DOI: 10.5061/dryad.1hn2b
title: Data from: Contrasting effects of nutrient enrichment on below-ground biomass in coastal wetlands

description: Anthropogenically-enhanced nutrient availability is often cited among the
 most important drivers of altered ecosystem function and loss of services
 worldwide. Although the above-ground consequences of nutrient enrichment
 on plant growth patterns are numerous and well-documented, below-ground
 impacts are less clear but nonetheless critical from a global change
 perspective. In coastal wetlands, for example, plant-soil-nutrient
 dynamics directly affect the capacity to sequester carbon as soil organic
 matter, keep pace with sea level rise, and resist storm-induced erosion.
 Here, we investigate the effects of excess nutrient loading on
 below-ground plant growth in an oligohaline marsh fertilized for seven
 years with a factorial combination of nitrogen (N) and phosphorus (P). We
 used two common assessment procedures, the ingrowth and standing crop
 methods, to simultaneously quantify distinct aspects of below-ground plant
 growth: 1) below-ground biomass accumulation into unexploited open
 resource space, and 2) in situ, or maintenance, below-ground biomass of
 plants in equilibrium with their environment, respectively. Our objective
 was to determine if plant growth responses to nutrient enrichment differed
 depending on process and/or biomass component measured. We show that
 excess N concurrently increased live root biomass accumulation in ingrowth
 cores and reduced in situ live root standing crop. Similar, albeit
 non-significant, response trajectories were apparent for other
 below-ground biomass pools using both methods, excepting dead biomass and
 total standing crop. A review of previously published research supports
 our results and suggests that nutrient enrichment consistently has
 contrasting effects on below-ground plant growth depending on whether
 biomass accumulation or standing crop is measured, and that living biomass
 components are most responsive to enhanced nutrient availability.
 Synthesis. We conclude that eutrophic conditions can be both beneficial
 and detrimental to ecosystem function by either stimulating below-ground
 biomass accumulation in unexploited soil or reducing the below-ground
 standing crop required to sustain the nutritional needs of established
 plants in mature communities. Thus, nutrient enrichment may, in the
 short-term, contribute to soil organic matter (i.e., carbon) accumulation
 by increasing below-ground growth as plants exploit new resource space.
 Over the long-term, however, nutrient enrichment has the potential to
 negatively impact soil organic matter content as plants equilibrate to
 excess nutrient availability by down-regulating below-ground standing
 crop.
description: Coastal Wetland
 Belowground BiomassThese data were
 collected in the field in 2008 from a Sagittaria lancifolia L. dominated,
 oligohaline marsh located along the west bank of the Tchefuncte River,
 approximately 1 km north of Lake Pontchartrain, LA, USA (30° 23.205’N, 90°
 09.551’ W). Two methods were used to estimate belowground biomass: the
 ingrowth method and the standing crop method. Abbreviated headings are as
 follows: "Block" = statistical block; "N" = nitrogen
 enrichment treatment (kg/ha/yr); "P" = phosphorus enrichment
 treatment (kg/ha/yr); "LRoot IG" = live root biomass in ingrowth
 cores (g/m2); "LRhiz IG" = live rhizome biomass in ingrowth
 cores (g/m2); "Live IG" = live root+rhizome biomass in ingrowth
 cores (g/m2); "Dead IG" = dead root+rhizome biomass in ingrowth
 cores (g/m2); "Total IG" = total live+dead biomass in ingrowth
 cores (g/m2); "LRoot SC" = live root biomass in standing crop
 cores (g/m2); "LRhiz SC" = live rhizome biomass in standing crop
 cores (g/m2); "Live SC" = live root+rhizome biomass in standing
 crop cores (g/m2); "Dead SC" = dead root+rhizome biomass in
 standing crop cores (g/m2); "Total SC" = total live+dead biomass
 in standing crop cores (g/m2).Belowground
 Biomass.csv