University of Minnesota
University of Minnesota
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Methods for Experiment 136 -

aefe136 - Acorn production

Acorn production

Acorn production was quantified between late July and late August from 1995 to 2011 using visual surveys in which two observers scanned different parts of each tree canopy and counted as many acorns as they could in 15 s (Koenig et al. 1994a). Counts for the two observers were added to equal a 30 second count. 212 marked trees of four species, including bur oak (Quercus macrocarpa Michx., N = 90), Northern pin oak (Q. ellipsoidalis E.J.Hill, N = 90; subsequently referred to as pin oak), white oak (Q. alba L., N = 11), and red oak (Q. rubra L., N = 21). Trees that died during the study were not replaced. Trees of three of the four species (all except for Q. alba) were divided among six burn units differing in size from 2.4 to 30 ha and varying in the frequency of prescribed burning. Prescribed burns occurred in April or May after the snow melted but before trees leafed out; fire intensity varied depending on the weather and fuel load but was typically of low intensity (Reich et al. 2001; Cavender-Bares and Reich 2012). Fire frequency ranged from 0 to 12 fires during the 17-year study depending on the unit. Method references cited: Koenig WD, Knops JMH, Carmen WJ, Stanback MT, Mumme RL (1994a) Estimating acorn crops using visual surveys. Can J For Res 24:2105?2112 Reich PB, Peterson DW, Wedin DA, Wrage K (2001) Fire and vegetation effects on productivity and nitrogen cycling across a forest-grassland continuum. Ecology 82:1703?1719 Cavender-Bares J, Reich PB (2012) Shocks to the system: community assembly of the oak savanna in a 40-year fire frequency experiment. Ecology 93:S52?S69 Published results from this data in: Koenig, Walter D.; Knops, Johannes M. H.; Environmental correlates of acorn production by four species of Minnesota oaks; Population Ecology, 2013, 1-9, DOI 10.1007/s10144-013-0408-z 2013

aehe136 - Oak diameter at breast height

Oak diameter at breast height

Oak diameter at breast height was measured sometime between 1995 and 1998.