Plant carbon inputs and environmental factors strongly affect soil respiration in a subtropical forest of southwestern China

Soil respiration is a large component of global carbon fluxes, so it is important to explore how this carbon flux varies with environmental factors and carbon inputs from plants. As part of a long-term study on the chemical and biological effects of aboveground litterfall denial, root trenching and tree-stem girdling, we measured soil respiration for three years in plots where those treatments were applied singly and in combination. Tree-stem girdling terminates the flow of carbohydrates from canopy, but allows the roots to continue water and nutrient uptake. After carbon storage below the stem girdles is depleted, the girdled trees die. Root trenching immediately terminates root exudates as well as water and nutrient uptake. Excluding aboveground litterfall removes soil carbon inputs, but allows normal root functions to continue. We found that removing aboveground litterfall and the humus layer reduced soil respiration by more than the C input from litter, a respiration priming effect. When this treatment was combined with stem girdling, root trenching or those treatments in combination, the change in soil respiration was indistinguishable from the loss of litterfall C inputs. This suggests that litterfall priming occurs only when normal root processes persist. Soil respiration was significantly related to temperature in all treatment combinations, and to soil water content in all treatments except stem girdling alone, and girdling plus trenching. Aboveground litterfall was a significant predictor of soil respiration in control, stem-girdled, trenched and stem-girdled plus trenching treatments. Stem girdling significantly reduced soil respiration as a single factor, but root trenching did not. These results suggest that in addition to temperature, aboveground carbon inputs exert strong controls on forest soil respiration.     

The Role of Mucus in Mytella falcata (Orbigny 1842) Gills from Polluted Environments

Water, Air, & Soil Pollution - This paper presents experimental data on particulate matter (PM10 and PM2.5) in the atmosphere of Candiota—South Brazil. Samples were collected using...     

Assessing insecticide and fungicide effects on the culturable soil bacterial community by analyses of variance of their DGGE fingerprinting data

To assess the effects of three insecticides (aldicarb, chlorpyrifos, deltamethrin) and two fungicides (tebuconazole and metalaxyl + mancozeb) on the PCR-DGGE fingerprints of culturable soil bacterial communities (CSBC), a greenhouse experiment was carried out with soil samples from an Integrated System for Agroecological Production (ISAP), a Conventional Potato Production Area (CPPA) and a Secondary Forest Area (SFA) close to the CPPA. Samples were obtained at 15 day intervals starting at 32 until 77 days after sowing (DAS) to perform the PCR-DGGE analysis of the CSBC cultured on media amended with soil suspension. Analysis of variance from PCR-DGGE data indicated significant differences among treatments. Regardless the type of pesticide applied, CSBC was disturbed and similarity values varied from 5% to 90% in comparison to the control. Significant shifts on CSBC were only detected among treatments in the first two harvests, while CSBC tended to be more akin to each other at the last two harvest dates. The most significant responses observed were due to different soil sample origins, where values of 5% of similarity to the control were observed on CPPA soil. The use of analysis of variance on PCR-DGGE data was useful to a better understanding of the changes on CSBC induced by pesticides applications.     

Bioactive cinchona alkaloids from Remijia peruviana

Three known Cinchona alkaloids of the quinine type, quinine (1), cupreine (2), cinchonine (3), and the possible artifact cinchonine-HCl (3-HCl), along with two new ones, acetylcupreine (4) and N-ethylquinine (5), have been isolated from the bark of Remijia peruviana (Rubiaceae). Their stereochemical structures were established by high resolution NMR spectroscopy. Alkaloids 2-4 had antifeedant effects on Leptinotarsa decemlineata with varying potencies. Compound 4 was cytotoxic to both insect Sf9 and mammalian CHO cells after 48 h of incubation, while 3-HCl had stronger and selective cytotoxicity to Sf9. Quinine 1 had a moderate to low effect on Trypanosoma cruzi. Tumoral cells were also affected by these alkaloids, with 4 and 3-HCl being the most cytotoxic to all the cell lines tested. Overall, the 8R, 9S configurations, as in 3 and 3-HCl, as well as the C-6'acetylated alkaloid 4, with an 8S, 9R configuration, showed stronger biological effects.     

<Emphasis Type="Italic">Achromobacter insolitus</Emphasis> and <Emphasis Type="Italic">Zoogloea ramigera</Emphasis> associated with wheat plants (<Emphasis Type="Italic">Triticum aestivum</Emphasis>)

This study reports for the first time the presence of diazotrophic bacteria belonging to the genera Achromobacter and Zoogloea associated with wheat plants. These bacterial strains were identified by the analysis of 16S rDNA sequences. The bacterium IAC-AT-8 was identified as Azospirillum brasiliense, whereas isolates IAC-HT-11 and IAC-HT-12 were identified as Achromobacter insolitus and Zoogloea ramigera, respectively. A greenhouse experiment involving a non-sterilized soil was carried out with the aim to study the endophytic feature of these strains. After 40 days from inoculation, all the strains were in the inner of roots, but they were not detected in soil. In order to assess the location inside wheat plants, an experiment was conducted under axenic conditions. Fifteen days after inoculation, preparations of inoculated plants were observed by the scanning electron microscope, using the cryofracture technique, and by the transmission electron microscope. It was observed that all isolates were present on the external part of the roots and in the inner part at the elongation region, in cortex cells, but not in the endodermis or in the vascular bundle region. No colonizing bacterial cells were observed in wheat leaves.     

Evaluation of the rates of soil organic matter mineralization in forest ecosystems of temperate continental,mediterranean, and tropical monsoon climates

The processes of the organic matter (OM) mineralization in forest soils developed under temperate continental (Moscow oblast, Russia), Mediterranean (the central and western parts of Spain), and tropical monsoon (southern Vietnam) climates were studied under laboratory conditions. The potential and specific rates of the OM mineralization (PR _min and PR _min/C_org, respectively), the ecophysiological parameters of the microbial communities status (C_mic, qCO₂, and C_mic/C_org), and the sensitivity of the rate of the OM mineralization to the rise in temperature were evaluated by the temperature coefficients (Q ₁₀) determined in the humus horizons (0–10 cm, without forest litter). The average values of PR _min for the climatic zones decreased in the following order: Mediterranean (57.1 ± 10.6 mg C/kg per day) > temperate continental (23.8 ± 7.1 mg C/kg per day) > tropical monsoon (10.4 ± 1.6 mg C/kg per day). The lowest resistance of the soil OM to mineralization as evaluated by the PR _min/C_org values was found in the Albeluvisol and Phaeozem of the temperate continental climate and in the Acrisol of the Mediterranean climate. The highest Q ₁₀ coefficients were attributed to the OM mineralization in the forest soils of the temperate continental climate. This allowed us to conclude that the observed and expected climate changes with an increase in the mean annual air temperature should lead to the maximum intensification of the OM mineralization processes in the forest soils of northern regions.     

Volatile compounds in Spanish, French, and American oak woods after natural seasoning and toasting

The volatile composition (volatile phenols, phenolic aldehydes, furanic compounds, lactones, phenyl ketones, and other related compounds) of Spanish oak heartwood of Quercus robur, Quercus petraea,Quercus pyrenaica, and Quercus faginea was studied by gas chromatography/mass spectrometry, in relation to the processing in barrels cooperage and in relation to the French oak of Quercus robur (Limousin) and Quercus petraea (Allier) and American oak of Quercus alba (Missouri), which are habitually used in cooperage. The volatile composition of seasoned oak woods varied according to individual trees, species, and origins, and the differences were more significant in Spanish species with respect to American species than with respect to French species. The toasting process influenced the volatile composition of wood. It led to high increases in the concentration of volatile phenols, furanic aldehydes, phenyl ketones, and other related structures, but the effect on w-lactones levels depended on species and origin. The volatile composition in Spanish oak species evolved during toasting like in French and American oak, but quantitative differences were found, especially important in American species with respect to European species.     

Mono- and Multielement Sorption of Trace Metals on Oxidic Industrial By-products

Assessing multielement adsorption of trace metals on materials having potential to be used as soil amendments is an essential stage for the remediation success, as soil contamination rarely occurs with a single element. This study evaluated mono-/multielement adsorption of Zn, Cu, Cd, and Pb on aluminum (AMB) and iron mining by-products (IMB, used for comparison). Prior to adsorption, these products were characterized by X-ray diffraction, isoelectric point, infrared spectroscopy, scanning electron microscopy, and microwave furnace digestion. Sorption experiments comprised: (1) pH adjustment (5.5, 6.5, and natural suspension pH), (2) mono- and multielement adsorption, and (3) desorption. Rising pH from 5.5 to natural suspension values (9.5) increased monoelement adsorption of Zn, Cu, Cd, and Pb on AMB up to 3.8-, 1.4-, 6.2-, and 1.1-fold, whereas multielement adsorption was increased up to 17.3-, 2.0-, 20.3-, and 1.2-fold, respectively. Zinc and Cd were less adsorbed than Cu and Pb and more affected by competition. Multielement adsorption at 5.5 pH in AMB resulted in smaller adsorption of Zn (up to 4.6-fold), Cu (1.4-fold), Cd (3.3-fold), and Pb (1.1-fold) when compared with monoelement adsorption. The lower the pH, the smaller the adsorption and the higher the desorption. The AMB showed higher capacity to maintain the elements adsorbed than the IMB.     

Targeted metabolite analysis and antioxidant potential of Rumex induratus

Targeted metabolite analysis of aqueous extract of Rumex induratus leaves, in terms of phenolic compounds and organic acids, and the study of its antioxidant activity against the DPPH(*) radical, a reactive oxygen species, hypochlorous acid, and a reactive nitrogen species, nitric oxide ((*)NO), were performed. The samples were collected in several locations, spontaneously occurring or from greenhouse culture, at different stages of development and seasons. The phenolic composition was achieved by high-performance liquid chromatography (HPLC)-diode array detection, and four hydroxycinnamic acid derivatives and 10 flavonoid glycosides (C- and O-heterosides) were determined. Organic acids composition was established by HPLC-UV, revealing five compounds. The total amount of phenolic compounds and organic acids were affected by growing conditions and developmental phase. The aqueous extract exhibited a dose-related activity against all tested reactive species.