DOI: 10.5061/dryad.c5t6v
title: Data from: Neighborhood-scale analyses of non-additive species effects on cation concentrations in forest soils

description: Trees affect soil chemistry and nutrient availability via a broad range of
 processes. Effects can vary dramatically among species, whose distinctive
 spatial “footprints” can vary for different nutrients. Potentially
 overlapping effects of neighboring trees in mixed-species stands make
 footprint shape and interspecific interactions important: If interactions
 are non-additive, then not only abundance but also spatial configuration
 influence tree species’ effects on ecosystem properties. We used spatially
 explicit neighborhood-scale data on tree distributions to fit maximum
 likelihood models of exchangeable calcium, magnesium, and potassium in
 surface soils of four sites in northern hardwood forests in northwestern
 Connecticut, USA. The models incorporated parent material, site, and tree
 species or functional group configuration to predict availability of the
 three cations. Site had a stronger effect than species for all cations
 (there was no species effect for potassium), even after accounting for
 variation in parent material. Species’ spatial footprints extended further
 from the stem for calcium than magnesium, which is consistent with the
 relative importance of litterfall versus stemflow transfer of these
 nutrients. The magnitude of species effects on calcium and magnesium
 varied widely. Functional groups made up of species with positive or
 negative effects provided parsimonious models for magnesium and calcium,
 and the best model for calcium included a non-additive, antagonistic
 effect whose strength varied by site. This non-additive effect suggests
 that the degree of intermingling of tree species from negative- and
 positive-effect functional groups may influence stand-level availability
 of calcium, a key nutrient for forest health in these ecosystems.
description: Soil Sample Data with 4
 Site CodesSoil Sample Data
 documentation. 137 records, each representing a point at which soil
 samples were obtained. Variables are "SITECODE",
 "SITENUM", "TDIST" (m), "X" (m),
 "Y" (m), "EL.CA.MOL" (mol/m2), "EL.MG.MOL"
 (mol/m2), "EL.K.MOL" (mol/m2), "EX.CA.MOL" (mol/m2),
 "EX.MG.MOL" (mol/m2), "EX.K.MOL" (mol/m2)
 "SITECODE", values 1-4, is code indicating area of landscape
 where samples were taken. In the accompanying manuscript, corresponding
 locations and codes are 1=Camps Pond (A), 2=Wangum (D), 3 = #4 Trail (B),
 4 = Backgate (C). "SITENUM", values 1-104 (not inclusive).
 SITENUM 1-18 and 52-95 are at Camps Pond. SITENUM 19-30 are at Wangum,
 SITENUM 31-36 are at #4 Trail. SITENUM 101 is at Backgate, and SITENUM 104
 is at #4 Trail. "TDIST" indicates distance along transect, in
 meters. SITENUM 101 consists of two parallel transects: the first transect
 has distances from 0-100, and second, from 200-300 (i.e., the different
 transect is indicated by adding 200 to each distance along it). SITENUM
 104 consists of a single 200 m transect with soil sample sites at 5 m
 intervals. Every record is defined by a unique combination of
 "SITENUM" and "TDIST". "X" and "Y"
 are xy coordinates (in m) where soil sample was taken. There is a unique
 XY coordinate reference system at each value of "SITENUM".
 "EL.CA.MOL" (mol/m2), "EL.MG.MOL" (mol/m2),
 "EL.K.MOL" (mol/m2), "EX.CA.MOL" (mol/m2),
 "EX.MG.MOL" (mol/m2), "EX.K.MOL" (mol/m2) are values
 of exchangeable calcium, magnesium and potassium.Tree Map Data Checked
 2015The file "Tree Map
 Data Checked 2015.txt" provides tree map data for plots where soil
 samples were taken. Variables are "SITENUM", "X" (m),
 "Y" (m), "Z" (m), "DBH" (cm), and
 "SPECIES". It has original site numbers (not grouped into 4
 sites, and not numbered consecutively). 1:18 - Camps Pond 19:30 - Wangum
 31:36 - #4 Trail 51-98: Sites originally sampled by Feike Dijkstra, n=18,
 all at Camps Pond 104: Transect #1 at #4 Trail 101: “Back Gate” transects
 #1 and #2 X, Y, and Z are local tree-location coordinates. Each SITENUM
 has a common coordinate reference system. DBH is tree's breast-height
 diameter. SPECIES is a four-letter acronym that is a concatentation of the
 first two letters of the genus and species. Acronyms and associated
 species are given below "species","binomial"
 "acpe","Acer pennsylvanica"
 "acru","Acer rubrum" "acsa","Acer
 saccharum" "beal","Betula alleghaniensis"
 "bepa","Betula papyrifera"
 "bepo","Betula populifolia"
 "crb","Crataegus brainerdii"
 "caca","Carpinus caroliniana"
 "caov","Carya ovata" "fram","Fraxinus
 americana" "fagr","Fagus grandifolia"
 "havi","Hammamelis virginiana"
 "masy","Malus sylvestris"
 "osvi","Ostrya virginiana"
 "pran","Prunus angustifolia"
 "pprr","Picea rubens "prse","Prunus
 serotina" "pist","Pinus strobus"
 "qual","Quercus alba" "quru","Quercus
 rubra" "tsca","Tsuga
 canadensis"