Combined effects of seed provenance, plant facilitation and restoration site on revegetation success.
Abstract
Plant provenance, plant facilitation and the characteristics of restoration sites are critical determinants of revegetation success. Surprisingly, however, very little is known about how these key factors interact, both with each other and to complex patterns of recruitment in target plant species. We investigated, for the first time, the potential of combining seed provenance, plant facilitation and restoration site characteristics to guide revegetation efforts. As a model system, we used the Iberian pear (Pyrus bourgaeana) and three potential nurse shrub species. To this end, we completed a comprehensive reciprocal transplant experiment in five P. bourgaeana populations within a fragmented landscape at the Doñana Biosphere Reserve (SW Spain). There were marked differences among provenances for seedling emergence and growth, as well as for recruitment, but no evidence of local adaptation was found. Shrubs generally had a positive or neutral effect on P. bourgaeana seedling performance with, for example survival underneath shrubs being, on average, twice as high as in open microhabitats. Interestingly, however, the magnitude and even the sign of such plant-plant interactions changed with both sowing locality and seed provenance. For instance, shrubs enhanced seedling survival and recruitment at the end of the study in four of the five sowing localities, whereas it decreased it in the remaining locality. Also, although nurse shrubs lessened seedling size of two provenances, it did not have a significant effect on the other three. Synthesis and applications. We show how revegetation success can be maximized, not only by selecting the most appropriate plant material, taking advantage of plant facilitative interactions and selecting the right restoration site, but also by using these factors in an integrated fashion. We propose local managers efficiently undertake future revegetation campaigns by mixing seeds from several genetically adequate source populations in numbers weighted according to previously estimated provenance-specific recruitment successes. Our novel approach can help to guide revegetation of many tree and plant species living in stressful conditions, such as arid, semi-arid and high mountain habitats.