J.E. Celis, M. Sandoval, B. Martínez, and C. Quezada. 2013. Effect of organic and mineral amendments upon soil respiration and microbial biomass in a saline-sodic soil. Cien. Inv. Agr. 40(3): 571-580. An understanding of soil carbon stocks and fluxes in saline-sodic soils is becoming critical in environmental management because salinity and sodicity are predicted to increase worldwide. The effects of amendment with sewage sludge (SW), mined gypsum (MG) and synthetic gypsum (SG) on the soil respiration rate and soil (S) microbial biomass (SMB) of a saline-sodic soil were assessed in vitro over 60 days under controlled conditions. The treatments were: T1 = S + MG (7 t ha -1 ); T2 = S + MG (7 t ha -1 ) + SW (90 t ha -1 ); T3 =
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In the present work, soil respiration varied greatly throughout the year, mainly influenced by soil temperature. Soil water content did not significantly influence the response of soil respiration as it was constant during the measurement period and under no water stress conditions. Distance between nearest walnut and measurement was also a highly influential factor in soil respiration. Generally there was a decreasing trend in soil respiration when the distance to the nearest tree increased. It was also analyzed the response of soil respiration according to alder presence and fertilizer management (50 kg N·ha -1 ·año -1 from 1999 to 2010). None of these treatments significantly influenced soil respiration, although previous studies noticed an inhibition in rates of soil respiration under fertilized conditions and high rates of available nitrogen. However, treatments without fertilization and without alder presence obtained higher respiration rates in those cases with significant differences. The lack of significant differences between treatments may be due to the high coefficient of variation experienced by soil respiration measurements. Finally an asynchronous fluctuation was observed between soil respiration and litterfall during senescence period. This is possibly due to the slowdown in the emission of exudates by roots during senescence period, which are largely related to microbial activity.
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The Oxitop® device consists of a measuring vessel and a lid for locking it, an Oxitop® – C measuring sensor (measuring head) an Oxitop® OC110 controller. The moisture (soil) is placed in the bottom of the vessel, and a plastic cup with the absorption agent (NaOH) is placed in the holder plate. As the process follows, the measuring head reads the pressure every certain period of time, and the data can be collected with the controller. After finishing the experiment, it is possible to transfer all the measurements to the computer via ACHAT OC PC software, and then to Excel. After finishing the experiment and collecting all data, soil respiration can be calculated as:
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The soils in the Rivas area largely belong to the Rivas complex and were formed on marine parent material of young Tertiary age. The parent materials consist of clays and sands of varying thickness. The Rivas complex has been lightly folded and eroded, resulting in a landscape with rolling to steep hills. Ephemeral rivers (gullies) are deeply incised and bordered by fluvial deposits that range from clay higher up in the deposit to gravel at the bottom. Alluvial fans with slopes of less than 10% have been formed as a result of erosion in the hills. These areas are largely heavy-textured and range from clay loam on the fringes of valleys to heavy clay in the central areas. The clays are largely montmorillonitic, causing the formation of Vertisols which swell upon wetting and form deep cracks upon drying. These soils become very hard when dry. In some areas the soils may have horizons with lime concretions (<1 cm diameter) between 50 and 100 cm depth, because the parent material has some calcium carbonate. Steeper slopes have highly variable soils and on slopes where soil movement is evident they range between 0 and 50 cm in depth. Loamy to clayey soils are found on more gradual, less steep slopes, frequently with a well-developed dark topsoil. The mineralogy of these soils is the same as in the alluvial fans, but the Vertisol character is less expressed, with lower clay contents (Buurman and Hoosbeek 2009).
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to a two-way analysis of variance (ANOVA) at each sampling date. The differences were validated using the Tukey’s honestly significant differences (HSD) test and were considered statistically significant at p≤0.05 for all pairwise comparisons (Steel and Torrie, 1980). On a seasonal basis, correlation coefficients between morning and afternoon soil respiration rates and environmental variables (soil temperature, soil water content, absolute maximum air temperature, maximum mean air temperature, monthly mean air temperature, minimum mean air temperature, absolute minimum air temperature and monthly precipitation) at each land use were quantified by the Spearman’s rank order correlation analyses since the null hypothesis of normality was rejected at p<0.05 (Steel and Torrie, 1980; Ott, 1993). Linear regression analyses were performed between soil respiration rate and morning and afternoon soil temperature at each land use. All statistical methods were applied according to the SPSS (Statistical Package for the Social Sciences) software package (standard released version 9.0 for Windows, SPSS Inc., Chicago, IL).
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de Oaxaca: una comparación de sitios húmedos y secos. Tesis de Maestría. Instituto de Ecología, Universidad Nacional Autónoma de México. México, D.F., México. 73 p. Alef, K. 1995. Soil respiration. In: Alef, K. and P. Nannipieri (eds.). Methods in applied soil microbiology and biochemistry. Academic Press Inc. San Diego, CA, USA. pp. 214-215. Almeida-Leñero, L., M. Nava, A. Ramos, M. Espinosa, M. J. Ordóñez y J. Jujnovsky. 2007. Servicios ecosistémicos en la cuenca del río Magdalena, Distrito Federal, México. Gaceta Ecológica 84-85: 53–64.
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In fact, in a previous work, a chronosequence of grassland from 3 to 56 years of age, was evaluated. Their results indicated that 15 year old grasslands had a higher amount of C and N due to the age, the grassland system accumulated more SOM, coming specifically from plant and root organic wastes, which generated a higher SOC contribution and other nutrient uptake. After that age, there was a decrease in the release of chemical elements in such systems (Cheng & Shao (2015); Jie, Cheng, Li & Liu (2012); Tadakatsu, Ohkura & Matsumoto (2015)). Alternatively, Huang et al. (2010), mentioned that over the years, grasslands lose their vocation to accumulate SOC due to a decrease in the system productivity, mainly due to an increasing degradation of its properties, motivated by cattle overgrazing and the type of grassland established. Accordingly to Goodrick et al. (2015), some tropical agroforestry systems slowly reduce the SOC content due to the higher N contents that legumes procure (which speeds up the mineralization processes). In addition, a higher STN concentration and higher mineralization, reduces the C/N ratio, resulting in a greater SOM decomposition. Other research has documented that under certain conditions, by switching from crop to grassland, an increase in SOC levels, which can be achieved by 26% (Don et al., 2011). On the other hand, Johnson et al. (2007), conducted a study in which they revealed the SOC amount, which can be stored in the soil as a function of the organic wastes amount produced and entering into the soil, for instance, soil composition and soil decomposition rate, noting that roots of the grasses decomposition have allowed a great amount of recalcitrant compounds.
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being more systematic over Scandinavia and Northern Russia. Fig. 5 (top right) shows the corresponding bias for the ELD experiment. The bias is also well controlled, with a predominance of colder biased regions. However, biased regions do not exactly match in both experiments. ELD shows a clear trend to cold bias over France and Eastern Europe, which is not so notorious in the REF experiment. On the other hand, the REF cold bias over Northern Europe is not present in the ELD experiment. A possible explanation of the Nordic bias in REF could reside on the masking conditions prescribing when screen variables are coupled or not to soil moisture. These “summer- like” conditions frequently show a latitudinal dependence, reducing the number of active cycles for soil moisture corrections as latitude increases (see Navascues et al. 2003).
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Among the problems of physical degradation, compaction and densification are the main ones, and they cause strong decreases in subsequent crop yields thereof. The degradation of soil structure is a worldwide problem that can occur in all soils and livestock production levels. Given the above, this paper aims to analyze the main changes in the internal structure of the soil as a result of compaction by trampling of animals. Soil compaction due to the collapse or decrease in pore spaces, is the most common cause of physical restraint to growth and root development. As an aggravating factor, degradation of soil structure is regarded as the type of land degradation more difficult to locate and retrain; the reason is that this degradation is a subsurface phenomenon. Finally it is to establish some possible solutions to this problem, including the main method of restoring the porosity of the boundary layers of root growth is to apply biological methods as used, for example, the roots of natural vegetation or crops coverage, planted to act as biological subsoilers that penetrate dense horizons.
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Variations in soil organic matter content depend on the equilibrium between the amount of organic matter provided and its mineralization rate. In this study, organic matter contribution was the highest in CT and the lowest in HT. On the other hand, biomass management generated by each treatment also had effects over the soil organic matter content. Likewise, by incorporating the biomass generated for adventitious plants in the TT scenario, the soil organic matter is preserved at similar level to AGT treatment. The aerial biomass generated by AGT was six times greater than that generated by TT (Table 6). However, since this treatment did not involve tillage, mainly the underground part of the cover crop (approximately 25% of the aerial part) was truly incorporated into the soil (Fig. 2) while in TT all the biomass generated by the adventitious plants was incorporated into the soil. This way, the real amount of biomass incorporated into the soil was very similar in both treatments.
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suggested that the CTM2 pore structure contained a great amount of small features as the number of small voids (i.e., connected components) surpasses the number of soil materials that tunneled through them; therefore, high val- ues of the specic mean curvature from these small features of the CTM2 pore space should be explained by the regularity of the surface that enclosed them. Let us recall that convex objects have positive mean curvature. It will be neg- ative when concave parts dominate over convex ones on the boundary surface of a three-dimensional object. Sample CTM1 followed the same trend at the lowest porosity, but in this case it was less pronounced. Therefore, at low porosities smaller than 10%, samples from tillage displayed a great amount of small and regular features as compared with samples from resident vegetation cover. When the volume fraction or porosity went beyond 10%, resident veg- etation cover displayed a distinct pattern characterized by a highly connected structure as a consequence of the high values of specic surface, mean cur- vature close to zero, and negative low values of specic connectivity. These results suggest that evolution of morphological features with dilation and ero- sion is more informative as an indicator of structure than moving threshold for cultivated soil in a Mediterranean vineyard.
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and weeds (De Cal et al., 2005; Schneider et al., 2008; García-Méndez et al., 2009). Although the integrated pest management has increased and the use of plant protection products has decreased in the last years (EUROSTAT, 2015; Zanón et al., 2014), the intensive production continues being an environmental concern in the strawberry production areas. Since the phase out of methyl bromide, producing strawberries has become increasingly challenging. Various alternatives to methyl bromide soil disinfection less aggressive to the environment have been used (Mao et al., 2012); The use of 1,3- dichloropropene (1,3-D) and chloropicrin (Pic) has increased in strawberry cropping systems in the last years, becoming essential to maintain strawberry commercial production in southern Spain (Porter et al., 2006; López-Aranda et al., 2009b). However, these fumigants present uncertain effects on the environment (Yates et al., 2011) and in 2011 their use were not approved in the European Union (E.C., 2011a, 2011d). Currently, their use in Spain is limited to some exceptional situations for periods shorter than 120 days according to the article 53 of the Regulation (EC) No. 1107/2009, which accepts exceptional uses when phytophatological danger cannot be contained by any other reasonable mean (E.C., 2009). The use of other soil fumigants as dazomet, metam-sodium and metam-potassium is permitted in the EU (E.C., 2011b) and have demonstrated their efficacy as alternatives to methyl bromide in strawberry crops (López-Aranda et al., 2009a; López-Aranda et al., 2009b; Pizano et al., 2010). The use of other substances with nematicide, fungicide and insecticide effects as Bacillus firmus I-1582, etoprophos, fenamiphos, fosthiazate, iprodione, oxamil and Paecilomyces lilacinus strain 251 is also possible (E.C., 2011b).
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In recent decades, afforestation of mountain grasslands has occurred on a global scale (Jackson et al. 2002; Berthrong et al. 2009). This is particularly the case in Spanish (Poyatos et al. 2003; Camarero and Gutiérrez 2004) and Austrian mountain regions (Dullinger et al. 2004; Tasser et al. 2007), following the intensification of livestock production and economic constraints which have driven smallholders’ farmers in mountainous regions out of business, together with the afforestation programmes promoted by European governments. The growing body of information on the effect of forest expansion on SOM has produced contrasting and highly site-dependent results (Guo and Gifford 2002). The aim of this work is to determine common patterns caused by afforestation of grasslands on SOM features in two European mountainous areas with contrasting climates (Mediterranean and temperate). We sampled soil from 17 paired sites, all containing grassland and afforested plots. We determined bulk C and N concentrations and their stable isotope composition from soil and vegetation, and estimated SOC decomposition rates under standardised conditions in the laboratory for six months. We hypothesised that afforestation leads to changes (1) in SOC and total N concentrations, (2) in SOC mineralisation rates, and (3) in the signatures of soil 13 C and
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Natural as well as managed traditional tropical ecosystems are composed of combina- tions of plant life forms that have the potential to be more productive and more thorough in the use of resources than most monocultures (Haggar and Ewel 1995, 1997). It has been hypothesized that full use of resources on a site having high potential productivity could be achieved by the use of highly productive mon- ocultures or the combination of productive spe- cies that complement one another in their use of resources (Haggar and Ewel 1997). Greater productivity of plant associations seems to be due to the combination of trees with spe- cies that occupy other layers of the canopy and soil. Examples of this are combinations of trees with understory plants and perennial monocots. Trees allocate a high proportion of their biomass to supporting structures, while many perennial monocots show high alloca- tion to structures such as leaves and fine roots (Haggar and Ewel 1997). These species may be complementary in the use of key resources and be successfully used to construct sustainable land use systems.
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The Mt. Bawakaraeng Caldera is located in the province of South Sulawesi, Indonesia (Figure 1), at 2 830 masl. The morphology of Mt. Bawakaraeng is characterized by a high relief, extreme slopes, high degree of weathering, as well as events related to erosion such as soil movement and landslides (Hasnawir and Kubota, 2010). The vegetation of the mountainous areas is composed of natural forest and forest plantations of Pinus merkusii Jungh. & de Vriese. The basement around the area of Mt. Bawakaraeng, consists of Tonasa formation, Camba formation, Baturape-Cindako volcanic rocks, extrusive and intrusive rocks and Lompobattang volcanic formations, whose origin dates from the Paleogene to the Quaternary period.
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The seeds planted in the vermiculite (b, d) did not germinate, while those in untreated soil (a, c) germinated readily. Temperature, humidity and light could not have affected the results, because all four dishes were irrigated with the same amount of sterile distilled water and placed in the same incubator (28 C) in the dark. From these results, I concluded that sorne factor in the soil was probably indispensable for the germination of Urostigma seeds.
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distribution of samples by the ranges of IE where the majority of soil are found (Table 1). When the IE is computed with the standard triplet a great amount of soils have low IE value (have unbalanced contents respect to those texture fractions). This is may be an obstacle for reconstruction of the PSD under the entropy self-similarity. In particular, because of the meaning of self-similarity itself, if the input contents are very unbalanced, it cause a multiplicative effect of more unbalanced distribution in the “sub-fractions” at lower scales and probably a more unreliable simulation. On the contrary, in the case of the modified 30
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In conclusion, the benthic primary producers of the Surá stream are, under closed canopy, light limited and are not limited by macronutnents in open canopy siles. Because the La Selva forest has a very high disturbance rate in the forro of new forest gaps (Sanford, Braker & Hartshorn 1986), open areas along forested streams may be a frequent evento Hence, the growth of primary producers in tropical headwaters is possibly more common than is currently thought. Compared to other tropical periphyton studies, the Sufá acquires similar biomass levels at similar colonization times. Productivity and respiration rates, however, are lower than other tropical sites. Micronutnent limitation may exist, but could not be demonstrated in our study.
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Agriculture significantly contributes to global greenhouse gas (GHG) emissions and there is a need to develop effective mitigation strategies. The efficacy of methods to reduce GHG fluxes from agricultural soils can be affected by a range of interacting management and environmental factors. Uniquely, we used the Taguchi experimental design methodology to rank the relative importance of six factors known to affect the emission of GHG from soil: nitrate (N0 3 ~) addition, carbón quality (labile and non-labile C), soil temperature, water-filled
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According to the variance analysis, differences (P≤0.05) were found in the soil respiration, temperature and soil moisture for the land use factor (UF); there were no differences in soil moisture for the sampling time factor (TF), and no significant differences were found in any of the studied variables for the UF*TF interaction (Table 2). The Sr is highest in the morning samplings carried out in the thornscrub (6.17 µ mol CO 2 m -2 s -1 ) and differs from that of the other land
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