Climatic impacts on phenology in chaparral- and coastal sage scrub-dominated ecosystems in southern California using MODIS-derived time series
Abstract
Remote sensing monitoring of vegetation phenology can be an important tool for detecting the impacts of climate change on whole ecosystem functioning at local to regional scales. This study elucidates climate-phenology relations and the changes occurring in the phenology of both chaparral and coastal sage scrub-dominated ecosystems in southern California. Whole ecosystem phenology is monitored for the period 2001-2012 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 time series with temperature, precipitation, and Palmer Drought Severity Index (PDSI) data and by computing time series phenology metrics. Overall we find that the vegetation index values have fluctuated around a stable mean for vegetation types for the entire time period. However, interannual variability is high, likely due to annual variations in climate. The most significant statistical correlation in chaparral ecosystems were found between NDVI and PDSI, indicating that chaparral phenology is likely driven by drought and soil water deficit at the multi-monthly timescale. However, coastal sage scrub correlations were highest between NDVI and temperature + precipitation combined with no time lag. This reflects a more immediate response by these shallow rooted and deciduous species. The start of the growing season in both plant communities occurred early in rainy years, and later in years with lower PDSI (drought-associated). This suggests that future predicted climate change in southern California may cause increased interannual variability in chaparral phenology cycles, with early initiation of the growing season occurring in years following large rain events, and later initiation in drought years. Coastal sage scrub-dominated areas will be less influenced by lower frequency, long-term drought, but more immediately affected by discrete precipitation events and timing.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B43C0507W
- Keywords:
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- 0429 BIOGEOSCIENCES Climate dynamics;
- 0480 BIOGEOSCIENCES Remote sensing;
- 0476 BIOGEOSCIENCES Plant ecology