Below-ground opportunities in vegetation science

Background: The below-ground component of vegetation accounts for the bulk of plant mass and vegetation function (e.g. carbon sequestration) in temperate ecosystems, yet the proportion of plant ecology studies that consider roots is <20%. Methods: I review how minirhizotron technology and DNA sequencing of mixed-species root samples allows new insights into below-ground vegetation structure and function. Results: Recent advances highlight important differences between the below- and above-ground parts of vegetation. For example, plant species richness below ground is about 50% greater than that above ground. Below-ground plant richness has been measured from only a few sites, and patterns along gradients of productivity and life-form turnover are unknown. Fine roots differ from leaves in temperate ecosystems by having a growing season 40% longer, and by persisting over multiple growing seasons. Aspects of roots other than growth may vary seasonally, such as nutrient uptake, competition with microbes, or mycorrhizal hyphal production or activity. Minirhizotrons allow the investigation of root heterogeneity at very small scales (<1 mm) that may be more relevant to fine roots and rhizospheres than data obtained fromlarger-scale soil sampling. Conclusions: Work in the near future promises a more complete picture of vegetation function by elucidating mechanisms within the bulk of vegetation, below ground.