William Stock

Ecological Engineering by a Mega-Grazer: White Rhino Impacts on a South African Savanna

Publisher: Springer Science and Business Media LLC

Date: 30-11-2007

DOI: 10.1007/S10021-007-9109-9

Global patterns of foliar nitrogen isotopes and their relationships with climate, mycorrhizal fungi, foliar nutrient concentrations, and nitrogen availability

Publisher: Wiley

Date: 10-08-2009

DOI: 10.1111/J.1469-8137.2009.02917.X

Abstract: Ratios of nitrogen (N) isotopes in leaves could elucidate underlying patterns of N cycling across ecological gradients. To better understand global‐scale patterns of N cycling, we compiled data on foliar N isotope ratios (δ 15 N), foliar N concentrations, mycorrhizal type and climate for over 11 000 plants worldwide. Arbuscular mycorrhizal, ectomycorrhizal, and ericoid mycorrhizal plants were depleted in foliar δ 15 N by 2‰, 3.2‰, 5.9‰, respectively, relative to nonmycorrhizal plants. Foliar δ 15 N increased with decreasing mean annual precipitation and with increasing mean annual temperature (MAT) across sites with MAT ≥ −0.5°C, but was invariant with MAT across sites with MAT −0.5°C. In independent landscape‐level to regional‐level studies, foliar δ 15 N increased with increasing N availability at the global scale, foliar δ 15 N increased with increasing foliar N concentrations and decreasing foliar phosphorus (P) concentrations. Together, these results suggest that warm, dry ecosystems have the highest N availability, while plants with high N concentrations, on average, occupy sites with higher N availability than plants with low N concentrations. Global‐scale comparisons of other components of the N cycle are still required for better mechanistic understanding of the determinants of variation in foliar δ 15 N and ultimately global patterns in N cycling.

Genetic and ecological consequences of recent habitat fragmentation in a narrow endemic plant species within an urban context

Publisher: Springer Science and Business Media LLC

Date: 27-07-2021

DOI: 10.1007/S10531-021-02256-X

Abstract: Understanding the timescales that shape spatial genetic structure is pivotal to ascertain the impact of habitat fragmentation on the genetic ersity and reproductive viability of long-lived plant populations. Combining genetic and ecological information with current and past fragmentation conditions allows the identification of the main drivers important in shaping population structure and declines in reproduction, which is crucial for informing conservation strategies. Using historic aerial photographs, we defined the past fragmentation conditions for the shrub Conospermum undulatum , a species now completely embedded in an urban area. We explored the impact of current and past conditions on its genetic layout and assessed the effects of genetic and environmental factors on its reproduction. The historically high structural connectivity was evident in the genetics of the species. Despite the current intense fragmentation, we found similar levels of genetic ersity across populations and a weak spatial genetic structure. Historical connectivity was negatively associated with genetic differentiation among populations and positively related to within-population genetic ersity. Variation partitioning of reproductive performance explained ~ 66% of the variance, showing significant influences for genetic (9%), environmental (15%), and combined (42%) fractions. Our study highlights the importance of considering the historical habitat dynamics when investigating fragmentation consequences in long-lived plants. A detailed characterization of fragmentation from 1953 has shown how low levels of genetic fixation are due to extensive gene flow through the non-fragmented landscape. Moreover, knowledge of the relationships between genetic and environmental variation and reproduction can help to implement effective conservation strategies, particularly in highly dynamic landscapes.

AN EVALUATION OF SOME MANUAL COLORIMETRIC METHODS FOR THE DETERMINATION OF INORGANIC NITROGEN IN SOIL EXTRACTS

Publisher: Informa UK Limited

Date: 08-1983

DOI: 10.1080/00103628309367420

Natural abundance of δ 15N confirms insectivorous habit of Roridula gorgonias, despite it having no proteolytic enzymes

Publisher: Oxford University Press (OUP)

Date: 09-1998

DOI: 10.1006/ANBO.1998.0684

Atmospheric nitrogen deposition in world biodiversity hotspots: the need for a greater global perspective in assessing N deposition impacts

Publisher: Wiley

Date: 03-2006

DOI: 10.1111/J.1365-2486.2006.01104.X

Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa

Publisher: Elsevier BV

Date: 03-2009

DOI: 10.1016/J.ENVPOL.2008.10.021

Abstract: Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field s les were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32-1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar delta(15)N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6-13 kgNha(-1)a(-1) since 1950. Enhanced N deposition rates of this magnitude could lead to bio ersity losses in native ecosystems.

Time since fire influences food resources for an endangered species, Carnaby's cockatoo, in a fire-prone landscape

Publisher: Elsevier BV

Date: 07-2014

DOI: 10.1016/J.BIOCON.2014.04.006

Reply to migration is not the perfect answer: Optimized methodology to assess LCI agreement between corrected legacy multiple breath nitrogen washout data and that directly collected on updated software

Publisher: Wiley

Date: 03-05-2023

DOI: 10.1002/PPUL.26430

SOIL-NITROGEN AND THE ROLE OF FIRE AS A MINERALIZING AGENT IN A SOUTH-AFRICAN COASTAL FYNBOS ECOSYSTEM

Publisher: JSTOR

Date: 06-1986

DOI: 10.2307/2260257

Long-term effects of elevated atmospheric CO2 on species composition and productivity of a southern African C4 dominated grassland in the vicinity of a CO2 exhalation

Publisher: Springer Science and Business Media LLC

Date: 06-2005

DOI: 10.1007/S11258-004-3654-5

Correction to: Genetic and ecological consequences of recent habitat fragmentation in a narrow endemic plant species within an urban context

Publisher: Springer Science and Business Media LLC

Date: 13-09-2021

DOI: 10.1007/S10531-021-02285-6

Genome-wide scans detect adaptation to aridity in a widespread forest tree species

Publisher: Wiley

Date: 05-2014

DOI: 10.1111/MEC.12751

Abstract: Patterns of adaptive variation within plant species are best studied through common garden experiments, but these are costly and time-consuming, especially for trees that have long generation times. We explored whether genome-wide scanning technology combined with outlier marker detection could be used to detect adaptation to climate and provide an alternative to common garden experiments. As a case study, we s led nine provenances of the widespread forest tree species, Eucalyptus tricarpa, across an aridity gradient in southeastern Australia. Using a Bayesian analysis, we identified a suite of 94 putatively adaptive (outlying) sequence-tagged markers across the genome. Population-level allele frequencies of these outlier markers were strongly correlated with temperature and moisture availability at the site of origin, and with population differences in functional traits measured in two common gardens. Using the output from a canonical analysis of principal coordinates, we devised a metric that provides a holistic measure of genomic adaptation to aridity that could be used to guide assisted migration or genetic augmentation.

Seasonal allocation of dry mass and nitrogen in a fynbos endemic Restionaceae species Thamnochortus punctatus Pill.

Publisher: Springer Science and Business Media LLC

Date: 05-1987

DOI: 10.1007/BF00379284

Dynamics of phreatophyte root growth relative to a seasonally fluctuating water table in a Mediterranean-type environment

Publisher: Springer Science and Business Media LLC

Date: 13-06-2012

DOI: 10.1007/S00442-012-2381-1

Abstract: While seasonal redistribution of fine root biomass in response to fluctuations in groundwater level is often inferred in phreatophytic plants, few studies have observed the in situ growth dynamics of deep roots relative to those near the surface. We investigated the root growth dynamics of two Banksia species accessing a seasonally dynamic water table and hypothesized that root growth phenology varied with depth, i.e. root growth closest to the water table would be influenced by water table dynamics rather than surface micro-climate. Root in-growth bags were used to observe the dynamics of root growth at different soil depths and above-ground growth was also assessed to identify whole-plant growth phenology. Root growth at shallow depths was found to be in synchrony with above-ground growth phenophases, following increases in ambient temperature and soil water content. In contrast, root growth at depth was either constant or suppressed by saturation. Root growth above the water table and within the capillary fringe occurred in all seasons, corresponding with consistent water availability and aerobic conditions. However, at the water table, a seasonal cycle of root elongation with drawdown in summer followed by trimming in response to water table rise and saturation in winter, was observed. The ability to grow roots year-round at the capillary fringe and redistribute fine root biomass in response to groundwater drawdown is considered critical in allowing phreatophytes, in seasonally water-limited environments, to maintain access to groundwater throughout the year.

Plasticity of functional traits varies clinally along a rainfall gradient in Eucalyptus tricarpa

Publisher: Wiley

Date: 13-01-2014

DOI: 10.1111/PCE.12251

Abstract: Widespread species often occur across a range of climatic conditions, through a combination of local genetic adaptations and phenotypic plasticity. Species with greater phenotypic plasticity are likely to be better positioned to cope with rapid anthropogenic climate changes, while those displaying strong local adaptations might benefit from translocations to assist the movement of adaptive genes as the climate changes. Eucalyptus tricarpa occurs across a climatic gradient in south-eastern Australia, a region of increasing aridity, and we hypothesized that this species would display local adaptation to climate. We measured morphological and physiological traits reflecting climate responses in nine provenances from sites of 460 to 1040 mm annual rainfall, in their natural habitat and in common gardens near each end of the gradient. Local adaptation was evident in functional traits and differential growth rates in the common gardens. Some traits displayed complex combinations of plasticity and genetic ergence among provenances, including clinal variation in plasticity itself. Provenances from drier locations were more plastic in leaf thickness, whereas leaf size was more plastic in provenances from higher rainfall locations. Leaf density and stomatal physiology (as indicated by δ(13)C and δ(18)O) were highly and uniformly plastic. In addition to variation in mean trait values, genetic variation in trait plasticity may play a role in climate adaptation.

Pine as Fast Food: Foraging Ecology of an Endangered Cockatoo in a Forestry Landscape

Publisher: Public Library of Science (PLoS)

Date: 11-04-2013

DOI: 10.1371/JOURNAL.PONE.0061145

ATMOSPHERIC DEPOSITION OF PHOSPHORUS IN A COASTAL FYNBOS ECOSYSTEM OF THE SOUTHWESTERN CAPE, SOUTH-AFRICA

Publisher: JSTOR

Date: 07-1984

DOI: 10.2307/2260065

How savanna grasses decompose?

Publisher: Elsevier BV

Date: 04-2007

DOI: 10.1016/J.SAJB.2007.02.084

Interactive effects of altered rainfall and simulated nitrogen deposition on seedling establishment in a global biodiversity hotspot

Publisher: Wiley

Date: 10-04-2012

DOI: 10.1111/J.1600-0706.2012.20553.X

Floral display and habitat fragmentation: Effects on the reproductive success of the threatened mass‐flowering Conospermum undulatum (Proteaceae)

Publisher: Wiley

Date: 26-09-2019

DOI: 10.1002/ECE3.5653

Dendroecological indicators of historical responses of pines to water and nutrient availability on a superficial aquifer in south-western Australia

Publisher: Elsevier BV

Date: 2012

DOI: 10.1016/J.FORECO.2011.09.033

Forces that structure plant communities: quantifying the importance of the mycorrhizal symbiosis

Publisher: Wiley

Date: 08-11-2010

DOI: 10.1111/J.1469-8137.2010.03550.X

Phytochemical changes in leaves of subtropical grasses and fynbos shrubs at elevated atmospheric CO2 concentrations

Publisher: Elsevier BV

Date: 07-2005

DOI: 10.1016/J.GLOPLACHA.2004.10.010

INFLUENCE OF SEED SIZE AND QUALITY ON SEEDLING DEVELOPMENT UNDER LOW NUTRIENT CONDITIONS IN 5 AUSTRALIAN AND SOUTH-AFRICAN MEMBERS OF THE PROTEACEAE

Publisher: JSTOR

Date: 12-1990

DOI: 10.2307/2260949

Do grazers alter nitrogen dynamics on grazing lawns in a South African savannah?

Publisher: Wiley

Date: 14-09-2010

DOI: 10.1111/J.1365-2028.2010.01236.X

RESOURCE CONTROL OF SEED SET IN BANKSIA-LARICINA C GARDNER (PROTEACEAE)

Publisher: JSTOR

Date: 1989

DOI: 10.2307/2389619

Emissions of gaseous pollutants from laboratory-based fires of vegetation from five common vegetation types in Western Australia

Publisher: Elsevier BV

Date: 06-2020

DOI: 10.1016/J.APR.2020.03.015

SEED DEVELOPMENTAL PATTERNS IN BANKSIA-ATTENUATA R BR AND B-LARICINA C GARDNER IN RELATION TO MECHANICAL DEFENSE COSTS

Publisher: Wiley

Date: 1991

DOI: 10.1111/J.1469-8137.1991.TB00950.X

Functional Group Identity Does not Predict Invader Impacts: Differential Effects of Nitrogen-fixing Exotic Plants on Ecosystem Function

Publisher: Springer Science and Business Media LLC

Date: 11-04-2006

DOI: 10.1007/S10530-006-0008-3

Isolation, characterization, and cross‐amplification of 20 microsatellite markers for Conospermum undulatum (Proteaceae)

Publisher: Wiley

Date: 08-2019

DOI: 10.1002/APS3.11283

Water stress vulnerability of four Banksia species in contrasting ecohydrological habitats on the Gnangara Mound, Western Australia

Publisher: Wiley

Date: 03-12-2009

DOI: 10.1111/J.1365-3040.2008.01904.X

Abstract: This study investigated the interspecific differences in vulnerability to xylem embolism of four phreatophytes - two facultative phreatophytes (Banksia attenuata and B. menziesii) and two obligate phreatophytes (B. ilicifolia and B. littoralis). Species differences at the same position along an ecohydrological gradient on the Gnangara Groundwater Mound, Western Australia were determined in addition to intraspecific differences to water stress between populations in contrasting ecohydrological habitats. Stem- and leaf-specific hydraulic conductivity, as well as Huber values (ratio of stem to leaf area), were also determined to support these findings. We found that where water is readily accessible, there were no interspecific differences in vulnerability to water stress. In contrast both facultative phreatophyte species were more resistant to xylem embolism at the more xeric dune crest site than at the wetter bottom slope site. B. ilicifolia did not differ in vulnerability to embolism, supporting its classification as an obligate phreatophyte. Other measured hydraulic traits (K(S), K(L) and Huber value) showed no adaptive responses, although there was a tendency for plants at the wetter site to have higher K(S) and K(L). This study highlights the influence site hydrological attributes can have on plant hydraulic architecture across species and environmental gradients.

Effects of water availability, nitrogen supply and atmospheric CO2 concentrations on plant nitrogen natural abundance values

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/FP05188

Abstract: The relative effects of soil N, water supply and elevated atmospheric CO2 on foliar δ15N values were examined. Phalaris arundinacea L. (Holdfast) and Physalis peruviana L. (Cape Gooseberry) were grown for 80 d with three water availability treatments, two atmospheric CO2 concentrations and four N supply rates. Elevated CO2 increased total plant biomass and N for each treatment and decreased allocation to roots, leaf N concentrations and stomatal conductance. Leaves had less negative leaf δ13C values under low water supply associated with decreased stomatal conductance and increased leaf N concentration, which decreased the ratio of intercellular to ambient CO2 concentration. The δ15N value of the supplied nitrate (4.15‰) was similar to the value for Phalaris leaves (4.11‰), but Cape Gooseberry leaves were enriched (6.52‰). The effects of elevated CO2 on leaf δ15N values were small, with Phalaris showing no significant change, while Cape Gooseberry showed a significant (P 0.05) decline of 0.42 ‰. Variation in δ15N values was unrelated to stomatal conductance, transpiration, differential use of N forms or denitrification. Plants with low foliar N concentrations tended to be depleted in 15N. We suggest that changes in N allocation alter foliar δ15N values under different CO2 and water treatments.

Rapid root elongation by phreatophyte seedlings does not imply tolerance of water table decline

Publisher: Springer Science and Business Media LLC

Date: 18-02-2015

DOI: 10.1007/S00468-015-1161-Z

Herbivore and nutrient control of lawn and bunch grass distributions in a southern African savanna

Publisher: Springer Science and Business Media LLC

Date: 12-06-2009

DOI: 10.1007/S11258-009-9621-4

Phylogenetic ecology of foliar N and P concentrations and N:P ratios across mediterranean‐type ecosystems

Publisher: Wiley

Date: 13-02-2012

DOI: 10.1111/J.1466-8238.2011.00752.X

Nitrogen deposition effects on Mediterranean-type ecosystems: An ecological assessment

Publisher: Elsevier BV

Date: 10-2011

DOI: 10.1016/J.ENVPOL.2010.12.019

Abstract: We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling.

Rooting theories of plant community ecology in microbial interactions

Publisher: Elsevier BV

Date: 08-2010

DOI: 10.1016/J.TREE.2010.05.004

UPTAKE AND ASSIMILATION OF NITRATE AND AMMONIUM BY AN EVERGREEN FYNBOS SHRUB SPECIES PROTEA-REPENS L (PROTEACEAE)

Publisher: Wiley

Date: 06-1984

DOI: 10.1111/J.1469-8137.1984.TB04130.X

Genome-wide scans reveal cryptic population structure in a dry-adapted eucalypt

Publisher: Springer Science and Business Media LLC

Date: 07-04-2015

DOI: 10.1007/S11295-015-0864-Z

Grazing and landscape controls on nitrogen availability across 330 South African savanna sites

Publisher: Wiley

Date: 19-10-2009

DOI: 10.1111/J.1442-9993.2009.01978.X

University Of Cape Town

Location: South Africa

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University Of KwaZulu-Natal

Location: South Africa

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University Of Newcastle Australia

Location: Australia

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University Of Western Australia

Location: Australia

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Edith Cowan University

Location: Australia

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Linkage Infrastructure, Equipment And Facilities - Grant ID: LE100100041

Start Date: 2010

End Date: 12-2010

Amount: $100,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0669240

Start Date: 06-2007

End Date: 02-2011

Amount: $251,000.00

Funder: Australian Research Council