Laynara F Lugli1,2, Jessica S Rosa1, Kelly M Andersen2,3,4, Raffaello Di Ponzio5, Renata V Almeida5, Maria Pires1, Amanda L Cordeiro1,6, Hellen F V Cunha1, Nathielly P Martins1, Rafael L Assis1,7, Anna C M Moraes1, Sheila T Souza1, Luiz E O C Aragão2,8, Jose L Camargo5, Lucia Fuchslueger9, Karst J Schaap1, Oscar J Valverde-Barrantes10, Patrick Meir4,11, Carlos A Quesada1, Lina M Mercado2,12, Iain P Hartley2. 1. Coordination of Environmental Dynamics, National Institute of Amazonian Research, Manaus, AM, 69060-062, Brazil. 2. Geography, College of Life and Environmental Sciences, University of Exeter, Amory Building, Rennes Drive, Exeter, Devon, EX4 4RJ, UK. 3. Asian School of the Environment, Nanyang Technological University, Singapore, 639798, Singapore. 4. School of Geosciences, University of Edinburgh, Edinburgh, EH8 9AB, UK. 5. Biological Dynamics of Forest Fragment Project, National Institute for Amazonian Research, Manaus, AM, 69067-375, Brazil. 6. Colorado State University, Fort Collins, CO, 80523, USA. 7. Natural History Museum, University of Oslo, Oslo, 0562, Norway. 8. National Institute for Space Research, São Jose dos Campos, São Paulo, 12227-010, Brazil. 9. Centre of Microbiology and Environmental Systems Science, University of Vienna, Vienna, 1090, Austria. 10. International Centre of Tropical Biodiversity, Department of Biological Sciences, Florida International University, Miami, FL, 33133, USA. 11. Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia. 12. UK Centre for Ecology and Hydrology, Wallingford, OX10 8BB, UK.
Abstract
Soil nutrient availability can strongly affect root traits. In tropical forests, phosphorus (P) is often considered the main limiting nutrient for plants. However, support for the P paradigm is limited, and N and cations might also control tropical forests functioning. We used a large-scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low-fertility soils in Central Amazonia after 1 yr of fertilisation. Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition. Here we showed that rock-derived nutrients determined root functioning in low-fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicated that even slow-growing tropical rainforests can respond rapidly to changes in resource availability.
Soil nutrient availability can strongly affect root traits. In tropical forests, n class="Chemical">phosphorus (P) is often conpan>sidered the mainpan> limitinpan>g nutrient for planpan>ts. However, support for the P paradigm is limited, anpan>d pan> class="Chemical">N and cations might also control tropical forests functioning. We used a large-scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low-fertility soils in Central Amazonia after 1 yr of fertilisation. Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition. Here we showed that rock-derived nutrients determined root functioning in low-fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicated that even slow-growing tropical rainforests can respond rapidly to changes in resource availability.