Sure can smell the rain


Fly, thought, on golden wings,
go alight on the cliffs, on the hills,
where the sweet airs of our
native soil smell soft and mild!

Chorus of the Hebrew slaves, Nabucco
Giuseppe Verdi

 

Have you ever noticed the smell of rain? Why does wet soil smell so good?

Bottled petricor. Picture by Kevin O-Mara.  Clinc the image to see the original picture at Flickr.
Bottled petrichor. Photo by Kevin O-Mara. Clinc the image to see the original picture at Flickr.

The smell of wet soil plants oils released into the soil during dry periods is due. These substances accumulate in the soil and mix with geosmin, produced and released by several groups of bacteria, including actinobacteria (eg, Streptomyces) and cyanobacteria. Geosmine (from Greek “geo”, earth, and “osmin”, smell) is a bicyclic alcohol derivative of decain, and was firstly described in the 1960s (Gerber and Lechevalier, 1965). When it rains, these chemicals are released into the atmosphere and cause a special smell which is known in English as petrichor (Greek “petros”, stone, and “ikhôr” liquid flowing through the veins of the gods). Continue reading

Soils at Imaggeo: fall into litter


Antonio Jordán
University of Seville, Spain

Click on the image to see the original picture and details at Imaggeo.

Description

Wet forest soil surface after a rainfall simulation experiment in Los Alcornocales Natural Park, southern Spain. When pores are saturated with water, rainfall does not infiltrate, but a dense litter layer may inhibit runoff for some time.

About Imaggeo

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes.

All the material in this database is copyrighted under a Creative Commons Attribution 3.0 licence, which means that Imaggeo content is owned by the individual creators and that they must always be credited when their content is used. People interested in submitting material to Imaggeo can also choose a more restrictive licence, such as Creative Commons Attribution NonCommercial ShareAlike 3.0 licence. For more information please check the Copyright page.

Monday paper: Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain


Doblas-Miranda, E., Rovira, P., Brotons, L., Martínez-Vilalta, J., Retana, J., Pla, M., and Vayreda, J. 2013. Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain. Biogeosciences, 10, 8353-8361. DOI: 10.5194/bg-10-8353-2013.

Abstract

Accurate estimates of C stocks and fluxes of soil organic carbon (SOC) are needed to assess the impact of climate and land use change on soil C uptake and soil C emissions to the atmosphere. Here, we present an assessment of SOC stocks in forests, shrublands and grasslands of peninsular Spain based on field measurements in more than 900 soil profiles. SOC to a depth of 1 m was modelled as a function of vegetation cover, mean annual temperature, total annual precipitation, elevation and the interaction between temperature and elevation, while latitude and longitude were used to model the correlation structure of the errors. The resulting statistical model was used to estimate SOC in the ∼8 million pixels of the Spanish Forest Map (29.3 × 106 ha). We present what we believe is the most reliable estimation of current SOC in forests, shrublands and grasslands of peninsular Spain thus far, based on the use of spatial modelling, the high number of profiles and the validity and refinement of the data layers employed. Mean concentration of SOC was 8.7 kg m−2, ranging from 2.3 kg m−2 in dry Mediterranean areas to 20.4 kg m−2 in wetter northern locations. This value corresponds to a total stock of 2.544 Tg SOC, which is four times the amount of C estimated to be stored in the biomass of Spanish forests. Climate and vegetation cover were the main variables influencing SOC, with important ecological implications for peninsular Spanish ecosystems in the face of global change. The fact that SOC was positively related to annual precipitation and negatively related to mean annual temperature suggests that future climate change predictions of increased temperature and reduced precipitation may strongly reduce the potential of Spanish soils as C sinks. However, this may be mediated by changes in vegetation cover (e.g. by favouring the development of forests associated to higher SOC values) and exacerbated by perturbations such as fire. The estimations presented here provide a baseline to estimate future changes in soil C stocks and to assess their vulnerability to key global change drivers, and should inform future actions aimed at the conservation and management of C stocks.

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Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

Monday paper: Soil organic carbon dynamics of black locust plantations in the middle Loess Plateau area of China


Lu, N., Liski, J., Chang, R. Y., Akujärvi, A., Wu, X., Jin, T. T., Wang, Y. F., Fu, B. J. 2013. Soil organic carbon dynamics of black locust plantations in the middle Loess Plateau area of China. Biogeosciences 10, 7053-7063. DOI: 10.5194/bg-10-7053-2013

Abstract

Soil organic carbon (SOC) is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics are critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation (Robinia pseudoacacia) of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980–2010, where the annual mean precipitation ranging from 450 mm to 600 mm. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr) at all the sites, although it decreased at the wetter sites in the first few years. The accumulation rates of SOC were 1.58 to 6.22% yr−1 in the upper 20 cm and 1.62 to 5.15% yr−1in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation) were the major causes for SOC dynamics and the differences among the sites. They explained 88–96, 48–86 and 57–74% of the variations in annual SOC changes at the soil depths of 0–20, 0–40, and 0–100 cm, respectively. Notably, the simulated SOC decreased during the first few years at all the sites, although the magnitudes of decreases were smaller at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer timescale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites during 1980–2010. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions, species adaptability, and successional stage of recovery.

Download full paper

Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

Monday paper: Changes in soil carbon sequestration in Pinus massoniana forests along an urban-to-rural gradient of southern China


Chen, H., Zhang, W., Gilliam, F., Liu, L., Huang, J., Zhang, T., Wang, W., Mo, J. 2013.  Changes in soil carbon sequestration inPinus massoniana forests along an urban-to-rural gradient of southern China. Biogeosciences 10, 6609-6616. DOI: 10.5194/bg-10-6609-2013

Abstract

Urbanization is accelerating globally, causing a variety of environmental changes such as increases in air temperature, precipitation, atmospheric CO2, and nitrogen (N) deposition. However, the effects of these changes on forest soil carbon (C) sequestration remain largely unclear. Here, we used urban-to-rural environmental gradients in Guangdong Province, southern China, to address the potential effects of these environmental changes on soil C sequestration in Pinus massoniana forests. In contrast to our expectations and earlier observations, soil C content in urban sites was significantly lower than that in suburban and rural sites. Lower soil C pools in urban sites were correlated with a significant decrease in fine root biomass and a potential increase in soil organic C decomposition. Variation of soil C pools was also a function of change in soil C fractions. Heavy fraction C content in urban sites was significantly lower than that in suburban and rural sites. By contrast, light fraction C content did not vary significantly along the urban-to-rural gradient. Our results suggest that urbanization-induced environmental changes may have a negative effect on forest soil C in the studied region.

Download full paper

Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

Monday paper: Mean age of carbon in fine roots from temperate forests and grasslands with different management


E. Solly, I. Schöning, S. Boch, J. Müller, S.A. Socher, S.E. Trumbore, M.  Schrumpf. 2013. Mean age of carbon in fine roots from temperate forests and grasslands with different management. Biogeosciences, 10, 4833-4843, doi:10.5194/bg-10-4833-2013

Abstract

Fine roots are the most dynamic portion of a plant’s root system and a major source of soil organic matter. By altering plant species diversity and composition, soil conditions and nutrient availability, and consequently belowground allocation and dynamics of root carbon (C) inputs, land-use and management changes may influence organic C storage in terrestrial ecosystems. In three German regions, we measured fine root radiocarbon (14C) content to estimate the mean time since C in root tissues was fixed from the atmosphere in 54 grassland and forest plots with different management and soil conditions. Although root biomass was on average greater in grasslands 5.1 ± 0.8 g (mean ± SE, n = 27) than in forests 3.1 ± 0.5 g (n = 27) (p < 0.05), the mean age of C in fine roots in forests averaged 11.3 ± 1.8 yr and was older and more variable compared to grasslands 1.7 ± 0.4 yr (p < 0.001). We further found that management affects the mean age of fine root C in temperate grasslands mediated by changes in plant species diversity and composition. Fine root mean C age is positively correlated with plant diversity (r = 0.65) and with the number of perennial species (r = 0.77). Fine root mean C age in grasslands was also affected by study region with averages of 0.7 ± 0.1 yr (n = 9) on mostly organic soils in northern Germany and of 1.8 ± 0.3 yr (n = 9) and 2.6 ± 0.3 (n = 9) in central and southern Germany (p < 0.05). This was probably due to differences in soil nutrient contents and soil moisture conditions between study regions, which affected plant species diversity and the presence of perennial species. Our results indicate more long-lived roots or internal redistribution of C in perennial species and suggest linkages between fine root C age and management in grasslands. These findings improve our ability to predict and model belowground C fluxes across broader spatial scales.

Download full paper

Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

New book: Fire in agricultural and forestal ecosystem. The effects on soil.


Book cover
Book cover

Giacomo Giovannini
88 pages, 10.00 euros
ISBN 978-884673558-4

What kind of fire can we expect in a specific environment? what outcomes? Although we can not always predict fires, we can scientifically predict their consequences and thus prevent some of them.  This book intends to serve as an overview on the topic and as a guide both in basic ecosystem research dealing with fires and in fire fighting.

This book is written for ecologists, foresters, wildlife and park managers and young scientists who work in the field of forest fire and soil.

The book is intended to serve at least two purposes.

The first purpose is to give an overview of the great and interconnected complexity of the impact of fire on soil. Fire consists of specific components: heat and ash production, which act according to their specific temporal dynamic sequence. Then there is the soil, which behaves as described in traditional soil sciences, but is made even more complex when interacting with fire. Finally, there is the elapse of time and the action of meteorological events such as rain.

Young scientists, in their enthusiastic passion tend, correctly, to study the phenomenon of specific interest in depth, but often neglect the collateral effects. Such effects are discussed in Chapter 1.

Another problem not always well solved by young researchers is the appropriate choice of soil samples for their investigations.

Continue reading