Root dynamics and survival in a nutrient-poor and species-rich woodland under a drying climate
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Background and aims
In Australia’s Mediterranean hyperdiverse vegetation, species that produce cluster roots to mobilise poorly-available nutrients (e.g. Banksia spp.) are an important functional and structural component. Cluster roots are only active during the wet season, indicating a strong dependence on suitable surface soil moisture conditions. Winter rainfall in this region is declining due to global climate change, with a delayed commencement of rains and a decline in precipitation. It is unknown how lower soil moisture levels will affect the root dynamics of these globally-significant plant communities.
We determined the root dynamics and root lifespan with minirhizotrons with or without irrigation to simulate reduced rainfall scenarios.
We found a major effect of irrigation on the early production (0.24 m m−2 d−1 increase), occurrence (97% increase) of cluster roots and only slight effects on lifespan (~10 days less) of all root types. With irrigation, the resultant greater soil moisture levels increased the deployment of cluster roots. Apart from cluster roots, the dynamics of other roots did not decline at lower soil moisture levels, suggesting that this system shows some resilience to decreased rainfall.
Future research should focus on assessing if climate-altered cluster-root activity may be promoting compositional shifts in plant communities with additional restraining effects on root trait diversity.
KeywordsBanksia attenuata Cluster-root emergence Mediterranean climate change Minirhizotron Root lifespan and longevity Soil moisture
Michael Blair and Raymond Scott provided help at the start of the experimental setup and tube installations and for facilitating access to the field station. We are indebted to Bryden Quirk and David D. Sampson (Optical + Biomedical Engineering Laboratory) at the School of Electrical, Electronic & Computer Engineering at UWA for building a high-resolution minirhizotron camera and helping gather the first set of images. We are grateful to Jairo Palta, then at CSIRO in Floreat, for loaning the Bartz minirhizotron camera. Thomas Mazet played a key role with imaging during rainy days. We are especially grateful to Judith Holmes, Cynthia Playford, and Ruby Johnson of the ‘Friends of Kings Park’ for their valuable help during the plant identification and root annotation with RootFly. Funding was provided by The University of Western Australia with a Research and Development Award granted to FT and the Australian Research Council with a Discovery Project (ARC DP0985685) to HL, EV and KD.
FPT, HL, KWD, and EJV originally formulated the idea, FPT, KWD, and EJV developed methodology, FPT conducted fieldwork, FPT generated the images, VAM and FPT analysed the images, FPT performed statistical analyses, and FPT, VAM, HL, KWD, and EJV wrote the manuscript.
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