creeks, the removal of topsoil and plant species important for the diet and refuge of fauna (including some endangered species, e.g. Amazona barbadensis), an increase in erosion and the invasion of exotic plant species, amongst others (Fajardo, Rodríguez, González, & Briceño-Linares, 2013). Mycorrhizal status was related with variables like spore number, mycorrhizal colonization and composition, richness and diversity of the AMF assemblages
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