Slow responses of understory plants of maple-dominated forests to white-tailed deer experimental exclusion

We examined the response of understory plants in mature maple-dominated forests of southern Québec, Canada, following about 30 years of high deer densities, using a deer exclosure experiment. An exclosure and a paired control of 625 m² each were established on six sites in 1998. An exclosure and a paired control of 16 m² were added at each of the same sites in 2003 but under a recent canopy gap to determine if light could enhance plant responses. We measured plant richness and abundance, and aboveground biomass of different plant groups for 8 years in the understory plots and for 3 years in the canopy gaps. Four herbaceous species were also monitored individually in the same plots. No significant differences between treatments were found in plots under forest cover, except for lateral obstruction at 0–50 cm height which was higher in the exclosures. Under canopy gaps, however, tree seedling and total plant abundance were higher in deer exclosures than in control plots. Trillium erectum recovered partially as individuals were taller, had larger leaves and more frequently produced a flower or a fruit in the absence of deer browsing under forest cover. To a lesser extent, Erythronium americanum and Maianthemum canadense also exhibited signs of recovery but were still at the single-leaf stage after 8 years of recovery. In general, the different plant groups exhibited little recovery following deer exclusion, possibly because of the low light levels that prevailed in the understory of undisturbed maple-dominated forests. The higher latitude of the present study could also contribute to the slow recovery rates of the different groups of plants compared to studies conducted in northeastern USA. Variability among sites and years had an effect on detection of statistically significant differences. Trends are however appearing over time, suggesting that many understory plants are recovering very slowly following deer exclusion. Our results emphasize the importance of studying large herbivore–forest interactions on different groups of plants, but also on specific species, and under different latitudes to be fully understood.     

Comparative efficiency and accuracy of variable area transects versus square plots for sampling tree diversity and density

Agroforestry systems have been recognized as areas with high conservation potential, and there is a need to quickly assess the biodiversity and tree stocking density available in these systems. However, it is not clear if the commonly used fixed area plot is most efficient for sampling such landscapes, or if a different method could provide equivalent data with less effort. Thus, a field and simulation-based study was carried out to compare the efficiency and accuracy of a variable area transect versus the fixed area square plot. Field efficiency tests were carried out in three habitat types, robusta coffee plantations, arabica coffee plantations and a privately owned forest fragment, in Kodagu, southern India. A simulation study of bias, precision and accuracy of the two methods for tree density estimation also was carried out using various spatial distribution patterns and densities. The variable area transect was significantly more efficient per unit effort in the field than the fixed area square plot. In the simulation tests both methods performed equally well under random spatial distribution. However, under simulated aggregated distribution both methods were positively biased (square plot up to 12% at low density, variable area transect 9–12% at all densities), and under simulated regular distribution the variable area transect was slightly negatively biased (−5 to −7% at medium to high density). The variable area transect thus can be recommended over the square plot for rapid assessment of tree diversity and density, when the vegetation is expected to be randomly dispersed.     

Observations sur la participation du cycle des pentoses phosphates au catabolisme glucidique de certains fruits

The following question arises: Do the glycolysis and the pentose phosphate cycle operate in the fruit during its maturity? The different results obtained yet with the banana and particularly with the apple and the pear suggest that the pentose phosphate cycle may operate in the preclimacteric fruit and then, decreases with a shift toward the glycolysis. Experiences were conducted with banana and with a non climacteric fruit: the cherry. It seems that cherry does not exhibit such a shift. It may be a difference between climacteric fruits and non climacteric ones.     

Physico‐chemical characterization of humic‐metal‐phosphate complexes and their potential application to the manufacture of new types of phosphate‐based fertilizers

The aim of this review is to describe the main physicochemical characteristics of diverse types of humic‐metal‐phosphate acid complexes. The effects of these complexes on phosphorus (P) fixation in soils with different pH values and physicochemical features and on plant phosphorus uptake are also discussed. Humic‐metal‐phosphate complexes have apparent stability constants in the same range as those of metal‐humic complexes, in solutions with diverse pH and ionic‐strength values. Likewise, the molecular‐size distribution of humic‐metal‐phosphate complexes as a function of pH is similar to that of potassium or sodium humates and metal‐humic complexes. Humic‐metal‐phosphate complexes are able to decrease phosphate fixation in soils and increase plant growth and phosphate uptake. Phosphorus fertilizers containing humic‐metal‐phosphate complexes proved to be efficient to improve plant growth and P uptake with respect to conventional fertilizers such as single superphosphate. The values of parameters related to plant phosphorus‐utilization efficiency (PUt E) suggest that the regulation of root acquisition of phosphate from these complexes could involve the interregulation of a system for the optimization of metabolic P utilization in the shoot and another system involving stress responses of roots under phosphorus deficiency.     

Breed-associated phenotypes in canine atopic dermatitis

Canine atopic dermatitis is a multifaceted disease, whose clinical presentation may be affected by numerous factors, including the genetic background of the animal, the environment, the offending allergens and flare factors. In particular, breed-associated differences have often been mentioned but never defined precisely. Using a large data set of atopic dogs, we document in this study the clinical presentation of nine often-affected breeds and demonstrate the existence of substantial differences between the clinical phenotype of each breed and the whole population. Some of the differences may be due to genetic differences while others are most likely to be associated with variations in environmental factors.     

Collaborative validation of the QuEChERS procedure for the determination of pesticides in food by LC-MS/MS

Seven FDA pesticide laboratories collaborated to develop and validate an LC-MS/MS method to determine 173 pesticides in <20 min. The average determination coefficient (r2) was >0.99 for all but two compounds tested. The limits of detection were <20 ng/mL for all compounds and <10 ng/mL for 363 of the 368 transitions reported. The method was used to determine pesticides in two AOAC sponsored proficiency samples. The LC-MS/MS determination was used for the analysis of oranges, carrots and spinach using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method. Each matrix was fortified at 20, 100, 400, and 1000 ng/g. No false positive responses were detected in controls of the three matrices. 165 pesticides had recoveries between 70 and 130%, and 161 had minimum detection levels less than 10 ng/g. Recoveries of 169 compounds for the 1000 ng/g spikes were within 50-150%. A matrix effect study indicated all three matrices caused a small net suppressing effect, the most pronounced attributable to the citrus matrix. The procedure proved to be accurate, precise, linear, sensitive and rugged, and adds 100 pesticides to the scope of the FDA pesticide program.     

In situ quantification of CH<Subscript>4</Subscript> bubbling events from a peat soil using a new infrared laser spectrometer

Purpose  

CH₄ emissions from peatlands are space and time dependent. The variety of efflux routes contributes to these variabilities. CH₄ bubbling remains difficult to investigate since it occurs on a timescale of seconds. The aims of this study were to use for the first time the recently built infrared high-resolution spectrometer, SPectrometre Infra-Rouge In situ Troposphérique to (1) measure in situ CH₄ fluxes in natural and artificial peatland plot and (2) observe online bubbling events with quantification of CH₄ emission fluxes corresponding to this very sudden degassing event.     

Heavy Metal Concentration Survey in Soils and Plants of the Les Malines Mining District (Southern France): Implications for Soil Restoration

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg^?C1 Zn, 90,000 mg kg^?C1 Pb, 9,700 mg kg^?C1 of As and 245 mg kg^?C1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metal-tolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg^?C1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.     

Reduced Atmospheric Manganese in Montreal Following Removal of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Methylcyclopentadienyl manganese tricarbonyl (MMT) was used between 1990 and 2003 as an antiknock agent and as an octane booster in Canadian unleaded gasoline. Its combustion leads to Mn emissions. The objective of this research was to examine the variations in atmospheric Mn in Montreal (Canada) from 2001 to 2007, covering the period prior (2001?C2003) to and following (2005?C2007) MMT use. Three sampling stations were selected because of their proximity to roads with widely differing and well-known traffic patterns. Filters from 2001 to 2007 were obtained from the Montreal Urban Community. The first sample of each month was selected, and Mn analysis was performed by neutron activation analysis. Total suspended particulates (TSP) was calculated by weighing the filters before and after dust collection. Results show a significant decrease of Mn over time at each station, whereas TSP decreased significantly in two stations. Comparing atmospheric Mn during and after the period of use of MMT 2001?C2003 vs 2005?C2007 showed a significant decrease at all stations. For TSP, only one station showed borderline significant decline between these two periods. Overall, between the two periods, Mn and TSP decreased by 39% and 17%, respectively. These data suggest that the combustion of MMT led to an increase of airborne Mn of approximately 22%. These findings should help in decision-making processes concerning the use of MMT in gasoline in other countries.     

Biochar as a strategy to manage plant diseases caused by pathogens inhabiting the soil: a critical review

Phytoparasitica - The current agricultural scenario faces a range of challenges, with phytosanitary ones being paramount. In most cases, plant diseases are treated with chemicals; however, they...