Native Cerrado Vegetation Research Articles

Cerrado vegetation types determine how land use impacts ant biodiversity

The simplification of native habitats leads to biodiversity decline in tropical terrestrial ecosystems. We evaluated how conversion of three types of native Cerrado vegetation (open grassland, typical savanna, and woodland savanna) to two human-managed land uses (Eucalyptus plantations and pastures) affects ant richness and composition in arboreal, epigaeic, and hypogaeic ant communities. We also sampled vegetation and soil characteristics to determine which specific features could be driving differences in ant communities with land use conversion. In general, biodiversity was negatively affected by conversion to Eucalyptus plantations and pastures regardless of vegetation type. But these impacts do not act in the same way in each ant strata or vegetation type. Grass and herbaceous cover was the most important environmental variable correlated with diversity in open grassland and plant richness and litter diversity were the most important environmental variables for ant species in typical and woodland savannas. Our results indicate that expanding Eucalyptus plantations may have stronger negative impacts from conversion of open vegetation types while pasture implementation may have stronger negative effects if implemented in closed vegetation types. Thus, we show the need of protection of the diversity of all native vegetation found in the Brazilian Cerrado (from open to forested habitats).

The drivers of sugarcane expansion in Goiás, Brazil

Between 2003 and 2013, sugarcane area expanded six-fold, from 142,000ha to 847,000ha, in Goiás State and the Federal District, Brazil. And while there has been much research on land-use dynamics of sugarcane expansion in established sugarcane growing regions, little is known about the dynamics associated with its expansion in sugarcane frontiers like Goiás. Understanding these dynamics provides critical information for environmental, economic, and political decisions. Here, we investigate the agricultural land-use change dynamics associated with sugarcane production in Goiás and interrogate the relationship between biophysical, institutional, and logistical factors associated with sugarcane expansion. Our results demonstrate that pasture is seven times more likely to be converted to sugarcane than soy, and most new sugarcane area was not sourced in native Cerrado vegetation. Although there exist few biophysical limitations to sugarcane expansion, capital, infrastructure, and institutions constrain production. Lastly, we show that areas where soy is currently cultivated may be converted to sugarcane in the future given the expansion of transportation and sugarcane infrastructure. Thus, we suggest incentivizing the cultivation of sugarcane on degraded pastures and supporting increased pasture stocking rates to ensure continued protection of both natural vegetation and food production while supporting the expansion of sugarcane in the state.

EDAPHIC ATTRIBUTES OF A CROP-LIVESTOCK INTEGRATION SYSTEM IN THE CERRADO BIOME

ABSTRACT A significant increase in the use of integrated farming systems have been observed in the Brazilian Cerrado, such as crop-livestock integration (CLI), which combined with the no-tillage system (NTS) have shown significant influence on soil properties. Therefore, the objective of this work was to evaluate the influence of a CLI system on the chemical, physical and microbiological soil characteristics, in an area in the Cerrado biome, Montividiu, State of Goias, Brazil. The soil fertility, remaining phosphorus (Prem), total organic carbon (TOC), total nitrogen (Nt), aggregate stability (geometric mean diameter - GMD), microbial respiration (C-CO2) and easily-extractable glomalin-related soil protein (EE-GRSP) were evaluated. Soil samples were collected at depth of 0-5 and 5-10 cm in three areas with: CLI (13 years of annual rotation with Urochloa ruziziensis); Urochloa decumbens pasture (15 years of implementation); and native Cerrado vegetation. The CLI area had higher pH, Mg, P available (0-10 cm) and Prem (5-10 cm) values compared to the other areas, and equal values of TOC, Nt, EE-GRSP (0-10 cm) and aggregate stability (5-10 cm) compared to the pasture area. The CLI had no differences in C-CO2 emissions compared to the Cerrado, but had lower rates compared to the pasture. The P available and Prem were sensitive indicators to show the differences between the CLI and pasture systems, with higher contents in the CLI area. The TOC and Nt indicators had no differences between these two systems. The GMD results indicated a better aggregation in the pasture (0-5 cm) compared to the CLI area, while the EE-GRSP were similar in these areas. The total values of C-CO2 emission from the soil aggregates showed the stability of respirometry rates in the CLI and Cerrado areas.

Selecting soil quality indicators for different soil management systems in the Brazilian Cerrado

Abstract The objective of this work was to assess soil quality indicators obtained with different datasets to compare soil management systems in the Brazilian Cerrado. Three criteria were used to select soil physical, chemical, and biological indicators: the full set of indicators obtained, with 36 parameters, for which all the physical, chemical, and biological soil properties were determined; a subset of indicators selected by principal component analysis (20 parameters); and a subset of indicators with some frequency of use in the literature (16 parameters). These indicators were obtained from the following management systems: no-tillage, conventional tillage, and native cerrado vegetation. Soil samples were collected at 0.0-0.1-m soil depth, and soil quality indicators were subjected to analysis of variance and their means were compared. The incorporation of soil native cerrado into agriculture decreased soil quality. The most commonly used indicators in the scientific literature are sensitive enough to detect differences in soil quality according to land use. Therefore, the selection of a minimum set of representative data can be more useful than a complex set of properties to compare management systems as to their soil quality.

English

Intensive soil use without a management plan based on its structures and limitations is the main cause of soil erosion and degradation. The physical properties changes of a studied agricultural area are evaluated by comparing with an area that did not suffer any modification caused by human activities, which is considered the ideal soil condition. This research evaluated the alterations in the hydro-physical properties and the organic carbon content of a Eutrophic Yellow Oxysol under different use and management systems in the Triângulo Mineiro, an important agriculture region in Brazil. The systems studied were, Cerrado with typical stricto sensu vegetation preserved for over 30 years; eucalyptus planted about 30 years ago, without fertilizer or cultivation since the implantation period; corn grown under the no tillage system intercropped with pasture; and Brachiaria sp. under no-tillage intercropped with corn, managed with cattle and annually fertilized with turkey litter. The soil bulk density, total porosity, size distribution of the pores, flocculation degree, geometric mean diameter, water infiltration and organic carbon were evaluated. The effects of land use and management system alterations on soil physical properties were similar at both depths, except the geometric mean diameter, which was higher in the surface layer. The eucalyptus and no-tillage systems with corn and pasture recovered the soil organic carbon contents as compared to the preserved Cerrado area, which was more significant in the surface layer. The soil with native Cerrado vegetation presented faster infiltration in relation to other systems followed by, in descending order, the areas planted with eucalyptus, pasture and corn. The infiltration rate and cumulative infiltration curves were similar to values obtained in the field. Key words: Management systems, no-tillage, soil structure, water infiltration.

Land-use change affects water recycling in Brazil's last agricultural frontier.

Historically, conservation-oriented research and policy in Brazil have focused on Amazon deforestation, but a majority of Brazil's deforestation and agricultural expansion has occurred in the neighboring Cerrado biome, a biodiversity hotspot comprised of dry forests, woodland savannas, and grasslands. Resilience of rainfed agriculture in both biomes likely depends on water recycling in undisturbed Cerrado vegetation; yet little is known about how changes in land-use and land-cover affect regional climate feedbacks in the Cerrado. We used remote sensing techniques to map land-use change across the Cerrado from 2003 to 2013. During this period, cropland agriculture more than doubled in area from 1.2 to 2.5 million ha, with 74% of new croplands sourced from previously intact Cerrado vegetation. We find that these changes have decreased the amount of water recycled to the atmosphere via evapotranspiration (ET) each year. In 2013 alone, cropland areas recycled 14km(3) less(-3%) water than if the land cover had been native Cerrado vegetation. ET from single-cropping systems (e.g., soybeans) is less than from natural vegetation in all years, except in the months of January and February, the height of the growing season. In double-cropping systems (e.g., soybeans followed by corn), ET is similar to or greater than natural vegetation throughout a majority of the wet season (December-May). As intensification and extensification of agricultural production continue in the region, the impacts on the water cycle and opportunities for mitigation warrant consideration. For example, if an environmental goal is to minimize impacts on the water cycle, double cropping (intensification) might be emphasized over extensification to maintain a landscape that behaves more akin to the natural system.

The seasonal carbon and water balances of the Cerrado environment of Brazil: Past, present, and future influences of land cover and land use

The Brazilian savanna (known as Cerrado) is an upland biome made up of various vegetation types from herbaceous to arboreal. In this paper, MODIS remote sensing vegetation greenness from the Enhanced Vegetation Index (EVI) and evapotranspiration (ET) data for the 2000–2012 period were analyzed to understand the differences in the net primary productivity (NPP-proxy), carbon, and the evaporative flux of the major Cerrado natural and anthropic landscapes. The understanding of the carbon and evaporative fluxes of the main natural and anthropic vegetation types is of fundamental importance in studies regarding the impacts of land cover and land use changes in the regional and global climate. The seasonal dynamics of EVI and ET of the main natural and anthropic vegetation types of the Cerrado biome were analyzed using a total of 35 satellite-based samples distributed over representative Cerrado landscapes. Carbon and water fluxes were estimated for different scenarios, such as, a hypothetical unconverted Cerrado, 2002 and 2050 scenarios based on values derived from literature and on the PROBIO land cover and land use map for the Cerrado. The total growing season biomass for 2002 in the Cerrado region was estimated to be 28gigatons of carbon and the evapotranspiration was 1336gigatons of water. The mean estimated growing season evapotranspiration and biomass for 2002 was 576Gt of water and 12Gt of carbon for pasture and croplands compared to 760Gt of water and 15Gt of carbon for the Cerrado natural vegetation. In a modeled future scenario for the year 2050, the ET flux from natural Cerrado vegetation was 394Gt less than in 2002 and 991Gt less than in an unconverted scenario, with only natural vegetation, while the carbon was 8Gt less than in 2002 and 21Gt less than in this hypothetical pre-conversion Cerrado. On the other hand, the sum of the pasture and cropland ET flux increased by 405Gt in 2050 relative to 2002 and the carbon by 11Gt of carbon. Given the increasing global demand for agricultural products and the insufficient protected areas in the Cerrado (with a significant area of remaining native vegetation in privately owned lands that may be legally deforested), our analyses suggest that potential future changes to the water and carbon balances are likely to be highly significant in the severely threatened Cerrado biome. On the other hand, our results also suggest that the recovery of degraded pastures can have a positive impact on climate, due to the higher rates of carbon sequestration and water transfer to the atmosphere.

Carbon Stocks in Compartments of Soil Organic Matter 31 Years after Substitution of Native Cerrado Vegetation by Agroecosystems

Changes in carbon stocks in different compartments of soil organic matter of a clayey Latossolo Vermelho Distrofico (Typic Haplustox), caused by the substitution of native savanna vegetation (cerrado sensu stricto) by agroecosystems, were assessed after 31 years of cultivation. Under native vegetation, a stock of 164.5 Mg ha-1 C was estimated in the 0.00-1.00 m layer. After 31 years of cultivation, these changes in soil C stocks were detected to a depth of 0.60 m. In the case of substitution of cerrado sensu stricto by no-tillage soybean-corn rotation, a reduction of at least 11 % of the soil C pools was observed. However, the adoption of no-tillage as an alternative to tillage with a moldboard plow (conventional system) reduced CO2 emissions by up to 12 %.

Pollen analysis of honey and pollen collected by Apis mellifera linnaeus, 1758 (Hymenoptera, Apidae), in a mixed environment of Eucalyptus plantation and native cerrado in Southeastern Brazil.

Eucalyptus plantations are frequently used for the establishment of bee yards. This study was carried on at Fazenda Brejão, northwestern region of the State of Minas Gerais, Brazil. This farm is covered both with native Cerrado vegetation (Brazilian savanna) and eucalyptus plantations. This paper reports on the botanic origin of pollen pellets and honey collected from honeybee (Apis mellifera) hives along a thirteen-month period (January 2004 to January 2005). The most frequent pollen types found in the pollen pellets during the rainy season were Trema micrantha (Ulmaceae), Copaifera langsdorffii (Fabaceae), an unidentified Poaceae, unidentified Asteraceae-2, Cecropia sp. 1 (Cecropiaceae) and Eucalyptus spp. (Myrtaceae); during the dry season the most frequent pollen types were Acosmium dasycarpum (Fabaceae), Cecropia sp. 1 (Cecropiaceae) and Eucalyptus spp. (Myrtaceae). Pollen grains of Baccharis sp. (Asteraceae), Cecropia sp. 1 (Cecropiaceae), Copaifera langsdorffii (Fabaceae), Mimosa nuda (Fabaceae), Eucalyptus spp. (Myrtaceae) and Trema micrantha (Ulmaceae) were present in the honey samples throughout the study period.

Air-drying and long-term storage effects on β-glucosidase, acid phosphatase and arylsulfatase activities in a tropical Savannah Oxisol

Air-drying soil samples causes a rapid cessation of microbial activity and is a useful means of storing soil samples and standardizing experiments as moisture levels can be accurately controlled. In contrast to temperate soils, there is little information regarding the advantages and disadvantages of using field-moist or air-dried soil samples in the assessment of enzyme activities in tropical soils. The aim of this study was to evaluate the effects of air-drying and a two-year storage period on β-glucosidase, acid phosphatase and arylsulfatase activities in soil samples from cultivated and non-cultivated clayey Oxisols from the Cerrado region. Cultivated soil samples (0–10cm depth) were collected from 24 treatments in three long-term experiments and analyzed to determine their enzyme activities and soil organic carbon (SOC). These treatments presented a large range of extractable Mehlich-P values and cumulative corn and soybean yields. Non-cultivated soil samples from four nearby areas with native Cerrado vegetation were also included in the study. In the laboratory, soil samples were divided into two groups. In the first group, soil samples were separated, stored at 7°C at field moisture levels and sieved through a 4mm sieve. The analyses were performed within 1 week after sampling. In the second group, soil samples were air-dried at room temperature for two weeks, sieved through a 2mm sieve and stored for 2 years at room temperature. Average reductions of 26%, 53% and 72%, were observed in the activities of β-glucosidase, arylsulfatase and acid phosphatase in the air-dried long-term stored samples, in both cultivated and non-cultivated Cerrado clayey Oxisols. Air-drying and long-term storage hardly changed the ranking of treatments for β-glucosidase, arylsulfatase and acid phosphatase. However, a reduction in the capacity to detect changes among treatments was observed for acid phosphatase, which prevents the recommendation of air-drying prior to its analyses. As long as the effects of air-drying upon soil enzymes activities are well established, this pretreatment can be used for β-glucosidase and arylsulfatase analyses in the Cerrado clayey Oxisols.

The Brazilian Cerrado: assessment of water and soil degradation in catchments under intensive agricultural use

AbstractThe Brazilian Cerrado is recognized as one of the most threatened biomes in the world, as the region has experienced a striking change from natural Cerrado vegetation to intense cash crop production. This paper reviews the history of land conversion in the Cerrado and the development of soil properties and water resources under past and ongoing land use. We compared soil and water quality parameters from different land uses considering 80 soil and 18 water studies conducted in different regions across the Cerrado to provide quantitative evidence of soil and water alterations from land use change.Following the conversion of native Cerrado, significant effects on soil pH, bulk density and available P and K for croplands and less‐pronounced effects on pastures were evident. Soil total N did not differ between land uses because most of the sites classified as croplands were nitrogen‐fixing soybeans, which are not artificially fertilized with N. In contrast, water quality studies showed nitrogen enrichment in agricultural catchments, indicating fertilizer impacts and potential susceptibility to eutrophication. Regardless of the land use, P is widely absent because of the high‐fixing capacities of deeply weathered soils and the filtering capacity of riparian vegetation. Pesticides, however, were consistently detected throughout the entire aquatic system. In several case studies, extremely high‐peak concentrations exceeded Brazilian and European Union (EU) water quality limits, which were potentially accompanied by serious health implications. Land use intensification is likely to continue, particularly in regions where less annual rainfall and severe droughts are projected in the northeastern and western Cerrado. Thus, the leaching risk and displacement of agrochemicals are expected to increase, particularly because the current legislation has caused a reduction in riparian vegetation. We conclude that land use intensification is likely to seriously limit the Cerrado's future regarding both agricultural productivity and ecosystem stability. Because only limited data are available, we recommend further field studies to understand the interaction between terrestrial and aquatic systems. This study may serve as a valuable database for integrated modelling to investigate the impact of land use and climate change on soil and water resources and to test and develop mitigation measures for the Cerrado. Copyright © 2014 John Wiley & Sons, Ltd.

New insights on the rarity of the vulnerable Cinereous Warbling-finch (Aves, Emberizidae) based on density, home range, and habitat selection.

The Cinereous Warbling-finch Poospiza cinerea (Emberizidae) is a Neotropical grassland bird considered rare, with population declining due to habitat loss and classified as vulnerable. However, the species conspicuously remains in several degraded areas, suggesting that it may be favored by these environments. Studies which focus on this species were inexistent until 2012, making questionable any statement about its threaten status. Here we analyzed population density, home range, and habitat selection of two groups of P. cinerea at independent sites that differ in human impact levels. Density was estimated by counting and mapping birds. Kernel density and minimum convex polygon were used to estimate home ranges. Habitat selection was inferred from use and availability of every habitat identified within the home range boundaries. One group positively selected urban tree vegetation, despite the availability of natural habitats in its home range. Based on a review on the literature and our findings, we assume that it is unlikely that P. cinerea is rare owing to habitat degradation, as previously thought. Nevertheless, this species was always recorded around native Cerrado vegetation and thus habitat modification may still threaten this species at some level. It is suggested that this species might be a woodland edge species, but future studies are necessary to confirm this assumption.

Cerambycidae Associated with Hybrid Eucalyptus Urograndis and Native Vegetation in Carbonita, Minas Gerais State, Brazil

Wood-borers of exotic and native trees are important pests of eucalyptus in many regions of the world. The feeding behavior of these insects causes losses in wood production. The aim of this study was to identify Cerambycidae beetles inhabiting plantations of clonal hybrid (Eucalyptus grandis × E. urophylla hybrid; Myrtales: Myrtaceae) and native cerrado vegetation in order to improve knowledge about potential wood-borers in these habitats. The insects were collected weekly using baited traps located within eucalyptus stands and in the cerrado vegetation. In total, 3,377 individuals belonging to 13 cerambycid species were caught. The potential wood-borers species in eucalyptus managed plantations should to be monitored during the rainy period.

English

Management and land use is one of the practices that tend to modify the chemical characteristics of the topsoil by tillage and deployment of diverse cultures isolated or consortium. From this perspective, the objective of this study was to evaluate changes in the availability of cations (calcium, aluminum and magnesium) and influence  the potential of zero charge and the point and salt effect null in oxisols under different management systems and use (preserved Cerrado, eucalyptus monoculture, corn under no-tillage and pasture with baquiária grass) in the Triângulo Mineiro region. Noting that the use and soil management changes the electrochemical conditions and a correlation between the availability of calcium and magnesium, with potential of zero charge and the point and salt effect null of the soils, but shows no correlation with the organic matter for the Cerrado soils in use with corn, pasture, eucalyptus and native Cerrado vegetation.   Key words: Nutrients, potential of zero charge, point of zero salt effect, Cerrado.

Formas de carbono em latossolo sob sistemas de plantio direto e integração lavoura-pecuária no cerrado, Goiás

The no-tillage system (NTS) and more recently, the crop-livestock integration (CLI) are very used for grain production in the Cerrado biome. This, the soil organic matter (SOM) is one of the main components responsible for maintaining the quality of tropical soils. This study aimed to quantify the levels of total organic carbon (TOC), total nitrogen (total N), water soluble carbon (WSC) and carbon of humic fractions in areas with different land use systems in the Cerrado of Goias. The farming systems were used: CLI (brachiaria + corn/beans/cotton/soybean) and NTS (sunflower/millet/soybean/corn) andas a reference, area native Cerrado vegetation (Cerradão). We collected soil samples at 0-10, 10- 20, 20-30 and 30-40 cm. The contents of TOC, total N, WSC, humin fraction carbon (C-HUM), humic acid fraction (C-HAF) and fulvic acid fraction (C-FAF). The area of Cerradão had the highest TOC, total N, C-HUM and C-FAH in the surface layer (0-10 cm). The levels of WSC and humic fractions of SOM showed significant differences between the systems of land use and sampling depths. The highest levels of C-HAF were found in the area of CLI, at 0-10 and 20-30 cm. The CLI systems and NTS did not differ for the TOC and total N except for N in layer 20-30 cm. The system CLI favors the formation of C-HUM compared to the NTS. The CLI system leads to lower levels of WSC and higher C-FAF compared with the NTS, which has higher levels of WSC and C-FAH. The use of WSC and carbon of humic fractions was more efficient to identify differences from the land use systems evaluated (NTS, CLI and Cerradão) when compared to the TOC for the climatic conditions of this study.

Teores e estoque de carbono em frações lábeis e recalcitrantes da matéria orgânica do solo sob integração lavoura-pecuária no bioma Cerrado

The study of organic matter and its compartments and their relationship with management, aims to develop strategies for increasing their levels in soils and better understanding of its dynamics. This work aimed to evaluate the fractions of soil organic matter and their carbon stocks in different soil cover system in crop-livestock integration and native Cerrado vegetation. The study was conducted at the farm Cabeceira, Maracajú – MS, sample area have the following history: soybean/corn + brachiaria/cotton/oat + pasture/soybean/formation of pasture/grazing, sampling was carried out in two seasons, dry (May/2009) and rainy (March 2010), in the dry season, crops present were: pasture, corn and cotton + brachiaria and in the rainy season were corn, cotton and soybeans, so the areas in the two evaluation periods were: pasture / maize + brachiaria / cotton, cotton / soybean area and a native of Savanna. Was performed to determine the exchangeable cations, particle size analysis, bulk density, organic carbon, particle size fractionation of organic matter of the soil with the quantification of particulate organic carbon (POC) and organic carbon associated with minerals (OCam). Was also quantified the carbon stock and size fractions. The area of pasture / maize showed higher carbon stock in the particulate fraction in the topsoil. The area of cotton / soy due to its lower clay, showed the greatest loss of carbon. Because of the areas have the same history, the stock of more recalcitrant fraction was not sensitive to variations in coverage. The POC fraction appears more sensitive to different soil covers and seasonality.

Teores e estoque de carbono em frações lábeis e recalcitrantes da matéria orgânica do solo sob integração lavoura-pecuária no bioma Cerrado

The study of organic matter and its compartments and their relationship with management, aims to develop strategies for increasing their levels in soils and better understanding of its dynamics. This work aimed to evaluate the fractions of soil organic matter and their carbon stocks in different soil cover system in crop-livestock integration and native Cerrado vegetation. The study was conducted at the farm Cabeceira, Maracaju – MS, sample area have the following history: soybean/corn + brachiaria/cotton/oat + pasture/soybean/formation of pasture/grazing, sampling was carried out in two seasons, dry (May/2009) and rainy (March 2010), in the dry season, crops present were: pasture, corn and cotton + brachiaria and in the rainy season were corn, cotton and soybeans, so the areas in the two evaluation periods were: pasture / maize + brachiaria / cotton, cotton / soybean area and a native of Savanna. Was performed to determine the exchangeable cations, particle size analysis, bulk density, organic carbon, particle size fractionation of organic matter of the soil with the quantification of particulate organic carbon (POC) and organic carbon associated with minerals (OCam). Was also quantified the carbon stock and size fractions. The area of pasture / maize showed higher carbon stock in the particulate fraction in the topsoil. The area of cotton / soy due to its lower clay, showed the greatest loss of carbon. Because of the areas have the same history, the stock of more recalcitrant fraction was not sensitive to variations in coverage. The POC fraction appears more sensitive to different soil covers and seasonality.

Conservation polices and control of habitat fragmentation in the Brazilian Cerrado biome

The Brazilian Cerrado is the most bio-diverse and threatened savannah on the planet. This biome has already lost 48.2 percent of its original floral cover and is being affected by an intense process of habitat fragmentation. The purpose of this article is to verify if and how governmental and non-governmental conservation measures are protecting the remaining native Cerrado vegetation and whether these measures are encouraging connectivity. Results show that the effects of conservation units are limited, since only 3.1 percent of the biome is within fully protected areas. It was also found that public agencies are much more involved in conservation planning than actions in the field. Conservation projects are often implemented in the same territories, leading to the squandering of resources and ineffective results. Another problem is that many projects are dependent on international organizations and resources. Conservation initiatives in areas under private ownership are rare and economic or fiscal incentives that support such initiatives are sporadic and inadequate. The article concludes by suggesting that the Cerrado should become the focus of specific conservation policies, integrating governments, civil society and economic sectors and actors, especially farmers.

Soil Carbon Stocks under Productive and Degraded Brachiaria Pastures in the Brazilian Cerrado

In the central savannah (Cerrados) region of Brazil approximately 50 Mha are occupied by Brachiaria pastures, most of which are classified as degraded. There are few reliable data on soil C stocks under planted pastures in this region and how soil C has been affected by their establishment and subsequent decline in productivity. This study was performed to compare soil C stocks under native Cerrado vegetation (NV) and productive (PP) and degraded pastures (DP) at four sites (chronosequences). Soil texture, bulk density, and 13C abundance were investigated as candidate indicators for validation of the chronosequences. Productivity of the pastures at each site was evaluated using forage regrowth, existing and deposited litter, and the light fraction of soil organic matter (SOM). At all sites, the soil C stocks were higher under the PP than under the neighboring NV, and stocks under the DP were intermediate or very similar to the stocks under the NV. Soil 13C abundance and C to N ratio suggested that SOM derived from NV was lost at a very low rate except in the surface layers (0–20 cm) and that soil C lost as pastures declined in productivity was principally derived from the pasture grass Brachiaria. The difference between soil C stocks under NV and PP was only 6 to 7 Mg C ha‐1 at two sites with lower clay content (11 and 16%, respectively) but reached 12 Mg C ha‐1 at Site C (46% clay) and 47 Mg C ha‐1 at Site D (67% clay).

Changes in soil C and N distribution assessed by natural δ13C and δ15N abundance in a chronosequence of sugarcane crops managed with pre-harvest burning in a Cerrado area of Goiás, Brazil

Pre-harvest sugarcane straw burning affects the dynamics of soil chemistry and δ13C and δ15N abundance, but further studies are needed to understand the long-term effects of this practice on the degradation of chemical attributes of soil and sugarcane production. The present study evaluates chemical modifications of soil and natural δ13C and δ15N abundance in sugarcane crops managed with pre-harvest straw burning for 1, 5, 10 and 20 years. For comparison purposes, soil covered with natural Cerrado vegetation and forage grass (pasture) were also evaluated. After chemical characterization of the areas studied, according to Embrapa (1997) total organic carbon (TOC), bulk density (Bd) and natural δ15N and δ13C abundance were determined in soil samples, and carbon stocks calculated from TOC values. In general, the pasture area had the highest δ13C and δ15N content, the Cerrado vegetation area had the lowest values for these elements and sugarcane crops exhibited intermediary levels. Areas subjected to sugarcane field burning for a shorter period had the highest Ca and Mg and lowest P and K content. Sugarcane crops managed with straw burning for 1 and 5 years produced lower carbon stocks in the top soil layer (0–10cm) than sugarcane crops with 10 and 20 years, pasture and Cerrado areas. The replacement of natural Cerrado vegetation by sugarcane crops changed δ13C profile, likely because sugarcane is a C4 plant, which has a specific carbon accumulation pattern. Areas cropped with sugarcane for 1, 10 and 20 years and subjected to different types of soil use after replacement of the original Cerrado vegetation had the highest δ15N values, indicating accelerated mineralization of soil organic matter.