Effect of plant diversity on ecosystem functions
in grasslands - the role of roots
People
Christof Engels, Project P.I.
Holger Beßler, Ph.D.-student
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Rationale
In several recent studies it was found that increasing plant diversity in experimental grassland communities is associated with enhanced productivity and lower risk of nutrient leaching from soil. Relatively little is known about the effect of plant diversity on rooting pattern.
Root biomass production substantially contributes to total plant biomass production. In agriculturally used grassland, rhizodeposition and root turnover is the most important component of total carbon input into the soil. The acquisition of soil resources by plants, which often limits plant productivity and controls nutrient leaching, is dependent on rooting pattern in time and space. Positive effects of high plant diversity on productivity may be due to complementarity of species in rooting pattern.
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Subproject aims
This project aims to provide data on:
- root biomass production and turnover which are necessary to assess the effect of plant diversity on total plant productivity and carbon and nutrient input into the soil,
- rooting pattern in time and space which are necessary to improve our understanding about the mechanisms regulating biodiversity effects on productivity and nutrient retention in soil.
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Methods
Root biomass production is assessed with the "ingrowth core" technique: soil cores are removed and root-free soil from field site is replaced into the holes at time zero. After a certain period of time the soil cores are removed again, and the roots inside the core are separated from soil for determination of biomass and mineral nutrients.
"Ingrowth core" technique
Rooting pattern in space and time is determined with the "minirhizotron" technique: transparent plastic tubes (minirhizotrons) are inserted into the soil; roots growing along the interface between tube and soil can be observed in different soil depths using an endoscope-camera system.
"Minirhizotron" technique
In a first approach root turnover is assessed with the "minirhizotron" technique: repeated observations of the same section of the soil/tube interface allow recording of individual roots from their appearance at the interface (birth) to their disappearance (death). In a second approach root turnover is calculated from root production and maximum standing root biomass.
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First results
Measurements with the "ingrowth core" technique show a substantial effect of specific plant functional groups on the annual root biomass production in the experimental grassland stands.
Annual root biomass production of different plant functional groups grown in monocultures.
Repeated observations with the "minirhizotron" technique reveal persistence of individual roots in the soil for at least several months, thus indicting low root turnover in the experimental grassland stands.
Nodule formation and root persistence in a monoculture of Trifolium pratense.
Assessment of rooting pattern with the "minirhizotron" technique indicates large differences among plant species in vertical root distribution and the temporal pattern of rooting e.g. during winter and early spring.
Differences in vertical distribution of root length growth among 3
grassland plant species
grown in monocultures.
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GERMAN