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99 results for “Chronosequence”
Data from: Foliar nutrient concentrations and resorption efficiency in plants of contrasting nutrient-acquisition strategies along a 2-million year dune chronosequence
1. Long-term pedogenesis leads to important changes in the availability of soil nutrients, especially nitrogen (N) and phosphorus (P). Changes in the availability of micronutrients can also occur, but are less well understood. We explored whether changes in leaf nutrient concentrations and resorption were consistent with a shift from N to P limitation of plant productivity with soil age along a >2-million year dune chronosequence in south-western Australia. We also compared these traits among plants of contrasting nutrient-acquisition strategies, focusing on N, P and micronutrients. 2. The range in leaf [P] for individual species along the chronosequence was exceptionally large for both green (103–3000 μg P g-1) and senesced (19–5600 μg P g-1) leaves, almost equalling that found globally. From the youngest to the oldest soil, cover-weighted mean leaf [P] declined from 1840 to 228 μg P g-1, while P-resorption efficiency increased from 0% to 79%. All species converged towards a highly conservative P-use strategy on the oldest soils. 3. Declines in cover-weighted mean leaf [N] with soil age were less strong than for leaf [P], ranging from 13.4 mg N g-1 on the youngest soil to 9.5 mg N g-1 on the oldest soil. However, mean leaf N-resorption efficiency was greatest (45%) on the youngest, N-poor soils. Leaf N:P ratio increased from 8 on the youngest soil to 42 on the oldest soil. 4. Leaf zinc (Zn) concentrations were low across all chronosequence stages, but mean Zn-resorption efficiency was greatest (55–74%) on the youngest calcareous dunes, reflecting low Zn availability at high pH. 5. N2-fixing species had high leaf [N] compared with other species. Non-mycorrhizal species had very low leaf [P] and accumulated Mn across all soils. We surmise that this reflects Mn solubilisation by organic acids released for P acquisition. 6. Synthesis. Our results show community-wide variation in leaf nutrient concentrations and resorption that is consistent with a shift from N to P limitation during long-term ecosystem development. High Zn resorption on young calcareous dunes supports the possibility of micronutrient co-limitation. High leaf [Mn] on older dunes suggests the importance of carboxylate release for P acquisition. Our results show a strong effect of soil nutrient availability on nutrient-use efficiency, and reveal considerable differences among plants of contrasting nutrient-acquisition strategies.
Data from: Trait convergence in photosynthetic nutrient-use efficiency along a 2-million year dune chronosequence in a global biodiversity hotspot
1. The Jurien Bay dune chronosequence in south-western Australia's biodiversity hotspot comprises sites differing in nutrient availability, with phosphorus (P) availability declining strongly with increasing soil age. We have explored the exceptionally high photosynthetic P-use efficiency (PPUE) of Proteaceae in this region, triggering the question what the PPUE of co-occurring species in other families might be along the Jurien Bay chronosequence. 2. We explored how traits associated with PPUE, photosynthetic nitrogen (N)-use efficiency (PNUE) and leaf respiration might converge along the chronosequence, and whether Proteaceae and non-Proteaceae species differ in leaf traits associated with nutrient use. 3. Seven to 10 species were sampled at three sites differing in nutrient availability (ranging from N- to P-limited). Measurements of leaf light-saturated photosynthesis and dark respiration were integrated with measurements of total N and P concentration in both mature and senesced leaves, and leaf mass per unit area (LMA). 4. Contrary to what is known for other chronosequences, rates of photosynthesis and respiration did not decrease with increasing soil age and LMA along the Jurien Bay chronosequence. However, they increased when expressed per unit leaf P. Both N and P were used much more efficiently for photosynthesis on nutrient-poor sites, in both Proteaceae and non-Proteaceae species. Proteaceae had the fastest rate of photosynthesis per unit leaf P, followed by species that preferentially allocate P to mesophyll cells, rather than epidermal cells. 5. Synthesis. Our results show that with declining soil P availability, PPUE of all investigated species from different families increased. Plants growing on the oldest, most nutrient-impoverished soils exhibited similar rates of CO2-exchange as plants growing on more nutrient-rich younger soils, and extraordinarily high PPUE. This indicates convergence in leaf traits related to photosynthetic nutrient use on severely P-impoverished sites.
Collapse of dispersal trait diversity across a long-term chronosequence reveals a strong negative impact of frugivore extinctions on forest resilience
<p><span><b>1. </b></span><span>Understanding how seed dispersal disruption may alter plant community diversity and dynamics over a large temporal scale remains a challenge. Here, we use a long-term chronosequence to compare changes in the richness and composition of different dispersal trait assemblages in communities established before and after human colonisation in the Mascarene archipelago.</span></p> <p><span><b>2. </b></span><span>Our study was located on Réunion on the slopes of the Piton de la Fournaise, one of the most active volcanoes worldwide. We analysed 151 vegetation surveys on lava flows dated between 1401-AD and 1956-AD and in tropical rainforests established on older substrata. We defined five classes of substratum age, according to the well-known chronology of native frugivore defaunation: "old substrata" and </span>[1401, 1665[ when frugivores were abundant and diverse <span>before permanent human settlement</span>; [1665, 1800[ when large-bodied frugivore populations were strongly reduced; [1800, 1900[ when large-bodied frugivores went extinct and small-bodied frugivores were still abundant; [1900, 1956] <span>decline in the population of small-bodied frugivores. Based on dispersal traits, we categorised 146 native woody species as anemochorous, small fleshy-fruited or large fleshy-fruited, i.e. plant of which fruit could not theoretically be dispersed by extant frugivores.</span></p> <p><span><b>3. </b></span><span>Changes in dispersal trait diversity strongly correlated with the chronology of defaunation. Species-rich communities settled before human colonisation were strongly dominated by fleshy-fruited species. </span>L<span>arge fleshy-fruited plants in the oldest communities </span>settled after human colonisation <span>declined markedly and almost disappeared after 1800. The richness of small fleshy-fruited plants decreased less rapidly across the chronosequence, with medium levels on </span>[1665, 1800[ and [1800, 1900[ <span>lava flows and low levels on </span>[1900, 1956] lava flows<span>. Conversely, the richness of anemochorous plants remained unchanged. Communities settled before human colonisation had a similar composition. Fleshy-fruited assemblages showed strong species loss across the chronosequence, while anemochorous assemblages showed strong species turnover, which was probably due to lower dispersal limitation.</span></p> <p><span><b>4. Synthesis. </b></span><span>Our results provide the first insights into the tremendous impact that frugivore extinction has on plant colonisation dynamics over 300 years. The dramatic loss of fleshy-fruited plant diversity on historical lava flows highlights the irreplaceable dispersal role played by frugivores, especially large-bodied species. The conservation of </span>plant-animal mutualistic interactions<span> is invaluable and refaunation efforts need to be undertaken in areas where frugivores have been extirpated.</span></p>
Data from: Time for recovery of riparian plants in restored northern Swedish streams: a chronosequence study
A lack of ecological responses in stream restoration projects has been prevalent throughout recent literature with many studies reporting insufficient time for recovery. We assessed the relative importance of time, site variables, and landscape setting for understanding how plant species richness and understory productivity recover over time in riparian zones of northern Swedish streams. We used a space-for-time substitution consisting of 13 stream reaches restored 5–25 years ago, as well as five unrestored channelized reference reaches. We inventoried the riparian zone for all vascular plant species along 60-m study reaches and quantified cover and biomass in plots. We found that while species richness increased with time, understory biomass decreased. Forbs made up the majority of the species added, while the biomass of graminoids decreased the most over time, suggesting that the reduced dominance of graminoids favored less productive forbs. Species richness and density patterns could be attributed to dispersal limitation, with anemochorous species being more associated with time after restoration than hydrochorous, zoochorous, or vegetatively reproducing species. Using multiple linear regression, we found that time along with riparian slope and riparian buffer width (e.g., distance to logging activities) explained the most variability in species richness, but that variability in total understory biomass was explained primarily by time. The plant community composition of restored reaches differed from that of channelized references, but the difference did not increase over time. Rather, different time categories had different successional trajectories that seemed to converge on a unique climax community for that time period. Given our results, timelines for achieving species richness objectives should be extended to 25 years or longer if recovery is defined as a saturation of the accumulation of species over time. Other recommendations include making riparian slopes as gentle as possible given the landscape context and expanding riparian buffer width for restoration to have as much impact as possible.
Data from: Reproductive traits as predictors of assembly chronosequence patterns in epiphyllous bryophyte metacommunities
1) Understanding the mechanisms underlying species assembly is a central focus of plant ecology and is crucial to revealing how plant communities are structured. However, the temporal limitations of most terrestrial plant communities preclude collection of species assembly data in a tractable time-frame. 2) The aim of this study is to investigate the importance of dispersal potential, as estimated by inter-specific variation in sexual and asexual expression, as a predictor of patch chronosequence assembly for epiphyllous (leaf-inhabiting) bryophytes. Secondarily, we investigate whether spatio-temporal patterns in patch turnover and compositional variation infer evidence of local (within-patch) population processes. The frequency and distribution of 55 epiphyllous bryophytes across five leaf age classes were studied on an understory shrub Piper grande (Piperaceae) in pre-montane Panamanian tropical forest. Logistical models were used to test whether inter-specific variation in dispersal-related life history traits predicts assembly order. Beta diversity and ordination analyses were employed to examine nestedness versus turnover, and probe for repeatable patterns in patch chronosequence assembly, respectively. 3) Our results emphasize the importance of dispersal potential on species assembly patterns as earlier arrivals exhibit greater probabilities of sexual and specialized asexual expression. High turnover coupled with temporal convergence in species composition also point to evidence of within-patch biotic filtering. 4) Synthesis: Epiphylls are locally diverse in humid tropical forests worldwide; however, the mechanisms which maintain their high local diversity are unknown. This study suggests that inter-specific variation in dispersal capacity in combination with diffuse indirect effects are the principal contributors to the high alpha-diversity of these ephemeral metacommunities.
Data from: Impact of a hurricane on the herpetofaunal assemblages of a successional chronosequence in a tropical dry forest
Land‐use change is the main cause of deforestation and degradation of tropical forest in Mexico. Frequently, these lands are abandoned leading to a mosaic of natural vegetation in secondary succession. Further degradation of the natural vegetation in these lands could be exacerbated by stochastic catastrophic events such as hurricanes. Information on the impact of human disturbance parallel to natural disturbance has not yet been evaluated for faunal assemblages in tropical dry forests. To evaluate the response of herpetofaunal assemblages to the interaction of human and natural disturbances, we used information of pre‐ and post‐hurricane herpetofaunal assemblages inhabiting different successional stages (pasture, early forest, young forest, intermediate forest, and old growth forest) of dry forest. Herpetofaunal assemblages were surveyed in all successional stages two years before and two years after the hurricane Jova that hit the Pacific Coast of Mexico on October 2011. We registered 4093 individuals of 61 species. Overall, there were only slight effects of successional stage, hurricane Jova or the interaction between them on abundance, observed species richness and diversity of the herpetofauna. However, we found marked changes in estimated richness and composition of frogs, lizards, and snakes among successional stages in response to hurricane Jova. Modifications in vegetation structure as result of hurricane pass promoted particular changes in each successional stage and taxonomic group (anurans, lizards, and snakes). Secondary forests at different stages of succession may attenuate the negative effects of an intense, short‐duration, and low‐frequency natural disturbance such as hurricane Jova on successional herpetofaunal trajectories and species turnover.
Data from: Ecosystem carbon density and allocation across a chronosequence of longleaf pine forests
Forests can partially offset greenhouse gas emissions and contribute to climate change mitigation, mainly through increases in live biomass. We quantified carbon (C) density in 20 managed longleaf pine (Pinus palustris Mill.) forests ranging in age from five to 118 years located across the southeastern USA and estimated above and belowground C trajectories. Ecosystem C stock (all pools including soil C) and aboveground live tree C increased nonlinearly with stand age and the modeled asymptotic maxima were 168 Mg C/ha and 80 Mg C/ha, respectively. Accumulation of ecosystem C with stand age was driven mainly by increases in aboveground live tree C, which ranged from <1 Mg C/ha to 74 Mg C/ha and comprised <1% to 39% of ecosystem C. Live root C (sum of below-stump C, ground penetrating radar measurement of lateral root C, and live fine root C) increased with stand age and represented 4% to 22% of ecosystem C. Soil C was related to site index, but not to stand age, and comprised 39% to 92% of ecosystem C. Live understory C, forest floor C, down dead wood C and standing dead wood C were small fractions of ecosystem C in these frequently burned stands. Stand age and site index accounted for 76% of the variation in ecosystem C among stands. The mean root to shoot ratio calculated as the average across all stands (excluding the grass stage stand) was 0.54 (standard deviation of 0.19) and higher than reports for other conifers. Long-term accumulation of live tree C, combined with the larger role of belowground accumulation of lateral root C than in other forest types, indicates a role of longleaf pine forests in providing disturbance-resistant C storage that can balance the more rapid C accumulation and C removal associated with more intensively managed forests. Although other managed southern pine systems sequester more C over the short-term, we suggest that longleaf pine forests can play a meaningful role in regional forest C management.
Radiocarbon in Bulk and Respired CO2 from the Cowlitz River Chronosequence, Washington, USA
<p>This is part of a study that measured radiocarbon in bulk soil carbon and CO2 respired in incubations from a soil chronosequence on andesite. The study sites are the same ones that are reported in Lawrence et al. 2015 (reference below). However, the soils reported in Lawrence et al. 2015 were sampled in 2010. The samples reported here (previously unpublished) were collected. in 2009. The incubations were performed at the University of California Irvine; the bulk soil samples were collected at the same time but splits were analyzed separately. </p> <p>Corey R. Lawrence, Jennifer W. Harden, Xiaomei Xu, Marjorie S. Schulz, Susan E. Trumbore, (2015) Long-term controls on soil organic carbon with depth and time: A case study from the Cowlitz River Chronosequence, WA USA. Geoderma, V 247-248: p. 73-87, DOI: <a href="https://doi.org/10.1016/j.geoderma.2015.02.005">10.1016/j.geoderma.2015.02.005</a></p> <p> </p> <p>The associated ISRaD Template Information File provides the names and descriptions of all fields.</p>
Soil radiocarbon data from a fire chronosequence near Delta Junction, Alaska
<p>Soil radiocarbon data sampled along a crown fire (stand replacing) chronosequence located near Delta Junction, Alaska, USA consisting of three sites that burned in 2010 (Gilles Creek fire), 2004 (Camp Creek fire), and about 100 years ago (control). </p>
Data from: Bee communities along a prairie restoration chronosequence: similar abundance and diversity, distinct composition
Recognition of the importance of bee conservation has grown in response to declines of managed honey bees and some wild bee species. Habitat loss has been implicated as a leading cause of declines, suggesting that ecological restoration is likely to play an increasing role in bee conservation efforts. In the Midwestern USA, restoration of tallgrass prairie has traditionally targeted plant community objectives without explicit consideration for bees. However, restoration of prairie vegetation is likely to provide ancillary benefits to bees through increased foraging and nesting resources. We investigated community assembly of bees across a chronosequence of restored eastern tallgrass prairies and compared patterns to those in control and reference habitats (old fields and prairie remnants, respectively). We collected bees for three years and measured diversity and abundance of in-bloom flowering plants, vegetation structure, ground cover, and surrounding land use as predictors of bee abundance and bee taxonomic and functional diversity. We found that site-level variables, but not site type or restoration age, were significant predictors of bee abundance (bloom diversity: p = 0.004, bare ground cover: p = 0.02) and bee diversity (bloom diversity: p = 0.01). There were significant correlations between overall composition of bee and blooming plant communities (mantel test: p = 0.002), and both plant and bee assemblages in restorations were intermediate between those of old fields and remnant prairies. Restorations exhibited high bee beta diversity, i.e., restored sites' bee assemblages were taxonomically and functionally differentiated from each other. This pattern was strong in younger restorations (< 20 years old), but absent from older restorations (> 20 years), suggesting restored prairie bee communities become more similar to one another and more similar to remnant prairie bee communities over time with the arrival of more species and functional groups of bees. Our results indicate that old fields, restorations, and remnants provide habitat for diverse and abundant bee communities, but continued restoration of old fields will help support and conserve bee communities more similar to reference bee communities characteristic of remnant prairies.
The trajectories of vegetative structure and soil microbial function diverged across a fire chronosequence of the boreal forests in Northeast China
<p>The role of boreal forest to ameliorate the effect of global climate change largely depends on the regeneration of postfire forests in northeast China. The postfire recovery of boreal forest can be evaluated by the aboveground vegetative structure and soil microbial function. In present study, a 50-year fire chronosequence was established, and the biomass of forbs, shrub and woody plant was separately weighted to assess their contribution to the whole community with the year since fire (YSF). Simultaneously, soil biophysical properties were measured for stands in different time period after fire. Soil microbial functions, i.e., growth efficiency (GE) and carbon use efficiency (CUE), were calculated basing on ecoenzymatic and soil nutrient stoichiometry. In terms of vegetative structure, forbs' proportion decreased from 75% to 1.5%, but the proportion of woody plant increased from 0.04% to 70% across this fire chronosequence. In contrast, soil microbial function reached the highest value in 15 YSF and then began to decrease. As an important variable, soil metal content, particularly the calcium content, showed a positive correlation with woody plant biomass and a negative with soil microbial function. Furthermore, soil metal content was significantly increased in the late stage of this fire chronosequence. Overall, the present work highlighted that the time period of 15 YSF and 31 YSF was a hallmark stage for aboveground vegetative structure and soil microbial function to change in different trends, and the calcium content may partly account for these two divergent trajectories.</p>
Data set of 1) plant abundance in the herb layer and 2) Shrub and tree composition and structure following forest management along a chronosequence
<p>In each site (1200 m²), three circular plots (400 m²) were established (total of 198 plots). Data presented here for 1) plant of the herb layer and 2) shrub and tree are grouped by site (addition of three plots). </p> <p>In the herb layer, total plant species identity and abundance (percentage cover) were sampled in each plot using eight circular micro-plots of 4 m². Data were collected in 2016 and 2017, between June and August. To minimize seasonal variability and allow detection of early spring species, plants (identity and abundance) in the herb layer were measured twice (once in June to early-July, and once in late-July to August).</p> <p>For tree, in each plot, species identity, diameter at breast height (DBH, 1.3 m) and locations of each tree > 9.1 cm DBH were determined. In each plot, species identity and DBH of shrubs and small trees (DBH range: 1.1 to 9.1 cm) were measured in three circular micro-plots of 25 m². Data that were related to the shrub-canopy layer included all trees and shrubs with DBH > 1.1 cm. Here, in each site, forest composition and structure is represented by different combinations of DBH classes (1.1-4 cm, 4-9.1 cm, 9.1-20 cm, 20-35 cm, >35 cm) and species.</p> <p>Plant community composition and abundance were assessed in unmanaged forests (sites of old-growth forest > 100 years, with dominant and co-dominant trees older than 200 years, and no obvious sign of past harvesting), and in even-aged and uneven-aged managed forests along a chronosequence (< 5 years, 15 years, 30 years after forest harvesting).</p>
Data from: Impact of a hurricane on the herpetofaunal assemblages of a successional chronosequence in a tropical dry forest
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Data from: Post-fire changes in forest carbon storage over a 300-year chronosequence of Pinus contorta-dominated forests
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Collapse of dispersal trait diversity across a long-term chronosequence reveals a strong negative impact of frugivore extinctions on forest resilience
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Data from: Bee communities along a prairie restoration chronosequence: similar abundance and diversity, distinct composition
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Data from: Foliar nutrient concentrations and resorption efficiency in plants of contrasting nutrient-acquisition strategies along a 2-million year dune chronosequence
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Data from: Reproductive traits as predictors of assembly chronosequence patterns in epiphyllous bryophyte metacommunities
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Data from: Ecosystem carbon density and allocation across a chronosequence of longleaf pine forests
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The trajectories of vegetative structure and soil microbial function diverged across a fire chronosequence of the boreal forests in Northeast China
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