Alpine vascular plant species richness: the importance of daily maximum temperature and pH

Species richness in the alpine zone varies dramatically when communities are compared. We explored (i) which stress and disturbance factors were highly correlated with species richness, (ii) whether the intermediate stress hypothesis (ISH) and the intermediate disturbance hypothesis (IDH) can be applied to alpine ecosystems, and (iii) whether standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone. Species numbers and standing crop were determined in 14 alpine plant communities in the Swiss Alps. To quantify the stress and disturbance factors in each community, air temperature, relative air humidity, wind speed, global radiation, UV-B radiation, length of the growing season, soil suction, pH, main soil nutrients, waterlogging, soil movement, number of avalanches, level of denudation, winter dieback, herbivory, wind damage, and days with frost were measured or observed. The present study revealed that 82% of the variance in␣vascular species richness among sites could be explained by just two abiotic factors, daily maximum temperature and soil pH. Daily maximum temperature and pH affect species richness both directly and via their effects on other environmental variables. Some stress and disturbance factors were related to species richness in a monotonic way, others in an unimodal way. Monotonic relationships suggest that the harsher the environment is, the fewer species can survive in such habitats. In cases of unimodal relationships (ISH and IDH) species richness decreases at both ends of the gradients due to the harsh environment and/or the interaction of other environmental factors. Competition and disturbance seemed only to play a secondary role in the form of fine-tuning species richness in specific communities. Thus, we concluded that neither the ISH nor the IDH can be considered useful conceptual models for the alpine zone. Furthermore, we found that standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone, even though there is no direct causality.     

Modelling biomass of mountainous grasslands by including a species composition map

High mountain grasslands offer multiple goods and services to society but are severely threatened by improper land use practices such as abandonment or rapid intensification. In order to reduce abandonment and strengthen the common extensive agricultural practice a sustainable land use management of high mountain grasslands is needed. A spatially detailed yield assessment helps to identify possible meadows or, on the contrary, areas with a low carrying capacity in a region, making it easier to manage these sites. Such assessments are rarely available for remote and inaccessible areas. Remotely sensed vegetation indices are able to provide valuable information on grassland properties. These indices tend, however, to saturate for high biomass. This affects their applicability to assessments of high-yield grasslands.The main aim of this study was to model a spatially explicit grassland yield map and to test whether saturation issues can be tackled by consideration of plant species composition in the modelling process. The high mountain grassland of the subalpine belt (1800 – 2500 m a.s.l.) in the Kazbegi region, Greater Caucasus, Georgia, was chosen as test site for its strong species composition and yield gradients.We first modelled the species composition of the grassland described as metrically scaled gradients in the form of ordination axes by random forest regression. We then derived vegetation indices from Rapid Eye imagery, and topographic variables from a digital elevation model, which we used together with the multispectral bands as predictive variables. For comparison, we performed two yield models, one excluding the species composition maps and one including the species composition map as predictors. Moreover, we performed a third individual model, with species composition as predictors and a split dataset, to produce the final yield map.Three main grassland types were found in the vegetation analysis: Hordeum violaceum-meadows, Gentianella caucasea-grassland and Astragalus captiosus-grassland. The three random forest regression models for the ordination axes explained 64%, 33% and 46% of the variance in species composition. Independent validation of modelled ordination scores against a validation data set resulted in an R² of 0.64, 0.32 and 0.46 for the first, second and third axes, respectively. The model based on species composition resulted in a R² = 0.55, whereas the benchmark model showed weaker relationships between yield and the multispectral reflectance, vegetation indices, and topographical parameters (R² = 0.42). The final random forest yield model used to derive the yield map resulted in 62% variance explained and an R² = 0.64 between predicted and observed biomass. The results further indicate that high yields are generally difficult to predict with both models.The benefit of including a species composition map as a predictor variable for grassland yield lies in the preservation of ecologically meaningful features, especially the occurrence of high yielding vegetation type of Hordeum violaceum meadows is depicted accurately in the map. Even though we used a gradient based design, sharp boundaries or immediate changes in productivity were visible, especially in small structures such as arable fields or roads (Fig. 6b), making it a valuable tool for sustainable land use management. The saturation effect however, was mitigated by using species composition as predictor variables but is still present at high yields.     

Gender difference in the relationship of performance in the handgrip and standing long jump tests to lean limb volume in young adults

Groups of young, adult males and females performed the handgrip and standing long jump tests. Their total forearm and leg volumes were calculated from a series of circumference and length measurements, and the lean volumes (bone + muscle) calculated by taking the skinfold thickness into consideration. In the handgrip, the mean female performance was 298 N compared with 496 N for the males. In the standing long jump, mean performance expressed as distance x body mass was 87.3 kg.m for females compared with 137.7 kg.m for males. These superior performances of males could simply reflect their greater muscle mass, as the mean lean volumes of female and male limbs respectively were 0.54 l and 0.89 l for forearms, and 11.82 l and 14.82 l for the two legs. However, when the performances of males and females were grouped by lean limb volume, it was found that while in both tests there were linear relationships, males and females did not share a common line. In both tests the male relationship was at a higher level than the female; therefore, for a given lean volume, the male performance was significantly superior to that of the female. The gender difference found in this study has not been seen in other studies in which the performance of skeletal muscle has been related to the cross-sectional area of the active muscles and the possible reasons for the differences are considered.     

Cross-connections coordinate postural motoneuron activity in the crayfish abdomen

Intracellular recordings and dye injections were used to examine mutual coupling among slow abdominal postural motoneurons in the 4th abdominal ganglion in crayfish (Procambarus clarkii). Intracellular current injection into one motoneuron altered the spike firing rate of some of its synergists. Depending on the polarity of the injected current, the premotor effect on the synergists was excitatory or inhibitory. The magnitude of the effect was intensity dependent. No dye coupling was found among the motoneurons following injection of Lucifer yellow. The morphological basis of the coupling was examined by differential filling of motoneuron pairs, one with horseradish peroxidase and the other with Lucifer yellow. The stained motoneurons were simultaneously visualized under light microscopy to determine the proximity of their differently colored dendrites. It was thus possible to locate the site of the presumed monosynaptic contacts between them. Combined physiological and morphological evidence suggests that these neurons are mutually coupled, forming part of an integrative system for abdominal posture control in crayfish.     

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year^–1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha^–1 containing 1173 kg ha^–1 N; 126 kg ha^–1 P; 437 kg ha^–1 K; 1869 kg ha^–1 Mg; 125 kg ha^–1 Ca, and 2177 kg ha^–1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.     

Head posture and craniofacial morphology

The associations between craniofacial morphology and the posture of the head and the cervical column were examined in a sample of 120 Danish male students aged 22–30 years. Two head positions were recorded on lateral cephalometric radiographs, one determined by the subject's own feeling of a natural head balance (self balance position), and the other by the subject looking straight into a mirror (mirror position). Craniofacial morphology was described by 42 linear and angular variables, and postural relationships by 18 angular variables. A comprehensive set of correlations was found between craniofacial morphology and head posture. The correlations were similar for both head positions investigated. Of the postural variables, the position of the head in relation to the cervical column showed the largest set of correlations with craniofacial morphology. Extension of the head in relation to the cervical column was found in connection with large anterior and small posterior facial heights, small antero-posterior craniofacial dimensions, large inclination of the mandible to the anterior cranial base and to the nasal plane, facial retrognathism, a large cranial base angle, and a small nasopharyngeal space. The possible role of functional factors in mediating the relationship between morphology and posture was discussed.     

A method for 3D detection of symmetry line in asymmetric postures

The methods for symmetry line detection presented in the literature are typically suited to analyse symmetric upright postures, both standing and seated. The proposed method focuses on the symmetry line detection in subjects assuming asymmetric postures in which this line falls far outside the sagittal plane. The proposed approach evaluates the symmetry line by means of an autoregressive process in order to determine the set of planes suited to slice the back coherently with its geometric spatial configuration. The method is analysed assuming the cutaneous marking as reference and it is compared with a previous one, also developed by these authors. Results are analysed and critically discussed.     

Lower-body power,linear speed,and change-of-direction speed in Division I collegiate women’s volleyball players

Volleyball players need to sprint and change direction during a match. Lower-body power, often measured by jump tests, could contribute to faster movements. How different jumps relate to linear and change-of-direction (COD) speed has not been analyzed in Division I (DI) collegiate women’s volleyball players. Fifteen female volleyball players completed the vertical jump (VJ), two-step approach jump (AppJ), and standing broad jump (SBJ). Peak power and power-to-body mass ratio (P:BM) were derived from VJ and AppJ height; relative SBJ was derived from SBJ distance. Linear speed was measured via a 20-m sprint (0–10 and 0–20 m intervals); COD speed was measured using the pro-agility shuttle. Pearson’s correlations (p < 0.05) calculated relationships between the power variables, and speed tests. There were no significant relationships between the power variables and the 0–10 m sprint interval. Greater VJ height (r = -0.534) and P:BM (r = -0.557) related to a faster 0–20 m sprint interval. This be due to a greater emphasis on the stretch-shortening cycle to generate speed over 20 m. However, although a 20-m sprint may provide a measure of general athleticism, the distance may not be specific to volleyball. This was also indicated as the AppJ did not relate to any of the speed tests. Nonetheless, VJ height and P:BM, and SBJ distance and relative SBJ, all negatively correlated with the proagility shuttle (r = -0.548 to -0.729). DI women’s collegiate volleyball players could develop absolute and relative power in the vertical and horizontal planes to enhance COD speed.