To date, most studies on the effectiveness of geotextiles on soil erosion rates were conducted in laboratory experiments for <1 h. Hence, at Hilton, East Shropshire, UK, this study investigated the effectiveness of palm-mat geotextiles (Borassus and Buriti mats) in reducing rainsplash erosion, runoff and soil loss and changing selected soil properties under field conditions over two years (January 2007-January 2009). Mat-cover effects on rainsplash erosion were studied in two sets on a loamy sand soil (0o slope). In both sets, six randomly-selected plots (each 1 m2) were completely matcovered and six were bare. Unlike Buriti mats, Borassus mat-cover on bare soil significantly (P<0.001) decreased rainsplash erosion (by ~89%). Duplicate runoff plots (10 x 1 m on a 15o slope) had five treatments (bare, permanent grass, Borassus completely-cover, Borassus buffer strip and Buriti buffer strip). Using Borassus buffer strips (area coverage ~10%) on bare soil decreased runoff by ~71% (P>0.05) and soil erosion by ~92% (P<0.001). Borassus buffer strip, Buriti buffer strip and Borassus completely-covered plots had similar effects in decreasing runoff and soil loss. However, the longevity of Borassus mats was ~twice that of Buriti mats. Despite physical protection, runoff control and sediment entrapment, biomat buffer zones may considerably alter and protect flow direction by presenting barriers and creating several cross-drains. Except Borassus completely-covered plots, all plots had significant (P<0.05) increases in topsoil (0-5 cm) bulk density and decreased aggregate stability. However, buffer strips were more effective in trapping fine particles than Borassus completely-covered plots. No treatments had significant (P>0.05) effects on changes in pH, soil organic matter, total soil carbon or N. Plots with Borassus mats significantly (P<0.05) increased total P and decreased total Ca. Treatments had no significant effects on changes in total S, Mg, Zn, Cu, Fe, Mn, Mo or Cl concentrations. Borassus buffer strips can effectively conserve soil and water and improve and maintain selected soil properties, with results similar to Borassus completely-covered plots. The mechanisms explaining the effectiveness of buffer zones require further studies under varied pedo-climatic conditions.

A deficiência de nitrogênio tem sido apontada como uma das principais causas da degradação de pastagens, mas o suprimento de enxofre também é relevante nessa situação. Objetivou-se avaliar os efeitos das combinações entre doses de nitrogênio e de enxofre em características produtivas, fisiológicas e nutricionais da planta e nos atributos químicos do solo, na implantação do capim-Marandu (Brachiaria brizantha cv. Marandu) em Neossolo Quartzarenico proveniente de área de capim-Braquiária (Brachiaria decumbens) em degradação, com baixo teor de matéria orgânica. O experimento foi conduzido em casa-de-vegetação, em Piracicaba, Estado de São Paulo, no período de dezembro de 2004 a abril de 2005. Utilizou-se esquema fatorial 52 fracionado, com 13 combinações para as doses de nitrogênio e enxofre, em mg dm-3: 0-0; 0-20; 0-40; 100-10; 100-30; 200-0; 200-20; 200-40; 300-10; 300-30; 400-0; 400- 20 e 400-40, as quais foram distribuídas em delineamento estatístico de blocos ao acaso, com quatro repetições. Foram realizados três cortes nas plantas e a cada corte era coletada uma amostra de solo de cada unidade experimental. Após o terceiro corte as raízes foram separadas do solo e tiveram o comprimento e a superfície avaliados. Os resultados demonstraram que o fornecimento de nitrogênio foi fundamental para o crescimento inicial e adequado estabelecimento do capim-Marandu. Quando o nitrogênio foi fornecido em altas doses foi necessário cuidar do fornecimento de enxofre para a maximização da produção do capim- Marandu, bem como para o valor SPAD, a concentração de nitrogênio e de enxofre nas lâminas de folhas recém-expandidas e parte aérea e para a relação N:S na parte aérea. O valor SPAD refletiu diretamente a concentração de nitrogênio nas lâminas de folhas recém-expandidas do capim. O nitrogênio foi determinante para a maximização da massa seca de raízes, do comprimento do sistema radicular, da relação nitrogênio e enxofre no sistema radicular do capim- Marandu e dos teores de nitrato e amônio no solo suportando o capim-Marandu. A aplicação de enxofre proporcionou aumento da concentração de enxofre na parte aérea e no sistema radicular do capim, e dos teores de sulfato e enxofre total no solo com a presença do capim. A relação adequada entre as doses de nitrogênio e de enxofre para a maximização das características produtivas do capim-Marandu esteve no intervalo entre doses de 8:1 a 11:1. / Nitrogen deficiency has been mentioned as one of the main reasons for pasture degradation, but sulphur supply also is considerable in such cases. The objective was to evaluate the effects of combinations between nitrogen and sulphur rates in productive, physiological and nutritional plant characteristics and in some soil parameters at the establishment of Marandu grass in Typic Quartzipsamment with low organic matter concentration taken from a degrading Signal grass pasture. The experiment was carried out in a greenhouse, at Piracicaba, Satate of São Paulo, Brazil, from December 2004 to April 2005. A fractionated 52 factorial was used, with 13 combinations for the nitrogen and sulfur rates, in mg dm-3: 0-0; 0-20; 0-40; 100-10; 100-30; 200- 0; 200-20; 200-40; 300-10; 300-30; 400-0; 400-20 e 400-40, which were set in a randomized block design, with four replications. Plants were harvested three times, and at each harvest a soil sample was taken from each experimental unit. Following the third harvest, roots were separated from the soil and their length and surface were measured. The results showed that nitrogen supply was essential for the initial growth and adequate establishment of Marandu grass. When nitrogen was supplied at high rates, it was necessary a special care with sulphur supply to maximize dry matter yield, SPAD value, nitrogen and sulphur concentrations in the newly expanded leaves and plant tops and N:S ratio in plant tops. SPAD value was directly related to nitrogen concentration in the newly expanded leaves. Nitrogen was also decisive for maximizing roots dry weight and length, N:S ratio in the roots, and nitrate and ammonium in the soil with the grass. Sulphur application resulted in increase in the sulphur concentration in the grass tops and roots, and in the sulphate and total sulphur in the soil supporting the grass. Adequate ratio between nitrogen and sulphur rates to maximize the productive characteristics of Marandu grass was in the range of 8:1 a 11:1.

A deficiência de nitrogênio tem sido apontada como uma das principais causas da degradação de pastagens, mas o suprimento de enxofre também é relevante nessa situação. Objetivou-se avaliar os efeitos das combinações entre doses de nitrogênio e de enxofre em características produtivas, fisiológicas e nutricionais da planta e nos atributos químicos do solo, na implantação do capim-Marandu (Brachiaria brizantha cv. Marandu) em Neossolo Quartzarenico proveniente de área de capim-Braquiária (Brachiaria decumbens) em degradação, com baixo teor de matéria orgânica. O experimento foi conduzido em casa-de-vegetação, em Piracicaba, Estado de São Paulo, no período de dezembro de 2004 a abril de 2005. Utilizou-se esquema fatorial 52 fracionado, com 13 combinações para as doses de nitrogênio e enxofre, em mg dm-3: 0-0; 0-20; 0-40; 100-10; 100-30; 200-0; 200-20; 200-40; 300-10; 300-30; 400-0; 400- 20 e 400-40, as quais foram distribuídas em delineamento estatístico de blocos ao acaso, com quatro repetições. Foram realizados três cortes nas plantas e a cada corte era coletada uma amostra de solo de cada unidade experimental. Após o terceiro corte as raízes foram separadas do solo e tiveram o comprimento e a superfície avaliados. Os resultados demonstraram que o fornecimento de nitrogênio foi fundamental para o crescimento inicial e adequado estabelecimento do capim-Marandu. Quando o nitrogênio foi fornecido em altas doses foi necessário cuidar do fornecimento de enxofre para a maximização da produção do capim- Marandu, bem como para o valor SPAD, a concentração de nitrogênio e de enxofre nas lâminas de folhas recém-expandidas e parte aérea e para a relação N:S na parte aérea. O valor SPAD refletiu diretamente a concentração de nitrogênio nas lâminas de folhas recém-expandidas do capim. O nitrogênio foi determinante para a maximização da massa seca de raízes, do comprimento do sistema radicular, da relação nitrogênio e enxofre no sistema radicular do capim- Marandu e dos teores de nitrato e amônio no solo suportando o capim-Marandu. A aplicação de enxofre proporcionou aumento da concentração de enxofre na parte aérea e no sistema radicular do capim, e dos teores de sulfato e enxofre total no solo com a presença do capim. A relação adequada entre as doses de nitrogênio e de enxofre para a maximização das características produtivas do capim-Marandu esteve no intervalo entre doses de 8:1 a 11:1. / Nitrogen deficiency has been mentioned as one of the main reasons for pasture degradation, but sulphur supply also is considerable in such cases. The objective was to evaluate the effects of combinations between nitrogen and sulphur rates in productive, physiological and nutritional plant characteristics and in some soil parameters at the establishment of Marandu grass in Typic Quartzipsamment with low organic matter concentration taken from a degrading Signal grass pasture. The experiment was carried out in a greenhouse, at Piracicaba, Satate of São Paulo, Brazil, from December 2004 to April 2005. A fractionated 52 factorial was used, with 13 combinations for the nitrogen and sulfur rates, in mg dm-3: 0-0; 0-20; 0-40; 100-10; 100-30; 200- 0; 200-20; 200-40; 300-10; 300-30; 400-0; 400-20 e 400-40, which were set in a randomized block design, with four replications. Plants were harvested three times, and at each harvest a soil sample was taken from each experimental unit. Following the third harvest, roots were separated from the soil and their length and surface were measured. The results showed that nitrogen supply was essential for the initial growth and adequate establishment of Marandu grass. When nitrogen was supplied at high rates, it was necessary a special care with sulphur supply to maximize dry matter yield, SPAD value, nitrogen and sulphur concentrations in the newly expanded leaves and plant tops and N:S ratio in plant tops. SPAD value was directly related to nitrogen concentration in the newly expanded leaves. Nitrogen was also decisive for maximizing roots dry weight and length, N:S ratio in the roots, and nitrate and ammonium in the soil with the grass. Sulphur application resulted in increase in the sulphur concentration in the grass tops and roots, and in the sulphate and total sulphur in the soil supporting the grass. Adequate ratio between nitrogen and sulphur rates to maximize the productive characteristics of Marandu grass was in the range of 8:1 a 11:1.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.

<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>

Soils are the largest pool of carbon (C) in terrestrial ecosystems and store 1500 Gt of C in their soil organic matter (SOM). SOM is a dynamic, complex and heterogeneous mixture, which influences soil quality through a wide range of soil properties. Labile SOM comprises a small fraction of total SOM (approximately 5%), but due to its rapid turnover has been suggested to be most vulnerable to loss following soil disturbance. This research was undertaken to examine the consequences of soil disturbance on labile SOM, its availability and protection in soils using the isotopic analysis of soil-respired CO₂ (δ¹³CO₂). A range of soils were incubated in both the short- (minutes) and long-term (months) to assess changes in labile SOM. Shifts in soil-respired δ¹³CO₂ over the course of soil incubations were found to reflect changes in labile substrate utilisation. There was a rapid depletion of δ¹³CO₂ (from a starting range between -22.5 and -23.9‰, to between -25.8 and -27.5‰) immediately after soil sampling. These initial changes in δ¹³CO₂ indicated an increased availability of labile SOM following the disturbance of coring the soil and starting the incubations. Subsequently δ¹³CO₂ reverted back to the initial, relatively enriched starting values, but this took several months and was due to labile SOM pools becoming exhausted. A subsequent study was undertaken to test if soil-respired δ¹³CO₂ values are a direct function of the amount of labile SOM and soil physical conditions. A range of pasture soils were incubated in the short-term (300 minutes), and changes in soil-respired δ¹³CO₂ were measured along with physical and chemical soil properties. Equilibrium soil-respired δ¹³CO₂, observed after the initial rapid depletion and stabilisation, was a function of the amount of labile SOM (measured as hot water extractable C, HWEC), total soil C and soil protection capacity (measured as specific soil surface area, SSA). An independent experimental approach to assess the effect of SSA, where labile SOM was immobilised onto allophane – a clay mineral with large, active surface area – indicated limited availability of labile SOM through more enriched δ¹³CO₂ (in a range between -20.5 and -20.6 ‰) and a significant (up to three times) reduction in HWEC. In the third study, isotopic measurements were coupled with CO₂ evolution rates to directly test whether equilibrium soil-respired δ¹³CO₂ can reflect labile SOM vulnerability to loss. Soils were sampled from an experimental tillage trial with different management treatments (chemical fallow, arable cropping and permanent pasture) with a range of C inputs and soil disturbance regimes. Soils were incubated in the short- (300 minutes) and long-term (600 days) and changes in δ¹³CO₂ and respiration rates measured. Physical and chemical fractionation methods were used to quantify the amount of labile SOM. Pasture soils were characterised by higher labile SOM estimates (HWEC; sand-sized C; labile C respired during long-term incubations) than the other soils. Long-term absence of plant inputs in fallow soils resulted in a significant depletion of labile SOM (close to 50% based on sand-sized C and HWEC estimates) compared with pasture soils. The values of δ¹³CO₂ became more depleted in 13C from fallow to pasture soils (from -26.3 ‰ to -28.1 ‰) and, when standardised (against the isotopic composition of the solid soil material), Δ¹³CO₂ values also showed a decrease from fallow to pasture soils (from -0.3 ‰ to -1.1 ‰). Moreover, these patterns in isotopic measures were in strong agreement with the amount of labile SOM and its availability across the soils, and were best explained by the isotopic values of the labile HWEC fraction. Collectively, these results confirm that labile SOM availability and utilisation change immediately after soil disturbance. Moreover, isotopic analysis of soil-respired CO₂ is a powerful technique, which enables us to probe mechanisms and examine the consequences of soil disturbance on labile SOM by reflecting its availability and the degree of SOM protection.

In der Landnutzung stellt die Bewertung der Versorgung mit organischer Bodensubstanz (OBS) eine besondere Herausforderung dar. Dabei wird der Einfluss der Bodenfeuchte aufgrund des globalen Klimawandels an Bedeutung gewinnen, da die Wasserverfügbarkeit Einfluss auf die Aktivität der bodenlebenden Mikroorganismen nimmt. Ziel der Arbeit waren daher Aussagen, inwieweit verschiedene Wassergehalte den biologischen Umsatz bei der Inkubation von Bodenproben mit unterschiedlicher Herkunft sowie organischer Düngung beeinflussen. In einem Modellversuch wurden Bodenproben ungedüngter Parzellen von drei deutschen Dauerfeldversuchen in einer zweifaktoriellen Blockanlage in Abhängigkeit von organischer Düngung (Weizenstroh, Stallmist) und Wassergehalt inkubiert. Die Experimente wurden in vier Feuchtigkeitsstufen mit 10, 40, 65 und 90 % der Feldkapazität über einen Zeitraum von 85 Tagen bei einer Temperatur von 25 °C realisiert. Zusätzlich sind vor und nach der Inkubation Thermogravimetrische Bodenanalysen (TGBA) durchgeführt worden. Die Ergebnisse belegen einen mit dem Wassergehalt steigenden C-Umsatz, da die Aktivität von aeroben Mikroorganismen bis zur Wassersättigung des Bodens zunimmt. Die Steigerung war bei Zugabe von Weizenstroh höher als bei Stallmist, ohne Düngerzusatz signifikant niedriger. Gleichzeitig änderte sich die Dynamik der Abbauprozesse. Durch besonders trockene Verhältnisse wurde die Umsetzung verzögert, zudem sank die Umsatzrate langsamer. Ein dauerhafter Einfluss des Standorts auf den Umsatz der Düngemittel war dagegen nicht nachweisbar. Der biologische Abbau im Inkubationsversuch veränderte darüber hinaus die thermische Zerfallsdynamik. Die größten Veränderungen wurden nach Zugabe von Stroh festgestellt. Nicht geklärt werden konnte, ob in Böden mit höherer Versorgung durch organische Substanz gleiche Ergebnisse erzielt werden können. / In land use, the assessment of the supply of organic soil matter (OBS) is a particular challenge. The influence of soil moisture on global climate change will become increasingly important, as water availability influences the activity of soil-living microorganisms. The aim of the work is therefore to determine the extent to which different water contents influence the biological turnover during the incubation of soil samples with different origins as well as organic fertilisation. In a model experiment, soil samples from unfertilized plots of three German long-time field experiments were incubated in a two-factor block facility depending on organic fertilization (wheat straw, manure) and water content. The experiments were carried out in four humidity levels with 10, 40, 65 and 90 % of the field capacity over a period of 85 days at a temperature of 25 °C. In addition, thermogravimetric soil analyses (TGBA) were performed before and after incubation. The results prove a C turnover increasing with the water content, since the activity of aerobic microorganisms increases until the water saturation of the soil. The increase was higher with the addition of wheat straw than with manure, without fertilizer significantly lower. At the same time, the dynamics of the degradation processes changed. Due to particularly dry conditions, conversion was delayed and the turnover rate fell more slowly. A lasting influence of the site on fertilizer turnover was not proved. In addition, the biological degradation in the incubation experiment changed the thermal decay dynamics. The largest changes were observed after the addition of straw. It could not be clarified whether the same results could be achieved in soils with a higher supply of organic matter.