Nutrient‐poor ecosystems globally exhibit high plant diversity. One mechanism enabling the co‐existence of species in such ecosystems is facilitation among plants with contrasting ...nutrient‐acquisition strategies. The ecophysiological processes underlying these interactions remain poorly understood. We hypothesized that root positioning plays a role between sympatric species in nutrient‐poor vegetation. We investigated how the growth traits of the focal mycorrhizal non‐cluster‐rooted Hibbertia racemosa change when grown in proximity of non‐mycorrhizal Banksia attenuata, which produces cluster roots that increase nutrient availability, compared with growth with conspecifics. Focal plants were placed in the centre of rhizoboxes, and biomass allocation, root system architecture, specific root length (SRL), and leaf nutrient concentration were assessed. When grown with B. attenuata, focal plants decreased root investment, increased root growth towards B. attenuata, and positioned their roots near B. attenuata cluster roots. SRL was greater, and the degree of localized root investment correlated positively with B. attenuata cluster‐root biomass. Total nutrient contents in the focal individuals were greater when grown with B. attenuata. Focal plants directed their root growth towards the putatively facilitating neighbour's cluster roots, modifying root traits and investment. Preferential root positioning and root morphological traits play important roles in positive plant–plant interactions.
With an experimental design using rhizoboxes, we aimed to assess root–root interactions in putatively facilitative inter‐specific interactions. We highlight that sympatric plant species with contrasting nutrient‐acquisition strategies allow positive plant–plant interactions via preferential root positioning.
The response of small understory trees to long‐term drought is vital in determining the future composition, carbon stocks and dynamics of tropical forests. Long‐term drought is, however, also likely ...to expose understory trees to increased light availability driven by drought‐induced mortality. Relatively little is known about the potential for understory trees to adjust their physiology to both decreasing water and increasing light availability. We analysed data on maximum photosynthetic capacity (Jmax, Vcmax), leaf respiration (Rleaf), leaf mass per area (LMA), leaf thickness and leaf nitrogen and phosphorus concentrations from 66 small trees across 12 common genera at the world's longest running tropical rainfall exclusion experiment and compared responses to those from 61 surviving canopy trees. Small trees increased Jmax, Vcmax, Rleaf and LMA (71, 29, 32, 15% respectively) in response to the drought treatment, but leaf thickness and leaf nutrient concentrations did not change. Small trees were significantly more responsive than large canopy trees to the drought treatment, suggesting greater phenotypic plasticity and resilience to prolonged drought, although differences among taxa were observed. Our results highlight that small tropical trees have greater capacity to respond to ecosystem level changes and have the potential to regenerate resilient forests following future droughts.
Small understory trees are able to modify their leaf functional traits under drought conditions to elevated light availability, including increasing photosynthetic capacity and respiration. Small trees are more responsive to prolonged drought than large canopy trees of the same taxa.
At the world's longest running tropical forest throughfall exclusion experiment in Eastern Amazonia, mortality of large canopy trees has increased the light availability in the understory. Despite reduced water availability, trees in the understory show positive responses to increased light, including elevated photosynthetic capacity and respiration. This suggests small trees are able to adapt to drought conditions and could grow to become the next generation of canopy trees.
Tropical savannas are known for the fire‐prone ecosystems, yet, riparian evergreen forests are another important landscape feature. These forests usually remain safe from wildfires in the wet ...riparian zones. With global changes, large wildfires are now more frequent in savanna landscapes, exposing riparian forests to unprecedented impact.
In 2017, a large wildfire spread across the Chapada dos Veadeiros National Park, an iconic UNESCO site in central Brazil, raising concerns about its impact on the fire‐sensitive ecosystems. By combining remote sensing analysis of Google Earth images (2003–2019) with detailed field information from 36 sites, we assessed wildfire impacts on riparian forests. For this, we measured the structure of trees, saplings and herbaceous plants, as well as topsoil variables.
Since 2003, all riparian forests had canopy cover above 90%, but after 2017, canopy cover dropped to 20% in some forests, indicating large variation in wildfire damage. A closer look in the field revealed that, on average, the wildfire killed 52% of adult trees and 87% of tree saplings in flooded forests. In non‐flooded forests, impacts on adult trees were negligible, but fire killed 75% of tree saplings. Opportunistic vines and the invasive grass Melinis minutiflora were already present in severely disturbed flooded forests. In all forests, impacts on many ecosystem variables were related to canopy damage, a variable measurable from satellite. Overall, seasonally flooded riparian forests were the most severely impacted, possibly due to the relatively thinner barks of their trees.
Synthesis and applications. Our findings reveal how riparian forests embedded in tropical savanna landscapes are in danger from large wildfires. The destruction of some forests has opened space for new plant species that may propel a shift to an alternative ecosystem state. Riparian forests are habitat of large savanna animals and their loss could affect entire trophic networks. Managing wildfires and invasive grasses locally is probably the best strategy to maintain riparian forests resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings stress the need for an integrated management that considers riparian forests as a vulnerable element of the system.
Our findings reveal how riparian forests embedded in tropical savanna landscapes are in danger from large wildfires. The destruction of some forests has opened space for new plant species that may propel a shift to an alternative ecosystem state. Riparian forests are habitat of large savanna animals and their loss could affect entire trophic networks. Managing wildfires and invasive grasses locally is probably the best strategy to maintain riparian forests resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings stress the need for an integrated management that considers riparian forests as a vulnerable element of the system.
BACKGROUND AND AIMS: Euplassa cantareirae is a Neotropical Proteaceae, native to the Restinga forest in Brazil and it experiences a wide array of adverse environmental conditions, especially seasonal ...flooding and low nutrient availability. We aimed to investigate the effects of phosphorus (P) supply on plant growth and cluster root formation, as well as to characterize the main carboxylates released by the cluster roots of this species. METHODS: We conducted a greenhouse experiment where seedlings were grown in a sandy soil and watered three times a week with nutrient solution with the following P concentrations: 0, 10, 50 or 100 μM. Cluster-root production per plant, tissue P concentrations, growth parameters and carboxylate release were recorded and analyzed. RESULTS: Remarkably, cluster-root formation, biomass production and leaf P concentration did not depend on P supply. These results differ from what have been found for almost all other investigated species, except for one other plant that inhabits a similar habitat in south-western Australia, Viminaria juncea (Fabaceae). The carboxylates that were found in the rhizosphere were similar to those reported before for other Proteaceae. CONCLUSIONS: Euplassa cantareirae is a Neotropical Proteaceae producing cluster roots, and contrary to what is known for other family members, it does not appear to regulate its cluster-root formation, growth and leaf P concentration by the soil P availability.
The genetic influence in obesity prevalence is well described, but the role of genetic markers related to athletic strength/ endurance performance remains controversial. We investigated associations ...between obesity and the genetic polymorphisms alpha-actinin-3 (ACTN3) R577X and angiotensin-converting enzyme (ACE) I/D in schoolchildren aged 4-13 years from Southern Brazil. We collected sociodemographic data from parents through a questionnaire and conducted an anthropometric assessment. DNA was extracted from buccal cells and genotyping was performed by PCR. We found that 1.9% of the individuals were classified as low weight-for-age, 57.6% as normal weight and 40.5% as overweight/ obesity. Regarding allelic distribution, we found that 52.5% of individuals were DD, 30.8% ID, and 16.7% II for ACE; and 38.8% of individuals were RR, 40.2% RX and 21.0% XX for ACTN3. When both polymorphisms were combined, we observed a clear association between the composed genetic profile of these alleles and severe obesity in schoolchildren. Our data suggest that the combined analysis of ACTN3 R577X and ACE I/D polymorphisms may serve as a predictor for the risk of severe obesity in children. These data can contribute to a better understanding of the relationship between these polymorphisms and the body weight development of school-age children.
Campos rupestres is an extremely phosphorus (P)‐impoverished rocky ecosystem in Brazil. Velloziaceae is an important plant family in this environment, and some species colonize exposed quartzite ...rock. However, we know virtually nothing about their root development and nutrient acquisition within the rock outcrops and their possible role in rock weathering and landscape formation.
We tested the hypothesis that Velloziaceae dissolve P from the rock, enhancing rock weathering. The study was carried out with two Barbacenia species (Velloziaceae) that colonize quartzite rocks. We assessed the root specializations and exudates, and determined the mineralogical composition of the rocks.
The quartzite rocks contained a low concentration of total P in a matrix composed predominantly of silica. Using transmission electron microscopy, we show root growth perpendicular to the rock‐bedding planes. A micro‐XRF set‐up at the XRF beamline of a synchrotron evidenced root‐associated rock dissolution.
The investigated roots show novel morphological and physiological specializations, coined vellozioid roots, which are highly effective at P acquisition. These carboxylate‐releasing roots function like other specialized roots in nutrient‐depleted soils. The rocks represent a barrier for most species, but due to their chemical and physical actions inside the rocks, vellozioid roots play a pivotal role in rock weathering, contributing to shaping the campos rupestres landscapes.
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Plain Language Summary
Our aim was to explore the potential of Cerrado, a biodiversity hotspot which is a reservoir of genetic resources of agriculture-relevant traits to be used towards enhancing the sustainable use of ...agriculture in the region. We searched for pertinent articles dealing with all relevant aspects of Cerrado that we cover in our review. We focus on P-acquisition and P-use strategies, aluminium resistance, and plant water relations. We review results from a wide range of sources, to develop a case to curtail further destruction of native Cerrado vegetation, and works towards more sustainable crop and pasture systems in the region. We highlight many genetic resources that have tremendous potential to improve sustainable crop yield, while maintaining the key ecosystem services provided by the Cerrado that support agriculture. We conclude that the Cerrado is a rich source of plant species and plant traits to deal with environmental constraints such as soils with a low availability of P, a low pH, high availability of Al, and a low availability of water. Allowing species extinction to continue will make many untapped resources unavailable for future generations for incorporation into agriculture. Rather than allow further destruction to continue, scientists should explore relevant traits in native Cerrado species towards sustainable yields of currently used land.
Background and aims
Belowground interspecific plant facilitation is supposed to play a key role in enabling species co-existence in hyperdiverse ecosystems in extremely nutrient-poor, semi-arid ...habitats, such as
Banksia
woodlands in southwestern-Australia. Manganese (Mn) is readily mobilised by
Banksia
cluster root activity in most soils and accumulates in mature leaves of native Australian plant species without significant remobilisation during leaf senescence. We hypothesised that neighbouring shrubs are facilitated in terms of Mn uptake depending on distance to surrounding cluster root-forming
Banksia
trees.
Methods
We mapped all
Banksia
trees and selected neighbouring shrubs within a study site in Western Australia. Soil samples were collected and analysed for physical properties and nutrient concentrations. To assesses the effect of
Banksia
tree proximity on leaf Mn concentrations Mn of non-cluster-rooted woody shrubs, samples of similarly aged leaves were taken. We used multiple linear models to test for factors affecting shrub leaf Mn.
Results
None of the assessed soil parameters showed a significant correlation with shrub leaf Mn concentrations. However, we observed a significant positive effect of very close
Banksia
trees (2 m) on leaf Mn in one of the understorey shrubs. We found additional effects of elevation and shrub size.
Conclusions
Leaf micronutrient concentrations of understorey shrubs were enhanced when growing within 2 m of tall
Banksia
trees. Our model predictions also indicate that belowground facilitation of Mn uptake was shrub size-dependent. We discuss this result in the light of plant water relations and shrub root system architecture.
Whether tropical trees acclimate to long‐term drought stress remains unclear. This uncertainty is amplified if drought stress is accompanied by changes in other drivers such as the increases in ...canopy light exposure that might be induced by tree mortality or other disturbances.
Photosynthetic capacity, leaf respiration, non‐structural carbohydrate (NSC) storage and stomatal conductance were measured on 162 trees at the world's longest running (15 years) tropical forest drought experiment. We test whether surviving trees have altered strategies for carbon storage and carbon use in the drier and elevated light conditions present following drought‐related tree mortality.
Relative to control trees, the surviving trees experiencing the drought treatment showed functional responses including: (a) moderately reduced photosynthetic capacity; (b) increased total leaf NSC; and (c) a switch from starch to soluble sugars as the main store of branch NSC. This contrasts with earlier findings at this experiment of no change in photosynthetic capacity or NSC storage. The changes detected here only occurred in the subset of drought‐stressed trees with canopies exposed to high radiation and were absent in trees with less‐exposed canopies and also in the community average. In contrast to previous results acquired through less intensive species sampling from this experiment, we also observe no species‐average drought‐induced change in leaf respiration.
Our results suggest that long‐term responses to drought stress are strongly influenced by a tree's full‐canopy light environment and therefore that disturbance‐induced changes in stand density and dynamics are likely to substantially impact tropical forest responses to climate change. We also demonstrate that, while challenging, intensive sampling is essential in tropical forests to avoid sampling biases caused by limited taxonomic coverage.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
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