Changes in Soil C, N, and P Concentrations and Stocks after Caatinga Natural Regeneration of Degraded Pasture Areas in the Brazilian Semiarid Region

Abstract

The conversion of caatinga vegetation areas into pastures in the Brazilian semiarid region has depleted soil fertility due to degradation. The natural regeneration of the caatinga has been the alternative adopted to restore soil fertility. However, the real effectiveness of this practice in recovering organic carbon (SOC) and nutrient stocks is unknown. This work evaluated the effect of natural regeneration of the caatinga vegetation on the restoration of levels and stocks of SOC, N, and P as a strategy to maintain the sustainability of the environment. We collected soil samples every 5 cm, up to 20 cm deep, in areas of degraded pasture, caatinga in regeneration (10 years), and regenerated caatinga (35 years) to evaluate the levels and stocks of SOC, N, and P. The depth significantly affects the levels and stocks of SOC, N, and P. Stocks and levels of SOC, N, and P were higher in regenerated caatinga > regenerating caatinga > degraded pasture. The regenerated caatinga increased SOC, N, and P stocks by 115%, 110%, and 117%, respectively, compared to the degraded pasture. Although 35 years of regeneration of the caatinga has improved soil fertility, the levels and stocks of SOC, N, and P remain low.

1. Introduction

Arid and semiarid landscapes represent 45% of the Earth’s surface [1], and in these areas, dry forests are crucial for providing important ecosystem services locally and globally [2]. The native vegetation is an essential regulator of climate, biodiversity, biogeochemical cycles, and the soil’s physical, chemical, and biological properties. Additionally, native vegetation acts as a sink for greenhouse gases [3,4]. However, most dry forest areas have been converted into human-modified landscapes [5].

In Brazil, the caatinga dry forest has enormous endemic biodiversity and is considered one of the dry forests with the most incredible biodiversity around the globe, containing more than 4000 plant species [6,7,8,9]. Despite this, the caatinga has been severely devastated due to its replacement by pasture areas, which has led to severe environmental problems such as loss of biodiversity and desertification [8,10,11,12,13]. Overgrazing is one of the practices that has the most degraded soils in the Brazilian semiarid region. Soil compaction caused by excessive animal trampling leads to the loss of organic matter by increasing soil erosion, which directly affects microbial communities, as well as the availability of nutrients in the soil, and an increase in greenhouse gas emissions [14,15,16,17].

The concentrations and stocks of soil organic carbon (SOC), nitrogen (N), and phosphorus (P) in Brazilian semiarid soils are strongly controlled by the rates of addition and removal of organic matter, which is significantly affected by the management adopted. SOC plays a vital role in several soil properties (physical, chemical, and biological), as well as nitrogen and phosphorus, which are essential for the nutrition of native vegetation. Thus, according to [18], understanding the effects caused by changes in land use on the concentrations of these elements becomes important since efforts have been made to identify soil management systems that favor their increases and/or maintain their concentrations in order to create strategies for soil management that reduce the impact of agriculture on the environment.

Brazilian semiarid soils are generally poor in organic matter [19]. The conversion of caatinga into degraded pasture areas drastically reduces carbon stocks and nutrient concentrations such as N and P, resulting in the loss of fertility and productive potential of Brazilian semiarid soils [20]. After degradation, these areas are generally abandoned and left fallow. In this context, it is reasonable to expect that the caatinga natural regeneration tends to increase litter deposition, and, as a consequence, both SOC and nutrient concentrations and stocks will increase as a result of litter decomposition. Therefore, restoring soil fertility and increasing organic matter and nutrient levels is crucial to maintaining environmental sustainability.

Reforestation and natural regeneration are essential plant restoration strategies used in the caatinga. These ecological restoration strategies effectively sequester SOC and soil nutrients, restore degraded ecosystems, and improve soil quality [21]. However, caatinga’s natural regeneration occurs slowly due to the loss of organic matter and nutrients in the soil and water scarcity. Thus, there is a wide range of information about the effects of natural regeneration of the caatinga on SOC and soil nutrients. This study aimed to verify the effects of caatinga natural regeneration over a degraded pasture on restoring the concentrations and stocks of SOC, N, and P in representative soils of the Brazilian semiarid region as a strategy to maintain their sustainability.

2. Materials and Methods

2.1. Study Area

The research was conducted at Fazenda Lagoinha (Figure 1), located in the municipality of Serra Talhada, in the microregion of Vale do Pajeú, in the hinterland of Pernambuco—a state located in northeastern Brazil. According to the Köppen classification system, the climate is BShw semiarid, hot and dry, with precipitation occurring between December and May. The highest precipitation values are observed in March with an annual average of 642 mm [22].

Currently, the study area consists of the following sub-areas: an area with caatinga vegetation in the regeneration stage—the fallow area (Figure 1A), an area with regenerated caatinga vegetation (Figure 1B), and an area of degraded pasture (Figure 1C). An aerial satellite image of the study area from Google Satellite is shown in Figure 1. The degraded pasture area presents exposed soil with clear signs of erosion. The soil is compacted due to excessive animal trampling, and no plant cover exists. The area with caatinga in regeneration (fallow area) has caatinga vegetation under natural regeneration of intermediate size (10 years in regeneration). In this area, arboreal plants with a maximum height of 1.5 m and plants with large spacing between them dominate. The area with regenerated caatinga vegetation has the predominance of angico (Anadenanthera colubrina (Vell.) Brenan) in tree-shrub form, with 35 years from fallow until regeneration (Figure 1B). In this area, the plants are shrubby, measuring over 3 m, and there is reasonable ground cover, with good litter deposition on the soil surface.

According to the Brazilian Soil Classification System [23] (Figure 2), the predominant soils in the study area are Luvisol in degraded pasture and regenerated caatinga areas (Figure 2A,B) and Leptosol in the area of caatinga in regeneration (Figure 2C), which are shallow and have a low degree of weathering.

2.2. Soil Sampling

This study evaluated the concentrations and stocks of SOC, N, and P in the top 20 cm layer because this layer is more sensitive to changes in land use compared to deeper layers [24]. Soil samples were collected from three different land use conditions: degraded pasture, regenerating caatinga (fallow area), and regenerated caatinga. The samples were gathered using a sampling grid with 10 × 10 m equidistant points in a 50 × 50 m area (Figure 3). In each area studied, soil samples were taken at four depth layers: 0–5, 5–10, 10–15, and 15–20 cm. There were 36 sampling points at each depth, resulting in 144 soil samples for each area (432 soil samples in total). The soil sampler was inserted into the topsoil at a 20 cm depth during soil sampling. The equipment was then retired from the soil, and the collected soil was split into the studied layers—0–5, 5–10, 10–15, and 15–20 cm (Figure 2). The sampling grids were set up under the same topographic conditions in all three areas.

2.3. Chemical and Physical Properties Analysis

To evaluate the chemical attributes of the soils (

Table 1. Chemical and physical attributes of soils in the study areas.

Study Area	pH	Ca2+	Mg2+	Na+	K+	CEC 1	CS 2	TS 3	Silt	Clay
		________________ cmolc kg−1 ________________					______________ % _____________
Degraded pasture	6.78	16.38	4.99	0.44	0.41	22.22	38.8	20.8	21.8	18.6
Caatinga in regeneration	6.95	15.33	2.91	0.28	0.39	18.91	43.2	20.6	18.8	17.4
Regenerated caatinga	6.48	11.96	1.81	0.31	0.41	14.48	50.2	22.2	17.4	10.2

¹ CEC—Cation Exchange Capacity; ² CS—Coarse Sand; ³ TS—Thin Sand.

), we measured the pH in water (1:2.5). The exchangeable cations—Ca²⁺, Mg²⁺, Na⁺ e K⁺, were extracted with 1 mol L⁻¹ ammonium acetate solution, with Ca²⁺ and Mg²⁺ determined by atomic absorption spectrophotometry and Na⁺ and K⁺ by flame emission photometry. The cation exchange capacity was determined by the sodium acetate and ammonium acetate 1 mol L⁻¹ method [25].

We determined the SOC concentration using the Walkley–Black method adapted by Mendonça and Matos [26]. We weighed 0.5 g of the soil sieved through a 0.5 mesh sieve and added 10 mL of potassium dichromate (K₂Cr₂O₇), 0.167 mol L⁻¹, and 20 mL of concentrated sulfuric acid. After 30 min of rest, 200 mL of distilled water, 10 mL of concentrated H₃PO₄, and 1 mL of 0.16% diphenylamine were added. The excess dichromate that was not reduced in the reaction was determined by volumetric titration using ammonium ferrous sulfate [Fe(NH₄)₂(SO₄)₂6H₂O)].

Available P was extracted using the methodology of Olsen et al. [27] and measured by colorimetry. For this purpose, we added 20 mL of a 0.5 mol L⁻¹ NaHCO₃ solution (pH 8.5) to 1 g of soil. After stirring, 5 mL of the extract was filtered, and 10 mL of diluted ammonium molybdate solution and powdered ascorbic acid were added. After color development, the P concentration was measured by colorimetry.

Total nitrogen was measured according to the Embrapa method [28]. Total nitrogen was quantified by sulfuric acid digestion, boric acid distillation, and sodium hydroxide titration. In the physical characterization, the granulometric composition was determined [28] for textural comparison of the areas and to verify the influence of texture on the organic carbon concentrations of the study areas.

2.4. SOC, P and N Stocks

SOC, N, and P stocks were calculated separately for each soil layer studied in the three areas and expressed on an area basis, as described by Carvalho et al. [29], using the equation:

X Stock = (X_i × BD × H)/10,

where X represents the stock of SOC, N, or P in the studied layer (Mg ha⁻¹); X_i is the SOC, N, or P concentration (g kg⁻¹) in the study layer; BD is the soil density in the studied layer (kg dm⁻³); and H is the thickness of the layer considered (cm).

Don et al. [30] emphasized the crucial need to correct carbon stock calculations due to variations in soil density following land use changes. Therefore, the stocks of SOC, N, and P were subsequently corrected for an equivalent soil mass in both study areas, according to Ellert and Bettany [31]:

X_c Stock = X × (BD_ref/BD),

where X_c Stock is the carbon stock run in the layer; X is the uncorrected carbon stock of the layer of interest; BD_ref is the soil density of the layer in the reference area (regenerated caatinga); BD is the soil density in the layer of the area of interest.

Finally, the corrected carbon stock was meticulously calculated for the entire surface layer (0–20 cm) by summing the corrected carbon stock of each layer for each area separately.

2.5. Statistical Analysis

The data underwent ANOVA analysis, followed by a comparison of means using the Tukey test (p < 0.05) to assess differences in concentrations between the studied areas and depths. Additionally, correlation analysis was conducted using the Pearson method.

3. Results

Soil analysis data from the study areas revealed that, in general, pH values were similar (Table 1). The soils presented high exchangeable cations Ca²⁺, Mg²⁺, and K⁺ concentrations. However, the soil of the regenerated caatinga had a lower cation exchange capacity value than the other soils due to the higher content of the sand fraction found in this area’s soil. This characteristic of being more sandy makes the soil of the regenerated caatinga more physically and chemically different from the soils of the degraded pasture and caatinga in regeneration.

3.1. SOC, P, and N Concentrations as Influenced by Different Depths and Caatinga Natural Regeneration

The depth significantly influences (p < 0.05) the SOC, P, and N concentrations in the studied areas (Figure 4, Figure 5 and Figure 6). In all areas, the SOC, P, and N concentrations were higher on the surface and significantly reduced in the subsurface. In the degraded pasture area (Figure 4), the highest SOC concentration observed was 12.1 g kg⁻¹ (0–5 cm), and the lowest one was 5.6 g kg⁻¹ (15–20 cm), and this means that in degraded pasture areas, SOC concentrations are reduced by approximately 54% from the surface to 20 cm deep. In the regenerating caatinga area (Figure 4), SOC concentrations varied from 20.4 g kg⁻¹ (0–5 cm) to 9.5 g kg⁻¹ (15–20 cm), implying percentage reductions of approximately 52% of surface up to 20 cm deep. In the regenerated caatinga (Figure 4), the surface SOC concentration was 29.3 g kg⁻¹ (0–5 cm), while the lowest value observed was 10.8 g kg⁻¹ (15–20 cm), representing reductions of approximately 63% in SOC concentrations from the surface to a 20 cm depth.

Regarding phosphorus (P) concentrations in the degraded pasture area, the highest observed concentration was 20.06 mg kg⁻¹ in the surface layer (0–5 cm), while the lowest was 6.99 mg kg⁻¹ in the 15–20 cm depth layer, indicating a reduction of approximately 65% in P concentration from the surface to the subsurface (Figure 5). In the regenerating caatinga area, P concentrations ranged from 45.64 mg kg⁻¹ (0–5 cm) to 15.62 mg kg⁻¹ (15–20 cm), corresponding to a decrease of about 66% down to a depth of 20 cm (Figure 5). In the regenerated caatinga (Figure 5), P concentration varied from 54.69 mg kg⁻¹ (0–5 cm) to 18.06 mg kg⁻¹ (15–20 cm), reflecting a reduction of approximately 67%.

In the degraded pasture area, N concentrations showed a significant reduction, with the highest concentration found at 0.107 g kg⁻¹ (0–5 cm) and the lowest at 0.05 g kg⁻¹ (15–20 cm), indicating a decrease of approximately 53% from the surface to 20 cm depth (Figure 6). Similarly, in the regenerating caatinga area, N concentration also decreased significantly, ranging from 0.179 g kg⁻¹ (0–5 cm) to 0.08 g kg⁻¹ (15–20 cm), representing a reduction of about 55% over the same depth range (Figure 6). In the regenerated caatinga, the reduction in N concentration was even more pronounced, with a decrease of around 63% from the surface to a depth of 20 cm, where the highest concentration observed was 0.247 g kg⁻¹ (0–5 cm), and the lowest was 0. 09 g kg⁻¹ (15–20 cm) (Figure 6).

The data indicates that natural regeneration of the caatinga significantly (p < 0.05) improves soil fertility. The SOC, P, and N concentrations were higher in the regenerated caatinga compared to the regenerating caatinga and degraded pasture. SOC concentrations varied from 2.93 (in the 0–5 cm layer of the regenerated caatinga) to 0.56 dag kg⁻¹ (in the 15–20 cm layer of the degraded pasture) (Figure 4). Compared to degraded pasture, SOC concentrations increased by 66 and 140% in the 0–5 cm layer of the regenerating and regenerated caatinga areas, respectively. In the 5–10 cm layer, SOC concentration gains were 59 and 107% for the regenerating caatinga and regenerated caatinga areas, respectively. For the 10–15 cm layer, the increases in SOC concentrations of regenerating caatinga and regenerated caatinga, about degraded pasture, were 55 and 98%, while for the 15–20 cm layer, the SOC concentration gains were 69 and 92%, respectively.

The phosphorus (P) concentrations varied across the study areas (Figure 5), ranging from 54.7 mg kg⁻¹ in the regenerated caatinga (0–5 cm) to 6.9 mg kg⁻¹ in the degraded pasture (15–20 cm). The data from this study suggest that P concentrations are positively influenced (p < 0.05) by caatinga regeneration. At the 0–5 cm layer, there were increases of 127% and 172% in P concentrations compared to degraded pasture in the regenerating and regenerated caatinga areas, respectively. In the 5–10 cm layer, the increases in P concentrations were 93% and 61% in the regenerating and regenerated caatinga areas, respectively. In the 10–15 cm layer, only the regenerating caatinga showed significant increases in P concentrations, with a gain of 71% compared to the degraded pasture. However, at 15–20 cm, both regenerating and regenerated caatinga areas showed significant increases in P concentration—123% and 158%, respectively, compared to the degraded pasture area.

The N concentrations varied between the study areas, ranging from 0.247 mg kg⁻¹ in the regenerated caatinga (0–5 cm) to 0.04 mg kg⁻¹ in the degraded pasture (15–20 cm) (Figure 6). Caatinga regeneration significantly (p < 0.05) increased the N concentrations compared to degraded pasture. The results show that the increases in N concentration were as follows: 69% and 133% (0–5 cm), 67% and 108% (5–10 cm), 60% and 100% (10–15 cm), and 72% and 100% (15–20 cm) for the regenerating caatinga and regenerated caatinga, respectively.

3.2. SOC, P and N Stocks

Comparisons of SOC, P, and N stocks in a degraded pasture x regenerating caatinga (10 years in regeneration) x regenerated caatinga (35 years from fallow until regeneration) are of immense value as they enrich our understanding of the dynamics of these stocks across various ecological areas. In general, the caatinga regeneration significantly (p < 0.05) increased SOC, N, and P stocks (Figure 7). The SOC, N, and P stocks supported these findings, with higher concentrations observed in regenerated caatinga > regenerating caatinga > degraded pasture. Specifically, the SOC stocks increased significantly by 64% and 115% compared to degraded pasture in the regenerating and regenerated caatinga areas, respectively (Figure 7).

While N stocks did not differ significantly between regenerating caatinga and degraded pasture, the regenerated caatinga exhibited a substantial increase of approximately 110% compared to degraded pasture (Figure 7). On the other hand, P stocks showed no significant difference between regenerating and regenerated caatinga (Figure 7). This suggests that caatinga is more effective in recovering P stocks compared to N or SOC. Specifically, P stocks increased by 109% and 117% in regenerating and regenerated caatinga, respectively, relative to degraded pasture.

4. Discussion

Our results revealed that soil anthropization drastically reduces SOC, P, and N concentrations. We observed a greater accumulation of these elements on the topsoil (0–5 cm), which is expected due to the soil surface being the layer with greater deposition and accumulation of litter [32], as also reported by [18]. These findings are consistent with those reported by Gava et al. [20], who also found higher concentrations of SOC, N, and P in the surface layer (0–5 cm) under different land use conditions in the Brazilian semiarid region. Since no fertilizers are applied in the study areas, the N and P distribution patterns in the soil align with the results for SOC. This suggests that the dynamics of N and P in Brazilian semiarid soils, under conditions of natural regeneration of the caatinga, are similar to that of SOC since organic matter is the only source of nutrients in the soils of these areas.

After forest regeneration, SOC and soil nutrient rates depend on climate, land use conditions, previous land use, soil clay content, type and density of vegetation cover, and sampling depth [24]. In our study, it was possible to verify the contribution of the natural regeneration of the caatinga on the SOC, P, and N concentrations, which resulted in the improvement of the natural fertility of semiarid soils through the reestablishment of vegetation cover. The higher accumulation of SOC, P, and N in the regenerated caatinga area compared to other areas is due to the increased vegetation, which contributes more organic matter to the soil. The contribution of plant residues to the soil surface promotes slow and gradual decomposition, ensuring continuous incorporation of organic material into the soil. The trend of increasing soil organic matter over time is consistent with the effects of reforestation and forest succession on soil organic matter accumulation.

The lower concentrations of SOC, P, and N observed in this study in degraded pasture areas occur mainly due to the removal of vegetation cover, which results in a low production of litter, reducing the supply of organic matter to the soil surface. In many cases, the limited amount of litter produced is consumed by animals as food, leaving the soil surface unprotected. The lack of soil cover, combined with excessive trampling, leads to soil compaction and increased susceptibility to water erosion, especially during heavy rainfall in the rainy season [33,34]. Consistent with our findings, Almeida et al. [10] conducted a 10-year comparison study between degraded pasture and regenerating caatinga areas, observing reduced soil erosion and organic carbon losses in the regenerating caatinga. They also noted higher nutrient concentrations in the regenerating caatinga, with increases of 75% for nitrogen, 73% for phosphorus, and 34% for potassium.

The SOC, P, and N concentrations positively correlate with the clay content (

Table 2. Correlation coefficients for organic carbon, P, and N concentrations with chemical and physical attributes verified in the study areas.

	pH	Ca2+	Mg2+	Na+	K+	TS 2	CS 3	Silt	Clay
SOC 1	−0.24	−0.51	−0.94	−0.55	−0.53	0.45	0.98	−0.99 *	0.93 *
P	0.15	−0.13	−0.99 *	−0.83 *	−0.44	0.69	0.82	−0.94 *	0.72 *
N	−0.19	−0.46	−0.96	−0.59	−0.11	0.40	0.96	−0.99 *	0.91 *

¹ SOC—Organic Carbon; ² TS—Thin Sand; ³ CS—Coarse Sand. * Significant at p < 0.05.

), so the more clay there is, the higher the concentrations of these elements in the soil. Conversely, the higher the silt content, the lower the SOC, P, and N concentrations due to their negative correlation with these nutrients. Additionally, the P concentration was negatively correlated with Mg²⁺ and Na⁺ concentrations (Table 2).

Clay is responsible for stabilizing colloidal or humic compounds in soil organic matter due to the adsorption process, providing protection due to the high specific surface area involved and the strong interaction between organic and inorganic colloids, which results in the formation of aggregates such as protection and the presence of stable organomineral complexes [35,36], which explains the positive correlation between clay and soil organic carbon concentration. Although the degraded pasture area had a higher clay content, the silt, the Mg²⁺, and Na⁺ concentrations were also higher than in the other areas (Table 1), and this also contributed strongly to the reductions in SOC, and consequently, the P and N concentrations, as their levels depend on soil organic matter, their main source.

On the other hand, the soil of the regenerated caatinga, classified as Leptosol, contained a higher percentage of sand than the soils of the degraded pasture and regenerating caatinga—Luvisols (Table 1). This area is dominated by Angico vegetation (Anadenanthera colubrina (Vell.) Brenan), which helps to understand the greater stocks of SOC and N accumulated in this soil. Angico is a legume species; therefore, the higher richness of legume species implies higher amounts of N-fixing microorganisms, which contributes to the higher stock of N in this soil [34]. Furthermore, as the caatinga vegetation on this soil is denser and consists of larger trees, the greater supply of litter compared to other areas contributes to the greater stock of SOC.

The conversion of degraded areas into forests reestablishes nutrient cycling. Perennial land cover in native and regenerating forests provides greater and constant deposition of litter, which can contribute to the maintenance of soil moisture and lower soil surface temperatures, which can increase carbon stocks, phosphorus, and nitrogen in the topsoil [37]. Our study found that caatinga regeneration was more effective in recovering P stocks since, in 10 years of forest regeneration, P stocks did not differ from the regenerated caatinga. However, this was not the case for SOC and N, where 10 years of caatinga regeneration was insufficient to raise SOC and N stocks to the same level as in the 25-year-old regenerated caatinga. These findings suggest that for elements with low levels in Brazilian semiarid soils, such as phosphorus in our study, caatinga regeneration can restore the element’s stocks in a shorter period than elements that are naturally more abundant in semiarid soils.

It is important to note that even with the caatinga regenerated (25 years regenerated), the SOC, N, and P stocks were low compared to other biomes. For example, Azevedo et al. [38] found SOC stocks of 136.68 Mg ha⁻¹ for the Atlantic Forest, representing a SOC stock three times higher than in this study. Villela et al. [39] found N stocks varying from 0.98 to 1.86 Mg ha⁻¹. Also, these values were much higher for the Atlantic Forest than those verified in our study for N stocks. Thus, the data verified in this study indicate that the slow caatinga regeneration, as it is a dry forest, makes it difficult to reestablish soil nutrients. This occurs due to climatic conditions characterized by low rainfall and high temperatures, which limit plant growth and biomass production, leading to reduced litter deposition and, consequently, a decreased supply of nutrients to the soil. Althoff et al. [40] suggested that SOC recovery in deforested caatinga areas may take up to 60 years to reach the original levels of dense vegetation before deforestation. Additionally, Araújo Filho et al. [41] indicated that in caatinga areas, the average time for SOC to return to its initial value in the soil is approximately 65 years. Like SOC, in our study, P and N followed the same tendency to return to the soil as the vegetation establishment time after deforestation.

The assessment of SOC, N, and P stocks in Brazilian semiarid soils is also essential to provide insights into soil health, as microbial activity in soils is limited by the availability of SOC, N, and P [42], which are easily altered by land use. Medeiros et al. [43] suggested that native and restored forests receive more significant inputs of C and N, stimulating greater enzymatic activities related to N and P. Also, Costa [44] found that the conversion of forest to pasture significantly alters the soil bacterial community. This implies that actions need to be taken to prevent deforestation of the caatinga, support reforestation efforts, and therefore preserve and recover SOC and nutrients in the soil. Such actions should include financial compensation for local producers who rely on income generated by livestock production for their subsistence to avoid deforestation of the caatinga.

5. Conclusions

The findings of this study highlight the importance of revegetating the caatinga to enhance and restore the natural soil fertility in the semiarid region of Brazil, particularly in the topsoil. Our research showed a significant increase in SOC, P, and N concentrations and stocks due to natural caatinga regeneration compared to degraded pasture, emphasizing the importance of this technique to restore soil fertility and contribute to the sustainability of the Brazilian semiarid soils. Our data also revealed that nutrient concentrations and stocks remained relatively low even after 35 years of caatinga regeneration.

For nutrients with deficient concentrations in Brazilian semiarid soils, such as those found for P in this study, a shorter regeneration time in the caatinga is sufficient to recover their concentrations and stocks. Given the caatinga’s slow growth, we suggest additional research to explore methods to enhance its growth and establishment, thereby accelerating the restoration of SOC and soil nutrients and ensuring the soil’s sustainability.