Authors:J. Lovett-Doust, A. Hegazy, O. Hammouda and N. Gomaa
Abundance-occupancy relationships were determined for desert plants in the northwestern Red Sea region, at both the whole landscape, and individual habitat levels. Some 58 stands (having a total of 66 species) were studied, using ten quadrats (10 × 10 m
) per stand. The relation was positive and highly significant at both scales, but stronger at habitat level than across the regional landscape. Niche-breadth was estimated as the number of habitats occupied regionally by a species, and was significantly related to both abundance and occupancy. Niche breadth explained just 10.1%of variation in abundance but some 56.2% of variation in occupancy. Using empirical data, we tested whether those abundance-occupancy relationships diverged significantly from a theoretical null model. Relationships diverged significantly from the null model at both regional landscape and habitat levels. Applications of abundance-occupancy relationships for plant conservation showed that 36% of the species in the study region is at risk of extinction.
Authors:A. Hegazy, J. Lovett-Doust, O. Hammouda and N. Gomaa
The distribution of plant communities and the pattern of species diversity were studied along an altitudinal gradient in the northwestern Red Sea region. A total of 58 stands were studied, using ten quadrats (10 m × 10 m) per stand. The classification of vegetation using the Two Way Indicator Species Analysis (TWINSPAN) identified five groups representing different altitudinal ranges. Detrended Correspondence Analysis (DCA) clearly distinguished these groups by the first two DCA axes. Edaphic factors such as soil texture, CaCO
, organic carbon, and electrical conductivity contribute to the distribution of plant communities. Species richness, Shannon-index of diversity and evenness show a hump-shaped curve along the altitudinal gradient, whereas beta diversity decreases with elevation. Variation in the diversity and the distributional behaviour of plant species and plant communities in the study area may be attributed to the change of water resources, climatic factors, edaphic variables and anthropogenic pressures along the elevation gradient. The implications of the results are discussed and recommendations are suggested for conservation and sustainable utilization of vegetation.
Authors:K Ghattassi, O Hammouda, A Graja, N Boudhina, H Chtourou, S Hadhri, T Driss and N Souissi
Very few studies have investigated the temporal specificity of melatonin (MEL) ingestion upon short-term maximal athletic performances. The aim of the present study was to explore the effect of morning MEL ingestion on cognitive and physical performances measured in the afternoon.
Twelve soccer players from a Tunisian squad (17.9 ± 1.3 years, 1.74 ± 0.06 m and 62.0 ± 8.8 kg) participated in the present study. They performed two testing sessions at 08:00 h, 12:00 h and 16:00 h after either MEL (5mg) or placebo (PLA) ingestion, in a randomized order. During each period, the participants performed the following cognitive and physical tests: reaction time and vigilance tests, medicine-ball throw (MBT), five jumps, handgrip strength (HG), and agility tests.
cognitive and physical performances were significantly higher at 16:00 h compared to 08:00 h during the two conditions (p < 0.05). Moreover, performances of MBT and HG were lower in the morning with MEL in comparison to PLA (p < 0.05). However, MEL ingestion did not affect physical and cognitive performances measured at 12:00 h and 16:00 h.
morning MEL ingestion has no unfavourable effect on afternoon physical and cognitive performances in soccer players.
Authors:MA Farjallah, O Hammouda, M Zouch, K Ghattassi, A Graja, T Driss, K Chamari and N Souissi
Fatigue is a limiting factor for sport performance. For this reason, optimal recovery after training is just as critical as the training program itself, if not more. Indeed, there is a need for strategies that can facilitate recovery after training, and one such strategy is the ingestion of supplements like melatonin (MEL). This study aimed to evaluate if MEL intake could improve recovery of athletes after an intermittent training session (ITS).
Fifteen elite female athletes (17.4 ± 0.4 years, 76.4 ± 5.6 kg, 1.76 ± 0.04 m; mean ± standard deviation) participated in two testing campaigns. During each period, they performed a battery of physical and cognitive tests before and after an ITS, as well as after ingesting MEL (6 mg tablet) or placebo in a randomized design. The ITS comprised the modified agility T-test, squat jump, counter movement jump, maximum standing ball-throw velocity test, maximum jump ball-throw velocity test, and 20-m sprint. Oral temperature (OT) and vigilance were evaluated before and after the ITS. Rating of perceived exertion (RPE), blood lactate [La], and glucose [Gl] were recorded after each ITS.
Short-term performance, recovery of physical performance, and OT were not affected by MEL ingestion after the ITS. Moreover, MEL did not affect cognitive performance or RPE scores after the ITS. However, [La] and [Gl] (p < 0.05 for both) were decreased after MEL ingestion.
MEL has no effect on the recovery of physical performance but may affect glucose utilization and lactate metabolism during the team-handball training session.
Authors:A Ammar, H Chtourou, O Hammouda, M Turki, F Ayedi, C Kallel, O AbdelKarim, A Hoekelmann and N Souissi
The aims of the present study were to: (1) investigate the effect of a weightlifting training session and time-of-day (TOD) upon biological parameters (i.e., oral temperature, hematological, C-reactive protein (CRP), and oxidative stress) and (2) assess their possible link with muscle damage responses. Nine weightlifters (21 ± 0.5 years) performed, in a randomized order, three Olympic-Weightlifting sessions (i.e., at 08:00, 14:00, and 18:00). Blood samples were collected at rest, 3 min and 48 h after each training session. Between pre- and post-training session, ANOVA showed significant increases in oxidative stress markers at the three TODs (p < 0.01) and significant increases for creatine kinase (CK) and lactate dehydrogenase (LDH) only at 08:00 and 18:00 (p < 0.05). At rest, the results showed a significant diurnal variation for the majority of the selected parameters except for malondialdehyde (MDA), total bilirubin, and CRP with higher values observed at 18:00 (p < 0.05). After the training session, given the higher rate of increase during the morning session, these diurnal variations persisted for temperature and WBC (p < 0.01) and were suppressed for CK, LDH, uric acid (UA), catalase, and glutathione peroxidase. The main significant correlations (p < 0.001) were observed between: (1) CK and MDA (r = 0.6) and CK and UA (r = 0.66 and r = 0.82) during the morning and evening training sessions; (2) CK and CRP only during the morning session (r = 0.5); and (3) CRP and WBC during the three training sessions (r = 0.8). In conclusion, the present findings: (1) confirm that the muscle damage responses could be induced by a high level of oxidative stress and (2) suggest to avoid scheduling training sessions in the morning given the higher muscle damage, inflammatory, and oxidative responses at this TOD.