DOI: 10.5061/dryad.h44j0zpkh
title: Ecosystem sulfur accumulation following woody encroachment drives a more open S-cycle in a subtropical savanna

description: Globally widespread woody encroachment into grass-dominated ecosystems has
 substantial consequences for carbon (C), nitrogen (N), and phosphorus (P)
 cycles. Despite its significance as an essential macronutrient, however,
 little is known regarding potential changes in the sulfur (S) cycle. We
 quantified S concentrations, stoichiometric relationships, and δ34S values
 in the plant-soil environment to investigate landscape-scale changes in
 the S cycle following grassland-to-woodland transitions in a subtropical
 savanna. Plant tissues of woody species had significantly higher S
 concentrations and δ34S values than those of herbaceous species, resulting
 in a landscape-scale correspondence between spatial patterns of S and δ34S
 in surface soils and vegetation distribution, with higher S and δ34S in
 soils beneath woody patches. These patterns were more subtle at soil
 depths &gt; 5 cm. Woody plants had higher N:S ratios but comparable
 P:S ratios relative to herbaceous species, which contributed to
 contrasting spatial patterns between N:S and P:S ratios in surface soils.
 Sulfur in surface soils increased proportionally less relative to N, but
 proportionally more compared to P. Our findings indicate that
 grassland-to-woodland transitions amplify landscape-scale S dynamics,
 especially in surface soils, and create a S-enriched environment that
 enables woody plants to acquire sufficient S relative to demand to support
 their continued productivity and proliferation.
description: This dataset was collected
 at the Texas A&M AgriLife La Copita Research Area (27˚40' N,
 98˚12' W) in southern Texas, USA. Briefly, a 160 m × 100 m landscape
 consisting of three major landscape elements (i.e., grasslands, clusters,
 and groves) was established on an upland portion of this site. We further
 subdivided this landscape into 10 m × 10 m grid cells (160 cells in
 total), and georeferenced each corner of each grid cell based on UTM
 coordinates system. In July 2014, we selected two randomly located
 sampling points within each 10 m × 10 m grid cell, yielding a total of 320
 sampling points across this landscape. At each sampling point, we
 collected two adjacent soil cores (2.8 cm in diameter and 5 cm in depth).
  All soil samples were passed through a 2 mm sieve to remove coarse
 organic matter and dried at 65 °C for 48 hrs prior to elemental and
 isotopic analyses.  In addition, to characterize the
 elemental and isotopic composition of vegetation inputs, live leaves and
 fine roots were collected from 16 dominant plant species located within
 the 100 x 160 m study area. Samples were collected from four individual
 plants per species. Furthermore, for each landscape element, we selected
 five locations for collecting litter and fine roots. At each location,
 litter was collected within a 25 cm × 25 cm frame and sorted into twigs
 (i.e., coarse woody debris with a diameter &lt; 1 cm) and leaf litter
 for groves and clusters. After removing the litter layer, one soil core (7
 cm in diameter and 5 cm in depth) was collected from each location and
 washed through a 2 mm sieve to obtain fine roots. All plant and litter
 samples were carefully washed with deionized water and then dried at 65 °C
 for chemical analyses. Oven-dried plant tissues, litter,
 and soil samples were ground to fine powder. All samples were analyzed for
 N concentration using a Costech ECS 4010 elemental analyzer, and for P
 concentrations using the lithium fusion-molybdenum blue method. In
 addition, all samples were combusted to SO2 for determination of total S
 concentrations and δ34S values using a Thermo Scientific EA IsoLink CNSOH
 elemental analyzer interfaced via a ConFlo IV with a Delta V Advantage
 isotope ratio mass spectrometer.
description: The dataset is comprised of
 an excel file with different tabs showing measurements for soil and plant
 samples.