Delayed and altered post-fire recovery pathways of Mediterranean shrubland under 20-year drought manipulation

<p>Increasing anthropogenic and natural disturbances have disturbed 75% of global land area, indicating many plant communities are unstable or in recovery process. Increasing water deficits by rainfall reduction may decrease resilience (rate of recovery) and trigger different succession pathways (e.g. delayed, altered mature status and advanced degradation). Knowledge on the effects of future drought on community structure and demographic dynamics is key to project the fate of vegetation and yet it is limited. </p><p>Here we assessed the impacts of long-term (20 years) experimental drought (-30% rainfall) on the successional pathways of species diversity, community composition and demographic changes for an early-successional Mediterranean shrubland (4 years after a wildfire). The results indicated that experimental drought significantly decreased species richness and shifted community composition compared to control plots. Significant decreases in abundance and increases in death ratios at both community (all species) and shrub (shrub species) levels were found in experimental drought. However, the abundance of Globularia Alypum was significantly increased by drought while Erica multiflora was not affected; the death ratios for the two species were significantly lower in drought than control plots. Species richness, community composition and abundance followed pathway 2 (altered mature state) while shrubland abundance followed pathway 3 (advanced degradation). Principal Component Analysis (PCA) indicated that the variance in vegetation metrics was notably explained by the first two dimensions (49.4%), mainly related to the death ratio of G. alypum and E. multiflora (27.3% for PC1) and abundance of community and shrub levels (22.1% for PC2). The space variation in PC1 significantly increased over time, which was orthogonal with PC2. Within two dimensions of PC1 and PC2, the scores in control were significantly higher than drought. </p><p>Our findings suggest that drier condition simulated by long-term drought could delay and alter the succession pathways of species diversity, community composition and abundance of the plant communities in Mediterranean ecosystems. The results also imply the importance to analyse long-term drought and extreme events on ecosystem functions (the strength of carbon storage in vegetation and soil) for such recovering communities.</p>

The Combined Effect of Mediterranean Shrubland Pasture and the Dietary Administration of Sage By-Products on the Antioxidant Status of Segureña Ewes and Lambs

The objective of this study was to determine if the combined effect of ewe grazing and the incorporation of sage by-products in the lamb feed enhances the Segureña ewe and lamb antioxidant status. For that, the endogenous (related to blood antioxidant enzymes) and exogenous (plasma antioxidant activity) antioxidant systems of ewes and lambs were studied at the physiological stages of lactation, after weaning and at the end of the fattening period. Major results indicated that grazing improved the enzymatic antioxidant defense of ewes during the stressful period of lamb weaning, and also, the antioxidant status of the ewe plasma at both physiological stages: lactation and after lamb weaning. With regards to the lambs, ewe grazing stimulated the antioxidant enzymatic defense during lactation, but not the antioxidant capacity of the plasma. At the end of the fattening period, the inclusion of sage by-products in the lamb diet (10% w/w) enhanced both the enzymatic cascade and antioxidant capacity of the lamb plasma. The antioxidant capacity of the lamb meat was also studied and the benefits of sage were detected in samples from the deltoideus muscle. Thus, Mediterranean grazing stimulated the antioxidant defense in ewes, while the inclusion of sage by-products in the lamb diets enhanced the antioxidant status of both blood and meat.