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Eriobotrya japonica is a non-native tree expanding in secondary forests and threatening the tropical montane cloud forest of central Veracruz, Mexico. Our objective was to investigate whether E. japonica has invasive potential by examining morphological and physiological functional traits in response to drought events. We did field surveys in a cloud forest reserve, and determined responses to experimental drought on germination, growth, morphological (leaf area, specific leaf area, thickness, and chlorophyll content) and physiological (hydraulic conductivity, maximum photosynthesis, and stomatal conductance) functional traits. Eriobotrya japonica adults, saplings, and seedlings were dominant in secondary forest, but scarce in mature forest. In lab, cumulative germination curves were similar across treatments (low–high temperatures; drought, water) while in the forest there was a delayed germination in drought treatment, though ultimately total germination was similarly high in the lab and field. Growth of seedlings was higher in light gaps than in the understory. However, leaf area was similar across treatments, SLA was lower, and thickness and chlorophyll content were higher in the gap-drought treatment. Physiological traits reinforced that E. japonica is highly drought resistant as demonstrated by avoidance of losses in hydraulic conductivity and high levels of carbon fixation. In a drought experiment, it took over 2 months to reach injurious losses in hydraulic conductivity. This study demonstrated that germination, growth, and physiological maintenance will all be unaffected in drought conditions and we concluded that E. japonica has potential to become an invasive alien species. [ABSTRACT FROM AUTHOR]

Compared to enrichment planting techniques, direct seeding may represent a viable low-cost method to ensure the conservation and recovery of forest ecosystems. However, it is necessary to identify the environmental factors that affect seed germination and seedling establishment in order to improve the success of this technique. It has been suggested that the establishment of Oreomunnea mexicana (Juglandaceae), a threatened tropical montane cloud forest tree species, is associated with microsites of high soil moisture. We assessed seedling emergence in O. mexicana through direct seeding in a secondary forest and characterized the microenvironmental conditions of the sowing microsite. We also assessed the effect of seed hydration on seedling emergence and evaluated the effect of soil moisture content and seed hydration in O. mexicana seed germination and seedling emergence under laboratory conditions. Seedling emergence was lower in the field than in the laboratory (37 vs. 42 %, respectively). At microsite level, seedling emergence correlated positively with soil moisture content but negatively with vegetation cover. After 11 months, 52 % of the emerged seedlings still survived. Under laboratory conditions, seedling emergence did not differ significantly between hydrated and non-hydrated seeds (43.2 ± 0.52 vs. 40.3 ± 0.51 %, respectively), but did between high and low soil moisture contents (80 ± 0.18 vs. 3.5 ± 0.085 %, respectively). With appropriate soil moisture and vegetation cover conditions, O. mexicana seed introduction into secondary forest is a reliable technique. However, the method could be improved by protecting the seedlings from physical damage. [ABSTRACT FROM AUTHOR]

Soil seed banks may contribute to forest recovery, but the presence of exotic grasses may represent a constraint for the natural regeneration process. This study aims to evaluate the composition of seed banks in three successional stages of the lower montane peri-urban forest in Veracruz, Mexico, and experimentally determine the role of an exotic grass ( Cynodon plectostachyus) in suppressing seed bank expression. For this, soil samples were collected from an abandoned pasture (P), a young secondary forest (SF), and an old secondary forest (F), and grass was experimentally removed in P. Seed density (seeds/m) was higher in P (12,189 ± 2421), followed by SF (2825 ± 347) and F (3552 ± 865) with 76, 75 and 78 species, respectively. Tree seeds accounted for 1689 (P), 126 (SF) and 265 (F) emerged seedlings of 6, 8 and 6 tree species, respectively. The highest percentage of pioneer tree species was recorded in P seed banks (99 %). Similarity in tree species composition of the seed banks was higher between P and SF (Jaccard = 0.8) than between P and F (0.5). Similarity between soil seed bank tree species and tree standing vegetation was higher in P than in SF and F. Aboveground (1810 g/m) and belowground (508 g/m) biomass of C. plectostachyus is suppressing the emergence of individuals from the seed bank: when the grass was removed, nine woody species became established. Exotic grass removal in small nuclei may trigger early forest recovery through allowing the establishment of the tree species already present in the soil seed bank. [ABSTRACT FROM AUTHOR]

The montane forest in central Veracruz, Mexico is a hotspot of biodiversity. We asked whether lower and upper montane forests could be distinguished in this ecoregion. Variables of vegetation and seasonality in precipitation were tested across 14 sites between 1,250- and 2,550-m elevations. A total of 1,639 individuals and 128 tree species was recorded. There was a unimodal pattern in the richness of species, genera, and families; their richness was positively correlated with precipitation in the wettest quarter of the year, though there were no differences in the basal area and density. Rarefaction, species turnover, nonmetric multidimensional scaling, and a cluster histogram suggest two major groups: lower elevation forests that are less diverse, have low beta diversity and are more similar in composition, with Clethra macrophylla, Liquidambar styraciflua, and Quercus lancifolia as indicator species; and higher elevation forests that are more diverse, have high species turnover, and include forests with Quercus corrugata and Prunus rhamnoides, and forests with Fagus grandifolia, Persea americana, and Ternstroemia sylvatica as indicator species. However, other communities (an Oreomunnea mexicana at the upper site, and a limestone site in the lower forests), exemplify the high regional heterogeneity. We conclude that elevation and seasonality in precipitation produce a directional change in richness and indicator species, but not in vegetation structure. Lower montane forests differed from cloud forests at upper elevations. However, other factors should be included-mainly biogeographic affinities, historic and recent anthropogenic disturbance-to conclusively distinguish them. Montane forest can still be considered very heterogeneous and very high in beta diversity. [ABSTRACT FROM AUTHOR]

Gradient analysis is rarely used in studies of fungal communities. Data on macromycetes from eight sites along an elevation gradient in central Veracruz, Mexico, were used to demonstrate methods for gradient analysis that can be applied to studies of communities of fungi. Selected sites from 100 to 3,500 m altitude represent tropical dry forest, tropical montane cloud forest, conifer forest, and their ecotones. From May to October 2010, macromycetes were collected monthly within ten 10 × 10 m permanent plots per site. In total, 672 individuals of 213 species of macromycetes were recorded. Models for richness and diversity for all macromycete and ectomycorrhizal communities displayed peaks in the mid-part of the gradient, and a tendency to increase with elevation, whereas xylophagous fungi displayed a peak in the mid-lower part but tended to decrease with elevation. Cluster and Maximum Likelihood analyses distinguished four communities for both macromycetes and trees, but plant and fungal communities were only partly concordant. Canonical correspondence analysis indicated that macromycete distribution along the gradient is related to slope, relative humidity, soil temperature, soil water content, canopy openness, and litter depth. Spearman's correlation and regression trees suggested that air and soil temperature, relative humidity, soil water content, canopy openness, vegetation structure and tree species richness were most strongly related to macrofungal functional groups, but these environmental variables were often correlated to the forest type and may not be causal. Variation in the environment along the elevation gradient differentially affected macromycete functional groups. Results from the different methods used in this work were concordant and showed significant patterns. [ABSTRACT FROM AUTHOR]

Species for restoration forestry on degraded lands in the tropics are often restricted to a few well-known exotic timber species. This selection frequently leads to failed projects, as local people expect trees to cover a number of uses, not only timber. We studied local knowledge of the usefulness, scarcity and importance for wildlife of native tree species in central Veracruz, Mexico, a region with mainly secondary vegetation and remnants of tropical dry forest. Data were obtained from several workshops, in depth interviews of 40 key informants, field walks with informants, and botanical collections. Analysis included indices for cultural importance, scarcity and wildlife relevance. We documented 76 species in one or more of the categories, from primary, secondary, agroforestry and riparian habitats. Fabaceae was the most important family. All of the species were useful for humans, mainly for rural construction, food, fence posts and fuel. Two-thirds of the species were considered scarce though they were not necessarily rare-some were highly useful, overexploited species with populations insufficient for demand; this category included five of the ten most important species culturally. Also, two-thirds of the tree taxa were considered important for wildlife, especially species of Moraceae. The study shows that the local population is highly aware of the varying functions of trees in the landscape. However, few of the important species are available from regional nurseries. We propose a number of species for restoration forestry, agroforestry systems and enrichment plantings that would be valued by landowners. [ABSTRACT FROM AUTHOR]

Secondary succession following land abandonment, represented by a chronosequence of 15 old fields (0-80 years old) and two old-growth forests, was studied in the tropical montane cloud forest region of Veracruz, Mexico. The objective was to determine successional trajectories in forest structure and species richness of trees ≥5 cm DBH, in terms of differences in seed dispersal mode, shade tolerance, and phytogeographical affinity. Data were analyzed using AIC model selection and logistic regressions. Mean and maximum canopy height reached values similar to old-growth forest at 35 and 80 years, respectively. Species richness and diversity values were reached earlier (15 and 25 years, respectively) while basal area and stem density tended to reach old-growth forest values within 80 years. Along the chronosequence, the proportion of species and individuals of wind-dispersed trees declined, that of bird dispersed small seeded trees remained constant, while that of gravity and animal dispersed large seeded trees increased; shade-intolerant species and individuals declined, while intermediate and shade-tolerant trees increased. Shade-tolerant canopy trees were rare during succession, even in the old-growth forest. Tropical tree species were more frequent than temperate ones throughout the chronosequence, but temperate tree individuals became canopy dominants at intermediate and old-growth forest stages. [ABSTRACT FROM AUTHOR]

Secondary successional vegetation represents one-third of the 7% of the original area covered with tropical dry forest that remains in central Veracruz, Mexico. In this region, fallow periods are short, in general, no longer than 7-10 years, and old secondary successional sites are not available. Therefore we evaluated the potential of very early successional stages of tropical dry forest with different land use histories for recovering the structure and composition of regional forest. We compared five early successional sites (7-72 months) with five nearby forest remnants. Successional sites had reached 38 and 30%, respectively, of the average basal area and density recorded for the forest understories, but only 5 and 10%, respectively, of the basal area and density of forest overstories. A total of 132 tree species were recorded, 45 at successional and 107 at forest sites. Individuals of tree species with animal-dispersed seeds (57%) were significantly better represented than wind-dispersed (22%) and self-dispersing (21%) species in both successional and forest sites. Successional sites had already recruited 10% of the intermediate and shade-tolerant species that grow in forest remnants. However, only 20 species occurred in both early successional and forest sites, several showing resprouting ability. We conclude that the entry of forest species to the successional process at very early stages and the recruitment of individuals from resprouting may facilitate the recovery of the dry forest in Veracruz. [ABSTRACT FROM AUTHOR]

We examined vegetation structure and woody species diversity in relation to 14 environmental and anthropogenic factors in ten tropical dry forest (TDF) fragments in central Veracruz, Mexico. The basal area of the canopy (30.2 ± 2.11 m2/ha) and understory (1.96 ± 0.12 m2/ha) trees was similar, but density (1,014 ± 104 and 2,532 ± 227 individuals/ha, respectively) differed among sites. We recorded 98 canopy, 77 understory, and 60 seedling species. Richness was 24-45 species per site, Fisher's alpha and Shannon's indices increased with site altitude. Chao Jaccard indices revealed high species turnover, and a consistently higher similarity within the sites at the lowest and within the highest elevation sites. Ordination identified altitude, aspect, slope, water proximity, cattle and trails as significant explanatory variables of species patterns, and showed that sites at lower elevations were clearly separated from the other sites. Environmental heterogeneity alone did not control species diversity distribution, but species were affected by environmental filters at different stages in their life cycle, e.g., water proximity was significant for saplings and seedlings but not for adults. Anthropogenic disturbances act synergistically, e.g., trails played a key role in determining structure and tree diversity patterns. An important finding is that human disturbance diminishes species diversity in this TDF, but sites at lower elevations were more disturbed and less diverse, therefore we need to study how environmental factors would act if there were no anthropogenic disturbance. [ABSTRACT FROM AUTHOR]

Fuelwood extracted from natural forests serves as a principal energy source in rural regions of many tropical countries. Although fuelwood extraction (even low intensities) might strongly impact the structure and species composition of natural forests, long-term studies remain scarce. Here, we estimate the potential long-term impacts (over several hundred years) of such repeated harvesting of single trees on tropical montane cloud forest in central Veracruz, Mexico, by applying a process-based forest growth model. We simulate a wide range of possible harvesting scenarios differing in wood volume harvested and preferred tree species and sizes, and use a set of indicators to compare their impacts on forest size structure and community composition. Results showed that the overall impact on forest structure and community composition increased linearly with the amount of harvested wood volume. Even at low levels of harvesting, forest size structure became more homogeneous in the long term because large old trees disappeared from the forest, but these changes might take decades or even centuries. Although recruitment of harvested species benefited from harvesting, species composition shifted to tree species that are not used for fuelwood. Our results demonstrate that fuelwood extraction can have marked long-term impacts on tropical montane cloud forests. The results also offer the possibility to support the design of management strategies for the natural species-rich forests that achieve a balance between economic needs and ecological goals of the stakeholders. [ABSTRACT FROM AUTHOR]

Vegetation structure of forest edges and type of adjacent field can affect seed and seedling survival patterns of tree species. We investigated acorn removal and seedling survival of Quercus germana and Q. xalapensis in relation to woody plant density across old field-forest gradients with soft and abrupt edges. Experiments were established along four parallel bands located at 40-50 m in the forest, forest and field edges (0-10 m to each side of the border), and 20-30 m in the old field. Within each band, woody plant and acorn density was measured, and four points for acorn and seedling removal experiments were randomly positioned. In each position, 20 acorns or four seedlings were placed. Survival was monitored during one month. In abrupt edges, acorn density was higher along edges than in forest interior. Also, higher acorn removal and seedling mortality were observed in the adjacent old-field whereas acorn and seedling survival was the highest at the edges. Acorn and seedling survival was positively correlated to woody vegetation density. As the vegetation density of field and forest edges grows, abrupt edges develop into soft edges, and they become more hospitable to oak recruitment and then to forest cover expansion. [ABSTRACT FROM AUTHOR]

Leaf demography of four deciduous and five evergreen broadleaved tree species was studied in two replicate tropical montane cloud forest fragments (1250–1400 m elevation) in Veracruz, Mexico. The objectives were to investigate leaf life spans, expansion rates, survivorship curves, specific leaf area (SLA) and nitrogen concentration in tree species of contrasting leaf habits and phytogeographical affinities growing naturally in the same forest type. Tagged leaves were located in the mid forest canopy and were reached with a six-m ladder. A total of 2688 leaves from 78 trees were monitored from bud burst to death. Mean leaf longevity was 8.25 mo for deciduous tree species and 15.0 mo for evergreens. Mean leaf longevity was highly variable among evergreen species which included both the longest ( Magnolia, 36.4 mo) and the shortest ( Hedyosmum, 6.4 mo) values. Patterns of leaf emergence were similar for eight species with a pronounced peak at the beginning of the calendar year. The only exception was Hedyosmum with a multiple flush pattern. More than 50% leaf expansion occurred in less than a month for three deciduous species ( Carpinus, Liquidambar, Quercus) and two evergreens ( Oreopanax and Magnolia), but required more than a month for Clethra (deciduous) and Cinnamomum, Hedyosmum and Turpinia (evergreen). Leaf survivorship curves were similar between the two study sites, but they differed between deciduous and evergreen species. There was no significant difference between leaf habit groups in SLA, leaf area, or nitrogen concentration, however, SLA was inversely correlated with leaf longevity. Arranging the studied taxa from primitive to advanced reaveled that species in more primitive groups have the longest life-spans ( Magnolia, Cinnamomum) and more advanced taxa have the shortest life spans ( Carpinus, Quercus). Phylogenetic relationships between species should be taken into account when studying leaf traits. [ABSTRACT FROM AUTHOR]