Tropical vegetation biomass represents a key component of the carbon stored in global forest ecosystems. Estimates of aboveground biomass commonly rely on measurements of tree size (diameter and height) and then indirectly relate, via allometric relationships and wood density, to biomass sampled from a relatively small number of harvested and weighed trees. Recently, however, novel in situ remote sensing techniques have been proposed, which may provide nondestructive alternative approaches to derive biomass estimates. Nonetheless, we still lack knowledge of the measurement uncertainties, as both the calibration and validation of estimates using different techniques and instruments requires consistent assessment of the underlying errors. To that end, we investigate different approaches estimating the tropical aboveground biomass in situ. We quantify the total and systematic errors among measurements obtained from terrestrial light detection and ranging (LiDAR), hypsometer-based trigonometry, and traditional forest inventory. We show that laser-based estimates of aboveground biomass are in good agreement (<10% measurement uncertainty) with traditional measurements. However, relative uncertainties vary among the allometric equations based on the vegetation parameters used for parameterization. We report the error metrics for measurements of tree diameter and tree height and discuss the consequences for estimated biomass. Despite methodological differences detected in this study, we conclude that laser-based electronic devices could complement conventional measurement techniques, thereby potentially improving estimates of tropical vegetation biomass.

Most leaf functional trait studies in the Amazon basin do not consider ontogenetic variations (leaf age), which may influence ecosystem productivity throughout the year. When leaf age is taken into account, it is generally considered discontinuous, and leaves are classified into age categories based on qualitative observations. Here, we quantified age-dependent changes in leaf functional traits such as the maximum carboxylation rate of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) (Vcmax), stomatal control (Cgs%), leaf dry mass per area and leaf macronutrient concentrations for nine naturally growing Amazon tropical trees with variable phenological strategies. Leaf ages were assessed by monthly censuses of branch-level leaf demography; we also performed leaf trait measurements accounting for leaf chronological age based on days elapsed since the first inclusion in the leaf demography, not predetermined age classes. At the tree community scale, a nonlinear relationship between Vcmax and leaf age existed: young, developing leaves showed the lowest mean photosynthetic capacity, increasing to a maximum at 45 days and then decreasing gradually with age in both continuous and categorical age group analyses. Maturation times among species and phenological habits differed substantially, from 8 ± 30 to 238 ± 30 days, and the rate of decline of Vcmax varied from −0.003 to −0.065 μmol CO2 m−2 s−1 day−1. Stomatal control increased significantly in young leaves but remained constant after peaking. Mass-based phosphorus and potassium concentrations displayed negative relationships with leaf age, whereas nitrogen did not vary temporally. Differences in life strategies, leaf nutrient concentrations and phenological types, not the leaf age effect alone, may thus be important factors for understanding observed photosynthesis seasonality in Amazonian forests. Furthermore, assigning leaf age categories in diverse tree communities may not be the recommended method for studying carbon uptake seasonality in the Amazon, since the relationship between Vcmax and leaf age could not be confirmed for all trees.

There are few studies on the effects of fire on the seasonal semideciduous forest of the Cerrado region. This study aimed to assess the effect of fire on Semideciduous forest fragments located in the Altamiro Moura Pacheco State Park (AMPSP). The study area is located in the central state of Goiás. A total of 10 plots (50 x 20 m; 1,000 m 2 ) were drawn in the remaining forests seeking to portray two areas: area which underwent forest fire (burned area; B) and unburned area (unburned; UB). A total of 771 individuals with DBH (≥ 5 cm) were identified. A total of 303 individuals were recorded in the burned area (B), comprising 28 families, 41 genera and 47 species, while the unburned area (UB) had 468 individuals comprising 25 families, 43 genera and 50 species. The species Anadenanthera colubrina (Vell.) Brenan, Emmotum nitens (Benth.), Zanthoxylum rhoifolium Lam, Tapirira guianensis Aubl., Myracrodruon urundeuva Allemão and Luehea candicans Mart. had the highest Importance Value Index (IVI) values and occur in both areas. The percentage of dead trees differed between the areas, where the burned area had a mortality of 12.69% and the unburned area of 7.29% in regards to the number of individuals. Density per plot was the only parameter that differed between the areas, where the burned area (B) had the lowest values. The fire affected all diameter classes, demonstrating the fragility of this vegetation type in regards to fire. The fire had a greater effect on trees in the smaller diameter classes, reducing the frequency of individuals in the burned area and changing height distribution, which may have favored the establishment of lianas and invasive species. Keywords: Abundance; richness; tree community; forest fires. Resumo Efeito do fogo na estrutura de floresta estacional no Bioma Cerrado. A área de estudo está localizada na região central do estado de Goiás.Foram sorteadas 10 parcelas, de 50 x 20 m (1.000 m 2 ), nos remanescentes florestais buscando amostrar duas áreas: área que sofreu incêndio florestal (Q) e área não queimada (NQ). Foram identificados 771 indivíduos com DAP (≥ 5cm). Na área queimada (Q) foram levantados 303 indivíduos distribuídos em 28 famílias, 41 gêneros e 47 espécies. Já na área não queimada (NQ) foram amostrados 468 indivíduos, distribuídos em 25 famílias, 43 gêneros e 50 espécies. As espécies que apresentaram os maiores valores de Índice de Valor de Importância (IVI) e que ocorrem em ambas as áreas foram Anadenanthera colubrina (Vell.) Brenan, Emmotum nitens (Benth.), Zanthoxylum rhoifolium Lam, Tapirira guianensis Aubl., Myracrodruon urundeuva Allemão e Luehea candicans Mart.. A porcentagem de árvores mortas diferenciou entre as áreas, sendo que na queimada apresentou 12,69% e na não queimada 7,29%, do número total de indivíduos. Dos parâmetros analisados, o único que apresentou diferença estatística significativa foi a densidade de indivíduos por parcela, onde a área queimada (Q) apresentou os menores valores. O fogo agiu sobre todas as classes de diâmetro, demonstrando assim ...

&lt;p&gt;In large parts of the Amazon rainforest low soil phosphorus availability may prevent the stimulation of forest growth in response to elevated atmospheric CO&lt;sub&gt;2&lt;/sub&gt; (eCO&lt;sub&gt;2&lt;/sub&gt;). One strategy of plants could be to increase the relative allocation of the extra C belowground to their root systems to enhance nutrient acquisition and alleviate the potential phosphorus limitation, but little is known about the responses of tropical lowland forest species. We hypothesized that in tropical understory plants will trigger a first a fast upregulation of fine root phosphatase activities, followed by changes in fine root productivity and adaptions of morphological parameters, such as specific root length (SRL), specific root area (SRA) and root tissue density (RTD) to enhance phosphorus mobilization, increase its availability and exploit a larger soil and litter volume.&lt;/p&gt;&lt;p&gt;We tested our hypothesis in the first CO&lt;sub&gt;2&lt;/sub&gt; enrichment experiment in Central Amazonia at a low soil phosphorus site, increasing CO&lt;sub&gt;2&lt;/sub&gt; levels by 200 ppm relative to CO&lt;sub&gt;2&lt;/sub&gt; ambient (aCO&lt;sub&gt;2&lt;/sub&gt;) concentrations using open top chambers (OTC) in the forest understory. We monitored potential root phosphatase activity, root productivity, and morphological traits in the soil with ingrowth cores (0-15 cm) and in the litter layer, as well as root biomass stocks in 0-5 and 5-10 cm of depth.&lt;/p&gt;&lt;p&gt;In contrast to our hypothesis, we observed a reduction in fine root productivity (&lt;1mm diameter), from 0.038 &amp;#177; 0.01 mg cm&lt;sup&gt;2&lt;/sup&gt; day&lt;sup&gt;-1 &lt;/sup&gt;under aCO&lt;sub&gt;2&lt;/sub&gt; to 0.013 &amp;#177; 0.004 mg cm&lt;sup&gt;2 &lt;/sup&gt;day&lt;sup&gt;-1&lt;/sup&gt; after 12 months of eCO&lt;sub&gt;2.&lt;/sub&gt; On the other hand, the fine root biomass stock (&lt;2mm diameter) increased at 5-10 cm from 0.86 &amp;#177; 0.18 at aCO&lt;sub&gt;2&lt;/sub&gt; to 1.74 &amp;#177; 0.65 mg&lt;sup&gt;-1&lt;/sup&gt; cm&lt;sup&gt;2&lt;/sup&gt; with eCO&lt;sub&gt;2&lt;/sub&gt;, but there was no effect of eCO&lt;sub&gt;2&lt;/sub&gt; on fine root biomass in the litter layer. However, roots growing in the litter layer significantly increased their SRL and showed a strong tendency of higher SRA in response to eCO&lt;sub&gt;2 &lt;/sub&gt;(SRL: 4.66 &amp;#177; 1.08 and 9.58 &amp;#177; 2.12 cm mg&lt;sup&gt;-1&lt;/sup&gt;; SRA: &amp;#160;0.63 &amp;#177; 0.18 and 1.0 &amp;#177; 0.25 cm&lt;sup&gt;2&lt;/sup&gt; mg&lt;sup&gt;-1&lt;/sup&gt; with aCO&lt;sub&gt;2&lt;/sub&gt; and eCO&lt;sub&gt;2&lt;/sub&gt;, respectively), but we did not observe changes in root morphological parameters in the soil, only a tendency towards decreasing RTD. Moreover, we found a strong trend towards an increase in potential root phosphatase activity with eCO&lt;sub&gt;2 &lt;/sub&gt;in the litter by 20.0 % (aCO&lt;sub&gt;2&lt;/sub&gt;: 66.16 &amp;#177; 10.4; eCO&lt;sub&gt;2&lt;/sub&gt;: 79.39 &amp;#177; 20.8 nmol mg&lt;sup&gt;-1 &lt;/sup&gt;dry root h&lt;sup&gt;-1&lt;/sup&gt;) and soil by 45.61% (aCO&lt;sub&gt;2&lt;/sub&gt;: 97.42 &amp;#177; 30.76; eCO&lt;sub&gt;2&lt;/sub&gt;:141.86 &amp;#177; 34.04 nmol mg&lt;sup&gt;-1 &lt;/sup&gt;dry root h&lt;sup&gt;-1&lt;/sup&gt;).&lt;/p&gt;&lt;p&gt;Our initial results suggest that understory plants intensified the investment in fine root dynamics in litter layer as response to eCO&lt;sub&gt;2&lt;/sub&gt; (e.g., increase in SRL and potential root phosphatase activity) Furthermore, with a potential increase in root phosphatases exudation (litter and soil) in the first year with eCO&lt;sub&gt;2&lt;/sub&gt;, our results reinforce the importance of this mechanism to mobilize inorganic P. Our results provide an initial understanding of nutrient mechanisms acquisition under eCO&lt;sub&gt;2&lt;/sub&gt; in a tropical forest, which can be incorporated into ecosystem models to allow more reliable predictions of forest productivity under eCO&lt;sub&gt;2&lt;/sub&gt;.&lt;/p&gt;

Os fungos micorrízicos arbusculares (FMAs) são seres simbiontes de solo que exercem um papel significativo na funcionalidade e manutenção dos ecossistemas naturais manejados e principalmente degradados. O presente estudo objetivou avaliar a ocorrência de FMAs na rizosfera de Andirobeira, Sapoteira do Solimões e Cupuaçuzeiro presentes em um Sistema Agroflorestal, sendo avaliados em quatro meses (março, junho, setembro e dezembro) de 2018. O esquema fatorial 3x4 foi usado e as médias dos tratamentos foram comparadas pelo teste de Tukey. A ANOVA de medidas repetitivas demonstrou que há efeito do tempo (F (3,12) =3.776; p- valor= 0.019) e da interação entre tempo e espécie (F(6,36) =3.918; p-valor= 0.004) na densidade de esporos. Verificou-se que as rizosferas da Sapoteira do Solimões e da Andirobeira apresentaram as maiores médias de densidade de esporos (76,2 e 70,4 esporos.50 g de solo-1), no mês de março encontrou-se uma amostra com 97 esporos.50 g de solo-1, sendo a maior encontrada. As maiores taxas de colonização micorrízica (%) foram observadas nas rizosferas da Sapoteira do Solimões e da Andirobeira, as quais diferiram estatisticamente do Cupuaçuzeiro, não havendo diferença estatística entre os meses de coleta. O gênero Glomus spp. foi dominante nas rizosferas das plantas (43,1 %), sendo o menos abundante o Gigaspora spp. (10,04 %).