Evans, C. R. W., Krzic, M., Broersma, K. and Thompson, D. J. 2012. Long-term grazing effects on grassland soil properties in southern British Columbia. Can. J. Soil Sci. 92: 685-693. Although grazing effects on soil properties have been evaluated on various temperate grasslands, no study has dealt with these effects in the southern interior of British Columbia. The objective of this study was to determine the effects of spring versus fall season grazing as well as grazing [at a moderate rate of 0.6 animal unit months (AUM) ha⁻¹] versus non-grazing by beef cattle on selected soil properties. Effects were determined 20 and 30 yr after the establishment of the field experiment. Soil properties were determined for the 0- to 7.5-cm, 7.5- to 15-cm, and 15- to 30-cm depths. In comparison with fall grazing, spring grazing had greater soil bulk density, greater mechanical resistance within the top 15 cm of the soil profile, higher pH, and lower polysaccharides. This was true for both 20 and 30 yr of treatment. Grazing effects on aggregate stability were observed only after 30 yr with spring grazing leading to a more stable structure with a mean weight diameter (MWD) of 1.5 mm and 32% and 10% of aggregates in the 2- to 6-mm and 1- to 2-mm size fractions, respectively, compared with a MWD of 1.0 mm and 20% and 6% under fall grazing. Greater soil bulk density, mechanical resistance, and pH were observed under the grazed treatment relative to the control without grazing, but as we used a moderate stocking rate the impacts were not as great as in previous studies, which used heavy stocking rates. Our findings show that long-term grazing at a moderate stocking rate of 0.6 AUM ha⁻¹ did not have critical detrimental effects on soil properties as some land managers and ranchers have suggested.

Evans, C. R. W., Krzic, M., Broersma, K. and Thompson, D. J. 2012. Long-term grazing effects on grassland soil properties in southern British Columbia. Can. J. Soil Sci. 92: 685–693. Although grazing effects on soil properties have been evaluated on various temperate grasslands, no study has dealt with these effects in the southern interior of British Columbia. The objective of this study was to determine the effects of spring versus fall season grazing as well as grazing [at a moderate rate of 0.6 animal unit months (AUM) ha⁻¹] versus non-grazing by beef cattle on selected soil properties. Effects were determined 20 and 30 yr after the establishment of the field experiment. Soil properties were determined for the 0- to 7.5-cm, 7.5- to 15-cm, and 15- to 30-cm depths. In comparison with fall grazing, spring grazing had greater soil bulk density, greater mechanical resistance within the top 15 cm of the soil profile, higher pH, and lower polysaccharides. This was true for both 20 and 30 yr of treatment. Grazing effects on aggregate stability were observed only after 30 yr with spring grazing leading to a more stable structure with a mean weight diameter (MWD) of 1.5 mm and 32% and 10% of aggregates in the 2- to 6-mm and 1- to 2-mm size fractions, respectively, compared with a MWD of 1.0 mm and 20% and 6% under fall grazing. Greater soil bulk density, mechanical resistance, and pH were observed under the grazed treatment relative to the control without grazing, but as we used a moderate stocking rate the impacts were not as great as in previous studies, which used heavy stocking rates. Our findings show that long-term grazing at a moderate stocking rate of 0.6 AUM ha⁻¹ did not have critical detrimental effects on soil properties as some land managers and ranchers have suggested.

Land degradation causes great changes in the soil biological properties. The process of degradation may decrease soil microbial biomass and consequently decrease soil microbial activity. The study was conducted out during 2009 and 2010 at the four sites of land under native vegetation (NV), moderately degraded land (LDL), highly degraded land (HDL) and land under restoration for four years (RL) to evaluate changes in soil microbial biomass and activity in lands with different degradation levels in comparison with both land under native vegetation and land under restoration in Northeast Brazil. Soil samples were collected at 0–10 cm depth. Soil organic carbon (SOC), soil microbial biomass C (MBC) and N (MBN), soil respiration (SR), and hydrolysis of fluorescein diacetate (FDA) and dehydrogenase (DHA) activities were analyzed. After two years of evaluation, soil MBC, MBN, FDA and DHA had higher values in the NV, followed by the RL. The decreases of soil microbial biomass and enzyme activities in the degraded lands were approximately 8–10 times as large as those found in the NV. However, after land restoration, the MBC and MBN increased approximately 5-fold and 2-fold, respectively, compared with the HDL. The results showed that land degradation produced a strong decrease in soil microbial biomass. However, land restoration may promote short- and long-term increases in soil microbial biomass.

Phytoremediation technologies generate huge quantities of biomass, the disposal of which is a serious concern. Wastewater samples collected from electroplating industries were treated with Salvinia biomass. The effect of application of metal loaded Salvinia plant biomass in soil on growth and physiological indices of 10-day-old seedlings of Triticum aestivum was evaluated. Controls (A) consisted of soil supplemented with untreated plant biomass. Seed germination, seedling height, total chlorophyll, glucose and protein levels, photosynthetic efficiency (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (qn), quantum yield (Y), and electron transport rate (ETR) were not significantly affected in seedlings raised in soils supplemented with metal loaded biomass from most of the samples (B–F) in comparison to control. However, significant decline was noted in total chlorophyll, glucose, and quantum yield in plants grown in soil supplemented with biomass from sample E. Among elemental levels, C(%) remained largely unaffected, N(%) showed slight enhancement but a decrease in H(%) was noted in plants grown in soil supplemented with biomass from sample E. Our results, therefore, suggest that metal accumulated Salvinia biomass obtained after phytoremediation of heavy metal contaminated wastewater can be supplemented in soil. Further studies are required to assess long-term effects of disposal of metal loaded Salvinia plant biomass in soil.

Biological property is a best indicator for soil quality identification due to its relationships with soil nutrient cycle, respiration, microbial biomass and enzymes activity. The aim of the research was to study the influence of two even-aged and adjacent stands of loblolly pine (Alnus glutinosa L. (Gaertn.) and alder (Pinus taeda L.) on activity of dehydrogenase and urease enzymes, microbial biomass and some of the soil chemical and physical properties at west of Guilan province. Soil sampling was made up to 20 cm depth of soil surface (0-10 and 10-20cm). Dehydrogenase and urease enzymes activities and microbial biomass were measured, using the substrate reaction method and application of spectrophotometer device. The tested soil properties consisted of: texture, bulk density, mean particle density, moisture content, pH, organic carbon, total nitrogen, phosphorus and potassium. The results showed that there were significant differences between the two stands in respect to amounts of dehydrogenase and urease enzymes, microbial biomass, carbon, nitrogen and potassium. The amount of urease and dehydrogenase enzymes, microbial biomass, organic carbon and nitrogen in alder stand was more than in the loblooly Pine stand. There were significant correlations between the enzymes density and microbial biomass, organic carbon, nitrogen, pH, potassium, soil texture and soil porosity. Overall, it might be concluded that the alder stand provided better condition for organic matter and microbial production and microbial biomass development and activity.

The effects of fire on labile soil C and N in forest ecosystems are important for understanding C sequestration and N cycling not only because labile soil C and N are often variables that determine soil fertility but also because the role of soils as a source or sink for C is important on an ecosystem and on the regional level. In the current study, the literature on the effects of fire on soil organic C, total N, microbial biomass C and N, dissolved organic C, and total N, respiration, and N mineralization in mineral soil was reviewed, and the results of a meta-analysis on literature data were reported. Overall, fire significantly increased the soil total N, microbial biomass N, dissolved organic C, and total N, but decreased soil organic C, microbial biomass C, respiration and N mineralization. Among the significant effects of different fire types, wildfire had the higher effects on the soil organic C, total N, microbial biomass C and N, dissolved total N and respiration of soil than prescribed fire. In addition, responses of soil organic C, total N and N mineralization to wildfire depended on forest type and natural zone. Positive responses of soil organic C, total N were found in broadleaved forests and Mediterranean zones, and negative responses in coniferous forests and temperate zones. Wildfire significantly decreased N mineralization in coniferous forests. The effects of fire on soil microbial biomass C and N, dissolved organic C and N mineralization generally decreased with time after the fire. In general, the effects of fire on soil organic C, microbial biomass C, and dissolved total N and N mineralization decreased with increasing soil depth. These results suggest that fire increases C and N availability and increases microbial activity, which consequently decreases the potential rates of C sequestration.

This experiment was conducted to select winter-adaptable crop system or cropping systems for an enhanced carbon (C) fixation amount in plant biomass and soil. Single or mixed cropping systems of green manure crops, rye (R), triticale (TC), hairy vetch (HV), TC+HV, and control (fallow) were investigated during winter and spring. The amount and content of C and N in the above-ground biomass and soil C content by soil depth were measured under different green manure crops. The above-ground biomass was highest in TC+HV followed by R and TC with 664, 585, and 545 kg 10a-¹, which exceeded the biomass of control by 181, 160, and 149%, respectively. The amount of C accumulation was higher in soil surface than deep soil. which was a similar pattern to the above-ground biomass. Therefore, green manure cropping in winter and spring seasons will be very helpful of improve soil organic matter.

Tillage strongly affects the process of soil aggregate stabilization, which involves a variety of binding mechanisms interacting at a range of spatial scales. To understand how binding mechanisms interact to promote soil aggregation, the impacts of three tillage systems (no tillage (NT), ridge tillage (RT) and conventional tillage (CT)) on soil aggregate binding agents (i.e., organic carbon (SOC), microbial biomass and glomalin-related soil proteins (GRSPs)) and aggregation were studied in the black soil of Northeast China. Compared with CT, RT increased all the aggregate-associated SOC, and NT only increased the SOC in the microaggregates. However, the contents of microbial biomass and GRSPs within bulk soil and different aggregate fractions were higher in NT and RT than in CT. Among the four aggregate fractions, greater values of SOC, microbial biomass and easily extractable GRSP (EEGRSP) were found in microaggregates and macroaggregates, respectively; while the total GRSP (TGRSP) was distributed equally among aggregate fractions. Structural equation modelling revealed that SOC, microbial biomass, and GRSPs accounted for 79% of the variation in soil aggregation. Soil organic carbon influenced aggregate stability indirectly through the effects on MBC and MBN. Microbial biomass and glomalin were more important driving factors for aggregate stability in the RT and NT systems. Our results suggest that conservation tillage (RT and NT) is beneficial for soil structure due to its positive effects on aggregation processes in black soil region of Northeast China.