Evenness mediates the global relationship between forest productivity and richness

1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions

Evenness mediates the global relationship between forest productivity and richness

Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions. © 2023 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society

FOURIER TRANSFORM MICROWAVE SPECTROSCOPY OF SCS (X2Σ^{2}\Sigma), YS (X2Σ^{2}\Sigma) AND VS (X4Σ^{4}\Sigma)

Author Institution: Department of Chemistry and Steward Observatory, University of Arizona, Tucson, AZ 85721Pure rotational spectra of three transition-metal monosulfides, ScS, YS, and VS, have been recorded using Fourier transform microwave spectroscopy (FTWM) in the range 10-40 GHz. These molecules are all free radicals and have been synthesized in a mixture of H$_{2}$S gas with metal vapor, obtained by laser ablation of a metal rod. In the case of ScS and VS, a discharge was necessary to successfully produce the molecules. For YS, the N=1$\longrightarrow$0, 2$\longrightarrow$1, 3$\longrightarrow$2 and 4$\longrightarrow$3 rotational transitions have been recorded. For ScS and VS, the N=1$\longrightarrow$0, N=2$\longrightarrow$1 and N=3$\longrightarrow$2 have been obtained. Vanadium, scandium and yttrium hyperfine structures were resolved for these species. Rotational, fine structure and hyperfine coupling constants have been determined for all three radicals. This works completes the high-resolution pure rotational measurements of 3d transition-metal monosulfides, and provides the most accurate values of the hyperfine parameters for these molecules to date. Bond lengths and spectroscopic parameters will be presented

Utilisation rationnelle de fertilisants organiques pour la production de macroinvertébrés benthiques d'eau douce en pisciculture

Rational utilization of organic fertilizers for freshwater benthic macroinvertebrate production in fish farming. Description of the subject. This study aims to determine optimal conditions of rabbit manure utilization in freshwater benthic macroinvertebrate production in order to produce fish at low cost. Objectives. To determine the optimal dose of rabbit manure to be used for freshwater macroinvertebrate production. Method. Six treatments, including one control, received respectively 0%, 10%, 25%, 50%, 75% and 100% of rabbit manure compared to the substrate total volume. Cultures were carried out in buckets, which received 10 dm3 of substrate, 16 dm3 of groundwater and 4 dm3 of fishpond water. The initial seeding density was 6 ind·dm-2 of odonates, 6 ind·dm-2 of annelids or (3 ind·dm-3, for 0.5 m depth), 8 ind·dm-2 of chironomids or (4 ind·dm-3) and 10 ind·dm-2 of mollusks or (5 ind·dm-3). Physicochemical and biological parameters were measured during the 63 days of the experiment. Results. The highest densities of benthic macroinvertebrates were obtained within treatment T2, with 192 ± 1.20 ind·dm-2 of chironomids, 52 ± 0.8 ind·dm-2 of mollusks, 6 ± 0.33 ind·dm-2 of odonates and 6 ± 0.33 ind·dm-2 of annelids. Considering the depth of our experimental buckets (0.5 m), these highest densities also corresponded to respectively: 96 ± 1.20 ind·dm-3 of chironomids, 26 ± 0.8 ind·dm-3 of mollusks, 3 ± 0.33 ind·dm-3 of odonates and 2 ± 0.33 ind·dm-3 of annelids). The highest biomass of chironomids and mollusks was obtained within treatment T2, with respectively 728.1 ± 2.23 mg dry matter·dm-2 and 699.98 ± 22.49 mg dry matter·dm-2 (i.e. respectively 364.05 ± 2.23 mg dry matter·dm-3 and 349.99 ± 22.49 mg dry matter·dm-3). Conclusions. Considering these results, treatment T2 with 140 g dry matter of rabbit manure·dm-2 of substrate (i.e. 75 g dry matter of rabbit manure·dm-3 of substrate) could constitute the optimal dose that could be recommended for the optimal production of freshwater benthic macroinvertebrates

Examining transition metal hydrosulfides: The pure rotational spectrum of ZnSH (X̃2A′)

The pure rotational spectrum of the ZnSH ((X) over tilde (2)A') radical has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) methods across the frequency range 18-468 GHz. This work is the first gas-phase detection of ZnSH by any spectroscopic technique. Spectra of the (ZnSH)-Zn-66, (ZnSH)-Zn-68, and (ZnSD)-Zn-64 isotopologues were also recorded. In the mm-wave study, ZnSH was synthesized in a DC discharge by the reaction of zinc vapor, generated by a Broidatype oven, with H2S; for FTMW measurements, the radical was made in a supersonic jet expansion by the same reactants but utilizing a discharge-assisted laser ablation source. Between 7 and 9 rotational transitions were recorded for each isotopologue. Asymmetry components with K-a = 0 through 6 were typically measured in the mm-wave region, each split into spin-rotation doublets. In the FTMW spectra, hyperfine interactions were also resolved, arising from the hydrogen or deuterium nuclear spins of I = 1/2 or I = 1, respectively. The data were analyzed using an asymmetric top Hamiltonian, and rotational, spin-rotation, and magnetic hyperfine parameters were determined for ZnSH, as well as the quadrupole coupling constant for ZnSD. The observed spectra clearly indicate that ZnSH has a bent geometry. The r(m)((1)) structure was determined to be r(Zn-S) = 2.213(5) angstrom, r(S-H) = 1.351(3) angstrom, and theta(Zn-S-H) = 90.6(1)degrees, suggesting that the bonding occurs primarily through sulfur p orbitals, analogous to H2S. The hyperfine constants indicate that the unpaired electron in ZnSH primarily resides on the zinc nucleus. Published by AIP Publishing.NSF [CHE-1565765]12 month embargo; Published online: 20 October 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]