Asynchronous phenologies of photosynthetic carbon assimilation and tree-growth in temperate oaks scaled from cells to sa
Photosynthesis and tree-growth are interconnected processes that are independently modulated by environmental variables. The lack of co-located high spatiotemporal resolution measurements of photosynthesis and growth has limited our understanding of their relationship with each other and their environment. Here, we study photosynthesis and tree-growth at near-instantaneous timescales using in-situ and satellite remote-remote sensing, point dendrometers, quantitative wood anatomy, and Pulse Amplitude Modulated chlorophyll fluorescence. Tree and leaf-level measurements are being made on eight oak (Quercus spp.) trees in a temperate forest in southern New York. Specifically, we will determine the periods of initiation and cessation of tree-growth, the periods of canopy development and senescence, and the attainment and loss of the full photosynthetic capacity. Preliminary data for 2021 suggests that oaks commenced radial growth in the first week of April approximately one-month prior to canopy development that was not completed until the first week of May. Further, the development of foliar photosynthetic capacity lags leaf expansion by nearly two weeks. This two-week lag between the completion of leaf expansion and subsequent development of photosynthetic capacity is not captured by conventional remote sensing metrics. Further, we find that oak growth for the season is completed by early August while high levels of photosynthetic activity are maintained for three additional months until early November. Finally, we show that oak tree-ring width network for the Northeastern US reflect these lag effects between photosynthetic carbon assimilation and tree-growth.