No abstract

Tree species richness changes along elevation gradients in response to underlying environmental conditions. Our hypothesis was that richness is associated with climatic variables and decreases with elevation. The objective was to identify trends in species, genus and family richness, diversity and vegetation structure in relation to climate variables along an elevation gradient with successive types of forest in Veracruz, Mexico. Trees were identified and measured in 0.1 ha at 15 sites located from 140 to 4000 m a.s.l. Generalized linear models were used to fit richness, diversity, basal area and density as a function of elevation; the best model was selected using Akaike's Information Criterion. Multivariate analyses were used to explore climatic variables associated to composition of groups of sites along the gradient. Along the entire elevation gradient, species, genus and family richness decreased unimodally, and diversity decreased monotonically. Richness was positively correlated with temperature but not with precipitation. Basal area increased monotonically and highest basal area was associated with high humidity and certain tree species (Quercus and Abies). Ordinations indicated three groups of sites: lower elevation dry forest associated with temperature seasonality, mid-elevation cloud forest associated with precipitation-related variables, and coniferous forest at the top of the gradient associated with elevation. Our study shows that different plant communities are associated with certain climatic conditions and harbour different tree species, genera and families. The results support the hypothesis that species richness is associated with climate, and decreases with elevation.

Macromycetes are a group of fungi characterized by the production of fruit bodies and are highly relevant in most terrestrial ecosystems as pathogens, mutualists, and organic matter decomposers. Habitat transformation can drastically alter macromycete communities and diminish the contribution of these organisms to ecosystem functioning; however, knowledge on the effect of urbanization on macrofungal communities is scarce. Diversity metrics based on functional traits of macromycete species have shown to be valuable tools to predict how species contribute to ecosystem functionality since traits determine the performance of species in ecosystems. The aim of this study was to assess patterns of species richness, functional diversity, and composition of macrofungi in an urban ecosystem in Southwest Mexico, and to identify microclimatic, environmental, and urban factors related to these patterns in order to infer the effect of urbanization on macromycete communities. We selected four oak forests along an urbanization gradient and established a permanent sampling area of 0.1 ha at each site. Macromycete sampling was carried out every week from June to October 2017. The indices used to measure functional diversity were functional richness (FRic), functional divergence (FDig), and functional evenness (FEve). The metric used to assess variation of macrofungal ecological function along the study area was the functional value. We recorded a total of 134 macromycete species and 223 individuals. Our results indicated a decline of species richness with increased urbanization level related mainly to microclimatic variables, and a high turnover of species composition among study sites, which appears to be related to microclimatic and urbanization variables. FRic decreased with urbanization level, indicating that some of the available resources in the niche space within the most urbanized sites are not being utilized. FDig increased with urbanization, which suggests a high degree of niche differentiation among macromycete species within communities in urbanized areas. FEve did not show notable differences along the urbanization gradient, indicating few variations in the distribution of abundances within the occupied sections of the niche space. Similarly, the functional value was markedly higher in the less urbanized site, suggesting greater performance of functional guilds in that area. Our findings suggest that urbanization has led to a loss of macromycete species and a decrease in functional diversity, causing some sections of the niche space to be hardly occupied and available resources to be under-utilized, which could, to a certain extent, affect ecosystem functioning and stability.

Urban forests are recognized worldwide as the most critical component of green infrastructure due to their capacity to provide various environmental goods and services. As cities continue to expand and their environmental problems intensify, there is a growing need for urban forests and green infrastructure to be better incorporated into strategic land-use planning, especially in developing cities. The first step in building an urban forest management plan is to capture characteristics of the urban forest and how these change across the built environment. Here, we used an urban biotope approach to classify urban forest and environmental characteristics in Mexico City. We sampled 500 fixed-area randomly stratified plots across the city to characterize urban forest structural and compositional variables. PCA and the broken-stick method were used to reduce the number of 25 urban forest variables down to five significant principal components that accounted for 78% of the data's cumulative variation. Ward's method helped classify biotopes into a hierarchical system with seven finer-level biotopes defined by urban forest characteristics (Dunn = 0.09, AC = 0.98), nested within two broader-level biotopes defined by forest canopy conditions (Silhouette = 0.59, AC = 0.99). A no-tree canopy biotope was extracted from sampling locations with no trees. The biotopes derived here can fundament biotope mapping, support decision-making in urban forest planning, including the identification of available planting spaces, tree diversity targets, and canopy protection. Our work in Mexico City demonstrates how the biotope approach can be adapted and used to better incorporate urban forests and green infrastructure into future management planning for any city.

Urban forests are recognized worldwide as the most critical component of green infrastructure due to their capacity to provide various environmental goods and services. As cities continue to expand and their environmental problems intensify, there is a growing need for urban forests and green infrastructure to be better incorporated into strategic land-use planning, especially in developing cities. The rst step in building an urban forest management plan is to capture characteristics of the urban forest and how these change across the built environment. Here, we used an urban biotope approach to classify urban forest and environmental characteristics in Mexico City. We sampled 500 xed-area randomly strati ed plots across the city to characterize urban forest structural and compositional variables. PCA and the brokenstick method were used to reduce the number of 25 urban forest variables down to ve signi cant principal components that accounted for 78% of the data's cumulative variation. Ward's method helped classify biotopes into a hierarchical system with seven ner-level biotopes de ned by urban forest characteristics (Dunn = 0.09, AC = 0.98), nested within two broader-level biotopes de ned by forest canopy conditions (Silhouette = 0.59, AC = 0.99). A no-tree canopy biotope was extracted from sampling locations with no trees. The biotopes derived here can fundament biotope mapping, support decisionmaking in urban forest planning, including the identi cation of available planting spaces, tree diversity targets, and canopy protection. Our work in Mexico City demonstrates how the biotope approach can be adapted and used to better incorporate urban forests and green infrastructure into future management planning for any city.