Browsing by Author "Becerra, Pablo I."

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    Effect of a native tree on seedling establishment of two exotic invasive species in a semiarid ecosystem
    (2011) Becerra, Pablo I.; Bustamante, Ramiro O.
    Theory predicts that in more stressful environments, positive plant-plant interactions should be more important than negative ones. For instance, in arid and semiarid regions, amelioration of soil drought produced by the shade of established plants could facilitate establishment of other species, in spite of light reduction. However, this theory has not been tested widely in the context of plant invasion. In this paper we evaluated the hypothesis that in a semiarid ecosystem of central Chile, the native tree, Lithrea caustica, should facilitate through positive shading effects, the seedling establishment of two widely planted and invasive forestry species, Pinus radiata and Eucalyptus globulus. We assessed the seedling establishment examining two processes: seedling recruitment (including germination) and subsequent seedling survival. We sowed seeds to assess recruitment) and planted 8 months old seedlings (to assess seedling survival) of each exotic species under Lithrea patches, open sites and under an artificial shade mimicking Lithrea shading. The study was repeated in a north-facing and a southfacing slope in the study area located in a xeric zone within the distribution range of plantations of these species in central Chile. Our results show that in a north-facing slope Lithrea had positive effects on recruitment of both species, which was produced by shading. These effects were counteracted by negative effects on seedling survival but through a different mechanism, which suggests that Lithrea would have no significant effect on the whole seedling establishment process of Pinus radiata nor Eucalyptus globulus in this habitat. In turn, in a south-facing slope Lithrea had no significant effect on recruitment but had a negative effect on seedling survival, which was not produced by shading. This suggests that in this habitat Lithrea has a negative effect on the seedling establishment of these exotic species. Our results suggest that the effect of the native Lithrea caustica on the seedling establishment of these exotic species is dependent upon the life-cycle phase (recruitment or seedling survival) and habitat even within the same semiarid ecosystem. In contrast to the expected positive effects Lithrea is unlikely to facilitate seedling establishment of these exotic species in this area, and in fact in some habitats this effect could be negative. However, our results also suggest that a common mechanism proposed to resist invasion in forest ecosystems such as shading, probably is not sufficient to inhibit invasion in a semiarid region.
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    Effect of the invasive exotic herb Centaurea solstitialis on plant communities of a semiarid ecosystem
    (2020) Becerra, Pablo I.; Cavieres, Lohengrin; Bustamante, Ramiro O.
    Background
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    Facilitation by pioneer trees and herbivore exclusion allow regeneration of woody species in the semiarid ecosystem of central Chile
    (2023) Gomez-Fernandez, Nicolas A.; Smith-Ramirez, Cecilia; Delpiano, Cristian A.; Miranda, Alejandro; Vasquez, Inao A.; Becerra, Pablo I.
    Questions: Facilitation by pioneer plants and herbivore exclusion may contribute to plant regeneration and restoration of degraded semiarid ecosystems. In this study we evaluated the main and interactive effects of the exclusion of large and medium-sized mammal herbivores and the presence of the pioneer tree Vachellia caven on natural regeneration of woody species in degraded savannas.
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    Seed predation of woody species in different microhabitats of the Mediterranean-type region of Chile
    (2024) Correa-Solis, Maria Jose; Becerra, Pablo I.
    Seed predation may reduce the quantity and diversity of seeds and limit seedling recruitment. However, the extent to which seed predation may depend on the species and vegetational microhabitat has been less studied. We studied seed predation of woody species in the Mediterranean-type ecosystem of central Chile. We explored if interspecific differences in the magnitude of seed predation depends on the seed mass, evaluated the role vertebrate herbivores in seed predation, and examined if seed predation depends on the vegetation patch type. We conducted a seed removal experiment with eight woody species in three vegetation patch types (forest, shrub, and open) and replicated in two localities. We established exclosures for birds and mammals (wire cages covering 1 m2) and evaluated seed removal during 18 days within and outside of them. We also evaluated the soil seed availability by collecting soil samples inside and outside these exclosures after 2 years of exclusion in the same vegetation patches, adding other three localities. Exclosures significantly reduced the number of seeds removed in all species and patch types of both localities (overall 24.02% of removal in non-exclusion areas vs. 1.77% in exclosures). The magnitude of seed predation was negatively related to the seed mass of species. Exclosures significantly increased the number and species richness of seeds in the soil of forest and shrub patches of four localities. The results suggest that seed predation is mainly produced by vertebrates, affects several woody species from central Chile, and is more common in forest and shrub patches.