Buzz-Pollination in a Tropical Montane Cloud Forest: Compositional Similarity and Plant-Pollinator Interactions.

Buzz pollination

news and update book review Headwaters in the clouds Tropical Montane Cloud Forests, by L. A. Bruijnzeel, F. N. Scatena & L. S. Hamilton (editors), 2011, Cambridge University Press, 768 pp. £65 (Hardback) ISBN: 9780521760355; http:// www.cambridge.org/ Tropical Montane Cloud Forests (TMCFs) are gaining in scientific popularity since a first international symposium on this ecosystem was held in Puerto Rico in 1993. The promotion of the meeting by the UNESCO International Hydrological Programme illustrates a far-reaching effect of cloud forests: they act as water collectors for tropical forelands. TMCFs also harbour extraordinarily many plant species, contributing to outstanding positions in each of the five hottest spots of plant diversity. Why edit yet another comprehensive opus on TMCFs, after several previous fundamental works, despite their encompassing under 0.15% of the global terrestrial surface? The answer is clear to those who know this biome: there hardly exists a more fascinating environment than exuberant, moss-covered cloud forests, often called elfin forests due to their mystical appearance. They form highly complex ecosystems, which on different continents show divergent biocœnoses because of their fragmentation and isolated position within distinct tropical mountains in the Neotropics and, to a lesser degree, in the Paleotropics, and in a few cases even on Pacific islands. This book deals with general features of TMCFs (12 chapters) and contains examples from Middle America (21), South America (19), Southeast Asia (10), Africa (5) and Oceania / Australia (5). Most contributions result from a conference in Hawaii in 2004. A first glance reveals a nearly complete thematic spectrum. The book is subdivided into seven sections with a total of 72 chapters. The first part contains general features of TMCFs. Altitudinal distributions are presented in an introductory chapter, though integrative references to surrounding belts are missing. A useful GIS-based modelling approach provides instructive data on TMCF resources and losses including tables on their dimensions and distributions. Interestingly, Indonesia and Congo rank first in national extent, with neotropical countries falling lower down. A climate chapter is based on a dataset of 477 weather stations in cloud forest sites. Many graphs present vast dot clouds of data from stations between 200 and 5,000 m asl, which raises the confusing suspicion that TMCFs occur in regions of extremely dissimilar climates. A short but informative chapter on changes in fog precipitation should have been part of a later section, as also applies to one on epiphytism. Comments on global and local soil variations, as well as on nutrient cycling and limitation in TMCFs, provide convincing and compact estimations. Coloured maps of TMCF distribution highlight their restricted extent and natural fragmentation on a global scale. The subsequent and sadly brief section on regional aspects of floristic and faunistic diversity contains fascinating information from all TMCF- bearing continents. The range extends from research on epiphyte-diversity on solitary trees (up to 4,806 individuals of 114 vascular plant species on one single fig tree!) to potential and actual distribution patterns of the mountain tapir and Andean bear. The only point of criticism is that in a book on a biological realm this section could have been broader. The third section on hydrometeorology covers a broad remit since fog, rain and their interception are decisive triggers for the formation of TMCFs. Several parts display the importance of potential evaporation and irradiation as driving forces for the variable character of forests. Additionally, the degrees of litter mineraliation and soil acidity become crucial causes of ecological peculiarities. The contributions vary from rather specialist methodical content (e.g. measuring interception, usage of stable isotopes for diagnoses of precipitation origins) to comments on the water frontiers of biogeography 4.1, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society

The potential negative impacts of global climate change on tropical montane cloud forests

Clouds persistently engulf many tropical mountains at elevations cool enough for clouds to form, creating isolated areas with frequent fog and mist. Under these isolated conditions, thousands of unique species have evolved in what are known as tropical montane cloud forests (TMCF) and páramo. Páramo comprises a set of alpine ecosystems that occur above TMCF from about 11° N to 9° S along the Americas continental divide. TMCF occur on all continents and island chains with tropical climates and mountains and are increasingly threatened by climate and land-use change. Climate change could impact a primary feature distinguishing these ecosystems, cloud immersion. But where and in what direction cloud immersion of TMCF and páramo will change with climate are fundamental unknowns. Prior studies at a few TMCF sites suggest that cloud immersion will increase in some places while declining in others. Other unknowns include the extent of deforestation in protected and unprotected cloud forest climatic zones, and deforestation extent compared with projected climate change. Here we use a new empirical approach combining relative humidity, frost, and novel application of maximum watershed elevation to project change in TMCF and páramo for Representative greenhouse gas emissions Concentration Pathways (RCPs) 4.5 and 8.5. Results suggest that in <25–45 yr, 70–86% of páramo will dry or be subject to tree invasion, and cloud immersion declines will shrink or dry 57–80% of Neotropical TMCF, including 100% of TMCF across Mexico, Central America, the Caribbean, much of Northern South America, and parts of Southeast Brazil. These estimates rise to 86% of Neotropical TMCF and 98% of páramo in <45–65 yr if greenhouse gas emissions continue rising throughout the 21st century. We also find that TMCF zones are largely forested, but some of the most deforested areas will undergo the least climate change. We project that cloud immersion will increase for only about 1% of all TMCF and in only a few places. Declines in cloud immersion dominate TMCF change across the Neotropics.

Tropical montane cloud forests are known for their unique biodiversity and their critical role in sustaining ecosystem services; however, approximately 50% of their original cover in Mexico was estimated to have been lost by 1998. The Mexican ecoregion that supports these ecosystems experienced one of the highest rates of deforestation between 2001 and 2021. Thus, a more recent evaluation of Mexico's cloud forests is required. There is limited data on the landscape structure of cloud forests in Mexico, despite the possible application of landscape factors in conservation planning. Here, we estimated the average total area, number of patches, effective mesh size, total edge, and the shape of mixed forests that was present in 2020 within polygons of cloud forests defined in 1999 by Mexico's National Commission for the Use and Knowledge of Biodiversity (CONABIO for its acronym in Spanish). We estimated land cover using data from the North American Land Change Monitoring System, which classifies cloud forests as mixed forests. We found that eight out of the 109 polygons have no mixed forests and that an average of 49% of the 1,768,914 ha of cloud forests polygons are now covered by mixed forests distributed across 13 states. Additionally, within the remaining 101 polygons that do contain this type of vegetation, mixed forest is distributed on average across 140 patches (range = 1-1,473); 80% of these forests have very low effective mesh size values; 90% of them have low total edge values (<2,000 km); and their shapes tend to be uniformly distributed. Furthermore, most of cloud forest polygons are located outside of federal protected areas. Overall, our results suggest that the remaining Mexican cloud forests are extremely vulnerable and fragmented and that their extent has steadily declined since 1999. To ensure the survival of Mexican cloud forests, it will be crucial to prioritize high-diversity areas, strengthen protection in critical zones, establish ecological corridors, encourage sustainable practices, and actively engage local communities. This study highlights the complex issues and inherent heterogeneity that characterize cloud forest ecosystems in Mexico and provides crucial insights for conservation.

Background and Aims: Tropical montane cloud forest (TMCF) is one of the most threatened ecosystems worldwide. Natural protected areas (NPAs) have been established to prevent further loss of these forests in Mexico. To assess whether management activities temporally impact the biodiversity of NPAs, the use of indicator groups, such as some groups of macromycetes, has been proposed. The aim of this study was to assess the temporal shifts over the last 36 years in the alpha, beta, and gamma diversity of a Xylaria assemblage in a NPA of TMCF as a result of anthropogenic management activities.Methods: Collections were performed in a 31 ha NPA of TMCF in Xalapa, Veracruz, Mexico, during three 10 year and one six year sampling periods (1980-2016), taking into account specimens deposited in the herbarium XAL and collections performed by the authors, mainly in the two latter periods. Species number and abundance, compositional similarity, species turnover, and gamma diversity of assemblages were determined and compared among the sampling periods.Key results: Of 3480 individuals belonging to 30 Xylaria species, the most abundant species were X. scruposa, X. anisopleura, X. berteroi, X. cubensis, X. feejeensis, X. albocinctoides, and X. arbuscula. The inventory completeness was 99.9%. Species richness varied from six (1990-1999) to 28 species (2010-2016). Jaccard index separated two assemblage clusters. Gamma diversity was more influenced by beta diversity than alpha diversity.Conclusions: Xylaria assemblages are a useful bioindicator group and monitoring them over time may provide information about the impacts of management on TMCF ecosystems. Temporal dynamics of these assemblages partly depend on the historically implemented management in the NPA of TMCF. Effective conservation outcomes for TMCF will only be achieved if current management strategies are maintained and integrated into the long-term management framework of NPAs containing TMCF.

Active versus passive restoration: Recovery of cloud forest structure, diversity and soil condition in abandoned pastures

ABSTRACTAdaptations that reduce water retention on leaf surfaces may increase photosynthetic capacity of cloud forests because carbon dioxide diffuses slower in water than air. Leaf water repellency was examined in three distinct ecosystems to test the hypothesis that tropical montane cloud forest species have a higher degree of leaf water repellency than species from tropical dry forests and species from temperate foothills‐grassland vegetation. Leaf water repellency was measured by calculating the contact angle of the leaf surface and the line tangent to a water droplet through the point of contact on the adaxial and the abaxial surface. Leaf water repellency was significantly different between the three study areas. The hypothesis that leaf water repellency is higher in cloud forest species than tropical dry forests and temperate foothills‐grassland vegetation was not confirmed in this study. Leaf water repellency was lower for cloud forest species (adaxial surface = 50.8°; abaxial surface = 82.9°) than tropical dry forest species (adaxial surface = 74.5°; abaxial surface = 87.3°) and temperate foothills‐grassland species (adaxial surface = 77.6°; abaxial surface = 95.8°). The low values of leaf water repellency in cloud forest species may be influenced by presence of epiphylls and loss of epicuticular wax on the leaf surfaces.

Successional changes in soil, litter and macroinvertebrate parameters following selective logging in a Mexican Cloud Forest

Abstract: Unplanned selective logging for charcoal and firewood is a common practice in tropical montane cloud forest (TMCF), a high priority ecosystem for biodiversity conservation at the global scale. However, limited information is available regarding the impact of such logging on forest regeneration. We evaluated the abundance and composition of tree regeneration in four TMCF sites subject to traditional selective logging in southern Mexico. At each site, we calculated a tree extraction index based on the number of stumps, logs and charcoal kilns and established six 200 m2 plots where the abundance of adult, sapling and seedling trees were recorded and canopy cover estimated. Based on the extraction index and estimated basal area values, two sites each were classified as being of low (L) and high (H) logging intensity; the extraction index was three times lower in L (7.5 and 9.2) than in H (35 and 35) sites, while basal area was significantly higher in L than in H sites (80.2 ± 10.2 vs. 41.9 ± 4.96 m2 ha-1, respectively). No significant differences were found among sites in terms of canopy cover, diameter and density of adult trees or in the density of saplings and seedlings (0.72 individuals m-2). In all sites, species of intermediate shade-tolerance dominated the regeneration (76%), followed by the shade-tolerant (23%) and pioneer (1%) species. Regeneration of Quercus spp. (four species) dominated at all sites (50.5%); this is a group of particular interest to the local communities because of its utility for firewood and charcoal. The similarity in composition between adult and regenerating tree species was relatively high in all of the sites (Morisita-Horn Index L1=0.86, L2=0.64, H1=0.69 and H2=0.71). These results indicate that, under the evaluated selective logging intensities, TMCF can sustain sufficient regeneration of Quercus spp. and thus presents an opportunity for sustainable management. The legacy effects of traditional selective logging on TMCF tree regeneration are discussed.

Tropical montane cloud forests (TMCFs) are characterized by a unique set of biological and hydroclimatic features, including frequent and/or persistent fog, cool temperatures, and high biodiversity and endemism. These forests are one of the most vulnerable ecosystems to climate change given their small geographic range, high endemism and dependence on a rare microclimatic envelope. The frequency of atmospheric water deficits for some TMCFs is likely to increase in the future, but the consequences for the integrity and distribution of these ecosystems are uncertain. In order to investigate plant and ecosystem responses to climate change, we need to know how TMCF species function in response to current climate, which factors shape function and ecology most and how these will change into the future. This review focuses on recent advances in ecophysiological research of TMCF plants to establish a link between TMCF hydrometeorological conditions and vegetation distribution, functioning and survival. The hydraulic characteristics of TMCF trees are discussed, together with the prevalence and ecological consequences of foliar uptake of fog water (FWU) in TMCFs, a key process that allows efficient acquisition of water during cloud immersion periods, minimizing water deficits and favouring survival of species prone to drought-induced hydraulic failure. Fog occurrence is the single most important microclimatic feature affecting the distribution and function of TMCF plants. Plants in TMCFs are very vulnerable to drought (possessing a small hydraulic safety margin), and the presence of fog and FWU minimizes the occurrence of tree water deficits and thus favours the survival of TMCF trees where such deficits may occur. Characterizing the interplay between microclimatic dynamics and plant water relations is key to foster more realistic projections about climate change effects on TMCF functioning and distribution.

Tropical montane cloud forests are among the most vulnerable terrestrial ecosystems to climate change(1-3) owing to their restricted climatic requirements and their narrow and fragmented distribution(4). Although 12% of Mexican cloud forest is protected, it is not known whether reserves will ensure the persistence of the ecosystem and its endemic species under climate change. Here, we show that 68% of Mexico's cloud forest could vanish by 2080 because of climate change and more than 90% of cloud forest that is protected at present will not be climatically suitable for that ecosystem in 2080. Moreover, if we assume unprotected forests are cleared, 99% of the entire ecosystem could be lost through a combination of climate change and habitat loss, resulting in the extinction of about 70% of endemic cloud forest vertebrate species. Immediate action is required to minimize this loss-expansion of the protected-area estate in areas of low climate vulnerability is an urgent priority. Our analysis indicates that one key area for immediate protection is the Sierra de Juarez in Oaxaca. This area supports many endemic species and is expected to retain relatively large fragments of cloud forest despite rapid climate change.

Fitting rainfall interception models to forest ecosystems of Mexico

There have been conflicting findings on hydrological dynamics in tropical montane cloud forests (TMCFs)—attributed to differences in climate, altitude, topography, and vegetation. We contribute another observation-based comparison between a TMCF (8.53 ha; 1906 m.a.s.l.) and a tropical lowland rainforest (TLRF) (5.33 ha; 484 m.a.s.l.) catchment in equatorial Sabah, Malaysian Borneo. In each catchment, a 90° v-notch weir was established at the stream’s outlet and instrumented with a water-level datalogger that records data at 10-min intervals (converted to discharge). A nearby meteorological station records rainfall at the same 10-min intervals via a tipping bucket rain gauge connected to a datalogger. Over five years, 91 and 73 storm hydrographs from a TMCF and a TLRF, respectively, were extracted and compared. Various hydrograph metrices relating to discharge and flashiness were compared between the TMCF and TLRF while controlling for event rainfall, rainfall intensity, and antecedent moisture. Compared to the TLRF, storm-event runoff in the TMCF was up to 169% higher, reflecting the saturated conditions and tendency for direct runoff. Instantaneous peak discharge was also higher (up to 6.6x higher) in the TMCF. However, despite high moisture and steep topography, stream responsiveness towards rainfall input was lower in the TMCF, which we hypothesise was due to its wide and short catchment dimensions. Baseflow was significantly correlated with API20, API10, and API7. Overall, we found that the TMCF had higher runoff, but higher moisture condition alone may not be sufficient to govern flashiness.

Tropical montane cloud forests (TMCF) host high biodiversity and endemicity and are severely threatened by illegal selective logging, deforestation, fragmentation and climate change. The fragments of TMCF present high heterogeneity over short spatial intervals and a regional forest restoration approach must therefore incorporate seedling performance throughout the TMCF elevation range. We examined early seedling establishment in 12 endangered and valuable TMCF species in the understory of unplanned selectively logged TMCF and assessed the influence of elevation and canopy cover on seedling performance. Tree seedlings (10-18 mo-old) were transplanted into restoration plantings in 6 forest sites along an elevation range (1,250 to 1,995 m) in Veracruz, Mexico. In each forest, 30 seedlings per species were planted and their survival and relative growth rates in height (RGRh) and basal stem diameter (RGRd) recorded, along with canopy cover. Survival was high for all species after one year (81.1 to 99.4%) and was unaffected by elevation. Canopy cover positively affected the survival probability of 3 species. Both RGRh and RGRd decreased at lower elevations in 4 species; however, overall growth rates were positive. Our results indicate a positive early seedling establishment response in the evaluated tree species under the TMCF canopy (66-97% of canopy cover).