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"cloud forest"
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The forest in the clouds
Describes some of the exotic plants and animals that live in the cloud forest of Costa Rica, and discusses some environmental threats faced by this region.
Book
The variation of productivity and its allocation along a tropical elevation gradient
Why do forest productivity and biomass decline with elevation? To address this question, research to date generally has focused on correlative approaches describing changes in woody growth and biomass with elevation.
We present a novel, mechanistic approach to this question by quantifying the autotrophic carbon budget in 16 forest plots along a 3300m elevation transect in Peru.
Low growth rates at high elevations appear primarily driven by low gross primary productivity (GPP), with little shift in either carbon use efficiency (CUE) or allocation of net primary productivity (NPP) between wood, fine roots and canopy. The lack of trend in CUE implies that the proportion of photosynthate allocated to autotrophic respiration is not sensitive to temperature. Rather than a gradual linear decline in productivity, there is some limited but nonconclusive evidence of a sharp transition in NPP between submontane and montane forests, which may be caused by cloud immersion effects within the cloud forest zone. Leaf-level photosynthetic parameters do not decline with elevation, implying that nutrient limitation does not restrict photosynthesis at high elevations.
Our data demonstrate the potential of whole carbon budget perspectives to provide a deeper understanding of controls on ecosystem functioning and carbon cycling.
Journal Article
The search for Olinguito : discovering a new species
\"Learn about the olinguito, one of the most recently discovered mammal species, the discovery thereof, and the 'cloud forests' in which they live\"-- Provided by publisher.
Book
Local and Regional Effects of Land-Use Intensity on Aboveground Biomass and Tree Diversity in Tropical Montane Cloud Forests
The quantity and spatial patterns of aboveground biomass (AGB) are expected to correlate with ecosystem structure and biodiversity across biomes. However, the local and regional variations in the strength of such relationships remain poorly understood partly due to the influence of ecosystem disturbances, such as land-use change. Here, we quantified AGB in tropical montane cloud forest (TMCF) in southern Mexico and analyzed its distribution patterns at local and regional scales. Specifically, we investigated how land use and environmental factors (that is, topography and climate) influence AGB spatial patterns and the relationship between forest structure, AGB, and tree species diversity across forests with different levels of disturbance, using 160 plots from the Mexican National Forest Inventory (FI) database. Our results show that AGB (averaging 137 Mg ha−1) is strongly influenced by variations in forest structure such as stand basal area and the density of large trees, with a weak but positive relation with tree species diversity. AGB increased with elevation and slope and decreased with very high levels of precipitation and land-use intensity, suggesting that spatial variation in AGB across the region can be best predicted by the interactive effects of land use and environmental factors, with land use having a larger role. Our results challenge general assumptions about the structural and compositional properties of montane forest ecosystems and emphasize the need to explicitly include interactions between environmental and human drivers when analyzing changes in AGB and devising sustainable management plans.
Journal Article
Foliar uptake of fog water and transport belowground alleviates drought effects in the cloud forest tree species, Drimys brasiliensis (Winteraceae)
Foliar water uptake (FWU) is a common water acquisition mechanism for plants inhabiting temperate fog-affected ecosystems, but the prevalence and consequences of this process for the water and carbon balance of tropical cloud forest species are unknown.
We performed a series of experiments under field and glasshouse conditions using a combination of methods (sap flow, fluorescent apoplastic tracers and stable isotopes) to trace fog water movement from foliage to belowground components of Drimys brasiliensis. In addition, we measured leaf water potential, leaf gas exchange, leaf water repellency and growth of plants under contrasting soil water availabilities and fog exposure in glasshouse experiments to evaluate FWU effects on the water and carbon balance of D. brasiliensis saplings.
Fog water diffused directly through leaf cuticles and contributed up to 42% of total foliar water content. FWU caused reversals in sap flow in stems and roots of up to 26% of daily maximum transpiration. Fog water transported through the xylem reached belowground pools and enhanced leaf water potential, photosynthesis, stomatal conductance and growth relative to plants sheltered from fog.
Foliar uptake of fog water is an important water acquisition mechanism that can mitigate the deleterious effects of soil water deficits for D. brasiliensis.
Journal Article
hydroclimatic and ecophysiological basis of cloud forest distributions under current and projected climates
BackgroundTropical 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.ScopeThis 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.ConclusionsFog 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.
Journal Article
Cloud forest trees with higher foliar water uptake capacity and anisohydric behavior are more vulnerable to drought and climate change
Many tropical montane cloud forest (TMCF) trees are capable of foliar water uptake (FWU) during leaf-wetting events. In this study, we tested the hypothesis that maintenance of leaf turgor during periods of fog exposure and soil drought is related to species’ FWU capacity.
We conducted several experiments using apoplastic tracers, deuterium labeling and leaf immersion in water to evaluate differences in FWU among three common TMCF tree species. We also measured the effect of regular fog exposure on the leaf water potential of plants subjected to soil drought and used these data to model species’ response to long-term drought.
All species were able to absorb water through their leaf cuticles and/or trichomes, although the capacity to do so differed between species. During the drought experiment, the species with higher FWU capacity maintained leaf turgor for a longer period when exposed to fog, whereas the species with lower FWU exerted tighter stomatal regulation to maintain leaf turgor. Model results suggest that without fog, species with high FWU are more likely to lose turgor during seasonal droughts.
We show that leaf-wetting events are essential for trees with high FWU, which tend to be more anisohydric, maintaining leaf turgor during seasonal droughts.
Journal Article
Variation in the resilience of cloud forest vascular epiphytes to severe drought
Epiphytes are common in tropical montane cloud forests (TMCFs) and play many important ecological roles, but the degree to which these unique plants will be affected by changes in climate is unknown. We investigated the drought responses of three vascular epiphyte communities bracketing the cloud base during a severe, El Niño-impacted dry season.
Epiphytes were instrumented with sap flow probes in each site. Leaf water potential and pressure–volume curve parameters were also measured before and during the drought. We monitored the canopy microclimate in each site to determine the drivers of sap velocity across the sites.
All plants greatly reduced their water use during the drought, but recovery occurred more quickly for plants in the lower and drier sites. Plants in drier sites also exhibited the greatest shifts in the osmotic potential at full saturation and the turgor loss point.
Although all individuals survived this intense drought, epiphytes in the cloud forest experienced the slowest recovery, suggesting that plants in the TMCF are particularly sensitive to severe drought. Although vapor pressure deficit was an important driver of sap velocity in the highest elevation site, other factors, such as the volumetric water content of the canopy soil, were more important at lower (and warmer) sites.
Journal Article
Amphibian species and functional diversity as indicators of restoration success in tropical montane forest
Tropical forest restoration is increasingly seen as an activity that may counteract or reduce biodiversity loss. However, few studies monitor fauna or consider measures of functional diversity to assess restoration success. We assessed the effect of a tropical montane forest restoration program on species and functional diversity, using amphibians as the target group. We compared amphibian assemblages in three types of land use: restoration areas, tropical montane cloud forest (TMCF; reference ecosystem) and cattle pastures (degraded ecosystem) in southern Mexico. We also described microclimate, microhabitat heterogeneity, woody vegetation structure and diversity for each type of land use, and their relationship to amphibian species and functional diversity. Compared to TMCF, restoration areas had similar environmental conditions. However, amphibian species richness was similar in the three types of land use and abundance was lower in the restoration areas. In TMCF, the amphibian assemblage was dominated by forest-specialist species, the pastures by generalist species, and the restoration areas by a combination of both species types. Interestingly, functional richness, functional evenness and functional divergence did not vary with land use, though the number of functional groups in restoration areas and TMCF was slightly higher. Overall, the results suggest that after seven years, active restoration provided habitat heterogeneity and recovered woody vegetation capable of maintaining amphibian species and functional groups similar to those inhabiting TMCF. Forest fragments adjacent to restoration areas seem to facilitate fauna recolonization and this emphasizes the importance of the conservation of the reference ecosystems to achieving restoration success.
Journal Article
Nutrient limitation in rainforests and cloud forests along a 3,000-m elevation gradient in the Peruvian Andes
We report results from a large-scale nutrient fertilization experiment along a \"megadiverse\" (154 unique species were included in the study) 3,000-m elevation transect in the Peruvian Andes and adjacent lowland Amazonia. Our objectives were to test if nitrogen (N) and phosphorus (P) limitation shift along this elevation gradient, and to determine how an alleviation of nutrient limitation would manifest in ecosystem changes. Tree height decreased with increasing elevation, but leaf area index (LAI) and diameter at breast height (DBH) did not vary with elevation. Leaf N:P decreased with increasing elevation (from 24 at 200 m to 11 at 3,000 m), suggesting increased N limitation and decreased P limitation with increasing elevation. After 4 years of fertilization (N, P, N + P), plots at the lowland site (200 m) fertilized with N + P showed greater relative growth rates in DBH than did the control plots; no significant differences were evident at the 1,000 m site, and plots fertilized with N at the highest elevation sites (1,500, 3,000 m) showed greater relative growth rates in DBH than did the control plots, again suggesting increased N constraint with elevation. Across elevations in general N fertilization led to an increase in microbial respiration, while P and N + P addition led to an increase in root respiration and corresponding decrease in hyphal respiration. There was no significant canopy response (LAI, leaf nutrients) to fertilization, suggesting that photosynthetic capacity was not N or P limited in these ecosystems. In sum, our study significantly advances ecological understanding of nutrient cycling and ecosystem response in a region where our collective knowledge and data are sparse: we demonstrate N limitation in high elevation tropical montane forests, N and P co-limitation in lowland Amazonia, and a nutrient limitation response manifested not in canopy changes, but rather in stem and belowground changes.
Journal Article