Pollination and sexual reproduction of key dominant trees of Arid Chaco under different land-use intensities

Abstract

Fruit production by dominant native trees in the arid Chaco of central Argentina represents a crucial provisioning ecosystem service for local peasant economies. This region presents gradients of different woody vegetation cover (open forests and shrublands) along with cattle production systems operating under a variety of management regimens and socio-environmental degradation conditions. Here, we assess land-use intensity effects on pollination and reproduction of Neltuma spp. and Sarcomphalus mistol. The studied species responded differently to land-use intensity. Pollination service and fruit production in the strict self-incompatible Neltuma spp. tended to decrease with increased land-use intensity. In contrast, both pollination and reproduction in S. mistol, which is able to set fruits with geitonogamous pollen, increased in the highest land-use intensity sites (silvopastoral system). In Neltuma spp., the highest values of fodder production (fruit set, fruit mass and total fruit per plant) were found in secondary forests (medium land-use intensity). The positive effects of land-use intensity on the reproduction of S. mistol could be related to the higher visitation frequency observed in these sites, especially from Apis mellifera, but also with the higher amounts of soil nitrates and light availability in these sites. The only two stingless bee species present in the region (Plebeia molesta and P. catamarcensis) played an important role in the reproduction of Neltuma species, increasing fodder production. Our results highlight the complexity of species response to land-use changes and underline the importance of thinking beyond the conservation of species to concentrate on preserving ecological interactions. Many key functional aspects of ecosystems functioning and ecosystem services provision closely depend on plant-animal interactions. Thus, the promotion of local production systems that allows the preservation of not only provision services but also plant-pollinator interactions is crucial to conserve these remaining arid Chaco forests and secure the livelihoods of local communities.