Renato Marques

Understanding how P availability affects root turnover and P redistribution within plants is essential for optimizing fertilization strategies and sustaining forest growth under low-P soils. This study evaluated the effects of P fertilization on root system dynamics, plant growth, and P nutrition of Handroanthus heptaphyllus, a flowering landscape tree, cultivated in a subtropical climate. Plants were grown under two soil P levels (low and high). Plant height, stem diameter, leaf P concentration, soil P availability, total numbers of living and dead fine roots, total fine root surface area, and fine root production rate were measured at 18, 24, 30, and 36 months after planting. Phosphate fertilization increased soil P availability during the first 24 months and resulted in significant gains in plant height, stem diameter, fine root production, total surface area, and the ratio between living and dead fine roots, indicating a higher proportion of living roots relative to dead ones. Under high P availability, the greatest fine root production and surface area of living fine roots occurred in the 0–20 cm soil layer, reflecting localized P application near the plants. High P availability enhanced root system development, promoted greater soil exploration, and improved P uptake. These results indicate that under P supplementation, plants strategically invest in root growth, improving nutrient acquisition efficiency and reducing dependence on external inputs. Increased phosphorus availability enhances root growth and increases fine root production and turnover. Minirhizotron monitoring effectively captured shifts in root system dynamics driven by P availability, including enhanced root growth, increased fine root production and turnover, and improved nutrient uptake under high P, as well as limited root activity under low P conditions, indicating a more conservative strategy with reduced investment in root production.

This study aimed to generate knowledge about transition areas between phytophysiognomies for the understanding and conservation of these unique environments. Thus, the existence of different floristic groups was analyzed in a spatial gradient of an ecotone in the municipality of São Desidério, state of Bahia, Brazil. To this end, a transect of approximately 4.7 km, with orientation from Northeast to Southwest, was established along a spatial gradient. Twelve (12) 10x50 m sampling plots (500 m² each) were distributed throughout this transect. The following methodology was employed: First, the floristic similarity between the sampling plots was measured. These sampling plots were then grouped and the data were graphically presented in a dendrogram (Cluster analysis) and an ordering diagram (nMDS). Finally, the phytosociological parameters by ordered group were obtained. The results showed the presence of three floristic groups: Groups I, II and III, classified as wooded savannah, seasonal deciduous forest, and forested savannah, respectively. The floristic groups were formed gradually along the spatial gradient, and transition between phytophysiognomies does not occur abruptly, since the ordering by groups is more due to the difference between the abundance of species than to their presence and/or absence. The distribution pattern of the phytophysiognomies along the spatial gradient indicates association with abiotic factors, such as the pedological characteristics and the relief found along the transect, possibly creating an environmental gradient.

Forests play an important role in climate change, acting as a source or sink of carbon. There is, however, a lack of data regarding the carbon production from litterfall in tropical forests. The At...

The Program for Biodiversity Research (PPBio) is an innovative program designed to integrate all biodiversity research stakeholders. Operating since 2004, it has installed long-term ecological research sites throughout Brazil and its logic has been applied in some other southern-hemisphere countries. The program supports all aspects of research necessary to understand biodiversity and the processes that affect it. There are presently 161 sampling sites (see some of them at Supplementary Appendix), most of which use a standardized methodology that allows comparisons across biomes and through time. To date, there are about 1200 publications associated with PPBio that cover topics ranging from natural history to genetics and species distributions. Most of the field data and metadata are available through PPBio web sites or DataONE. Metadata is available for researchers that intend to explore the different faces of Brazilian biodiversity spatio-temporal variation, as well as for managers intending to improve conservation strategies. The Program also fostered, directly and indirectly, local technical capacity building, and supported the training of hundreds of undergraduate and graduate students. The main challenge is maintaining the long-term funding necessary to understand biodiversity patterns and processes under pressure from global environmental changes.

Necromass is crucial to understanding both carbon and nutrient cycling throughout the forest. In this study, we assessed the carbon stock and spatial distribution of necromass components in an Atlantic rainforest, southern Brazil, one hotspot of biodiversity. Necromass comprised: standing dead trees and stumps (SWN), large-sized woody necromass (LWN), medium-sized woody necromass (MWN), and litter (LTR). Specific sample designs assessed each component, while the Payandeh index indicated spatial distribution. Mean wood densities of LWN ranged from 0.24 to 0.46 g.cm⁻³, and mean carbon fraction ranged from 0.42 to 0.44 gC.g⁻¹ d.m. depending on decay class. The total necromass carbon stock was 12.83 MgC.ha⁻¹. SWN, LWN, MWN, and LTR carbon stores were 3.15, 4.24, 1.50, and 3.53 MgC.ha⁻¹, respectively. LWN and MWN showed a reverse J-curve skewed carbon stock distribution and clumped spatial pattern. LTR presented asymmetric distribution and a random spatial pattern. Coarse and heavy necromass is clumped near dead trees, while the wind scatters fine necromass throughout the forest. This study provides useful information to the understanding of the carbon cycle in Atlantic rainforests and may be helpful to improve the Brazilian Inventory of Anthropogenic Emissions and Removals of Greenhouse Gases and the Global Forest Resource Assessment.

O objetivo deste trabalho foi compreender a dinâmica da mineralização do nitrogênio (N) do solo, nas diferentes estações do ano, em Espodossolo sob Floresta Ombrófila Densa das Terras Baixas, no litoral do Paraná. Foram feitos dois ensaios de mineralização do nitrogênio, um aeróbico e outro anaeróbico, com amostras de solo coletadas nas profundidades 0-5 e 5-10 centímetros (cm). No anaeróbico as amostras de solo foram submetidas ao processo de incubação/extração em período sequencial de 0, 15, 30, 45, 60 e 75 dias, sendo a incubação feita com solução nutritiva, em estufa a 30 graus Celsius (º C) a extração de nitrogênio inorgânico com soluções de Cloreto de Potássio (KCl) e as determinações de N inorgânico por leitura em espectrofotômetro ultra violeta visível (UV-VIS) a 210 nanômetros (nm) para (nitrato) e pelo método do endofenol (amônio) descrito por Waring e Bremner (1964); APHA (1995). No aeróbico as amostras foram secas a 30º C, sendo feita uma primeira extração de N inorgânico com soluções de KCl. Depois disso, as amostras foram umedecidas a 30 porcento (%) e incubadas a 19,8 ºC em câmara fitoclimática por 15 dias. Diariamente foi feita leitura de respiração do solo e, ao final, foi feita nova extração com KCl. Alíquotas dos dois extratos obtidos foram então transferidas para microplacas para leitura de nitrato e amônio (Rodríguez et al., 2009). A análise estatística foi realizada com teste paramétrico com teste de Duncan (p<0,10) para os resultados de mineralização anaeróbica. A mineralização do N no solo mostrou-se influenciada pelas estações do ano e suas variáveis meteorológicas, além da umidade do solo. As temperaturas mais elevadas favoreceram a atividade microbiológica, a umidade do solo quando excessiva resulta em menor nitrificação e maior amonificação. Os ensaios de mineralização anaeróbico e aeróbico mostraram-se como ferramentas importantes para a identificação do efeito estacional e na profundidade de coleta sobre a mineralização de N no solo. Palavras-chave: carbono; respiração do solo; amonificação; nitrificação; processo de mineralização. MINERALIZATION OF NITROGEN IN THE SOIL UNDER ATLANTIC RAINFOREST DENSE OMBROPHYLOUS OF THE LOWLAND, IN PARANAGUÁ, PR – BRAZIL The objective of this work was to understand the dynamics of soil nitrogen mineralization in the different seasons of the year in Spodosol under Atlantic Rainforest Dense Ombrophylous of the Lowland in the Paraná state coast. Two nitrogen mineralization tests, one aerobic and one anaerobic, were performed at depths 0-5 and 5-10 centímetros (cm) in Spodosol under Dense Ombrophylous Lowland. The anaerobic test, soil samples were subjected to the incubation /extraction process in a sequential period of 0, 15, 30, 45, 60 and 75 days, with incubation being carried out with nutrient solution, in an oven at 30 degrees Celsius (º C) the extraction of inorganic nitrogen with solutions of Potassium Chloride (KCl) and the determination of inorganic N by reading in a visible ultra violet spectrophotometer (UV-VIS) at 210 nanometers (nm) for (nitrate) and by the endophenol (ammonium) method described by Waring and Bremner (1964); APHA (1995). The aerobic test, the samples were dried at 30º C, with a first extraction of inorganic N with KCl solutions. After that, the samples were moistened at 30 percent (%) and incubated at 19.8 ºC in a phytoclimatic chamber for 15 days. The soil breath was read daily and, at the end, a new extraction was done with KCl. Aliquots of the two extracts obtained were then transferred to microplates for reading nitrate and ammonium (Rodríguez et al., 2009). Statistical analysis was performed with parametric test with Duncan's test (p <0.10) for the results of anaerobic mineralization. The mineralization of N in the soil was shown to be influenced by the seasons and its meteorological variables, in addition to soil moisture. Higher temperatures favored microbiological activity, and excessive soil moisture results in less nitrification and greater ammonification. The anaerobic and aerobic mineralization tests proved to be important tools for the identification of the seasonal effect and the depth of collection in the mineralization of N in the soil. Keywords: carbon; soil respiration; ammonification; nitrification; mineralization process.