Large‐diameter, tall‐stature, and big‐crown trees are the main stand structures of forests, generally contributing a large fraction of aboveground biomass, and hence play an important role in climate ...change mitigation strategies. Here, we hypothesized that the effects of large‐diameter, tall‐stature, and big‐crown trees overrule the effects of species richness and remaining trees attributes on aboveground biomass in tropical forests (i.e., we term the “big‐sized trees hypothesis”). Specifically, we assessed the importance of: (a) the “top 1% big‐sized trees effect” relative to species richness; (b) the “99% remaining trees effect” relative to species richness; and (c) the “top 1% big‐sized trees effect” relative to the “99% remaining trees effect” and species richness on aboveground biomass. Using environmental factor and forest inventory datasets from 712 tropical forest plots in Hainan Island of southern China, we tested several structural equation models for disentangling the relative effects of big‐sized trees, remaining trees attributes, and species richness on aboveground biomass, while considering for the full (indirect effects only) and partial (direct and indirect effects) mediation effects of climatic and soil conditions, as well as interactions between species richness and trees attributes. We found that top 1% big‐sized trees attributes strongly increased aboveground biomass (i.e., explained 55%–70% of the accounted variation) compared to species richness (2%–18%) and 99% remaining trees attributes (6%–10%). In addition, species richness increased aboveground biomass indirectly via increasing big‐sized trees but via decreasing remaining trees. Hence, we show that the “big‐sized trees effect” overrides the effects of remaining trees attributes and species richness on aboveground biomass in tropical forests. This study also indicates that big‐sized trees may be more susceptible to atmospheric drought. We argue that the effects of big‐sized trees on species richness and aboveground biomass should be tested for better understanding of the ecological mechanisms underlying forest functioning.
Large‐diameter, tall‐stature and big‐crown trees are the main stand structures of forests, generally contributing a large fraction of aboveground biomass, and hence, play an important role in climate change mitigation strategies. We show that the “big‐sized trees effect” overrides the effects of remaining trees attributes and species richness on aboveground biomass in tropical forests. This study also indicates that big‐sized trees may be more susceptible to atmospheric drought. We argue that the effects of big‐sized trees on species richness and aboveground biomass should be tested for better understanding of the ecological mechanisms underlying forest functioning.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Species and stand structural complexity increased with climatic water availability.•Stand structural complexity, but not species diversity, increased with soil fertility.•Climate and ...soils did not affect aboveground biomass directly but did affect indirectly.•Maintaining high species diversity can promote stand structural complexity.•Maintaining high stand structural complexity can enhance aboveground biomass.
Theoretical and empirical studies have suggested that climate and soils are the main drivers of biodiversity, stand structure and aboveground biomass in natural forests. Yet, the direct effects of climate and soils on aboveground biomass versus the indirect effects mediated by species diversity and stand structural complexity remain unclear in forest ecosystems across large-scale ecological gradients. Here, we hypothesized that (1) climate and soils would influence aboveground biomass through strong indirect effects; (2) stand structural complexity rather than species diversity would strongly mediate the response of aboveground biomass to climate and soils; and (3) species diversity and stand structural complexity would promote each other under the niche differentiation and facilitation effects, and that stand structural complexity would have positive effects on aboveground biomass across large-scale ecological gradients. To test these hypotheses, we quantified climatic water availability, soil total exchangeable bases, species diversity, stand structural complexity including tree DBH (diameter at breast height) diversity and height diversity, and aboveground biomass across 907 plots in tropical forests of Hainan Island, Southern China. We tested 126 structural equation models to examine the direct and indirect effects of climate and soils on aboveground biomass via species diversity and stand structural complexity. Climatic water availability and soil fertility did not affect aboveground biomass directly but did affect indirectly via increasing stand structural complexity rather than species diversity. Species diversity and stand structural complexity promoted each other, and both increased with increasing climatic water availability. Stand structural complexity increased aboveground biomass directly, whereas species diversity increased it indirectly via increasing stand structural complexity. The total effects of climatic water availability, soil fertility, stand structural complexity and species diversity on aboveground biomass were significantly positive. This study shows that climatic water availability exerts a strong direct effect on stand structural complexity, indicating that any decrease in climatic water availability (i.e. increasing atmospheric drought) may directly diminish stand structural complexity and hence indirectly reduce aboveground biomass and carbon storage. This study suggests that maintaining high stand structural complexity can enhance aboveground biomass under favourable climate and soils while maintaining the benefits of species diversity on stand structural complexity for better ecosystem services such as carbon storage.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Climatic water availability is a key spatial driver of species distribution patterns in natural forests. Yet, we do not fully understand the importance of climatic water availability relative to ...temperature, and climate relative to edaphic factors for multiple biotic attributes across large-scale elevational gradients in natural forests. Here, we modelled multiple abiotic factors (elevation, climate, and edaphic factors) with each of the taxonomic-related (Shannon's species diversity, species richness, species evenness, and Simpson's dominance) and tree size or biomass-related (individual tree size variation, functional dominance and divergence, and aboveground biomass) biotic attributes through boosted regression trees (BRT) models, using biophysical data from 247,691 trees across 907 plots in tropical forests in Hainan Island of Southern China. The tested multiple abiotic factors explained simultaneously 43, 50, 36, 45, 37, 50, 17 and 46%, respectively, of the variations in Shannon's species diversity, species richness, species evenness, Simpson's dominance, individual tree size variation, functional dominance, functional divergence and aboveground biomass. After the large influences of elevation (i.e. 30.43 to 62.83%), climatic water availability accounted for most (i.e. 15.52 to 25.30%) of the variations in all biotic attributes. Beside the increasing trend with elevational gradients, taxonomic diversity increased strongly with climatic water availability whereas tree size or biomass-related biotic attributes showed strong decreasing and increasing trends. Tree size or biomass-related rather than taxonomic-related biotic attributes also decreased apparently with mean annual temperature. Most of the biotic attributes monotonically increased with soil fertility but decreased with soil pH, whereas soil textural properties had mostly negligible influences. This study strongly reveals that future climate change (i.e. a decrease in climatic water availability with an increase in mean annual temperature) is thus likely to have a substantial influence on the biotic attributes in the studied tropical forests across large-scale elevational gradients.
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•Climatic water availability was a main spatial driver of biotic factors.•Taxonomic diversity increased with climatic water availability.•Biotic factors increased monotonically with soil fertility but decreased with soil pH.•Tree size or biomass-related biotic attributes are sensitive to future drought and heat.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aim and hypothesis
This study aims to disentangle the direct and indirect roles of space, climate, edaphic, and biodiversity effects on aboveground biomass in natural tropical forests, thereby ...evaluating the relative effects and contribution of abiotic and biotic factors on aboveground biomass. We hypothesized that the space effect drives the longitudinal, latitudinal, and elevational patterns in climatic and edaphic factors, thereby directly and indirectly determining the relationships between biodiversity and aboveground biomass in natural tropical forests.
Methods
We used structural equation modelling for linking spatial, climatic, edaphic, and biotic factors of aboveground biomass, using data from 247,691 trees across 907 tropical forest plots (total sampling area of 145.23 ha) of Hainan Island in Southern China.
Results
Aboveground biomass increased directly with functional dominance, individual tree size inequality, and climatic water availability but decreased directly with space and edaphic effects. However, space effect increased aboveground biomass indirectly via simultaneously differential direct changes (positive, negative, and non‐significant) in climatic, edaphic, and biotic factors. As such, indirect effects of mean annual temperature and climatic water availability decreased aboveground biomass through differential direct changes in biotic factors, but opposite was true for soil fertility.
Conclusions
We argue that, despite the high relative contribution of biodiversity to aboveground biomass, the direct and indirect roles of space, climatic, and edaphic effects are also important for explaining biotic factors and aboveground biomass under the predictions of several abiotic‐based hypotheses. Hence, conserving biodiversity across space is important for forest management and land development under climate change.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Herein, two novel Evans-Showell-type polyoxometalate (POM)-based metal-organic complexes, namely, {Cu(L)(H2O)3Cu(L)0.5(H2O)Cu(L)0.5(H2O)4Co2Mo10H4O38}·5H2O (1) and ...(H2L)0.52{Zn(L)0.5(H2O)42Co2Mo10H4O38}·2H2O (2) (L = N,N'-bis(3-pyridinecarboxamide)-piperazine), were hydrothermally synthesized using a semi-rigid bis-pyridyl-bis-amide ligand and structurally characterized via single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). The single-crystal X-ray diffraction analysis shows that complex 1 is a 3D Evans-Showell-type POM-based metal-organic network. In complex 1, the 1D infinite double chain structure constructed from {{CuCo2Mo10H4O38}4-L} units and the μ4-bridging L ligand are linked by quadrate Cu2L2 loops to form a 2D layer, which is further connected by μ2-bridging L ligands, forming a 3D (2,3,4)-connected metal-organic framework. Complex 2 displays 3D supramolecular networks based on 1D {Co2Mo10H4O38-Zn-L}n infinite chains, which are constructed from Evans-Showell-type polyoxoanions and μ2-bridging 3-bpfp ligands (via ligation of pyridyl nitrogen atoms). The different coordination modes of the POM polyanions, bis(pyridylformyl)piperazine ligands and ratios play key roles in the construction of the title complexes. Significantly, the ligand L shows a μ4-bridging coordination mode in complex 1, which is observed for the first time in a POM system. Compounds 1 and 2 represent the first examples of metal-organic complexes based on Evans-Showell-type polyoxoanion and transition metal-bis-pyrazine-bis-amide coordination complexes. The fluorescence properties of the title complexes are reported herein. In addition, the title complexes act as heterogeneous Lewis acid catalysts for the oxidation of benzyl alcohol, and can also be recovered and reused without any significant loss in activity. Significantly, compound 1 with a 3D metal-organic framework showed higher catalytic performance with 99.4% conversion and 98.8% selectivity for benzoic acid at 10 h than compound 2 with 3D supramolecular networks.
Most of the previous studies have shown that the relationship between functional diversity and aboveground biomass is unpredictable in natural tropical forests, and hence also contrary to the ...predictions of niche complementarity effect. However, the direct and indirect effects of functional diversity on aboveground biomass via tree crown complementarity in natural forests remain unclear, and this potential ecological mechanism is yet to be understood across large-scale ecological gradients. Here, we hypothesized that tree crown complementarity would link positive functional diversity and aboveground biomass due to increasing species coexistence through efficient capture and use of available resources in natural tropical forests along large-scale ecological gradients. We quantified individual tree crown variation, functional divergence of tree maximum height, and aboveground biomass using data from 187,748 trees, in addition to the quantifications of climatic water availability and soil fertility across 712 tropical forests plots in Hainan Island of Southern China. We used structural equation modeling to test the tree crown complementarity hypothesis. Aboveground biomass increased directly with increasing functional diversity, individual tree crown variation and climatic water availability. As such, functional diversity enhanced individual tree crown variation, thereby increased aboveground biomass indirectly via individual tree crown variation. Additional positive effects of climatic water availability and soil fertility on aboveground biomass were accounted indirectly via increasing individual tree crown variation and/or functional diversity. This study shows that tree crown complementarity mediates the positive effect of functional diversity on aboveground biomass through light capture and use along large-scale ecological gradients in natural forests. This study also mechanistically shows that tree crown complementarity increases species coexistence through maintenance of functional diversity, which in turn enhances aboveground biomass in natural tropical forests. Hence, managing natural forests with the aim of increasing tree crown complementarity holds promise for enhancing carbon storage while conserving biodiversity in functionally-diverse communities.
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•Tree crown complementarity enhanced aboveground biomass•Tree crown complementarity and functional diversity promoted each other•Crown complementarity effect increased with soil fertility and climatic water availability•Soil fertility enhanced functional diversity•Structurally-complex stand can increase species coexistence and aboveground biomass
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Steel slag composite grout (SSCG) was prepared by a large amount of steel slag (SS) to reinforce expressway photovoltaic (PV) slopes and reduce carbon emission. Laboratory tests were conducted to ...investigate SSCG properties, including flowability, effective water-solid ratio (W/S), stone rate, initial and final setting time, as well as flexural strength (FS), unconfined compressive strength (UCS), FS/UCS ratio and microstructure of SSCG stone body. Ordinary Portland cement (OPC, 42.5) and sulphoaluminate cement (SAC, 42.5) grouts were selected to make contrasts. Based on the performance results, the recommended SSCG composition for engineering application is 40 % SS + 25 % blast furnace slag (BFS) + 20 % silicate cement clinker (CC) + 10 % fly ash (FA) + 5 % flue gas desulfurisation gypsum (FGDG). and the recommended admixture is: 6 % AA + 2 % bentonite + 0.4 % FND-C. With the above SSCG and related grouting techniques for slope soils, the soil cohesion was increased by 7.3–12.2 % and the angle of internal friction was increased by 10.2–19.7 %. To further validate the beneficial effects of SSCG on slope stability and the safe application of PV systems, numerical modelling calculations were conducted based on the soil sample test results. The simulations demonstrated the positive effect of SSCG in enhancing slope stability and facilitating the secure installation of PV systems on expressway slopes. The successful operation of grid-connected PV systems provided compelling evidence for the technical applicability of SSCG and it contributed to the application feasibility of PV systems to expressway slopes. The innovative use of SSCG in this study not only ensures the safety of construction projects but also contributes to environmental sustainability through the application of industrial slags.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The novel fluorescent sensors based on phenanthroline Schiff base can recognize Cd2+, Zn2+ and Eu3+.•L1–Eu3+ complex could be applied as selective sensor to distinguish malate anion from other ...carboxylate anions in an aqueous solution.•The binding constants were calculated and binding mechanism was given.
The compounds L1, L2 and D1 based on phenanthroline Schiff base bearing chiral amino alcohol groups had been synthesized and demonstrated. The sensing ability of the compounds in the presence of metal cations (Li+, Na+, K+, Mg2+, Co2+, Mn2+, Zn2+, Cd2+, Hg2+, Al3+, Cr3+, Fe3+, Eu3+) was studied by fluorescent spectroscopy. The experimental results indicated that compounds L1 and D1 could act as selective fluorescent sensors for Cd2+, Zn2+ with fluorescence enhancement and for the Eu3+ ion with fluorescence quenching in aqueous solution. Additionally, the emission properties of the L1–Eu3+ complex could be applied as selective sensor to distinguish malate anion from other carboxylate anions in an aqueous solution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The multibinding-site macrocycle R-4 was synthesized and the interactions of R-4 with various α-hydroxyl/amino carboxylate were studied in DMSO/H2O system (1:1, 0.01M Tris–HCl buffer, pH 7.4) by ...fluorescence titration experiments. The sensor R-4 was found to present high enantioselective fluorescent sensing ability to α-hydroxyl/amino carboxylate. It was observed that within a certain concentration range, the senor R-4 enantioselective responded to d-α-hydroxyl/amino carboxylates rather l-α-hydroxyl/amino carboxylates according to the fluorescence intensity. The results indicated that the sensor R-4 was very promising to be used as a fluorescent sensor in determining the enantiomeric composition of α-hydroxyl/amino carboxylates in DMSO/H2O system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
