Multiscale modeling of spring phenology across Deciduous Forests in the Eastern United States

Abstract

Phenological events, such as bud burst, are strongly linked to ecosystem processes in temperate deciduous forests. However, the exact nature and magnitude of how seasonal and interannual variation in air temperatures influence phenology is poorly understood, and model-based phenology representations fail to capture local- to regional-scale variability arising from differences in species composition. In this paper, we use a combination of surface meteorological data, species composition maps, remote sensing, and ground-based observations to estimate models that better represent how community-level species composition affects the phenological response of deciduous broadleaf forests to climate forcing at spatial scales that are typically used in ecosystem models. Using time series of canopy greenness from repeat digital photography, citizen science data from the USA National Phenology Network, and satellite remote sensing-based observations of phenology, we estimated and tested models that predict the timing of spring leaf emergence across five different deciduous broadleaf forest types in the eastern United States. Specifically, we evaluated two different approaches: (i) using species-specific models in combination with species composition information to 'upscale' model predictions and (ii) using repeat digital photography of forest canopies that observe and integrate the phenological behavior of multiple representative species at each camera site to calibrate a single model for all deciduous broadleaf forests. Our results demonstrate variability in cumulative forcing requirements and photoperiod cues across species and forest types, and show how community composition influences phenological dynamics over large areas. At the same time, the response of different species to spatial and interannual variation in weather is, under the current climate regime, sufficiently similar that the generic deciduous forest model based on repeat digital photography performed comparably to the upscaled species-specific models. More generally, results from this analysis demonstrate how in situ observation networks and remote sensing data can be used to synergistically calibrate and assess regional parameterizations of phenology in models.

Tree Community Phenodynamics and Its Relationship with Climatic Conditions in a Lowland Tropical Rainforest

“…Over larger scales, ground-based phenology is also important to validate and calibrate global vegetation models used to predict the effects of future climate change on ecosystems [69,70]. Consistent data that permits the determination of the intensity of phenophases per area per month are scarce for tropical rainforests.…”

Phenocams Bridge the Gap between Field and Satellite Observations in an Arid Grassland Ecosystem

“…Seasonal metrics derived from high-frequency (i.e., multiple images day −1 ) phenocam images provide a link between satellite and field perspectives and have been used to refine phenological models for forested ecosystems in the eastern U.S. [25,26]. Use of images from near-surface phenocams can increase temporal resolution, broaden the spatial footprint of field observations, and reduce costs of field-based observations [27].…”

Extracting Plant Phenology Metrics in a Great Basin Watershed: Methods and Considerations for Quantifying Phenophases in a Cold Desert

“…These per channel DN values are commonly used to calculate various vegetation indices that represent vegetative response and vigor [4,6,15]. These methods have been shown to be quite robust for phenology and gross primary productivity of deciduous forests [16,17,18], and determining fractional snow cover [19]. However, Brown et al [9] proposed that far less is known about their robustness in temperate and tropical evergreen forests [20], and warm and cold desert environments [21].…”