FORMAS DE HUMUS EM ECOSSISTEMAS DE FLORESTA COSTEIRA INTERTROPICAL. 1- A MATA ATLANTICA DE TABULEIROS

The Mata Atlantica ecosystems, located in the north part of Espirito Santo (Linhares) has two humus foons according to the forest type: Mata Alta Forest and Mussununga Forest. In the first case, humus is a mull-like fonn, and in the second, a moder-like humus is present. In the moder humus, 22t/ha corresponding to holorganic horizons- are superposed ou the A horizon, with 500kg/ha of organic nitrogen, while in the mull, this quantity reaches 6t/ha, with 100kg/ha of organic nitrogen. Below-ground pools -A horizon at 0-10cm depth- are similar in the two decomposition systems (10t/ha of organic carbon and700kg/ha of total nitrogen). A marked organic matter accumulation in Mussunnnga forest is essentially linked to the parental soil substrata with a limited clay fraction and very poor nutrieut content. Despite the factors detennining the humus fonns, which are simihlr to temperate forests, Mata Atlântica humus are differentiated by faster recycling of nutrieuts and a high organic-maner turnover.O ecossistema de Mata Atlantica localizado no norte do Espírito Santo (Linhares), apresenta duas fomas de húmus, de acordo com o tipo florestal: Mata Alta e Mata Mussununga. No primeiro caso, observa-se um húmus do tipo mull, enquanto a segunda fitofisionomia apresenta um humus do tipo moder. Nesta forma de humus, encontramos no horizonte holorgânico 22t/ha de matéria orgânica superficial e 500kg/ha de nitrogênio orgânico, enquanto no mull, estes valores alcançam 6t/ha de matéria orgânica superficial e 100kg/ha de nitrogênio orgânico. Com relação ao horizonte A subjacente (0-10cm), as duas áreas são similares nos seus conteúdos de matéria orgânica nitrogênio (10t/ha de carbono orgânico e 700kg/ha de nitrogênio total). Uma marcada acumulação superficial de matéria orgânica na Mata de Mussununga está intimamente relacionada à composição do substrato parental, com uma limitada fração de argila e baixíssimo conteúdo de nutrientes. Apesar dos fatores determinantes das formas húmicas serem semelhantes aos das florestas temperadas, os húmus da Mata Atlântica são diferenciados pela rápida reciclagem de nutrientes e alto" turnover" da matéria orgânica

Soil macroinvertebrate communities: A world-wide assessment

© 2022 The Authors. Global Ecology and Biogeography published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.[Aim] Macroinvertebrates comprise a highly diverse set of taxa with great potential as indicators of soil quality. Communities were sampled at 3,694 sites distributed world-wide. We aimed to analyse the patterns of abundance, composition and network characteristics and their relationships to latitude, mean annual temperature and rainfall, land cover, soil texture and agricultural practices.[Location] Sites are distributed in 41 countries, ranging from 55° S to 57° N latitude, from 0 to 4,000 m in elevation, with annual rainfall ranging from 500 to >3,000 mm and mean temperatures of 5–32°C.[Time period] 1980–2018.[Major taxa studied] All soil macroinvertebrates: Haplotaxida; Coleoptera; Formicidae; Arachnida; Chilopoda; Diplopoda; Diptera; Isoptera; Isopoda; Homoptera; Hemiptera; Gastropoda; Blattaria; Orthoptera; Lepidoptera; Dermaptera; and “others”.[Methods] Standard ISO 23611-5 sampling protocol was applied at all sites. Data treatment used a set of multivariate analyses, principal components analysis (PCA) on macrofauna data transformed by Hellinger’s method, multiple correspondence analysis for environmental data (latitude, elevation, temperature and average annual rainfall, type of vegetation cover) transformed into discrete classes, coinertia analysis to compare these two data sets, and bias-corrected and accelerated bootstrap tests to evaluate the part of the variance of the macrofauna data attributable to each of the environmental factors. Network analysis was performed. Each pairwise association of taxonomic units was tested against a null model considering local and regional scales, in order to avoid spurious correlations.[Results] Communities were separated into five clusters reflecting their densities and taxonomic richness. They were significantly influenced by climatic conditions, soil texture and vegetation cover. Abundance and diversity, highest in tropical forests (1,895 ± 234 individuals/m2) and savannahs (1,796 ± 72 individuals/m2), progressively decreased in tropical cropping systems (tree-associated crops, 1,358 ± 120 individuals/m2; pastures, 1,178 ± 154 individuals/m2; and annual crops, 867 ± 62 individuals/m2), temperate grasslands (529 ± 60 individuals/m2), forests (232 ± 20 individuals/m2) and annual crops (231 ± 24 individuals/m2) and temperate dry forests and shrubs (195 ± 11 individuals/m2). Agricultural management decreased overall abundance by ≤54% in tropical areas and 64% in temperate areas. Connectivity varied with taxa, with dominant positive connections in litter transformers and negative connections with ecosystem engineers and Arachnida. Connectivity and modularity were higher in communities with low abundance and taxonomic richness.[Main conclusions] Soil macroinvertebrate communities respond to climatic, soil and land-cover conditions. All taxa, except termites, are found everywhere, and communities from the five clusters cover a wide range of geographical and environmental conditions. Agricultural practices significantly decrease abundance, although the presence of tree components alleviates this effect.Peer reviewe

Effects of land-use system on the soil macrofauna in western Brazilian Amazonia

Agroforestry systems are presented as a valuable alternative to pastures to sustain crop production in forested areas. In order to evaluate their effect on soil macroinvertebrate communities, sampling was conducted during the rainy season at four localities located in the Rondônia and Acre states of Brazil. Four land-use systems were selected (fallow, annual crop, agroforestry systems and pasture), and compared to nearby disturbed forests. We used the sampling method recommended by the Tropical Soil Biology and Fertility Programme. Soil macrofauna responded more readily than soil parameters to different cultivation practices. Co-inertia analysis, however, showed a relationship between soil parameters and soil macrofauna. Comparison of communities showed a significant impact of land-use practices. All systems had quite abundant invertebrate communities with relatively low densities in the forest (884 ind. m-2) and in pastures (841 ind. m-2), and higher densities in fallow, agroforestry system and annual crop (1,737-1,761 ind. m-2). Earthworms were dominant in pastures (155 ind. m-2 and 56.2 g m-2 on average), whereas termites thrived better in annual crops and fallows (with respective densities of 1,287 and 816 and biomasses of 2.32 and 1.38 g m-2). Macrofauna communities in agroforestry systems were rather similar to the forest, in spite of higher densities of social insects. The termite:earthworm ratios were very low in pastures (0.2), had similar values in the forest (7.9) and the agroforestry system (8.8), which is much lower than in fallows (20.4) and annual crops (21.4) This study showed that all land-use practices were able to sustain sizeable macrofaunal communities with agroforestry communities rather similar to the those of a disturbed forest

Effects of forest conversion to pasture on soil carbon content and dynamics in Brazilian Amazonia

Soils play an important role in the carbon cycle, and deforestation in the tropics affects both soil carbon storage and CO2 release into the atmosphere. The consequences of deforestation and conversion to pasture for soil carbon content and dynamics were examined in two soil types differing mainly by their texture. Two chronosequences were selected, each consisting of an intact forest and three pastures of different ages (4, 8, 15 years and 3, 9, 15 years, respectively). One chronosequence is located in the central part of the Brazilian Amazon basin, where the soils are clayey ferralsols, and the second in the Eastern Brazilian Amazon Basin, where the soils are sandy clayey acrisols. In the upper layer the C content of clayey soils was three times higher than in the sandy soils, but despite the differences in soil texture, the C distribution in the particle-size fractions was quite similar. In the two chronosequences, the conversion to pasture induced a slight increase in C content. Bulk density increases were greater on soils with lower clay contents. The 13C measurements, which allowed to calculate the distribution of C derived from forest and from pasture, showed that all the particle-size fractions incorporated C derived from pasture and that a significant proportion of the young organic matter is rapidly trapped in the finest fractions. Although the proportions of pasture-derived C were higher in the sandy soils than in the clayey soils, the amounts of pasture-derived C in the particle-size fractions were 2-3 times larger in the clayey soils than in the sandy soils. © 2004 Elsevier B.V. All rights reserved

Land and soil problems : advances in methodological and empirical research and key challenges

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The role of macrofauna in the transformation and reversibility of soil structure of an oxisol in the process of forest to pasture conversion

In a central Amazonian pasture, a single earthworm species, Pontoscolex corethrurus, becomes very abundant (400 ind. m-2) after forest clearing. Its casts form a compact, continuous and impermeable crust with a thickness of 20 cm. To analyze the structural modifications, we established a field experiment in which soil blocks from the forest were implanted in the pasture, and soil blocks from the pasture were implanted in the forest. The objectives were (1) to verify the formation of the compact crust at the soil surface in pasture environment, (2) to evaluate the time necessary for the formation and the destruction of this crust, and (3) to find out if the crust formation was a reversible process. We used quantitative morphology to identify the biogenic structures formed by different fauna groups and to quantify the modifications in the solid phase as well as the resulting porosity. For the soil depth 0-5 cm, the measured porosity was 48% in the forest and 16% in the pasture. After 1 year, the blocks of forest soil installed in the pasture presented a porosity of 26%, and the blocks of pasture soil installed in the forest presented a porosity of 34%. There were significant differences between the control blocks and the exchanged blocks. The results demonstrate that the processes of formation and destruction of the biogenic structures are reversible. Approximately 1 year is necessary to re-establish the equilibrium between the exchanged blocks and the control blocks. This experiment illustrates the compacting effect of P. corethrurus. In addition, the small millimetric pores, which are formed by termites in the blocks of pasture soil implanted in the forest, show the decompacting effect of certain termite groups. © 2001 Elsevier Science B.V