Nitrogen and phosphorus have individually or jointly been demonstrated to limit primary productivity in most of Earth’s forested systems. Nutrient limitation of forest primary productivity is important because terrestrial systems currently store large amounts of carbon and partially mitigate carbon dioxide emissions from anthropogenic activities. There is also evidence that nutrient availability relative to demand is decreasing in forested systems. Trees have complex responses to nutrient availability, including changes in allocation of nutrients to different organs and mechanisms that aide in recycling of nutrients within the plant and ecosystem. In this work I provide new insight related to nutrient allocation and conservation mechanisms in trees, demonstrating that these mechanisms affect nutrient limitation of primary productivity. In Chapter 2, I provide evidence that tree reproductive organs have nutrient resorption processes that transfer nutrients from fruit to seeds and I also demonstrate that tree fruit are capable of photosynthesis – in the absence of such processes the carbon and nutrient costs of tree reproduction would likely be higher. In Chapter 3, I report on the results of a community science project through which I identified variation in biogeochemically relevant leaf traits across much of the geographic distribution of Acer rubrum, one of North America’s most broadly distributed tree species, demonstrating that foliar nitrogen resorption is highest in colder high latitudes and leaf litter %N is highest at warmer low latitudes. In Chapter 4, I compare leaf and reproductive litterfall nitrogen and phosphorus metrics worldwide and demonstrate that reproductive litterfall is a significant contributor to tree nutrient budgets, comprising a median of 13.0% and 16.1% of nitrogen and phosphorus fluxes, respectively, when combining leaf and reproductive litterfall. Overall, the results of my dissertation enable me to identify several understudied aspects of tree nutrient allocation and conservation processes by considering the biogeochemistry of reproductive and foliar organs and associated variation across the natural distribution of trees.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/47669 |
| Date | 17 November 2023 |
| Creators | Gougherty, Steven William |
| Contributors | Templer, Pamela H. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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