DOI: 10.5061/dryad.0gb5mkmdq
title: Data from: Structural diversity shifts from negative to positive associations with forest productivity via basal area, stand age, and precipitation thresholds

description: Understanding the relationship between biological diversity and ecosystem
 productivity is a central challenge in ecology. Structural diversity—the
 variation in size, height, and spatial arrangement of individuals within
 communities—has been proposed as a key driver of productivity, yet
 previous studies have reported mixed results, leaving its role in
 ecosystem functioning unclear. Clarifying the structural diversity and
 productivity relationship (SDPR) is essential not only for advancing
 ecological theory but also for informing biodiversity conservation,
 resource management, and climate adaptation strategies across ecosystems.
 Here, we utilized the USDA Forest Service Forest Inventory and Analysis
 (FIA) database, encompassing 95,602 trees within 3,307 plots throughout
 most types of forest ecosystems in the contiguous U.S. We investigated the
 variation of SDPR by analyzing the growth of existing trees under the main
 and interactive effects of structural diversity with basal area, stand
 age, and annual precipitation, with other factors. We also compiled the
 studies of SDPR published during 1974 - 2022 and compared the mean annual
 precipitation between studies showing the negative and positive SDPR. We
 found that: 1) SDPR was negative under the low range of structural
 diversity, but became positive under the high range; 2) SDPR was more
 positive with greater basal areas; 3) SDPR was more positive with stand
 development, and 4) SDPR was more positive with greater annual
 precipitation in the range of low structural diversity but switched to be
 more negative in the high range, and the negative SDPR with greater
 precipitation aligns with the analysis of published studies showing
 greater precipitation in studies with negative SDPR than the positive
 ones.
description: # Data from: Structural diversity shifts from negative to positive
 associations with forest productivity via basal area, stand age, and
 precipitation thresholds Dataset DOI:
 [10.5061/dryad.0gb5mkmdq](10.5061/dryad.0gb5mkmdq) ## Description of the
 data and file structure We have five datasets for the analysis.
 **FIA_Shade_Tolerance.xlsx**, a shade-tolerance metrics, ranging from 1-5
 for the species in FIA data. **tbl.fig.RData,** RData for figures.
 **tbl.growth.Norm.DmgTree.Rdata,** Plot-level data w/o standardized
 variables. **tbl.site.growth.site.dmgTree.Rdata,** Plot-level data w/
 standardized variables. **tbl.tree.MrgSbPlt.Rdata,** tree-level data after
 data curation in raw FIA data. Note that this tree-level data were
 aggregated to create plot-level data. 
 
 **Descriptions** **Code_JE.R:** Code that includes GAM developments and
 figures. **FIA_Shade_Tolerance.xlsx** * SpcsNm: Species Name (scientific
 names) * Shade tolerance: degree of the shade-tolerance, ranging from 1
 (shade intolerant) to 5 (shade tolerant) **tbl.fig.RData:** This just
 rData that includes the components to draw the figures.
 **tbl.growth.Norm.DmgTree.Rdata (Note that the value was standardized, so
 it's unitless)** * PlotID: PlotID * LAT: Latitude * LON: Longitude *
 StartDate: Measurement Starting date * EndDate: Measurement Ending date *
 Bomsclass: Biomass class: Ingrowth; Growth; and Mortality * ASPECT.factor:
 aspect (East, West, South, and North) * Aspect.East: indicator variables
 if Aspect is East = 1; otherwise = 0 * Aspect.West: indicator variables if
 Aspect is West= 1; otherwise = 0 * Aspect.South: indicator variables if
 Aspect is South = 1; otherwise = 0 * Aspect.North: indicator variables if
 Aspect is North = 1; otherwise = 0 * BIO1: Annual Mean Temperature defined
 in WorldClim:  * BIO2: Mean Diurnal Range (Mean of monthly (max temp - min
 temp)) * BIO3 = Isothermality (BIO2/BIO7) (×100) * BIO4 = Temperature
 Seasonality (standard deviation ×100) * BIO5 = Max Temperature of Warmest
 Month * BIO6 = Min Temperature of Coldest Month BIO7 = Temperature Annual
 Range (BIO5-BIO6) BIO8 = Mean Temperature of Wettest Quarter BIO9 = Mean
 Temperature of Driest Quarter BIO10 = Mean Temperature of Warmest Quarter
 BIO11 = Mean Temperature of Coldest Quarter BIO12 = Annual Precipitation
 BIO13 = Precipitation of Wettest Month BIO14 = Precipitation of Driest
 Month BIO15 = Precipitation Seasonality (Coefficient of Variation) BIO16 =
 Precipitation of Wettest Quarter BIO17 = Precipitation of Driest Quarter
 BIO18 = Precipitation of Warmest Quarter BIO19 = Precipitation of Coldest
 Quarter * AWS: Available water storage * CEC: Cation Exchange Capacity *
 OM: Organic matter  * PC: Percentage of clay * PS: Percentage of sand *
 DTW: Depth to water * ELEV: Elevation * Slope: slope * STDAGE: Stand age *
 ASPECT: aspect * COSASP: Cosine of aspect * SSD: Structural diversity *
 FD: Functional diversity * SLA: Specific leaf area * LfCN: Leaf C:N ratio
 * WD: Wood density * HT90: 90th percentile tree height * NumFixer: Number
 of N-fixed tree number in a plot * PcntNFixer: Percentage of N-fixed tree
 number * BAperha: Basal area per ha * SSDperha: SSDperha * SRperha:
 species richness per ha * PcntRtDmgTree: percentage of root-damaged trees
 * NumDmgTreeperha: Number of damaged trees per ha * PcntDmgperha:
 Percentage of damaged trees * Boms.YrRtperha: Biomass growth rate per ha
 **tbl.growth.Norm.DmgTree.Rdata,** * PlotID: PlotID * LAT: Latitude * LON:
 Longitude * Biomass: summation of the biomss of individuals  * TreeNum:
 Number of trees in a plot * Boms.YrRt: growth of the biomass (plot-level)
 * StartDate: Measurement Starting date * EndDate: Measurement Ending date
 * Bomsclass: Biomass class: Ingrowth; Growth; and Mortality *
 ASPECT.factor: aspect (East, West, South, and North) * Aspect.East:
 indicator variables if Aspect is East = 1; otherwise = 0 * Aspect.West:
 indicator variables if Aspect is West= 1; otherwise = 0 * Aspect.South:
 indicator variables if Aspect is South = 1; otherwise = 0 * Aspect.North:
 indicator variables if Aspect is North = 1; otherwise = 0 * BIO1: Annual
 Mean Temperature defined in WorldClim:  * BIO2: Mean Diurnal Range (Mean
 of monthly (max temp - min temp)) * BIO3 = Isothermality (BIO2/BIO7)
 (×100) * BIO4 = Temperature Seasonality (standard deviation ×100) * BIO5 =
 Max Temperature of Warmest Month * BIO6 = Min Temperature of Coldest Month
 BIO7 = Temperature Annual Range (BIO5-BIO6) BIO8 = Mean Temperature of
 Wettest Quarter BIO9 = Mean Temperature of Driest Quarter BIO10 = Mean
 Temperature of Warmest Quarter BIO11 = Mean Temperature of Coldest Quarter
 BIO12 = Annual Precipitation BIO13 = Precipitation of Wettest Month BIO14
 = Precipitation of Driest Month BIO15 = Precipitation Seasonality
 (Coefficient of Variation) BIO16 = Precipitation of Wettest Quarter BIO17
 = Precipitation of Driest Quarter BIO18 = Precipitation of Warmest Quarter
 BIO19 = Precipitation of Coldest Quarter * AWS: Available water storage *
 CEC: Cation Exchange Capacity * OM: Organic matter  * PC: Percentage of
 clay * PS: Percentage of sand * DTW: Depth to water * ELEV: Elevation *
 Slope: slope * STDAGE: Stand age * ASPECT: aspect * COSASP: Cosine of
 aspect * SSD: Structural diversity * FD: Functional diversity * SLA:
 Specific leaf area * LfCN: Leaf C:N ratio * WD: Wood density * HT90: 90th
 percentile tree height * NumFixer: Number of N-fixed tree number in a plot
 * PcntNFixer: Percentage of N-fixed tree number * BAperha: Basal area per
 ha * SSDperha: SSDperha * SRperha: species richness per ha *
 PcntRtDmgTree: percentage of root-damaged trees * NumDmgTreeperha: Number
 of damaged trees per ha * PcntDmgperha: Percentage of damaged trees *
 Boms.YrRtperha: Biomass growth rate per ha **tbl.tree.MrgSbPlt.Rdata** *
 PlotID: PlotID * StartDate: Measurement Starting date * EndDate:
 Measurement Ending date * SubPlotID: SubplotiD * TreeID: TreeID * SPCD:
 Species code * Status.StartYr. Tree status status in startYr  *
 Status.EndYr. Tree status status in EndYr * DeathCause: cause of deat
 agent of the trees * DIA.StartYr: diameter at breast height in start year
 * DIA.EndYr: diameter at breast height in end year * HT.StartYr: Height in
 start year  * HT.EndYr: Height in end year * Boms.StartYr: Biomass of
 trees in start year * Boms.EndYr: Biomass of trees in end year *
 CrownR.StartYr: Crown ratio in start year * CrownR.EndYr: Crown ratio in
 end year * CrownC.StartYr: Crown class code in start year * CrownC.EndYr:
 Crown class code in end year * BomsClass: biomass class: ingrowth; growth;
 and mortality * DAMLOC1.StartYr: Damage location in start year *
 DAMSEV1.StartYr: Damage severity in start year * DAMTYPE1.StartYr: Damage
 types in start year * DAMLOC2.StartYr: secondary damage location in start
 year * DAMSEV2.StartYr: secondary damage severity in start year *
 DAMTYPE2.StartYr: secondary damage types in start year * DAMLOC3.StartYr:
 Third damage location in start year * DAMSEV3.StartYr: Third damage
 severity in start year * DAMTYPE3.StartYr: Third damage types in start
 year * DAMLOC1.EndYr: Damage location in end year * DAMSEV1.EndYr: Damage
 severity in end year * DAMTYPE1.EndYr: Damage types in end year *
 DAMLOC2.EndYr: secondary damage location in end year * DAMSEV2.EndYr:
 secondary damage severity in end year * DAMTYPE2.EndYr: secondary damage
 types in end year * DAMLOC3.EndYr: Third damage location in end year *
 DAMSEV3.EndYr: Third damage severity in end year * DAMTYPE3.EndYr: Third
 damage types in end year * MORTYR: Mortality Year * SubPlotID.StartYr:
 Combination of SubplotID and StartYr * NumSrvys.x: Number of survey of the
 plot (not really need for the analysis) * NumSrvys.y: Number of survey of
 the plot (not really need for the analysis) * SpcsNm: species scientific
 names * Is39Spcs: Yes or no for the 39 species in the dataset * NumSbplts:
 Number of subplots in a plot * YrDiff: Year difference between startdate
 and enddate * SHADETOLERANCE: Shade tolerance levels **All the NA values
 are not measured data.**