Bioclimates and vegetation along the Pacific basin of Northwestern Mexico

We describe relationships between the bioclimates and vegetation of the northwest of Mexico, including the Baja California peninsula and the stretch of the Pacific basin between the states of Sonora and Colima, a transition zone from the most arid deserts of North America to tropical rainforests. Links were inferred from temperature and rainfall data obtained from 453 weather stations that were used to construct climatograms, calculate several climate indices and describe main latitudinal and longitudinal trends, and from sampling the vegetation around these stations. Across this extensive area, spanning some 14° of both latitude and longitude as well as three zonobiomes and two zonoecotones, two macrobioclimates were identified, Mediterranean and Tropical, within which we were able to distinguish six bioclimates. For each of these bioclimates, we find different types of zonal and azonal vegetation, whose floristic composition and physiognomy are described here.     

Male sexual behavior contributes to the maintenance of high LH pulsatility in anestrous female goats

The objective of this study was to determine the importance of male sexual behavior in stimulating LH secretion in anovulatory female goats. Two groups of females (n = 10 per group) were each exposed to a buck in sexual rest and submitted to natural daylength. In one group, the buck was awake, whereas in the other group, it was sedated to prevent its sexual behavior. Two other groups of goats (n = 10 per group) were exposed to sexually active bucks that had been exposed to 2.5 months of long days. In one group, the buck was awake, and in the other group, it was sedated. LH secretion was determined every 15 min from 4 h before introducing the bucks to 8 h after, then every 15 min again from 20 to 24 h after introducing the bucks. The bucks submitted to natural daylength did not stimulate LH secretion (P > 0.05), whether they were sedated or not. In contrast, both the awake and the sedated light-treated bucks induced an increase (P < 0.05) of LH pulsatility in the first 4 h following their introduction. However, pulsatility remained elevated until 24 h in the females exposed to the light-treated awake buck, whereas in the group with the light-treated sedated buck, pulsatility diminished (P < 0.05) after the first 4 h of stimulation by the buck. In conclusion, the sexual behavior of males contributes to the maintenance of a high LH pulsatility up to 24 h after introduction into a group of anovulatory goats.     

Evidence that the photoperiod controls the annual changes in testosterone secretion, testicular and body weight in subtropical male goats

The aim of this study was to determine whether the reproductive seasonality of local male goats from subtropical Mexico (26 degrees N) is controlled by photoperiod. The control group (n = 7) remained in an open shed under natural daylight. The two experimental groups (n = 6 each) were placed in light-proof buildings and exposed for 2 years (yr) to alternations of 3 months (mo) of long days and 3 mo of short days. One group was first exposed to long days and the other one to short days. Body and testicular weights were determined every 2 wk. Blood samples were obtained weekly to determine testosterone plasma concentrations. In the control group, the body weight exhibited variations (P < 0.0001) and it increased during the non-breeding season. In both treated groups, long days stimulated weight gain and short days inhibited it (P < 0.0001). In the control group, testicular weight displayed variations (P < 0.0001), and high values were registered in June. In the treated groups, a testicular weight reduction occurred 6-9 mo after the onset of the study. Afterwards, the changes in testicular size varied according to daylength (P < 0.01). The pattern of plasma testosterone concentration in the control group varied over the study (P < 0.0001) and the levels were higher from May-June to November. In both treated groups, the changes in testosterone secretion occurred according to photoperiod changes (P < 0.0001). Short days enhanced testosterone secretion one photoperiodic cycle after the onset of the study and long days inhibited it. Local male goats from subtropical Mexico are sensitive to photoperiodic changes and this environmental cue may control the timing of the breeding season in natural conditions.     

Quantitation of aliphatic suberin in Quercus suber L. cork by FTIR spectroscopy and solid-state (13)C-NMR spectroscopy

This work determined that the percentage of suberin in cork may be found by solid-state (13)C cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy and by FTIR with photoacoustic detection (FTIR-PAS) spectroscopy. A linear relationship is found between the suberin content measured through CP/MAS spectral areas and that measured gravimetrically. Furthermore, application of a partial least squares (PLS1) regression model to the NMR and gravimetric data sets clearly correlates the two sets, enabling suberin quantification with 90% precision. Suberin quantitation by FTIR-PAS spectroscopy is also achieved by a PLS1 regression model, giving 90% accurate estimates of the percentage of suberin in cork. Therefore, (13)C-CP/MAS NMR and FTIR-PAS proved to be useful and accurate noninvasive techniques to quantify suberin in cork, thus avoiding the traditional time consuming and destructive chemical methods.     

Phytosociological,bioclimatic and biogeographical classification of woody climax communities of western North America

Abstract. In this study, combining the Braun-Blanquet phytosociological approach with numerical methods (cluster analysis and principal coordinate ordination), woody climax associations of western North America are described, ranging from NW Baja California (Mexico) to Alaska (USA), and including some interior zones of Idaho and Montana (USA), Alberta, British Columbia and the Yukon Territory (Canada). 95 floristic associations are identified, and each is characterized by floristic combination, biogeographical range, and bioclimatic conditions.