ABSTRACT
Purpose: The aim of this study was to investigate how soil bacterial abundance relates to soil C, N and P contents along land use change gradient in the Cerrado landscape.
Method/design/approach: Land use categories were classified according to the succession stage of natural vegetation and agricultural activity. Soil physicochemical analyzes and plate counts of cellulolytic, amylolytic, free-living diazotrophic, phosphate solubilizing and actinobacteria were carried out. Linear regression analysis was used to investigate the interaction between the abundance of bacterial cultivable groups and soil C, N and P contents. Redundancy analysis (RDA) was used to determine the influence of environmental variables. Land use change affected how bacterial cultivable abundance interacts to soil C, N and P dynamics.
Results and conclusion: The regression analysis revealed 27 significant interactions between bacterial cultivable abundance (BCA) and soil C, N and P contents. In general, the increase of BCA is related to higher soil C, N and P rates. The influence of BCA in soil nutrient cycling seems to be more expressive in stressful environments such as intermediate succession area and agricultural lands. Nitrogen was the most affected nutrient and actinobacteria are the microbial group that can most enhance soil fertility. RDA showed that K, Mg and Ca contents were the main environmental factors acting on bacterial abundance.
Research implications: Conservation of natural resources and maintenance of biodiversity.
Originality/value: Soil bacterial functional groups and actinobacteria are directly involved in biogeochemical cycling being key factors for ecosystem conservation.
Keywords: Conservation, Semiarid, Ecosystem, Fertility, Bacteria.
RESUMO
Objetivo: O objetivo deste estudo foi investigar como a abundância bacteriana do solo se relaciona com o conteúdo do solo C, N e P ao longo do gradiente de alteração do uso do solo na paisagem do Cerrado.
Método/concepção/abordagem: As categorias de uso do solo foram classificadas de acordo com a fase de sucessão da vegetação natural e da atividade agrícola. Foram realizadas análises físico-químicas do solo e contagem de placas de celulolíticos, amilolíticos, diazotróficos de vida livre, solubilizantes de fosfato e actinobactérias. A análise de regressão linear foi utilizada para investigar a interação entre a abundância de grupos bacterianos cultiváveis e os teores de C, N e P do solo. A análise de redundância (RDA) foi utilizada para determinar a influência de variáveis ambientais. A mudança no uso da terra afetou como a abundância cultivável bacteriana interage com a dinâmica C, N e P do solo.
Resultados e conclusão: A análise de regressão revelou 27 interações significativas entre a abundância cultivável bacteriana (BCA) e os teores de C, N e P do solo. Em geral, o aumento do BCA está relacionado às taxas mais elevadas de C, N e P do solo. A influência do BCA no ciclo de nutrientes do solo parece ser mais expressiva em ambientes estressantes, como área de sucessão intermediária e terras agrícolas. O nitrogênio foi o nutriente mais afetado e as actinobactérias são o grupo microbiano que pode melhorar a fertilidade do solo. A RDA mostrou que os teores de K, Mg e Ca eram os principais fatores ambientais que atuavam sobre a abundância bacteriana.
Implicações da investigação: Conservação dos recursos naturais e manutenção da biodiversidade.
Originalidade/valor: Os grupos funcionais bacterianos do solo e as actinobactérias estão diretamente envolvidos no ciclo biogeoquímico, sendo fatores-chave para a conservação do ecossistema.
Palavras-chave: Conservação, Semiárido, Ecossistema, Fertilidade, Bactérias.
1 INTRODUCTION
Brazil harbors vast biological diversity, making it a priority for conservation programs. The country features large areas of remnant vegetation covering about 60% of its land in various ecosystems including tropical forests, deciduous forests, swamps, savannas and grasslands (Colli et al., 2020). However, tropical forests are under severe threat from deforestation for agriculture. Human activity's pressure on these natural ecosystems has increased, with land use and climate change being among the greatest current threats to biodiversity. The negative effects of land use change and climate change are predicted to be concentrated in tropical grassland and savanna regions (Venter et al., 2016; Newbold, 2018).
One of the most endangered tropical savannas globally is the Brazilian Cerrado, occupying over 200 million acres in central Brazil. In recent decades, approximately 50% of this biome has already been converted to different land uses (Santos et al., 2021). Land use change transforms the natural landscape through human activities. In the Brazilian Cerrado in recent decades, this has resulted in loss of natural vegetation, making it more vulnerable to degradation. Consequently, there were modifications to the soil microbiota, altering nutrient flows and interfering with biogeochemical processes (Grecchi et al., 2014; Bandeira et al., 2023).
Developing sustainable land management strategies to reduce soil degradation and biodiversity loss is a current need to preserve this biome. Understanding how land use changes affect relationships between microorganisms and soil fertility is essential. Fertility refers to the soil's fitness supporting optimal plant growth, effectively indicating soil quality through changes in physical, chemical and biological properties. There is no standard for soil fertility and fitness since diverse plants require varied optimal growth conditions related to edaphic factors including microbial activity (Muñoz-Rojas et al. 2016).
Microorganisms can be used as sensitive indicators of soil quality and are usually regarded as bioindicators as they reflect the properties and biological processes within the soil that indicate the state of this ecosystem. Several microbial parameters such as microbial biomass, respiration, metabolic quotient, community profiles, diversity and abundance have potential for use as soil quality diagnostic indicators and are widely used to discern different soil types and management (Muñoz-Rojas et al. 2016; Cavalcante et al., 2023).
The soil microbial community provides potential indicators for environmental monitoring, in terms of presence/absence, abundance, activity, morphology, physiology or behavior, in response to stresses or disturbances. Integrating chemical, physical and biological parameters improves understanding of biogeochemical processes fundamental for developing sustainable practices (Bunneman et al., 2018).
Bacterial functional groups comprising microbial guilds closely involved in biogeochemical processes are associated with soil enzymatic activity and C, N and P cycling functions. These are directly linked to nutrient limitation resulting from land use changes (Escalas et ak, 2019; Cavalcante et ak, 2023).
Edaphic factors like pH, texture, organic matter, nutrient availability and environmental factors such as seasonality, vegetation type, ecological succession stage and temperature importantly alter the abundance and composition of microbial communities in soil (Naylor et ak, 2020; Ezeokoli et ak, 2020; Cunha et ak, 2023).
While the effects of land use change and environmental factors on microbial community structure are widely discussed, the relationship between specific microbial community abundance and soil nutrient contents is poorly understood. This study examines how bacterial functional groups relate to soil fertility, addressing scenarios of ecosystem vulnerability versus sustainability.
We hypothesize increasing soil nutrient contents increases the abundance of cultivable bacterial groups, while land use change alters organic matter inputs into soil, causing resource limitation in disturbed ecosystems.
The objective was investigating how cellulolytic, amylolytic, free-living diazotrophic, phosphate-solubilizing bacteria and actinobacteria abundance relates to soil C, N and P contents across a land use gradient. Furthermore, identifying the environmental variables most influencing this relationship and addressing which bacterial group best relates to soil fertility.
2 METHODS
2.1 Study site
The study was carried out in the Sete Cidades [Seven Cities] National Park - SCNP and surrounding area (10 Km buffer zone) which is located in the state of Piaui - Brazil, between coordinates -04.03555, -041.67916. The SCNP was created by Federal Decree No. 50.744 on June 8th, 1961.
The regional climate is subhumid with a mean annual temperature of 26.5°C, reaching a maximum of 28.1°C in October and a minimum of 25.5°C in June. Mean annual precipitation is approximately 1560 mm, based on 1998-2018 data from a weather station 30 km from the conservation unit (INMET, 2018).
The region's vegetation comprises a complex mosaic dominated by savanna formations (Coutinho, 1978; Mantovani et al., 2017), generally associated with Arenosols and Planosols. Local relief features a pediplan surface with altitudes varying from 100 to 300 m, including isolated conical and tabular rock formations (Jacomine et al., 1986).
2.2 Soil sampling
Soil samples were collected inside and outside the Conservation Unit (CU) according to the land use classification (Table 1). In total, 28 soil samples were collected. Sampling was carried out from 05/15/2018 to 06/01/2018 (late rainy season) and soil was collected in a 10 cm depth. The experimental design and sampling details were previously described by Bandeira et al. 2023.
2.3 Soil physicochemical and microbiological analysis
Soil physicochemical analyzes were carried out according to the methodologies described by (Teixeira et al. 2017). The following parameters were evaluated: pH, soil organic carbon (SOC), total nitrogen, total phosphorus and texture.
Bacterial cultivable abundance (BCA) was estimated by plate count method (spread plate) and the following functional groups were essayed: amylolytic bacteria, cellulolytic bacteria, free-living diazotrophic bacteria and phosphate solubilizing bacteria, based on their relation to soil C, N and P dynamics. Cultivable actinobacteria were also essayed. Counting procedures were performed in triplicate and with three replications.
Ten grams (10 g) of soil sample was dispersed in 90 mL of sterile saline solution (0.85%) and subsequently shaken for 30 min at 150 rpm for homogenization. Serial dilutions were made ( 1 O'2 - 1 O'6), followed by inoculation of 0.1 mL of each dilution in selective culture media. Microbiological standard nystatin solution (100,000 lU/mL) was used in the media to prevent the growth of fungi, naturally present in the soil samples. All count results were expressed in Colony Forming Units (CFU) per gram of soil and transformed into loglO (Log CFU. g'1).
Phosphate solubilizing bacteria were counted using Pikovskaya agar (PVK) with pH adjusted to 7.0 (±0.2) and the addition of bromophenol blue dye (Gadagi & Sa, 2002). The inoculated plates were incubated at 28°C (±2) for seven days. Cellulolytic bacteria were counted using cellulose agar medium modified with Congo red dye (CCRA) according to Hendricks et al. (1995). Incubation took place for seven days at 28 °C (± 2). After this period, cellulolytic bacteria were detected by clear zone around the colonies that was revealed using a NaCl (2M) solution.
Burk's culture medium was used to quantify free-living diazotrophic bacteria. The pH of the medium was adjusted to 7.0 (± 0.2). After inoculation, the plates were incubated for seven days at 28°C (± 2) (Park et al. 2005). For the quantification of amylolytic bacteria, the minimal agar medium was used with the addition of starch (2%) (Cappuccino; Sherman 1996). Actinobacteria abundance was determined on casein-dextrose-agar (CDA) medium as described by Arifuzzaman et al. (2010). Plates were incubated for seven days at 28°C (± 2).
2.4 Data analysis
Soil physicochemical and bacterial cultivable abundance data were first assessed for normality and homogeneity of variance using Shapiro-Wilk and Levene's tests, respectively. One-way ANOVA followed by Tukey's post-hoc test was used to determine statistically significant differences between groups (p<0.05). Linear regression analysis was then performed, relating soil C, N and P contents to the abundance of each bacterial group. Redundancy analysis (RDA) identified the influence of measured environmental variables on bacterial abundances (p<0.05) (Gomez et al. 2006; Legendre & Legendre, 2012). ANOVA, regression analysis and post-hoc tests were conducted in IBM SPSS Statistics 20. RDA ordination plots were generated using PAST 2.13.
3 RESULTS AND DISCUSSION
The results of soil chemical analysis and bacterial cultivable abundances were previously presented by Bandeira et al., 2023. For this study the data were adapted as shown in Table 2.
Regression analysis revealed 27 significant interactions out of 60 total. These results indicate effects of vegetation successional stage and soil management on bacterial cultivable abundances, as related to soil C, N, and P contents. Pearson's correlation coefficients ranged from -0.512 to 0.697, suggesting each bacterial group uniquely interacts with soil nutrients across land use categories (Figure 1).
3.1 Protected and conserved area
Plots inside the conservation unit showed three significant associations. Soil nitrogen interacted only with actinobacteria, while soil phosphorus associated with actinobacteria and phosphate solubilizers. No groups exhibited linear relationships with soil organic carbon.
Actinobacteria obtained the highest coefficient of determination (r2) with soil phosphorus, explaining up to 26.2% of variance. Phosphate solubilizers also affected soil phosphorus, accounting for 24% of variation. The actinobacteria-soil nitrogen relationship accounted for 13%.
As actinobacteria abundance rises, soil nitrogen increases. However, higher actinobacteria and phosphate solubilizer populations associate with lower soil phosphorus, indicating negative interactions. In the conserved area, four significant interactions occurred, contrasting the protected zone. Soil phosphorus lacked associations, yet cellulolytic and phosphate solubilizing bacteria positively interacted with soil organic carbon. Both groups also presumably influence nitrogen dynamics here.
For the conserved area, phosphate solubilizers showed the highest r2 with soil organic carbon, estimating 12.4% and 6.7% of variance is explained by fluctuating abundances of phosphate solubilizers and cellulolytic bacteria, respectively.
3.2 Secondary Area
The secondary area showed the most associations between soil C, N, P and bacterial cultivable abundance, with only two non-significant interactions (p>0.05) - amylolytics and phosphate solubilizers bacteria with soil phosphorus.
Actinobacteria obtained this study's highest r2 with soil organic carbon. Their abundance variation accounts for 48.6% of SOC rate variation, representing the group most influencing soil fertility. Meanwhile, phosphate solubilizers showed the lowest SOC association (r2 = 0.072). All groups positively associated with SOC linearly.
Notably, all functional groups significantly related to SOC in the secondary area. Regression analysis estimates increasing these groups' abundances favors carbon levels, especially actinobacteria and amylolytics.
Nitrogen associations varied - diazotrophic bacteria most affected N variation, contributing 36.1%. Amylolytics showed the lowest relationship (r2 = 0.087).
Soil phosphorus links were less pronounced than for nitrogen and SOC. Diazotrophs, cellulolytic bacteria, and actinobacteria significantly interacted, suggesting their proliferation associates with greater total soil phosphorus.
3.3 Agriculture Area
Cultivated plots showed seven significant associations between soil C, N, P and bacterial abundance, four related to nitrogen. Only amylolytics significantly interacted with soil organic carbon, accounting for 22.6% of variance. Nitrogen appears most impacted by bacterial abundances here, with positive relationships between diazotrophs, amylolytics, actinobacteria and phosphate solubilizers.
As in the secondary area, diazotrophs, amylolytics, cellulolytic bacteria and phosphate solubilizers associated significantly with soil nitrogen. However, phosphate solubilizers exhibited a negative relationship.
Soil phosphorus linked significantly to amylolytic and cellulolytic bacteria, with cellulolytics showing the highest r2 value (0.396). Overall, bacterial cultivable abundance increased soil C, N and P under cultivation.
In summary, the secondary area revealed the greatest significant interactions between abundance and soil nutrients, implying microbiota most influences fertility status. Diazotrophs and amylolytics only associated significantly in two land use types.
Uniquely, phosphate solubilizers showed consistent associations with soil C, N and P across all categories, denoting a close fertility relationship. Result variability also reflects the study site's physiographic heterogeneity demonstrated through soil property standard deviations among land uses (Table 2).
3.4 Redundancy multivariate analysis.
Redundancy analysis (RDA) verified the influence of environmental variables on bacterial group abundance, complementing the regression analyses. In Figure 2, points represent individual plots with land use categories differentiated by color. The estimated model indicates soil chemical variables explain up to 68.3% of variation in bacterial abundances across plots.
Environmental variables positively intercorrelate, pointing in the same direction. Potassium, calcium and magnesium contents exerted the greatest effects on abundance. Conversely, soil organic carbon and electrical conductivity showed the least influence. Substantial dispersion of points between the X and ¥ axes reveals considerable variation in soil chemical and biological parameters among plots.
4 DISCUSSIONS
Bacterial cultivable abundance variably relates to soil fertility across land uses. Differing edaphic factors, vegetation succession stages, and agricultural activity likely explain some of this variability (Cline & Zak, 2015; Araujo et al. 2017; Heng et al. 2016).
In the linear regression analyses, r2 values remained below 0.85, so estimated models cannot predict outcomes. Some cases showed r2 scores below 0.100, suggesting slight bacterial influence on fertility. However, valid variable relationships still exist (Favero 2015). Given the complexity of soil nutrient cycling, discrete contributions by specific bacterial groups are expected. Furthermore, culturable bacteria constitute only a small soil community fraction. Various uncultured groups like denitrifiers, nitrifiers, fungi, and ammonifiers also drive nutrient transformations (Matsumoto et al. 2005; Burke et al. 2012).
The protected and conserved areas at advanced succession harbor more similar edaphic properties and vegetation, likely hosting comparable bacterial communities. Here, associations between abundance and C, N and P proved less significant versus secondary and agricultural zones. This implies vegetation importantly impacts functional microbiota characteristics during succession through litter biochemistry changes (Matsumoto et al. 2005; Cline & Zak, 2015). Thus, cover changes from succession should alter microbial community structure/function.
Higher root densities likely increase plant-microbe nutrient competition in protected/conserved plots (Schenk, 2006), evident in the negative phosphorus-abundance relationship suggesting limitation.
Thirteen of 27 total significant associations occurred in secondary forest, highlighting microbiota's substantial soil fertility role here (Figure 1). Early succession favors oligotrophs with few nutrients, while copiotrophs increase through litter deposition as succession progresses (Zeng et al. 2017).
Oligotrophic microorganisms thrive in nutrient-limited conditions, playing greater roles in soil processes (Hernandez & Lizarazo, 2015). Secondary and agricultural areas likely host more oligotrophs, given the higher significant abundance associations with soil C, N and P variations (13 and 7 of 27 total, respectively, representing 74%). This agrees with lower measured nutrient availability in these land uses (Table 2).
Alternatively, copiotrophs strongly depend on nutrient availability, with carbon favoring survival (Ramin & Allison, 2019). This potentially explains the weaker bacterial influence on fertility in the carbon/nitrogen-rich protected and conserved plots.
Agricultural land results indicate human activity impacts abundance-fertility interactions. As Szoboszlay et al. (2017) and Heng et al. (2016) found, differing litter inputs and vegetation affect agricultural and forest soil structure and nutrient quality, selecting for distinct microbial community composition and functionality.
Diazotrophs only significantly associated with fertility in secondary and agricultural zones. Land use change consequences on diazotrophic communities likely stem from plant community shifts (Mirza et al., 2014).
In protected/conserved forests, sufficient nitrogen from litter cycling reduces diazotroph demand. However, their nitrogen contributions become essential where depletion occurs, as in agriculture and secondary zones, to meet plant growth requirements (Norby & Iversen, 2006).
Our diazotrophic bacteria findings agree with Bomfim et al. (2019), showing land use and succession impact associations with soil nutrients. As Matsumoto et al. (2005) found, substrate quality further influences diazotrophic dynamics. Plant-modulated litter inputs driving microbial function in natural systems supports this.
Likewise, amylolytics only significantly linked to C, N and P in secondary and agricultural areas. Extracellular enzyme production reflects environmental conditions (Gorlachlira & Coutinho, 2007; Burns et al. 2013; Luo et al. 2017). With limited resources, hydrolytic enzyme secretion provides a competitive advantage (Fontaine et al. 2003).
Litter-rich environments contain abundant labile organic matter, favoring copiotrophic r-strategists that proliferate then strongly rely on this resource. With organic matter limitations, recalcitrant/stab le components accumulate, promoting к-strategist oligotrophs specialized in extracellular enzyme production to access nutrients (Fontaine et al. 2003; Pascault et al. 2013; Cline & Zak 2015).
Accordingly, secondary and agricultural areas showed the lowest soil organic carbon. Microbes likely adopt competitive enzymatic strategies expanding substrate utilization (Fontaine et al. 2003; Pascault et al. 2013; Cline & Zak 2015). High temperatures also induce extracellular enzyme secretion. Sandy soils further constrain retention, causing nutrient limitations.
The Cerrado encompasses varied physiognomies from grasslands to forests (Santos et al., 2021). Intermediate secondary vegetation includes spaced grasses, shrubs and small trees (Coutinho, 1978), yielding exposed soils facing radiation, heat, and moisture loss. This promotes functional groups producing extracellular enzymes like cellulolytics, amylolytics and actinobacteria (Table 2), also explaining their soil nutrient associations.
While agricultural activity should exert greater microbial stress (Zhang et al. 2016), abundance data did not reflect this. Less acidic pH from calcium/magnesium amendments that facilitate stress relief potentially explains this trend, as redundancy analysis emphasized their influence on distribution. Such bases commonly correct cultivated soil acidity (Wang et al., 2021).
Cellulolytics and actinobacteria significantly associated with fertility across land uses (Figure 1). As for amylolytics, they access nutrients via extracellular enzymes (Ramin & Allison, 2019). However, amylolytics lacked protected/conserved area relationships, likely because of narrow substrate specificity. Cellulolytic bacteria presented a significant association to soil C and N contents in the protected and conserved areas. Cellulose is the main substrate of this microbial group and makes up the most abundant part of the litter biomass (Pramanik & Kim, 2014), that is characteristic of advanced succession stage areas and justifies the interactions of this group in a greater range of land use classes compared to amylolytics. It is worth emphasizing the versatility of these microorganisms in secreting hydrolytic enzymes in response to environmental variables such as nutrient availability and abiotic factors, as shown by Berlemont et al. (2014) which reinforces its role in soil fertility also in the secondary and agricultural area.
Actinobacteria significantly associated with soil nutrients across three land uses - advanced/intermediate succession forests and agricultural areas. Their versatility arises from taxonomic, enzymatic and chemical diversity (Barka et al. 2016), plus abiotic stress tolerance (Yadav et al. 2018), underlying ecosystem function importance.
Actinobacteria also showed the highest abundance across categories (Table 2), demonstrating adaption to varied habitats. Agreeing with Araujo et al. (2017) and Castro et al. (2016), the phylum remained abundant constituting 21% of all phyla. Suela Silva et al. (2013) also reported Cerrado soil activity. Their highest r2 scores further indicate actinobacteria most strongly influence fertility.
Phosphate-solubilizing bacteria solubilize unavailable inorganic soil phosphates (Azziz et al. 2012). As discussed, protected/conserved plots likely harbor copiotrophic bacteria (Fontaine et al. 2003; Cline & Zak 2015; Ramin & Allison 2019) that rapidly proliferate given ample carbon. However, growth increases mineral requirements like phosphorus. Solubilization by phosphate-solubilizers provides bioavailable phosphorus that immediately incorporates into biomass, reducing soil contents.
This explains the negative actinobacteria-phosphorus relationship since they also solubilize phosphate (Jog et al. 2014). Through organic acid metabolism, phosphate-solubilizers chelate cation-bound phosphates, generating soluble forms (Chen et al. 2006; Karpagam & Nagalakshmi 2014). Their soil activity depends partly on nutrient availability, clarifying significant protected area phosphorus associations only, which showed the greatest organic carbon levels.
Besides phosphate-solubilizers, arbuscular mycorrhizal fungi actively participate in soil phosphorus cycling (Ferrol et al. 2019), further reducing expectations for strong solubilizer relationships. Agreeing with this, the group accounted for only 24% of variance. Fungal interactions likely drive dynamics in other land uses (Matsumoto et al. 2005; Burke et al. 2012).
A negative nitrogen relationship also occurred, with the group explaining 9.7% of variation. The secondary area showed the lowest soil nitrogen, so solubilizers potentially increased demand by providing phosphorus, since both act as limiting nutrients for nucleic acid/protein production (Raven 2018).
Overall positive abundance-nutrient associations indicate higher bacterial proliferation relates to greater availability. Nitrogen showed the most interactions (12), followed by carbon (8) and phosphorus (7), demonstrating microbial support of fertility.
This study evidenced bacterial functional groups' ecosystem process and ecological implications. Results showcase microbiota's soil fertility role, especially in stressful, resource-limited environments, indicating importance for biodiversity conservation. Outcomes could aid government ecological monitoring and sustainable land management.
5 CONCLUSIONS
Land use change affected how bacterial cultivable abundance interacts to soil C, N and P dynamics. In general, the higher the nutrient contents in the soil, the greater the abundance of the bacterial groups, highlighting the importance of soil microorganisms for nutrient cycling and ecosystem functioning.
A total of 27 significant associations between bacterial abundance and soil C, N and P contents (p<0.05) were obtained of which 3, 4, 13 and 7 were in the protected, conserved, secondary and agriculture plots respectively.
Bacterial cultivable abundance significantly related to soil fertility mostly in stressful environments, such as agricultural and secondary areas, that are characterized by nutrient limitation and abiotic severity which demonstrates the importance of preserving soil biodiversity.
K, Mg and Ca were the main factors acting on the bacterial abundance along the plots. Actinobacteria are the bacterial group that most contribute to soil fertility and nitrogen is the most affected soil nutrient.
ACKNOWLEDGMENTS
The National Council for Scientific and Technological Development and Chico Mendes Biodiversity Conservation Institute (CNPq / ICMBio /FAPs n°18/2017) for supporting this research (Grant Number 421350/2017-2) and CAPES (Financial code 001).
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Abstract
Purpose: The aim of this study was to investigate how soil bacterial abundance relates to soil C, N and P contents along land use change gradient in the Cerrado landscape. Method/design/approach: Land use categories were classified according to the succession stage of natural vegetation and agricultural activity. Soil physicochemical analyzes and plate counts of cellulolytic, amylolytic, free-living diazotrophic, phosphate solubilizing and actinobacteria were carried out. Linear regression analysis was used to investigate the interaction between the abundance of bacterial cultivable groups and soil C, N and P contents. Redundancy analysis (RDA) was used to determine the influence of environmental variables. Land use change affected how bacterial cultivable abundance interacts to soil C, N and P dynamics. Results and conclusion: The regression analysis revealed 27 significant interactions between bacterial cultivable abundance (BCA) and soil C, N and P contents. In general, the increase of BCA is related to higher soil C, N and P rates. The influence of BCA in soil nutrient cycling seems to be more expressive in stressful environments such as intermediate succession area and agricultural lands. Nitrogen was the most affected nutrient and actinobacteria are the microbial group that can most enhance soil fertility. RDA showed that K, Mg and Ca contents were the main environmental factors acting on bacterial abundance. Research implications: Conservation of natural resources and maintenance of biodiversity. Originality/value: Soil bacterial functional groups and actinobacteria are directly involved in biogeochemical cycling being key factors for ecosystem conservation.