An official website of the United States government
Abstract AimTo examine the climatic and biogeographic drivers of plant trait variation across Caribbean tropical dry forests, a system characterised by high rates of plant endemism despite low moisture availability, high rainfall variability and persistent exposure to hurricanes. LocationCaribbean tropical dry forests. TaxonWoody plants. MethodsWe used a database of 572 woody vegetation plots spanning across the Caribbean, including Florida. We then extracted seed mass, specific leaf area and wood density from global trait databases. We supplemented additional trait data from herbaria collections and calculated phylogenetic imputation of traits. Furthermore, we calculated presence–absence community means and functional diversity and correlated these metrics with bioclimatic variables in addition to island and dry forest area using generalised additive models. ResultsDespite occurring in climatically distinct regions, Caribbean tropical dry forests are functionally similar, and the trait space of many dry forests are nested within the functional space of others. In line with island biogeographic theory, island area, dry forest area and island isolation were correlated with functional diversity. Although temperature and precipitation were important determinants of trait variation and functional diversity, environmental variables differently impacted trait variation and the variance explained was generally low. Main ConclusionsThe high functional overlap among Caribbean dry forests is remarkable given the broad climatic gradient across these islands. High functional overlap suggests that environmental and biogeographic filters constrain plant form and function in these intrinsically fascinating systems. The trait space of these insular dry forest systems points to dispersal‐limitation, in addition to high temperature and water limitations, and favouring persistence strategies to withstand high frequency hurricane disturbance.
more »
« less
Trait‐based signatures of cloud base height in a tropical cloud forest
PremiseClouds have profound consequences for ecosystem structure and function. Yet, the direct monitoring of clouds and their effects on biota is challenging especially in remote and topographically complex tropical cloud forests. We argue that known relationships between climate and the taxonomic and functional composition of plant communities may provide a fingerprint of cloud base height, thus providing a rapid and cost‐effective assessment in remote tropical cloud forests. MethodsTo detect cloud base height, we compared species turnover and functional trait values among herbaceous and woody plant communities in an ecosystem dominated by cloud formation. We measured soil and air temperature, soil nutrient concentrations, and extracellular enzyme activity. We hypothesized that woody and herbaceous plants would provide signatures of cloud base height, as evidenced by abrupt shifts in both taxonomic composition and plant function. ResultsWe demonstrated abrupt changes in taxonomic composition and the community‐ weighted mean of a key functional trait, specific leaf area, across elevation for both woody and herbaceous species, consistent with our predictions. However, abrupt taxonomic and functional changes occurred 100 m higher in elevation for herbaceous plants compared to woody ones. Soil temperature abruptly decreased where herbaceous taxonomic and functional turnover was high. Other environmental variables including soil biogeochemistry did not explain the abrupt change observed for woody plant communities. ConclusionsWe provide evidence that a trait‐based approach can be used to estimate cloud base height. We outline how rises in cloud base height and differential environmental requirements between growth forms can be distinguished using this approach.
more »
« less
- Award ID(s):
- 1833358
- PAR ID:
- 10377184
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 107
- Issue:
- 6
- ISSN:
- 0002-9122
- Page Range / eLocation ID:
- p. 886-894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract High alpine regions are threatened but understudied ecosystems that harbor diverse endemic species, making them an important biome for testing the role of environmental factors in driving functional trait‐mediated community assembly processes. We tested the hypothesis that plant community assembly along a climatic and elevation gradient is influenced by shifts in habitat suitability, which drive plant functional, phylogenetic, and spectral diversity. In a high mountain system (2400–3500 m) Región Metropolitana in the central Chilean Andes (33°S, 70°W). We surveyed vegetation and spectroscopic reflectance (400–2400 nm) to quantify taxonomic, phylogenetic, functional, and spectral diversity at five sites from 2400 to 3500 m elevation. We characterized soil attributes and processes by measuring water content, carbon and nitrogen, and net nitrogen mineralization rates. At high elevation, colder temperatures reduced available soil nitrogen, while at warmer, lower elevations, soil moisture was lower. Metrics of taxonomic, functional, and spectral alpha diversity peaked at mid‐elevations, while phylogenetic species richness was highest at low elevation. Leaf nitrogen increased with elevation at the community level and within individual species, consistent with global patterns of increasing leaf nitrogen with colder temperatures. The increase in leaf nitrogen, coupled with shifts in taxonomic and functional diversity associated with turnover in lineages, indicate that the ability to acquire and retain nitrogen in colder temperatures may be important in plant community assembly in this range. Such environmental filters have important implications for forecasting shifts in alpine plant communities under a warming climate.more » « less
-
Abstract QuestionsIt is frequently reported that overstocking of camels, cattle and goats is degrading theAnogeissuscloud forest, which is endemic to a 200‐km stretch of coastal mountains in southern Arabia. However, livestock impacts on the vegetation have not been assessed. Furthermore, we have a limited understanding of the impacts of large‐bodied browsing livestock, such as camels, in woodland and forest rangelands. Therefore, in this study, we examine the effects of livestock browsing on the species composition, density, and phytomorphology of woody vegetation in theAnogeissuscloud forests in the Dhofar Mountains of Oman. LocationData were collected at 30 sites in the Jabal Qamar mountain range in western Dhofar, Oman. MethodsThe point‐centred quarter method was used to sample the composition, density and structure of woody vegetation. Constrained correspondence analysis was used to quantify the effects of livestock browsing on woody plant species composition, whilst effects on plant density were analysed using mixed‐effects models. Standardised major axis regression was used to examine differences in height–diameter allometry (stunting) under different stocking rates. ResultsFog density, topographic position and long‐term stocking rates were found to be important factors affecting woody species composition. We found lower species diversity and plant density, and higher frequencies of unpalatable species, under higher stocking rates. Juveniles showed a stronger response to stocking rates than adults, and several common species exhibited stunted morphology under high stocking rates. ConclusionsBrowsing by large‐bodied livestock, such as camels and cattle, can substantially alter the species composition, structure, and phytomorphology of woody vegetation in semi‐arid woodlands and forests. Juveniles are particularly susceptible to browsing which alters woody vegetation demography and inhibits regeneration potential. Our results support previous suggestions of overstocking in Dhofar and highlight the importance of swift measures to reduce livestock browsing pressure in theAnogeissuscloud forests.more » « less
-
Abstract QuestionsUrban ecosystems present an opportunity to study ecological communities in the context of unprecedented environmental change. In the face of urban land conversion, ecologists observe new patterns of species composition, dominance, behaviour and dispersal. We propose a hypothetical socioeconomic template that describes a gradient in human investment in community composition to aid in organizing the human role in shaping urban biodiversity. We asked: (1) what is the relative magnitude of taxonomic and functional turnover of urban woody plant communities across different land‐use types; and (2) do land uses exhibiting higher intensity of human management of biodiversity support higher turnover over those with less human influence? LocationBaltimore,MD,USA(39°17′ N, 76°38′ W). MethodsWe examined patterns in woody plant biodiversity across 209 plots of different urban land uses. Six land‐use types were arranged along a gradient in the intensity through which humans are hypothesized to manage species composition at the plot scale. We calculated local, or α‐diversity, and compositional turnover, or β‐diversity, of taxonomic and functional diversity across plots within each land‐use type. We compared the magnitude of these biodiversity measures between land uses to test our conceptual template for how the intensity of human management can predict urban woody plant biodiversity. ResultsWe observed high taxonomic turnover in residential and commercial plots compared with vacant or open space land‐use areas. This was associated with a weaker, but similar, pattern in functional diversity. This was associated with low total abundance in residential and commercial plots. Furthermore, the number of unique species was extremely high in the same land‐use types. ConclusionsOur observations help explain why turnover can be high in heavily managed plots relative to vacant land. In patches without heavy human management, we found low levels of turnover. This highlights the importance of assessing diversity both locally and at the level of turnover between patches. Management and policy can benefit from the perspective embodied in the conceptual approach tested here.more » « less
-
Abstract AimUnderstanding the mechanisms promoting resilience in plant communities is crucial in times of increasing disturbance and global environmental change. Here, we present the first meta‐analysis evaluating the relationship between functional diversity and resilience of plant communities. Specifically, we tested whether the resilience of plant communities is positively correlated with interspecific trait variation (following the niche complementarity hypothesis) and the dominance of acquisitive and small‐size species (following the mass ratio hypothesis), and for the context‐dependent effects of ecological and methodological differences across studies. LocationGlobal. Time Period2004–2021. Major Taxa StudiedVascular plants. MethodsWe compiled a dataset of 69 independent sites from 26 studies that have quantified resilience. For each site, we calculated functional diversity indices based on the floristic composition and functional traits of the plant community (obtained from the TRY database) which we correlated with resilience of biomass and floristic composition. After transforming correlation coefficients to Fisher'sZ‐scores, we conducted a hierarchical meta‐analysis, using a multilevel random‐effects model that accounted for the non‐independence of multiple effect sizes and the effects of ecological and methodological moderators. ResultsIn general, we found no positive functional diversity–resilience relationships of grand mean effect sizes. In contrast to our expectations, we encountered a negative relationship between resilience and trait variety, especially in woody ecosystems, whereas there was a positive relationship between resilience and the dominance of acquisitive species in herbaceous ecosystems. Finally, the functional diversity–resilience relationships were strongly affected by both ecological (biome and disturbance properties) and methodological (temporal scale, study design and resilience metric) characteristics. Main ConclusionsWe rejected our hypothesis of a general positive functional diversity–resilience relationship. In addition to strong context dependency, we propose that idiosyncratic effects of single resident species present in the communities before the disturbances and biological legacies could play major roles in the resilience of terrestrial plant communities.more » « less
