Tropical Montane Cloud Forest Research Articles

Loquat (Eriobotrya japonica) fruit consumption and preference by cloud forest birds: Implications for woody native species regeneration

Secondary forests from abandoned shade coffee plantations are commonly found close to Neotropical cities. These peri-urban forests provide important environmental services; however, their abandonment and proximity to the city can promote an increase of exotic species that could potentially change the structure and function of the system by creating novel ecosystems. The loquat (Eriobotrya japonica) is a tree native to Asia and is recognized as a potentially invasive species in the tropical montane cloud forest region of Central Veracruz, Mexico. We analyzed the consumption of and preference for loquat fruits in cloud forest frugivorous birds. In November 2020, we established six feeding stations with camera traps in a peri-urban cloud forest fragment in Xalapa, Mexico. To determine which bird species could consume and disperse E. japonica, fruits of this and another four native species (Psychotria nervosa, Hoffmannia excelsa, Picramnia antidesma, and Xylosma flexuosa) were exposed separately. After 444 camera-days, we recorded eight frugivorous bird species, seven of which consumed E. japonica fruits. Chlorospingus flavopectus was the only species to present a level of loquat fruit consumption greater than that expected by chance. We conducted experiments to assess whether the birds preferred to consume E. japonica fruits compared to those from three native species (Cestrum miradorense, P. nervosa, and X. flexuosa) that were offered simultaneously. All bird species exclusively consumed E. japonica fruits when contrasted against P. nervosa or X. flexuosa. The only native species fruits that were consumed were those of C. miradorense, although the birds also preferred to consume loquat fruits rather than this native species. The loquat therefore represents an important food resource and could act to influence the consumption and dispersal of native cloud forest plant species. The implications for cloud forest management are discussed.

Climate-Affected Australian Tropical Montane Cloud Forest Plants: Metabolomic Profiles, Isolated Phytochemicals, and Bioactivities.

The Australian Wet Tropics World Heritage Area (WTWHA) in northeast Queensland is home to approximately 18 percent of the nation's total vascular plant species. Over the past century, human activity and industrial development have caused global climate changes, posing a severe and irreversible danger to the entire land-based ecosystem, and the WTWHA is no exception. The current average annual temperature of WTWHA in northeast Queensland is 24 °C. However, in the coming years (by 2030), the average annual temperature increase is estimated to be between 0.5 and 1.4 °C compared to the climate observed between 1986 and 2005. Looking further ahead to 2070, the anticipated temperature rise is projected to be between 1.0 and 3.2 °C, with the exact range depending on future emissions. We identified 84 plant species, endemic to tropical montane cloud forests (TMCF) within the WTWHA, which are already experiencing climate change threats. Some of these plants are used in herbal medicines. This study comprehensively reviewed the metabolomics studies conducted on these 84 plant species until now toward understanding their physiological and metabolomics responses to global climate change. This review also discusses the following: (i) recent developments in plant metabolomics studies that can be applied to study and better understand the interactions of wet tropics plants with climatic stress, (ii) medicinal plants and isolated phytochemicals with structural diversity, and (iii) reported biological activities of crude extracts and isolated compounds.

Assessing the impact of land use change on different components of plant diversity in a tropical montane cloud forest of Mexico

Assessing the impact of land use change on different components of plant diversity in a tropical montane cloud forest of Mexico

ERORUN‐STAFOR: A collaborative observatory for the multidisciplinary study of the critical zone processes in a tropical volcanic watershed including a Tropical Montane Cloud Forest

AbstractTropical volcanic islands are biodiversity hotspots where the Critical Zone (CZ) still remains poorly studied. In such steep topographic environments associated with extreme climatic events (cyclones), deployment and maintenance of monitoring equipment is highly challenging. While a few Critical Zone Observatories (CZOS) are located in tropical volcanic regions, none of them includes a Tropical Montane Cloud Forest (TMCF) at the watershed scale. We present here the dataset of the first observatory from the French network of critical zone observatories (OZCAR) located in an insular tropical and volcanic context, integrating a ‘Tropical Montane Cloud Forest’: The ERORUN‐STAFOR observatory. This collaborative observatory is located in the northern part of La Réunion island (Indian Ocean) within the 45.0 km2 watershed of Rivière des Pluies (i.e., Rainfall river) which hosts the TMCF of Plaines des Fougères, one of the best preserved natural habitats in La Réunion Island. Since 2014, the ERORUN‐STAFOR monitoring in collaboration with local partners collected a multidisciplinary dataset with a constant improvement of the instrumentation over time. At the watershed scale and in its vicinity, the ERORUN‐STAFOR observatory includes 10 measurement stations covering the upstream, midstream and downstream part of the watershed. The stations record a total of 48 different variables through continuous (sensors) or periodic (sampling) monitoring. The dataset consists of continuous time series variables related to (i) meteorology, including precipitation, air temperature, relative humidity, wind speed and direction, net radiation, atmospheric pressure, cloud water flux, irradiance, leaf wetness and soil temperature, (ii) hydrology, including water level and temperature, discharge and electrical conductivity (EC) of stream, (iii) hydrogeology, including (ground)water level, water temperature and EC in two piezometers and one horizontally drilled groundwater gallery completed by soil moisture measurements under the canopy. The dataset is completed by periodic time series variables related to (iv) hydrogeochemistry, including field parameters and water analysis results. The periodic sampling survey provides chemical and isotopic compositions of rainfall, groundwater, and stream water at different locations of this watershed. The ERORUN‐STAFOR monitoring dataset extends from 2014 to 2022 with an acquisition frequency from 10 min to hourly for the sensor variables and from weekly to monthly frequency for the sampling. Despite the frequent maintenance of the monitoring sites, several data gaps exist due to the remote location of some sites and instrument destruction by cyclones. Preliminary results show that the Rivière des Pluies watershed is characterized by high annual precipitation (>3000 mm y−1) and a fast hydrologic response to precipitation (≈2 h basin lag time). The long‐term evolution of the deep groundwater recharge is mainly driven by the occurrence of cyclone events with a seasonal groundwater response. The water chemical results support existing hydrogeological conceptual models suggesting a deep infiltration of the upstream infiltrated rainfall. The TMCF of Plaine des Fougères shows a high water storage capacity (>2000% for the Bryophytes) that makes this one a significant input of water to groundwater recharge which still needs to be quantified. This observatory is a unique research site in an insular volcanic tropical environment offering three windows of observation for the study of critical zone processes through upstream‐midstream‐downstream measurements sites. This high‐resolution dataset is valuable to assess the response of volcanic tropical watersheds and aquifers at both event and long‐term scales (i.e., global change). It will also provide insights in the hydrogeological conceptual model of volcanic islands, including the significant role of the TMCFs in the recharge processes as well as the watershed hydrosedimentary responses to extreme climatic events and their respective evolution under changing climatic conditions. All data sets are available at https://doi.org/10.5281/zenodo.7983138.

The Mexican Balsam, Impatiens mexicana Rydb: A Redescription Based on Morphological and Phylogenetic Studies, with an Update of the Current Geographical Range of the Species

Impatiens mexicana is a native balsam restricted to the cloud forests of central and southwest Mexico, which is currently known to exist in four states (Zacatecas, Veracruz, Puebla, and Oaxaca), and is probably threatened by geographic restriction. Morphological and distributional information about this species is still scarce, with only a couple of investigations since its first description in 1910, which means the phylogenetic position of this species has yet to be placed. In order to contribute to knowledge of I. mexicana, morphological and molecular studies were carried out with material collected in the localities of Hidalgo, Veracruz, and Oaxaca, during expeditions from July to October 2021 and in 2022. The specimens selected were measured, photographed, and compared with morphological information from the six American balsams. At the same time, phylogenetic studies were carried out by using two regions of the cpDNA and one of the nrDNA. We report I. mexicana for the first time in Hidalgo state, and identify new registers in the Veracruz and Oaxaca localities, thus increasing the knowledge in its geographic distribution. We also redescribe the Mexican balsam by using new and complementary traits: we note that while the species is morphologically similar to I. capensis, it is distinguished by differences in flower color, the distribution of spot patterns on the upper petal, lower sepal, and lateral petals, and geographic information such as endemic geographic distribution in Mexico’s Tropical Montane Cloud Forest (TMCF). We also carried out phylogenetic analyses by using ITS and ITS + atpb-rbcL, which showed the Mexican balsam was independent from its Asian-American congeners. Interestingly, our genetic distance analyses reveal differences of 0.01–0.16% between I. mexicana and the other North American congeners that use ITS, atpb-rbcL and trnL-F, both independently and as concatenated genes: this low divergence most likely occurred because of the recent diversification of the group. However, both future redescriptions and phylogenetic studies in American species are imperative, as this will enable better discrimination.

Seed Germination Characteristics of a Critically Endangered Evergreen Oak—Quercus marlipoensis (Fagaceae) and Their Conservation Implications

Seed germination is among the most crucial and vulnerable stages in plant life cycles. Quercus marlipoensis is a critically endangered sclerophyllous oak. Only one population has ever been found worldwide in the tropical montane cloud forests of southeastern Yunnan, China, and it has shown difficulties with regeneration. However, its seed biological traits and key restrictive germination factors remain unknown. We investigate the impacts of scarification, temperature, and water potential on the seed germination of Q. marlipoensis. Results show that the seeds show typical epicotyl dormancy. The seed germination increased when removing part or all of the pericarp and part of the cotyledon (one-third and two-thirds). The seeds can germinate at 5 to 30 °C, but the highest T50 was achieved at 25 °C. When the water potential decreased from 0 to −1.0 MPa, the germination rate decreased but the germination time increased. Q. marlipoensis seeds are typically recalcitrant and highly sensitive to moisture loss, but the species can tolerate animal predation and low germination temperatures. The more frequent climatic extremes and droughts in the Indo-China region will severely degrade its natural habitats. Therefore, ex situ conservation to preserve its germplasm and introduce seedlings into a suitable habitat are essential for its conservation management.

The seasonal origins and ages of water provisioning streams and trees in a tropical montane cloud forest

Abstract. Determining the sources of water provisioning streams, soils, and vegetation can provide important insights into the water that sustains critical ecosystem functions now and how those functions may be expected to respond given projected changes in the global hydrologic cycle. We developed multi-year time series of water isotope ratios (δ18O and δ2H) based on twice-monthly collections of precipitation, lysimeter, and tree branch xylem waters from a seasonally dry tropical montane cloud forest in the southeastern Andes mountains of Peru. We then used this information to determine indices of the seasonal origins, the young water fractions (Fyw), and the new water fractions (Fnew) of soil, stream, and tree water. There was no evidence for intra-annual variation in the seasonal origins of stream water and lysimeter water from 1 m depth, both of which were predominantly comprised of wet-season precipitation even during the dry seasons. However, branch xylem waters demonstrated an intra-annual shift in seasonal origin: xylem waters were comprised of wet-season precipitation during the wet season and dry-season precipitation during the dry season. The young water fractions of lysimeter (< 15 %) and stream (5 %) waters were lower than the young water fraction (37 %) in branch xylem waters. The new water fraction (an indicator of water ≤ 2 weeks old in this study) was estimated to be 12 % for branch xylem waters, while there was no significant evidence for new water in stream or lysimeter waters from 1 m depth. Our results indicate that the source of water for trees in this system varied seasonally, such that recent precipitation may be more immediately taken up by shallow tree roots. In comparison, the source of water for soils and streams did not vary seasonally, such that precipitation may mix and reside in soils and take longer to transit into the stream. Our insights into the seasonal origins and ages of water in soils, streams, and vegetation in this humid tropical montane cloud forest add to understanding of the mechanisms that govern the partitioning of water moving through different ecosystems.

Resprouting and foliar functional traits driving the invasiveness of Eriobotrya japonica in a secondary cloud forest

Resprouting of non-native tree invaders is a threat to tropical montane cloud forests and particularly to periurban forests. Resprouting is a common response of trees to disturbance in many ecosystems; however, little is known about the resprouting of woody exotic species with shade-tolerant characteristics that can slowly invade those forests. Furthermore, resprouting of woody invaders is a complex challenge for the control of invasive species since it is a major driver of reinvasion and persistence. In this study, we focus on the resprouting ability of a potential invader, Eriobotrya japonica, in a periurban cloud forest reserve of Xalapa, Mexico. We experimentally cut trees and juveniles in the secondary forest and clipped seedlings at the forest edge, and assessed resprout number, dimensions, emergence position, survival, and leaves per resprout. We then determined foliar traits of the newly produced leaves (leaf area (LA), specific leaf area (SLA), leaf mass area (LMA), leaf dry mass content (LDMC), and thickness). Our results show that resprouting occurred within a month in both tree stumps and clipped seedlings. Resprout survival was 50-80% in stumps, and 63-88% in clipped seedlings. Resprouts were produced mostly in the upper 5 cm below the cut. Leaf number was positively related to dimensions of the longest resprout. Some leaf traits of E. japonica were similar to those of shade-tolerant trees, but there is a combination of strategies since the species presents higher LA and thicker leaves than other native tree species, yet its LMA and LDMC are within the range presented by shade-tolerant species. Eriobotrya japonica is a woody invasive that partly behaves as a shade-tolerant tree and resprouts profusely and rapidly from stumps and clipped seedlings. Its resprouting ability is therefore a key trait by which to explain the invasive potential of this woody species.

Climatic variability and plant functional traits in tropical montane cloud forest refugia along the Trans Mexican Volcanic Belt

Functional traits represent the adaptive responses of plant species to climatic changes. They are an integrative marker of the general environmental conditions at a location. Testing their patterns may help to understand how the functional traits would track these environmental changes of tropical montane cloud forests (TMCFs). These forests are characterized by the constant presence of clouds, and these are among the most threatened ecosystems by climate change worldwide. One of the main TMCF regions in Mexico is the Trans-Mexican Volcanic Belt (TMVB). This region has provided refugia during past climate-change events. We identify three current regions of distribution of TMCF in TMVB, Pacific, Center and Gulf. We used 60 years of climatic information, functional traits and plants databases. We proposed the following aims: to determine whether changes in climatic variation have occurred in the TMVB and how these changes can be related to functional trait variations for dominant tree species across the three TMCF regions, and to know the potential changes as a refuge of the TMCF of the TMVB. We found different rainfall and maximum temperature patterns among and within regions. We identified that the Pacific region forests were characterized by the lowest specific leaf area (SLA), wider leaf thickness and high leaf density, which indicates resources-conservative leaf economics and tolerance to low humidity. Center and Gulf forests were distinguished by the highest SLA, less leaf thickness, and higher leaf density values, which suggests that the leaves of dominant tree species tend to be resources-acquisitive rather than conservative-resources. Finally functional traits were associated with prevailing climatic conditions and suggested that SLA, leaf thickness and leaf density are the main functional traits that could be used to relate them to regional climate. Also, Central and Gulf regions could serve as a refuge for those species of trees demanding humidity.

Contrasting patterns of land-cover change between early and late successional forests in a tropical montane cloud forest area managed under the milpa system

Land cover dynamics (LCD) in areas affected by different management types are hard to predict. Such is the case of tropical montane cloud forest (TMCF) areas in Mexico. The millenary itinerant milpa involves local cyclical deforestation and natural reforestation dynamics with long-lasting fallow periods. Conversely, induced grasslands for cattle, non-traditional maize cultivation with short fallow periods, and sedentary agriculture involve persistent deforestation rates. Also, human density changes could alter LCD. Ignoring such factors may lead to equivocal conclusions. We analyzed LCD using remote sensing analyses with LANDSAT images during two periods (1993–2005, 2005–2014) in a TMCF area in Sierra Norte, Oaxaca, affected by milpas, sedentary agriculture, and grasslands. We divided the study area into six indigenous sub-regions with different human population growth rates (HPG). We identified five land-cover types: mature forests (MF) dominated by TMCF species, early successional pine forests (PF), shrubby fallows (SH), croplands (milpas and more sedentary maize croplands together), and grasslands. We show that: (a) The 1993–2005 period was more variable than the 2005–2014 period, 27 % vs. 21 % of the total area displayed transitions into another class. (b) MF area dominated (277,128 ha), increased from 1993 (64.0 %) to 2014 (67.6 %), and was not statistically associated with HPG. (c) PFs decreased from 27 % in 1993 to 15 % in 2014, and their rate of change was negatively associated with HPG. (d) The total forest area (MF + PF) decreased by 9.3 %. (f) Grasslands, SHs, and croplands fluctuated between periods and sub-regions, but none exceeded 7 % of the total area. (g) Grasslands showed the greatest increase rate, mainly at the expense of forestlands. (h) The grassland and SH increments were positively associated with HPG. The heterogeneity in LCD among periods and sub-regions reveals the relevance of considering temporal and spatial scales within the same region. The persistence of MF and the PF decrease can be ascribed to the disruption of the successional dynamics related to the decline of the traditional milpa enforced by federal and state policies at the beginning of the 21st century, the sedentarization of agriculture, local conservation areas, increases of induced pastures, and human emigration. Although Sierra Norte is an essential reservoir of TMCFs, the decline of the total forest area, particularly secondary forests, is of concern given their roles in resilience and as carbon, culture, and biodiversity reservoirs. Humid mid-elevation areas of Sierra Norte are one of the few examples of mature forest persistence and secondary forest decline.

Moss-associated diatoms from Malaysian montane cloud forest with a description of two new species

Although tropical montane cloud forests (TMCFs) occupy less than half of a percent of the Earth’s land surface, they are the most species-rich and species-dense ecosystems worldwide. Despite numerous studies on various organisms in this environment, diatoms remain a group that is practically unknown. Our work focused on samples of terrestrial bryophytes collected from various substrata at a single site in the Malaysian cloud forest. Despite originating from only one site, the samples contained a high diversity of diatom species and represented a wide range in pH (3.6–6.3). In our study, 62 diatom taxa were observed (8–24 per sample), of which 19 could not be identified with certainty, and were referred to established taxa of similar morphology (as cf. or aff.). Among these however, two species are described as new on the basis of their unique valve morphology: Geissleria bryophila sp. nov. and Eunotia brinchangiana sp. nov.

New Ascomycetes from the Mexican Tropical Montane Cloud Forest.

The tropical montane cloud forest is the most diverse and threatened vegetation type in Mexico. In the last decade, the number of described Ascomycetes species has notably increased, reaching more than 1300 species. This study describes six new species based on their molecular and morphological characteristics. Our results suggest that Mexico has the highest number of described species in the Neotropics. However, many other Mexican lineages still need to be described.

Urban forests support natural regeneration of cloud forest trees and shrubs, albeit with limited occurrence of late-successional species

In highly diverse tropical landscapes, urban and peri-urban forests can play a crucial role as reservoirs of biodiversity. However, urbanization has negatively impacted the natural and anthropogenic vegetation, including the composition, diversity, and functions of urban forests. Tree regeneration plays an essential role in the long-term functionality of forests. Few studies have investigated how natural regeneration occurs in urbanized tropical landscapes, as well as the factors that drive this process. We assessed whether natural regeneration of the tropical montane cloud forest is occurring in urban and peri-urban forests and examined the influence of environmental factors (elevation, annual precipitation, air temperature, canopy cover, and soil physicochemical characteristics) on the regeneration. We used the density and diversity of seedlings, saplings, and juveniles of trees and shrubs in 42 plots across seven urban and peri-urban sites in the Neotropical city of Xalapa, Mexico. In the natural regeneration, 42 tree and 22 shrub species were recorded. Of these species, 83% were native and 17% were non-native. There was a lower abundance of tree (34%) compared to shrub (66%) individuals. Early-successional species were more abundant (51%) than intermediate (35%) and late-successional (14%) species. The numbers of species in the seedling, sapling, and juvenile stages, and the number of early-successional species, were higher in urban than in peri-urban forests. The species richness of both native and non-native taxa was higher in urban than in peri-urban forests (95% CI). We found no significant differences in the density of the young life stages, the density of successional groups, or the density of native and non-native species, between urban and peri-urban forests, probably due to high variability across the sites. Canopy cover had a consistently positive effect on density in most groups. Forest type, soil phosphorus, and soil bulk density also explained densities, except for the late-successional species, where these factors were not statistically significant. The limited richness and density of late-successional species highlight the need to assist the regeneration of this vulnerable group. Understanding natural regeneration patterns can inform the management and restoration of urbanized areas in the distributional regions of tropical montane cloud forest, one of the most important and threatened tropical ecosystems.

Exploring monsoon precipitation signal in the Peruvian tropical montane cloud forest: Andean Walnut wood anatomy plasticity

Summary Andean Walnut (Juglans neotropica Diels-Juglandaceae) is a long-lived, deciduous broadleaf Tropical Montane Cloud Forest (TMCF) tree species native to the Andes Cordillera; nevertheless, it has received limited attention for dendro-quantitative wood anatomical studies. Based on 70 increment cores from 50 Andean Walnut trees at two Peruvian TMCFs, two chronologies (from 1969 to 2020 and from 1964 to 2020) were developed. The xylem vessel parameters assessment allowed us to detect South American Monsoon System (SAMS) precipitation signals in the Andean Walnuts’ wood. Dendro-wood anatomical features can be assessed within an annual growth ring, which allows for assessing intra-annual past and present wood anatomy-function relationships and its climate vulnerability.

Local and Regional Effects of Land-Use Intensity on Aboveground Biomass and Tree Diversity in Tropical Montane Cloud Forests

Local and Regional Effects of Land-Use Intensity on Aboveground Biomass and Tree Diversity in Tropical Montane Cloud Forests

Fine-scale genetic structure of Magnolia iltisiana in forest regeneration sites with a history of selective logging

Background: Selective logging is a frequent practice in the Tropical Montane Cloud Forest which can impact forest regeneration and the genetic makeup of successive generations of trees. The spatial clustering of genetically related individuals, fine-scale genetic structure (FSGS), can develop from the reduction of gene dispersal and the decrease in the number of reproductive individuals at the local scale due to selective logging.
 Questions: In regeneration sites with a history of selective logging, does FSGS differ from a site without such a history? Is FSGS stronger in seedlings and saplings relative to juveniles and adults? Is genetic diversity similar among life stages and sites?
 Studied species: Magnolia iltisiana an endemic tree.
 Study site and dates: Sierra de Manantlan Biosphere Reserve, Jalisco, Mexico.
 2020.
 Methods: We evaluated genetic diversity, genetic structure, and FSGS across four life stages (seedlings, saplings, juveniles, and adults) by genotyping 211 individuals with seven nuclear microsatellite loci in two regeneration and one conserved site.
 Results: We found statistically significant FSGS in the two regeneration sites only for seedlings and saplings, while no evidence of FSGS was detected in the conserved site. No differences in genetic diversity estimates and structure were found among life stages.
 Conclusions: Our study does not suggest an effect of selective logging on genetic diversity on the contrasted conditions and an FSGS pattern only in the earlier stages of the regeneration sites in M. iltisiana.

Are nurse plants useful for facilitating the reintroduction of mid- and late successional tree species in tropical montane cloud forests?

Background: In Mexico, where 50 % of the original Tropical montane cloud forest (TMCF) has been lost due to human activities, the restoration of these forests is essential.
 Questions and/or hypotheses: (1) L. styraciflua favors the survival and growth of Q. germana and M. schiedeana species (2) Are there competitive effects between nurses and beneficiary species? and (3) Is the magnitude of these positive/negative interspecific interactions affected by the canopy cover of nurses?
 Studied species: Liquidambar styraciflua L. (pioneer tree), Magnolia schiedeana Schltdl. (mid-successional tree) and Quercus germana Schltdl. & Cham. (late-successional tree).
 Study site and dates: A fallow in Xilitla, state of San Luis Potosí, Mexico, between 2016 and 2018.
 Methods: Seedling of mid- and late-successional species were transplanted 0.3 m and 2 m away from the stems of pioneer tree (protected and unprotected saplings, respectively). Performance of the species were compared after two years and the effects of canopy cover of pioneer trees.
 Results: Pioneer trees facilitated the establishment probabilities of the mid-and late-successional ones. Increasing canopy cover of pioneer trees enhanced the establishment probabilities of both beneficiary species.
 Conclusions: Joint transplanting of pioneer trees with mid- and late-successional tree seedlings in their close vicinity is a strategy to favor the recovery of the ecosystem.

Adaptation potential of Neotropical montane oaks to drought events: Wood anatomy sensitivity in Quercus delgadoana and Quercus meavei

Abstract Climate and local water availability are major evolutionary drivers of adaptive variation and plasticity in the hydraulic architecture of Tropical Montane Cloud Forest (TMCF) tree species. Between‐year xylem vessel variability is key to understanding the adaptation potential of wood anatomy of trees to drought. How wood anatomical features have been influenced by the typical TMCF climate and how tree species persist in these environments remain open questions, particularly in the context of predicted extreme climate events in the future. Here, we evaluated the effects of changes in temperature, precipitation and evapotranspiration during drought events on ring‐width and anatomical vessel traits (hydraulic diameter, vessel density, vessel grouping index and vulnerability index) for two relict endemic and threatened oak species (Quercus delgadoana and Q. meavei) from a Mexican TMCF. The study species differed in their functional and ecological vessel anatomical traits, and their wood anatomical differences are related to specific environmental requirements. However, the ring‐width indices (RWIs) calculated for these species indicate that both have high resistance and recovery, and thus high resilience to drought events. Ring‐width and vessel functional traits show differences in the between‐year variability of xylem traits associated with the hydraulic efficiency of these oak species, which is crucial to understanding how they avoid drought‐induced embolism and cavitation in vessel conduits. These results provide evidence for the existence of specific hydraulic systems that determine functional wood anatomy in response to climatic variation and drought in the study species. Further research assessing the wood anatomical adaptation to different climatic variables and identifying the xylem functional traits that underlie these adaptations, along with the mechanisms allowing tree species persistence in these environments, is essential to gain insight into the responses of TMCF to future drought events. Read the free Plain Language Summary for this article on the Journal blog.

'Ecophysiological controls on water use of tropical cloud forest trees in response to experimental drought'.

Tropical montane cloud forests (TMCFs) are expected to experience more frequent and prolonged droughts over the coming century, yet understanding of TCMF tree responses to moisture stress remains weak compared to the lowland tropics. We simulated a severe drought in a throughfall reduction experiment (TFR) for two years in a Peruvian TCMF and evaluated the physiological responses several dominant species (Clusia flaviflora, Weinmannia bangii, Weinmannia crassiflora, Prunus integrifolia). Measurements were taken of: i) sap flow ii) diurnal cycles of stem shrinkage, stem moisture variation, and water use; iii) intrinsic water use efficiency (iWUE) estimated from foliar δ13C. In Weinmannia bangii, we used dendrometers and volumetric water content (VWC) sensors to quantify daily cycles of stem water storage. In two years of sap flow (Js) data, we found a threshold response of water use to VPD>1.07kPa independent of treatment, though control trees used more soil water than the treatment trees. The daily decline in water use in the TFR trees was associated with a strong reduction in both morning and afternoon Js rates at a given VPD. Soil moisture also affected the hysteresis strength between Js and VPD. Reduced hysteresis under moisture stress implies that TMCFs are strongly dependent on shallow soil water. Additionally, we suggest that hysteresis can serve as a sensitive indicator of environmental constraints on plant function. Finally, six months into the experiment, the TFR treatment significantly increased iWUE in all study species. Our results highlight the conservative behavior of TMCF tree water use under severe soil drought and elucidates physiological thresholds related to VPD and its interaction with soil moisture. The observed strongly isohydric response likely incurs a cost to the carbon balance of the tree, and reduces overall ecosystem carbon uptake.

Environmental valuation of hydro-environmental services of the Tropical Montane Cloud Forest

Environmental externalities are just one class of externalities (or external effects). They are not more important than any other type of economic externalities, but it would not be possible to find rational arguments to justify that they are less so. If more complex and therefore better decisions are to be taken, these externalities should be duly quantified and incorporated in the framework of an economic analysis of public or private decisions of society. In that case, they can be accounted for as costs of our decisions. Environmental economics has different environmental valuation methods to include ecosystems and its dynamics into an economic system. The most applied methods are contingent valuation, hedonic prices, and travel cost. These methods may be used as a guide to formulate public policies to protect the environment and have an efficient management. The present research is an analysis for hydro-environmental services (recreational services) of the tropical montane cloud forest (La Granada waterfall) of Coatepec due to the increasing risks caused by human activity. Therefore, the travel cost method will be applied to estimate the economic value associated with the ecosystem. This method applies conventional empirical techniques used by economists to estimate economic values based on market prices. The findings showed different travel costs for every chosen zone and a consumer surplus of $47.10 MXN and an estimated yearly value of $70,645 MXN.