title: The influence of variable rainfall frequency on germination and early growth of shade-tolerant dipterocarp seedlings in borneo.
abstract: Climate change induced alterations to rainfall patterns have the potential to affect the regeneration dynamics of plant species, especially in historically everwet tropical rainforest. Differential species response to infrequent rainfall may influence seed germination and seedling establishment in turn affecting species distributions. We tested the role of watering frequency intervals (from daily to six-day watering) on the germination and the early growth of Dipterocarpaceae seedlings in Borneo. We used seeds that ranged in size from 500 to 20,000 mg in order to test the role of seed mass in mediating the effects of infrequent watering. With frequent rainfall, germination and seedling development traits bore no relationship to seed mass, but all metrics of seedling growth increased with increasing seed mass. Cumulative germination declined by 39.4% on average for all species when plants were watered at six-day intervals, and days to germination increased by 76.5% on average for all species from daily to six-day intervals. Final height and biomass declined on average in the six-day interval by 16% and 30%, respectively, but the percentage decrease in final size was greater for large-seeded species. Rooting depth per leaf area also significantly declined with seed mass indicating large-seeded species allocate relatively more biomass for leaf production. This difference in allocation provided an establishment advantage to large-seeded species when water was non-limiting but inhibited their growth under infrequent rainfall. The observed reduction in the growth of large-seeded species under infrequent rainfall would likely restrict their establishment in drier microsites associated with coarse sandy soils and ridge tops. In total, these species differences in germination and initial seedling growth indicates a possible niche axis that may help explain both current species distributions and future responses to climate change.
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland. mikey.j.obrien@gmail.com
authors.forename: Michael J
authors.initials: MJ
authors.lastname: O'Brien
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Philipson
authors.forename: John
authors.initials: J
authors.lastname: Tay
authors.forename: Andy
authors.initials: A
authors.lastname: Hector
mesh_terms: D018533:Biomass; D001893:Borneo; D053958:Dipterocarpaceae / Q000254:growth & development* / Q000502:physiology; D018525:Germination / Q000502:physiology*; D036226:Seedlings / Q000254:growth & development* / Q000502:physiology; D012639:Seeds / Q000502:physiology
references.citation: Science. 2011 Feb 4;331(6017):554
references.pmid: 21292971
references.citation: New Phytol. 2012 Jan;193(1):30-50
references.pmid: 22085245
references.citation: Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):4242-7
references.pmid: 20160078
references.citation: Oecologia. 2007 Dec;154(3):445-54
references.pmid: 17846798
references.citation: Ecol Lett. 2012 Aug;15(8):899-911
references.pmid: 22553898
references.citation: Oecologia. 2006 Jun;148(2):258-69
references.pmid: 16514537
references.citation: Philos Trans R Soc Lond B Biol Sci. 2011 Nov 27;366(1582):3303-15
references.pmid: 22006970
references.citation: Ann Bot. 2008 Dec;102(6):945-51
references.pmid: 18840874
references.citation: Philos Trans R Soc Lond B Biol Sci. 1999 Nov 29;354(1391):1869-83
references.pmid: 11605629
references.citation: Plant Cell Environ. 2002 Feb;25(2):251-263
references.pmid: 11841668
references.citation: Oecologia. 2003 Aug;136(3):383-93
references.pmid: 12811534
references.citation: Science. 1999 Dec 10;286(5447):2184-8
references.pmid: 10591655