DOI: 10.5061/dryad.v15dv4231
title: Contrasting responses of fine root biomass and traits to large-scale nitrogen and phosphorus addition in tropical forests in the Guiana shield

description: Fine roots mediate plant nutrient acquisition and growth. Depending on
 soil nutrient availability, plants can regulate fine root biomass and
 morphological traits to optimise nutrient acquisition. Little is known,
 however, about the importance of these parameters influencing forest
 functioning. In this study, we measured root responses to nutrient
 additions to gain a mechanistic understanding of plant adaptations to
 nutrient limitation in two tropical forests in French Guiana, differing
 two-fold in their soil nutrient statuses. We analysed the responses of
 root biomass, mean root diameter (RD), specific root length (SRL),
 specific root area (SRA), root tissue density (RTD) and carbon (C),
 nitrogen (N) and phosphorus (P) concentrations in roots down to 15 cm soil
 depth after three years of N and P additions. At the lower-fertility site
 Paracou, no changes in root biomass or morphological traits were detected
 with either N or P addition, although P concentrations in roots increased
 with P addition. In the higher fertility site, Nouragues, root biomass and
 P concentrations in roots increased with P addition, with no changes in
 morphological traits. In contrast, N addition shifted root traits from
 acquisitive to more conservative by increasing RTD. A significant
 interaction between N and P in Nouragues pointed to stronger responses to
 P addition in the absence of N. Our results suggest that the magnitude and
 direction of root biomass and trait expression were regulated by soil
 fertility, corroborated by the response to N or P additions. At low
 fertility sites, we found lower plasticity in root trait expression
 compared to more fertile conditions, where N and P additions caused
 stronger and antagonistic responses. Identifying the exact role of
 mechanisms affecting root nutrient uptake in Amazon forests growing in
 different soils will be crucial to foresee if and how rapid global changes
 can affect their carbon allocation.
description: # Contrasting responses of fine root biomass and traits to large-scale
 nitrogen and phosphorus addition in tropical forests in the Guiana shield
 Data regarding fine root
 (roots smaller than 2 mm in diameter) biomass stocks, root morphological
 traits, and nutrient concentration and stocks in fine roots and soils down
 to 15 cm depth in two forests in French Guiana. Data were sampled in the
 dry and wet seasons of 2019. These two forests received 3 years of
 factorial nutrient addition, with control plots and plots with the
 addition of nitrogen, phosphorus and nitrogen and phoshorus in
 combination. Each site comprises 12 plots (3 per treatment) measuring 50 x
 50 m, and in each plot, 5 samples were collected in each season, in the
 inner 30 x 30 m. These data therefore, report belowground data from the
 two sites belonging to the large-scale nutrient fertilisation IMBALANCE-P.
 ## Description of the data and file structure The data consist of one
 table with 32 columns and below the abbreviations and units are described
 in detail. **Site:** Two study sites in French Guiana; Paracou (PAR) and
 Nouragues (NOU) **Topo:** Three different terrain topographies frm which
 data was collected (bottom plots, slope plots and Top plots) **Treat:**
 four different treatments applied for each site and topographies. C is for
 control plots without nutrient addition; N is for plots with nitrogen
 addition; P is for plots with phosphorus addition and NP is for plots with
 the addition of both nitrogen and phorphorus together **Plot_n:** refers
 to the treatments in a numerical form. 1 refers to N treatment plots, 2
 refers to NP treatment plots, 3 for P plots and 4 for control plots.
 **Date:** Date that samples were collected in the field (ex. 201905, May
 2019) **Season:** Seasons of sampling; dry and wet **N_treat:** Presence
 (1) and absence (0) of nitrogen addition **P_treat:** Presence (1) and
 absence (0) of phosphorus addition **mean_finerootstocks_Mg_ha:** Fine
 root (&lt;2mm diameter) biomass stocks down to 15 cm soil depth in Mg/ha
 **mean_Cstock_Mg_ha:** Fine root (&lt;2mm diameter) biomass stocks of
 carbon down to 15 cm soil depth in Mg/ha **mean_Nstock_kg_ha:** Fine root
 (&lt;2mm diameter) biomass stocks of nitrogen down to 15 cm soil depth in
 kg/ha **mean_Castock_kg_ha:** Fine root (&lt;2mm diameter) biomass stocks
 of calcium down to 15 cm soil depth in kg/ha **mean_Mgstock_kg_ha:** Fine
 root (&lt;2mm diameter) biomass stocks of magnesium down to 15 cm soil
 depth in kg/ha **mean_Kstock_kg_ha:** Fine root (&lt;2mm diameter) biomass
 stocks of potassium down to 15 cm soil depth in kg/ha
 **mean_Pstock_kg_ha:** Fine root (&lt;2mm diameter) biomass stocks of
 phosphorus down to 15 cm soil depth in kg/ha **mean_diam_mm:** Mean fine
 root diameter in mm **mean_SRL_m_g:** Specific root length in m/g
 **mean_SRA_cm2_g:** Specific root area in cm2/g **mean_RTD_g_cm3:** Root
 tissue density in g/cm3 **mean_C_root_%:** Carbon concentration in fine
 roots in % **mean_N_root_%:** Nitrogen concentration in fine roots in %
 **mean_Ca_root_mg_kg:** Calcium concentration in fine roots in mg/kg
 **mean_Mg_root_mg_kg:** Magnesium concentration in fine roots in mg/kg
 **mean_K_root_mg_kg:** Potassium concentration in fine roots in mg/kg
 **mean_P_root_mg_kg:** Phosphorus concentration in fine roots in mg/kg
 **NP_ratio_root:** Ratio nitrogen to phosphorus concentrations in fine
 roots **CP_ratio_root:** Ratio carbon to phosphorus concentrations in fine
 roots **mean_Csoil_%:** Carbon concentration in soils down to 15 cm in %
 **mean_Nsoil_%:** Nitrogen concentration in soils down to 15 cm in %
 **mean_Psoil_mg_kg:** Phosphorus concentration in soils down to 15 cm in
 mg/kg **Pstock_soil_kg_ha:** Phosphorus stocks in soils down to 15 cm in
 kg/ha **mean_bulk_g_cm3:** Soil bulk density down to 15 cm in g/cm3 NA in
 table cells denote data not available. ## Sharing/Access information Data
 from aboveground responses to nutrient addition in the same plots and
 sites, used in the supplementary material of this manuscript, can be found
 in full at: * *