An Integrative Review of Drivers and Responses of Grassland Phenology under Global Change

This review synthesizes studies of grassland phenology and associations with plant resource-investment tradeoffs, functional traits, environmental and genetic regulators, genome size (GS), and management practices of nitrogen (N) fertilization, grazing, and mowing. Afterwards, the following five knowledge gaps were identified: (i) there is a lack of clarity of constraints of resource acquisition and allocation strategies, which constitute the plant economics spectrum, on herbaceous species vegetative and reproductive phenology; (ii) evidence is lacking for the tuning of phenology by functional traits via coordination of niche dimensionality and nutrient complementarity in species with contrasting community dominance; (iii) the role of keystone regulatory genes, such as AIL1, FDL1, ABI3, FT, and FRIGIDA, on phenology under contrasting environmental conditions (temperature, water, photoperiod) require confirmation; (iv) there is an urgent need to quantify trait-based and resource-partitioning links between GS and phenology to improve understanding of species coexistence; and (v) effects of N fertilization, grazing and mowing on phenological stages of coexisting species and growing season length, through impacts on inter-specific functional traits, light competition, pollination-syndromes, and carbon-investment economics are unclear. Thus, this review has identified areas of research that need to improve model predictions of the direction and magnitude of plant community responses and evolutionary mechanisms under global environmental change.