Tarin Toledo-Aceves

Tropical montane cloud forests: current threats and opportunities for their conservation and sustainable management in Mexico.

Tropical montane cloud forests (TMCF) are among the most threatened ecosystems globally in spite of their high strategic value for sustainable development due to the key role played by these forests in hydrological cycle maintenance and as reservoirs of endemic biodiversity. Resources for effective conservation and management programs are rarely sufficient, and criteria must be applied to prioritize TMCF for conservation action. This paper reports a priority analysis of the 13 main regions of TMCF distribution in Mexico, based on four criteria: (1) forest quality, (2) threats to forest permanence, (3) threats to forest integrity, and (4) opportunities for conservation. Due to the diverse socio-environmental conditions of the local communities living in Mexican TMCF regions, their associated social characteristics were also evaluated to provide a background for the planning of conservation actions. A set of indicators was defined for the measurement of each criterion. To assign priority values for subregions within each main region, an international team of 40 participants evaluated all the indicators using multicriteria decision-making analysis. This procedure enabled the identification of 15 subregions of critical priority, 17 of high priority, and 10 of medium priority; three more were not analysed due to lack of information. The evaluation revealed a number of subjects that had hitherto been undetected and that may prove useful for prioritization efforts in other regions where TMCF is similarly documented and faces equally severe threats. Based on this analysis, key recommendations are outlined to advance conservation objectives in those TMCF areas that are subjected to high pressure on forest resources.

Significance of Remnant Cloud Forest Fragments as Reservoirs of Tree and Epiphytic Bromeliad Diversity

Tropical Montane Cloud Forests (TMCF) support exceptional concentrations of biodiversity but are severely threatened by deforestation. In Mexico, 60% of TMCF tree species has been reported as threatened, and the epiphytic plants characteristic of these forests are particularly vulnerable to disturbance and climate change. We evaluated the role of remnant TMCF fragments as reservoirs of tree and epiphytic bromeliad biodiversity in southeastern Mexico. In four cloud forest fragments of varying size (1.2, 4.1, 6.6 and 9.8 ha), we recorded all trees ≥ 10 cm dbh in six 20 × 10 m plots and sampled eight trees at each site to measure bromeliad diversity. The assessment revealed that even very small forest fragments can host significant tree and epiphytic bromeliad diversity. In total, 45 tree and 18 bromeliad species were recorded among all the sites. These forest fragments are an important reservoir of both endemic tree species (seven species) and those with conservation status (nine tree species and one bromeliad species). Important variation in tree and bromeliad composition was found among fragments. This high heterogeneity among forest sites means that maintenance of even small fragments can play a strategic role in the conservation of biodiversity in the severely transformed landscape of the region. Such maintenance merits full consideration in the design of forest management policies and TMCF restoration initiatives.

Germination and seedling survivorship of three Tillandsia species in the cloud-forest canopy

Low germination and seedling survival probabilities are reported in various species of epiphytic bromeliad (Benzing 1978, Hietz et al . 2011, Toledo-Aceves & Wolf 2008, Winkler et al . 2005; but see Cascante-Marin et al . 2008). If germination and seedling survival are limiting factors in the life cycle, differential germination and seedling survival between species should be reflected in the relative abundance of established plants (Cascante-Marin et al . 2006, 2008) and in their presence or absence in secondary vegetation (Hietz et al . 2011), while differential germination within the tree would be expected to contribute to a heterogeneous distribution of established plants within the canopy (Hietz et al . 2011, Zotz & Vollrath 2002). Many factors influence the performance and distribution of epiphytes, including forest condition, disturbance type, distance from seed source, tree size and species, microclimate, epiphyte population dynamics and physiology (Cascante-Marin et al . 2009, Hietz et al . 2011, Valencia-Diaz et al . 2010, Zotz & Hietz 2001). In this study, we tested whether germination and seedling survival rates differ between the epiphytic bromeliads Tillandsia multicaulis Steud., T. punctulata Schldl. & Cham. and T. butzii Mez, and whether species abundance reflects the ability to germinate and survive as seedlings within the cloud-forest canopy. We also explore how morphological and physiological traits of the studied species can influence their early establishment.