Characterizing Seasonal Patterns of Leaf Phenology in Central Amazon Várzea Forest with the MODIS Enhanced Vegetation Index L. Hess, P. Ratana, A. Huete, C. Potter, and J. Melack LBA-ECO Investigation LC-32 (Melack/Novo)

12345Total % of total area % of total vegetated area Forested areas on mainstem várzea Total area: 98,100 km 2 Total forested area*: 61,500 km 2 *including closed shrub canopy

Many várzea tree species are flood-deciduous There is high spatial and temporal heterogeneity in patterns of leaf-fall Few field measurements – difficult to characterize

- Can we use satellite datasets to detect which areas of várzea forest are flood-deciduous, and when? Input to biogeochemical models (NASA-CASA) Better understanding of várzea forest functional ecotypes Significance as food resource (folivores, detritivores) - Good results with MODIS EVI for seasonal signals from other forest types suggest its use for this application

Schöngart, Piedade, Ludwigshausen, Horna, & Worbes, 2002, Phenology and stem-growth periodicity of tree species in Amazonian floodplain forests. J. Tropical Ecology 18: Sch ö ngart et al (Marchantaria Island) - Four functional dry forest ecotypes of Borchert (1994): evergreen (flush/shed constantly, never leafless) brevi-deciduous (short bare period followed by leaf flush) deciduous (trees remain bare until re-hydration by rainfall) stem-succulent (shed leaves; flush not dependent on rainfall) - Functional ecotypes concept convincingly explains phenological response as a reaction to water stress (not to photoperiod) - For all ecotypes, peak leaf shedding occurs during the first half of the aquatic phase, and peak leaf flushing in the late flooded period; there are differing time lags between fall and flush

Schöngart, Piedade, Ludwigshausen, Horna, & Worbes, 2002, Phenology and stem-growth periodicity of tree species in Amazonian floodplain forests. J. Tropical Ecology 18: Schöngart et al. 2002: Fall/flush lag times for ecotypes Evergreen DeciduousBrevi-deciduous

Haugaasen & Peres 2005: Lower Purus floodplain, adjacent várzea, igapó, and terra firme stands - phenological patterns for all 3 types are largely predictable - flood pulse is main driver for várzea and igapó; rainfall and solar irradiance are important for terra firme - peak shedding March to August for várzea and igapó, August to September for terra firme T. Haugaasen & C. Peres, 2005, Tree phenology in adjacent Amazonian flooded and unflooded forests. Biotropica 37:

MOD13Q (16-day, 250 m) EVI, NDVI, and VI Quality for várzea forest polygons, all classified as seasonally flooded forest on JERS mosaics; all closed canopy based on Landsat, video 12 to 56 pixels per polygon; sites 8,9,10 correspond to Haugaasen & Peres sites Cabaliana Purus Badajos Manacapuru gauge 100 km

Pixels with VI QA value > 3 for a given date were eliminated from calculation of the polygon median for that date.

Badajos Purus Cabaliana Smoothed EVI curves for Badajos, Purus, and Cabaliana sites, relative to Solimões River stage at Manacapuru

Inter-site comparison timing is almost the same amplitude of EVI cycle differs for the three reaches related to topographic position and/or functional ecotypes?

All sites: Badajos (black), Purus (red), Cabaliana (green)

Lower amplitude for high-levee sites

Flooding, or just time of year? Gray bars = +/- 32 days

May revise original assumption that we need to average over polygons and use QA-filtered pixel values (or fitted curves) directly.

Conclusions All sites showed a regular seasonal variation in EVI, ranging from a mean low for all sites of 0.41 to a mean high of The amplitude of variability in NDVI was about 50% that of EVI. Minimum EVI, corresponding to minimum leaf area, occurred in late May about one month preceding maximum river stage, and EVI peaked in mid-October, about 40 days before lowest river levels. The phase of the EVI curve was opposite to that of river stage and offset days in advance. Timing of min/max EVI agrees well with field observations of individual trees from Marchantaria and lower Purus Variability in timing and amplitude of seasonal EVI within the three reaches was as great as the variability between reaches. Amplitude of the EVI curve was lower for high levee sites; otherwise, no clear differences between high-, mid-, and low-levee Pixel-based analysis may be feasible, if filtered using QA

Caveats Not applicable to narrow levees, scroll-bar relief: scale issues Need to examine values for rivers (Juruá, Purus) where flood cycle is significantly offset from that of central Amazon, to separate effect of solar irradiance from that of flooding Next steps Extend measurements to broader geographic region, including blackwater and clearwater floodplains Use new ALOS PALSAR datasets to better discriminate flooded forest types (based on inundation period) and compare signals How to relate the EVI signal to litterfall rates? Practical demonstration as NASA-CASA model input

ALOS data to select areas Thank you for your attention!