Moderate land use changes plant functional composition without loss of functional diversity in India's Western Ghats.

Abstract

The fields of ecology and conservation science increasingly recognize the importance of managing for functional composition and functional diversity to maintain critical ecosystem processes and services. However, little is known about the degree to which widespread but moderate forms of land use that maintain overall vegetation structure are compatible with the conservation of functional diversity. We assessed differences in plani functional composition and functional diversity across savanna woodlands in the Western Ghats, India, managed with varying degrees of biomass extraction, livestock grazing, and ground fire. Across the gradient of moderate land uses, we found shifts in functional composition but no overall decline in functional diversity with land, use intensification. Biomass extraction was associated with changes in dispersal mode, reduced seed mass, and lower overstory functional diversity. Livestock grazing was associated with shorter overstory species, reduced seed mass, and increased understory functional diversity. Nonnative invasive species contributed to shifts in understory functional composition with livestock grazing and increased functional diversity with more intensive land use. Our study highlights both the utility and some limitations of assessing conservation value with functional diversity. These results suggest that moderate-intensity local land use can be compatible with maintenance of functional diversity in savanna woodlands of the Western Ghats, and further efforts to maximize this compatibility would benefit conservation in South India's extensive human-managed landscapes. However, using functional diversity as the sole metric by which to gauge conservation value can mask threats from invasive species and loss of diversity within categories of biotic dispersal. Therefore, functional diversity metrics are likely to provide a valuable complement to, but not replacement for, other management targets such as species composition.