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Abstract Detail

Ecological Section

Petersen, Sheryl [1], Carrino-Kyker, Sarah [1], DeForest, Jared [2], Hewins, Charlotte [1], Shaw, Alanna [3], Smemo, Kurt [1], Burke, David [4].

Tree responses to experimental pH and phosphorus elevation in acidic temperate hardwood forests.

Temperate hardwood forests are typically considered nitrogen limited, but decades of anthropogenic nitrogen and acid deposition may have caused these forests to transition towards phosphorus (P) limitation. However, few studies have documented P limitation in temperate hardwood trees in regions with significant levels of acid deposition. P limitation in temperate trees may not occur if plants become increasingly dependent on mycorrhizal fungi for acquiring P in acidic soils. However, the link between pH and inorganic P availability has seldom been explicitly examined. We increased soil pH and P availability in a factorial ecosystem-level experiment using a total of 72 plots across glaciated and unglaciated temperate forests of eastern Ohio. These manipulations were initiated in 2009 and raised pH by 1.5 units and increased labile P 3-fold. We examined treatment effects on productivity using estimates of tree growth rate and foliar biomass. Growth was calculated from annual diameter measurements. Foliar biomass was estimated from leaf litter harvests. We also evaluated indicators of nutrient limitation by quantifying foliar nutrients in Acer (maples). Three years after treatment initiation, collective tree growth did not differ with treatment, even when trees were categorized by their primary mycorrhizal fungal associations. However, ectomycorrhizal (EcM)-associated species grew 74% more than arbuscular mycorrhizal (AM)-associated species and one of the dominant EcM-associated genera, Quercus (oaks), grew 30% less in plots with elevated pH compared to control plots. This was not the case for Acer – the dominant AM-associated genera – for which growth did not significantly differ by treatment. Similarly, from 2010-2011, total litter production did not respond to treatment. However, in 2012, litter production was 50% less in plots with elevated pH, but only in unglaciated southern Ohio. By contrast, preliminary foliar nutrient analysis indicates trees responded more to phosphorus manipulations than pH. In 2011, Acer foliar N:P ratio was 28% lower in elevated-P plots in unglaciated southern Ohio, suggesting that these forests might be more phosphorus limited than those in glaciated northern Ohio. Overall, trees in southern Ohio on unglaciated soils responded more strongly to manipulations of pH and P availability. However, changes in productivity in response to pH appear uncoupled from the foliar responses to P manipulation. This may be because changes in productivity, particularly tree growth, lag behind foliar response to nutrient manipulation. We will address these questions as we continue to monitor changes in productivity and expand the examination of foliar nutrients to additional species.

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1 - The Holden Arboretum, Kirtland, OH
2 - Ohio University, Department of Environmental and Plant Biology, Athens, OH
3 - MPG Ranch, Missoula, MT
4 - The Holden Arboretum, 9500 Sperry Road, Kirtland, OH, 44094, USA


Presentation Type: Oral Paper:Papers for Sections
Session: 10
Location: Ascot/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 1:45 PM
Number: 10002
Abstract ID:417
Candidate for Awards:None

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