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Fine root productivity varies along nitrogen and phosphorus gradients in high-rainfall mangrove forests of Micronesia

March 4, 2015

Belowground biomass is thought to account for much of the total biomass in mangrove forests and may be related to soil fertility. The Yela River and the Sapwalap River, Federated States of Micronesia, contain a natural soil resource gradient defined by total phosphorus (P) density ranging from 0.05 to 0.42 mg cm−3 in different hydrogeomorphic settings. We used this fertility gradient to test the hypothesis that edaphic conditions constrain mangrove productivity through differential allocation of biomass to belowground roots. We removed sequential cores and implanted root ingrowth bags to measure in situ biomass and productivity, respectively. Belowground root biomass values ranged among sites from 0.448 ± 0.096 to 2.641 ± 0.534 kg m−2. Root productivity (roots ≤20 mm) did not vary significantly along the gradient (P = 0.3355) or with P fertilization after 6 months (P = 0.2968). Fine root productivity (roots ≤2 mm), however, did vary significantly among sites (P = 0.0363) and ranged from 45.88 ± 21.37 to 118.66 ± 38.05 g m−2 year−1. The distribution of total standing root biomass and fine root productivity followed patterns of N:P ratios as hypothesized, with larger root mass generally associated with lower relative P concentrations. Many of the processes of nutrient acquisition reported from nutrient-limited mangrove forests may also occur in forests of greater biomass and productivity when growing along soil nutrient gradients.

Citation Information

Publication Year 2015
Title Fine root productivity varies along nitrogen and phosphorus gradients in high-rainfall mangrove forests of Micronesia
DOI 10.1007/s10750-015-2178-4
Authors Nicole Cormier, Robert R. Twilley, Katherine C. Ewel, Ken W. Krauss
Publication Type Article
Publication Subtype Journal Article
Series Title Hydrobiologia
Series Number
Index ID 70142275
Record Source USGS Publications Warehouse
USGS Organization National Wetlands Research Center