DOI: 10.5061/dryad.crjdfn3h3
title: Nurse plant shading is more important than soil fertility for dryland plant recruitment and diversity

description: ”Islands” of plants surrounded by little vegetation cover in drylands are
 thought to arise when larger plants facilitate recruitment via
 “nurse-plant” effects. Simultaneously, plant-soil feedback processes can
 increase soil nutrients beneath shrubs, leading to spatial patterns known
 as “islands of fertility.” These phenomena shape dryland plant
 communities; however, their relative influences on plant density and
 diversity remain poorly quantified. Using reciprocal soil transplants
 among pairs of unvegetated interspaces and neighboring shrubs in
 combination with different cover treatments—open interspace, shaded
 interspace, intact shrub canopy, and trimmed shrub canopy—this study aimed
 to disentangle the influences of shading from soil properties in native
 plant recruitment under the foundational shrub species Larrea tridentata
 and Neltuma glandulosa in the northern Chihuahuan Desert, NM, USA.
 Seedling density varied significantly across the three study years in
 response to interannual climate variability and was consistently higher
 under L. tridentata than N. glandulosa. Cover treatments, soil provenance,
 shrub species, and spatial factors (plot location) significantly affected
 seedling density, species richness, and community structure. Shading from
 shrubs or shade clothes had a stronger effect on density and richness than
 soil provenance or shrub species. Seedling density and richness were also
 higher in soil from beneath shrubs, regardless of shrub species, location
 (native or transplanted locations), or time (study year) since initial
 translocation. The density of seedlings emerging from shaded interspace
 soil was initially similar to that observed under intact shrubs,
 indicating the importance of shading by nurse plants for recruitment.
 However, the effect of shade-cloth canopy surrogates on seedling density
 in interspaces switched from positive to negative by year three of the
 study, likely due to seed bank depletion. The significant influence of
 shading highlights the role of environmental factors in shaping plant
 communities of this dryland system. In contrast, the evidence of seed
 depletion combined with the influence of plot location suggests a
 concurrent influence of stochastic community assembly processes.
 Understanding how these processes interact to shape spatial and temporal
 patterns of vegetation community assembly and potentially reinforce
 alternate ecological states remains an important focus in dryland
 ecosystems.
description: # **Nurse plant shading is more important than soil fertility for dryland
 plant recruitment and diversity** ## **Description of the Data and File
 Structure** This dataset provides plant seedling counts, plant species
 richness, nurse shrub characteristics, and nurse plant neighborhood
 characteristics collected in 2020, 2021, and 2022 during the late summer
 to early autumn monsoon season from 30 study blocks, 15 each where
 creosote bush (Larrea tridenta) or honey mesquite (Neltuma glandulosa)
 were the focal nurse shrubs in southern New Mexico's Chihuhuan
 Desert. Each study block contained 4, 1 m x 1 m study plots that were
 associated with cover treatments that included: intact shrub, trimmed
 shrub (aboveground biomass removed at the ground level), shaded interspace
 (shrub-interspace shaded with 80% woven shade cloth), and open shrub
 interspace (no cover). Each of these 4 plots contained 4, 30 x 30 cm
 sub-plots associated with soil treatments that included: control (no
 disturbance/no seeding), undisturbed-seeded (no disturbance with a seed
 addition), lifted and replaced (a 30 x 30 x 10 cm soil column was cut
 free, lifted, and replaced to its origin), and reciprocally transplanted
 (a 30 x 30 x 10 cm soil column from an alternate setting was transplanted
 into place). Soil transplants were performed to place soil that originated
 under shrubs into interspace plots and vice versa. There are 4 data files
 included: (1) plant seedling counts and (2) plant species richness
 observed in the study sub-plots for each of the three study year with
 treatment category; these files also include information on nurse shrub
 species and identifiers and study plot neighborhood characteristics
 summarized to the first 2 principle components of a PCA included in a long
 format to support linear models in the R computing environment as
 described in the associated publication. The third file (3) contains
 neighborhood characteristics measured for the study plots, and the fourth
 file (4) contains the dimensions used to estimate canopy cover and shrub
 volume for each of the 30 focal, nurse shrubs for analyses. ### **General
 Information** #### **Submitter Details** **Submitter Name:** Ferrenberg,
 Scott **Affiliation:** University of Montana, Missoula, MT, USA, and New
 Mexico State University, Las Cruces, NM, USA **Email:**
 [scott.ferrenberg@mso.umt.edu](mailto:scott.ferrenberg@mso.umt.edu) ####
 **Dates of Data Collection** 2020-2022 #### **Data Spatial Scope** 30
 study blocks, each containing 4 study plots of 1 m x 1 m, from a site in
 southern New Mexico, USA #### **Sharing/Access** This work is licensed
 under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication license. ####
 **Data Sources** The data were obtained through repeated field surveys
 performed by the authors of the associated publication. Necessary permits
 were obtained from the Jornada Basin LTER at New Mexico State University,
 Las Cruces, NM, USA. ### **Description of the File Structure** There are
 two files in .csv format, output from the R environment, and each contains
 a single worksheet if opened in MS Excel. ### **Plant Density and Richness
 Data** Variables in this file (dryad_plant_density_richness_data.csv)
 include plant counts or species counts (species richness) derived from
 repeated surveys of study sub-plots (30 cm x 30 cm squares, 4 of which
 were nested within each 1 m x 1 m study plot). Not all sub-plots were used
 for each variable; in some cases, only 2 of the 4 sub-plots were used.
 Several variables were derived from surveys of study plot
 "neighborhoods," which were defined as 4 m diameter circular
 plots with the 1 m x 1 m study plot center as the origin. This data set
 also includes information about plot and sub-plot treatments, along with
 nurse shrub canopy dimensions and heights to calculate shrub size/volume.
 See Ferrenberg et al. (in press), Nurse plant shading is more important
 than soil fertility for dryland plant recruitment and diversity, *Journal
 of Ecology*, for details. #### **Variable and Data Column Descriptions**
 ##### **year** Calendar year corresponding to the study observations.
 ##### **shrub_species** Species of the nurse shrub, either *Larrea
 tridentata* (LATR) or *Neltuma* (formerly *Prosopis*) *glandulosa* (PRGL).
 ##### **block_number** Study block identification number, values range
 from 1 to 30. ##### **tag_number** Identification tag number used in the
 field setting to aid in plot-pair identification and for record keeping.
 Prior to the assignment of cover treatments, 60 shrub-interspace pairs
 were identified and uniquely tagged (the given tag numbers); tag numbers
 listed in the data are therefore shared by these pairs, leading to 2
 unique tag numbers per study block. ##### **subplot_number** The
 identification number of study sub-plots is used for record keeping and
 quality control during field visits. The sub-plot is the level to which
 soil treatments were applied. There were 4 subplots per study plot; the
 cover treatments were applied at the level of the study plots. #####
 **unique_id** A unique ID string that captures the shrub tag number,
 cover-treatment type, and sub-plot number. This value can be used for data
 quality control and modeling. ##### **cover_treatment** The
 cover-treatment type applied to the plot. There were 4 cover treatment
 levels: control/open interspace (inter), shaded interspace (shade), intact
 shrub (shrub), trimmed shrub (trim). ##### **soil_treatment** The
 soil-treatment type applied to each sub-plot. There were 4 soil treatment
 levels: control/no disturbance or seeding (control), lifted and replaced
 (lift), no disturbance with seeding (seed_only), lifted and reciprocally
 transplanted (swap). ##### **soil_provenance** The *provenance* of soil in
 each sub-plot, either *interspace* (inter) when soil was
 derived/originated in the interspace, or *shrub* (shrub) when soil was
 derived/originated from under a shrub. ##### **germination_total** The
 number of germinating plants/seedlings observed in a 30 cm x 30 cm
 sub-plot. ##### **germination_density** The density of germinating
 plants/seedlings observed in a sub-plot. This value is the
 "germination_total" converted to a density per m^2. #####
 **germinant_species_richness** The species richness (number of unique
 plant species) observed in a 30 cm x 30 cm sub-plot. #####
 **nearest_shrub_neighbor** The distance in centimeters (cm) from the study
 plot to the nearest neighboring shrub. ##### **total_shrub_neighbors** The
 number (count) of shrubs observed within the study plot neighborhood.
 ##### **number_shrub_neighbors_not_L.tridentata** The number (count) of
 shrubs observed within the study plot neighborhood that were not the
 species *Larrea tridentata*. ##### **average_height_shrub_neighbors** The
 average height in centimeters (cm) of all shrubs in the study plot
 neighborhood. ##### **max_height_shrub_neighbors** The maximum height in
 centimeters (cm) of the tallest shrub in the study plot neighborhood.
 ##### **average_shrub_height_to_count_ratio** The ratio of average shrub
 height (cm) to the number of shrubs in the study plot neighborhood--i.e.,
 "average_height_shrub_neighbors"/"total_shrub_neighbors." ##### **coefficient_variation_shrub_neighbor_heights** The coefficient of variation (CV) calculated from all shrub heights in the study plot neighborhood. ##### **height_shrub_1, height_shrub_2, height_shrub_3,...height_shrub_13** The 13 columns with "height_shrub_[number]" all correspond to the height, in centimeters (cm), of the tallest point on the canopy of shrubs found within the neighborhood defined around study plots. Each column corresponds to an individual shrub within the neighborhood. There are an equivalent number of column entries per row as the value found under "total_shrub_neighbors," i.e., each shrub in a study plot neighborhood is represented by one height value. ##### **neighborhood_principle_component_1** The value of PC 1 extracted from a PCA, using the "princomp" function in R, that was applied to reduce the shrub neighborhood data for use in linear models. ##### **neighborhood_principle_component_2** The value of PC 2 extracted from a PCA, using the "princomp" function in R, that was applied to reduce the shrub neighborhood data for use in linear models. ##### **nurse_shrub_height** The height to the tallest point of the nurse shrub canopy in meters (m). ##### **nurse_shrub_canopy_length** The longest axis of the nurse shrub canopy, measured parallel to the ground surface, in meters (m). ##### **nurse_shrub_canopy_width** The longest perpendicular axis to the "nurse_shrub_canopy_length" axis in the nurse shrub canopy, measured parallel to the ground surface, in meters (m). ### **Plant Community Data** This data set (dryad_community_matrix_data.csv) includes plot and sub-plot treatment information along with a community matrix of total counts of each plant species observed from repeated surveys of study sub-plots (30 cm x 30 cm squares, 4 of which were nested within each 1 m x 1 m study plot). See Ferrenberg et al. (in press), Nurse plant shading is more important than soil fertility for dryland plant recruitment and diversity, *Journal of Ecology* for details. #### **Variable and Data Column Descriptions** ##### **year** Calendar year corresponding to the study observations. ##### **shrub_species** Species of the nurse shrub, either *Larrea tridentata* (LATR) or *Neltuma* (formerly *Prosopis*) *glandulosa* (PRGL). ##### **block_number** Study block identification number, values range from 1 to 30. ##### **unique_id** A unique ID string that captures the shrub tag number, cover-treatment type, and sub-plot number. This value can be used for data quality control and modeling. ##### **cover_treatment** The cover-treatment type applied to the plot. There were 4 cover treatment levels: control/open interspace (inter), shaded interspace (shade), intact shrub (shrub), trimmed shrub (trim). ##### **soil_treatment** The soil-treatment type applied to each sub-plot. There were 4 soil treatment levels: control/no disturbance or seeding (control), lifted and replaced (lift), no disturbance with seeding (seed_only), lifted and reciprocally transplanted (swap). ##### **soil_provenance** The *provenance* of soil in each sub-plot, either *interspace* (inter) when soil was derived/originated in the interspace, or *shrub* (shrub) when soil was derived/originated from under a shrub. ##### **ACONAN, AMAFIM, AMAPAL, ... Unknown_plant** These columns are counts of the number of individuals of each species identified by 6-letter plant codes in each column header, or as "unknown" type when unable to be identified to genus/species. The columns correspond to the following species, presented in alphabetical order: | Species | 6 Letter Code | Functional Type | | -------------------------- | -------------- | ----------------------- | | *Acourtia nana* | ACONAN | Perennial forb | | *Aloysia wrightii* | ALOWRI | Perennial shrub | | *Amaranthus fimbriatus* | AMAFIM | Annual forb | | *Amaranthus palmeri* | AMAPAL | Annual forb | | *Bahia absinthifolia* | BAHABS | Perennial forb | | *Baileya multiradiata* | BAIMUL | Perennial forb | | *Bouteloua aristidoides* | BOUARI | Annual grass | | *Bouteloua barbata* | BOUBAR | Perennial grass | | *Chamaesyce micromera* | CHAMIC | Annual forb | | *Chamaesyce serpens* | CHASERP | Annual/Perennial forb | | *Chamaesyce serrula* | CHASERR | Annual forb | | *Chamaesyce spp.* | CHASPP | Annual forb | | *Cylindropuntia imbricata* | CYLIMB | Perennial succulent | | *Dasyochloa pulchella* | DASPUL | Perennial forb | | *Descurainia pinnata* | DESPIN | Annual forb | | *Digitaria californica* | DIGCAL | Perennial grass | | *Draba cuneifolia* | DRACUN | Annual forb | | *Eriogonum abertianum* | ERIABE | Annual forb | | *Kallstroemia parviflora* | KALPAR | Annual forb | | *Larrea tridentata* | LARTRI | Perennial shrub | | *Leptochloa viscida* | LEPVIS | Annual grass | | *Mollugo cerviana* | MOLCER | Annual forb | | *Muhlenbergia porteri* | MUHPOR | Perennial grass | | *Nama hispidum* | NAMHIS | Annual forb | | *Nemacladus glanduliferus* | NEMGLA | Annual forb | | *Parthenium incanum* | PARINC | Perennial shrub | | *Pectis papposa* | PECPAP | Annual forb | | *Portulaca halimoides* | PORHAL | Annual forb | | Unknown grass | unknown\_grass | Unknown grass | | Unknown forb | unknown\_forb | Unknown forb | | Unknown plant | unknown\_plant | Unknown plant spp./type | | *Verbesina encelioides* | VERENC | Annual forb | | *Yucca elata* | YUCELA | Perennial succulent | | *Zinnia acerosa* | ZINACE | Perennial forb |