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Wood anatomy plays a key role in plants' ability to persist under drought and should therefore predict demography. Plants balance their resource allocation among wood cell types responsible for different functions. However, it remains unclear how these anatomical trade-offs vary with water availability, and the extent to which they influence demographic rates. We investigated how wood anatomical trade-offs were related to drought and demographic rates, for seedling communities in four tropical dry forests differing in their aridity indexes (AIs). We measured wood density, as well as vessel, fiber and parenchyma traits of 65 species, and we monitored growth and survival for a 1-yr period. Two axes defined wood anatomical structure: a fiber-parenchyma axis and a vessel-wood density axis. Seedlings in drier sites had larger fiber but lower parenchyma fractions, while in less dry forests, seedlings had the opposite allocation pattern. The fiber-parenchyma trade-off was unrelated to growth but was positively related to survival, and this later relationship was mediated by the AI. These findings expand our knowledge about the wood anatomical trade-offs that mediate responses to drought conditions and influence demographic rates, in the seedling layer. This information is needed to anticipate future responses of forests to changing drought conditions., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Canopy lianas differ considerably from trees in terms of wood anatomical structure, and they are suggested to have a demographic advantage-faster growth and higher survival-than trees. However, it remains unclear whether these anatomical and demographic differences persist at the seedling stage, when most liana species are self-standing and, consequently, might be ecologically similar to trees. We assessed how self-standing liana and tree seedlings differ in relation to wood anatomy, growth, and survival. We measured 12 wood traits and monitored seedling growth and survival over one year for 10 self-supporting liana and 10 tree seedling species from three tropical dry forests in Colombia. Liana and tree seedlings exhibited similar survival rates and wood anatomies for traits related to water storage and mechanical support. Yet, for traits associated with water transport, liana seedlings showed greater variability in vessel lumen size, while tree seedlings had higher vessel density. Also, the liana relative growth rate was significantly higher than for trees. These results indicate that, while self-supporting liana and tree seedlings are anatomically similar in terms of mechanical support and water storage-likely contributing to their similar survival rates-liana seedlings have a growth advantage, possibly due to more efficient water transport. These findings suggest that the well-documented anatomical and demographic differences between adult lianas and trees may depend on the liana's developmental stage, with more efficient water transport emerging as a key trait from early stages.

Seasonally tropical dry forests (SDTFs) in the American tropics are a highly diverse yet poorly understood and endangered ecosystem scattered from Northern Mexico to Southern Argentina. One floristic element of the STDFs is the genus Magoniella (Polygonaceae), which includes two liana species, M. laurifolia and M. obidensis , which have winged fruits and are distributed from Costa Rica to Southern Brazil. In a field expedition to the SDTFs of the Colombian Caribbean in 2015, morphologically distinctive individuals of Magoniella were found. In this study, we investigated the species boundaries within Magoniella and determined the phylogenetic position of these morphologically distinctive individuals in the tribe Triplaridae. We compiled morphological trait data across 19 specimens of both species and produced newly sequenced nuclear-plastid DNA data for M. obidensis . Morphometric analyses revealed significant differences in fruit length and perianth size among individuals from the Colombian Caribbean compared to M. obidensis and bract length when compared to M. laurifolia . Maximum likelihood analysis of non-conflicting nuclear and plastid datasets placed the Colombian Caribbean individuals as sister to M. obidensis with maximum statistical support. Additionally, pairwise sequence comparisons of the nuclear ribosomal ITS and the lfy2i loci consistently showed 15-point mutations (10 transitions, five transversions) and six 2 bp-long substitutions that differ between M. obidensis and the Colombian Caribbean individuals. Our morphological and molecular evidence thus suggests that the Colombian Caribbean individuals of Magoniella represent a divergent population from M. laurifolia and M. obidensis , which we describe and illustrate as a new species, M. chersina . Additionally, we provide nomenclatural updates for M. laurifolia and M. obidensis . This study highlights the power of combining morphological and molecular evidence in documenting and naming plant diversity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Aguilar-Cano, Pérez-Escobar, Pizano, Tovar and Antonelli.)

Leaf habit has been hypothesized to define a linkage between the slow-fast plant economic spectrum and the drought resistance-avoidance trade-off in tropical forests ('slow-safe vs fast-risky'). However, variation in hydraulic traits as a function of leaf habit has rarely been explored for a large number of species. We sampled leaf and branch functional traits of 97 tropical dry forest tree species from four sites to investigate whether patterns of trait variation varied consistently in relation to leaf habit along the 'slow-safe vs fast-risky' trade-off. Leaf habit explained from 0% to 43.69% of individual trait variation. We found that evergreen and semi-deciduous species differed in their location along the multivariate trait ordination when compared to deciduous species. While deciduous species showed consistent trait values, evergreen species trait values varied as a function of the site. Last, trait values varied in relation to the proportion of deciduous species in the plant community. We found that leaf habit describes the strategies that define drought avoidance and plant economics in tropical trees. However, leaf habit alone does not explain patterns of trait variation, which suggests quantifying site-specific or species-specific uncertainty in trait variation as the way forward., (© 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation.)

There is now strong evidence suggesting that interactions between plants and their species-specific antagonistic microbes can maintain native plant community diversity. In contrast, the decay in diversity in plant communities invaded by nonnative plant species might be caused by weakening negative feedback strengths, perhaps because of the increased relative importance of plant mutualists such as arbuscular mycorrhizal fungi (AMF). Although the vast majority of studies examining plant-soil feedbacks have been conducted in a single habitat type, there are fewer studies that have tested how the strength and direction of these feedbacks change across habitats with differing dominating plants. In a fragmented montane agricultural system in Colombia, we experimentally teased apart the relative importance of AMF and non-AMF microbes (a microbial filtrate) to the strength and direction of feedbacks in both native and nonnative plant species. We hypothesized that native tree species of forest fragments would exhibit stronger negative feedbacks with a microbial filtrate that likely contained pathogens than with AMF alone, whereas nonnative plant species, especially a highly invasive dominant grass, would exhibit overall weaker negative feedbacks or even positive feedbacks regardless of the microbial type. We reciprocally inoculated each of 10 plant species separately with either the AMF community or the microbial filtrate originating from their own conspecifics, or with the AMF or microbial filtrate originating from each of the other nine heterospecific plant species. Overall, we found that the strength of negative feedback mediated by the filtrate was much stronger than feedbacks mediated by AMF. Surprisingly, we found that the two nonnative species, Urochloa brizantha and Coffea arabica, experienced stronger negative feedbacks with microbial filtrate than did the native forest tree species, suggesting that species-specific antagonistic microbes accumulate when a single host species dominates, as is the case in agricultural habitats. However, negative feedback between forest trees and agricultural species suggests that soil community dynamics may contribute to the re-establishment of native species into abandoned agricultural lands. Furthermore, our finding of no negative feedbacks among trees in forest fragments may be due to a loss in diversity of those microbes that drive diversity-maintaining processes in intact tropical forests., (© 2019 by the Ecological Society of America.)

Plant-soil interactions have been shown to determine plant community composition in a wide range of environments. However, how plants distinctly interact with beneficial and detrimental organisms across mosaic landscapes containing fragmented habitats is still poorly understood. We experimentally tested feedback responses between plants and soil microbial communities from adjacent habitats across a disturbance gradient within a human-modified tropical montane landscape. In a greenhouse experiment, two components of soil microbial communities were amplified; arbuscular mycorrhizal fungi (AMF) and a filtrate excluding AMF spores from the soils of pastures (high disturbance), coffee plantations (intermediate disturbance), and forest fragments (low disturbance), using potted seedlings of 11 plant species common in these habitats (pasture grass, coffee, and nine native species). We then examined their effects on growth of these same 11 host species with reciprocal habitat inoculation. Most plant species received a similar benefit from AMF, but differed in their response to the filtrates from the three habitats. Soil filtrate from pastures had a net negative effect on plant growth, while filtrates from coffee plantations and forests had a net positive effect on plant growth. Pasture grass, coffee, and five pioneer tree species performed better with the filtrate from "away" (where these species rarely occur) compared to "home" (where these species typically occur) habitat soils, while four shade-tolerant tree species grew similarly with filtrates from different habitats. These results suggest that pastures accumulate species-specific soil enemies, while coffee plantations and forests accumulate beneficial soil microbes that benefit pioneer native plants and coffee, respectively. Thus, compared to AMF, soil filtrates exerted stronger habitat and host-specific effects on plants, being more important mediators of plant-soil feedbacks across contrasting habitats., (© 2017 by the Ecological Society of America.)

Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km(2) of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub-sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred.

In the lowlands of central Panama, the Neotropical pioneer tree Trema micrantha (sensu lato) exists as two cryptic species: "landslide" Trema is restricted to landslides and road embankments, while "gap" Trema occurs mostly in treefall gaps. In this study, we explored the relative contributions of biotic interactions and physical factors to habitat segregation in T. micrantha. Field surveys showed that soils from landslides were significantly richer in available phosphorus and harbored distinct arbuscular mycorrhizal fungal (AMF) communities compared to gap soils. Greenhouse experiments designed to determine the effect of these abiotic and biotic differences showed that: (1) both landslide and gap species performed better in sterilized soil from their own habitat, (2) the availability of phosphorus and nitrogen was limiting in gap and landslide soils, respectively, (3) a standardized AMF inoculum increased performance of both species, but primarily on gap soils, and (4) landslide and gap species performed better when sterilized soils were inoculated with the microbial inoculum from their own habitat. A field experiment confirmed that survival and growth of each species was highest in its corresponding habitat. This experiment also showed that browsing damage significantly decreased survival of gap Trema on landslides. We conclude that belowground interactions with soil microbes and aboveground interactions with herbivores contribute in fundamental ways to processes that may promote and reinforce adaptive speciation.