Aluminum Forms in Solid Phase of Soils Developed over Schists as a Function of Land Use

ABSTRACT

Land use may modify certain soil properties while soil physicochemical characteristics can influence metal partitioning in soils. Therefore, the total content and various forms of aluminum (Al) in solid phase of schist-developed topsoils (0–20 cm) in NW Spain under different land uses (i.e., forest, pasture, and cultivation) were evaluated to identify the Al-bearing phases. Aluminum fractionation was performed, using a six-step sequential extraction procedure with ammonium acetate, hydroxylamine hydrochloride, ammonium oxalate in darkness, hydrogen peroxide, ammonium oxalate under ultraviolet radiation, and acid digestion. Mean concentrations of total Al were similar in the soils under three land uses. Mean percentage of the various Al forms in all soils were in the following order: residual fraction > amorphous compounds > crystalline compounds > water-soluble/exchangeable/specifically adsorbed > bound to oxidizable organic matter > manganese oxides. The forest soils contained considerably higher contribution of amorphous compounds (16.3%) to total Al concentration compared with the soils under other two uses (mean about 9%). Maximum mean concentration of exchangeable Al was also observed in forest soils (mean 8.8% of total Al vs. about 4% in pasture soils and cultivated soils); this is attributed to lower pH and higher organic matter content of the forest soils. Thus, this study revealed the impact of land use on the Al-bearing phases and, hence, in its bioavailability to plants.     

Impacts of land use/cover change on soil properties in the Mediterranean region of northwestern Jordan

This study was carried out to evaluate the effects of deforestation on physical and chemical properties of soils under native forest in the Mediterranean region of northwestern Jordan. Land use/cover maps of 1953, 1978 and 2002 were interpreted and analysed within GIS to quantify the shift from forest to rainfed cultivation. Six sites were sampled in a non‐changed forest and in cultivated fields, three for each. Different soil properties of texture, bulk density, organic matter, total nitrogen, pH, cation exchange capacity (CEC), phosphorous and potassium were analysed. Results showed that many forests were changed into cultivated lands at a rate more than the reforestation. Subsequently, adverse effects on the studied physical and chemical properties were observed. The most affected properties were particle size distribution, bulk density of surface soil and subsoil. Organic matter and CEC decreased in cultivated soil as compared to the forest soil. Cultivated soils were found to exhibit a significantly lower status in physical and chemical soil properties as compared to forest soils. This general decline in the soil physical and chemical properties, in turn, contributed to soil erosion, reduction of soil fertility and land degradation. There is an urgent need to improve soil quality by developing sustainable land use practices to reduce the rate of soil degradation and to ensure long‐term sustainability of the farming system in the study area and in similar biophysical settings. Copyright © 2008 John Wiley & Sons, Ltd.     

Soil Structural Stability and Water Retention Characteristics Under Different Land uses of Degraded Lower Himalayas of North‐West India

The lower Himalayan regions of north‐west India experienced a severe land‐use change in the recent past. A study was thus conducted to assess the effect of grassland, forest, agricultural and eroded land uses on soil aggregation, bulk density, pore size distribution and water retention and transmission characteristics. The soil samples were analysed for aggregate stability by shaking under water and water drop stability by using single simulated raindrop technique. The water‐stable aggregates (WSA) >2 mm were highest (17·3 per cent) in the surface layers of grassland, whereas the micro‐aggregates (WSA < 0·25 mm) were highest in eroded soils. The water drop stability followed the similar trend. It decreased with the increase in aggregate size. Being lowest in eroded soils, the soil organic carbon also showed an adverse effect of past land‐use change. The bulk density was highest in eroded lands, being significantly higher for the individual aggregates than that of the bulk soils. The macroporosity (>150 µm) of eroded soils was significantly (p < 0·05) lower than that of grassland and forest soils. The grassland soils retained the highest amount of water. Significant (p < 0·05) effects of land use, soil depth and their interaction were observed in water retention at different soil water suctions. Eroded soils had significantly (p < 0·05) lower water retention than grassland and forest soils. The saturated hydraulic conductivity and maximum water‐holding capacity of eroded soils were sufficiently lower than those of forest and grassland soils. These indicated a degradation of soil physical attributes due to the conversion of natural ecosystems to farming system and increased erosion hazards in the lower Himalayan region of north‐west India. Copyright © 2013 John Wiley & Sons, Ltd.     

Post-reclamation Age Effects on Soil Physical Properties and Microbial Activity Under Forest and Pasture Ecosystems

During surface mining and subsequent reclamation efforts, physical, chemical, and biological properties of soils are disturbed. A study was conducted to evaluate the effects of age chronosequence on soil physical property and microbial activity in chronosequence reclaimed sites covering successional ages in the ranges 1, 4, 8, 11, and 13 years under forest and pasture ecosystems. The adjacent normal and unmined pasture and forest were used as a control for comparison purposes. The study site was located at the Red Hill Mine in east central Mississippi (approximately 33.3 N latitude and 89 W longitude), which is used by the North America Mining Company, LLC. Soil samples were collected from the reclaimed and unmined sites at 0–15- and 15–30-cm depth and analyzed for selected soil quality indicators. Results indicated that water stable aggregate and infiltration were increased, but soil bulk density and compaction decreased with increasing reclamation age. Soil penetration resistance was greater in the pasture than forest ecosystem. All reclaimed soils had less microbial enzyme activity than an unmined forest ecosystem; however, bacteria population level after 11 years since reclamation was similar to that of unmined forest soils. Soil organic carbon increased with increasing reclamation age strongly correlated with soil physical indicators and appears to be the main driving force during the development of soil physical and biological properties in the humid southeast.     

土地利用变化对中国西南热带湿润地区土壤磷动态的影响

Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China’s tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the relationship between soil P dynamics and soil organic carbon (SOC); and c) elucidate the relationship between soil P content and soil properties such as pH and texture. Clearing secondary forests with subsequent shifting cultivation and establishment of rubber tree plantation caused significant decreases (P < 0.05) in available P in 0--20 cm soil depths, whereas for total P there was a significant decrease (P < 0.05) when converting to shifting cultivation, rubber tree plantation, or fallow fields at both 0--20 and 20--40 cm depths. Abandonment of fields used for shifting cultivation led to significant increases (P < 0.05) in available P at 20--40 cm depth. In addition, there was a significant positive relationship between soil organic carbon and soil P content. Compared to secondary forests, the ratio of organic carbon to total P in surface soils (0--20 cm) of shifting cultivation and rubber tree plantation was significantly lower (P < 0.05).     

Land‐use effects on the distribution of soil organic carbon within particle‐size fractions of volcanic soils in the Transmexican Volcanic Belt (Mexico)

The aim of this study was to determine the effect of land‐use and forest cover depletion on the distribution of soil organic carbon (SOC) within particle‐size fractions in a volcanic soil. Emphasis was given to the thermal properties of soils. Six representative sites in Mexico were selected in an area dominated by Andosols: a grassland site, four forested sites with different levels of degradation and an agricultural site. Soils were fractionated using ultrasonic energy until complete dispersion was achieved. The particle‐size fractions were coarse sand, fine sand, silt, clay and particulate organic matter from the coarse sand sized fraction (POM‐CS) and fine sand (POM‐FS). Soil organic carbon decreased by 70% after forest conversion to cropland and long‐term cultivation; forest cover loss resulted in a decrease in SOC of up to 60%. The grassland soil contained 45% more SOC than the cropland one. Soil organic carbon was mainly associated with the silt‐size fraction; the most sensitive fractions to land‐use change and forest cover depletion were POM followed by SOC associated with the silt and clay‐sized fractions. Particulate organic matter can be used as an early indicator of SOC loss. The C lost from the clay and silt‐sized fractions was thermally labile; therefore, the SOC stored in the more degraded forest soils was more recalcitrant (thermally resistant). Only the transformation of forest to agricultural land produced a similar loss of thermally stable C associated with the silt‐sized fraction.     

Effects of Cover Crops on Soil Quality: Selected Chemical and Biological Parameters

Cover crops improve soil quality properties and thus land productivity. We compared soil chemical and biological changes influenced by hairy vetch (Vicia villosa Roth.) and cereal rye (Secale cereal) cover crops grown in Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs), Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualfs), or sand in the greenhouse. Cover crop biomass, soil β-glucosidase, β-glucosaminidase, and fluorescein diacetate (FDA) hydrolase activities, and soil chemical properties were measured at six, nine, and twelve weeks after planting. Cover crop biomass increased with highest (p < 0.0001) yields for hairy vetch and cereal rye in Menfro and Mexico soils, respectively. β-glucosaminidase, FDA, organic carbon (C), total nitrogen (N), and total phosphorus (P) contents significantly decreased in all soils for both cover crops. However, β-glucosidase activity significantly increased (p < 0.0001). Long-term field studies are needed to evaluate soil quality improvement under cover crops, especially for soils with marginal organic matter and fertility.     

The influence of land use and fallow period on the properties of two calcareous soils in the humid tropics of southern Mexico

Calcareous soils are common in the humid tropics of Mexico, but little is known about their productivity and resistance to changes in land use. The influence of land use and duration of fallow on physical and chemical properties were investigated in (a) a loamy Rendzina (at Site A) rich in organic matter and limited in depth by calcareous gravel, and (b) a deeper Calcaric Phaeozem (at Site B) with a more clayey texture throughout. Plots at different successional stages within farmers' shifting cultivation systems were selected on both soils: cropland/young fallow (zero years fallow length), shrub-fallow and tree-fallow at Site A, and cropland/young fallow and forest at Site B. Changes in soil properties suggested a process of recovery with fallow length, in which organic matter, total N and CEC increased with time. The increase in organic matter was remarkably large, on average 0.5–0.6% per year. The Rendzina contained more organic matter than the Calcaric Phaeozem, probably because of its greater carbonate content, which is presumed to protect organic matter against decomposition. The differences in soil properties were mostly greater over time than between treatments.     

Soil enzyme activities in dependence on tree litter and season of a social forest,Burdwan, India

The study was done to evaluate enzyme activities (amylase, cellulase and invertase) from the soils of different vegetation sites, with seasonal variation, of social forest, Burdwan, India. Study results showed significant lower enzymatic activities in the subsoil compared to those of the topsoil. The seasonal variations indicated that amylase, cellulase and invertase enzyme activities had reached peaks during the rainy seasons in different soil depths. Amylase activity was highest in Tectona litter containing soil in all seasons in both the soil layers. All the three enzyme activities have shown significant positive correlation with available nitrogen (p < 0.05) and available phosphorous (p < 0.05) during rainy season in both the soil depths. Correlation study revealed that soil organic carbon was positively correlated with cellulase and invertase activities except in the Anacardium vegetation site in the topsoil during rainy season. Irrespective of the seasons and the depths of soil, control site without vegetation showed much lower levels of organic carbon and enzyme activity compared to those of the experimental sites. Therefore, it is concluded that carbon transformation will be higher during rainy season in the vegetation sites of forest soil under such agroclimatic conditions.     

Indian land use in the Raposa–Serra do Sol Reserve,Roraima, Amazonia,Brazil: Physical and chemical attributes of a soil catena developed from mafic rocks under shifting cultivation

Native Indians (Macuxi, Ingarikó and Uapishana) in the Raposa–Serra do Sol Indian Reserve have been cultivating forest soils since the early XIX century, especially those derived from dolerite sills, scattered within the quartzitic dominated landscape. Representative soils developed from mafic rocks under Indian shifting cultivation in northeastern Roraima, were submitted to physical, chemical and mineralogical analyses to characterize their pedogenetic characteristics and infer on their status under native Indian shifting cultivation. The soil profiles were classified as: Orthic Ebanic Chernosol (USDA Mollisol), vertic Orthic Ebanic Chernosol (USDA Mollisol), Eutrophic Haplic Cambisol (USDA mollic Inceptisol) and Eutrophic Red Nitosol (USDA Red Alfisol), which occupy, respectively, lower slopes and less dissected terrains (Mollisols) and steeper slopes (Alfisols). The first two are eutrophic, and not typical of the Amazon region. Their mineralogies range from kaolinite/goethite rich upland, deeply weathered Nitosol, to 2:1 clay rich downslope Chernosols. The latter has primary minerals in the silt fraction and high CEC resulting in high fertility. The Nitosols reveal a process of severe topsoil loss, due to widespread sheet erosion from deforestation and shifting cultivation. Chemical analyses showed varied soil fertility, ranging from high levels in the Chernosols to a low level in the non-cultivated Nitosol. Phosphorus levels are limited in all soils, despite the high fertility. The Chernosols located in lowland, flat areas close to the valley floor are more suitable environments for the slash-and-burn native farming system. In the Chernosols and Cambisols, the clay activity below the value limit for this class indicates a current natural process of increasing leaching. The more weathered and eroded Nitosol showed low Fe-oxalate and Si-oxalate levels. Micronutrients such as total zinc and copper, decreased with depth and weathering. The Nitosols showed the highest phosphate adsorption levels (1.574 mg g^− 1 of soil) which can be attributed to its clayey texture. Chernosols showed overall lower P adsorption values, increasing with depth. All soils under native Indian cultivation display signs of physical and chemical degradation due to shortened fallow under intense land use pressure in the Raposa–Serra do Sol Reserve.     

Aggregate-associated soil organic carbon and total nitrogen following amendment of puddled and sawah-managed rice soils in southeastern Nigeria

Puddling during sawah rice cultivation destabilizes the soil structure. The re-formation of soil water-stable aggregates (WSA) following puddling and amendments, and their associated organic carbon (SOC) and total N were studied at Akaeze and Ikwo in south-eastern Nigeria. The amendments, which were randomized in triplicate, include control, NPK fertilizer, poultry dropping, rice husk powder and rice husk ashes (RHA). Soil samples from 0 to 15 cm depth were taken from the field after 2 years of cultivation. Most of the SOC were found in the very fine aggregates. There was no consistent trend in the treatment effects. However, the NPK-amended soils showed the lowest values of WSA > 2 mm in both locations, whereas the poultry dropping-amended soils showed the least and the highest mean-weight diameter (MWD) values at Akaeze and Ikwo, respectively. The SOC of the whole soil in Akaeze correlated positively with MWD (r = 0.92*). Irrespective of location, SOC in soils and WSA > 2.00 mm correlated positively with MWD (r = 0.56*; 0.65*, respectively) while SOC in WSA 0.50–0.25 mm accounted for low MWD values. More carbon was sequestered at Akaeze than at Ikwo, with the RHA-amended soils being the highest at both locations.     

SOIL ORGANIC CARBON STOCK AND FRACTIONS IN RELATION TO LAND USE AND SOIL DEPTH IN THE DEGRADED SHIWALIKS HILLS OF LOWER HIMALAYAS

The proportional differences in soil organic carbon (SOC) and its fractions under different land uses are of significance for understanding the process of aggregation and soil carbon sequestration mechanisms. A study was conducted in a mixed vegetation cover watershed with forest, grass, cultivated and eroded lands in the degraded Shiwaliks of the lower Himalayas to assess land‐use effects on profile SOC distribution and storage and to quantify the SOC fractions in water‐stable aggregates (WSA) and bulk soils. The soil samples were collected from eroded, cultivated, forest and grassland soils for the analysis of SOC fractions and aggregate stability. The SOC in eroded surface soils was lower than in less disturbed grassland, cultivated and forest soils. The surface and subsurface soils of grassland and forest lands differentially contributed to the total profile carbon stock. The SOC stock in the 1.05‐m soil profile was highest (83.5 Mg ha⁻¹) under forest and lowest (55.6 Mg ha⁻¹) in eroded lands. The SOC stock in the surface (0–15 cm) soil constituted 6.95, 27.6, 27 and 42.4 per cent of the total stock in the 1.05‐m profile of eroded, cultivated, forest and grassland soils, respectively. The forest soils were found to sequester 22.4 Mg ha⁻¹ more SOC than the cultivated soils as measured in the 1.05‐m soil profiles. The differences in aggregate SOC content among the land uses were more conspicuous in bigger water‐stable macro‐aggregates (WSA > 2 mm) than in water‐stable micro‐aggregates (WSA < 0.25 mm). The SOC in micro‐aggregates (WSA < 0.25 mm) was found to be less vulnerable to changes in land use. The hot water soluble and labile carbon fractions were higher in the bulk soils of grasslands than in the individual aggregates, whereas particulate organic carbon was higher in the aggregates than in bulk soils. Copyright © 2012 John Wiley & Sons, Ltd.     

Soil penetrating quality in cultivated and forested coastal plain sands of Southern Nigeria

Conversion of natural forest to intensive cultivation makes to soil susceptible to flooding, declining fertility and loss of organic matter (OM) and reduced water movement into and within the soil. We studied infiltration rates and related soil penetrating indicators of forested and cultivated soils in humid tropical coastal plain sands in Southern Nigeria. Results showed that mean-weight diameter (MWD) and water stability of aggregates were higher in forested than cultivated soils. Stable aggregates > 1.00 mm were 16.5% and 31.1% respectively, for cultivated and forested soils at 0–15 cm depth, indicating formation of more macro-aggregates in forested soil. Soil disturbance through cultivation decreased hydraulic conductivity and increased bulk density of the soil. Infiltration rate attained after 2 hours was higher in forested soil. Temporary infiltration rate of 178 mm hr^?1 at initial time in cultivated soil was followed by very low infiltration rate of 7 mm hr^?1 after 2 hours. Soil organic matter (SOM), saturated hydraulic conductivity, MWD and total sand correlated positively with infiltration rates are r = 0.76, 0.61, 0.57 and 0.51 respectively. Changes in these parameters are dependent on surface soil disturbance by cultivation. Cultivation of forest decreased infiltration rates and water transmission properties of the soil.     

Ecological study on the dynamics of soil organic matter and its related properties in shifting cultivation systems of Northern Thailand

Abstract

There is a large number of hill people in northern Thailand, who practices shifting cultivation. In order to analyze the soil ecological problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the authors carried out comparative studies on the dynamics of organic matter and its related properties in soils both in the traditional shifting cultivation systems adopted by Karen people and more intensive upland farming practiced by Thai and Hmong people in the area. The contents of organic matter and available N in the surface 10 cm layers of soil from the fields continuously cultivated were lower than those in soils under prolonged fallow (more than 10 y) or natural forest. Based on the rate of soil respiration, the amount of organic matter decomposed within 1 y was estimated to reach nearly 10% of that stored in the upper 50 cm layers of the soil profile in the upland crop fields. These results indicate that the organic matter-related resources markedly decreased under continuous cropping. The contents of C, N, and P in the microbial biomass of the surface 10 cm layers of soil ranged from 0.37 to 2.09 mg C g^?l soil, from 22.7 to 188 µg N g^?l soil, and from 6.1 to 65.7 µg P g^?l soil, respectively. Since the contents of microbial C, N, and P in the surface soils were generally higher under prolonged fallow and natural forests than in the fields continuously cultivated, the microbial activity and/or the amounts of C, N, and P available for biological activity seemed to have declined under continuous upland farming. The incubation experiment to assess the N mineralization pattern showed two remarkable characteristics: 1) there was an initial time lag until active mineralization of N occurred in the soils from young fallow forest and 2) the soil burning effect was observed after burning in the fields under prolonged fallow. The active process of nitrification after N mineralization was always associated with a sharp fall in soil pH, suggesting that soil acidification was promoted and basic cations were lost from the soils. In conclusion, rapid deterioration of the soil organic matter-related properties in cropping fields can be considered to be one of the ecological reasons why upland fields must be returned to fallow again a few years after forest reclamation in traditional shifting cultivation systems. Therefore, in alternative farming systems with more intensive land use, it is essential to apply organic materials into soils to decrease the rate of soil degradation, or to improve the soil fertility, in avoiding soil acidification along with nitrification.     

Effects of charcoal production on soil physical properties in Ghana

Charcoal production, widespread in Ghana like in other W African countries, is a major driver of land‐cover change. Effects of charcoal production on soil physical, including hydrological, properties, were studied in the forest–savannah transition zone of Ghana. Core and composite samples from 12 randomly selected sites across the width of Kotokosu watershed were taken from 0–10 cm layer at charcoal‐site soils and adjacent field soils (control). These were used to determine saturated hydraulic conductivity (K_sat), bulk density, total porosity, soil texture, and color. Infiltration rates, surface albedo, and soil‐surface temperature were also measured on both sites. The results showed that the saturated hydraulic conductivity of soils under charcoal kilns increased significantly (p < 0.01) from 6.1 ± 2.0 cm h^–1 to 11.4 ± 5.0 cm h^–1, resulting to a relative increase of 88%. Soil color became darkened under charcoal kilns with hue, value, and chroma decreasing by 8%, 20%, and 20%, respectively. Bulk density on charcoal‐site soils reduced by 9% compared to adjacent field soils. Total porosity increased from 45.7% on adjacent field soils to 50.6% on earth kilns. Surface albedo reduced by 37% on charcoal‐site soils while soil‐surface temperature increased up to 4°C on average. Higher infiltration rates were measured on charcoal‐site soils, which suggest a possible decrease in overland flow and less erosion on those kiln sites.     

Effect of Land-Use History on Soil Carbon and Nitrogen in a Mediterranean Catchment

The impact of land use on soil organic matter was investigated. Five land cover types (pine forest, olive groves, wheat, wheat/maize cultivation systems, and a shrub pasture) belonging to three land-use categories from the same catchment in the island of Lesvos, Greece, were used. The soils developed under similar pedogenetic processes and accepted similar agricultural practices for at least 30 years. The results showed that the land-use and cover types ranged according to their total soil carbon (C) content as follows: forest > double cultivation > wheat > olive > pasture. Crop plantations contained 31 to 40% less C at their upper 0- to 45-cm layer than forest. Pasture had shallow soils with a small C accumulation but high C concentration, whereas olive groves had the lowest concentrations of both soil C and nitrogen (N). Olive grove soils were the most prone to degradation but possessed the greatest potential for C sequestration.     

The impact of land‐cover change on soil properties in northern Ghana

Effects of changes in land‐cover on soil quality parameters in an area in northern Ghana were studied. Land‐cover changes were derived from maps of the study area for 1984, 1992 and 1999. There were no significant differences between properties of soils under natural vegetation and soils put under cultivation from 1992, but permanently cultivated soils (1984–1999) showed significantly lower physical and chemical soil properties. Soils recently opened up since 1992 for cultivation in the last seven years (i.e. 1992–1999) were found to manifest significantly higher contents of organic C, N, Ca, Mg and ECEC than those under permanent cultivation, suggesting that continuous cropping is responsible for deterioration in soil quality. Minimum organic C contents necessary to meet critical levels of selected soil quality parameters were estimated. The organic C content of recently cultivated soils would need to be increased by about 7 t ha⁻ to replenish soil nutrient capital. This calls for a strategy to synchronize organic matter management with inorganic fertilizer application. Further research is also needed to develop farming systems that conserve organic matter and also improve the quality of organic matter in the study area. Copyright © 2004 John Wiley & Sons, Ltd.     

Changes in Carbon following Forest Soil Transplants along an Altitudinal Gradient

Using a simple case study approach, this research tested the hypothesis that soil organic carbon (C) concentrations would decline when mineral soils from cool, nitrogen (N)–rich, high‐elevation (>1400 m) forests were transplanted to warmer, N‐poor, low‐elevation (～545 m) forests. Two short‐term (<5 year) experiments were performed in the Great Smoky Mountains National Park (Tenn./N.C.) in the southern Appalachian Mountains. In the first experiment, C concentrations in whole soils, particulate organic matter (POM), and mineral‐associated organic matter (MOM) declined significantly (P 0.001) when soils from a high elevation site (1H) were transplanted to a low‐elevation site (1L). In the second experiment, there was a significant (P  0.05) decline in POM C concentrations when high elevation soils (2H) were moved to a lower elevation (2L) as well as declines in whole soil C concentrations that were significant at P  0.10. In both cases, reciprocal transplants of low elevation soils to high elevations resulted in no detectable change in soil C concentrations. Warming of higher quality soil organic matter (whole soil C‐to‐N ratio <20) resulted in greater soil C loss. Consistent with prior predictions, the results suggest that a future warmer and drier climate may cause losses of forest soil C at high elevations in the southern Appalachian Mountains.     

Assessing and monitoring the soil quality of forested and agricultural areas using soil-quality indices and digital soil-mapping in a semi-arid environment

In recent decades, the conversion of forest to agricultural land has been a major worldwide concern and a cause of environmental and soil-quality degradation. In this study, soil-quality indices (SQIs) were applied using several soil properties to determine the effects of land use on soil quality in a 206.50 km² area in Kurdistan Province, Iran. The Weighted Additive Soil Quality Index (SQI_w) was calculated using two scoring methods and two soil indicator selection approaches. Nine soil-quality indicators/variables were measured for 124 soil samples (0–30 cm depth). Calculated SQIs were digitally mapped with a random forest (RF) model using auxiliary data. The RF model was the best predictor of the SQI computed using the total dataset (TDS) and linear score function (SQI_w-TDS-linear). Soil quality was better estimated using non-linear scoring (r² = 0.82) than with linear scoring (r² = 0.73). The mean values of all SQIs were significantly greater in forestland than cropland. It is clear that soil quality is considerably reduced by deforestation, and that best management practices that maintain soil quality and reduce erosion must be developed for the soils of this region if they are to remain productive.     

Changes in Microbial Functional Diversity and Activity in Paddy Soils Irrigated with Industrial Wastewaters in Bandung, West Java Province, Indonesia

Characteristics, such as microbial biomass, basal respiration, and functional diversity of the microbial communities, were investigated in paddy soils located in Bandung, West Java Province, Indonesia, that have been heavily polluted by industrial effluents for 31 years. Paddy soil samples (10?C20 cm) were taken from two sites: polluted soils and unpolluted soils (as control sites). The polluted soils contained higher salinity, higher sodicity, higher nutrient contents, and elevated levels of heavy metals (Cr, Mn, Ni, Cu, and Zn) than unpolluted soils. Soil physicochemical properties, such as maximum water holding capacity, exchangeable sodium percentage, sodium adsorption ratio, and swelling factor, in polluted soils were much greater than those in unpolluted soils (P?<?0.05). Changes in the physical and chemical soil properties were reflected by changes in the microbial communities and their activities. BIOLOG analysis indicated that the functional diversity of the microbial community of polluted soils increased and differed from that of unpolluted soils. Likewise, the average rate of color development (average well color development), microbial biomass (measured as DNA concentration), and the soil CO₂ respiration were higher in polluted soils. These results indicate that major changes in the chemical and physical properties of paddy soils following the application of industrial wastewater effluents have had lasting impacts on the microbial communities of these soils. Thus, the increased activity, biomass, and functional diversity of the microbial communities in polluted soils with elevated salinity, sodicity, and heavy metal contents may be a key factor in enhancing the bioremediation process of these heavily polluted paddy soils.