Nas últimas décadas as mudanças climáticas foram evidenciadas pelo aumento da temperatura global, diminuição dos estoques de carbono terrestres, associados ao aumento nas emissões de gases de efeito estufa (GEE). A floresta Amazônica é o maior bioma tropical do mundo e desenvolve serviços ambientais estratégicos no planeta. Entretanto, há mais de duas décadas que o desmatamento na Amazônia impulsiona as emissões globais de GEE, diminuindo o armazenamento de carbono do solo com alterações na dinâmica nas populações microbianas e nos ciclos biogeoquimicos pela mudança de uso da terra. O objetivo desse estudo foi avaliar as alterações temporais dos atributos químicos do solo, quantificar as emissões de CO2, CH4 e N2O e verificar as alterações na estrutura bacteriana do solo após o corte e queima de vegetação nativa na Amazônia. O estudo foi desenvolvido em área de vegetação nativa no norte do estado de Rondônia, região sul da Amazônia no Brasil. A área de estudo consistiu-se de quatro hectares, onde foi realizado o corte e queima em 2,25 hectares. Foram realizadas amostragens para avaliação da fertilidade do solo e estoques de carbono (C) e nitrogenio (N) nas profundidades de 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40-50, 50-60, 60-80 e 80-100 cm. As coletas foram realizadas em vegetação nativa e aos 2, 30, 60, 90, 120, 240 e 365 dias após corte e queima. Foram determinados os atributos pH, Al, H+Al, Ca, Mg, K, P, C, N e calculados os valores de soma de bases, CTC, V % e m %. As coletas para quantificar as emissões dos GEE foram realizadas simultaneamente na área de vegetação nativa e no hectare central da área de corte e queima aos 19, 31, 48, 61 e 81 dias após corte e 2 , 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 e 350 dias após queima, com amostragens aos 0, 20, 40 e 60 minutos. Os atributos microbiológicos do solo foram avaliados pela técnica de T-RFLP com amostragens realizadas simultaneas nas duas áreas, aos 32 e 62 dias após o corte e aos 2, 15, 30, 45, 60, 90, 120, e 360 dias após queima da biomassa vegetal. Foi verificado rápido aumento da fertilidade do solo e diminuição da acidez e teores de Al+3 após a queima, entretanto esse efeito foi pouco persistente, retornando ao status inicial do solo após um ano. Houve redução de 30 % nos estoques de C e N do solo no final do estudo, evidenciando os efeitos deletérios da mudança do uso da terra nos atributos químicos do solo. Foi registrado redução de 50 % das emissões de CO2 equivalente após o corte, comparada à vegetação nativa e reduções nas emissões de GEE de 35 % após um ano de estudo. Verificou-se na camada superficial, alterações significativas na estrutura da comunidade bacateriana do solo em decorrência do impacto do fogo e das alterações nos atributos químicos em função da deposição superficial de cinzas no solo, entretanto não foi verificada alterações significativa nas camadas abaixo de 5 cm. Este estudo forneceu importantes informações para o entendimento dos impactos e as alterações causadas pelo processo de conversão florestal tropical pelo corte e queima de vegetação nativa na Amazônia. / In recent decades, climate change has been evidenced by the increase in global temperature and the decrease in terrestrial carbon stocks, associated with an increase in greenhouse gas (GHG) emissions. The Amazon rainforest is the largest tropical biome in the world and develops strategic environmental services on the planet. However, for more than two decades, deforestation in Amazon has driven global GHG emissions, reducing soil carbon storage with changes in microbial populations dynamics and in biogeochemical cycles due to land use change. The objective of this study was to evaluate the temporal alterations of soil chemical attributes, quantify CO2, CH4 and N2O emissions and verify changes in soil bacterial structure, due to the slash and burn of the native vegetation in Amazon. The study was developed in an area of native vegetation in the north of Rondônia state, southern region of Amazon in Brazil. The study area consisted of 4 hectares, where it was cut and burned in 2.25 hectares. Samples were collected to evaluate soil fertility and carbon (C) and nitrogen (N) stocks at the depths of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40- 50, 50-60, 60-80 and 80-100 cm. These samples were collected in native vegetation at 2, 30, 60, 90, 120, 240 and 365 days after cutting and burning. The attributes pH, Al, H + Al, Ca, Mg, K, P, C, N were determined and the values of base sum, CEC, base saturation and aluminum saturation were calculated. The samples to quantify GHG emissions were carried out simultaneously in the native vegetation area and in the central hectare of the cutting and burning area at 19, 31, 48, 61 and 81 days after cutting and 2, 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 and 350 days after burning, with samples at 0, 20, 40 and 60 minutes. The microbiological attributes of the soil were evaluated by T-RFLP technique with simultaneous samplings in the two areas, at 32 and 62 days after cutting and at 2, 15, 30, 45, 60, 90, 120, and 360 days after plant biomass burning. A rapid increase in soil fertility and a decrease in acidity and Al+3 contents after burning were verified, however this effect was not persistent, returning to the initial soil status after one year. There was a 30 % reduction in soil C and N stocks at the end of the study, evidencing the deleterious effects of land use change on soil chemical attributes. Also, a 50 % reduction in CO2 emissions after cutting, compared to native vegetation and, a 35 % reduction in GHG emissions after one year of study, were observed. We verified in the surface layer, significant alterations in the soil bacteria structure due to the fire impact and the changes in the chemical attributes, such as surface deposition of ashes. However, we did not verified significant changes in the layers lower than 5 cm. Our study provided important information for understanding the impacts and changes of the tropical forest conversion process by slash and burning native vegetation in Amazon.

<p>Ово истраживање има за циљ да процени резерве органског угљеника у земљишту и представи његову просторну дистрибуцију у земљиштима Републике Србије, као и да утврди зависност садржаја органског угљеника у земљишту од типа земљишта, температуре, падавина, надморске висине, начина коришћења земљишта и морфогенетских карактеристика рељефа. Резерве органског угљеника у земљишту процењене су за слој 0-30 cm и 0-100 cm дубине на основу резултата из базе података уз коришћење педолошке карте и карте коришћења земљишта. За потребе утврђивања зависности садржаја органског угљеника и типа земљишта педолошка карта Србије је прилагођена WRB класификацији и садржи 15.437 полигона. Примењена методологија за процену резерве органског угљеника за дату дубину је базирана на сумирању резерве органског угљеника по слојевима земљишта која се добија на основу запреминске масе, вредности садржаја органског угљеника и дебљине слоја. Прорачун је урађен за сваки профил посебно, затим је урађена калкулација за сваку референтну групу земљишта на основу резултата средњих вредности садржаја органског угљеника до 30 cm и 100 cm дубине за главне референтне групе и њихових површина. На основу површина референтних група земљишта, површине Републике Србије и вредности садржаја за сваку референтну групу, добијене су укупне резерве органског угљеника до 30 cm дубине које износе 0,71 Pg. Резултати анализе резерве органског угљеника до 100 cm дубине показују вредност 1,16 Pg.<br />На основу Corine Land Cover (CLC) базе података за 2006. годину издвојене су површине главних категорија начина коришћења земљишта. На основу резултата средњих вредности садржаја органског угљеника до 30 и 100 cm дубине и површине коју заузима Corine Land Cover категорија начина коришћења земљишта израчуната је укупна вредност резерве органског угљеника за пољопривредна земљишта, шуме и полуприродна подручја и вештачке површине.<br />Резултати показују да су резерве органског угљеника у оквиру категорије пољопривредних површина 303,22 x 1012g (Tg) до 30 cm дубине и 600,25 x 1012g (Tg) до 100 cm дубине. Категорије шуме и полуприродна подручја имају резерве од основних климатских елемената температуре и падавина и надморске висине показује да постоји средње јака до јака статистичка зависност у оквиру испитивања реализованих до 30 и 100 cm дубине.</p><p>органског угљеника 345,26 x 1012g (Tg) угљеника до 30 cm и 457,55 x 1012g (Tg) до 100 cm дубине. Резултати показују вредности резерве органског угљеника у категорији вештачке површине која углавном обухватају локалитете у оквиру зелених урбаних подручја и рекреационих површина 19,21 x 1012g (Tg) до 30 cm и 41,50 x 1012g (Tg) до 100 cm дубине.<br />Анализа садржаја резерве органског угљеника према начину коришћења земљишта показује да су вредности садржаја органског угљеника веће у шумама и полуприродним подручјима у односу на пољопривредне површине и то за 40,71 % до 30 cm, односно за 11,43 % до 100 cm дубине. Прорачун губитка резерве органског угљеника у земљишту на подручјима где је извршена пренамена пољопривредних површина, шума и полуприродних подручја у урбано земљиште, без категорије зелена урбана подручја, у периоду 1990-2006. године показује укупну вредности од 0,92 Mt С, односно 1,49 Mt С за дубинe до 30 cm, односно до 100 cm.<br />Утврђивање статистичке зависности садржаја органског угљеника у земљиштуод основних климатских елемената температуре и падавина и надморске висине показује да постоји средње јака до јака статистичка зависност у оквиру испитивања реализованих до 30 и 100 cm дубине.</p><p>Прорачун садржаја резерве органског угљеника у земљишту у зависности од морфометријских карактеристика рељефа показујe да резерва садржаја органског угљеника у земљишту расте са порастом надморске висине. Највеће средње вредности садржаја измерене су на терену који обухвата планине са надморским висинама од 1.000-2.000 m и који обухвата 11,5 % територије Републике Србије</p> / <p>Ovo istraživanje ima za cilj da proceni rezerve organskog ugljenika u zemljištu i predstavi njegovu prostornu distribuciju u zemljištima Republike Srbije, kao i da utvrdi zavisnost sadržaja organskog ugljenika u zemljištu od tipa zemljišta, temperature, padavina, nadmorske visine, načina korišćenja zemljišta i morfogenetskih karakteristika reljefa. Rezerve organskog ugljenika u zemljištu procenjene su za sloj 0-30 cm i 0-100 cm dubine na osnovu rezultata iz baze podataka uz korišćenje pedološke karte i karte korišćenja zemljišta. Za potrebe utvrđivanja zavisnosti sadržaja organskog ugljenika i tipa zemljišta pedološka karta Srbije je prilagođena WRB klasifikaciji i sadrži 15.437 poligona. Primenjena metodologija za procenu rezerve organskog ugljenika za datu dubinu je bazirana na sumiranju rezerve organskog ugljenika po slojevima zemljišta koja se dobija na osnovu zapreminske mase, vrednosti sadržaja organskog ugljenika i debljine sloja. Proračun je urađen za svaki profil posebno, zatim je urađena kalkulacija za svaku referentnu grupu zemljišta na osnovu rezultata srednjih vrednosti sadržaja organskog ugljenika do 30 cm i 100 cm dubine za glavne referentne grupe i njihovih površina. Na osnovu površina referentnih grupa zemljišta, površine Republike Srbije i vrednosti sadržaja za svaku referentnu grupu, dobijene su ukupne rezerve organskog ugljenika do 30 cm dubine koje iznose 0,71 Pg. Rezultati analize rezerve organskog ugljenika do 100 cm dubine pokazuju vrednost 1,16 Pg.<br />Na osnovu Corine Land Cover (CLC) baze podataka za 2006. godinu izdvojene su površine glavnih kategorija načina korišćenja zemljišta. Na osnovu rezultata srednjih vrednosti sadržaja organskog ugljenika do 30 i 100 cm dubine i površine koju zauzima Corine Land Cover kategorija načina korišćenja zemljišta izračunata je ukupna vrednost rezerve organskog ugljenika za poljoprivredna zemljišta, šume i poluprirodna područja i veštačke površine.<br />Rezultati pokazuju da su rezerve organskog ugljenika u okviru kategorije poljoprivrednih površina 303,22 x 1012g (Tg) do 30 cm dubine i 600,25 x 1012g (Tg) do 100 cm dubine. Kategorije šume i poluprirodna područja imaju rezerve od osnovnih klimatskih elemenata temperature i padavina i nadmorske visine pokazuje da postoji srednje jaka do jaka statistička zavisnost u okviru ispitivanja realizovanih do 30 i 100 cm dubine.</p><p>organskog ugljenika 345,26 x 1012g (Tg) ugljenika do 30 cm i 457,55 x 1012g (Tg) do 100 cm dubine. Rezultati pokazuju vrednosti rezerve organskog ugljenika u kategoriji veštačke površine koja uglavnom obuhvataju lokalitete u okviru zelenih urbanih područja i rekreacionih površina 19,21 x 1012g (Tg) do 30 cm i 41,50 x 1012g (Tg) do 100 cm dubine.<br />Analiza sadržaja rezerve organskog ugljenika prema načinu korišćenja zemljišta pokazuje da su vrednosti sadržaja organskog ugljenika veće u šumama i poluprirodnim područjima u odnosu na poljoprivredne površine i to za 40,71 % do 30 cm, odnosno za 11,43 % do 100 cm dubine. Proračun gubitka rezerve organskog ugljenika u zemljištu na područjima gde je izvršena prenamena poljoprivrednih površina, šuma i poluprirodnih područja u urbano zemljište, bez kategorije zelena urbana područja, u periodu 1990-2006. godine pokazuje ukupnu vrednosti od 0,92 Mt S, odnosno 1,49 Mt S za dubine do 30 cm, odnosno do 100 cm.<br />Utvrđivanje statističke zavisnosti sadržaja organskog ugljenika u zemljištuod osnovnih klimatskih elemenata temperature i padavina i nadmorske visine pokazuje da postoji srednje jaka do jaka statistička zavisnost u okviru ispitivanja realizovanih do 30 i 100 cm dubine.</p><p>Proračun sadržaja rezerve organskog ugljenika u zemljištu u zavisnosti od morfometrijskih karakteristika reljefa pokazuje da rezerva sadržaja organskog ugljenika u zemljištu raste sa porastom nadmorske visine. Najveće srednje vrednosti sadržaja izmerene su na terenu koji obuhvata planine sa nadmorskim visinama od 1.000-2.000 m i koji obuhvata 11,5 % teritorije Republike Srbije</p> / <p>The aim of this study was to quantify current SOC stocks and present the spatial distribution of organic carbon (SOC) in the soils of Republic of Serbia. The relation of SOC content to soil type, temperature, precipitation, altitude, land use and topography was investigated. Organic carbon stocks were estimated for soil layers 0-30 cm and 0-100 cm based on the results from a database and using soil and land use maps.<br />To establish the relationship between organic carbon content and soil type, a soil map of Serbia was adapted to the WRB classification and divided into 15,437 polygons (map units). The methodology for SOC stocks estimation was based on bulk density, organic carbon content and thickness of the analyzed soil layers. We calculated the values for each reference soil group based on mean values of SOC at 0-30 and 0-100 cm in the main reference groups and their areas. Based on the size of the reference groups, total area of Republic of Serbia, and the SOC values for each reference group, we calculated the total SOC stocks. The obtained values for the soil layers 0-30 cm and 0-100 cm amounted to 0,71 Pg and 1,16 Pg respectively.<br />Using Corine Land Cover (CLC) database for 2006, we defined areas of the major categories of land use. Based on the obtained mean values of organic carbon content at 0-30 and 0-100 cm and the areas indicated by Corine Land Cover categories of land use, we calculated the organic carbon stocks in agricultural land, forest land, semi-natural areas, and artificial areas. The results showed that the organic carbon stocks in the category of agricultural land were 303.22 x 1012 g (Tg) and 600.25 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. In the category of forests and semi-natural areas, the organic carbon stocks were 345.26 x 1012 g (Tg) and 457.55 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. In the category of artificial areas, which mainly included sites within urban green areas and recreational areas, the organic carbon stocks were 19.21 x 1012 g (Tg) and 41.50 x 1012 g (Tg) at 0-30 cm and 0-100 cm, respectively. The map of organic carbon distribution depending on land use method indicated that organic carbon stocks were higher in forests and semi-natural areas than in agricultural land, up to 40.71% and 11.43% at 0-30 cm and 0-100 cm, respectively.<br />SOC loss amount to 0,92 Mt С at 0-30 cm layer and 1,49 Mt С at 0-100 cm layer in the period 1990-2006 as a results of conversion from agricultural land, forestland and semi-natural areas to artificial areas.<br />For soil layers 0-30 and 0-100 cm, a medium to strong statistical relationship between temperature, precipitation and altitude and amount of organic carbon in soil is indicated. The soil organic carbon density was significantly affected by altitude. SOC content increased with increasing altitude.<br />The highest mean values of organic carbon content were found in the mountainous areas within the elevation of 1000-2000 m, which covers 11,5 % of the territory of the Republic of Serbia.</p>

O nitrogênio é o nutriente absorvido em maior quantidade pelo milho e o que mais influencia na produtividade de grãos, tendo sua dinâmica no sistema solo-planta condicionada pelo manejo. O trabalho foi desenvolvido na fazenda experimental da Faculdade de Engenharia de Ilha Solteira, UNESP, Selvíria-MS, em um Latossolo Vermelho distrófico, fase cerrado. Os objetivos do trabalho foram de avaliar a melhor dose e época de aplicação do N, na forma de uréia, no milho cultivado sob semeadura direta (SD) em sucessão à crotalária (CR) (Crotalaria juncea), milheto (MI) (Pennisetum americanum) ou solo em pousio na entressafra; quantificar o aproveitamento pelo milho do N da uréia e do N mineralizado dos resíduos vegetais da parte aérea da CR e do MI; avaliar o efeito dos adubos verdes no aproveitamento do N-uréia e vice-versa, e de averiguar o aproveitamento do N remanescente da uréia e dos adubos verdes pelo milho cultivado em SD no ano agrícola subseqüente. Foram conduzidos dois ensaios em áreas distintas e anexas, nos anos agrícolas de 2001/02 e de 2002/03, com a avaliação, nas respectivas áreas e ano agrícola subseqüente, 2002/03 e 2003/04, do aproveitamento pelo milho do N residual dos adubos verdes e do N do fertilizante e seu efeito sobre a produtividade do milho. O delineamento experimental utilizado foi o de blocos casualizados com 24 tratamentos e quatro repetições, dispostos em esquema fatorial incompleto (3 x 3 x 2) + 6 tratamentos adicionais (três tratamentos controles sem a aplicação de N e três tratamentos que receberam somente 30 kg ha-1 de N na semeadura, sobre CR, MI e solo em pousio. Os demais tratamentos constituíram-se pela combinação de três doses de N: 80, 130 e 180 kg ha-1, aplicando-se 30 kg ha-1 na semeadura e o restante em cobertura; três sistemas de cobertura do solo: CR e MI cultivados no inverno/primavera e o solo em pousio na entressafra, e duas épocas de aplicação do N: estádio quatro folhas ou estádio oito folhas. O fertilizante 15N-uréia foi aplicado nos tratamentos com 30 kg ha-1 de N na semeadura ou 50, 100 e 150 kg ha-1 de N em cobertura nos estádios quatro folhas ou oito folhas. A CR ou MI marcados com 15N foram utilizados somente nos tratamentos receberam o N no estádio quatro folhas, testemunha ou apenas 30 ha-1 de N na semeadura. A produtividade de grãos foi superior no milho em sucessão à CR, nos dois anos agrícolas, em relação ao cultivo em sucessão ao MI e ao solo pousio, que diferiram entre si com menor produtividade na sucessão MI-milho no primeiro ano agrícola e quando o N foi aplicado no estádio oito folhas no segundo. As épocas de aplicação do N não influenciaram no seu aproveitamento pelo milho, mas, a aplicação no estádio quatro folhas demonstrou ser mais viável economicamente quando o milho foi cultivado em sucessão ao MI e ao solo em pousio, e indiferente para o cultivo em sucessão à CR. O incremento na dose de fertilizante nitrogenado proporcionou aumento na quantidade de N na planta proveniente do fertilizante e diminuiu o seu aproveitamento, que foi em média de 53%, 49% e 44% para o milho cultivado em sucessão à CR, pousio e MI, respectivamente. O incremento na dose de fertilizante nitrogenado proporcionou aumento linear no aproveitamento pelo milho do N da CR, e quadrático no segundo ano agrícola para o N do MI, que foi em média de 15,60% 7,60%, respectivamente. A CR promoveu maior aproveitamento pelo milho do N da uréia comparada ao MI, que acumulou proporcionalmente maior quantidade de N proveniente do solo. O aproveitamento do N remanescente da parte aérea do MI e da CR pelo milho cultivado no ano agrícola subseqüente, foi inferior a 3,5% e 3%, respectivamente, da quantidade inicial, e o do N remanescente do fertilizante uréia foi inferior a 3% do aplicado inicialmente. / Nitrogen is the most absorbed nutrient by corn crop and most affect the grains yield, and its dynamic in soil-plant system is conditioned by management. The research was carried in the Experimental Farm of Faculty of Engineering, Sao Paulo State University (UNESP), Ilha Solteira, located in Selvíria-MS, in a dystrophic Red Latosol, cerrado phase, during 2001/02 and 2002/03 growing season. The objectives were to evaluate the best rate and time of N application, as urea, and N utilization by corn crop grown under no-tillage system in succession to sunnhemp (Crotalaria juncea L) (SU), millet (Pennisetum americanum) (MI) and fallow; to quantify the utilization of N from urea and mineralized SU and MI residues by corn crop; to evaluate the effect f green manure on urea N utilization by corn crop and vice-versa; and to investigate the utilization by corn crop of N remnant from previous year applied urea and green manure by corn crop grown subsequent year under no-tillage system. Two experiments were carried out in distinct nearby areas in 2001/02 e 2002/03, with the evaluation, in the respective areas and subsequent years, 2002/03 and 2003/04, of utilization by corn by corn of green manure and fertilizer remnant N and their effects on corn yield. The experimental design was randomized complete blocks, with 24 treatments and four replications in an incomplete factorial, (3 x 3 x 2) + 6 additional treatments (three without N application and three that received 30 kg N ha-1 at seeding); three N rates: 80, 130 and 180 kg N ha-1; tree preceding cover crops SU, MI grown during winter/spring season and fallow; two N application time: four leaves or eight leaves stage. The fertilizer 15N-urea was applied in the treatments 30 kg ha-1 of N at seeding or 50, 100 and 150 kg ha-1 topdressed at four leaves or eight leaves stages. SU or MI labeled with 15N were used only in the treatments that received N in the four leaves stage, control or those which received 30 ha-1 of N at seeding. The grains yield was higher in the corn in succession to SU, in both growing seasons, in relation to the cultivation in succession to MI and the fallow soil, that differed between them, with smaller productivity in the succession MI-corn in the first year and when N was applied at the eight leaves stage in the second. The N application times did not affect its utilization by the corn, but the application in four leaves stage demonstrated to be more economically viable when the corn was grown in succession to MI and the soil in fallow, and indifferent for the cultivation in succession to SU. The amount of N derived from fertilizer (Npdff) increased with increasing N rate and reduced the N utilization efficiency (NUE), in average 53%, 49% and 44% for the corn grown in succession to SU, fallow and MI, respectively. The increasing nitrogen fertilizer rate increased linearly the utilization by corn of N from SU, and adjusted to quadratic model in the second year for N from MI, in average 15.60% 7.60%, respectively. SU promoted larger utilization of urea N compared to MI, which accumulated proportionally larger amount of N derived from the soil than SU. The utilization of N remnant from above ground part of MI and of SU by the corn grown in the subsequent year was less than 3.5% and 3%, respectively, of the initial amount, and the remaining N of the urea fertilizer was less than 3% of initially applied amount.

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

Soil organic matter (SOM) contains about twice the amount of carbon in the atmosphere. With global changes, the potential shifts in SOM quantity and quality are a major concern. Due to its heterogeneity, SOM remains largely unknown in terms of its molecular composition and responses to climatic events. Traditional bulk soil analysis cannot depict the structural changes in SOM. This thesis applies two complementary molecular-level methods, i.e., SOM biomarker gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) spectroscopy, to examine the origin and degradation of various SOM components in grassland and temperate forest soils, and to investigate the shifts in microbial community and SOM composition with both laboratory- and field-simulated global changes, such as frequent freeze-thaw cycles, increasing soil temperatures, elevated atmospheric CO2 levels, and nitrogen (N) deposition. This thesis has several major findings. First, as the most active component in soil, microbial communities were sensitive to substrate availability changes resulting from prolonged soil incubation, freeze-thaw-induced cell lyses, N fertilization and increased plant inputs under elevated CO2 or soil warming. Microbial community shifts have direct impacts on SOM decomposition patterns. For instance, an increased fungal community was believed to contribute to the enhanced lignin oxidation in an in situ soil warming experiment as the primary degrader of lignin in terrestrial environments. Second, contrast to the conventional belief that aromatic structure was recalcitrant and stable in SOM, ester-bond aliphatic lipids primarily originating from plant cutin and suberin were preferentially preserved in the Canadian Prairie grassland soil profiles as compared with lignin-derived phenols. Cutin- and suberin-derived compounds also demonstrated higher stability during soil incubation. With an increased litter production under elevated CO2 or global warming, an enrichment of alkyl structures that had strong contributions from leaf cuticles was observed in the Duke Forest Free Air CO2 Enrichment (FACE) and soil warming experiments, suggesting an accumulation of plant-derived recalcitrant carbon in the soil. These results have significant implications for carbon sequestration and terrestrial biogeochemistry. Overall, this thesis represents the first of its kind to employ comprehensive molecular-level techniques in the investigation of SOM structural alterations under global changes.

Soil organic matter (SOM) contains about twice the amount of carbon in the atmosphere. With global changes, the potential shifts in SOM quantity and quality are a major concern. Due to its heterogeneity, SOM remains largely unknown in terms of its molecular composition and responses to climatic events. Traditional bulk soil analysis cannot depict the structural changes in SOM. This thesis applies two complementary molecular-level methods, i.e., SOM biomarker gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) spectroscopy, to examine the origin and degradation of various SOM components in grassland and temperate forest soils, and to investigate the shifts in microbial community and SOM composition with both laboratory- and field-simulated global changes, such as frequent freeze-thaw cycles, increasing soil temperatures, elevated atmospheric CO2 levels, and nitrogen (N) deposition. This thesis has several major findings. First, as the most active component in soil, microbial communities were sensitive to substrate availability changes resulting from prolonged soil incubation, freeze-thaw-induced cell lyses, N fertilization and increased plant inputs under elevated CO2 or soil warming. Microbial community shifts have direct impacts on SOM decomposition patterns. For instance, an increased fungal community was believed to contribute to the enhanced lignin oxidation in an in situ soil warming experiment as the primary degrader of lignin in terrestrial environments. Second, contrast to the conventional belief that aromatic structure was recalcitrant and stable in SOM, ester-bond aliphatic lipids primarily originating from plant cutin and suberin were preferentially preserved in the Canadian Prairie grassland soil profiles as compared with lignin-derived phenols. Cutin- and suberin-derived compounds also demonstrated higher stability during soil incubation. With an increased litter production under elevated CO2 or global warming, an enrichment of alkyl structures that had strong contributions from leaf cuticles was observed in the Duke Forest Free Air CO2 Enrichment (FACE) and soil warming experiments, suggesting an accumulation of plant-derived recalcitrant carbon in the soil. These results have significant implications for carbon sequestration and terrestrial biogeochemistry. Overall, this thesis represents the first of its kind to employ comprehensive molecular-level techniques in the investigation of SOM structural alterations under global changes.

[Truncated abstract] Relationships between the persistence of organic matter added to soil, the dynamics of soil organic carbon (C) and phosphorus (P) were examined in four experiments on lateritic soils of Western Australia. The main objective was to quantify the release of P following organic matter application in soils which have high P adsorbing capacity. Another objective was to confirm that due to its recalcitrant materials, the effect of peat lasted longer in soil than other sources of organic matter in terms of increasing plant-available P fractions. Three experiments were conducted under glasshouse conditions for various lengths of time, with nine- to twelve-month incubations to investigate these hypotheses. As expected, organic matter with lower C:N ratios than peat (lucerne hay) decomposed more rapidly compared with peat, and the most active mineralisation took place within the first three months of incubation. Soil organic-C (extracted by 0.5 M K2SO4) had a significant positive correlation with P extracted with 0.5 M NaHCO pH 8.53. For a higher application rate (120 ton ha-1), peat was better than wheat straw and lucerne hay in increasing extractable bicarbonate-P concentrations in soil, especially at incubation times up to 12 months. Throughout the experiment, peat was associated with a steady increase in all parameters measured. In contrast to peat, nutrient release from lucerne hay and wheat straw was rapid and diminished over time. There was a tendency for organic-C (either in the form of total extractable organic-C or microbial biomass-C) to steadily increase in soil with added peat throughout the experiment. Unlike wheat straw and lucerne hay, extractable organic-C from peat remained in soil and there was less C loss in the form of respiration. Therefore, peat persisted and sequestered C to the soil system for a longer time than the other source of organic matter. Freshly added organic matter was expected to have a greater influence on P transformation from adsorbed forms in lateritic soils than existing soil organic matter. By removing the existing soil organic matter, the effect of freshly applied organic matter can be determine separately from that of the existing soil organic matter for a similar organic-C content. In order to do this, some soil samples were combusted up to 450° C to eliminate inherent soil organic matter. The release of P was greater when organic-C from fresh organic matter was applied to combusted soils than in uncombusted soils that contained the existing soil organic matter. The exception only applied for parameters related to soil micro-organisms such as biomass-C and phosphatase. For such parameters, new soil organic matter did not create conditions favourable for organisms to increase in activity despite the abundance of organic matter available. More non-extractable-P was formed in combusted soils compared to bicarbonate-P and it contributed to more than 50% of total-P. As for the first experiment, peat also showed a constant effect in increasing bicarbonate extractable-P in the soil

Les sols de montagne constituent un réservoir majeur de carbone stocké sous forme de matière organique (carbone organique du sol, COS), potentiellement hautement vulnérable aux changements des conditions climatiques. Afin de comprendre les répercussions des changements des conditions climatiques sur la dynamique du COS des sols de montagne, cette thèse s'appuie sur une expérimentation de transplantation altitudinale de monolithes de sol de prairie subalpine calcaire, mise en place dans le Jura Suisse en 2009. Cette expérimentation permet de simuler deux scénarios réalistes de changements climatiques attendus au cours du 21éme siècle, visant à réchauffer et assécher le climat (+2°C et +4°C ; -20% et -40% de précipitations).La démarche conceptuelle de cette thèse a été d'étudier les effets des changements des conditions climatiques (variations saisonnières et manipulation climatique) au bout de quatre années d'expérimentation sur (i) la dynamique des communautés microbiennes et de leur activité enzymatique de décomposition du COS, (ii) la dynamique de différents pools de COS qui constituent la ressource énergétique des micro-organismes décomposeurs, (iii) les interactions s'établissant entre les communautés microbiennes et leurs ressources énergétiques et (iv) les stocks de COS du sol.Nos résultats montrent une très forte dynamique saisonnière du processus de décomposition microbienne se traduisant par de fortes activités enzymatiques de décomposition, une biomasse microbienne plus importante et une structure des communautés microbienne différente lors de la saison hivernale par rapport à la saison estivale. Ces résultats sont en lien avec la dynamique observée des pools les plus labiles du COS (C organique extractible à l'eau et C organique particulaire libre), et des modèles d'équations structurelles montrent que les conditions climatiques (variations saisonnières et manipulation climatique) modifient les interactions s'établissant entre les communautés microbiennes et leurs ressources pour contrôler la décomposition enzymatique du COS.Enfin, ce travail de thèse montre une forte diminution des concentrations en COS sous l'effet de la manipulation climatique, qui ne peut être expliquée par une décomposition microbienne accrue du COS. Au contraire, nos résultats suggèrent que la diminution de la concentration en COS pourrait être due à l'accélération des processus pédologiques naturels sous les scénarios de changement climatique au sein de ces sols calcaires de prairies subalpines, avec une décarbonatation accrue favorisant la lixiviation du carbone organique dissous et le lessivage du pool de COS associé aux argiles. Ces résultats inédits offrent de nouvelles perspectives de recherche sur les effets des changements climatiques sur l'évolution des stocks de COS. / Mountain soils stocks huge quantities of carbon as soil organic matter (SOM) which may be highly vulnerable to climate change and thus alter the atmospheric greenhouse gases concentration at a decadal timescale. To understand the effect of climate conditions on the dynamics of mountain soil organic carbon (SOC), a climate change experiment was set up in October 2009 in Swiss Jura subalpine grassland soils. The climate change experiment (soil transplantation) simulated two realistic climate change scenarios, with increased air temperatures ranging between 2 °C and 4 °C and decreased precipitation ranging between 20% and 40%. These changes reflect current predictions of climate change for the 21th century in temperate mountain regions.We studied the effect of climate conditions (climate manipulation and seasonal changes) after four years of climate experiment on (i) the dynamic of microbial decomposition, microbial abundance and community structure, (ii) the dynamic soil organic matter pools with contrasted turnover rate and representing the energetic resource of microbial communities, (iii) the interactions between microbial communities and soil organic matter pools and (iv) the soil organic carbon stocks.This work shows a strong seasonal dynamics of microbial decomposition with higher enzymatic activities, higher microbial abundance and shift of microbial community structure in winter than in summer. These results were linked to the seasonal organic matter labile pools dynamics. Moreover structural equation modeling shows that climate manipulation differently influences the drivers of SOC enzymatic decomposition in summer and winter.Finally, this work shows a strong decrease of soil organic carbon concentration under the climate change manipulation which cannot be explained by an increase of microbial activities. In contrast, our results suggest that the observed climate-induced decrease in bulk soil organic C content was due a SOC decrease in the most biogeochemically stable SOM fraction associated with a decrease in clay content and a decrease of soil calcareous concentration. Thus, our results hint more so towards an effect of SOM leaching (Gavazov, 2013) to explain the climate effect on SOC content than an effect of microbial and/or plant activities.

Le sol est une des composantes essentielles au soutien du fonctionnement de l’écosystème. Il est lesupport de la production primaire, un habitat pour la diversité biologique et remplit de nombreux processus écologiques. Les activités anthropiques, et parmi elles, les pratiques agricoles intensives, ont conduit à des déséquilibres au sein du sol causant un fort déclin de leur biodiversité. En réponse à ces effets, de nouvelles pratiques agricoles ont été développées pour préserver les sols et les services écosystémiques qu’ils fournissent. Ces pratiques dites innovantes s’appuient principalement sur la réduction du travail du sol, une gestion intégrée des résidus de culture, l’installation d’un couvert végétal permanent ou encore l’introduction de légumineuses dans les rotations de culture. C’est dans ce contexte de mutation des pratiques agricoles que s’inscrit ce sujet de thèse qui vise à mieux comprendre les effets de l’adoption de ces gestions innovantes sur (i) la diversité des communautés de la macro- et de la mésofaune du sol et (ii) sur le fonctionnement du sol en termes de stockage ducarbone organique (source de nourriture de base), de structure du sol et de distribution de la taille des pores (milieu de vie). Au cours des différents chapitres de ce travail, nous avons mis en évidence trois actions liées à des pratiques agricoles innovantes combinant des approches expérimentales in et ex situ. L’objectif de la première action visait à étudier l’effet combiné de l’introduction de légumineuse (féverole) et de la réduction du travail du sol sur le compartiment endogé. Pour y répondre, nous avons développé une conception expérimentale empirique faite avec la combinaison des situations rencontrées dans les fermes. Nos résultats ont montré que l’interaction entre les deux pratiques innovantes n’a pas entrainé d'augmentation significative de la diversité de la faune du sol. Les fonctions microbiennes ainsi que la dynamique du carbone (C) et de l’azote (N) ne semblent pas non plus être affectées par ces pratiques. Il s’avère que les effets bénéfiques de ces pratiques innovantes ne peuvent être envisagés sans prendre en compte la manière dont elles sont mises en oeuvre à l’échelle des rotations culturales et des itinéraires techniques. Cela nous a permis de valoriser une seconde action dont l’objectif était de suivre dans les mêmes conditions pédoclimatiques et mêmes itinéraires techniques, l'effet à long terme (quatre ans) de cinq régimes de gestion différents sur les communautés de faune du sol. Les traitements comprenaient des combinaisons de différentes cultures (annuelles, vivaces), de différents taux de fertilisation azotée (ajout d'azote, azote réduit),incorporation ou élimination de résidus de culture et différentes intensités de labour (labour vs. travail superficiel). Les résultats ont montré que la réduction de l’intensité du travail du sol a favorisé la diversité des collemboles et ses groupes fonctionnels grâce à l’amélioration des conditions de l’habitat à travers l’augmentation de la biomasse microbienne de carbone (source trophique). Par ailleurs, les autres composantes de la gestion, soit la « réduction des apports d’azote » et la « restitution / exportation des résidus de culture», n’ont pas eu d’effet sur les collemboles (abondance et richesse), notamment sur ceux vivants dans le sol, qu'ils soient hémi ou euédaphiques. Toutefois, cette étude démontre que la dissemblance dans la composition des assemblages de collemboles augmente avec la différenciation temporelle des pratiques agricoles et le travail du sol est le premier facteur responsable de cette trajectoire. Cette assertion a donné lieu à une troisième action dont l’objectif était de suivre sur une saison de végétation la conversion de la perturbation mécanique résultant du travail du sol sur la résistance et résilience fonctionnelle des assemblages biotiques édaphiques. / Soil is one of the essential components supporting the functioning of the ecosystem. It is the support of primary production; an habitat for biodiversity, and it fulfills many ecological processes. Human activities, including intensive agricultural practices, have led to impaired the soil causing a sharp decline in their biodiversity. In response to these effects, new agricultural practices have been developed to preserve the soils and the ecosystem services they provide. These so-called innovative practices rely mainly on the reduction of tillage, integrated management of crop residues, the installation of permanent plant cover or the introduction of legumes into crop rotations. It is in this context of changes in agricultural practices that this thesis topic lays. This thesis aims to better understand the effects of the adoption of these innovative management practices on (i) the diversity of the macro and mesofauna communities soil and (ii) soil functioning in terms of organic carbon storage (basic food source), soil structure and pore size distribution (living environment). During the different chapters of this work, we highlighted three actions related to innovative agricultural practices combining in situ and ex situ experimental approaches. The aim of the first action was to study the combined effect of the introduction of legume (faba bean) and the reduction of tillage on the endogenous compartment. To answer this question, we developed an empirical experimental design made with the combination of situations encountered on farms. Our results showed that theinteraction between the two innovative practices did not result in a significant increase in the diversity of soil fauna. Microbial functions and the dynamics of carbon (C) and nitrogen (N) also do not seem to be affected by these practices. It turns out that the beneficial effects of these innovative practices cannot be considered without taking into account how they are implemented at the scale of crop rotations and technical itineraries. This allowed us to promote a second action whose objective was to follow, under the same pedoclimatic conditions and the same technical itineraries, the long-term effect (four years) of five different management regimes on the communities of soil fauna. Treatments included combinations of different crops, different rates of nitrogen fertilization, incorporation or removal of crop residues and different plowing intensities. The results showed that the reduction of tillage intensity favored the diversity of Collembola and its functional groups by improving habitatconditions through the increase of microbial carbon biomass (trophic source). In addition, the other components of management, namely the "reduction of nitrogen inputs" and the "restitution / export of crop residues", had no effect on springtails (abundance and wealth), in particular on those living in the soil, whether hemi or euedaphic. However, this study demonstrates that the dissimilarity in the composition of Collembola assemblages increases with the temporal differentiation of agricultural practices, and tillage was the main factor responsible for this trajectory.

The main aim of this thesis was to assess the status of soil organic carbon in newly shaped soils called Velká podkrušnohorská dump in the Sokolov district and evaluate the information in relation to the physic-chemical properties of soils. Another objective was to determine the relationship between the stable and labile fractions of soil organic carbon. The amount of soil carbon (stable fraction) was measured in the solid soil samples and there was the analysis of basic physic-chemical parameters of the soil performed. The highest concentration of soil carbon was measured in the stand alders and larch. The amount of soil carbon (labile fraction) was measured in the water extract. The highest values were measured in the stand silver birch and alders. Based on this data the quotient of the labile fraction from the stable fraction was determined and the correlation of the labile and stable fractions was made. It was found out that the higher quality soils are located at the leafy trees, but it leads to leaching of organic carbon. The bulk density and coarse-grained soil fraction was determined from the physical properties and these data were used to calculate the stock of soil organic carbon. The highest value was measured in deciduous forests with small-leaved linden, in coniferous forests with larch. The stocks of soil organic carbon were converted into codes by land cover categories and the thematic map was created. It was found out that the leafy trees are much more appropriate for forest restoration, because they are characterized by the rapid initial growth, easily degradable plant litter and stable form humus. Deciduous forests are also characterized by more developed soil substrate, which is however unstable.