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Human disturbance has disrupted the dynamics of plant communities. To restore these dynamics, we could take advantage of the microclimatic conditions generated by remaining patches of vegetation and plastic mulch. These microclimatic conditions might have great importance in restoring disturbed lava fields located south of Mexico City, where the rock is exposed and the soil is shallow. We evaluated the effects of both the shade projected by vegetation patches and plastic mulch on the mean monthly soil surface temperature (Tss) and photosynthetic photon flux density (PPFD) and on the survival and growth of Salvia mexicana throughout the year. This species was used as a phytometer of microsite quality. Shade reduced the T ss to a greater extent than mulch did. Both survival and growth were enhanced by shade and mulch, and the PPFD was related with seedling growth. During the dry season, plant biomass was lost, and there was a negative effect of PPFD on plant growth. At micro-meteorological scales, the use of shade projected by patches of vegetation and mulch significantly reduced the mortality of S. mexicana and enhanced its growth. Survival and growth of this plant depended on the environmental quality of microsites on a small scale, which was determined by the environmental heterogeneity of the patches and the landscape. For plant restoration, microsite quality must be evaluated on small scales, but on a large scale it may be enough to take advantage of landscape shade dynamics and the use of mulch to increase plant survival and growth.

Exotic species pose a threat to most ecosystems because of their potential to establish negative interactions with native biota. However, exotic species can also offer resources to native species, especially within highly modified environments such as urban ecosystems. We studied 17 exotic-native pairs of species with the potential to compete with one another, or in which one of the species could offer resources to the other, in an urban ecological reserve located within Mexico City. We used two-species occupancy models to analyze the potential association between the presence of the exotic species and the spatial distribution of the native species, as well as to assess if these species tend to avoid each other (negative spatial interaction) or to co-occur more often than expected under the hypothesis of independent occurrences (positive spatial interaction). Our results revealed few cases in which the exotic species influenced occupancy of the native species, and these spatial interactions were mainly positive, indicated by the fact that the occupancy of the native species was usually higher when the exotic species was also present. Seven of the eight observed non-independent patterns of co-occurrence were evident during the dry months of the year, when resources become scarce for most species. Our results also demonstrate that the observed patterns of species co-occurrence depend on the distance to the nearest urban structure and the amount of herb, shrub, and tree cover, indicating that these habitat features influence whether native species avoid or co-occur with exotic species. Our study represents an important contribution to the understanding of temporal dynamics in the co-occurrence between exotic and native species within urban ecological reserves.

Restoration requires techniques similar to those used in agriculture to improve germination and seedling vigor. We treated 6‐year‐old (collected in 2003, S‐2003) and 1‐month‐old (S‐2009) seeds of Dodonaea viscosa with hydropriming (HP). Seeds were made permeable with hot water prior to hydration for 24 or 48 hours (HP‐24 and HP‐48, respectively) followed by dehydration. The resulting seedlings exposed to both HP treatments were sown in a lava field in soil mixed with hydrogel (HG) under the shade projected by five vegetation patches. The effects of these treatments on germination, seedling field survival, and growth were assessed. HP‐24 in S‐2009 and HP‐48 in S‐2003 increased the germination percentage from 22.5 and 31.7% in control seeds (permeable seeds) to 63.3 and 98.3%, respectively. The seedlings‐2009 (from S‐2009) with HG maintained high survival in all vegetation patches. Seedlings‐2003, however, had low survival. The lack of HG was negatively related to the photon flux in each patch. Survival of seedlings‐2009 increased with HG of up to 398.41 µmol m−2 s−1; after which survival decreased. During the rainy season, HP enhanced seedling growth, except the basal diameters and number of leaves in the seedlings‐2003 with HP‐24. During the dry season, the effects of HG and HP were similar for all the seedlings. In the following rainy season, the priming effect was lost while HG continued to promote seedling growth. The combined use of HP and HG and the shade projected by the patches resulted in a successful vegetation recovery strategy.

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