Effects Of Functional Composition Research Articles

Effects of Tree Diversity, Functional Composition, and Large Trees on the Aboveground Biomass of an Old-Growth Subtropical Forest in Southern China

Forest aboveground biomass (AGB) plays an important role in regulating the global carbon cycle and is thus an essential component of ecosystem functioning. In the relationships between biodiversity and ecosystem functioning (BEF), studies have shown that many biotic factors (e.g., species, functional traits, and large trees) and abiotic factors have significant impacts on AGB. However, the relative strength of these affecting factors remains unclear. In this study, we analyzed woody plants (diameter at breast height [DBH] ≥ 1 cm) within a 1.6 ha plot in an old-growth subtropical natural forest in southern China. We used structural equation models to test the effects of tree diversity (species, phylogenetic, functional, and size inequality), functional composition, large trees, and environmental factors (topography, soil nutrients, and understory light) on AGB. Our results indicated that size inequality, the community-weighted mean of maximum DBH (CWM_MDBH), and large trees had significant, positive effects on AGB (p < 0.001), while lower soil phosphorus content was found to promote an increase in AGB. Furthermore, large trees, which were mostly composed of dominant tree species, were the main driver of AGB, and the effect of functional composition (e.g., CWM_MDBH) on AGB was substantially reduced by large trees. We argue that the selection effect plays a key role in regulating BEF relationships in subtropical natural forests and conclude that retaining large-diameter trees and dominant species, along with sustaining a complex stand structure, are key measures for improving productivity.

Functional composition enhances aboveground biomass stock undergoing active forest restoration on mining tailings in Mariana, Brazil

Functional composition is an important driver of aboveground biomass (AGB) variation in the tropical forest and has been demonstrated through the mass ratio hypotheses (MRH) that explain how dominant species and their functional traits have an important role in the AGB increase. We hypothesized that AGB stock of tree species is promoted by the simultaneous effects of restoration treatments and Technosol quality through functional trait composition. We tested the main effects of taxonomic, stand structural, functional attributes and abiotic factors undergoing different restoration methods (planting of nursery‐grown seedlings, seeding, and natural regeneration) and the effect of Technosol fertilization on AGB using different linear models. The functional traits were based on the community‐weighted mean of the community of values of functional traits related to MRH. Stems and biomass distribution were categorized into the following functional groups: successional strategy, dispersal syndrome, nitrogen fixation, wood density (WD). As expected, during early restoration stage, the pioneer and anemochoric species were dominants mainly represented by naturally regenerated stems. However, the autochoric dispersal and nitrogen‐fixing tree species were biomass dominant groups in active restoration, driven mostly bySenna alatawhich had high abundance and WD. We found that high WD and active restoration methods determine higher AGB stock on mining tailings where natural regeneration is limited. We conclude that functional composition reverses the effects of species richness and abundance on AGB tenting the MRH. Therefore, the effects of functional composition and restoration methods are key predictors on ecosystem functioning during forest restoration.

The effect of organic matter humification (aromaticity and oxidation degree) on structural and nanomorphological characteristics of humic nanocomposites of metallic platinum

BackgroundIt has been previously found that humic substances (HSs) can serve as the environmentally benign non-toxic agent for the preparation of magnetic and noble metals nanoparticles that are increasingly used in biomedicine. The structure of HSs and, hence, their synthetic potential depend on the source of their origin. Thus, humification character, determined by conditions and duration of complex transformation of organic remains in HSs can evidence their structure, in particular their aromaticity and oxidation degree. The incorporation of platinum nanoparticles in a shell of HSs allows obtaining aggregate-stable nanomaterials with directly controlled structural and nanomorphological characteristics, which combine the properties of platinum nanoparticles (selective cytotoxicity, anti-inflammatory activity, etc. And a complex of biological properties of HSs (antioxidant, immunomodulatory and anti-inflammatory activity. At the same time, the expression of valuable properties of platinum nanoparticles can be varied directly by changing their nanomorphological characteristics that strongly depend on the conditions of synthesis, in particular on the HSs type which is used for the synthesis. AimTo study the effect of humification (aromaticity and oxidation degree) of three types of humic substances extracted from natural Mongolia sources (therapeutic muds of Gurvan Nuur Lake, brown coal of Baganuur coal deposit and shale of Shine Hudag deposit) on structural and nanomorphological characteristics of Pt0-containing nanocomposites produced on their basis. MethodsNanocomposites with Pt0 content 1.2–6.5% were synthesized by reduction of hydrogen hexachloroplatinate with HSs in an aqueous-alkaline medium upon heating (90 °C). The yield of nanocomposites varied depending on type of HSs in the range 75–96%. The structure, composition and morphology of obtained nanocomposites were characterized by complex of modern physical and chemical methods (elemental analysis, XRD, SEM, TEM, IR- and optical-spectroscopy, DLS). ResultsThe platinum-containing nanocomposites have been synthesized using the reduction and stabilizing potentials of HSs with different degrees of humification (aromaticity and oxidation degree) and isolated from three natural Mongolian sources. The effect of functional composition, including oxidation and aromaticity degrees of HSs on the yield, quantitative and nanomorphological characteristics of produced platinum nanocomposites has been found. It is established that under the same reaction conditions platinum nanoparticles with face-centered cubic lattice and the smallest average size (9–15 nm) are formed from humic substances extracted from coal, while HSs derived from mud and shale afford the nanoparticles of larger size (18–28 and 16–26 nm respectively). The increase of platinum content in nanocomposites enlarges their average size, decreases their aggregate stability, as well as augments oxidation degree of HSs macromolecules. The reduction of platinum from precursor to the zero-valent state occurs due to oxidation of the phenolic and alcoholic hydroxyl groups, which are major components of HSs, as well as carbonyl groups. At the same time, HSs cover individual platinum nanoparticles, making them water soluble and preventing their aggregation. ConclusionThus, we have synthesized a series Pt0-containing nanocomposites containing 1.2–6.5% with use as reducing and stabilizing matrix of natural available HSs with different humification characteristics (aromaticity and oxidation degree) and isolated from three natural Mongolia sources It is found that obtained nanocomposites are formed in form of platinum nanoparticles mainly of spherical shape and size of 3–42 nm distributed in a matrix of HSs. Polyfunctional composition of HSs is determined by conditions of their transformation and degree of humification, which provides their reducing and stabilizing properties during the synthesis of platinum metallic nanocomposites. It is established that Pt0 nanoparticles with the smallest average size and the highest aggregate stability are generated from HSs-coal with the lowest oxidation degree. These data contribute significantly to understanding of possible control of the nanomaterials synthesis and prediction of their properties.