title: The value of biodiversity for the functioning of tropical forests: insurance effects during the first decade of the Sabah biodiversity experiment.
abstract: One of the main environmental threats in the tropics is selective logging, which has degraded large areas of forest. In southeast Asia, enrichment planting with seedlings of the dominant group of dipterocarp tree species aims to accelerate restoration of forest structure and functioning. The role of tree diversity in forest restoration is still unclear, but the 'insurance hypothesis' predicts that in temporally and spatially varying environments planting mixtures may stabilize functioning owing to differences in species traits and ecologies. To test for potential insurance effects, we analyse the patterns of seedling mortality and growth in monoculture and mixture plots over the first decade of the Sabah biodiversity experiment. Our results reveal the species differences required for potential insurance effects including a trade-off in which species with denser wood have lower growth rates but higher survival. This trade-off was consistent over time during the first decade, but growth and mortality varied spatially across our 500 ha experiment with species responding to changing conditions in different ways. Overall, average survival rates were extreme in monocultures than mixtures consistent with a potential insurance effect in which monocultures of poorly surviving species risk recruitment failure, whereas monocultures of species with high survival have rates of self-thinning that are potentially wasteful when seedling stocks are limited. Longer-term monitoring as species interactions strengthen will be needed to more comprehensively test to what degree mixtures of species spread risk and use limited seedling stocks more efficiently to increase diversity and restore ecosystem structure and functioning.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
authors.forename: Sean L
authors.identifier: 0000-0002-1542-3589
authors.initials: SL
authors.lastname: Tuck
authors.affiliation: Consejo Superior de Investigaciones Científicas, Estación Experimental de Zonas Áridas, Carretera de Sacramento s/n, 04120 La Cañada, Almería, Spain.|Danum Valley Field Centre, The SE Asia Rainforest Research Partnership (SEARRP), PO Box 60282, 91112 Lahad Datu, Sabah, Malaysia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Brien
authors.affiliation: Ecosystem Management, Institute of Terrestrial Ecosystems, ETH Zurich, Switzerland.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Philipson
authors.affiliation: Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Saner
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
authors.forename: Matteo
authors.initials: M
authors.lastname: Tanadini
authors.affiliation: Tropical Rainforest Conservation and Research Centre, Lot 2900 and 2901, Jalan 7/71B Pinggiran Taman Tun, 60000 Kuala Lumpur, Malaysia.
authors.forename: Dzaeman
authors.initials: D
authors.lastname: Dzulkifli
authors.affiliation: Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
authors.forename: H Charles J
authors.identifier: 0000-0001-8859-7232
authors.initials: HC
authors.lastname: Godfray
authors.affiliation: Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah, 88400 Sabah, Kota Kinabalu, Malaysia.
authors.forename: Elia
authors.initials: E
authors.lastname: Godoong
authors.affiliation: Sabah Forestry Department Forest Research Centre, Mile 14 Jalan Sepilok, 90000 Sandakan, Sabah, Malaysia.
authors.forename: Reuben
authors.initials: R
authors.lastname: Nilus
authors.affiliation: Sabah Forestry Department Forest Research Centre, Mile 14 Jalan Sepilok, 90000 Sandakan, Sabah, Malaysia.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Ong
authors.affiliation: Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmid
authors.affiliation: Yayasan Sabah (Conservation and Environmental Management Division), 12th Floor, Menara Tun Mustapha, Yayasan Sabah, Likas Bay, PO Box 11622, 88813 Kota Kinabalu, Sabah.
authors.forename: Waidi
authors.initials: W
authors.lastname: Sinun
authors.affiliation: Centre for Biological Sciences, University of Southampton, Southampton, UK.
authors.forename: Jake L
authors.initials: JL
authors.lastname: Snaddon
authors.affiliation: Face the Future, Utrechtseweg 95, 3702 AA, Zeist, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Snoep
authors.affiliation: Yayasan Sabah (Conservation and Environmental Management Division), 12th Floor, Menara Tun Mustapha, Yayasan Sabah, Likas Bay, PO Box 11622, 88813 Kota Kinabalu, Sabah.
authors.forename: Hamzah
authors.initials: H
authors.lastname: Tangki
authors.affiliation: School of International Tropical Forestry, Universiti Malaysia Sabah, Kota Kinabalu, 88400 Sabah, Malaysia.
authors.forename: John
authors.initials: J
authors.lastname: Tay
authors.affiliation: Danum Valley Field Centre, The SE Asia Rainforest Research Partnership (SEARRP), PO Box 60282, 91112 Lahad Datu, Sabah, Malaysia.
authors.forename: Philip
authors.initials: P
authors.lastname: Ulok
authors.affiliation: Yayasan Sabah (Conservation and Environmental Management Division), 12th Floor, Menara Tun Mustapha, Yayasan Sabah, Likas Bay, PO Box 11622, 88813 Kota Kinabalu, Sabah.
authors.forename: Yap Sau
authors.initials: YS
authors.lastname: Wai
authors.affiliation: Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland.
authors.forename: Maja
authors.initials: M
authors.lastname: Weilenmann
authors.affiliation: Danum Valley Field Centre, The SE Asia Rainforest Research Partnership (SEARRP), PO Box 60282, 91112 Lahad Datu, Sabah, Malaysia.
authors.forename: Glen
authors.initials: G
authors.lastname: Reynolds
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK andrew.hector@plants.ox.ac.uk.
authors.forename: Andy
authors.identifier: 0000-0002-1309-7716
authors.initials: A
authors.lastname: Hector
mesh_terms: D044822:Biodiversity; D065928:Forests; D008296:Malaysia; D036226:Seedlings / Q000254:growth & development; D014197:Trees / Q000254:growth & development*; D014329:Tropical Climate
keywords: Dipterocarpaceae; Sabah biodiversity experiment; biodiversity and ecosystem functioning; forest restoration; selective logging; tropical forest