Phenotypic plasticity facilitates species persistence across resource gradients but may be limited in low resource environments that require resource conservation. We investigated the trade-off between trait plasticity and resource conservatism across a biome boundary characterized by high turnover in nutrient and light availability, and whether this contributes to the maintenance of alternate stable states. Differences in plasticity were determined by comparing species’ leaf and foliar nutritional traits response to light, represented by leaf area index (LAI), and soil nutrient availability across forest–shrubland boundaries in South Africa.
Results/Conclusions
Although forest had higher LAI and soil nutrient availability than shrubland, forest species experienced greater resource variation.With increasing LAI and nutrient availability, forest species increased their leaf size, specific leaf area and leaf area/stem length, and decreased their foliar [N] and [K]. While these responses are indicative of plasticity, shrubland species appeared to lack plasticity as evidenced by limited trait variability even in the presence of environmental heterogeneity. Inhabiting diverse light environments imposed by forest structure likely selects for plasticity, whereas specialization to light-saturated, nutrient-poor environments that select for conservative leaf traits compromises plasticity in shrubland species. This pattern suggests a trade-off between trait plasticity and resource conservatism, which may influence species colonization across ecologically divergent biome boundaries.