Influences of traits and processes on productivity and functional composition in grasslands: A modeling study

Grasslands are an important habitat for many plant species whose functional diversity and composition influences ecosystem functioning and services. Despite several field studies, still uncertainties remain about the interplay of species traits and ecosystem processes that lead to the functional diversity observed in grasslands. Here, we used an individual-based process-oriented model to simulate a biodiversity field experiment located in Central Europe. With the focus on plant functional types (PFT), the simulation model well reproduced vegetation attributes of grassland communities at different diversity levels (of up to four PFTs of grasses, small herbs, tall herbs and legumes). To understand how plant traits and competition between plants affects the functional composition of grasslands, we tested in a simulation study the impact of different ecosystem processes and detected sensitive plant traits. According to our model results, competition for space affects community productivity stronger than competition for light. While some traits increase and strengthen the growth of plants, other functional traits make plants stronger through advantages in demographic processes. Our model-based findings can be substantiated by several independent field studies in terms of relative yield, plant density, plant biomass and life span of plant functional types. The methods and analyses shown here represent a promising step for the development of grassland models to investigate the complex structures and dynamics of temperate grasslands in complement to field studies.