Effect of fire on soil nutrients and under storey vegetation in Chir pine forest in Garhwal Himalaya,India

The study was carried out in the Pinus roxburghii Sargent (Chir pine) forest in the sub-tropical region of Garhwal Himalaya to assess the effect of fire on soil nutrient status at different altitudes (700 m, 800 m and 1000 m), soil depths (0–20 cm, 20–40 cm and 40–60 cm) and on under storey vegetation. The soil nutrients and under storey vegetation were assessed before fire (pre-fire) and after fire (post-fire). The results of the study indicate that fire plays an important role in soil nutrient status and under storey vegetation. The nutrients (soil organic carbon, nitrogen, phosphorus and potassium), decreased in post-fire assessment and with increasing altitudes, and soil depths, compared to pre-fire assessment. The under storey vegetation diminished after fire in all forest sites. The study concludes that in Chir pine forest, fire plays a role in reducing soil nutrients along the altitudinal gradient, soil depths and under storey vegetation. Thus, these nutrients can be saved through some management practices e.g. by early controlled burning and by educating local villagers about the negative impacts of severe wild fires on soil and vegetation.     

Wildfire spatial pattern analysis in the Zagros Mountains,Iran: A comparative study of decision tree based classifiers

Knowledge of wildfire behavior is of key importance for planning and allocating resources to fire suppression efforts. In this study, we analyzed the spatial pattern of wildfires with five decision tree based classifiers, including alternating decision tree (ADT), classification and regression tree (CART), functional tree (FT), logistic model tree (LMT), and Naïve Bayes tree (NBT). The classifiers were trained using historical fire locations in the Zagros Mountains (Iran) from the years 2007–2014 and a set of fifteen explanatory variables (i.e., slope degree, aspect, altitude, plan curvature, topographic position index (TPI), topographic roughness index (TRI), topographic wetness index (TWI), mean annual temperature and rainfall, wind effect, soil type, land use, and proximity to settlements, roads, and rivers) that were first optimized with a twostep process using multicollinearity analysis and the Gain Ratio variable selection method. The classifiers were then validated using the Kappa index and several statistical index-based evaluators (i.e., accuracy, sensitivity, specificity, precision, and F-measure). The global performance of the classifiers was measured using the ROC-AUC method. In this comparative study, the ADT classifier demonstrated the highest performance both in terms of goodness-of-fit with the training dataset (accuracy = 99.8%, AUC = 0.991) and the capability to predict future wildfires (accuracy = 75.7%, AUC = 0.903). This study contributes to the suite of research that evaluates data mining methods for the prediction of natural hazards.     

Managing road corridors to limit fire hazard. A simulation approach in southern France

Road corridors are sources of fire ignition and fire spread in French Mediterranean areas, but little is known about the flammability of vegetation and the probability of fire ignition and spread to neighbouring forests. This study simulated fire propagation in road corridors with the help of a cellular automata (CA). We assessed the relative importance of vegetation type, fuel treatment and the spatial patterning of vegetation on the probability of fire spreading to forests. The cellular automaton simulator was implemented with different types of corridors (30 m × 40 m), on the basis of an extensive field survey of vegetation. We used data from laboratory flammability experiments to determine the probability of ignition and propagation for each of the 20 cm × 20 cm cells of the CA. The probability of a fire reaching the neighbouring forest (P_FR) indicated that certain types of road corridors represent a very high risk owing to a combination of highly flammable vegetation and high spatial connectivity. The lowest P_FR values correspond to corridors with a decreasing vegetation flammability gradient in the vicinity of the forest. A several meter-wide embankment with low-flammable and/or managed vegetation can substantially reduce P_FR. These results suggest that firewise landscaping and local vegetation management can reduce fire risk in road corridors. Each corridor type should be subjected to specific vegetation management to account for flammability, growth pattern and lifetime.     

Post-fire dynamics of woody vegetation in seasonally flooded forests (impucas) in the Cerrado-Amazonian Forest transition zone

Fire disturbance alters the structural complexity of forests, above-ground biomass stocks and patterns of growth, recruitment and mortality that determine temporal dynamics of communities. These changes may also alter forest species composition, richness, and diversity. We compared changes in plant recruitment, mortality, and turnover time over three years between burned and unburned sites of two seasonally flooded natural forest patches in a predominantly savanna landscape (regionally called ‘impucas’) in order to determine how fire alters forest dynamics and species composition. Within each impuca, 50 permanent plots (20 m × 10 m) were established and all individuals ≥5 cm diameter at breast height (DBH) identified and measured in two censuses, the first in 2007 and the second in 2010. Unplanned fires burned 30 plots in impuca 1 and 35 in impuca 2 after the first census, which enabled thereafter the comparison between burned and unburned sites. The highest mortality (8.0 and 24.3% year⁻¹ for impuca 1 and 2) and turnover time (69 and 121.5 years) were observed in the burned sites, compared to 3.7 and 5.2% year⁻¹ (mortality), and 28.4 and 40.9 years (turnover), respectively, for the unburned sites. Although these seasonally flooded impuca forests are embedded in a fire-adapted savanna landscape, the impucas vegetation appears to be sensitive to fire, with burned areas having higher mortality and turnover than unburned areas. This indicates that these forest islands are potentially at risk if regional fire frequency increases.     

Detecting changes in climate forcing on the fire regime of a North American mixed-pine forest: A case study of Seney National Wildlife Refuge,Upper Michigan

The study of forests dominated by red pine (Pinus resinosa Ait.), one of the few fire-resistant tree species of eastern North America, provides an opportunity to reconstruct long-term fire histories and examine the temporal dynamics of climate forcing upon forest fire regimes. We used a 300-year long spatially explicit dendrochronological reconstruction of the fire regime for Seney National Wildlife Refuge (SNWR, 38,531 ha), eastern Upper Michigan to: (1) identify fire size thresholds with strong vs. weak climate controls, (2) evaluate effect of landform type (outwash channel vs. sand ridges) in modifying climate–fire associations, and (3) check for the presence of temporal changes in the climate control of large fire events over the time period 1700–1983. We used a summer drought sensitive red pine chronology (ITRDB code can037) as a proxy of past fire-related climate variability. Results indicated that fires >60 ha in sand-ridge-dominated portions of SNWR and >100 ha in outwash channels were likely climatically driven events. Climate–fire associations varied over time with significant climate–fire linkages observed for the periods 1700–1800 (pre-EuroAmerican), 1800–1900 (EuroAmerican settlement) and 1900–1983 (modern era). Although an increase in fire activity at the turn of 20th century is commonly associated with human sources of ignitions, our results suggest that such an increase was also likely a climatically driven episode.     

Comparison of boosted regression tree and random forest models for mapping topsoil organic carbon concentration in an alpine ecosystem

Soil organic carbon (SOC) plays an important role in soil fertility and carbon sequestration, and a better understanding of the spatial patterns of SOC is essential for soil resource management. In this study, we used boosted regression tree (BRT) and random forest (RF) models to map the distribution of topsoil organic carbon content at the northeastern edge of the Tibetan Plateau in China. A set of 105 soil samples and 12 environmental variables (including topography, climate and vegetation) were analyzed. The performance of the models was evaluated using a 10-fold cross-validation procedure. Maps of the mean values and standard deviations of SOC were generated to illustrate model variability and uncertainty. The results indicate that the BRT and RF models exhibited very similar performance and yielded similar predicted distributions of SOC. The two models explained approximately 70% of the total SOC variability. The BRT and RF models robustly predicted the SOC at low observed SOC values, whereas they underestimated high observed SOC values. This underestimation may have been caused by biased distributions of soil samples in the SOC space. Vegetation-related variables were assigned the highest importance in both models, followed by climate and topography. Both models produced spatial distribution maps of SOC that were closely related to vegetation cover. The SOC content predicted by the BRT model was clearly higher than that of the RF model in areas with greater vegetation cover because the contributions of vegetation-related variables in the two models (65% and 43%, respectively) differed significantly. The predicted SOC content increased from the northwestern to the southeastern part of the study area, average values produced by the BRT and RF models were 27.3 g kg⁻¹ and 26.6 g kg⁻¹, respectively. We conclude that the BRT and RF methods should be calibrated and compared to obtain the best prediction of SOC spatial distribution in similar regions. In addition, vegetation variables, including those obtained from remote sensing imagery, should be taken as the main environmental indicators and explicitly included when generating SOC maps in Alpine environments.     

Determination of mildronate by LC–MS/MS and its application to a pharmacokinetic study in healthy Chinese volunteers

A simple, rapid and accurate liquid chromatography–tandem mass spectrometry (LC–MS/MS) method has been developed and validated for the determination of mildronate in human plasma. Following a simple protein precipitation with methanol, the analyte was separated on a C₁₈ column by isocratic elution with methanol and 10 mM ammonium acetate (55:45; v/v), and then analyzed by mass spectrometry in the positive ion MRM mode. Good linearity was achieved over a wide range of 0.01–20 μg/mL. The intra- and inter-batch precisions (as RSD, %) were less than 7.1%. The average extraction recovery was 87.5%. The method described above has been used, for the first time, to reveal the pharmacokinetics of mildronate injection in healthy subjects. After single intravenously administration of 250, 500 and 1000 mg mildronate, the elimination half-life (t_1/2) were (5.56 ± 1.55), (6.46 ± 1.07) and (6.55 ± 1.17) h, respectively. The Student–Newman–Keuls test results showed that peak plasma concentration (C_max) and the area under the plasma concentration versus time curve from time 0 to 24 h (AUC_0–24) were both linearly related to dose. The pharmacokinetics of mildronate fitted the linear dynamic feature over the dose range studied. The essential pharmacokinetic parameters of multidoses administration intravenously (500 mg, b.i.d) were as follows: t_1/2 was (15.34 ± 3.14) h; C_max was (25.50 ± 3.63) μg/mL; AUC_0–24 was (58.56 ± 5.57) mg h/L. The t_1/2 and AUC of multidoses administration intravenously were different from those of single-dose administration significantly. These findings suggested that accumulation of mildronate in plasma occurred.     

Postprandial Dynamics of Plasma Glucose,Insulin, and Glucagon in Patients with Type 2 Diabetes Treated with Saxagliptin Plus Dapagliflozin Add-On to Metformin Therapy

ObjectiveTo analyze changes in plasma glucose, insulin, and glucagon in relation to glycemic response during treatment with dual add-on of saxagliptin (SAXA) plus dapagliflozin (DAPA) to metformin XR (MET) compared with SAXA add-on or DAPA add-on alone to MET in patients with type 2 diabetes mellitus (T2DM) poorly controlled with MET.MethodsDouble-blind trial in adults with glycated hemoglobin (HbAlc) ≥ 8.0 to ≤ 12.0% randomized to SAXA 5 mg/day plus DAPA 10 mg/day (n = 179), or SAXA 5 mg/day and placebo (n = 176), or DAPA 10 mg/day and placebo (n = 179) added to background MET ≥ 1,500 mg/ day. The mean change from baseline in the area under the curve from 0 to 180 minutes (AUC_{0-180 min}) was calculated for glucose, insulin, and glucagon obtained during a liquid meal tolerance test (MTT).ResultsGlucose AUC_{0-180 min} an was reduced more from baseline with SAXA + DAPA + MET (-12,940 mg/dL) compared with SAXA + MET (-6,309 mg/dL) and DAPA + MET (-11,247 mg/dL). Insulin AUC_{0-180 min} significantly decreased with SAXA + DAPA + MET (-1,120 μU/mL) and DAPA + MET (-1,019 μU/mL) and increased with SAXA + MET (661 μU/mL). Glucagon AUC_{0-180 min} only increased with DAPA + MET (2,346 pg/mL). The changes in glucose (P < .0001) and insulin (P = .0003) AUC_{0-180 min} correlated with change in HbA1c, whereas the change in glucagon AUC_{0-180 min} min did not (P = .27).ConclusionsWhen added to background MET, the combination of SAXA + DAPA provided additional reductions in glucose AUC_{0-180 min} and HbA1c without the increase in insulin seen with SAXA and without the increase in glucagon seen with DAPA. Changes in insulin and glucose but not glucagon AUC_{0-180 min} correlated with change in HbA1c. (Endocr Pract. 2014;20:1187-1197)     

Lodgepole pine forest age class dynamics and susceptibility to mountain pine beetle attack

Because mountain pine beetle attack mature pine stands, an understanding of forest age class dynamics is important to managing forests within the distribution of the beetle. The assumed theoretical negative exponential forest age distribution provides an estimate when ecosystem dynamics are in equilibrium. This study investigates the dynamics of forest age distribution for non-equilibrium ecosystem dynamics, which result primarily from large and irregular stand-replacement fire disturbances that alter the forest age distribution. A model experiment using the SEM-LAND model on a 1 million ha lodgepole pine forest landscape was conducted to estimate how the proportion of susceptible area could be influenced by different fire regimes. The results of the simulation suggest that the temporal dynamics of the area susceptible to mountain pine beetle attack are complex and depend on the fire history of the study area, if the area is experiencing large and irregular stand-replacement fires. The age range of the lodgepole pine forest stands susceptible to mountain pine beetle attack might significantly affect the estimate of the area susceptible to attack.     

Short-term effects of experimental burning on soil nutrients in the Cantabrian heathlands

The aim of this study is to determine the short-term effects of fire on nitrogen and phosphorus soil concentration in heathland sites dominated by Calluna vulgaris in the Cantabrian Mountain range (NW Spain). Three C. vulgaris heathlands sites (San Isidro, Riopinos I and Riopinos II) were selected. In June 2005, one plot (20 m × 20 m) per site was subjected to an experimental fire and the other was used as a control. Immediately after the fire, ten ash samples and ten soil samples (at a depth of 5 cm) were collected and thoroughly mixed. Soil moisture, temperature, total N, NH₄⁺, NO₃^?, total P, available P and pH were determined in each sample. The quantity of ashes deposited was 300 g/m², with a pH of 9, low N content but higher P concentrations. Significant differences in temperature and soil moisture were detected between the fire-treated and control plots. No significant differences for soil pH, total and available P, total N and NO₃^? concentration were found between the treatments. However, the concentration of ammoniacal-N indicated a significant increase 11 months post-fire and was produced by the changes in environmental soil conditions after the fire. Our results show that low intensity fires do not modify the concentration of N and P in the soil. However, post-fire conditions favour an increase in ammoniacal-N one year later.     

Spatial modeling of deforestation processes in the Central Peruvian Amazon

This study examines the relation between primary forest loss and landscape characteristics in the Ucayali region, Peru. Seven variables (rivers, elevation, annual precipitation, soil suitability for agriculture, population density, paved roads, and unpaved roads), were identified as potential deforestation drivers. The variables were converted into spatially explicit layers of continuous data and divided into a 9 km² grid. A multiple regression analysis was conducted to determine variable significance. Distance to paved and unpaved roads were strongly associated with deforestation, followed by distance to rivers, annual precipitation and elevation. All significant variables were negatively correlated with deforestation. Variables excluded from the model were population density and soil suitability for agriculture, suggesting that the influence of population density on forest clearing across the study area was not significant, and that deforestation activities were undertaken regardless whether soils are suitable for agriculture or not. Based on the linear regression analysis, the significant variables were selected and added to the Land Change Modeler in order to project primary forest coverage by 2025. The modeling results predict extensive deforestation along the Aguaytia River and at the forest/non-forest interface along the paved highway. The rate of primary forest removal is expected to increase from 4783 ha y⁻¹ (for the 2007–2014 period) to 5086 ha y⁻¹ (for the 2015–2025 period). A preliminary survey questionnaire conducted to explore deforestation intentions by farmers in the region, partly confirmed the overall deforestation trends as projected by the model.     

Prescribed burning as an alternative management in grasslands of temperate Europe: The impact on seeds

Fire is not an integral part of terrestrial ecosystems in temperate Europe, nevertheless prescribed burning is proposed to be an alternative to traditional management applied to grasslands. Thus, anthropogenic fire represents a serious challenge to plant species, and there is no information on how the recruitment of species responds to fire. The aim of our study was to assess the effect of fire on seed germination of 16 herbaceous grassland and ruderal species belonging to four common families. We first assessed the fuel load in open habitats in early spring and measured soil temperatures during experimental fires. After that we performed a controlled pot experiment involving heat treatments and experimental fire applied to seeds and followed their germination. Our measurements showed that maximum temperatures are between 73 °C and 264 °C on the ground surface and fire passage is fast, with short residence times of high temperatures. In deeper soil layers (1 cm and 5 cm), temperature increase is negligible. Seed germination of half of the species was decreased by the passage of fire, and a heat shock of 100 °C for 5 min had an even stronger adverse effect. Seeds of three Fabaceae species were stimulated by heat or fire, while negative effects prevailed among species belonging to other families. Anthropogenic fire in grasslands of temperate Europe might reduce recruitment by seed, particularly in species of the Asteraceae and Poaceae, two very important families with a large representation in temperate grasslands. Our results indicate that prescribed burning should be carefully applied in order not to endanger the local persistence of grassland species whose seedling emergence is negatively affected by fire.     

A territorial fire vulnerability model for Mediterranean ecosystems in South America

A forest fire risk model was designed and applied to a South American Mediterranean ecosystem, taking into consideration three analysis groups: fire risk; danger of fire spread, or propagation; and damage potential over economic threat values. The study area for development and validation of the model was the Mediterranean zone of central Chile and employed data from historical records spanning a 14 year period (1997–2010). Territorial data layers, combined with analysis of the statistical database and wildfire simulation have enabled areas of highest vulnerability to be defined with greater precision, especially in sectors associated with the urban–wildland interface (defined as the zone where man-made structures meet wildland). Maps generated by this model have enabled improvements to be made to the traditional mapping of fires currently undertaken in South American countries. The results shown here are applicable to other Mediterranean areas, where modifications are made to the entrance variables in the risk model.     

Synthesis and SAR studies of benzimidazolone derivatives as histamine H3-receptor antagonists

A novel series of benzimidazolone-containing histamine H₃-receptor antagonists were prepared and their structure–activity relationship was explored. These benzimidazolone analogs demonstrate potent H₃-receptor binding affinities, no P450 enzyme inhibition, and strong H₃ functional activity. Compound 1o exhibits the best overall profile with H₃K_i = 0.95 nM and rat AUC = 12.9 μM h.     

An in vivo microdialysis measurement of harpagoside in rat blood and bile for predicting hepatobiliary excretion and its interaction with cyclosporin A and verapamil

Harpagoside, a major bioactive iridoid glucoside in genus Scrophularia, has been widely used in clinical practice for the treatment of pain in the joints and lower back for its neuroprotective and anti-inflammation activities. To investigate the pharmacokinetics and hepatobiliary excretion, an in vivo microdialysis method coupled with high performance liquid chromatography was developed to monitor the concentration of harpagoside in blood and bile. The harpagoside bile-to-blood distribution ratio (AUC_bile/AUC_blood) up to 986.28 ± 78.46 significantly decreased to 6.41 ± 0.56 or 221.20 ± 18.92 after co-administration of cyclosporin A or verapamil. The results indicated that harpagoside went through concentrative elimination from the bile which was probably regulated by P-glucoprotein, providing possible clinical trials of co-administration of transporter inhibitors to decrease drug efflux, thus to enhance the curative effects.     

The effects of fire on woody plant encroachment are exacerbated by succession of trees of decreased palatability

The ingression of woody plants into the grassy layer of savannas and grasslands has become a global concern. The increase of woody plants has been primarily attributed over grazing, fire and more recently to the increase of atmospheric CO₂. We used long-term observations and analyses to assess changes in woody vegetation in Ithala Game Reserve (IGR), South Africa. Textural analysis of aerial photographs was used to detect changes in woody vegetation, from 1943 to 2007 in Ithala Game Reserve (IGR), South Africa. Daily rainfall data from 1905 to 2009 were used in a time-series analysis to determine if rainfall patterns have changed. The time-series analysis showed that the low magnitude (0–10 mm) rainfall events decreased from 1916 to 2009 and high magnitude rainfall events increased (10–20 and >20 mm). The mean annual rainfall increased from ～700 to ～850 mm from the 1930s to the 2000s. This change in rainfall was a key factor in the increase in woody vegetation from 1943 to 2009. We also used field data from the same reserve collected over 30 years to assess the increases in tree cover. Tree cover and density increased significantly by 32.5% and 657.9 indiv ha^?1 respectively, over 64 years. Before the proclamation of IGR in 1972, increases in woody vegetation from 1943 were non-significant. After the proclamation of IGR, herbivore population numbers and spatial distribution influenced the accumulation of grassy biomass required to fuel fires. In areas with reduced fuel loads, the consequential suppression of fire accelerated the rate of woody plant invasion into savannas. The increase in woody vegetation coincided with a decrease in palatable (e.g. Acacia gerrardii and Acacia davyi) and an increase in unpalatable woody plants. The avoidance of the unpalatable trees (e.g. Euclea and Searsia species) by large mammalian herbivores has allowed these trees to increase in density relatively unhindered.     

Species richness of soil gamasid mites (Acari: Mesostigmata) in fire-damaged mountain sites

Gamasid mites are important regulators of soil food webs in forest ecosystems. Wildfire is a dominant disturbance factor in forest ecosystems. We assessed the impact of fire on the species composition of soil gamasid mites at mountain sites following fires of four different degrees of severity and at one control site (5 years post-fire). In total, 14 families, 28 genera, and 54 species or species complexes were found. The abundance and richness were poor in severely burned sites compared to the less damaged sites. The different species compositions, especially in the medium-burned site, require further ecological study to improve our understanding. The fire response and recovery processes of selected species are also discussed.     

Determination of asiatic acid in beagle dog plasma after oral administration of Centella asiatica extract by precolumn derivatization RP-HPLC

A novel precolumn derivatization reversed-phase high-performance liquid chromatography (RP-HPLC) method with UV–vis detection for the quantitative determination of total concentration of asiatic acid (AA) in beagle dog plasma is described. AA was extracted with n-hexane-dichloromethane-2-propanol (20:10:1, v/v/v) from plasma, which had been hydrolyzed by acid and derivatized with p-Toluidine. Chromatographic separation was achieved on a C₁₈ column using gradient elution in a water–methanol system. Detection was set at UV wavelength of 248 nm. A calibration curve ranging from 0.01 to 1.5 μg/mL was shown to be linear, and the lower limit of quantification (LLOQ) was 0.01 μg/mL. The intra- and inter-day precisions which were determined by three different concentrations (0.05, 0.2 and 0.8 μg/mL) ranged from 4.4% to 13.1% and 4.6% to 14.2%, respectively. Mean extraction recoveries were no less than 65% for AA and ursolic acid (IS). Plasma samples containing asiatic acid were stable for 30 days at ?20 °C. The method was successfully applied to a pharmacokinetic study in beagle dogs after oral administration of Centella asiatica extract, and the main pharmacokinetic parameters obtained were: T_1/2, 4.29 h; T_max, 2.70 h; C_max, 0.74 μg/mL; AUC_0–t and AUC_0–∞, 3.74 and 3.82 μg h/mL, respectively.     

Forest cover dynamics analysis and prediction modeling using logistic regression model

Forest cover conversion and depletion are of global concern due to their role in global warming. The present study attempted to study the forest cover dynamics and prediction modeling in Bhanupratappur Forest Division of Kanker district in Chhattisgarh province of India. The study aims to examine and analyze the various explanatory variables associated with forest conversion process and predict forest cover change using logistic regression model (LRM). The forest cover for the periods 1990 and 2000, derived from Landsat TM satellite imagery, was used to predict the forest cover for 2010. The predictive performance of the model was assessed by comparing the model-predicted forest cover with the actual forest cover for 2010. To explain the effects of anthropogenic pressure on forest, this study considered three distance variables viz., distance from forest edge, roads and settlements, and slope position classes as explanatory variables of forest change. The highest regression coefficient (β = −26.892) was noticed in case of distance from forest edge, which signifies the higher probability of forest change in areas that are closer to the forest edges. The analysis showed that forest cover has undergone continuous change between 1990 and 2010, leading to the loss of 107.2 km² of forest area. The LRM successfully predicted the forest cover for the period 2010 with reasonably high accuracy (ROC = 87%).