Rainfall Interception Based on Indirect Methods: A Case Study in Temperate Forests in Oaxaca,Mexico

Rainfall interception represents the amount of water trapped in natural cover that is not drained directly to the ground. Intercepted rainfall may evaporate after a rain event, making it one of the main drivers of water balance and hydrologic regionalization. This process can be affected by factors such as climate, altitude, vegetation type, and topography. Here is a simple method of calculating rainfall interception in temperate forests using in Santa Maria Yavesia, Oaxaca, and Mexico as an illustrative study area. We used two rain gauges to measure net precipitation (N_p) under the canopy at each study site and one gauge outside the canopy to obtain gross precipitation (G_p). Throughfall (T_h) was indirectly measured using hemispherical photographs. Rainfall interception was obtained through a combination T_h and G_p and N_p. The mean rainfall interception was 50.6% in the Abies forests, 23%–40% in the coniferous‐mixed forests, and 27.4% in the broad‐leaved forests. We classified rainfall events by intensity to determine the effect of canopy structure and precipitation and found that 75% of the events were weak events, 24% were moderate events, and 1% were strong events. In addition, we found that rainfall interception was lower when the intensity of precipitation was higher. Our method can be replicated in different ecosystems worldwide as a tool for assessing the influence of rainfall interception in terms of ecological services.     

The effect of an active steering system on city bus drivers’ muscle activity

City bus drivers spend hours driving under time pressure, in congested traffic and in a monotonous sitting position. This leads to unhealthy working conditions, especially in terms of physical and psychological stress. The aim of this study is to investigate whether an active steering system can alleviate the musculoskeletal stress involved in manoeuvring a bus. Twenty bus drivers drove a city bus equipped with the Volvo dynamic steering (VDS) support system in real traffic. Steering effort was evaluated with electromyography and with a questionnaire. Compared to baseline, VDS significantly reduced the required muscle activity by on average 15–25% while turning, and up to 68% in the part of the manoeuvre requiring maximum effort. The bus drivers believed that VDS will help reduce neck and shoulder problems, and they expressed a desire to have VDS installed in their own bus.     

Analysis of perfluorooctanoate (PFOA) and other perfluorinated compounds (PFCs) in the River Po watershed in N-Italy

C7-C11 perfluorinated carboxylates (PFACs) and perfluorooctansulfonate (PFOS) were analysed in selected stretches of the River Po and its major tributaries. Analyses were performed by solid-phase extraction (SPE) with Oasis HLB cartridges and methanol elution followed by LC-MS-MS detection using 13C-labelled internal standards. High concentration levels ( approximately 1.3 microg l(-1)) of perfluorooctanoate (PFOA) were detected in the Tánaro River close to the city Alessandria. After this tributary, levels between 60 and 337 ng l(-1) were measured in the Po River on several occasions. The PFOA concentration close to the river mouth in Ferrara was between 60 and 174 ng l(-1). Using the river discharge flow data in m3 s(-1) at this point (average approximately 920 m3 s(-1) for the year 2006), a mass load of approximately 0.3 kg PFOA per hour or approximately 2.6 tons per year discharged in the Adriatic Sea has been calculated. PFOS concentration levels in the Po River at Ferrara were approximately 10 ng l(-1).     

Partial neutralization of rain by seaspray: the case of Recôncavo, Bahia-Brazil

In the Recôncavo of Bahia (located between 12°33′ and 13°10′S and 38°00′and 39°00′W), there are significant discharges of SO₂ and NO_x due to local, industrial and urban activities. The incoming air masses from the Atlantic Ocean are enriched with seaspray, which neutralizes part of the rain acidity. The extent of seaspray neutralization of rain acidity was quantified in four sites of the region, each with different loads of seaspray. Rain samples were obtained daily at the same time, integrating the precipitation of the previous 24 h, using wet-only collectors and analyzed for pH by potentiometry and for sodium by flame photometry. The amount of rain acidity in Recôncavo neutralized by seaspray ranged from <1% up to 88% and depended on the site. On average, neutralization ranged from 5% to 18%.     

Use of whole-body and subcellular Cu residues of Lumbriculus variegatus to predict waterborne Cu toxicity to both L. variegatus and Chironomus riparius in fresh water

We tested the use of whole-body and subcellular Cu residues (biologically-active (BAM) and inactive compartments (BIM)), of the oligochaete Lumbriculus variegatus to predict Cu toxicity in fresh water. The critical whole-body residue associated with 50% mortality (CBR₅₀) was constant (38.2-55.6 μg g⁻¹ fresh wt.) across water hardness (38-117 mg L⁻¹ as CaCO₃) and exposure times during the chronic exposure. The critical subcellular residue (CSR₅₀) in metal-rich granules (part of BIM) associated with 50% mortality was approximately 5 μg g⁻¹ fresh wt., indicating that Cu bioavailability is correlated with toxicity:subcellular residue is a better predictor of Cu toxicity than whole-body residue. There was a strong correlation between the whole-body residue of L. variegatus (biomonitor) and survival of Chironomus riparius (relatively sensitive species) in a hard water Cu co-exposure. The CBR₅₀ in L. variegatus for predicting mortality of C. riparius was 29.1-45.7 μg g⁻¹ fresh wt., which was consistent within the experimental period; therefore use of Cu residue in an accumulator species to predict bioavailability of Cu to a sensitive species is a promising approach.     

Photochemical degradation of methylparathion in the presence of humic acid

Photochemical degradation of methylparathion (O,O,-dimethyl O-4 nitrophenylphosphorothioate) in the presence of humic acid between pH 2 and 7 was monitored by differential pulse polarography. Humic acid was not electro-active under the experimental conditions used in this study. Only the pesticide and its main degradation product at pH 2 exhibited polarographic signals. Photolysis of methylparathion in acid media was sensitized by humic acid since the pesticide did not degrade in the absence of this compound. Methylparathion degradation in the presence of humic acid was observed at each of the studied pHs. The reaction was first-order with rate constant values ranging from 2 x 10(-3) to 6.3 x 10(-3) min(-1).     

Shell shape variation in populations of Mytilus chilensis (Hupe 1854) from southern Chile: a geometric morphometric approach

The pattern of shell shape variation in populations of the mussel, Mytilus chilensis (Hupe 1854) from Southern Chile was analyzed as a function of sample origin (cultivated vs. wild) and latitude, using standard tools of geometric morphometrics for landmark data. Additionally, posterior adductor muscle index (PAMI), Freeman condition index and shell thickness were measured in each sample. Highly significant differences in shell shape components were found among mussel populations. These differences are related to the origin of samples (expansion of the posterior adductor muscle scar, elongation of the lateral ligament and of the ventral umbo position in non-cultivated samples) and to latitude (more elongated shells and more extended posterior adductor muscle scar in most southern samples when compared with the northernmost ones). PAMI and shell thickness were statistically higher in wild population, and Freeman condition index was higher in cultivated shells. It is suggested that in wild populations of M. chilensis, the mussels may face higher predator pressures and other environmental stress factors. Consequently, individuals may be using higher energy fraction to reinforce shells and to promote adductor muscle growth at the expense of somatic growth. In contrast, individuals found in calm aquaculture environments are relatively protected from predators and use most of their assimilated energy in somatic growth. In turn, this growth depends on changes that covariate with shell morphology.     

Fire history and tree recruitment in the Colorado Front Range upper montane zone: implications for forest restoration

Forests experiencing moderate- or mixed-severity fire regimes are presumed to be widespread across the western United States, but few studies have characterized these complex disturbance regimes and their effects on contemporary forest structure. Restoration of pre-fire-suppression open-forest structure to reduce the risk of uncharacteristic stand-replacing fires is a guiding principle in forest management policy, but identifying which forests are clear candidates for restoration remains a challenge. We conducted dendroecological reconstructions of fire history and stand structure at 40 sites in the upper montane zone of the Colorado Front Range (2400-2800 m), sampled in proportion to the distribution of forest types in that zone (50% dominated by ponderosa pine, 28% by lodgepole pine, 12% by aspen, 10% by Douglas-fir). We characterized past fire severity based on remnant criteria at each site in order to assess the effect of fire history on tree establishment patterns, and we also evaluated the influence of fire suppression and climate. We found that 62% of the sites experienced predominantly moderate-severity fire, 38% burned at high severity, and no sites burned exclusively at low severity. The proportion of total tree and sapling establishment was significantly different among equal time periods based on a chi-square test, with highest tree and sapling establishment during the pre-fire-suppression period (1835-1919). Superposed epoch analysis revealed that fires burned during years of extreme drought (95% CI). The major pulse of tree establishment in the upper montane zone occurred during a multidecadal period of extreme drought conditions in the Colorado Front Range (1850-1889), during which 53% of the fires from the 1750-1989 period burned. In the upper montane zone of the Colorado Front Range, historical evidence suggests that these forests are resilient to prolonged periods of severe drought and associated severe fires.     

Artificial light at night (ALAN) causes variable dose-responses in a sandy beach isopod

Artificial Light at Night (ALAN) is expanding worldwide, and the study of its influence remains limited mainly to documenting impacts, overlooking the variation in key characteristics of the artificial light such as its intensity. The potential dose–response of fitness-related traits to different light intensities has not been assessed in sandy beach organisms. Hence, this study explored dose-responses to ALAN by exposing the intertidal sandy beach isopod Tylos spinulosus to a range of light intensities at night: 0 (control), 20, 40, 60, 80 and 100 lx. We quantified the response of this species at the molecular (RNA:DNA ratios), physiological (absorption efficiency) and organismal (growth rate) levels. Linear and non-linear regressions were used to explore the relationship between light intensity and the isopod response. The regressions showed that increasing light intensity caused an overall?~?threefold decline in RNA:DNA ratios and a?~?threefold increase in absorption efficiency, with strong dose-dependent effects. For both response variables, non-linear regressions also identified likely thresholds at 80 lx (RNA:DNA) and 40 lx (absorption efficiency). By contrast, isopod growth rates were unrelated (unaltered) by the increase in light intensity at night. We suggest that ALAN is detrimental for the condition of the isopods, likely by reducing the activity and feeding of these nocturnal organisms, and that the isopods compensate this by absorbing nutrients more efficiently in order to maintain growth levels.