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Background and aims We aimed to investigate the effects of root carboxylate exudation in the interaction between Azospirillum brasilense and Zea mays. We hypothesized that root carboxylate exudation is a mechanism that increases colonization of the maize rhizosphere by A. brasilense and that carboxylate exudation would increase at a low soil phosphorus (P) availability. Methods We conducted a greenhouse experiment, using maize seeds inoculated and uninoculated with A. brasiliense. Seeds were planted in pots, supplied with nutrient solution, varying in P concentration. After 45 days we measured total plant biomass, root length and area, plant nutrient status, and the root carboxylate-exudation rate. Results Inoculation increased the root length and area, and this effect increased with increasing P supply. Inoculated plants also showed an increased root carboxylate-exudation rate. For inoculated treatments, the exudation rate was positively correlated with root architecture parameters; however, it was negatively correlated with leaf manganese concentration, a proxy for the amount of carboxylates in the rhizosphere. Conclusion Inoculation of A. brasilense stimulated root caiboxylate exudation, which was positively correlated with root length and area. These positive correlations are probably mediated by the effect of carboxylates on the rhizosphere microbial community. This indicates a positive feedback in which A. brasilense inoculation stimulates root caiboxylate exudation, influencing the rhizosphere microbial community. It results in positive effects on maize root architecture. The root length of inoculated plants was positively correlated with P supply, indicating that P supply positively affects the microbial community, modulating the interaction between A. brasilense and Z mays.

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.

Research highlights: Tropical forest restoration can be supported by the production of timber species in their understory. While they may appear at odds, they can be reconciled to promote environmental conservation and services. The lack of information on the management of tropical species causes a technical constraint for timber production in the understory of restoration sites, especially given the light restrictions. This issue could be amended with the development of methods to easily manage and estimate light availability, targeting management practices that balance restoration success and productivity. Materials and Methods: We conducted this study in an area within the Atlantic Forest, Brazil, where we tested the efficiency of chemical thinning to increase light availability in the understory of a five-year-old restoration planting, aiming to increase the growth rates of desirable timber species. Moreover, we tested the viability of using hemispherical photography taken with a smartphone to assess light incidence to assist restoration management practices. We calculated the percentage of photosynthetically active radiation (PAR) using a ceptometer in four different thinning intensities and compared them to the smartphone measures using correlation analysis. Results: Chemical thinning increased light incidence in the understory, with potential impacts on timber species productivity. Light management through PAR and canopy opening were highly correlated overall, especially after three months of management and 60% of thinning intensity. Conclusions: These findings demonstrate the potential for chemical thinning as a management practice to enhance light availability in the understory of tropical forest restoration sites. Additionally, our study highlights the value of using affordable and accessible tools like smartphones and fisheye clips for the indirect assessment of light conditions to promote natural regeneration and guide forest management and timber production in tropical forest restoration.

Background and Research Aims: Monitoring is essential for assessing the success of ecological restoration efforts. Ants, with their vast diversity and functional roles, serve as a significant group for such analyses. This study focused on evaluating ant communities to identify potential arboreal species that could serve as indicators of the forest restoration process. Methods: The study was carried out in restoration areas within the Seasonal Semideciduous Forest, located in two landscapes within the Atlantic Forest of southeastern Brazil. We examined forest restoration plantations at three different developmental stages—early, middle, and late—alongside a native reference forest. Key parameters such as canopy cover and density of trees and saplings were measured. Ants were actively sampled throughout different seasons. We assessed ant community compositions across restoration gradients and investigated their association with vegetation structure. We also identified ant species that could serve as restoration indicators. Results: We identified a total of 60 species and 19 morphospecies. However, no significant difference in species richness was observed among the areas. Ant communities in restoration areas exhibited more similarity to each other than to those in native forests. Therefore, even in the oldest restored sections, ant communities have not yet converged with those of the reference ecosystem. Although we identified some indicator species within certain areas, none of these were arboreal. Conclusion: The composition of the ant community is more valuable than its species richness for monitoring tropical forest restoration. The historical context of restoration areas and the age of restoration efforts may influence the results. Implications for conservation: Early stages of tropical forest restoration do not recover the biodiversity and composition of arboreal ants found in reference forests. Additional studies are needed to better understand changes in the ant communities over time, providing information to improve monitoring, management and the conservation value.

African mahogany (Khaya spp.) produces high-value wood, and its cultivation is expanding in tropical regions. The silvopastoral system is an alternative method for growing timber trees, but may involve cattle stripping bark from trees, which limits its usefulness. We evaluated cattle bark-stripping rates in two African mahogany species, K. grandifoliola and K. senegalensis, in a silvopastoral system with Guinea grass, Panicum maximum, in South-eastern Brazil. Cattle had free access to plantations of both tree species for 2 weeks in May 2018 and July 2019, when trees were 5 and 6 years old, respectively. In 2018, we found bark-stripping only in K. grandifoliola, but in 2019 both species were bark-stripped. The proportion of bark-stripped trees was higher for K. grandifoliola than for K. senegalensis. Considering both years, 29/155 (18.7%) K. senegalensis trees and 106/153 (69.3%) K. grandifoliola trees had some of their bark-stripped by cattle. Bark-stripped trees had lower trunk diameter growth than unaffected trees, and their growth was affected by the degree of bark-stripping. Some trees were girdled by bark-stripping. These trees dried up, and some of them fell down 1 year after girdling. In 2019, despite the high herbage mass, levels of crude protein in the pasture were very low, which may have stimulated bark-stripping. Although we could not identify the reasons for bark-stripping, we recommend avoiding the use of silvopastoral systems with cattle and African mahogany in times of the year when pasture has a low quality.

Purpose The overharvesting of the endemic palm tree Euterpe edulis Mart. (Arecaceae) from the Brazilian Atlantic Forest hotspot and the destination given to the sludge produced from urban sewage treatment are both serious environmental issues caused by human activities. In order to find solutions or alternatives for both the issues, we aimed to investigate the effect of increasing rates of a sewage sludge organic fertilizer (SSOF), produced by composting sewage sludge and solid waste, on the initial growth of E. edulis. Methods We mixed sand with 0, 62.5, 125, and 250 kg·m−3 of SSOF in 8 L (21 cm height × 24 cm top diameter × 20.5 cm base diameter) pots and then planted a seedling of E. edulis in each pot. We assessed the seedlings’ height and stem diameter relative growth rate (RGR), biomass, root to shoot ratio, and shoot macronutrient (nitrogen, phosphorous, potassium, calcium, magnesium, and sulphur) concentrations in relation to fertilizer levels. We also evaluated the relation between plant height and diameter over time for each fertilization level. Results We found that height and stem diameter RGRs, biomass accumulation, and N and P shoot concentrations of E. edulis were positively related to SSOF levels between 120 and 250 kg·m−3 in the substrate. Conclusions Our study demonstrates that SSOF can be further used as an alternative to sewage sludge disposal and contribute to E. edulis cultivation, and, hence, its conservation.

Neste trabalho, foi avaliada a viabilidade do uso de composto de lodo de esgoto, proveniente de estação de tratamento de esgoto, como fertilizante alternativo para o cultivo inicial de eucalipto. O experimento foi realizado em casa de vegetação no CCA - UFSCar, Araras, SP. Os cultivos ocorreram em vasos de 11 L durante 75 dias. O delineamento experimental foi inteiramente ao acaso, com cinco tratamentos e sete repetições. Os tratamentos adotados foram constituídos por uma testemunha, três tratamentos com composto de lodo de esgoto (25%, 50% e 75% do volume do vaso) e um tratamento com fertilizante mineral convencional, todos em solo arenoso. Ao final do experimento, a taxa de crescimento relativo (TCR) e a massa seca das plantas foram medidas e submetidas à análise de variância seguida pelo teste de Tukey a 5% de probabilidade. A TCR foi maior nos tratamentos com fertilização do que na testemunha, mas não diferiu entre a fertilização mineral e as doses de fertilização orgânica. A massa seca das plantas foi maior no tratamento com 50% do volume do vaso com fertilizante orgânico (p<0,01). Assim, o composto de lodo de esgoto se mostrou com potencial para substituir fertilizantes minerais convencionais no cultivo inicial de eucalipto.

We aimed to investigate the effects of root carboxylate exudation in the interaction between Azospirillum brasilense and Zea mays. We hypothesized that root carboxylate exudation is a mechanism that increases colonization of the maize rhizosphere by A. brasilense and that carboxylate exudation would increase at a low soil phosphorus (P) availability. We conducted a greenhouse experiment, using maize seeds inoculated and uninoculated with A. brasiliense. Seeds were planted in pots, supplied with nutrient solution, varying in P concentration. After 45 days we measured total plant biomass, root length and area, plant nutrient status, and the root carboxylate-exudation rate. Inoculation increased the root length and area, and this effect increased with increasing P supply. Inoculated plants also showed an increased root carboxylate-exudation rate. For inoculated treatments, the exudation rate was positively correlated with root architecture parameters; however, it was negatively correlated with leaf manganese concentration, a proxy for the amount of carboxylates in the rhizosphere. Inoculation of A. brasilense stimulated root carboxylate exudation, which was positively correlated with root length and area. These positive correlations are probably mediated by the effect of carboxylates on the rhizosphere microbial community. This indicates a positive feedback in which A. brasilense inoculation stimulates root carboxylate exudation, influencing the rhizosphere microbial community. It results in positive effects on maize root architecture. The root length of inoculated plants was positively correlated with P supply, indicating that P supply positively affects the microbial community, modulating the interaction between A. brasilense and Z. mays.

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. 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 [mu]M. Cluster-root production per plant, tissue P concentrations, growth parameters and carboxylate release were recorded and analyzed. 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. 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.

This study evaluated the feasibility of sewage sludge compost obtained from a sewage treatment plant as an alternative \"Class D\" organic fertilizer for the initial cultivation eucalyptus. The experiment was conducted in a greenhouse at CCA - UFSCar, Araras, SP. Cultivation occurred in 11 L pots for 75 days. We adopted a completely randomized design, with five treatments and seven repetitions. The tests considered a control treatment with no fertilization, three treatments with sewage sludge compost addition (25%, 50%, and 75% of the pot volume) and a treatment with conventional mineral fertilizers, all in sandy soil. At the end of the experiment, plant relative growth rate and dry mass were evaluated and submitted to analysis of variance, followed by a Tukey test at 5% probability. Treatments with fertilization had a greater relative growth rate than the control; however, we found no difference between mineral and organic fertilization. Plant dry mass was higher in the treatment with 50% of the pot filled with organic fertilizer. Thus, we conclude that the tested sewage sludge compost is a potential substitute for conventional mineral fertilization for the initial cultivation of eucalyptus.