# Analyzing the Long-Term Phenological Trends of Salt Marsh Ecosystem across Coastal LOUISIANA
## Materials and Methods
### Trend Analysis  
In order to highlight the spatial distribution of the marsh pixels showing improvement (positive change) and stress/degradation (negative change), we employed the Mann-Kendall (MK) trend test [88] to determine the phenological changes of the salt marshes of southeast and southwest LA between 2000-2015, using R [89]. We calculated the MK trend test separately for every pixel for base value, amplitude, max value, and small seasonal integral composites for the southeast and southwest LA salt marshes. These parameters are crucial indicators of seasonal productivity. We classified changes based on the z-score distribution at a 95% confidence interval. A positive or negative value of z represented an upward or downward trend, respectively. Changes beyond the lower critical limit  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Seasonality Parameters** & **Description/Phenological Interpretation** & **Unit** \\ \hline Start of Season (SOS) & Time at the beginning of the growing season, when GBM begins to increase and photosynthesis starts & Julian days starting from January 1 \\ \hline End of Season (EOS) & Time at the end of growing season, when GBM begins to decrease and photosynthesis stops completely & Julian days starting from January 1 \\ \hline Peak of Season (POS) & Computed as the mean of the time period for which the green-up process stops and brown-down starts; time when the GBM and photosynthesis reach their & Julian days starting from January 1 \\ \hline Length of Season (LOS) & Time from start to end of growing season & Days \\ \hline Base Value & Mean of the minimum GBM values at the start (initial GBM and end (final GBM) of the growing season & GBM unit \\ \hline Max Value & Maximum GBM value for the fitted function during the growing season/ GBM value during the peak of the growing season & GBM unit \\ \hline Amplitude & Difference between the base and max value; Maximum increase in canopy photosynthetic activity above & GBM unit \\ \hline Left Derivative & Rate of green-up; rate of increase of GBM values from the beginning till the peak of the growing season & GBM unit/8 days \\ \hline Right Derivative & Rate of brown-down; rate of decrease of GBM values from the peak to the end of the growing season & GBM unit/8 days \\ \hline Small Seasonal Integral & Integral of the function describing the season from the start to end of the season, above the base level; indicator of net canopy photosynthetic rate across the entire growing season & GBM unit \\ \hline Large Seasonal Integral & Integral of the function describing the season from start to end of the season; indicator of gross canopy & GBM unit \\ \hline \hline \end{tabular}
\end{table}
Table 1: Seasonality Parameters Estimated by TIMESAT. GBM: green biomass.  
(z \(<-1.96\)) were classified as a strong negative change, while those beyond the higher critical limit (z \(>\) 1.96) were classified as a strong positive change. Changes within the 95% confidence interval were classified as weak (negative or positive depending on negative or positive values of z).