Extraterrestrial soils

Extraterrestrial soils may be defined as any of the solid granular crustal features of planets and moon other than those soils on planet Earth. Despite four decades of space exploration, which greatly expanded our understanding of the Solar System, there is considerable debate as to the loose covers of rocky planets and moons are soils in a pedological sense. On Earth, soil form thanks to the combined action of at least five factors: parent rock, climate, topography, living organisms and time. A few other factors can concur to drive pedogenesis. However, the necessity of biota as unavoidable soil forming factor is debated. In fact, important parts of Earth, such as the hyperarid Atacama Desert of Chile and the Dry Valleys of Antarctica, host virtually life-free soils with advanced horizonation. Actually, although most people invokes the ability to support plant growth in its natural environment as condicio sine qua non for soil, a scientific definition considers soil to be any in situ weathered veneer of a planetary surface that retains information on its climatic and geochemical history. A current or past mineral weathering is hence the pivotal requisite for soil

Abundance and composition of free and aggregate-occluded carbohydrates and lignin in two forest soils as affected by wildfires of different severity

International audienceOrganic matter is the soil component most affected by wildfires, both in terms of abundance and composition. Fire-induced alteration of soil organic matter (SOM) depends on heating intensity and duration, oxygen availability and other factors related to topography, climate, soil and vegetation features. Particularly affected by fire is the litter layer, but SOM from the uppermost mineral soil can also experience some major changes. In this study, we investigated the direct impact of fire on molecular SOM parameters in density fractions isolated from the top 2.5 cm of mineral soil in two forests that recently experienced wildfires of different severity. One, located in Tuscany, Central Italy, is a mixed forest of Downy oak and Maritime pine, developed on Acrisols formed on sandy lacustrine deposits, affected by a moderately severe fire. The other, located in Victoria, South-East Australia, is a mixed-species eucalypt forest, developed on a Cambisol formed on sandy Devonian sediments, affected by an extremely severe fire (the infamous 'Black Saturday' fire). The purpose of this study was the assessment of fire-induced changes on amount and composition of the bulk SOM and SOM associated to soil fractions having different densities. We used 1.8 Mg m(-3) as density cut-off and distinguished between free and aggregate-occluded SOM. In particular, the analyses focused on abundance and composition of two major SOM components, proposed as molecular indicators of fire severity: the non-cellulosic neutral sugars, digested by trifluoroacetic acid (TFA), and the lignin-derived phenolic monomers, released by cupric oxide (CuO) oxidation. The chemical structure of both bulk SOM and SOM fractions were analysed by solid-state C-13 nuclear magnetic resonance spectroscopy. In contrast to the moderately severe fire affecting the Italian site, the extremely severe fire at the Australian site caused substantial loss of SOM from the top mineral soil. Both fires had major effects on SOM composition. In spite of the evident impact they experienced, neither hydrolysable sugars nor lignin phenols resulted to be reliable indicators of fire severity. Moreover, both fires apparently broke up soil aggregates, hence promoting the release of some occluded organic matter. The fire-induced changes of SOM observed have implications for the C cycle, so highlighting the critical role of wildfire occurrence and severity in climate change

Radiocarbon dating reveals different past managements of adjacent forest soils in the Campine region, Belgium

The soils of adjacent first generation monospecific stands of Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) in the Campine region, Belgium, apparently developed under the same forming factors, were studied for carbon dynamics to disentangle eventual different past land uses. In fact, visual observations suggested that the soil under pine experienced substantial addition of organic matter and ploughing, such to be considered a plaggen, opposite to the soil under oak, which is inexplicably much poorer in C. In order to prove this hypothesis, the soil organic carbon was quantified by horizons and, both bulk soil organic matter (SOM) and the least mobile SOM fractions - the humic acid and the unextractable fractions - were radiocarbon dated. Surprising was the marked difference between the mean SOM age from the two stands. In fact, while under oak this age is a few years or decades, under pine it amounts to more than a millennium, so confirming the hypothesis of a confined C supply occurred mainly in the Middle Age, or later using partly humified matter. The mean residence time (MRT) of SOM in the organic layers matches almost perfectly with that estimated via a mass balance approach and, as expected, was much lower in the oaks than in the pines. The humic acid fraction, generally the most stable fraction of SOM, in terms of both mobility and degradability, reflects the behaviour of the bulk SOM, showing higher radiocarbon ages under pine. The findings of this work indicate that the large human-induced additions of organic material in the area now occupied by the pine stand, probably occurred in the Middle Age and it continues to strongly affect the present soil C pools and their dynamics. Any study dealing with budgets and dynamics of C in soil should avail itself of a careful reconstruction of the land uses and management history, in order to provide reliable conclusions about the real role of the current vegetation on soil carbon. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved

UPAYA MENINGKATKAN HASIL BELAJAR SISWA MELALUI LESSON STUDY PADA PENJUMLAHAN PECAHAN DI KELAS IV SDK TEBUK

Materi penjumlahan pecahan merupakan salah satu materi yang dipandang susah bagi siswa SD, terutama penjumlahan pecahan yang berpenyebut tidak sama. Adalah tanggung jawab seorang guru untuk memastikan agar siswa dapat memahami tentang penjulahan pecahan. Penelitian ini bertujuan untuk mengetahui 1) kemampuan guru mengajarkan materi penjumlahan pecahan di kelas IV SDK Tebuk melalui Lesson Study; 2) aktifitas siswa di kelas selama proses pembelajaran materi penjumlahan pecahan di kelas IV SDK Tebuk melalui Lesson Study; 3) hasil belajar siswa pada materi penjumlahan pecahan di kelas IV SDK Tebuk melalui Lesson Study; 4) respon siswa terhadap pembelajaran melalui Lesson Study pada materi penjumlahan pecahan di kelas IV SDK Tebuk. Metode penelitian yang dipakai untuk mencapai tujuan tersebut adalah pendekatan kualitatif dengan jenis penelitian deskriptif, dengan menggunakan Lesson Study. Berdasarkan hasil pengolahan data didapat bahwa 1) kemampuan guru dapat mencapai peningkatan dan berada dalam kategori sangat baik; 2) aktivitas siswa dapat mencapai peningkatan dan berada dalam kategori sangat  baik; 3) hasil tes siswa dapat mencapai peningkatan; dan 4) respon siswa terhadap pembelajaran penjumlahan melalui Lesson Study adalah positif. Oleh karena itu, dapat disimpulkan bahwa melalui pembelajaran berbasis Lesson Study, pembelajaran penjumlahan pecahan di kelas IV SDK Tebuk dikatakan efektif

Holocene as Anthropocene

Anthropocene seems a more reasonable name than Holocene for this combined time span, whose most characteristic trait is the human pressure on the planet. Holocene could possibly be the first stage of the Anthropocene, the one characterized by a soft and spotty human impact on Earth

Soil forming factors

The Russian geologist Vasily Dokuchaev (1846–1903), considered the father of soil science, was the first to identify and discuss, at the end of 19th century, what we know today as the “factors of soil formation”. He introduced the idea that soil is not something inert and stable, but it develops and evolves under the influence of climatic agents and vegetation that operate over time on a given geological substrat