Metadata

Description
All measurements were collected at site TS/Ph-7 in the Florida Coastal Everglades (FCE) LTER. TS/Ph-7 is located approximately 1.5 km inland from the mouth of Taylor River in southeastern FCE. Duplicate mangrove vegetation plots (20 x 20 m) were established in December 2000 perpendicular to the shoreline (i.e., Taylor River) at 50 and 90 m in the fringe and interior scrub red mangrove-dominated zones, respectively, to monitor forest structural attributes, productivity, and soil biogeochemical properties. The mangrove forests at TS/Ph-7 are classified as scrub mangroves, because phosphorus limitation and permanent flooding constrain mangrove forest growth and development.
Due to the stunted physiognomy of the forest at TS/Ph-7, eight distinct mangrove islands of similar size (3-5 m in diameter) were selected and treated as experimental units for repeated measurements of leaf photosynthesis and physicochemical variables from January to December 2019. Mangrove islands were selected within the permanent vegetation plots based on their location relative to the shoreline (i.e., Taylor River), with four islands located in the fringe mangrove zone (~50-60 m from the edge) and four islands located in the interior forest (~100-110 m inland; Figure 1). Mangrove islands are characterized by a distinct elevation gradient, with higher soil elevation at the center of islands and lower elevation range at the edge of islands. Differences in elevation between center and edge habitats of the mangrove islands averaged 30 cm. Soil surface elevation at each habitat was measured using real-time kinematics referenced to the NAVD88 datum with a Trimble R8 high precision GPS system ( Trimble, Sunnyvale, CA).
Water levels relative to the soil surface were measured monthly with a meter stick at each of the permanent aluminum rods established at all island habitats. A porewater sample was collected at 30 cm depth at each habitat using a 60 ml syringe attached to a stopcock and a rigid tubing probe (3/16” diameter). Porewater temperature and salinity were measured using a handheld YSI conductivity-salinity-temperature meter (model Pro 30, YSI Incorporated, Yellow Springs, OH). A sample of surface water (when present) was also collected at each island habitat to measure salinity and temperature.
Leaf gas exchange data were collected monthly using the Li-6800 portable gas exchange system (Li-COR Inc., Lincoln, NE). During each sampling date, five mature green leaves were randomly selected from top mangrove branches. Fully developed and healthy (i.e., without herbivory) green leaves from the second-most distal pair of leaves on the leaf rosette were chosen. The Li-6800 was clamped onto each leaf and held until machine stability was reached, wherein data points were logged. During each sampling date, five leaves per habitat type were randomly chosen from the second-most terminal leaf pair on the leaf rosette in order to control for leaf ontogeny. The Li-6800 was clamped on the leaf and allowed to stabilize before logging data points. Eighty measurements were taken per sampling period with the environmental set up / machine configuration as follows: Flow - automatic at high (~1500 µmols s-1), H2O_r - set to RHair (which varied between 50-70%), CO2_r - 400 ppm, Fan - automatic (high), Air temperature - set to Tair, Light (Qin) – set to 1000 µmols m-2 s-1 (which was determined to be non-limiting based on data from a quantum senor on a eddy co-variance tower at the TS/Ph-7). The stability criteria (5) for the logging of data points with Li-6800 were as follows (note: Std = standard deviation, Slp = slope): deltaH2O (Meas2): Slp<1, Ci (GasEx): Slp<5, A (GasEx): Slp<1, gsw (GasEx): Slp<0.5, E (GasEx): Std<1, all of which were assessed over a 15s interval.
Leaves were collected every three months and analyzed for morphological traits and tissue nutrients. Leaf morphological data were measured by scanning leaves and recording their fresh and dry weights. Scanned images were processed in imageJ for morphological parameters. Leaf total carbon and nitrogen content were determined for homogenized leaf tissue samples with a NA1500 elemental analyzer (Fisons Instruments, Inc., Danvers, MA). Total phosphorus (TP) was extracted using an acid-digested (HCl) extraction, and concentrations of soluble reactive P were determined by colorimetric analysis. Leaf C and N bulk isotopic signatures (δ13C, δ15N) were analyzed on a Thermo Scientific Delta V Plus CF-IRMS coupled to an 1108 elemental analyzer via a ConFlo IV interface (Thermo Fisher, Waltham, MA).