Spartina patens is grown in experimental elevation planters placed in draining ponds on the salt marsh platform. The planters are constructed from PVC pipes of varying lengths. All of the PVC pipes are open at the bottom, and flush to the mudflat surface of the pond, resulting in the tops of the pipes being situated at various relative elevations within the tidal range. Plants growing in the shorter PVC pipes are flooded for a longer duration of each tidal cycle than plants growing in the taller PVC pipes. The growth response of S. patens when exposed to different flood frequencies is monitored by destructive 'harvesting' of all above- and belowground plant material at the end of the growing season.
Experimental Elevation Planters:
There have been 4 experimental elevation planters located at Law's Pt. Each planter has 6 replicate pots each of 6 levels. Level 1 is the lowest level and is more frequently inundated than the other levels. Level 6 is the highest level and is inundated least frequently. Pots are constructed from varying lengths (in 15-cm increments) of 6" diameter PVC pipe. All of the PVC pipes are open at the bottom, and flush to the mudflat surface of the pond, resulting in the tops of the pipes being situated, step-wise, at various relative elevations within the tidal range. The entire structure resembles a staircase. Elevations of the pots in all 4 planters range from about 52 - 164 cm NAVD88. (about 0.5m above MSL to about 0.2m above MHHW). Planter 1 was established in 2002 and dismantled after the 2009 experiment. Planter 1 was planted exclusively with S. alterniflora (see LTE-MP-LPA-elev_planter). Planter 2 was established in 2006, and discontinued after it was dislodged by ice during winter 2014/2015. Planter 3 was established in 2015. Planter 4 was established in 2015.
Replicate pots are filled with sediment from the draining pond in which they are situated in either late fall or early spring. Plugs of S. patens are collected from the marsh platform near the planter, and transplanted into the pots. Every attempt is made to ensure that all plugs are the same size (surface area and depth) and contain the same number of plants of about the same height. However, particularly in spring, the natural marsh is not yet well established, and there is variability within the initial plantings. Marsh plugs are approximately 4" in diameter and 6" in depth.
Replicate pots are observed approximately monthly. Canopy height, presence/absence of flowers, presence/absence of non-S. patens plants, and plant condition (e.g. % live, % cover) are recorded.
At the end of the growing season (usually mid-Aug), the planter is 'harvested'. The contents of each replicate pot (live shoots, dead shoots, roots, rhizomes, peat, sediment, dead belowground macro organic matter) are removed from the planter. Shoots are clipped at the sediment surface, dried (60C) and weighed. Belowground portions from each pot are washed of sediment and seived (2.5mm) to collect all plant material (live and dead), dried (60C) and weighed.
Various monitoring, planting, and harvesting protocols (e.g. sorting into live, dead, roots, rhizomes etc) have been used to accomodate various experimental goals. In 2006 and 2007, belowground material in several representative pots was sorted into live and dead; the rest of the pots were not sorted. In 2015, belowground material in several representative pots was sorted into roots, rhizomes, and dead; the rest of the pots were not sorted.
Elevations of the pots relative to NAVD88 are determined by FastStatic measurements using a Trimble 4800 receiver and TSC-1 controller (from UNAVCO www.unavco.org).
Collections occur approximately monthly from May through September. Database is updated once annually, usually in the winter. Study and data collection are ongoing as of Sept 2016.
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