In arid environments, direct facilitation (microhabitat amelioration) and indirect facilitation ('associational resistance' via protection from herbivory) among plants of different species may act simultaneously. Little is known about their relative effects. One way to disentangle the effects is by evaluating spatial associations. We examined the relative importance of these two mechanisms of facilitation in the semiarid Chaco vegetation of north-central Argentina, through an eight-way observational study in which we quantified the degree of spatial association between saplings of each of two key tree species, Schinopsis lorentzii (Anacardiaceae) and Aspidosperma quebracho-blanco (Apocynaceae), with shrub neighbours either possessing spines or without spines and in both an ungrazed site and a site with a long history of cattle grazing.We analysed data across 400 subparcels at each site with spatial analysis by distance indices. Saplings of both tree species showed positive spatial associations with spiny shrubs in the grazed site but not in the ungrazed site, and never with non-spiny shrubs. This result suggests that spiny shrubs may indeed provide associational resistance for saplings of key tree species in grazed habitats in these dry subtropical forests, that is, that indirect facilitation may predominate over direct facilitation. If confirmed by experimental studies, this result can have implications for the silvopastoral management of rapidly expanding ranches in the semiarid Chaco, where current practice includes the near elimination of native shrubs.
Throughout its range in Latin America, the jaguar Panthera onca is threatened by habitat loss and fragmentation, and by conflict as a result of coexistence with people. This Near Threatened species is a top predator, and is often illegally hunted. Understanding people's attitudes and perceptions and the factors that could influence them is crucial for the conservation of this species. In this study we assess how knowledge, attitudes and perceptions among people in northern Argentina regarding jaguars vary depending on their level of education, age and occupation. We interviewed 810 people living in and around 10 protected areas in northern Argentina. Positive perceptions and attitudes towards the jaguar were associated with economic benefits that people may receive from the species’ presence, such as income from tourism. Unexpectedly, higher levels of formal education were not associated with more positive attitudes and perceptions. Negative attitudes and perceptions towards the species were determined by fear; people see jaguars as a threat to their lives. This study shows that the socio-economic factors that affect the level of tolerance towards jaguars are not related only to economic losses. Our findings provide information for the design, implementation and evaluation of jaguar conservation projects in Argentina.
In semiarid regions, livestock is concentrated around water sources generating a piosphere pattern (gradients of woody vegetation degradation with increasing proximity to water). Close to the water source, livestock may affect the composition, structure and regeneration strategies of woody vegetation. We used the proximity from a water source as a proxy of grazing pressure. Our objectives were (1) to compare woody vegetation attributes (richness, diversity, species composition, density and basal area) and ground cover between sites at two distances to a water source: near (higher grazing pressure) and far from the water source (lower grazing pressure), and (2) to quantify and compare cases of spatial association among the columnar cacti Stetsonia coryne (Salm-Dyck) Britton and Rose (Cactaceae), and the dominant tree Bulnesia sarmientoi Lorentz ex Griseb. (Zygophyllaceae). We used a paired design with eight pairs of rectangular plots distributed along a large and representative natural water source. We found lower total species richness, plant density and soil cover near than far from water source, and more cases of spatial associations between the two species studied. Our results show evidence of increased livestock impacts around water sources. However, we found no difference in terms of species composition or basal area at near versus far sites. We conclude that grazing pressure might be changing some attributes of the woody plant community, and that the association of young trees with thorny plants (grazing refuge) could be a regeneration mechanism in this semiarid forest with high grazing pressure.
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