The Experts below are selected from a list of 13716 Experts worldwide ranked by ideXlab platform
Benjamin L. Turner - One of the best experts on this subject based on the ideXlab platform.
-
A climosequence of Chronosequences in southwestern Australia
2017Co-Authors: Benjamin L. Turner, Patrick E. Hayes, Etienne LaliberteAbstract:To examine how climate affects soil development and nutrient availability over long timescales, we studied a series of four long-term Chronosequences along a climate gradient in southwestern Australia. Annual rainfall ranged from 533 mm to 1185 mm (water balance from −900 mm to +52 mm) and each Chronosequence included Holocene (≤ 6.5 ka), Middle Pleistocene (120 to 500 ka), and Early Pleistocene (~2000 ka) dunes. Vegetation changed markedly along the climosequence, from shrubland at the driest site to Eucalyptus forest at the wettest. The carbonate and P content of the parent sand declined along the climosequence, presumably linked to variation in offshore productivity. However, soil development and associated nutrient status followed remarkably consistent patterns along the four Chronosequences. Pedogenesis involved decalcification and secondary carbonate precipitation in Holocene soils and leaching of iron oxides from Middle Pleistocene soils, ultimately yielding bleached quartz sands on the oldest soils. Along all Chronosequences soil pH and total P declined, while C:P and N:P ratios increased, consistent with the predicted shift from N to P limitation of vegetation during ecosystem development. The expected unimodal pattern of leaf area index was most pronounced along wetter Chronosequences, suggesting an influence of climate on the expression of retrogression. The four Chronosequences do not appear to span a pedogenic climate threshold, because exchangeable phosphate and base cations declined consistently during long-term pedogenesis. However, the proportion of the total P in organic form was greater along wetter Chronosequences. We conclude that soils and nutrient availability on the coastal sand plains of southwestern Australia change consistently during long-term pedogenesis, despite marked variation in modern vegetation and climate. The four Chronosequences provide a rare soil-age × climate framework within which to study long-term ecosystem development.
-
Sulfur dynamics during long-term ecosystem development
Biogeochemistry, 2016Co-Authors: Benjamin L. Turner, Leo M Condron, Christine A. M. France, Johannes Lehmann, Dawit Solomon, Duane A. Peltzer, Sarah J. RichardsonAbstract:Long-term soil and ecosystem development involves predictable changes in nitrogen (N) and phosphorus (P) availability and limitation, but far less is known about comparable changes in sulfur (S) despite its importance as an essential plant macronutrient and component of soil organic matter. We used a combination of elemental analysis, X-ray absorption spectroscopy, hydrolytic enzyme assays, and stable S isotope ratios to examine S in soil and leaf tissue along the 120,000-year Franz Josef Chronosequence, New Zealand. Total soil S concentrations increased during the early stages of pedogenesis and then declined as soils aged. There was little variation in soil N:S ratios along the Chronosequence other than in the youngest (5 year old) soil, although the carbon (C):S ratio increased markedly in the oldest soils and the P:S ratio decreased continuously along the Chronosequence. Foliar S concentrations and N:S ratios varied widely among common plant species but did not change consistently with increasing soil age, although foliar P:S declined for several species in the older stages of the Chronosequence. The chemical nature of soil organic S extracted from mineral and organic horizons and determined by S K -edge X-ray absorption near-edge fine-structure (XANES) spectroscopy was dominated by C-bonded S distributed approximately equally in highly-reduced and intermediate oxidation states, although ester-bonded S was also abundant throughout the Chronosequence. Soil sulfatase activity expressed on a soil C basis was highest in young soils, indicating low S availability in the early stage of pedogenesis. Enzymatic C:S and N:S ratios varied little during ecosystem development, although the enzymatic P:S ratio increased continuously along the Chronosequence. Stable S isotope ratios (δ^34S) increased along the Chronosequence, particularly in the early stages of pedogenesis, reflecting a shift in S inputs from primary mineral S to oceanic sulfate in atmospheric deposition. Overall, this first comprehensive assessment of S along a long-term soil Chronosequence suggests that S availability is low in the earliest stage of pedogenesis, but then remains stable throughout the progressive and retrogressive phases of ecosystem development, despite pronounced shifts in the chemistry and dynamics of other nutrients.
-
increasing plant species diversity and extreme species turnover accompany declining soil fertility along a long term Chronosequence in a biodiversity hotspot
Journal of Ecology, 2016Co-Authors: Benjamin L. Turner, Etienne Laliberte, Graham Zemunik, Hans LambersAbstract:Summary Long-term soil Chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well-studied forested soil Chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in species turnover and beta (β) diversity have not been explored, particularly in extremely species-rich regions. We quantified changes in plant species diversity and community composition, and identified the edaphic drivers of these changes, along a >2-million year retrogressive dune Chronosequence in the south-west Australia biodiversity hotspot. We found greater plant species diversity across all growth forms as soil development proceeded and concentrations of soil nutrients, particularly phosphorus (P), diminished to extremely low levels (surface soil total P concentrations of 6 mg P kg−1). Despite the high plant α diversity on older nutrient-impoverished soils, species turnover across the Chronosequence was exceptionally high when all growth forms were considered (mean of 1% of species shared between the youngest and oldest soils), and there was complete turnover of woody species along the Chronosequence. Such extreme species turnover across the Chronosequence reflected large changes in soil chemical properties. In addition, β diversity within individual Chronosequence stages increased with declining soil fertility. Shrubs remained the dominant and most speciose growth form throughout the Chronosequence. Synthesis. The large increase in plant α diversity and the extreme species turnover associated with declining soil fertility highlight the central role of soil properties in driving plant community assembly during long-term ecosystem development, previously only reported from comparatively species-poor regions. Our finding that plant β diversity increased with declining soil fertility points to a novel mechanism whereby extremely low soil fertility, rather than high productivity, promotes high β diversity. These results suggest that the interaction of an exceptionally diverse plant species pool and nutrient-impoverished soils provides the basis for the maintenance of such high β diversity at extremely low soil fertility.
-
Increasing plant species diversity and extreme species turnover accompany declining soil fertility along a long‐term Chronosequence in a biodiversity hotspot
Journal of Ecology, 2016Co-Authors: Graham Zemunik, Benjamin L. Turner, Hans Lambers, Etienne LaliberteAbstract:Summary Long-term soil Chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well-studied forested soil Chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in species turnover and beta (β) diversity have not been explored, particularly in extremely species-rich regions. We quantified changes in plant species diversity and community composition, and identified the edaphic drivers of these changes, along a >2-million year retrogressive dune Chronosequence in the south-west Australia biodiversity hotspot. We found greater plant species diversity across all growth forms as soil development proceeded and concentrations of soil nutrients, particularly phosphorus (P), diminished to extremely low levels (surface soil total P concentrations of 6 mg P kg−1). Despite the high plant α diversity on older nutrient-impoverished soils, species turnover across the Chronosequence was exceptionally high when all growth forms were considered (mean of 1% of species shared between the youngest and oldest soils), and there was complete turnover of woody species along the Chronosequence. Such extreme species turnover across the Chronosequence reflected large changes in soil chemical properties. In addition, β diversity within individual Chronosequence stages increased with declining soil fertility. Shrubs remained the dominant and most speciose growth form throughout the Chronosequence. Synthesis. The large increase in plant α diversity and the extreme species turnover associated with declining soil fertility highlight the central role of soil properties in driving plant community assembly during long-term ecosystem development, previously only reported from comparatively species-poor regions. Our finding that plant β diversity increased with declining soil fertility points to a novel mechanism whereby extremely low soil fertility, rather than high productivity, promotes high β diversity. These results suggest that the interaction of an exceptionally diverse plant species pool and nutrient-impoverished soils provides the basis for the maintenance of such high β diversity at extremely low soil fertility.
-
Soil phosphorus fractionation and nutrient dynamics along the Cooloola coastal dune Chronosequence, southern Queensland, Australia
Geoderma, 2015Co-Authors: Chengrong Chen, Leo M Condron, Enqing Hou, Gary Bacon, Maryam Esfandbod, Jon Olley, Benjamin L. TurnerAbstract:Abstract The amounts and forms of soil phosphorus (P) follow predictable patterns during long-term pedogenesis, but have rarely been examined along subtropical Chronosequences. We quantified changes in soil nutrient stocks, foliar nutrient concentrations, and the chemical forms of soil P along the Cooloola Chronosequence, a series of coastal dunes spanning ca. 500,000 years of pedogenesis in subtropical Queensland. The total P stock in the upper 30 cm of the soil profile declined continuously with soil age, from 229–237 kg ha − 1 on the youngest soils (40 years old) to 24–28 kg ha − 1 on the oldest soils (195–> 460 ka). In contrast, total carbon (C) and nitrogen (N) stocks increased initially along the Chronosequence and then declined in the oldest soils. As a consequence, soil N:P ratios increased continually throughout the sequence, from ≤ 4 on the youngest soils to 27–30 on the oldest soils. This indication of increasing biological P stress and ultimately P limitation was further supported by a decline in foliar P concentrations and increasing foliar N:P ratios of two common plant genera along the Chronosequence. Sequential P fractionation revealed that although all forms of P declined during pedogenesis, young soils contained low concentrations of primary mineral P and relatively high concentrations of occluded P associated with secondary minerals, suggesting that the parent sand originated from strongly-weathered continental soils. We conclude that the Cooloola Chronosequence is an important example of long-term ecosystem development under a subtropical climate, although the pre-weathered nature of the parent sand indicates that the sequence represents a modification of the Walker and Syers model of P transformations during pedogenesis.
David A. Wardle - One of the best experts on this subject based on the ideXlab platform.
-
Responses of communities of soil organisms and plants to soil aging at two contrasting long-term Chronosequences
Soil Biology and Biochemistry, 2017Co-Authors: Stef Bokhorst, Sarah J. Richardson, Paul Kardol, Peter J. Bellingham, Robert M. Kooyman, Susanne Schmidt, David A. WardleAbstract:Soil fertility and vegetation are major drivers of soil communities. Soil community responses to vegetation development and associated changes in soil fertility have been mostly reported for Chronosequences that span time scales from decades to centuries. Here we evaluated soil communities for two contrasting Chronosequences, the Franz Josef Chronosequence in southern New Zealand caused by glacial retreat and spanning 120,000 years, and the Cooloola Chronosequence in eastern Australia caused by aeolian movement of sand that spans 700,000 years. Both Chronosequences feature later-phase retrogressive stages characterized by reduced nutrient availability and plant stature. We hypothesized that soil communities would mirror the patterns of vegetation across these long-term Chronosequences with organism biomasses, abundances and diversity increasing throughout early stages of the succession and declining at retrogression stages. The hypothesis was not consistently supported. Bacterial and fungal biomass increased across the youngest Chronosequence stages but remained unchanged across the later stages, while fungal-to-bacterial ratios increased throughout. Microbial biomass was related to soil nitrogen concentrations across both Chronosequences. Invertebrate abundance and richness increased during the early stages of ecosystem development in both Chronosequences, but different groups peaked at different stages at each Chronosequence, and not all invertebrate groups declined during the retrogressive stages. Invertebrate groups had no consistent correlations with biotic or abiotic ecosystem properties across either Chronosequence. Our study demonstrates that soil organisms track changes in plant biomass and richness and soil fertility during the initial stages of both Chronosequences, but with increasing age of the Chronosequences, these relationships weaken and other factors drive the soil community. Possible explanations for the different patterns in soil communities at the two Chronosequences include that they differ strongly in soil organic matter, nutrient concentrations and abundances of soil organisms (all of which are much higher at Franz Josef than Cooloola), overlaid with different macroclimate and geology, so that different factors are likely to restrict the presence of particular organisms across both Chronosequences. As such, while soil fertility and vegetation are widely recognized as important drivers of the soil community, the manner in which these factors directly and indirectly shape the soil community can vary greatly across organism groups, among Chronosequences, and over the time scales that ecosystems develop.
-
The use of Chronosequences in studies of ecological succession and soil development
Journal of Ecology, 2010Co-Authors: Lawrence R. Walker, David A. Wardle, Richard D. Bardgett, Bruce D. ClarksonAbstract:Summary 1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when Chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a Chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of Chronosequences.
-
Among- and within-species variation in plant litter decomposition in contrasting long-term Chronosequences
Functional Ecology, 2009Co-Authors: David A. Wardle, Richard D. Bardgett, Lawrence R. Walker, Karen I. BonnerAbstract:1. Following major disturbances ecosystem development occurs but in the prolonged absence of disturbance a decline (retrogressive) phase follows in which productivity and nutrient availability diminishes. Although it is recognized that litter quality and decomposition rates decrease as retrogression proceeds, little is known about the extent to which this is driven among- vs. within-species variation across these sequences. 2. We selected six long-term Chronosequences that each included retrogressive stages, in New Zealand, Hawaii, Sweden, Alaska and Australia. Two involve significant species turnover across the sequence so that different species dominate at different stages, two involve low species turnover so that the same dominant species occur at all stages, and two involve some turnover of species but with certain species persisting throughout most of the sequence. 3. For each Chronosequence, we collected litter from each dominant plant species at each stage of that sequence. For each litter collection we measured concentrations of N and P, and performed laboratory decomposition bioassays to measure mass loss, N and P loss, and the response of mass loss to mixture with litters of coexisting species. 4. We found that litter N and P concentrations often declined with increasing ecosystem age, both among- and within-species. However, the relative importance of among- and within-species effects varied across the six Chronosequences. Rates of litter mass, N, and P loss during decomposition sometimes decreased with increasing ecosystem age, but most often at the among-species rather than the within-species level. 5. Litter mixing effects often varied across Chronosequence stages, but the magnitude and direction of these effects was inconsistent among sequences. Variation in litter mixing effects across Chronosequence stages was driven mainly by among- rather than within-species variation. 6. Although several recent studies have emphasized the role of within-species variation on ecosystem properties, our results point to among-species variation as a consistently important ecological driver, with within-species variation being important only for some variables and in some instances. As such they highlight that decomposition processes are most likely to be highly responsive to gradients of soil fertility (such as across Chronosequences) when significant species turnover occurs across the gradient.
-
Changes in the community structure and diversity of soil invertebrates across the Franz Josef Glacier Chronosequence
Soil Biology and Biochemistry, 2008Co-Authors: Enrique Doblas-miranda, Duane A. Peltzer, David A. Wardle, Gregor W. YeatesAbstract:Following the creation of new land surfaces, there is an initial build-up phase of ecosystem development, but after a prolonged absence of major disturbance a retrogressive (decline) phase often follows due to reduced nutrient availability over time. Although many studies have considered how the soil community changes during the build-up phase, the response of this community to the retrogressive phase is poorly known. We measured litter and soil communities of microfauna and macrofauna along the Franz Josef Glacier Chronosequence in New Zealand that spans ca. 120,000 years, and includes well-established build-up and retrogressive stages. We aimed to assess whether the abundances, community structure and diversity of these groups show the same pattern across the sequence as that for vegetation. With regard to microfaunal abundances, litter-dwelling microbe-feeding nematodes were most abundant in the first stage of the Chronosequence, but several other groups of microfauna in both the soil and litter increased sharply during the first few stages and declined sharply during the last (retrogressive) stages. The ratios of bacterial- to fungal-feeding nematodes in both soil and litter were lowest for the final stages of the Chronosequence, and (in the case of soil) for some of the early stages, pointing to domination by the fungal-based energy channel at those stages for which soil organic matter content or quality were lowest. This is consistent with the fungal-based energy channel being better adapted than the bacterial-based channel for resource-poor conditions. The main groups of macroinvertebrates typically had their lowest abundances at the very early and late stages of the Chronosequence, although the relative abundances of different taxa differed during the intermediate stages. Taxonomic diversity of nematodes and macroinvertebrates in both litter and soil varied strongly with Chronosequence stage but differed among taxa; diversity of only one group (macroinvertebrates in litter) declined significantly during retrogression. Diversity of nematodes and macroinvertebrates along the sequence did not closely match tree diversity or soil chemical properties, but community composition of these groups was often related to tree community composition and ratios of soil C to N, C to P and N to P. Different groups of soil invertebrates show contrasting responses to Chronosequence stage, probably because they differ in their relative response to bottom-up and top-down controls. However, the abundance of most groups increased during the build-up phase and declined during retrogression. As such, the build-up and decline phases observed for plant communities and ecosystem processes across long-term Chronosequences also apply to soil communities, pointing to the importance of resource availability as a major driver of soil biota during long-term ecosystem change.
-
Context-dependent changes in the resistance and resilience of soil microbes to an experimental disturbance for three primary plant Chronosequences
Oikos, 2006Co-Authors: Kate H. Orwin, David A. Wardle, Laurence G. GreenfieldAbstract:The extrinsic factors that regulate soil microbial stability (resistance and resilience) are little understood, even though soil microbes are important drivers of ecosystem function and their stability is likely to affect soil carbon storage and plant nutrient availability. Soils were collected across three primary plant Chronosequences (two in New Zealand and one in Hawaii) that differed in climate, parent material and time spans to test the following hypotheses: i) there is a tradeoff between the resistance and resilience of key soil microbial response variables, ii) this tradeoff is related to the relationship of soil microbial resistance and resilience to soil resources, iii) resources change predictably during different primary plant Chronosequences, and iv) if the first three hypotheses hold and are consistent for all three Chronosequences, then soil microbial resistance and resilience should change predictably across different Chronosequences. Results showed that although there was a tradeoff between resistance and resilience, the role of resources in determining this was unclear. Within each Chronosequence, resources that were positively related to resistance were negatively related to resilience and vice versa, consistent with our second hypothesis. However, the direction and strength of correlations between stability and soil resources depended strongly on which soil microbial response variable was measured, and the Chronosequence it was measured in. Total amounts of resources often showed consistent trends with ecosystem development for each Chronosequence, but the way that resource quality changed varied between Chronosequences. At least partly because of the variable nature of these relationships, the trajectory of resistance and resilience during ecosystem development varied considerably across Chronosequences. Thus, although consistent trends were found within each Chronosequence, the relationships between the stability of different soil microbial response variables, resources and ecosystem development depended strongly on which Chronosequence was considered.
Etienne Laliberte - One of the best experts on this subject based on the ideXlab platform.
-
A climosequence of Chronosequences in southwestern Australia
2017Co-Authors: Benjamin L. Turner, Patrick E. Hayes, Etienne LaliberteAbstract:To examine how climate affects soil development and nutrient availability over long timescales, we studied a series of four long-term Chronosequences along a climate gradient in southwestern Australia. Annual rainfall ranged from 533 mm to 1185 mm (water balance from −900 mm to +52 mm) and each Chronosequence included Holocene (≤ 6.5 ka), Middle Pleistocene (120 to 500 ka), and Early Pleistocene (~2000 ka) dunes. Vegetation changed markedly along the climosequence, from shrubland at the driest site to Eucalyptus forest at the wettest. The carbonate and P content of the parent sand declined along the climosequence, presumably linked to variation in offshore productivity. However, soil development and associated nutrient status followed remarkably consistent patterns along the four Chronosequences. Pedogenesis involved decalcification and secondary carbonate precipitation in Holocene soils and leaching of iron oxides from Middle Pleistocene soils, ultimately yielding bleached quartz sands on the oldest soils. Along all Chronosequences soil pH and total P declined, while C:P and N:P ratios increased, consistent with the predicted shift from N to P limitation of vegetation during ecosystem development. The expected unimodal pattern of leaf area index was most pronounced along wetter Chronosequences, suggesting an influence of climate on the expression of retrogression. The four Chronosequences do not appear to span a pedogenic climate threshold, because exchangeable phosphate and base cations declined consistently during long-term pedogenesis. However, the proportion of the total P in organic form was greater along wetter Chronosequences. We conclude that soils and nutrient availability on the coastal sand plains of southwestern Australia change consistently during long-term pedogenesis, despite marked variation in modern vegetation and climate. The four Chronosequences provide a rare soil-age × climate framework within which to study long-term ecosystem development.
-
increasing plant species diversity and extreme species turnover accompany declining soil fertility along a long term Chronosequence in a biodiversity hotspot
Journal of Ecology, 2016Co-Authors: Benjamin L. Turner, Etienne Laliberte, Graham Zemunik, Hans LambersAbstract:Summary Long-term soil Chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well-studied forested soil Chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in species turnover and beta (β) diversity have not been explored, particularly in extremely species-rich regions. We quantified changes in plant species diversity and community composition, and identified the edaphic drivers of these changes, along a >2-million year retrogressive dune Chronosequence in the south-west Australia biodiversity hotspot. We found greater plant species diversity across all growth forms as soil development proceeded and concentrations of soil nutrients, particularly phosphorus (P), diminished to extremely low levels (surface soil total P concentrations of 6 mg P kg−1). Despite the high plant α diversity on older nutrient-impoverished soils, species turnover across the Chronosequence was exceptionally high when all growth forms were considered (mean of 1% of species shared between the youngest and oldest soils), and there was complete turnover of woody species along the Chronosequence. Such extreme species turnover across the Chronosequence reflected large changes in soil chemical properties. In addition, β diversity within individual Chronosequence stages increased with declining soil fertility. Shrubs remained the dominant and most speciose growth form throughout the Chronosequence. Synthesis. The large increase in plant α diversity and the extreme species turnover associated with declining soil fertility highlight the central role of soil properties in driving plant community assembly during long-term ecosystem development, previously only reported from comparatively species-poor regions. Our finding that plant β diversity increased with declining soil fertility points to a novel mechanism whereby extremely low soil fertility, rather than high productivity, promotes high β diversity. These results suggest that the interaction of an exceptionally diverse plant species pool and nutrient-impoverished soils provides the basis for the maintenance of such high β diversity at extremely low soil fertility.
-
Increasing plant species diversity and extreme species turnover accompany declining soil fertility along a long‐term Chronosequence in a biodiversity hotspot
Journal of Ecology, 2016Co-Authors: Graham Zemunik, Benjamin L. Turner, Hans Lambers, Etienne LaliberteAbstract:Summary Long-term soil Chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well-studied forested soil Chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in species turnover and beta (β) diversity have not been explored, particularly in extremely species-rich regions. We quantified changes in plant species diversity and community composition, and identified the edaphic drivers of these changes, along a >2-million year retrogressive dune Chronosequence in the south-west Australia biodiversity hotspot. We found greater plant species diversity across all growth forms as soil development proceeded and concentrations of soil nutrients, particularly phosphorus (P), diminished to extremely low levels (surface soil total P concentrations of 6 mg P kg−1). Despite the high plant α diversity on older nutrient-impoverished soils, species turnover across the Chronosequence was exceptionally high when all growth forms were considered (mean of 1% of species shared between the youngest and oldest soils), and there was complete turnover of woody species along the Chronosequence. Such extreme species turnover across the Chronosequence reflected large changes in soil chemical properties. In addition, β diversity within individual Chronosequence stages increased with declining soil fertility. Shrubs remained the dominant and most speciose growth form throughout the Chronosequence. Synthesis. The large increase in plant α diversity and the extreme species turnover associated with declining soil fertility highlight the central role of soil properties in driving plant community assembly during long-term ecosystem development, previously only reported from comparatively species-poor regions. Our finding that plant β diversity increased with declining soil fertility points to a novel mechanism whereby extremely low soil fertility, rather than high productivity, promotes high β diversity. These results suggest that the interaction of an exceptionally diverse plant species pool and nutrient-impoverished soils provides the basis for the maintenance of such high β diversity at extremely low soil fertility.
-
soil development and nutrient availability along a 2 million year coastal dune Chronosequence under species rich mediterranean shrubland in southwestern australia
Ecosystems, 2015Co-Authors: Benjamin L. Turner, Etienne LaliberteAbstract:Soil Chronosequences provide valuable model systems to investigate pedogenesis and associated effects of nutrient availability on biological communities. However, long-term Chronosequences occurring under seasonally dry climates remain scarce. We assessed soil development and nutrient dynamics along the Jurien Bay Chronosequence, a 2 million-year sequence of coastal dunes in southwestern Australia. The Chronosequence is significant because it occurs in a Mediterranean climate and supports hyperdiverse shrublands within a global biodiversity hotspot. Young soils formed during the Holocene ( 2,000,000 years old) are completely leached of iron oxides and consist of bleached quartz sand several meters deep. Changes in soil organic matter and nutrient status along the Jurien Bay Chronosequence are consistent with patterns observed along other long-term Chronosequences and correspond closely to expectations of the Walker and Syers (1976) model of biogeochemical change during pedogenesis. Organic carbon and nitrogen (N) accumulate rapidly to maximum amounts in intermediate-aged Holocene dunes and then decline as soils age. In contrast, total phosphorus (P) declines continuously along the Chronosequence to extremely low levels after 2 million years of pedogenesis, eventually representing some of the lowest P soils globally. Ratios of soil organic carbon to P and N to P increase continuously along the Chronosequence, consistent with a shift from N limitation on young soils to extreme P limitation on old soils. Phosphorus fractionation by sequential extraction reveals a rapid decline in primary and non-occluded phosphate and an increase in organic and occluded P as soils age. Concentrations of extractable (that is, readily bioavailable) N and P, as well as exchangeable cations, are greatest in Holocene dunes and decline to low levels in Pleistocene dunes. Extractable micronutrient concentrations were generally very low and varied little across the Chronosequence. We conclude that the Jurien Bay Chronosequence is an important example of changing patterns of nutrient limitation linked to long-term soil and ecosystem development under a Mediterranean climate.
-
experimental assessment of nutrient limitation along a 2 million year dune Chronosequence in the south western australia biodiversity hotspot
Journal of Ecology, 2012Co-Authors: Etienne Laliberte, Benjamin L. Turner, Graham Zemunik, Thomas Costes, Stuart J Pearse, Karlheinz Wyrwoll, Hans LambersAbstract:Summary 1. The classical model of long-term ecosystem development suggests that primary productivity is limited by nitrogen (N) on young substrates and phosphorus (P) on older substrates. Measurements of foliar and soil nutrients along soil Chronosequences support this model, but direct tests through nutrient-addition experiments are rare. 2. We conducted a nutrient-limitation bioassay using phytometer species grown in soils from five stages of a >2-million-year dune Chronosequence in south-western Australia. This long-term Chronosequence is located within a region of exceptionally high plant species diversity and has not been previously studied in the context of ecosystem development. 3. Growth of unfertilized phytometers, a proxy for primary productivity, peaked on young soils (hundreds to a few thousand years) and then declined steadily on older soils. This decline was linked to P limitation, and its rapid appearance (<7000 years) compared to other sequences reflects the low P concentration in the parent material. As predicted, growth of canola was N-limited on the youngest soil (stage 1), co-limited by multiple nutrients in stage 2 and increasingly P-limited thereafter. 4. Growth of wheat was P-limited from stage 2 onwards, yet on the youngest soil it was co-limited by potassium (K) and micronutrients – most likely iron (Fe). Nitrogen addition also decreased the root:shoot ratio of wheat such that shoot growth was higher than in the control. We attribute these responses to a parent material that is very low in K and N and strongly alkaline (pH [H2O] > 9), being of a marine origin (i.e. carbonate dunes). Fe is poorly soluble at high pH and K likely plays a role in the secretion of Fe-mobilizing exudates from wheat roots. 5. Synthesis. Our results provide strong support for the long-term ecosystem-development model, particularly with regard to the appearance of P limitation and associated declines in productivity. However, our study also shows that N cannot be assumed to invariably be the most important limiting nutrient in young soils, and it is unlikely to be the only limiting nutrient in calcareous soils. This south-western Australian long-term Chronosequence provides an excellent opportunity to explore edaphic controls over plant species diversity.
Natasa J. Vidic - One of the best experts on this subject based on the ideXlab platform.
-
Soil-age relationships and correlations: comparison of Chronosequences in the Ljubljana Basin, Slovenia and USA
Catena, 1998Co-Authors: Natasa J. VidicAbstract:Abstract A comparison of soil development indices established in Chronosequences from the Ljubljana Basin (humid climate), California (Mediterranean), Pennsylvania (humid) and New Mexico (arid) suggests that the rates of soil development expressed by the indices increase with increasing precipitation, even though some individual soil properties, notably rubification, develop faster in xeric areas. Parent material composition does not seem to affect the indices significantly. Therefore similarity of present climate and climatic history between compared Chronosequences remains a pre-requisite for soil-age correlations. The chronofunctions are not suitable for exact dating and age correlations because variability of soil development within each geomorphic surface prevents the dependent variables (soil properties) being used to predict the independent variable (soil age). Changes in age estimates affect calculated rates of soil development. In the Ljubljana Basin Chronosequence rates changed by up to 20% for semi-logarithmic chronofunctions and by up to 180% for linear chronofunctions if minimum or maximum ages were used instead of best estimates. Better dating methods and more replicate profiles on each geomorphic surface would diminish these problems. Statistical techniques that account for variability in both variables (maximum likelihood estimates) also help improve age correlations. Within the Ljubljana Basin Chronosequence some time dependent soil properties can be used to discriminate between groups of geomorphic surfaces, but each of them has a limited ability to do so because the confidence intervals for deposits overlap. The inability of soil properties to discriminate between all members of the Chronosequence is attributed to the large intrinsic variability of soils, the insufficient number of replicate profiles on each deposit and the decreasing rate of soil development with age.
-
Rates of soil development of the Chronosequence in the Ljubljana Basin, Slovenia
Geoderma, 1997Co-Authors: Natasa J. Vidic, Franc LobnlkAbstract:Abstract Rates of soil development (determined from the slopes of chronofunctions of soil development indices) of a post-incisive Chronosequence that formed on a sequence of outwash terraces (ages 5 ka to 1.8 Ma) in the Ljubljana Basin decrease with time (i.e., soil development increases with the logarithm or power of soil age). The development of soil properties can be affected by soil forming factors other than time (climatic fluctuations, intrinsic thresholds), and does not reach a steady state during the observed time-span. Cumulative soil development expressed by weighted means of profile development calculated by combining the four most time-dependent properties (rubification, total texture, pH-decrease, and clay films), however, ceases to increase at about 980 ka; therefore. a steady state could be assumed. Weighted means cease to increase because some of the four properties continue to increase whereas others begin to decrease after 980 ka. Steady state could thus be defined as a stage in soil development when the sum of progressive (those that contribute to the increase in soil development: weathering, translocations, profile differentiation) and regressive (those that contribute to the decrease in soil development or cause the changes in the direction of development: intrinsic thresholds, erosion) processes equals zero (i.e., regressive = progressive). The trends in soil development indices are consistent with the hypothesis that weathering followed by clay translocation were the main pedogenic processes that affected the soils of the Ljubljana Basin Chronosequence. Rates of soil development derived from chronofunctions can change if age estimates change considerably. The change in age estimates within the uncertainty intervals for the Ljubljana Basin Chronosequences caused the differences in rates that were less than 15% for semi-logarithmic and power chronofunctions, and about 80% for linear chronofunctions. Since most of the Ljubljana Basin chronofunctions were semi-logarithmic or power, the estimated rates would not change significantly if the age estimates changed within the existing uncertainty interval. Compared to Chronosequences in other climatic settings (humid, xeric, aridic), the rates of soil development in the humid Ljubljana Basin generally exceed those in other areas, especially in xeric and aridic areas. The rates of soil morphology development seem to depend on the climatic conditions, and generally increase with increasing precipitation, even though some of the properties, such as rubification, may develop faster in xeric than in humid areas.
Sarah J. Richardson - One of the best experts on this subject based on the ideXlab platform.
-
Responses of communities of soil organisms and plants to soil aging at two contrasting long-term Chronosequences
Soil Biology and Biochemistry, 2017Co-Authors: Stef Bokhorst, Sarah J. Richardson, Paul Kardol, Peter J. Bellingham, Robert M. Kooyman, Susanne Schmidt, David A. WardleAbstract:Soil fertility and vegetation are major drivers of soil communities. Soil community responses to vegetation development and associated changes in soil fertility have been mostly reported for Chronosequences that span time scales from decades to centuries. Here we evaluated soil communities for two contrasting Chronosequences, the Franz Josef Chronosequence in southern New Zealand caused by glacial retreat and spanning 120,000 years, and the Cooloola Chronosequence in eastern Australia caused by aeolian movement of sand that spans 700,000 years. Both Chronosequences feature later-phase retrogressive stages characterized by reduced nutrient availability and plant stature. We hypothesized that soil communities would mirror the patterns of vegetation across these long-term Chronosequences with organism biomasses, abundances and diversity increasing throughout early stages of the succession and declining at retrogression stages. The hypothesis was not consistently supported. Bacterial and fungal biomass increased across the youngest Chronosequence stages but remained unchanged across the later stages, while fungal-to-bacterial ratios increased throughout. Microbial biomass was related to soil nitrogen concentrations across both Chronosequences. Invertebrate abundance and richness increased during the early stages of ecosystem development in both Chronosequences, but different groups peaked at different stages at each Chronosequence, and not all invertebrate groups declined during the retrogressive stages. Invertebrate groups had no consistent correlations with biotic or abiotic ecosystem properties across either Chronosequence. Our study demonstrates that soil organisms track changes in plant biomass and richness and soil fertility during the initial stages of both Chronosequences, but with increasing age of the Chronosequences, these relationships weaken and other factors drive the soil community. Possible explanations for the different patterns in soil communities at the two Chronosequences include that they differ strongly in soil organic matter, nutrient concentrations and abundances of soil organisms (all of which are much higher at Franz Josef than Cooloola), overlaid with different macroclimate and geology, so that different factors are likely to restrict the presence of particular organisms across both Chronosequences. As such, while soil fertility and vegetation are widely recognized as important drivers of the soil community, the manner in which these factors directly and indirectly shape the soil community can vary greatly across organism groups, among Chronosequences, and over the time scales that ecosystems develop.
-
Sulfur dynamics during long-term ecosystem development
Biogeochemistry, 2016Co-Authors: Benjamin L. Turner, Leo M Condron, Christine A. M. France, Johannes Lehmann, Dawit Solomon, Duane A. Peltzer, Sarah J. RichardsonAbstract:Long-term soil and ecosystem development involves predictable changes in nitrogen (N) and phosphorus (P) availability and limitation, but far less is known about comparable changes in sulfur (S) despite its importance as an essential plant macronutrient and component of soil organic matter. We used a combination of elemental analysis, X-ray absorption spectroscopy, hydrolytic enzyme assays, and stable S isotope ratios to examine S in soil and leaf tissue along the 120,000-year Franz Josef Chronosequence, New Zealand. Total soil S concentrations increased during the early stages of pedogenesis and then declined as soils aged. There was little variation in soil N:S ratios along the Chronosequence other than in the youngest (5 year old) soil, although the carbon (C):S ratio increased markedly in the oldest soils and the P:S ratio decreased continuously along the Chronosequence. Foliar S concentrations and N:S ratios varied widely among common plant species but did not change consistently with increasing soil age, although foliar P:S declined for several species in the older stages of the Chronosequence. The chemical nature of soil organic S extracted from mineral and organic horizons and determined by S K -edge X-ray absorption near-edge fine-structure (XANES) spectroscopy was dominated by C-bonded S distributed approximately equally in highly-reduced and intermediate oxidation states, although ester-bonded S was also abundant throughout the Chronosequence. Soil sulfatase activity expressed on a soil C basis was highest in young soils, indicating low S availability in the early stage of pedogenesis. Enzymatic C:S and N:S ratios varied little during ecosystem development, although the enzymatic P:S ratio increased continuously along the Chronosequence. Stable S isotope ratios (δ^34S) increased along the Chronosequence, particularly in the early stages of pedogenesis, reflecting a shift in S inputs from primary mineral S to oceanic sulfate in atmospheric deposition. Overall, this first comprehensive assessment of S along a long-term soil Chronosequence suggests that S availability is low in the earliest stage of pedogenesis, but then remains stable throughout the progressive and retrogressive phases of ecosystem development, despite pronounced shifts in the chemistry and dynamics of other nutrients.
-
n and p in new zealand soil Chronosequences and relationships with foliar n and p
Biogeochemistry, 2005Co-Authors: R L Parfitt, David A. Coomes, Sarah J. Richardson, D J Ross, M C Smale, Randy A DahlgrenAbstract:The growth of forest species in soil development Chronosequences becomes increasingly phosphorus (P)-limited with time, as P is weathered, eroded and leached from soil. Foliar nitrogen (N) concentrations also tend to decrease with soil age when vegetation may be limited in both N and P. Here we report on soil development in temperate rain forests along three New Zealand Chronosequences that have minimal pollution and disturbance from human activities, at Franz Josef, Waitutu and Central Volcanic Plateau, and on factors influencing soil net N mineralization (aerobic; 56 days) and foliar N and P concentrations. Except in very young soils (<500 years), at least 85% of total-P in mineral soil (0–10 cm) was transformed to organic-P. In each Chronosequence, total-P declined with time, and foliar N:P ratios (mass) generally increased from 8 to 15–18, suggesting P was more limiting than N in the oldest soils of the Chronosequence. There was a negative relationship between net N mineralization and C:N ratio for mineral soil. For the FH (organic) layer, net N mineralization had the strongest relationships with total-N concentration (positively) and C:organic-P ratio (negatively); however, relationships varied with forest group, suggesting that other factors were also important. Foliar P of kamahi (Weinmannia racemosa Linn. f.), a dominant canopy species, was related to soil organic-P, suggesting mineralization was an important process for tree nutrition.Foliar N was positively related to N concentration in the FH layer, but was not significantly related to any measured property in mineral soil, possibly because of the wide range of soils. The consistent declines in both soil and foliar P across the contrasting Chronosequences strongly suggest that vegetation becomes progressively P-limited during long-term ecosystem development.
-
RESORPTION PROFICIENCY ALONG A Chronosequence: RESPONSES AMONG COMMUNITIES AND WITHIN SPECIES
Ecology, 2005Co-Authors: Sarah J. Richardson, Duane A. Peltzer, Robert B. Allen, Matt S. McgloneAbstract:Soil nitrogen and phosphorus pools shift strongly along soil Chronosequences worldwide, but variation in plant nutrient resorption along these sequences is poorly understood. We quantified leaf and litter nutrient concentrations in 28 woody species along the Franz Josef soil Chronosequence, New Zealand, a strong fertility gradient in temperate rain forest, to address two questions: How do leaf and litter nutrient concentrations vary along a soil Chronosequence? And are the community-level responses driven by compositional differences among fertile and infertile sites, or by consistent changes in resorption proficiency within growth forms, and within species? Community-level leaf and litter N and P concentrations declined by between 67% and 88% along the soil Chronosequence, and these responses were remarkably consistent within three contrasting growth forms (angiosperms, conifers, tree ferns), and within individual species. In spite of the three growth forms sharing similar responses to the soil Chronosequence, tree ferns had higher absolute concentrations of leaf N, leaf P, and litter N relative to angiosperms, and higher concentrations of leaf N relative to conifers. These results clearly indicate that differences among fertile and infertile sites are driven both by compositional differences, as has been previously demonstrated, and by plasticity of individual species.