Abstract
Near surface (i.e., camera) and satellite remote sensing metrics have become widely used indicators of plant growing seasons. While robust linkages have been established between field metrics and ecosystem exchange in many land cover types, assessment of how well remotely-derived season start and end dates depict field conditions in arid ecosystems remain unknown. We evaluated the correspondence between field measures of start (SOS; leaves unfolded and canopy greenness >0) and end of season (EOS) and canopy greenness for two widespread species in southwestern U.S. ecosystems with those metrics estimated from near-surface cameras and MODIS NDVI for five years (2012–2016). Using Timesat software to estimate SOS and EOS from the phenocam green chromatic coordinate (GCC) greenness index resulted in good agreement with ground observations for honey mesquite but not black grama. Despite differences in the detectability of SOS and EOS for the two species, GCC was significantly correlated with field estimates of canopy greenness for both species throughout the growing season. MODIS NDVI for this arid grassland site was driven by the black grama signal although a mesquite signal was discernable in average rainfall years. Our findings suggest phenocams could help meet myriad needs in natural resource management.
Highlights
Phenology—the timing of seasonal life cycle events in plants and animals—is an integrative indicator of species’ responses to environmental conditions [1,2]
This study demonstrates that phenocams are a reliable source of data that can bridge species-specific field observations with those from satellites to yield better interpretations of land surface phenology in arid ecosystems
In the mixed grass-shrub system examined here, the dominant C4 grass and C3 shrub responded to different drivers within years as shown by growing season lengths and between years in response to rainfall demonstrated by the muted grass response in 2012 and the bi-modal response in 2016 shrub greenness
Summary
Phenology—the timing of seasonal life cycle events in plants and animals—is an integrative indicator of species’ responses to environmental conditions [1,2]. Spatiotemporal trends derived from phenological data (e.g., timing of initial growth, peak greenness, or flower and fruit production in plants) have been pivotal for addressing a range of research questions These include but are not limited to plant and ecosystem responses to climate change [3,4,5,6], the potential for ecosystem change to modify ecosystem services [7,8], and the alteration of ecosystems following species invasions [9]. Phenological metrics such as the start and length of growing season can be used to map land cover types or plant distributions [16] that aid remote assessments of landscape change [17,18] While such management applications are broadly relevant, they are relevant to the large expanses of arid and semi-arid landscapes in the western U.S under federal stewardship
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