المؤلفون: Ury EA; Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708, USA., Yang X; Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia, 22904, USA., Wright JP; Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708, USA., Bernhardt ES; Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708, USA.

المصدر: Ecological applications : a publication of the Ecological Society of America [Ecol Appl] 2021 Jul; Vol. 31 (5), pp. e02339. Date of Electronic Publication: 2021 Apr 29.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Ecological Society of America Country of Publication: United States NLM ID: 9889808 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1051-0761 (Print) Linking ISSN: 10510761 NLM ISO Abbreviation: Ecol Appl Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Sea Level Rise*, Climate Change ; Conservation of Natural Resources ; Forests ; Wetlands

مستخلص: Climate change is driving ecological shifts in coastal regions of the world, where low topographic relief makes ecosystems particularly vulnerable to sea-level rise, salinization, storm surge, and other effects of global climate change. The consequences of rising water tables and salinity can penetrate well inland, and lead to particularly dramatic changes in freshwater forested wetlands dominated by tree species with low salt tolerance. The resulting loss of coastal forests could have significant implications to the coastal carbon cycle. We quantified the rates of vegetation change including land loss, forest loss, and shrubland expansion in North Carolina's largest coastal wildlife refuge over 35 yr. Despite its protected status, and in the absence of any active forest management, 32% (31,600 hectares) of the refuge area has changed landcover classification during the study period. A total of 1,151 hectares of land was lost to the sea and ~19,300 hectares of coastal forest habitat was converted to shrubland or marsh habitat. As much as 11% of all forested cover in the refuge transitioned to a unique land cover type-"ghost forest"-characterized by standing dead trees and fallen tree trunks. The formation of this ghost forest transition state peaked prominently between 2011 and 2012, following Hurricane Irene and a 5-yr drought, with 4,500 ± 990 hectares of ghost forest forming during that year alone. This is the first attempt to map and quantify coastal ghost forests using remote sensing. Forest losses were greatest in the eastern portion of the refuge closest to the Croatan and Pamlico Sounds, but also occurred much further inland in low-elevation areas and alongside major canals. These unprecedented rates of deforestation and land cover change due to climate change may become the status quo for coastal regions worldwide, with implications for wetland function, wildlife habitat, and global carbon cycling.
(© 2021 by the Ecological Society of America.)

المؤلفون: Mitchell RM; School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ, USA., Ames GM; Department of Biology, Duke University, Durham, NC, USA., Wright JP; Department of Biology, Duke University, Durham, NC, USA.

المصدر: Annals of botany [Ann Bot] 2021 Mar 24; Vol. 127 (4), pp. 543-552.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't

بيانات الدورية: Publisher: Oxford University Press Country of Publication: England NLM ID: 0372347 Publication Model: Print Cited Medium: Internet ISSN: 1095-8290 (Electronic) Linking ISSN: 03057364 NLM ISO Abbreviation: Ann Bot Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Fires*, Ecology ; Phenotype ; Plant Leaves

مستخلص: Background and Aims: Understanding impacts of altered disturbance regimes on community structure and function is a key goal for community ecology. Functional traits link species composition to ecosystem functioning. Changes in the distribution of functional traits at community scales in response to disturbance can be driven not only by shifts in species composition, but also by shifts in intraspecific trait values. Understanding the relative importance of these two processes has important implications for predicting community responses to altered disturbance regimes.
Methods: We experimentally manipulated fire return intervals in replicated blocks of a fire-adapted, longleaf pine (Pinus palustris) ecosystem in North Carolina, USA and measured specific leaf area (SLA), leaf dry matter content (LDMC) and compositional responses along a lowland to upland gradient over a 4 year period. Plots were burned between zero and four times. Using a trait-based approach, we simulate hypothetical scenarios which allow species presence, abundance or trait values to vary over time and compare these with observed traits to understand the relative contributions of each of these three processes to observed trait patterns at the study site. We addressed the following questions. (1) How do changes in the fire regime affect community composition, structure and community-level trait responses? (2) Are these effects consistent across a gradient of fire intensity? (3) What are the relative contributions of species turnover, changes in abundance and changes in intraspecific trait values to observed changes in community-weighted mean (CWM) traits in response to altered fire regime?
Key Results: We found strong evidence that altered fire return interval impacted understorey plant communities. The number of fires a plot experienced significantly affected the magnitude of its compositional change and shifted the ecotone boundary separating shrub-dominated lowland areas from grass-dominated upland areas, with suppression sites (0 burns) experiencing an upland shift and annual burn sites a lowland shift. We found significant effects of burn regimes on the CWM of SLA, and that observed shifts in both SLA and LDMC were driven primarily by intraspecific changes in trait values.
Conclusions: In a fire-adapted ecosystem, increased fire frequency altered community composition and structure of the ecosystem through changes in the position of the shrub line. We also found that plant traits responded directionally to increased fire frequency, with SLA decreasing in response to fire frequency across the environmental gradient. For both SLA and LDMC, nearly all of the observed changes in CWM traits were driven by intraspecific variation.
(© The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

المؤلفون: Ames GM; Department of Plant & Microbial Biology, North Carolina State University, Raleigh, North Carolina, 27695, USA.; Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708, USA., Wall WA; U.S. Army Engineer Research and Development Center, Construction Engineering Research Laboratory, Champaign, Illinois, 61826-9005, USA., Hohmann MG; U.S. Army Engineer Research and Development Center, Construction Engineering Research Laboratory, Champaign, Illinois, 61826-9005, USA., Wright JP; Department of Biology, Duke University, Box 90338, Durham, North Carolina, 27708, USA.

المصدر: Ecological applications : a publication of the Ecological Society of America [Ecol Appl] 2020 Jun; Vol. 30 (4), pp. e02087. Date of Electronic Publication: 2020 Feb 27.

نوع المنشور: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Ecological Society of America Country of Publication: United States NLM ID: 9889808 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1051-0761 (Print) Linking ISSN: 10510761 NLM ISO Abbreviation: Ecol Appl Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Plants*, Humans

مستخلص: Rare species reintroductions are an increasingly common conservation strategy, but often result in poor survival of reintroduced individuals. Reintroduction sites are chosen primarily based on historical occupancy and/or abiotic properties of the site, with much less consideration given to properties of the larger biotic community. However, ecological niche theory suggests that the ability to coexist with other species is determined in part by the degree of functional similarity between species. The degree to which functional similarity affects the survival of reintroduced plants is poorly understood, but has important implications for the allocation of limited conservation resources. We collected a suite of abiotic, biotic, and functional trait variables centered on outplanted individuals from four reintroduced rare plant species and used logistic regression and model selection to assess their influence on individual survival. We show that higher functional similarity between reintroduced individuals and the local community, measured by differences between their multivariate functional traits and the community-weighted mean traits of their immediate neighbors, increases survival and is a stronger predictor of survival than local variation in abiotic factors, suggesting that the functional composition of the biotic community should be incorporated into site selection to improve reintroduction success.
(© 2020 by the Ecological Society of America.)

المؤلفون: Ury EA; Duke University Department of Biology, Durham, NC, USA., Anderson SM; Duke University Department of Biology, Durham, NC, USA.; North Carolina State University Department of Forestry and Environmental Resources, Raleigh, NC, USA., Peet RK; University of North Carolina at Chapel Hill Department of Biology, Chapel Hill, NC, USA., Bernhardt ES; Duke University Department of Biology, Durham, NC, USA., Wright JP; Duke University Department of Biology, Durham, NC, USA.

المصدر: Annals of botany [Ann Bot] 2020 Feb 03; Vol. 125 (2), pp. 255-264.

نوع المنشور: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Oxford University Press Country of Publication: England NLM ID: 0372347 Publication Model: Print Cited Medium: Internet ISSN: 1095-8290 (Electronic) Linking ISSN: 03057364 NLM ISO Abbreviation: Ann Bot Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Trees*, North Carolina ; Salinity ; Soil ; Wetlands

مستخلص: Background and Aims: Coastal plant communities globally are highly vulnerable to future sea-level rise and storm damage, but the extent to which these habitats are affected by the various environmental perturbations associated with chronic salinization remains unclear. In this study, we examine the relationship between North Carolina wetland tree community composition and basal area change and indicators of salinization such as soil salt ion content and elevation.
Methods: We surveyed 34 forest plots in forested, freshwater wetlands across the Albemarle-Pamlico Peninsula. A subset of our study sites had been sampled during the previous decade as part of the Carolina Vegetation Survey, enabling us to investigate the environmental effects on current community structure, and community change over time.
Key Results: Multi-variate (ordination) analysis and linear regression models of tree community composition revealed that elevation and soil salt content were correlated with changes in total site tree basal area. Shifts in tree community composition were, however, only weakly correlated with indicators of salinization, specifically elevation, soil sulphate and sodium, but not chloride. While the majority of plots experienced gains in basal area over the past decade, consistent with secondary succession, sites with high soil salt content or low elevation experienced basal area (biomass) loss during the same period.
Conclusions: The key factors associated with chronic saltwater intrusion (soil ion content) likely explain recent changes in tree biomass, and potential shifts in community composition in low-elevation sites along the North Carolina coast. Not only is it probable that other coastal forest ecosystems worldwide will experience similar stressors and shifts in community biomass and structure as sea levels rise, but the ability of these habitats to deliver key ecosystem services like carbon sequestration and flood defence will be compromised as a result.
(© The Author(s) 2019. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

المؤلفون: Mitchell RM; Department of Biology, Duke University, Box 90338, Durham, NC, 27708, USA. rachel.mitchell@nau.edu.; School of Earth Sciences and Environmental Sustainability, Northern Arizona University, 525 S. Beaver St, Box 5694, Flagstaff, AZ, 86011, USA. rachel.mitchell@nau.edu., Wright JP; Department of Biology, Duke University, Box 90338, Durham, NC, 27708, USA., Ames GM; Department of Biology, Duke University, Box 90338, Durham, NC, 27708, USA.

المصدر: Oecologia [Oecologia] 2018 Mar; Vol. 186 (3), pp. 719-729. Date of Electronic Publication: 2017 Dec 13.

نوع المنشور: Journal Article

بيانات الدورية: Publisher: Springer Country of Publication: Germany NLM ID: 0150372 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1432-1939 (Electronic) Linking ISSN: 00298549 NLM ISO Abbreviation: Oecologia Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Plants*, Phenotype

مستخلص: Plant trait expression is shaped by filters, which can alter trait means and variances, theoretically driving species toward an "optimum" trait value for a set of environmental conditions. Recent research has highlighted the ubiquity of intraspecific variation in functional traits, which can cause plants to diverge from a hypothesized "optimum". We examined whether species occurring in "core" habitats (where they occur frequently, abundantly, and consistently) express traits that are nearer to "optimum", as captured by the community-weighted mean (CWM). We also asked whether trait variance showed signs of environmental filtering. We used cluster analysis to group plots based on environmental factors along a wet-to-dry ecotone. We used indicator species analysis to identify species with strong associations within each cluster. Trait means and variances were compared, and evidence of variance filtering was tested using a null-model approach. Trait means and trait variances respond to local-scale environmental filtering and species in core habitats were not necessarily nearer to the CWM than in other habitats. Intraspecific trait variability shows a strong signal of filtering, as variability was reduced for nearly all species and all traits compared to estimates of variability generated in the absence of environmental filtering. Our results provide strong evidence that species traits are not necessarily near "optimum" trait values in core habitats, and that trait distributions within species are strongly shaped by the environment. Future analyses should account for this divergence when calculating metrics of functional diversity, and extrapolating to ecosystem function.

المؤلفون: Reese AT; Department of Biology, Duke University, Durham, NC, United States of America., Ames GM; Department of Biology, Duke University, Durham, NC, United States of America., Wright JP; Department of Biology, Duke University, Durham, NC, United States of America.

المصدر: PloS one [PLoS One] 2016 Dec 09; Vol. 11 (12), pp. e0166714. Date of Electronic Publication: 2016 Dec 09 (Print Publication: 2016).

نوع المنشور: Journal Article

بيانات الدورية: Publisher: Public Library of Science Country of Publication: United States NLM ID: 101285081 Publication Model: eCollection Cited Medium: Internet ISSN: 1932-6203 (Electronic) Linking ISSN: 19326203 NLM ISO Abbreviation: PLoS One Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem*, Herbivory/*physiology , Plant Leaves/*physiology , Plants/*metabolism, Animals ; Biomass ; Computer Simulation ; Models, Theoretical ; Plant Leaves/metabolism ; Plants/classification ; Poaceae/classification ; Poaceae/metabolism ; Poaceae/physiology ; Species Specificity ; Trees/classification ; Trees/metabolism ; Trees/physiology

مستخلص: The effects of herbivory can shape plant communities and evolution. However, the many forms of herbivory costs and the wide variation in herbivory pressure, including across latitudinal gradients, can make predicting the effects of herbivory on different plant species difficult. Functional trait approaches may aid in contextualizing and standardizing the assessment of herbivory impacts. Here we assessed the response of 26 old-field plant species to simulated defoliation in a greenhouse setting by measuring whole plant and leaf level traits in control and treated individuals. Simulated defoliation had no significant effects on any plant traits measured. However, the baseline leaf level traits of healthy plants consistently predicted the log response ratio for these species whole plant response to defoliation. The latitudinal mid-point of species' distributions was also significantly correlated with aboveground biomass and total leaf area responses, with plants with a more northern distribution being more negatively impacted by treatment. These results indicate that even in the absence of significant overall impacts, functional traits may aid in predicting variability in plant responses to defoliation and in identifying the underlying limitations driving those responses.
Competing Interests: The authors have declared that no competing interests exist.

المؤلفون: Wright JP; Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA Department of Biodiversity Research and Systematic Botany, Universität Potsdam, Maulbeerallee 2a, Potsdam, Germany jw67@duke.edu., Ames GM; Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA., Mitchell RM; Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA.

المصدر: Philosophical transactions of the Royal Society of London. Series B, Biological sciences [Philos Trans R Soc Lond B Biol Sci] 2016 May 19; Vol. 371 (1694).

نوع المنشور: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Royal Society Country of Publication: England NLM ID: 7503623 Publication Model: Print Cited Medium: Internet ISSN: 1471-2970 (Electronic) Linking ISSN: 09628436 NLM ISO Abbreviation: Philos Trans R Soc Lond B Biol Sci Subsets: MEDLINE

مواضيع طبية MeSH: Adaptation, Biological* , Ecosystem* , Phenotype*, Biodiversity ; Environment ; Forests ; Models, Biological ; North Carolina ; Population Dynamics

مستخلص: The importance of intraspecific trait variability for community dynamics and ecosystem functioning has been underappreciated. There are theoretical reasons for predicting that species that differ in intraspecific trait variability will also differ in their effects on ecosystem functioning, particularly in variable environments. We discuss whether species with greater trait variability are likely to exhibit greater temporal stability in their population dynamics, and under which conditions this might lead to stability in ecosystem functioning. Resolving this requires us to consider several questions. First, are species with high levels of variation for one trait equally variable in others? In particular, is variability in response and effects traits typically correlated? Second, what is the relative contribution of local adaptation and phenotypic plasticity to trait variability? If local adaptation dominates, then stability in function requires one of two conditions: (i) individuals of appropriate phenotypes present in the environment at high enough frequencies to allow for populations to respond rapidly to the changing environment, and (ii) high levels of dispersal and gene flow. While we currently lack sufficient information on the causes and distribution of variability in functional traits, filling in these key data gaps should increase our ability to predict how changing biodiversity will alter ecosystem functioning.
(© 2016 The Author(s).)

المؤلفون: Colman BP; Department of Biology, Duke University, Durham, NC, USA. benjamin.colman@duke.edu, Arnaout CL, Anciaux S, Gunsch CK, Hochella MF Jr, Kim B, Lowry GV, McGill BM, Reinsch BC, Richardson CJ, Unrine JM, Wright JP, Yin L, Bernhardt ES

المصدر: PloS one [PLoS One] 2013; Vol. 8 (2), pp. e57189. Date of Electronic Publication: 2013 Feb 27.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Public Library of Science Country of Publication: United States NLM ID: 101285081 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1932-6203 (Electronic) Linking ISSN: 19326203 NLM ISO Abbreviation: PLoS One Subsets: MEDLINE

مواضيع طبية MeSH: Ecosystem* , Metal Nanoparticles*, Silver/*chemistry, Biomass ; Microscopy, Electron, Transmission ; Plants/metabolism ; Silver Nitrate/administration & dosage

مستخلص: A large fraction of engineered nanomaterials in consumer and commercial products will reach natural ecosystems. To date, research on the biological impacts of environmental nanomaterial exposures has largely focused on high-concentration exposures in mechanistic lab studies with single strains of model organisms. These results are difficult to extrapolate to ecosystems, where exposures will likely be at low-concentrations and which are inhabited by a diversity of organisms. Here we show adverse responses of plants and microorganisms in a replicated long-term terrestrial mesocosm field experiment following a single low dose of silver nanoparticles (0.14 mg Ag kg(-1) soil) applied via a likely route of exposure, sewage biosolid application. While total aboveground plant biomass did not differ between treatments receiving biosolids, one plant species, Microstegium vimeneum, had 32 % less biomass in the Slurry+AgNP treatment relative to the Slurry only treatment. Microorganisms were also affected by AgNP treatment, which gave a significantly different community composition of bacteria in the Slurry+AgNPs as opposed to the Slurry treatment one day after addition as analyzed by T-RFLP analysis of 16S-rRNA genes. After eight days, N2O flux was 4.5 fold higher in the Slurry+AgNPs treatment than the Slurry treatment. After fifty days, community composition and N2O flux of the Slurry+AgNPs treatment converged with the Slurry. However, the soil microbial extracellular enzymes leucine amino peptidase and phosphatase had 52 and 27% lower activities, respectively, while microbial biomass was 35% lower than the Slurry. We also show that the magnitude of these responses was in all cases as large as or larger than the positive control, AgNO3, added at 4-fold the Ag concentration of the silver nanoparticles.

المؤلفون: Fridley JD; Department of Biology, Syracuse University, 107 College Place, Syracuse, NY, 13244, USA. fridley@syr.edu, Wright JP

المصدر: Oecologia [Oecologia] 2012 Apr; Vol. 168 (4), pp. 1069-77. Date of Electronic Publication: 2011 Oct 19.

نوع المنشور: Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Springer Country of Publication: Germany NLM ID: 0150372 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1432-1939 (Electronic) Linking ISSN: 00298549 NLM ISO Abbreviation: Oecologia Subsets: MEDLINE

مواضيع طبية MeSH: Climate* , Ecosystem* , Plant Development*, Soil/*analysis, Analysis of Variance ; Mid-Atlantic Region ; Population Dynamics ; Regression Analysis ; Southeastern United States ; Species Specificity

مستخلص: Climate change is widely expected to induce large shifts in the geographic distribution of plant communities, but early successional ecosystems may be less sensitive to broad-scale climatic trends because they are driven by interactions between species that are only indirectly related to temperature and rainfall. Building on a biogeographic analysis of secondary succession rates across the Eastern Deciduous Forest (EDF) of North America, we describe an experimental study designed to quantify the relative extent to which climate, soil properties, and geographic species pools drive variation in woody colonization rates of old fields across the EDF. Using a network of five sites of varying soil fertility spanning a latitudinal gradient from central New York to northern Florida, we added seeds of nine woody pioneer species to recently tilled old fields and monitored first-year growth and survivorship. Results suggest seedlings of southern woody pioneer species are better able to quickly establish in fields after abandonment, regardless of climate regime. Sites of lower soil fertility also exhibited faster rates of seedling growth, likely due to the slower development of the successional herbaceous community. We suggest that climate plays a relatively minor role in community dynamics at the onset of secondary succession, and that site edaphic conditions are a stronger determinant of the rate at which ecosystems develop to a woody-dominated state. More experimental research is necessary to determine the nature of the herbaceous-woody competitive interface and its sensitivity to environmental conditions.

المؤلفون: Adler PB; Department of Wildland Resources and the Ecology Center, Utah State University, 5230 Old Main, Logan, UT 84322, USA. peter.adler@usu.edu, Seabloom EW, Borer ET, Hillebrand H, Hautier Y, Hector A, Harpole WS, O'Halloran LR, Grace JB, Anderson TM, Bakker JD, Biederman LA, Brown CS, Buckley YM, Calabrese LB, Chu CJ, Cleland EE, Collins SL, Cottingham KL, Crawley MJ, Damschen EI, Davies KF, DeCrappeo NM, Fay PA, Firn J, Frater P, Gasarch EI, Gruner DS, Hagenah N, Hille Ris Lambers J, Humphries H, Jin VL, Kay AD, Kirkman KP, Klein JA, Knops JM, La Pierre KJ, Lambrinos JG, Li W, MacDougall AS, McCulley RL, Melbourne BA, Mitchell CE, Moore JL, Morgan JW, Mortensen B, Orrock JL, Prober SM, Pyke DA, Risch AC, Schuetz M, Smith MD, Stevens CJ, Sullivan LL, Wang G, Wragg PD, Wright JP, Yang LH

المصدر: Science (New York, N.Y.) [Science] 2011 Sep 23; Vol. 333 (6050), pp. 1750-3.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: American Association for the Advancement of Science Country of Publication: United States NLM ID: 0404511 Publication Model: Print Cited Medium: Internet ISSN: 1095-9203 (Electronic) Linking ISSN: 00368075 NLM ISO Abbreviation: Science Subsets: MEDLINE

مواضيع طبية MeSH: Biodiversity* , Biomass* , Ecosystem* , Plants*, Africa ; Australia ; China ; Europe ; Models, Biological ; Models, Statistical ; North America ; Plant Development ; Plant Physiological Phenomena ; Regression Analysis

مستخلص: For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.