PS 64-63
Monitoring plant phenology in southern California National Parks: A remote-sensing based study from 2000-present
Remote sensing of vegetation phenology can be an important tool for detecting the impacts of climate change on whole-ecosystem functioning. Southern California has a particularly high level of biodiversity in combination with a high amount of ongoing human impact. It is therefore both a challenge and a necessity to provide adequate monitoring in order to apply effective conservation methods. This study elucidates climate-phenology relations and the phenological changes occurring in native chaparral and coastal sage scrub-dominated ecosystems in southern California National Parks, specifically the Santa Monica Mountains National Recreation Area and Channel Islands National Park. Ecosystem phenology is monitored for 2000-2014 within the Parks using the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) derived from MODIS MOD13Q1. Changes in phenology are assessed through a comparison of the vegetation index time series with raw data and anomalies of monthly temperature, precipitation, cumulative precipitation, and Palmer Drought Severity Index (PDSI) data.
Results/Conclusions
Overall, we find that the climate and vegetation indices are relatively stable for both vegetation types for the entire time period. Inter-annual variability is high, due to annual variations in climate. The most significant correlation in chaparral ecosystems was found between NDVI and PDSI, indicating that chaparral phenology is likely driven by drought and soil water deficit at the multi-monthly timescale. However, in coastal sage scrub communities correlations were highest between NDVI and discrete precipitation events and temperature fluctuations. Climate anomalies had little to no correlations with the vegetation indices, indicating that the phenology of these native plants may be highly resilient to short-term changes in climate. These time series data serve as an important baseline for conservation-based monitoring studies of whole ecosystem phenology in relation to climate change.