When does plant diversity matter?

By Cynthia Chang

Plant communities provide important ecosystem services to us, such as food and natural resources. The more productive an ecosystem is, the more food or resources are available for us to use.  Having more plant diversity in a community is thought to increase overall productivity. The idea behind this is that different types of plants occupy different niches– or resource requirements. For example, some types of plants may have shallow roots while other types may have deeper roots. If you have a diverse plant community with many different depths of roots, the community as a whole is able to access more water along the entire depth of the water column. People have been applying this theory for a long time in agricultural practices, growing different types of crops together in hopes of maximizing productivity.

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Ecologists have been testing whether having more plant diversity increases ecosystem productivity in a variety of experiments with varying results. Recently, there has been a growing interest in understanding whether or not increasing genetic diversity within a single plant species increases productivity. The idea is that a genetically diverse group of plants will occupy different niches whereas a group of clones, genetically identical individuals, will occupy the same niche and thus, be less productive overall.

Our UW-Bothell Plant Ecology class is conducting a greenhouse experiment growing 3500 (!!) Arabidopsis thaliana plants to determine whether plant diversity impacts community productivity. We will grow 6 plants together in a single pot to represent a small plant community. Some pots will have high genetic diversity, while other pots will have lower genetic diversity. In addition, certain plant individuals will also be more genetically predisposed to exhibiting different traits under different growing conditions (also known as phenotypic plasticity). Some pots will have individuals that exhibit very different traits under different growing conditions (high phenotypic plasticity), while other pots will have individuals that always exhibit the same trait (low phenotypic plasticity). We will grow these plant communities under two different water conditions, high and low water, to see how different plants respond. At the end of the experiment, we will compare total biomass of each pot between all the different communities to determine whether more diversity increases productivity.

This project is part of the unPAK (undergraduates phenotyping Arabidopsis knockouts) and the data we collect will contribute to a nationwide, collaborative network. The goal of this network is to get undergraduate students involved in developing a database to help understand the genotype-phenotype relationship of different Arabidopsis mutants.

Check back in next week to hear more about our seed sowing adventures!

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