DOI: 10.5061/dryad.jq2bvq8fx
title: Data from: 28 years of vegetation standing crop data from the Mississippi river delta

description: Deltaic landscapes go through cycles of birth, growth, decline, to death
 governed by intertwined geological, biological, and ecological
 processes.  This study tracks deltaic lobes in the Balize
 Mississippi River Delta, Louisiana, USA over ~3 decades (study years
 1984–2012). Hydrologic and geomorphic patterns and those which sustain
 patterns to wetland plant richness, diversity, and biomass are
 described.  Plant diversity and biomass were modeled by nMDS
 ordination.  Taxa (53) were harvested and dried (116,706g) from
 965 (0.25 m2) plots and divided into three groups: I. 4 Foundation
 Species; 78.9% of total harvest; II. 9 Pioneer Species; 13.6% of total
 harvest; III. All Other taxa; 7.5% of total harvest (8 Miscellaneous
 Grasses, 8 Miscellaneous Sedges, 24 Miscellaneous Herbs). 
 Autogenic/allogenic processes (sedimentation, subsidence, plant
 colonization, succession events) affect composition and biomass. 
 Eleven important species were identified.  Taxa’s richness
 increased on mudflats during primary succession (15 to 25 taxa per site),
 then declined to fewer than 5 per site.  Niche-space theory
 explained patterns to community change.  There was similar total
 biomass/yr (~500 g/m2/yr) at study sites.  Quantile regression
 analyses showed water quality and quantity of the Mississippi River
 influenced biomass especially spring-time waters.  Stochastic
 events (storms, herbivory, salt-burn, flood-pulses) impacted biomass.
 Long-term studies like this are required in a future of climate unknowns.
description: In 1984 three sites were chosen for study; two sites on 2yr old
 (determined from NASA photographic records) rapidly elongating lobes of
 the BS; a north site (BSn) and a south site (BSs).  A third site was
 established ~150m inland from Octave Pass on the east side of the
 southeasterly dredged channel.  This constructed or created WSc site was
 originally a designed test location for wetland development to monitor
 with the two natural sites on BS.  Years later another lobe showed a
 future for growth on the same growing splay down flow from WSc but, not
 influenced by the dredged material from a decade before.  In 1994, this
 area was designated as the new WSn site. In 1984 at BSs, BSn, WSc, and at
 WSn in 1994, study site transect locations for plant collection on the
 newly emerged sites were marked by permanent stakes mid-summer nearshore
 at the most distal growing ends of each site’s lobe. Each year of
 substantial accretion (which forced elongation of the lobes) additional
 transects were added; two by 1986 at WSc and BSn, and two by 1989 at BSs. 
 All lobes had to have elongated ~50m or more for a new transect.  No
 further transects were deemed necessary after sufficient plots were
 established to describe the lobe plant community (usually three transects
 each with five plots). At the time of usual flowering (late-August early
 September), the peak plant standing crop along each transect was clipped
 in 5 quarter-meter<sup>2</sup> (50cm x 50cm) plots separated
 by ~5 to 10m. All plant material, including the unidentifiable dead, was
 dried to constant weight and entered into Excel spreadsheets.  Voucher
 material was deposited in the herbarium of Tulane University, New Orleans,
 LA; since moved to the collections at Louisiana State University, Baton
 Rouge, LA.