DOI: 10.5061/dryad.gg3c9
title: Data from: Do changes in grazing pressure and the degree of shrub encroachment alter the effects of individual shrubs on understorey plant communities and soil function?

description: 1. Shrub encroachment has dramatically altered the structure and
 functioning of many dryland ecosystems worldwide. While positive effects
 of shrubs on their understorey are commonly found (patch-level effects),
 these effects can be either positive or negative when scaled up to the
 community or landscape level (landscape-level effects). These contrasting
 results are likely to be caused by differences in the degree of shrub
 encroachment or grazing pressure among studies. No study has addressed the
 relationship between the patch-level effects of shrubs and the degree of
 shrub encroachment (i.e., their density or cover) within the landscape,
 and how this relationship is influenced by grazing. 2. We examined how
 differences in grazing pressure and the degree of shrub encroachment, as
 measured by shrub cover, influences patch-level effects of shrubs on
 multiple soil and plant attributes (plant density, biomass and similarity
 between shrub-open areas, and soil stability, nutrient cycling, and
 infiltration) in two semi-arid Australian woodlands. 3. Shrubs had
 consistently positive effects on all plant and soil variables evaluated
 and, contrary to expectation, these positive effects did not decline with
 increasing shrub cover. Rather, these positive patch-level effects became
 larger or remained constant as shrub cover increased, depending on the
 studied variable and site. Heavy grazing negatively affected most of the
 variables studied, and altered the relationship between patch-level
 effects of shrubs and their landscape-level cover in half of the variables
 examined. In these cases, heavy grazing dampened the positive relationship
 between the strength of the positive patch-level effect and shrub cover.
 Synthesis: Shrubs positively affected plant and soil attributes, and this
 positive effect can generally be expected, or even increase, for stands up
 to 50% landscape-level cover. Heavy grazing, however, dampens the positive
 relationship between shrub effects at the patch level and their cover at
 the landscape level. Our results will help to reconcile the contrasting
 results found for the ecological effects of shrub encroachment in the
 literature and further refine our predictions on the effects of woody
 encroachment on ecosystem structure and functioning.
description: shrub encroachment,
 grazing and facilitationThis dataset aimed to
 quantify the interrelationships between grazing, the degree of shrub
 encroachment at the landscape scale and the effect of individual shrubs on
 the vegetation and soils beneath them regarding open areas. Data were
 obtained for 57 50 m x 50 m plots on two different areas (Buronga and
 Scotia) in semiarid New South Wales (Australia. Grazing was quantified by
 sampling within two contrasting land uses: 1) National Parks or protected
 areas, lightly grazed by native herbivores, with no livestock and
 exclusion of kangaroos and feral herbivores, and 2) Grazing properties,
 heavily grazed by livestock (mostly sheep and cattle) with no control of
 kangaroos or feral herbivores. Within these 4 combination of area x
 grazing (Buronga Grazed, Buronga Ungrazed, Scotia Grazed, Scotia Ungrazed)
 we sampled a gradient in shrub encroachment, with 14-15 plots ranging in
 shrub covers from 5 to over 50% (N= 57). Within each plot, we sampled a
 variable number of quadrats (depending on shrub cover) beneath the
 dominant shrubs and in the open. In these quadrats we measured three soil
 function indices (LFA indicators; Tongway 1995, namely infiltration
 (ability to capture water and retain run-off and nutrients), stability
 (resistance to soil erosion) and nutrient cycling. We also measured
 vascular plant richness (species density), cover and biomass. With this
 data, and by using the RII index (Armas et al. 2004, cited in the text),
 we quantified patch-level effects (i.e., the effect of individual shrubs
 in the soils and plants beneath them). From this data we also obtained
 similarity indices between those subcommunities living beneath a nurse and
 those living in the open. More details in the data can be obtained both in
 the metadata and data spreadsheets in the Excel file There is not empty
 data. Data was taken by David Eldridge, Santiago Soliveres and James Val.
 Contact for further information: Dr. Santiago Soliveres (e-mail:
 santiagosoliverescodina@gmail.com)Soliveres & Eldridge_data
 FEcol dryad.xls