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Background: Explored botanically from the 19th century, the Sierra de Chiconquiaco is recognized for its large vegetal and topographical heterogeneity. However, the available floristic information is sparse and its geographic characteristics remain undefined. The objective of this study was therefore to integrate floristic, vegetal and geographic information in order to identify areas that have experienced floristic exploration as well as potential sites for conservation. Question: Under which criteria can the Sierra be geographically delimited? What kind of floristic and vegetational studies have been carried out? How many species of plants have been registered? Which sites have been more widely explored? Which of them have conservation and research potentials? Study site and years of study: Sierra de Chiconquiaco, Veracruz, Mexico, 2010-2014. Methods: A bibliographical and records review of the XAL and MEXU herbariums, works and field survey were carried out. Through analysis of geomorphological attributes in a geographic information system, the boundaries of the Sierra were established, revealing an area of 3,632 km2, featuring 22 municipalities and an altitudinal range of 50 to 3,000 m a.s.l. Results: Seven vegetation types were described, as well as a floristic list of 3,019 species, including 72 type localities, 36 endemics, 57 registered in the NOM-059, 2010 and 195 in the CITES. Conclusions: Nine potential areas for conservation of flora were detected, as well as six that were scarcely documented in the herbaria. This study provides a relevant contribution to the knowledge, use and conservation of the vegetal resources of Mexico.

Key message Highly variable nighttime transpiration, with higher rates generally observed after preceding fog, is prevalent in dominant tree species of the nutri- ent-poor tropical montane cloud forest environment of central Veracruz, Mexico. Abstract Although nighttime transpiration (En) is pre- valent in a wide range of species from cloud-affected for- ests, its magnitude relative to total daily transpiration (Ed) as reported in the literature is generally small (En/Ed is 0.12 on average). In the present study, we observed high dry- season En/Ed ratios with large night-to-night variation in dominant species from the tropical montane cloud forest (TMCF) zone of central Veracruz, Mexico: 0.22 ± 0.18 for Quercus lancifolia (old-growth TMCF); 0.26 ± 0.14 and 0.16 ± 0.16 for Alchornea latifolia and Alnus jorull- ensis, respectively (regenerating post-fire TMCF); and 0.30 ± 0.20 to 0.12 ± 0.21 for Pinus patula (young and mature pine plantations). En was determined as the dif- ference between observed nocturnal sap flow and estimated refilling of stem water storage, the latter of which was on average: 21-25 % of nocturnal sap flow for Q. lancifolia ;6 and 5 % for A. latifolia and A. jorullensis, respectively; and 21-23 % for P. patula. Night-to-night variation in En was mostly due to large variation in vapor pressure deficit (VPD) related in turn to the alternation of cold fronts (producing fog events) and high pressure weather (pro- ducing nights with VPD up to 2 kPa). Moreover, in the hours following fog events without concurring rainfall, En was often higher as compared to fog-free nights with similar VPD across all species examined. Low-nutrient availability and high water content of the soils in the study area suggest a nutrient uptake benefit associated with the relatively high En rates observed.

Payment for hydrological services (PHS) are popular tools for conserving ecosystems and their water-related services. However, improving the spatial targeting and impacts of PHS, as well as their ability to foster synergies with other ecosystem services (ES), remain challenging. We aimed at using spatial analyses to evaluate the targeting performance of México's National PHS program in central Veracruz. We quantified the effectiveness of areas targeted for PHS in actually covering areas of high HS provision and social priority during 2003-2013. First, we quantified provisioning and spatial distributions of two target (water yield and soil retention), and one non-target ES (carbon storage) using InVEST. Subsequently, pairwise relationships among ES were quantified by using spatial correlation and overlap analyses. Finally, we evaluated targeting by: (i) prioritizing areas of individual and overlapping ES; (ii) quantifying spatial co-occurrences of these priority areas with those targeted by PHS; (iii) evaluating the extent to which PHS directly contribute to HS delivery; and (iv), testing if PHS targeted areas disproportionately covered areas with high ecological and social priority. We found that modelled priority areas exhibited non-random distributions and distinct spatial patterns. Our results show significant pairwise correlations between all ES suggesting synergistic relationships. However, our analysis showed a significantly lower overlap than expected and thus significant mismatches between PHS targeted areas and all types of priority areas. These findings suggest that the targeting of areas with high HS provisioning and social priority by Mexico's PHS program could be improved significantly. This study underscores: (1) the importance of using maps of HS provisioning as main targeting criteria in PHS design to channel payments towards areas that require future conservation, and (2) the need for future research that helps balance ecological and socioeconomic targeting criteria.