Attili, D. S. 1 *; Tauk-Tornisielo S.M. 2

1Fundação Tropical de Pesquisas e Tecnologia "André Tosello", CP 1889, 13087-010, Campinas, SP, Brazil and 2CEA-UNESP, CP 199, 13506-900, Rio Claro, SP, Brazil.

* Present address: ESALQ-USP, CP 83, 13400-970, Piracicaba, SP, Brazil



Surface soil of three different parcels of an area in the Ecological Reserve of Juréia-Itatins, SP, Brazil, was sampled to determine colony-forming units of filamentous fungi, soil moisture and pH, organic matter, carbon and nitrogen contents (%), phosphorus (m g/cm3), potassium, calcium and magnesium contents (meq/100 cm3), sum of bases (meq/100 cm3), potential acidity (meq/100 cm3), cation exchange capacity (meq/100 cm3) and base saturation (V%). The area was studied for the first time and the parcels investigated were located next to each other but progressively distant from the black-water Una River, in order to verify likely influences of this distribution. The analysis of variance and Pearson correlation coefficient showed evidences of a high relationship between organic matter and soil moisture content; a lower level of base cations than acidic cations in the area; higher concentrations of nutrients in the parcel furthest from the river, and a positive correlation of the numbers of colony-forming units with the elements in parcel tree. A hypothetical outline of the nutrient distribution in the studied area is proposed.

Key words: correlation, organic soil, fungi filamentous, soil ecology, tropical rain forest.



Organic soils are a small portion of the world's land area but are widely distributed. They are formed when the production of organic matter exceeds its mineralization, usually under conditions of almost cetontinuous saturation with water, reducing circulation of oxygen through the soil (5). Peat bogs, for instance, are low pH environments that have complex organic constituents which degrade more slowly than they accumulate. The rate and extent of degradation of these substances vary and depend mainly on the existance of favourable conditions for the activity of the soil biota community (13). For the classification of histosols it is necessary to quantitatively evaluate the degree of the decomposition of their organic matter. Besides the ecological aspect, their importance also relies on the fact that bodies of histosols have been, in many areas, sources of fuel (5).


The Atlantic tropical rain forest is one of the most important ecosystems in the world and comprises diverse and complex environments (12), nevertheless only 5% of the original cover still remains in Brazil. In the state of São Paulo, a well-preserved area where scientific studies are nearly pioneer, can be found in the valley of the Ribeira de Iguape river. The Ecological Reserve of Juréia-Itatins (ERJI), SP, presents many types of plant formations which are thought to be the result of diverse substrates, since they are all under the same climatic conditions. More than twenty years ago, some natives of the ERJI cultivated rice in areas next to the Una river which crosses the region. Soil nutrients may be influenced by topography, parent material, disturbances and drainage (5). Studying physico-chemical characteristics of lowlands in the Valey of Ribeira de Iguape river, authors (4), found different distribution patterns along the riverbed in non-disturbed areas. This work brings information on high organic content soil in the Atlantic rain forest that was disturbed in the past, comparing parcels of distinct distances from the Una river. The influence of the drainage and the correlation among physico-chemical parameters and number of colony forming units of filamentous fungi are also studied aiming the characterization of the site.


Study site

The ERJI is an area of 79.245ha Atlantic rain forest created in 1986 and located in the State of São Paulo, Brazil, between 24° 18’47"-24° 36’10" S and 47° 00’03" - 47° 30’07" W (Figure 1). Main climatic characteristics are: mean air temperatures between 15-35° C, high relative air humidity (80-100%); annual rain fall average above 3,400mm, and a less-rainy season during autumn-winter (3). A great variety of vegetation is found as part of the mangroves, lowland forests, luxuriant rain forest, mountains and elevations (7). The collecting place is known as "Banhado Grande", in the middle of the Reserve; in the area chosen for this study the soil tends to peat formation and it is classified as histosol hemist (5). The site was characterized as a secondary forest exposed to floods, with predominance of Tibouchina (Melastomataceae), Psychotria (Rubiaceae), Richeria australis and Alchornea triplinervea (Euphorbiaceae), Rudgea villiflora (Rubiaceae), Becquerelia muricata (Cyperaceae) and Calathea sp. (Marantaceae) (Sobral, 1994, pers. commun.).

Figure 1. Localization of the Ecological Reserve of Juréia-Itatins, SP, Brazil.

Soil sampling

From October 1990 to January 1992 surface soil was trimonthly sampled. The 3ha. study site was established from the left edge of the river towards the mountains. It was subdivided in 3 parcels of the same size as follows: parcel 1, 100m away from the river; parcel 2, 200m; parcel 3, 300m. Using sterile plastic bags, three soil samples composed of 10 subsamples were collected from each parcel (9 samples in total), up to the depth of 10cm after removing the forest floor. They were labeled and homogenized. The amount used for fungal quantification was immediately processed and the remaining soil was sent to the Soil Department of the Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba, where it was analysed in five days.

Soil analysis

To determine the colony-forming units, dilution plate counts on cellulose agar, Czapek and Fries-cellulose modified media (9) at 28° C for 72h were used. Ten subsamples of soil were dried at 105°C to constant weight in order to determine moisture content. The results of the percentage (w/w) of water in the soil were based on the fresh weight divided by dry weight (11). Soil pH was measured in 0.01M CaCl2 with a glass electrode.

Organic carbon was determined in 0.25g of soil using the Walkley-Black method. Soil organic matter and N were defined by elemental calculations. Concentrations of extractable P were determined with a mixture of IR-120 and IRA-400 resins in a spectrophotometer. The ions K+, Ca+2 and Mg+2 were extracted by an ion-exchange resin procedure (after a 16-hour shaking period) and separated from soil with an acidic solution of sodium chloride; determination was by atomic absorption spectrophotometry. The values of percentage base saturation, cation exchange capacity and sum of bases were calculated. The potential acidity was evaluated in the pH suspension comparing the readings with a standard curve between pH values in SMP buffer and those of potential acidity determined in soils by the calcium acetate method (18).

Statistical analysis

Data were log transformed when appropriate to meet the assumptions for analysis of variance (ANOVA) (21). The average of the parameters were compared to determine the heterogenicity of the study site. The Tukey test was used


when differences were significative. The analysis was performed using SAS 6.04. SYSTAT 5.01 was chosen to calculate Pearson correlation coeficients and define relationships among colony-forming units of filamentous fungi, soil moisture and pH, organic matter, carbon and nitrogen contents (%), phosphorus (µg/cm3), potassium, calcium and magnesium contents (meq/100cm3), base cations (meq/100cm3), potential acidity (meq/100cm3), cation exchange capacity (meq/100cm3) and base saturation (V%).


In general, the results showed a significative increase on the concentration of the parameters analysed, from the distance of the river (Table 1). Lower values were found in parcel 1 and higher ones in parcel 3, both statistically different from parcel 2. This situation was observed in the following parameters: colony forming untis (1,63.103 CFU x 10,32.103 CFU); moisture content (42,56% x 74,10%); organic matter (6,37% x 21,83%); organic carbon content (3,70% x 12,69%) and total nitrogen content (0,32% x 1,09%). Parcels 1 and 2 were similar in other parameters, both significatively different from parcel 3 where higher concentrations were detected. These results were found in the following analysis: extractable phosphorus content (12µg Pcm-3 in parcel 2 x 39,33µg Pcm-3 ); exchangeable potassium (0,11meq100cm-3 in parcel 1 x 0,33meq100cm-3); calcium content (0,17meq100cm-3 in parcels 1 and 2 x 0,80meq 100cm-3); magnesium concentration (0,20meq 100cm-3 in parcels 1 and 2 x 0,63meq 100 cm-3); sum of bases (0,60meq100cm-3 in parcels 1 and 2 x 1,57meq100cm-3) and CEC (11,57meq100cm-3 in parcel 1 x 34,73meq100cm-3). Parcel 3 also presented maximum and minimum values of two parameters: potential acidity (10,87meq100cm-3 in May 1991 and 33,8meq100cm-3 in October 1991) and base saturation (2,67% in October 1991 and 12% in May 1991). The pH of all parcels varied between 3,07 and 4,03 and were found to be indicative of an acidic soil. No statistical differences were detected among the parcels, but measurements of first and last samplings were statistically different. Results of correlation analysis are in Table 2. Correlations not significative at 5% at least were ommited. Figure 2 presents a hypothetical distribution of the parameters studied in the sampling site.

Table 1. Number of colony forming units of filamentous fungi, chemical and physico-chemical parameters of the organic soil in the ERJI, SP, Brazil, analysed between Oct.1990-Jan.1992.

Figure 2. Hypothetical outline of the nutrient distribution in the studied area. Legend: P = extractable phosphorus; o.m. = organic matter; CFU = colony forming units of filamentous fungi; CEC = cation exchange capacity; BS = base saturation; V = sum of bases.

The moisture of the soil studied was very high (42,5-74,1%), probably due to the total rainfall that occurs along the year in the Atlantic Rain Forest, where the pluviometric balance is always positive (3). Soil moisture fluctuations in the ERJI were even higher than other regions with similar type of vegetation where values ranged between 50-60% for two years (20). In savannah-like areas this percentage is much lower, around 7-17% (19). The correlation analysis of Pearson coeficient made it possible to highlight the importance of the water present in the soil through many positive correlations found in almost all parameters: organic matter, carbon, nitrogen, potential acidity, calcium, magnesium, potassium, base saturation, sum of the bases, CEC, extractable phosphorus and colony forming units of filamentous fungi, Table 2. This kind of correlation is already known because the water and the other parameters mentioned are strictly related (21,17). In all cases it is assumed that a higher moisture content favoured the concentration of the cations. The soil potential acidity is formed by the dissociation of H+ and Al+3, which is influenced by the water content. Besides this fact, higher values of these parameters resulted in an increase of the number of filamentous fungi, which usually counts for the fertility of any type of soil.

Table 2. Correlation analysis for : potencial acidity (acidity); base saturation (BS); carbon (C); nitrogen (N); organic matter (o. m.); pH; cation exchange capacity (CEC); calcium (Ca+2); magnesium (Mg+2); potassium (K+); sum of bases (V); extractable phosphorus (P); soil moisture (moisture) and colony forming units of filamentous fungi (CFU). Significant correlations are marked with (**) = 1% and (*) = 5%; (+) = positive correlation and (-) = negative correlation; a = correlations .

Typical of organic soils is the heavy discharge of organic acids during the decomposition process. This situation leads to low pH measurements, as detected in the sampling field. In this study the pH was positively correlated with the base saturation and was negative to the potential acidity and CEC. In theory, when the acidity of the soil is neutralized, a gradual decrease of the alluminium and hidrogen is observed, resulting in lower levels of potential acidity and higher values of pH. Since CEC represents the sum of the bases plus H++Al+3, it decreases as well, and then we have the negative correlation. The relation between base saturation (sum of cations/CEC) and the pH of the soil is very intense, so if a decrease of the CEC occurs it is likely that the base saturation should increase and establishe a positive correlation with the pH (17).

Measurements of organic matter (6,4-21,8%), total carbon (3,7-12,7%) and nitrogen (0,3-1,1%), confirmed the status of the soil studied as organic. The predominance of carbon content compared to the nitrogen is due to the chemical composition of the plants (17).

The high positive correlation (1%) found among these parameters and also similar correlations with other analysis (potencial acidity, CEC, calcium, magnesium, potassium, sum of bases, phosphorus and CFU of filamentous fungi) underlines their close relationship. This fact may be explained because it is already known that C and N exist in soil due to the decomposition of the organic matter (17), or as a consequence of the analytical methods used for the determinations favouring them to express the same fluctuations. Organic debris contribute to the nutritional condition of the soil, releasing or keeping nutrients due to its high CEC (4,17). Soil moisture is related to the percentage of cellulose and hemicellulose found in the parental organic layer which increases 4 to 6 times its capacity to retain water (10). In that manner, the organic matter is considered one of the main factors to establish the number of microorganisms in the soil (17); its high correlation with sum of bases and potential acidity in other sites nearby the ERJI was also known (4).

The values of P concentrations measured in the study area were considered intermediate to low, Table 1. Despite its low rate of leaching, the lack of this nutrient in tropical and subtropical soils had already been mentioned (15); nevertheless, the wide variation that phosphorus may be present in the soil makes its concentrations range from almost zero to 3.000µg/g, depending on the parental matter (17). All correlations determined between P and other parameters were positive: base saturation, sum of bases, potassium and magnesium, Table 2, which may be a result of their proportional release from the organic matter.

As observed for the great majority of the parameters studied, the levels of K+ were also higher in parcel 3, but even so the measurements of 0,11-0,33meq100cm-3 were found low to intermediate compared with other soils in the State of São Paulo (17). Its positive correlations with base saturation, sum of bases, calcium and magnesium are widely reported in the literature ( 15,17).

In the study area, concentrations of Ca+2 (0,17-0,80meq100cm-3) and Mg+2 (0,20-0,63meq 100 cm-3) were found to be very low (Lepsch, 1997, personnal comm.), and as a consequence, the sum of bases. Soil analysis of another area of Atlantic Rain Forest, for instance, resulted in 1,90meq Ca+2 100cm-3 (20). In the process of retation and cation exchange, Ca+2 is followed by Mg+2 and because of that the level of the later is usually lower (16), as observed in this work.

In general, cation concentrations were considered low in the soil of the studied field. It has been observed that some plants respond with a better growth to a favourable association of cations that leads to a good sum than to their values individually (Sparovek, 1994, personnal comm.). Potential acidity and CEC were positively correlated with the sum of bases.

The correlations among potential acidity, sum of bases and magnesium suggest a proportional realease from the organic matter, making the CEC higher. In the association H+ + Al+3, aluminium is the only exchangeable cation. When a smaller part of CEC is formed by basic cations (17), then the soil becomes more acidic (CEC= SB + H+ + Al+3) but an increase of the aluminium results an increase of CEC too.

The parameter pH has a strong influence on the cation exchange capacity of the organic matter. When pH is higher, ions H+ are dissociated and free to combain with hidroxils to make water, other cations replace H+, increasing the CEC of the parental material (10). CEC values of 8 different areas in the State of São Paulo varied from 3,2 to 28,9meq100cm-3 and the organic matter from 0,6 to 4,5% (17). Since in the organic soil of the ERJI base cation concentrations were low it is assumed that the levels of 11,6-34,7meq CEC 100cm-3 were due to the exchangeable Al+3 highly present in the potential acidity (10,9-33,8meq 100cm-3).

This study detected a negative correlation between base saturation and potential acidity, as previously observed by other authors in the Ribeira River Valley, located in the surroundings of ERJI (Berg et al., 1987). Forest soils seem likely to present this kind of correlation since there are not practicals of soil corrections as happens in soils used for cultivation. (Sparovek, 1994, personnal comm.). Base saturation (Ca+2 + Mg+2 + Na+ + K+/ CEC), is considered a very important parameter to evaluate the fertility of a soil (16,17).

During a study of lowlands, authors (4), concluded that areas closer to the river presented higher levels of base saturation, lower potential acidity and a gradual increase of organic matter and carbon further the edge; the great complexity of this kind of environment was highlighted. The 3ha area delimited in this investigation was heterogeneous, and parcel 3, farther from the river had higher levels of moisture content, organic matter and its components. The distance may influence these parameters because the closest parcels are subjected to a stronger drainage, leaching the nutrients more intensively. On the other hand, moisture content increases in parcel 3 due to a lesser draining. Base cations may be concentrated in the canopy. Similarities between the Atlantic Rain Forest and Amazonian Forest had already been observed (Lepsch, 1997, personnal comm.).

Parcels 1 and 3 were always statistically different, parcel 2 seemed to behave as a transitory area, suggesting that major changes occur between distances of 200m. The calculations also showed standard deviations relatively wide, indicating that there must be microsites in the studied area.

The diversity of elements that contribute to the formation of soils result in differences that determine the development of the microbial communities (2), which in response also influence the characteristics of the soil. Nearly half of the volume of the soil is composed by pores fulfilled with air and water, essencial for the survival of microorganisms; the other half is occupied by nutrients also important for the microbial biomass (1).

The methodology employed for the analysis of the organic soil in the ERJI was considered appropriate for this study, despite its simplicity. It was possible to detect significative differences among the areas and their influences on the number of colony forming units of filamentous. The literature suggests that more refined methods to analyse forest soils are still being developed. The organic matter content, C, N, K+ and soil moisture were correlated with the CFU


which presented higher numbers in parcel 3, where the concentration of the majority of the elements was more elevated. However, it is assumed that the high water content in the soil did not favour the fungal decomposition of the organic matter as evidenced by its high content yet to be decomposed. These microrganisms develop well in conditions of 60-70% of soil moisture, but are also aerobic and so more efficient in the presence of O2 which they use as eletron receptors (14,22).


The moisture content of the soil directly influenced the increase of the organic matter, and this favoured the retention of water in the place. The organic matter of the organic soil in the ERJI is poor in bases and rich in acidic cations influencing the low pH found. Increasing levels of the parameters studied were observed from the distance of the river, with statistical differences between 200m, revealing a higher number of colony forming units of filamentous fungi. As mentioned before, the studied area was a field of rice cultivation 20 years ago, and has been recovering since then. It is known that after removing the original vegetation of a forest there is an interruption of the natural balance of the soil properties, which can be restablished along the years, although in a different way from the original condition (8). The hypothetical outline of the parameters in the studied area proposed in Figure 2 shows the present situation of this site. It is assumed that despite the parcel, the content of water in the soil was high, in general, with a hard influence on most nutrients. Base cations must probably be concentrated in the canopy of the secondary forest as reported in the Amazonian forest and a lower pH may be a result of the high potential acidity and the organic acids liberated during the decomposition process.


DSA thanks the Conselho Nacional de Pesquisa e Desenvolvimento - CNPq, Brasília, for the award of a senior research grant, Dr. Fausto Campos Pires and team, from the Environmental Secretary of the State of São Paulo, for the assistance to reach the study area ; Dr. Igo Lepsch, University of Uberlândia, MG and Dr. Gerd Sparovek, ESALQ, Piracicaba, for their suggestions and the researcher Marcos G. Sobral from the University of Rio Grande do Sul, RS for the botanical characterization of the study site.



Análises e estudos das correlações do solo orgânico na Estação Ecológica da Juréia-Itatins, Estado de São Paulo. Amostras de solo da superfície de três parcelas determinadas em uma área da Estação Ecológica de Juréia-Itatins, SP, Brasil, foram submetidas às seguintes análises: unidades formadoras de colônias de fungos filamentosos, umidade, pH, matéria orgânica, nitrogênio total, carbono (%), fósforo (µg/cm3), potássio, cálcio e magnésio (meq/100cm3), soma das bases (meq/100cm3), acidez potencial (meq/100cm3), capacidade de troca catiônica (meq/100cm3) e saturação das bases (V%). As três parcelas investigadas localizaram-se progressivamente distantes das águas negras do rio Una do Prelado no intuito de verificar os efeitos desta distribuição. As análises de variância e o coeficiente de correlação de Pearson mostraram: 1. alta relação entre o teor de matéria orgânica do solo e a umidade do mesmo; 2. menores níveis de cátions básicos em relação aos ácidos; 3. maiores concentrações de nutrientes na parcela mais distante do rio, e , 4. uma correlação positiva com o número de unidades formadoras de


fungos filamentosos com o aumento de nutrientes na parcela 3. Propõe-se um esquema hipotético da distribuição destes elementos na área.

Palavras-chave: correlação, ecologia do solo, floresta tropical, fungos filamentosos, solo orgânico.



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