Meadows and Conifer Encroachment: Effect of Soil Moisture and Location on Wet Meadow Encroachment by Lodgepole Pine

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Important for maintaining year-round water flow in Sagehen Creek

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Pinus contorta In Sagehen Creek Field Station, wet meadows are encroached specifically by the lodgepole pine. Lodgepole are strong competitors in wet environments, but suffer from root rot in saturated soils

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“In order to test for conifer encroachment we chose four large wet meadows…” All graphs showed some gradient of smaller pines near the interior of the meadow At each meadow, 4 transects were used for each cardinal direction Each transect was sampled at 4 points, representing a gradient of the meadow from inside the forest to 20m toward the interior of the meadow

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Tree growth was determined by felling the closest sapling to each transect point and comparing sapling height and diameter to age Analysis of tree growth as a response to local environment was done through determining the average growth rate of saplings and comparing individual deviation from mean to environment

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Our methods for finding soil moisture worked based on these results, however, there was no response from saplings

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Average Age vs. Transect Point Younger saplings are found just slightly within the meadow (5m away from the forest line) – saplings tend to be recruited close to their “parents” – additionally, their proximity to the forest and other trees could be an advantage in this ecosystem - experience less competition from meadow plants closer to the forest line These saplings also had the highest average growth rate but that is probably a result of age because age and growth had a negative relationship across all saplings – saplings tended to grow faster when they were younger

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Sapling Density vs. Direction of Transect Sapling density at meadow edge was found to vary with the cardinal direction that the meadow is facing Explain Graph The North and South edges of the meadows varied much less and tended to have fewer saplings present than the West and East edges. We hypothesize that this may be a result of the meadow’s orientation to the sun, with the west and east areas receiving less constant sun and thus being more conducive to sapling growth, though we are unsure of an explanation of this mechanism.

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It can be concluded that soil moisture has no effect on pine recruitment and is a result of factors outside the scope of this study Pine recruitment appears to be strongest near the periphery of meadow Using the measure of young pines as an indicator for an encroaching forest The factors that maintain meadows are obviously very complex and therefore a more elegant study design and broader scope is required to better understand ecosystem dynamics

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Soil moisture measurement methods appear accurate as a moisture gradient was found between the forest and meadow habitats Meadows are very unique, and there were statistical differences found between our meadows that made sampling difficult.

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Being able to determine the factors that influence meadow dynamics is critical for Sierra Forest ecosystems. As the climate continues to change and prolonged drought threatens California, wet meadows may become more vulnerable to drying and invasion by the forest, weakening the meadows’ ability to store carbon, contributing to the effects of climate change

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Meadows & Conifer Encroachment Effect of Soil Moisture and Location on Wet Meadow Encroachment by Lodgepole Pine Katie, Will, & Zach: CEC Summer 2018

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Montane Wet Meadow Functions Meadows serve critical functions for montane ecosystems Biodiversity hotspot Carbon store by stifling aerobic decomposition Retention of groundwater and maintenance of summer stream flow Meadow – Forest boundaries represent a complicated ecotone

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Conifer Encroachment Meadows shrink as conifers spread Conifers reduce soil moisture through evapotranspiration Wet meadows are especially vulnerable As climate change causes more severe droughts in California, encroachment could become more prevalent

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What biotic and abiotic conditions control the recruitment of lodgepole pine into wet meadows of Sagehen Creek Basin? Hypotheses: When high levels of water are present in soil, there will be less pine recruitment and meadow contraction. Similarly, the growth rate of pine saplings will decrease outside of the tree line due to less favorable conditions

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Methods & Study System We collected data on: Soil moisture Sapling density Growth rate of the nearest sapling sapling

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Methods: Sapling Growth Rate

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The soil moisture increases into the meadow There was no response to soil moisture from saplings

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Average Age of Sapling and Location in Meadow Average Age of Sapling (years) Distance into Meadow (m)

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Direction of Meadow Edge and Sapling Density Sapling per m^2 Cardinal Direction

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Discussion Based on our results, soil moisture has no effect on the growth or abundance of saplings in wet meadows Soil moisture has no effect on pine recruitment Pine recruitment appears to be strongest near the periphery of meadow

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Reflection and Future Study Other factors such as soil pH should be considered to determine factors impacting recruitment Study of seasonality across long term, use of GIS Investigation into impact of cardinal direction on pine growth We recommend future studies sample more meadows or focus more closely on a specific meadow

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Broader Impact

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Thanks! Special thanks to Justin and Kathleen for getting us the tools we needed To Tim for letting us ruin his finger saw And lastly, to the trees for giving their life’s in the name of science Any questions?

Summary: Summer, 2018

Tags: student project

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