ABSTRACT
Anthropic activities in their various aspects have promoted soil degradation in the Brazilian semi-arid region (SAB). As a result, significant losses in productivity and in the ability of soils to fulfill their ecological functions have been reported. The present study investigated the effects of degradation on soil attributes and properties under dense (CAD) and sparse (CAE) shrubby Caatinga in Campina Grande, PB, Brazil. Samples from the 0-20 cm layer of soil were investigated via physical (particle size distribution and soil density), chemical (acidity, electrical conductivity, macronutrients, soil organic matter) and microbiological attributes (microbial biomass carbon (C-BMS), basal respiration of the soil (RBS) and metabolic quotient (qCO2) Data were submitted to the Mann-Whitney Test and Principal Component Analysis (PCA). Anthropic actions on the CAE promoted the exposure of the saprolitic layer on the surface. This layer has imperfect drainage, low levels of nutrients and organic matter and high sodicity, which contributes to the slow regeneration of vegetation. Carbon stock and microbial activity are significantly lower in CAE compared to CAD. Degradation resulted in losses of supporting ecosystem services (nutrient cycling and primary production) and regulation (erosion control and climate regulation). The results can be used to understand the dynamics of landscapes of low complexity (high degradation) in the SAB and serve as a framework to find strategies to restore the productive capacity of extensive degraded and/or desertified areas in the SAB.
Keywords:
Ecosystem Services; Desertification; Carbon Stock
RESUMO
As atividades antrópicas em seus diversos aspectos têm promovido a degradação dos solos no Semiárido brasileiro (SAB). Como consequência, têm sido reportadas perdas significativas de produtividade e da capacidade dos solos em cumprir suas funções ecológicas. O objetivo desta pesquisa foi avaliar os efeitos da degradação nos atributos e propriedades de solos sob Caatinga arbustiva densa (CAD) e esparsa (CAE) em Campina Grande, PB, Brasil. Amostras da camada de 0-20 cm do solo foram analisadas quanto aos atributos físicos (granulometria e densidade do solo), químicos (acidez, condutividade elétrica, macronutrientes, matéria orgânica) e microbiológicos (carbono da biomassa microbiana (C-BMS), respiração basal do solo (RBS) e quociente metabólico (qCO2). Os dados foram submetidos ao Teste de Mann-Whittney e à Análise de Componentes Principais (ACP). As ações antrópicas na CAE promoveram a exposição da camada saprolítica em superfície. Esta camada possui drenagem imperfeita, baixos teores de nutrientes e de matéria orgânica e elevada sodicidade, o que contribui para a lenta regeneração da vegetação. O estoque de carbono e a atividade microbiana são significativamente mais baixos na CAE em relação à CAD. A degradação acarretou em perdas de serviços ecossistêmicos de suporte (ciclagem de nutrientes e produção primária) e de regulação (controle da erosão e regulação do clima). Os resultados podem ser utilizados para compreensão da dinâmica de paisagens de baixa complexidade (elevada degradação) no SAB, bem como para adoção de estratégias de restabelecimento da capacidade produtiva de extensas áreas degradadas e/ou desertificadas no SAB.
Palavras-Chave:
Serviços ecossistêmicos; Desertificação; Estoque de carbono
1. INTRODUCTION
The Brazilian Semi-arid (SAB), a region with 1,182,697 km2 (Sudene, 2017Superintendência de Desenvolvimento do Nordeste - SUDENE. Delimitação do semiárido. 2017 [cited 2022 apr 07]. Available from: http://antigo.sudene.gov.br/delimitacao-do-semi-arido
http://antigo.sudene.gov.br/delimitacao-...
), represents almost 14% of the national territory and 76% of the Northeast region. It is a region traditionally subject to droughts, where erosive processes have been intensified due to extensive livestock farming, rudimentary agriculture, and vegetal extractivism (CGEE, 2016Centro de Gestão e Estudos Estratégicos - CGEE. Desertificação, degradação da terra e secas no Brasil. 2016 [cited 2022 apr 07]. Available from: https://www.cgee.org.br/documents/10195/734063/DesertificacaoWeb.pdf
https://www.cgee.org.br/documents/10195/...
).
Studies evaluating the effects of land use change on C (carbon) and N (nitrogen) dynamics (Althoff et al., 2018Althoff TD, Menezes RSC, Pinto AS, Pareyn FGC, Carvalho AL, Martins JCR, et al. Adaptation of the century model to simulate C and N dynamics of Caatinga dry forest before and after deforestation. Agriculture, Ecosystems Environment. 2018; 254(May 2017): 26-34. doi: doi.org/10.1016/j.agee.2017.11.016
https://doi.org/10.1016/j.agee.2017.11.0...
), energy and water flows (Silva et al., 2017Silva PF, Lima JRS, Antonino ACD, Souza R, Souza ES, Silva JRI, et al. Seasonal patterns of carbon dioxide, water and energy fluxes over the Caatinga and grassland in the semi-arid region of Brazil. Journal of Arid Environment. 2017; 147: 71–82. doi: https://doi.org/doi:10.1016/j.jaridenv.2017.09.003
https://doi.org/doi:10.1016/j.jaridenv.2...
), nutrient cycling (Moura et al., 2016Moura PM, Althoff TD, Oliveira RA, Souto JS, Souto PC, Menezes RSC, et al. Carbon and nutrient fluxes through litterfall at four succession stages of Caatinga dry forest in Northeastern Brazil. Nutrient Cycling in Agroecosystems. 2016; 105(1): 25-38. doi: https://doi.org/10.1007/s10705-016-9771-4
https://doi.org/10.1007/s10705-016-9771-...
), microbial abundance (Neves et al., 2021Neves LVMW, Fracetto FJC, Fracetto GGM, Araújo Filho JC, Araujo JKS, Santos JCB, et al. Microbial abundance and C and N stocks in tropical degraded Planosols from semi-arid northeastern Brazil. Catena [Internet]. 2021; 196(May 2020): 104931. doi: https://doi.org/10.1016/j.catena.2020.104931
https://doi.org/10.1016/j.catena.2020.10...
), physical and chemical soil quality (Mota et al., 2014Mota JCA, Alves CVO, Freire AG, Assis Júnior RN. Uni and multivariate analyses of soil physical quality indicators of a Cambisol from Apodi Plateau - CE, Brazil. Soil and Tillage Research. 2014; 140: 66-73. doi: https://doi.org/10.1016/j.still.2014.02.004
https://doi.org/10.1016/j.still.2014.02....
) and microclimate (Silva et al., 2021Silva TGF, Queiroz MG, Zolnier S, Souza LSB, Souza CAA, Moura MSB, et al. Soil properties and microclimate of two predominant landscapes in the Brazilian semi-arid region: Comparison between a seasonally dry tropical forest and a deforested area. Soil &Tillage Research. 2021; 207(October 2020): 104852. doi: https://doi.org/10.1016/j.still.2020.104852
https://doi.org/10.1016/j.still.2020.104...
) have been conducted in different SAB regions. Numerous studies have also shown the effects of degradation on the soil attributes of the SAB. Most of these studies have assessed these changes in the first soil layers (Mora and Lázaro, 2014Mora JL, Lázaro R. Seasonal changes in bulk density under semi-arid patchy vegetation: The soil beats. Geoderma [Internet]. 2014; 235-236: 30-8. doi: http://dx.doi.org/10.1016/j.geoderma.2014.06.022
http://dx.doi.org/10.1016/j.geoderma.201...
; Araújo Filho et al., 2017Araújo Filho JC, Ribeiro MR, Burgos N, Marques AM. Solos da Caatinga. In: Curi N, Ker JC, Novais RF, Vidal-Torrado P, Schaefer CEGR, editors. Pedologia: Solos Dos Biomas Brasileiros. Viçosa: Sociedade Brasileira de Ciência do Solo; 2017. p. 227-260, 2017. ISBN: 978-85-86504-22-8; Althoff et al., 2018Althoff TD, Menezes RSC, Pinto AS, Pareyn FGC, Carvalho AL, Martins JCR, et al. Adaptation of the century model to simulate C and N dynamics of Caatinga dry forest before and after deforestation. Agriculture, Ecosystems Environment. 2018; 254(May 2017): 26-34. doi: doi.org/10.1016/j.agee.2017.11.016
https://doi.org/10.1016/j.agee.2017.11.0...
) and, to a lesser extent, in depths greater than 40 cm and/or in subsurface pedogenetic horizons (Neves et al., 2021Neves LVMW, Fracetto FJC, Fracetto GGM, Araújo Filho JC, Araujo JKS, Santos JCB, et al. Microbial abundance and C and N stocks in tropical degraded Planosols from semi-arid northeastern Brazil. Catena [Internet]. 2021; 196(May 2020): 104931. doi: https://doi.org/10.1016/j.catena.2020.104931
https://doi.org/10.1016/j.catena.2020.10...
; Silva et al., 2021Silva TGF, Queiroz MG, Zolnier S, Souza LSB, Souza CAA, Moura MSB, et al. Soil properties and microclimate of two predominant landscapes in the Brazilian semi-arid region: Comparison between a seasonally dry tropical forest and a deforested area. Soil &Tillage Research. 2021; 207(October 2020): 104852. doi: https://doi.org/10.1016/j.still.2020.104852
https://doi.org/10.1016/j.still.2020.104...
; Menezes et al., 2021Menezes RSC, Sales AT, Primo DC, Albuquerque ERGM de, Jesus KN de, Pareyn FGC, et al. Soil and vegetation carbon stocks after land-use changes in a seasonally dry tropical forest. Geoderma. 2021; 390(July 2020): 114943. doi: https://doi.org/10.1016/j.geoderma.2021.114943
https://doi.org/10.1016/j.geoderma.2021....
).
Recently, some studies have sought to understand the relationships between biophysical variables and the flow of water and C in areas with different stages of degradation in the Caatinga (Borges et al., 2020Borges CK, Santos CAC, Carneiro RG, Silva LL, Oliveira G, Mariano D, et al. Seasonal variation of surface radiation and energy balances over two contrasting areas of the seasonally dry tropical forest (Caatinga) in the Brazilian semi-arid. Environmental Monitoring Assessment. 2020; 192(8). doi: https//doi.org/10.1007/s10661-020-08484-y
https//doi.org/10.1007/s10661-020-08484-...
; Oliveira et al., 2021Oliveira ML, Santos CAC, Oliveira G, Perez-Marin AM, Santos CAG. Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers. Science of Total Environment [Internet]. 2021;792:148458. doi: https://doi.org/10.1016/j.scitotenv.2021.148458
https://doi.org/10.1016/j.scitotenv.2021...
). These studies showed that the degradation of the Caatinga can modify the local microclimate by reducing atmospheric C sequestration and increasing greenhouse gas emissions.
Despite the importance of these studies, combined with the fact that soil properties and attributes can be safely used to assess soil quality (Maurya et al., 2020Maurya S, Abraham JS, Somasundaram S, Toteja R, Gupta R, Makhija S. Indicators for assessment of soil quality: a mini-review. Environmental Monitoring Assessment. 2020;192(9). doi: https://doi.org/10.1007/s10661-020-08556-z
https://doi.org/10.1007/s10661-020-08556...
). Research that seeks to evaluate the physical, chemical and biological attributes of soils under Caatinga in different stages of regeneration has been neglected (Silva et al., 2021Silva TGF, Queiroz MG, Zolnier S, Souza LSB, Souza CAA, Moura MSB, et al. Soil properties and microclimate of two predominant landscapes in the Brazilian semi-arid region: Comparison between a seasonally dry tropical forest and a deforested area. Soil &Tillage Research. 2021; 207(October 2020): 104852. doi: https://doi.org/10.1016/j.still.2020.104852
https://doi.org/10.1016/j.still.2020.104...
).
Thus, in this research we seek to evaluate the physical, chemical and biological attributes of soil layers exposed on the surface by land degradation, where even after interventions and actions towards reforestation, it still has a slow capacity for vegetation regeneration. This scenario is similar to that observed for other regions in the SAB, where extensive heavily degraded areas have truncated soils, with subsurface horizons of high unavailability for agricultural use exposed on the surface (CGEE, 2016Centro de Gestão e Estudos Estratégicos - CGEE. Desertificação, degradação da terra e secas no Brasil. 2016 [cited 2022 apr 07]. Available from: https://www.cgee.org.br/documents/10195/734063/DesertificacaoWeb.pdf
https://www.cgee.org.br/documents/10195/...
; Macedo et al., 2021Macedo, RS, Beirigo RM, Medeiros BM, Felix, VJL, Souza RFS, Bakker AP. Processos Pedogenéticos e Susceptibilidade dos Solos à Degradação no Semiárido brasileiro. Revista Caminhos de Geografia, 2021; 22(81): 176-195. doi: http://doi.org/10.14393/RCG228155397
http://doi.org/10.14393/RCG228155397...
).
In this context, this integrated study of soil attributes can contribute to the understanding of the effects of human actions on the dynamics and stock of nutrients in soils at different stages of degradation, as well as elucidate the mechanisms involved in the recovery of fertility and ecosystem services of these soils with the restoration of vegetation. Certainly, this knowledge will also contribute to strategic actions aimed at reincorporating extensive areas of degraded soils in the SAB into agricultural activities, increasing the resilience and food security of family agroecosystems in the face of climatic adversities in the region.
The objective of this research was to evaluate physical, chemical and microbiological attributes of soils in two areas of Caatinga (dense shrubby Caatinga - CAD; sparse shrubby Caatinga - CAE) subjected to anthropic pressures in the SAB.
2. MATERIAL AND METHODS
2.1 Study area
The research was carried out at the Experimental Station Prof. Ignácio Salcedo, belonging to the Instituto Nacional do Semiárido (INSA), municipality of Campina Grande, state of Paraíba, Brazil. An area under dense shrubby Caatinga (CAD) and another under sparse shrubby Caatinga (CAE) was studied (Figure 1).
The CAD site (7°16'47.76"S and 35°58'29.21"W; 480 m) corresponds to a legal reserve area with approximately 300 ha of dense preserved vegetation in different stages of regeneration, primarily consisting of shrubs and tree species typical of the Caatinga biome. The species commonly found in the area are umburana (Spondias tuberosa Arruda), pereiro (Aspidosperma pyrifolium Mart), imburana (Comminphora leptophloeos (Mart) J. B. Gillet), mandacaru (Cereus jamacaru DC.), facheiro (Pilosocereus pachycladus Ritter), marmeleiro (Croton sonderianus Müll. Arg), umburana (Amburana cearensis (Fr All) A. C. C. Smith), catingueira (Poincianella bracteosa (Tul.) L. P. Queiroz), mororó (Bauhinia cheilantha (bong.) steud), jurema branca (Mimosa verrucosa), jurema preta (Mimosa tenuiflora (Wild.) Poir), jurema unhade-gato (Mimosa sp.) and joão mole (Guapira sp.). The local vegetation is classified as dense shrubby Caatinga (Rizzini, 1997Rizzini CT, editor. Tratado de fitogeografia do Brasil. 2ª. ed. Rio de Janeiro: Âmbito Cultural Edições; 1997. ISBN: 9788586742200.).
The CAE site (7°14'59.78"S and 35°56'49.70"W; 500 m) corresponds to a borrow area where the surface horizon of the soil was removed to supply material for the construction of a nearby road. This process caused the exposure of the saprolitic layer (horizon C) on the surface, which presents characteristics of the source material and ample occurrence of partially weathered minerals. As part of the recovery process of this degraded area, in 2018, reforestation was carried out with adapted and native species in the region, such as white jurema (Mimosa verrucosa), jurema preta (Mimosa tenuiflora (Wild.) Poir), guandu (Cajanus cajan), cunhã (Clitoria ternatea), crotalaria (Crotalarea juncea), marmeleiro (Croton sonderianus Müll. Arg) and pereiro (Aspidosperma pyrifolium Mart). This configuration results in a phytophysiognomy consisting of a low shrub stratum, with a maximum height of 3 m, being classified as a sparse shrubby Caatinga (Rizzini, 1997Rizzini CT, editor. Tratado de fitogeografia do Brasil. 2ª. ed. Rio de Janeiro: Âmbito Cultural Edições; 1997. ISBN: 9788586742200.).
The climate is semi-arid with low altitude and latitude (BSh) according to the Kõppen classification (Alvares et al., 2013Alvares CA, Stape JL, Sentelhas PC, Moraes Gonçalves JL, Sparovek G. Köppen's climate classification map for Brazil. Meteorol Zeitschrift. 2013;22(6):711-28. doi: https://doi.org/10.1127/0941-2948/2013/0507.
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). The average annual temperature is 23.3°C and the average annual rainfall is 503 mm. The native vegetation is the hyperxerophytic Caatinga, characterized as a dry xerophytic forest with sparsely distributed shrubs and small trees (less than 7 meters in height), and patches of grass that develop only during the rainy season (January to September).
The relief varies from gently undulating to undulating with elevations of flat tops, composed of slopes of tens of meters with dry and open valleys (Brasil, 1972). Leptsols predominate in the area, formed from the weathering of cataclastic leucogneiss with biotite (Brazil, 1972).
2.2 Soil collection and analysis
Soils were collected in August 2020. Year in which annual precipitation was 551.2 mm, with a rainy season between March and July (494.2 mm), corresponding to 89% of annual precipitation. In this rainy period, rainfall was 270.6 mm in March and April and 223.6 mm between May and July.
The experimental design used was completely randomized. The sampling was performed in two homogeneous areas of 1000 m2, with five collection points (experimental units), and at each point five simple deformed soil samples were collected (0-20 cm), which constituted a composite sample that was dried in air and passed through a 2 mm sieve (TFSA). At each collection point five undisturbed samples were also collected in 100 cm3 volumetric rings to perform soil density (Ds) analysis. The deformed samples were morphologically described according to Santos et al. (2015). Additional features such as rock volume and percentage of aggregates were evaluated according to Schoeneberger et al. (2012)Schoeneberger PJ, Wysocki DA, Benham EC, Soil Survey Staff. Field book for describing and sampling soils, Version 3.0. Lincoln: Natural Resources Conservation Service, National Soil Survey Center; 2012..
Sample preparation and physical and chemical analyses of the soils were performed at the INSA Soils and Mineralogy Laboratory according to methodologies proposed by Embrapa (Teixeira et al. 2017Teixeira PC, Donagemma GK, Fontana A, Teixeira WG, editors. Manual de Métodos de Análise de Solo. Brasília: 3. Embrapa Solos, 2017. ISBN 9788570357717.). Particle size analysis and water dispersed clay were performed by the pipette method, using NaOH and H2O as dispersants, respectively. Ds was obtained by the volumetric cylinder method.
The pH was determined in water (1:2.5 -TFSA:H2O) and the electrical conductivity (CE) was obtained using a direct reading conductivity meter (1:5.0 - TFSA:H2O). The exchangeable contents of Ca2+, Mg2+ and Al3+ were extracted with KCl 1 mol L-1, while P, K+ and Na+ were extracted with Mehlich 1 solution (HCl 0.05 mol L-1 + H2SO4 0.0125 mol L-1). Potential acidity (H + Al) was extracted with 0.5 mol L-1 calcium acetate pH 7.0. Ca2+ and Mg2+ were determined by complexometry, Al3+ by titration, K+ and Na+ by flame photometry and P by colorimetry. The total organic carbon (COT) was determined by the method proposed by Yeomans and Bremner (1988)Yeomans JC, Bremner JM. A rapid and precise method for routine determination of organic carbon in soil. Communications in Soil Science Plant Analysis. 1988;19(13):1467–76. doi: https://doi.org/10.1080/00103628809368027
https://doi.org/10.1080/0010362880936802...
. COT contents were converted to soil organic matter (MOS) from multiplication by the factor 1.724 (Machado et al., 2003Machado PLO, Bernardi ACC, Santos FS. Métodos de Preparo de Amostras e de Determinação de Carbono em Solos Tropicais. 2003;9. [accessed: 15 january.2022] Available from: https://ainfo.cnptia.embrapa.br/digital/bitstream/CNPS/11582/1/circtec_19_2003_metodos_preparo.pdf
https://ainfo.cnptia.embrapa.br/digital/...
). Total carbon (CT) was obtained via dry combustion in a CHNS elemental analyzer. Organic carbon stock (EstC) was calculated according to the following equation (Du et al., 2017Du Z, Cai Y, Yan Y, Wang X. Embedded rock fragments affect alpine steppe plant growth, soil carbon and nitrogen in the northern Tibetan Plateau. Plant and Soil. 2017;420(1-2):79-92. doi://doi.org/10.1007/s11104-017-3376-9
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):
Where: EstC (Mg ha-1) represents the concentration of organic carbon (g kg-1), Ds is the density of the soil (kg dm-3), E is the thickness of the evaluated layer (cm) and R is the content volumetric (%) of rock fragments > 2 mm in the soil.
With the results, the following indices were obtained: degree of flocculation (GF), base sum (SB), effective and total cation exchange capacity (CTCef), base saturation (V%), aluminum saturation (m%) and percentage of sodium saturation (PST) (Teixeira et al. 2017Teixeira PC, Donagemma GK, Fontana A, Teixeira WG, editors. Manual de Métodos de Análise de Solo. Brasília: 3. Embrapa Solos, 2017. ISBN 9788570357717.). Soil analysis results were interpreted according to Sobral et al. (2015)Sobral LF, Barreto MCV, Silva AJ da, Anjos JL dos. Guia Prático para Interpretação de Resultados de Análises de Solo. Embrapa Tabuleiros Costeiros-Documentos (INFOTECA-E). 2015;13..
The analyzes of the microbiological attributes were carried out at the Laboratory of Environmental Microbiology of INSA, evaluating the microbial biomass from the quantification of carbon (C-BMS), by the chloroform-fumigation-extraction (CEF) method (Vance et al., 1987Vance ED, Brookes PC, Jenkinson DS. An extraction method for measuring soil microbial biomass C. Soil Biology and Biochemistry. 1987; 19(6):703–7. doi: https://doi.org/10.1016/0038-0717(87)90052-6
https://doi.org/10.1016/0038-0717(87)900...
) and the activity microbial growth by basal soil respiration (RBS) (Jenkinson and Powlson, 1976Jenkinson DS, Powlson DS. The effects of biocidal treatments on metabolism in soil-I. A method for measuring soil biomass. Soil Biology and Biochemistry. 1976;8(5):209-2013. doi: https://doi.org/10.1016/0038-0717(76)90001-8
https://doi.org/10.1016/0038-0717(76)900...
). The metabolic quotient (qCO2) values, which express the ratio between basal respiration and soil microbial biomass per unit of time, were calculated by dividing CBM by RBS.
2.3 Data analysis
The data obtained were submitted to the nonparametric Mann-Whitney test (p < 0.05). In addition, principal component analyzes (PCA) were performed in order to reduce the large number of variables to a more significant set. The R software (version 4.1.0) was used for such analyzes (CoreTeam, 2017CoreTeam R. R: A Language and Environment for Statistical Computing [Internet]. Vol. 2. 2017. Available from: https://www.r-project.org/
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).
3. RESULTS
3.1 Morphology and physical attributes
The morphological and physical attributes of the studied areas are shown in Table 1. The soil under CAD is dark yellowish-brown and under CAE it is dark gray. Mottles occur only on the ground under CAE. Very friable medium/large subangular blocks predominate in the area under CAD, while extremely hard/firm massive structure was identified in CAE. Roots of varying sizes are common or abundant only in soil under CAD.
Morphological and physical attributes of the 0-20 cm layer of soils under sparse (CAE) and dense (CAD) shrubby Caatinga in the Brazilian semi-arid region. Experimental Station of the Instituto Nacional do Semiárido (INSA), municipality of Campina Grande, PB, Brazil.
Tabela 1
Atributos morfológicos e físicos da camada de 0-20 cm de solos sob Caatinga arbustiva esparsa (CAE) e densa (CAD) no Semiárido brasileiro. Estação Experimental do Instituto Nacional do Semiárido (INSA), município de Campina Grande, PB, Brasil.
The soil under CAE is sandy loam, while the soil under CAD is sandy loam (Table 1). There is no significant difference in sand, ADA and GF contents between the evaluated soils. Silt contents are significantly higher in CAE, while clay contents are significantly higher in CAD (p < 0.05). Silt contents are significantly higher under CAE, while Ds is significantly higher under CAD.
3.2 Chemical Attributes
The chemical attributes of the studied areas are presented in Table 2. Soil under CAE is practically neutral, while soil under CAD is moderately acidic. The low content of Ca2+ in the soil of CAE is significantly lower than the content considered high in the CAD (CAE: 0.5; CAD: 3.3 cmolc kg-1; p < 0.05). The average Mg2+ content in CAE is significantly lower than in CAD (CAE: 1.0; CAD: 1.9 cmolc kg-1; p < 0.05). Both soils have high K+ contents, although significantly higher in CAD (CAE: 1.2; CAD: 7.9 cmolc kg-1; p < 0.05). Al3+ and P contents are low in both evaluated soils, although P is significantly higher in CAD.
Chemical attributes, soil organic matter (MOS), total organic carbon (COT), carbon stock (EstC) and total carbon (CT) of soils in soils under sparse (CAE) and dense shrubby (CAD) soils in the Brazilian semi-arid region. Experimental Station of the Instituto Nacional do Semiárido (INSA), municipality of Campina Grande, PB, Brazil.
Tabela 2
Atributos químicos, teores de matéria orgânica solo (MOS), carbono orgânico total (COT), estoque de carbono (EstC) e carbono total (CT) de solos sob Caatinga arbustiva esparsa (CAE) e densa (CAD) no Semiárido brasileiro. Estação Experimental do Instituto Nacional do Semiárido (INSA), município de Campina Grande, PB, Brasil.
CTCef is high in both soils, being significantly higher in CAD (Table 2). The base saturation (V%) is high and significantly higher in the soil under CAE (CAE: 82.6; CAD: 64.9%; p < 0.05), while the aluminum saturation is low in both soils and significantly higher under CAD. Electrical conductivity (EC) is low in both soils and significantly higher in CAD. The PST in the CAE is high and significantly higher than the levels considered low for the CAD (CAE: 34.5; CAD: 4.3%; p < 0.05).
The COT (CAE: 3.6; CAD: 46.2 g kg-1; p < 0.05) and CT (CAE: 6.4; CAD: 100.1%; p < 0.05) contents are significantly higher in CAD. Therefore, EstC is also significantly higher in soil under CAD (CAE: 2.1; CAD: 19.2 Mg ha-1; p < 0.05).
3.3 Microbiological attributes
No significant difference was observed in microbial biomass carbon content (C-BMS) for the evaluated soils (Table 3). On the other hand, RBS (CAE: 0.34; CAD: 0.91 mg g-1 h-1; p < 0.05) and qCO2 (CAE: 2.0; CAD: 5.7 mg g-1 h-1; p < 0.05) are significantly higher in CAD.
Microbiological attributes of soils under sparse (CAE) and dense (CAD) shrubby Caatinga in the Brazilian semi-arid region. Experimental Station of the Instituto Nacional do Semiárido (INSA), municipality of Campina Grande, PB, Brazil.
Tabela 3
Atributos microbiológicos de solos sob Caatinga arbustiva esparsa (CAE) e densa (CAD) no Semiárido brasileiro. Estação Experimental do Instituto Nacional do Semiárido (INSA), município de Campina Grande, PB, Brasil.
3.4 Principal Component Analysis
The analysis of principal components of the physical, chemical and microbiological attributes of soils is presented in Figure 2. The two main components explained 87.6% of the data variability, with 78.5% and 8.9% being attributed to PCA1 and PCA2, respectively. The positive dimension of PCA1 is constituted by the attributes argila, ADA, GF, Ds, CE, Al3+, Ca2+, Mg2+, K+, P, H+Al, SB, T, CTCef, COT, EstC, MOS, CT, m%, qCO2 e RBS, while the negative dimension is composed of areia, silte, pH, V, Na+ and PST. On the other hand, the positive dimension of PCA 2 is composed of the attributes pH, V, PST, Ca2+, Al3+, Na+, areia, ADA, SB, T, SB, m%, CTCef, K+, P, H+Al, CE, COT, Estc, MOS, CT, while the negative dimension consists of silte, m%, Ds, Mg2+, RBS, qCO2, argila e GF.
Principal Component Analysis (PCA) of physical, chemical and microbiological attributes of soils under sparse (CAE) and dense (CAD) shrubby Caatinga in the Brazilian semi-arid region. Experimental Station of the Instituto Nacional do Semiárido (INSA), municipality of Campina Grande, PB, Brazil. CAE: 1-5; CAD: 6-10. Active acidity (pHH2O), Potential acidity (H+Al), electric conductivity (CE), available levels of P, exchangeable levels of Ca2+, Mg2+ e Al3+, extractabte contents of K+ e Na+, total carbon (CT), total organic carbon (COT), soil carbon stock (EstC), soil organic matter (MOS), effective cation exchange capacity (CTCef), cation exchange capacity at pH 7.0 (T), sum of bases (SB), base saturation (V%), aluminum saturation (m%), sodium saturation percentage (PST), granulometry (sand, silt and clay), clay dispersed in water (ADA), soil density (Ds), flocculation degree (GF), carbon from soil microbial biomass (C-BMS), basal soil respiration (RBS) e metabolic quotient (qCO2).
Figura 2
Análise de Componentes Principais (ACP) de atributos físicos, químicos e microbiológicos de solos sob Caatinga arbustiva esparsa (CAE) e densa (CAD) no Semiárido brasileiro. Estação Experimental do Instituto Nacional do Semiárido (INSA), município de Campina Grande, PB, Brasil. CAE: 1-5; CAD: 6-10. Acidez ativa (pHH2O), acidez potencial (H+Al), condutividade elétrica (CE), teores disponíveis de P, teores trocáveis de Ca2+, Mg2+ e Al3+, teores extraíveis de K+ e Na+, carbono total (CT), carbono orgânico total (COT), estoque de carbono no solo (EstC), matéria orgânica do solo (MOS), capacidade de troca de cátions efetiva (CTCef), capacidade de troca de cátions a pH 7,0 (T), soma de bases (SB), saturação por bases (V%), saturação por alumínio (m%), percentagem de saturação por sódio (PST), granulometria (areia, silte e argila), argila dispersa em água (ADA), densidade do solo (Ds), grau de floculação (GF), carbono da biomassa microbiana do solo (C-BMS), respiração basal do solo (RBS) e quociente metabólico (qCO2).
4. DISCUSSION
4.1 Degradation and physical attributes of soils
Our results showed that the removal of the Caatinga followed by the removal of the surface layer of the soil significantly altered soil properties. Such practices intensified the erosive processes in the area currently under sparse shrubby Caatinga (the authors observations), which resulted in the loss of the soil surface horizon (horizon A) and the exposure of the saprolite surface (horizon Crn). The occurrence of > 50% of rock structure, < 50% of soil aggregates and massive structure confirm the occurrence of saprolite (Juilleret et al., 2016Juilleret, J.; Corrêa, MM.; Azevedo, AC. Porosity and genesis of clay in gneiss saprolites: The relevance of saprolithology to whole regolith pedology. Geoderma, 319, 1-13, 2018. doi: https://doi.org/10.1016/j.geoderma.2017.12.031.
https://doi.org/10.1016/j.geoderma.2017....
).
No variability was found in the sand contents, given the predominance of quartz in the soil source material and the low precipitation rates in the region. The higher levels of silt in CAE reflect the incipient pedogenesis of the saprolytic layer. The high silt/clay ratio confirms the moderate weathering in the saprolite, delaying the transformation and/or dissolution of plagioclases and micas that remain in the soils at silt particle size (Santos et al., 2018).
Studies have shown that seasonality and different land use systems alter Ds in semi-arid regions (Mora and Lazaro, 2014Mora JL, Lázaro R. Seasonal changes in bulk density under semi-arid patchy vegetation: The soil beats. Geoderma [Internet]. 2014; 235-236: 30-8. doi: http://dx.doi.org/10.1016/j.geoderma.2014.06.022
http://dx.doi.org/10.1016/j.geoderma.201...
; Silva et al., 2021Silva TGF, Queiroz MG, Zolnier S, Souza LSB, Souza CAA, Moura MSB, et al. Soil properties and microclimate of two predominant landscapes in the Brazilian semi-arid region: Comparison between a seasonally dry tropical forest and a deforested area. Soil &Tillage Research. 2021; 207(October 2020): 104852. doi: https://doi.org/10.1016/j.still.2020.104852
https://doi.org/10.1016/j.still.2020.104...
). In this research, Ds reflects the higher temperature on the surface of degraded soils, since it is more exposed (Oliveira et al., 2021Oliveira ML, Santos CAC, Oliveira G, Perez-Marin AM, Santos CAG. Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers. Science of Total Environment [Internet]. 2021;792:148458. doi: https://doi.org/10.1016/j.scitotenv.2021.148458
https://doi.org/10.1016/j.scitotenv.2021...
), which contributes to the reduction of MOS from the oxidation of carbon with a consequent increase in Ds. In addition, in the soil under CAD there is a greater contribution of litter and roots, which contributes to an increase in MOS and a reduction in Ds.
4.2 Degradation and chemical attributes of soils
The more acidic reaction of soils in CAD is mainly due to the ionization of H+ ions from carboxylic and phenolic acids, and notably from tertiary alcohols from organic matter (Silva and Mendonça, 2007Silva IR, Mendonça ES. Acidez do solo e sua correção. In: Novais RF, Alvarez VVH, Barros NF, Fontes RLF, Cantarutti RB, Neves JCL, editors. Fertilidade do Solo. Viçosa: Sociedade Brasileira de Ciência do Solo; 2007. p. 206-374. ISBN: 9788586504082). On the other hand, the practically neutral condition of the saprolite reflects its origin from gneisses and amphibolites, which release considerable amounts of basic reaction cations (Santos et al., 2017Santos JCB, Le Pera E, Souza Júnior VS, Corrêa MM, Azevedo AC. Gneiss saprolite weathering and soil genesis along an east-west regolith sequence (NE Brazil). Catena [Internet]. 2017;150(October):279–90. doi: http://dx.doi.org/10.1016/j.catena.2016.11.031
http://dx.doi.org/10.1016/j.catena.2016....
; Câmara et al., 2021Câmara ERG, Santos JCB, Araújo Filho JC, Schulze SMBB, Corrêa MM, Ferreira TO, et al. Parent rock-pedogenesis relationship: How the weathering of metamorphic rocks influences the genesis of Planosols and Luvisols under a semi-arid climate in NE Brazil. doi: Geoderma. 2021;385(December 2020). Available from: https://doi.org/10.1016/j.geoderma.2020.114878
https://doi.org/10.1016/j.geoderma.2020....
).
Soils under CAE have a eutrophic character (V > 50%). However, in these soils Na+ ions predominate in the exchange complex, while K+, Ca2+ e Mg2+ are dominant in soils under CAD. This fact confirms that the removal of the surface layer of soils and the consequent exposure of the saprolite on the surface reduces soil fertility, which corresponds to 75% of the Ca2+ and K+ contents and 47% of the Mg2+ contents. This lower availability of nutrients, together with the greater compactness of the saprolite, contributes to the slow regeneration of vegetation in the area.
Degradation promoted an increase in surface Na+ contents. Surprisingly, these contents are much higher than the average values found in natric horizons in the SAB (Brasil, 1972; Oliveira Filho et al., 2020Oliveira Filho JS, Pinheiro Junior CR, Pereira MG, Valladares GS, Camara R. Sodification and solodization processes: Pedogenesis or natural soil degradation? Journal of South American Earth Sciences. 2020;104(June): 102909. doi: https://doi.org/10.1016/j.jsames.2020.102909
https://doi.org/10.1016/j.jsames.2020.10...
). These levels confirmed the sodium character (PST ≥ 15%) of the saprolite, whose origin is mainly credited to the weathering of plagioclases (dos Santos et al., 2018). In semi-arid regions, where the potential for evapotranspiration exceeds precipitation, Na+ tends to predominate in the exchange (sodification) complex (Araújo Filho et al., 2017Araújo Filho JC, Ribeiro MR, Burgos N, Marques AM. Solos da Caatinga. In: Curi N, Ker JC, Novais RF, Vidal-Torrado P, Schaefer CEGR, editors. Pedologia: Solos Dos Biomas Brasileiros. Viçosa: Sociedade Brasileira de Ciência do Solo; 2017. p. 227-260, 2017. ISBN: 978-85-86504-22-8), which can lead to colloidal dispersion and reduced soil permeability, making regeneration difficult from degraded areas.
Significant carbon losses in degraded soils in the Brazilian semi-arid region have been reported (Neves et al., 2021Neves LVMW, Fracetto FJC, Fracetto GGM, Araújo Filho JC, Araujo JKS, Santos JCB, et al. Microbial abundance and C and N stocks in tropical degraded Planosols from semi-arid northeastern Brazil. Catena [Internet]. 2021; 196(May 2020): 104931. doi: https://doi.org/10.1016/j.catena.2020.104931
https://doi.org/10.1016/j.catena.2020.10...
; Santos et al., 2022Santos TO, Cury Fracetto FJ, Souza Júnior VS, Araújo Filho JC, Lira Junior MA, Mendes Júnior JP, et al. Carbon and nitrogen stocks and microbial indicators in tropical semi-arid degraded Luvisols. Catena. 2022; 210:105885. doi: https://doi.org/10.1016/j.catena.2021.105885
https://doi.org/10.1016/j.catena.2021.10...
). Our results confirm these observations, where the exposure of saprolite on the surface represents a reduction of 93.6% in CT and 87.8% in EstC, when compared to the surface layer of soil under CAD. Although the Caatinga vegetation in both areas acts as a carbon sink (Oliveira et al., 2021Oliveira ML, Santos CAC, Oliveira G, Perez-Marin AM, Santos CAG. Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers. Science of Total Environment [Internet]. 2021;792:148458. doi: https://doi.org/10.1016/j.scitotenv.2021.148458
https://doi.org/10.1016/j.scitotenv.2021...
), our results indicate that only soils under CAD store carbon at levels reported for other areas of the Caatinga biome, even in amounts greater than found in Caatinga preserved under similar soils (Althoff et al., 2018Althoff TD, Menezes RSC, Pinto AS, Pareyn FGC, Carvalho AL, Martins JCR, et al. Adaptation of the century model to simulate C and N dynamics of Caatinga dry forest before and after deforestation. Agriculture, Ecosystems Environment. 2018; 254(May 2017): 26-34. doi: doi.org/10.1016/j.agee.2017.11.016
https://doi.org/10.1016/j.agee.2017.11.0...
).
Thus, considering that Leptsols sequester an average of 65 Mg ha-1 of total carbon, which corresponds to between 70 and 80% of the total carbon stock of ecosystems with Caatinga vegetation (Menezes et al., 2021Menezes RSC, Sales AT, Primo DC, Albuquerque ERGM de, Jesus KN de, Pareyn FGC, et al. Soil and vegetation carbon stocks after land-use changes in a seasonally dry tropical forest. Geoderma. 2021; 390(July 2020): 114943. doi: https://doi.org/10.1016/j.geoderma.2021.114943
https://doi.org/10.1016/j.geoderma.2021....
), our results prove that degradation compromises atmospheric carbon sequestration, with direct impacts on the carbon cycle and the provision of ecosystem services, notably those related to regional climate regulation.
4.3 Degradation and microbiological attributes of soils
Soil microbiological attributes can be significantly altered with changes in land use, management practices and soil degradation (Kaschuk et al., 2010Kaschuk G, Alberton O, Hungria M. Three decades of soil microbial biomass studies in Brazilian ecosystems: Lessons learned about soil quality and indications for improving sustainability. Soil Biology and Biochemistry [Internet]. 2010;42(1):1-13. doi: http://dx.doi.org/10.1016/j.soilbio.2009.08.020
http://dx.doi.org/10.1016/j.soilbio.2009...
; Araújo Filho et al., 2018Araújo Filho RN, Freire MBGS, Wilcox BP, West JB, Freire FJ, Marques FA. Recovery of carbon stocks in deforested Caatinga dry forest soils requires at least 60 years. Forest Ecology and Management [Internet]. 2018; 407(May): 210-20. doi: http://dx.doi.org/10.1016/j.foreco.2017.10.002
http://dx.doi.org/10.1016/j.foreco.2017....
). The C-BMS values found for CAD and CAE are similar to those found for soils under different uses in the Caatinga (72 and 385 mg C kg-1) (Kachuck et al., 2010).
The highest RBS observed in the CAD area indicates high biological activity and decomposition of organic matter, with a consequent high level of productivity in the ecosystem (Silva et al., 2007Silva RF, Tomazi M, Pezarico CR, Aquino AM, Mercante FM. Macrofauna invertebrada edáfica em cultivo de mandioca sob sistemas de cobertura do solo. Pesquisa Agropecuária Brasileira. 2007;42(6):865–71. doi: https://doi.org/10.1590/s0100-204x2007000600014
https://doi.org/10.1590/s0100-204x200700...
). A study carried out in agroforestry systems found greater RBS in the surface layer of the soil, associated with a greater amount of organic residues in this layer (Pezarico et al., 2013Pezarico CR, Vitorino ACT, Mercante FM, Daniel O. Indicadores de qualidade do solo em sistemas agroflorestais. Revista de Ciências Agrárias -Amazonian Journal of Agricultural Environmental Sciences. 2013;56(1):40-7. doi: http://dx.doi.org/10.4322/rca.2013.004
http://dx.doi.org/10.4322/rca.2013.004...
), corroborating the results of our study, where the CAD presented a greater amount of MOS.
The highest values of qCO2 in soil under CAD reflect the release of CO2 throughout the process of mineralization of organic matter. Higher values of qCO2 were observed in forests and significantly decreased in soil under cultivation (Dinesh et al., 2003Dinesh R, Chaudhuri SG, Ganeshamurthy AN, Dey C. Changes in soil microbial indices and their relationships following deforestation and cultivation in wet tropical forests. Applied Soil Ecology. 2003;24(1):17-26. doi: https://doi.org/10.1016/S0929-1393(03)00070-2
https://doi.org/10.1016/S0929-1393(03)00...
). According to the authors, these high values suggest that soil microorganisms in forests need high energy compared to cultivated sites. Higher values of qCO2 in an area of native Caatinga when compared to cultivated areas are indicative that the microbial biomass in areas without cultivation has greater metabolic activity.
On the other hand, the significantly lower qCO2 in CAE may indicate an economy in the use of energy by microorganisms in the saprolitic layer, which have become more efficient in the use of ecosystem resources, releasing less CO2 into the atmosphere and incorporating more carbon contents to microbial tissues. This fact indicates a stable system, but not necessarily with a high level of productivity.
4.4. Degradation and density of vegetation cover
PCA clearly individualized the topsoil under CAD and the saprolite of the CAE area. In this way, we show that the slow regeneration of the Caatinga vegetation is taking place in a saprolitic layer with: (i) imperfect drainage, inferred by the occurrence of gray mottling (7.5YR 4/1) indicative of oxidation-reduction processes (gleization); (ii) low clay content, which implies a lower amount of clay minerals responsible for the high cation exchange capacity in saprolites in the SAB (Santos et al., 2017Santos JCB, Le Pera E, Souza Júnior VS de, Oliveira CS, Juilleret J, Corrêa MM, et al. Porosity and genesis of clay in gneiss saprolites: The relevance of saprolithology to whole regolith pedology. Geoderma [Internet]. 2018;319(August 2017):1–13. doi: https://doi.org/10.1016/j.geoderma.2017.12.031
https://doi.org/10.1016/j.geoderma.2017....
); (iii) low levels of organic matter and carbon, with adverse implications for the phenomena of nutrient adsorption and water absorption; (iv) high sodicity; and (v) reduced microbiological activity, which can compromise the mineralization of organic compounds and, therefore, the release of nutrients to plants.
On the other hand, soils under CAD have higher levels of nutrients and organic matter, with carbon stocks at levels similar or superior to other areas with preserved Caatinga vegetation. This explains the higher stage of vegetation regeneration in these soils, presenting higher primary production and significant contribution to atmospheric carbon sequestration (Oliveira et al., 2021Oliveira ML, Santos CAC, Oliveira G, Perez-Marin AM, Santos CAG. Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers. Science of Total Environment [Internet]. 2021;792:148458. doi: https://doi.org/10.1016/j.scitotenv.2021.148458
https://doi.org/10.1016/j.scitotenv.2021...
). These conditions allow the characterization of this area as highly complex, given its capacity to maintain important ecosystem services for the semi-arid region, such as nutrient cycling, primary production (support services), erosion control and climate regulation (regulation services) (Araújo et al., 2021Araújo HFP, Machado CCC, Pareyn FGC, Nascimento NFF, Araújo LDA, Borges LA de AP, et al. A sustainable agricultural landscape model for tropical drylands. Land Use Policy. 2021; 100(July), 104913. doi: https://doi.org/10.1016/j.landusepol.2020.104913.
https://doi.org/10.1016/j.landusepol.202...
).
5. CONCLUSIONS
The removal of native vegetation followed by degradation causes the removal of the surface horizon of the soils and promotes the exposure on the surface of a saprolitic layer with high compactness, low nutrient and organic matter contents and high sodium contents.
Degradation significantly reduces the carbon stock and biological activity of the soil, resulting in an increase in carbon emissions into the atmosphere and savings in energy use by microorganisms, with adverse implications for the mineralization of organic matter and the release of nutrients.
Ecosystem services related to climate regulation and nutrient cycling are compromised with degradation. This adverse scenario increases the vulnerability of these areas to extreme weather events and the process of desertification, the latter due to regressive changes in soils, vegetation and water regime, leading to local biological deterioration, with direct implications for both the regeneration of Caatinga, as for the establishment of its productive capacity.
6. REFERENCES
- Althoff TD, Menezes RSC, Pinto AS, Pareyn FGC, Carvalho AL, Martins JCR, et al. Adaptation of the century model to simulate C and N dynamics of Caatinga dry forest before and after deforestation. Agriculture, Ecosystems Environment. 2018; 254(May 2017): 26-34. doi: doi.org/10.1016/j.agee.2017.11.016
» https://doi.org/10.1016/j.agee.2017.11.016 - Alvares CA, Stape JL, Sentelhas PC, Moraes Gonçalves JL, Sparovek G. Köppen's climate classification map for Brazil. Meteorol Zeitschrift. 2013;22(6):711-28. doi: https://doi.org/10.1127/0941-2948/2013/0507
» https://doi.org/10.1127/0941-2948/2013/0507 - Araújo HFP, Machado CCC, Pareyn FGC, Nascimento NFF, Araújo LDA, Borges LA de AP, et al. A sustainable agricultural landscape model for tropical drylands. Land Use Policy. 2021; 100(July), 104913. doi: https://doi.org/10.1016/j.landusepol.2020.104913
» https://doi.org/10.1016/j.landusepol.2020.104913 - Araújo Filho JC, Ribeiro MR, Burgos N, Marques AM. Solos da Caatinga. In: Curi N, Ker JC, Novais RF, Vidal-Torrado P, Schaefer CEGR, editors. Pedologia: Solos Dos Biomas Brasileiros. Viçosa: Sociedade Brasileira de Ciência do Solo; 2017. p. 227-260, 2017. ISBN: 978-85-86504-22-8
- Araújo Filho RN, Freire MBGS, Wilcox BP, West JB, Freire FJ, Marques FA. Recovery of carbon stocks in deforested Caatinga dry forest soils requires at least 60 years. Forest Ecology and Management [Internet]. 2018; 407(May): 210-20. doi: http://dx.doi.org/10.1016/j.foreco.2017.10.002
» http://dx.doi.org/10.1016/j.foreco.2017.10.002 - Borges CK, Santos CAC, Carneiro RG, Silva LL, Oliveira G, Mariano D, et al. Seasonal variation of surface radiation and energy balances over two contrasting areas of the seasonally dry tropical forest (Caatinga) in the Brazilian semi-arid. Environmental Monitoring Assessment. 2020; 192(8). doi: https//doi.org/10.1007/s10661-020-08484-y
» https//doi.org/10.1007/s10661-020-08484-y - Câmara ERG, Santos JCB, Araújo Filho JC, Schulze SMBB, Corrêa MM, Ferreira TO, et al. Parent rock-pedogenesis relationship: How the weathering of metamorphic rocks influences the genesis of Planosols and Luvisols under a semi-arid climate in NE Brazil. doi: Geoderma. 2021;385(December 2020). Available from: https://doi.org/10.1016/j.geoderma.2020.114878
» https://doi.org/10.1016/j.geoderma.2020.114878 - Centro de Gestão e Estudos Estratégicos - CGEE. Desertificação, degradação da terra e secas no Brasil. 2016 [cited 2022 apr 07]. Available from: https://www.cgee.org.br/documents/10195/734063/DesertificacaoWeb.pdf
» https://www.cgee.org.br/documents/10195/734063/DesertificacaoWeb.pdf - CoreTeam R. R: A Language and Environment for Statistical Computing [Internet]. Vol. 2. 2017. Available from: https://www.r-project.org/
» https://www.r-project.org/ - Dinesh R, Chaudhuri SG, Ganeshamurthy AN, Dey C. Changes in soil microbial indices and their relationships following deforestation and cultivation in wet tropical forests. Applied Soil Ecology. 2003;24(1):17-26. doi: https://doi.org/10.1016/S0929-1393(03)00070-2
» https://doi.org/10.1016/S0929-1393(03)00070-2 - Du Z, Cai Y, Yan Y, Wang X. Embedded rock fragments affect alpine steppe plant growth, soil carbon and nitrogen in the northern Tibetan Plateau. Plant and Soil. 2017;420(1-2):79-92. doi://doi.org/10.1007/s11104-017-3376-9
» https://doi.org/10.1007/s11104-017-3376-9 - Jenkinson DS, Powlson DS. The effects of biocidal treatments on metabolism in soil-I. A method for measuring soil biomass. Soil Biology and Biochemistry. 1976;8(5):209-2013. doi: https://doi.org/10.1016/0038-0717(76)90001-8
» https://doi.org/10.1016/0038-0717(76)90001-8 - Juilleret, J.; Corrêa, MM.; Azevedo, AC. Porosity and genesis of clay in gneiss saprolites: The relevance of saprolithology to whole regolith pedology. Geoderma, 319, 1-13, 2018. doi: https://doi.org/10.1016/j.geoderma.2017.12.031
» https://doi.org/10.1016/j.geoderma.2017.12.031 - Kaschuk G, Alberton O, Hungria M. Three decades of soil microbial biomass studies in Brazilian ecosystems: Lessons learned about soil quality and indications for improving sustainability. Soil Biology and Biochemistry [Internet]. 2010;42(1):1-13. doi: http://dx.doi.org/10.1016/j.soilbio.2009.08.020
» http://dx.doi.org/10.1016/j.soilbio.2009.08.020 - Macedo, RS, Beirigo RM, Medeiros BM, Felix, VJL, Souza RFS, Bakker AP. Processos Pedogenéticos e Susceptibilidade dos Solos à Degradação no Semiárido brasileiro. Revista Caminhos de Geografia, 2021; 22(81): 176-195. doi: http://doi.org/10.14393/RCG228155397
» http://doi.org/10.14393/RCG228155397 - Machado PLO, Bernardi ACC, Santos FS. Métodos de Preparo de Amostras e de Determinação de Carbono em Solos Tropicais. 2003;9. [accessed: 15 january.2022] Available from: https://ainfo.cnptia.embrapa.br/digital/bitstream/CNPS/11582/1/circtec_19_2003_metodos_preparo.pdf
» https://ainfo.cnptia.embrapa.br/digital/bitstream/CNPS/11582/1/circtec_19_2003_metodos_preparo.pdf - Maurya S, Abraham JS, Somasundaram S, Toteja R, Gupta R, Makhija S. Indicators for assessment of soil quality: a mini-review. Environmental Monitoring Assessment. 2020;192(9). doi: https://doi.org/10.1007/s10661-020-08556-z
» https://doi.org/10.1007/s10661-020-08556-z - Menezes RSC, Sales AT, Primo DC, Albuquerque ERGM de, Jesus KN de, Pareyn FGC, et al. Soil and vegetation carbon stocks after land-use changes in a seasonally dry tropical forest. Geoderma. 2021; 390(July 2020): 114943. doi: https://doi.org/10.1016/j.geoderma.2021.114943
» https://doi.org/10.1016/j.geoderma.2021.114943 - Ministério da Agricultura e do Interior- BRASIL. Levantamento exploratório-reconhecimento de solos do estado da Paraíba. 1972 [cited 2022 apr 07]. Available from: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/330784
» http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/330784 - Mora JL, Lázaro R. Seasonal changes in bulk density under semi-arid patchy vegetation: The soil beats. Geoderma [Internet]. 2014; 235-236: 30-8. doi: http://dx.doi.org/10.1016/j.geoderma.2014.06.022
» http://dx.doi.org/10.1016/j.geoderma.2014.06.022 - Moura PM, Althoff TD, Oliveira RA, Souto JS, Souto PC, Menezes RSC, et al. Carbon and nutrient fluxes through litterfall at four succession stages of Caatinga dry forest in Northeastern Brazil. Nutrient Cycling in Agroecosystems. 2016; 105(1): 25-38. doi: https://doi.org/10.1007/s10705-016-9771-4
» https://doi.org/10.1007/s10705-016-9771-4 - Mota JCA, Alves CVO, Freire AG, Assis Júnior RN. Uni and multivariate analyses of soil physical quality indicators of a Cambisol from Apodi Plateau - CE, Brazil. Soil and Tillage Research. 2014; 140: 66-73. doi: https://doi.org/10.1016/j.still.2014.02.004
» https://doi.org/10.1016/j.still.2014.02.004 - Neves LVMW, Fracetto FJC, Fracetto GGM, Araújo Filho JC, Araujo JKS, Santos JCB, et al. Microbial abundance and C and N stocks in tropical degraded Planosols from semi-arid northeastern Brazil. Catena [Internet]. 2021; 196(May 2020): 104931. doi: https://doi.org/10.1016/j.catena.2020.104931
» https://doi.org/10.1016/j.catena.2020.104931 - Oliveira Filho JS, Pinheiro Junior CR, Pereira MG, Valladares GS, Camara R. Sodification and solodization processes: Pedogenesis or natural soil degradation? Journal of South American Earth Sciences. 2020;104(June): 102909. doi: https://doi.org/10.1016/j.jsames.2020.102909
» https://doi.org/10.1016/j.jsames.2020.102909 - Oliveira ML, Santos CAC, Oliveira G, Perez-Marin AM, Santos CAG. Effects of human-induced land degradation on water and carbon fluxes in two different Brazilian dryland soil covers. Science of Total Environment [Internet]. 2021;792:148458. doi: https://doi.org/10.1016/j.scitotenv.2021.148458
» https://doi.org/10.1016/j.scitotenv.2021.148458 - Pezarico CR, Vitorino ACT, Mercante FM, Daniel O. Indicadores de qualidade do solo em sistemas agroflorestais. Revista de Ciências Agrárias -Amazonian Journal of Agricultural Environmental Sciences. 2013;56(1):40-7. doi: http://dx.doi.org/10.4322/rca.2013.004
» http://dx.doi.org/10.4322/rca.2013.004 - Rizzini CT, editor. Tratado de fitogeografia do Brasil. 2ª. ed. Rio de Janeiro: Âmbito Cultural Edições; 1997. ISBN: 9788586742200.
- Santos JCB, Le Pera E, Souza Júnior VS, Corrêa MM, Azevedo AC. Gneiss saprolite weathering and soil genesis along an east-west regolith sequence (NE Brazil). Catena [Internet]. 2017;150(October):279–90. doi: http://dx.doi.org/10.1016/j.catena.2016.11.031
» http://dx.doi.org/10.1016/j.catena.2016.11.031 - Santos JCB, Le Pera E, Souza Júnior VS de, Oliveira CS, Juilleret J, Corrêa MM, et al. Porosity and genesis of clay in gneiss saprolites: The relevance of saprolithology to whole regolith pedology. Geoderma [Internet]. 2018;319(August 2017):1–13. doi: https://doi.org/10.1016/j.geoderma.2017.12.031
» https://doi.org/10.1016/j.geoderma.2017.12.031 - Santos RD, Lemos RC, Santos HG, Ker JC, Anjos LHC, Shimizu SH. Manual de descrição e coleta de solo no campo. 7. ed. rev. ampl. Viçosa, MG: Sociedade Brasileira de Ciência do Solo; 2015.
- Santos TO, Cury Fracetto FJ, Souza Júnior VS, Araújo Filho JC, Lira Junior MA, Mendes Júnior JP, et al. Carbon and nitrogen stocks and microbial indicators in tropical semi-arid degraded Luvisols. Catena. 2022; 210:105885. doi: https://doi.org/10.1016/j.catena.2021.105885
» https://doi.org/10.1016/j.catena.2021.105885 - Schoeneberger PJ, Wysocki DA, Benham EC, Soil Survey Staff. Field book for describing and sampling soils, Version 3.0. Lincoln: Natural Resources Conservation Service, National Soil Survey Center; 2012.
- Silva PF, Lima JRS, Antonino ACD, Souza R, Souza ES, Silva JRI, et al. Seasonal patterns of carbon dioxide, water and energy fluxes over the Caatinga and grassland in the semi-arid region of Brazil. Journal of Arid Environment. 2017; 147: 71–82. doi: https://doi.org/doi:10.1016/j.jaridenv.2017.09.003
» https://doi.org/doi:10.1016/j.jaridenv.2017.09.003 - Silva IR, Mendonça ES. Acidez do solo e sua correção. In: Novais RF, Alvarez VVH, Barros NF, Fontes RLF, Cantarutti RB, Neves JCL, editors. Fertilidade do Solo. Viçosa: Sociedade Brasileira de Ciência do Solo; 2007. p. 206-374. ISBN: 9788586504082
- Silva RF, Tomazi M, Pezarico CR, Aquino AM, Mercante FM. Macrofauna invertebrada edáfica em cultivo de mandioca sob sistemas de cobertura do solo. Pesquisa Agropecuária Brasileira. 2007;42(6):865–71. doi: https://doi.org/10.1590/s0100-204x2007000600014
» https://doi.org/10.1590/s0100-204x2007000600014 - Silva TGF, Queiroz MG, Zolnier S, Souza LSB, Souza CAA, Moura MSB, et al. Soil properties and microclimate of two predominant landscapes in the Brazilian semi-arid region: Comparison between a seasonally dry tropical forest and a deforested area. Soil &Tillage Research. 2021; 207(October 2020): 104852. doi: https://doi.org/10.1016/j.still.2020.104852
» https://doi.org/10.1016/j.still.2020.104852 - Sobral LF, Barreto MCV, Silva AJ da, Anjos JL dos. Guia Prático para Interpretação de Resultados de Análises de Solo. Embrapa Tabuleiros Costeiros-Documentos (INFOTECA-E). 2015;13.
- Superintendência de Desenvolvimento do Nordeste - SUDENE. Delimitação do semiárido. 2017 [cited 2022 apr 07]. Available from: http://antigo.sudene.gov.br/delimitacao-do-semi-arido
» http://antigo.sudene.gov.br/delimitacao-do-semi-arido - Teixeira PC, Donagemma GK, Fontana A, Teixeira WG, editors. Manual de Métodos de Análise de Solo. Brasília: 3. Embrapa Solos, 2017. ISBN 9788570357717.
- Vance ED, Brookes PC, Jenkinson DS. An extraction method for measuring soil microbial biomass C. Soil Biology and Biochemistry. 1987; 19(6):703–7. doi: https://doi.org/10.1016/0038-0717(87)90052-6
» https://doi.org/10.1016/0038-0717(87)90052-6 - Yeomans JC, Bremner JM. A rapid and precise method for routine determination of organic carbon in soil. Communications in Soil Science Plant Analysis. 1988;19(13):1467–76. doi: https://doi.org/10.1080/00103628809368027
» https://doi.org/10.1080/00103628809368027
Publication Dates
-
Publication in this collection
23 Jan 2023 -
Date of issue
2023
History
-
Received
03 May 2022 -
Accepted
14 Oct 2022