FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS IN THE GALIO SYLVATICI-CARPINETUM AND ALNO-ULMION FORESTS**

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1 P O L I S H J O U R N A L O F S O I L S C I E N C E VOL. XLIV/ PL ISSN Soil Chemistry DOROTA KAWA KO, BEATA ABAZ, PAWE JEZIERSKI* FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS IN THE GALIO SYLVATICI-CARPINETUM AND ALNO-ULMION FORESTS** Received July 7, 2011 Abstract: The aim of the study was to analyze the fractional composition of humic compounds in ectohumus O and humus A soil horizons in two forest associations: Galio Sylvatici-Carpinetum and Alno-Ulmion in relation to chosen physical-chemical properties of soils. The following analyses were performed on collected soils samples: texture, ph in 1mol KCl dm -3, exchangeable acidity, organic C, N total, the contents of exchangeable cations of alkaline character (Ca +2, Mg +2, K +, Na + ) and fractional composition of humic compounds using the Tiurin method. River alluvial brown soils were investigated. The soils were characterised by an acidic reaction and a typical distribution of organic matter with maximum content in the accumulative horizon. Fraction Ia (fulvic fraction, consisting of low compound fulvic acids, extracted with 0.05 mol dm -1 H 2 SO 4 ) accounts for a rather insignificant part ( % C total) of humic compounds. Humus is dominated by fraction I (humic compounds bound with calcium and mobile forms of R 2 O 3, extracted with 0.1 mol dm -1 NaOH). This fraction is significantly different and in the range from 9.14 to 49.68% C total; in turn the C HA /C FA ratio has a value between Fraction II (humic compounds bound with the stable silicate forms of R 2 O 3 ) is placed in the range % C total. Non hydrolyzing C constitutes % of C total. River valleys are considered the most valuable and universal ecological passages with matter exchange taking place along them. It has also been emphasized that natural river valleys, due to their special arrangements with regard to geomorphologic and hydrologic aspects, constitute very rich and differentiated habitats for organisms inhabiting the valleys or those moving along them [11]. However, since primeval times, river valleys have been subject to intense *D. Kawa³ko, DSc., B. abaz, DSc., P. Jezierski, DSc.; Institute of Soil Science and Environmental Protection, Wroc³aw University of Environment and Life Sciences, Grunwaldzka 53, Wroc³aw, Poland. **The study was financed by the Ministry of Science and Higher Education, Poland under the project No. N N

2 118 D. KAWA KO et al. management by humans, which has led during the last two centuries to their strong transformation, biological impoverishment, decrease in water retention and increased water run-off [13, 28]. The regulation of rivers causes a significant inhibition of geomorphological processes. The protection of river banks limits the possibility of meandering and old river bed formation. The old river beds formed previously are subject to a gradual shallowing, degradation and successive disappearance. As has been demonstrated in longstanding studies [1, 12, 22, 23] there are significant changes in the physical and chemical properties of soils, which is confirmed by a decrease in biodiversity. The decrease in groundwater levels has caused significant changes in the natural environment resulting in the retreat of a large number of valuable flora and fauna species (including species protected by law and endangered species). One of the most important things in terms of ecology are soil formations located in the area of river valleys and flood terraces of the Galio Sylvatici- Carpinetum and Alno-Ulmion forests. Galio Sylvatici-Carpinetum forests (oakhornbeam-lime) are stable natural communities in a considerable part of their area, and their special feature is their multilayer arrangement. They require fertile, fresh-humid soils; however, they do not require any special irrigation or any outstanding soil fertility. Alno-Ulmion forests (forests formed by ash, grey alder, poplar, willow and elm) occupy fertile soils and exist by dint of periodical, especially early-spring, floods. They are one of the richest forest ecosystems functioning as a natural water absorber and the best protection against floods. The aim of the present work was to determine the fractional composition of humus compounds of soils of the Galio Sylvatici-Carpinetum and Alno-Ulmion forests on the basis of physico-chemical properties. The results presented in the paper are part of a wider study concerning the influence of groundwater surface depths on the properties of soils formed from different bed rocks in selected forest habitats of protected areas in the Lower Silesia region. MATERIAL AND METHODS The study included soils developed from formations of river accumulation situated in the south-west part of the Jerzyca Valley Landscape Park near the village of Dêbno, in the Wo³ów area. After the analysis of cartographic materials and soil-habitat studies, 8 soil profiles were selected. Experimental sites were chosen with regard to the kind of forest community (Central European Galio Sylvatici-Carpinetum and Alno-Ulmion forest) and the distance from the Odra River. Soil samples of a broken structure were collected from all separated genetic horizons, and the following parameters were determined: granulometric composition using the Bouyoucos-Casagrande aerometric-screening method as modified by Prószyñski, organic carbon content on a C Ströhlein CS-Mat 5500

3 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 119 automatic analyzer, total nitrogen content using the Kjeldahl method on a Büchi analyzer, ph of soils in 1 mol KCl dm -3 by the potentiometric method, exchangeable acidity using the Soko³ow method, and the content of changeable base cations using the Pallman method in 1mol CH 3 COONH 4 dm -3 of ph 7. The ions of Mg 2+ in the extract obtained was determined using the ASA method on a Philips PU 9100X apparatus, Ca 2+, Na +, K + ions on a Carl Zeiss (Jena) flame photometer. On the basis of exchangeable acidity and the content of analyzed ions, the cation exchange capacity (CEC) and degree of sorptive complex saturation with bases (BS) were calculated. Fractional composition of humus compounds was analyzed using a modified Tiurin method [10] separating the following groups of humus substances: fraction Ia (fulvic) - substances passing to solution while treating the soil with 0.05 mol H 2 SO 4 dm -3 including low-molecular, more mobile organic connections; fraction I - humic substances separated via multiple soil treatment with 0.1mol NaOH dm -3 including free connections, bound with calcium and non-silicate R 2 O 3 forms; fraction II - humic substances separated during alternating soil treatment with 0.1 mol H 2 SO 4 dm -3 and 0.1 mol NaOH dm -3 including humus substances more strongly bounded with stable silicate R 2 O 3 forms. This fraction was determined only in the mineral levels; fraction III - humic substances separated during direct soil treatment with 0.1 mol H 2 SO -3 dm -3 including humus substances more strongly bounded with non-silicate R 2 O 3 forms; C HA -Ca - humic acids bound with calcium, calculated from the difference of the content of fraction I C FA and fraction III C HA ; non-hydrolyzing C - including so called post extraction residue including non-humificated organic residues in organic levels, while mainly humins and ulmins in mineral levels. This fraction was calculated from the following difference: non-hydrolyzing C = organic C - (C fraction Ia + C fraction I + C fraction II ). Absorbance with wave lengths of 464 and 665 nm was determined in humic acid extracts 10 mg humic acid extracts was dissolved in 50 cm mol NaOH. dm -3 and also the absorbance coefficients A4/6 were calculated. RESULTS AND DISCUSSION Chemical and physico-chemical properties All the analyzed soils belong to alluvial soils [17]. They are characterised by a considerable content of fractions that to a high degree determine their physical, chemical and physico-chemical properties.

4 120 D. KAWA KO et al. Profiles 1-4 were done in a community of Central European Galio Sylvatici- Carpinetum forest, on a site of fresh forest with dominating hornbeam, oak, lime, maple and single spruce and pine. The age of the tree stand was assessed as years. The soil sample sites were situated about 1000 m from the river Odra, and there was no ground water in the profile. The soils were characterised by well formed humus level (mull type bedding), compact texture and the presence of down gley at a depth of cm (Table 1). The soil sample sites 5-8 were done in a moderately humid Alno-Ulmion forest site with a predominance of grey alder, oak aged years, elm and poplar. The profiles were situated at a distance of m from the Odra river bed, in a slightly narrower part of the terrace with a deeper groundwater level. The soil layers up to the depth of 70 cm were strongly overgrown with roots, a layer of drifted material was observed on the surface (mull type bedding) (profiles 6 and 7), and gley signs were seen just at a negligible depth (profiles 6 and 8). These soils were characterised by a lower content of parts < mm compared to river alluvial soils in a Galio Sylvatici-Carpinetum forest (Table 1). The presence of humus is a basic feature allowing soils to be distinguished, and an inflow and accumulation of soil organic matter is an important factor in soil formation and the differentiation of their morphology and properties [1]. In the analyzed soils, the highest content of carbon was observed in organic horizons and was within the range of 13.4% in profile 5 to 32.96% in profile 1 (Table 2). The amount of organic carbon in accumulation horizons ranged from 2.30 % in profile 2 to 14.5 % in profile 6. This parameter tended to decrease with depth increase in almost all the soils. The exception was profiles 6 and 7 where a substantial content of organic carbon was noted in the organic horizon, and next in the layer IIA2 at a depth of 20 cm. When comparing the analyzed soils in both habitats, a higher content of organic carbon in organic horizons of fen soils in Galio Sylvatici- Carpinetum forests can be observed, and a considerably lower amount in mineral horizons when compared to fen soils in Alno-Ulmion forests (Table 2). The obtained results confirm that nitrogen content in particular horizons is closely connected to the content of organic carbon. Also, the high positive correlation between these parameters in the organic horizon (0.96*) confirms this thesis (Table 5). The ratio of C:N in organic levels of the analyzed forest soils was within the range from 21.7 (profiles 4 and 8) to 26.4 (profile 2). In analyzed soils under Galio Sylvatici-Carpinetum forests that ratio was the widest in organic horizons, which illustrates the predominance of the process of organic matter accumulation over its decomposition in those levels [8, 15, 27]. In analyzed soils under Alno-Ulmion forests mineral levels were observed, and the ratio of C:N was wider when compared to organic levels, and this may result from the presence of compounds containing nitrogen in humus, where C:N is slightly narrower than in humic acids.

5 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 121 TABLE 1. TEXTURE OF ANALYZED SOILS Object 1 G S-C 2 G S-C 3 G S-C 4 G S-C 5 A-U 5 A-U Horizon Depth of horizon (cm) Percentage content of fraction (Ø in mm) > <0.002 Name of group A silt loam Bbr silt loam ICg silty clay loam IICg sandy loam IIIC sand Ag silt loam Bbr silt loam Cg silty clay loam IICg loam IIIC sandy loam IVC sand A silt loam Bbr loam Cg loam IICg silt loam IIICg loam IVg silt loam A silt loam Bbr silt loam Cg silt loam IICg loam IICg loam Gox silty clay loam A sandy loam ABbr sandy loam Bbr loam BbrCgg sandy loam Cgg sandy loam A1g silt loam C1g sandy loam IIA loam ABbr loam Bbrgg loam Cgg silt loam

6 122 D. KAWA KO et al. Object 6 A-U 7 A-U 8 A-U Horizon Depth of horizon (cm) TABLE 1. CONTINUATION Percentage content of fraction (Ø in mm) > <0.002 Name of group A1g silt loam C1g sandy loam IIA loam ABbr loam Bbrgg loam Cgg silt loam A silt loam IIA silt loam Bbr silt loam Cgg silt loam A sandy loam Bbrg silt loam BbrCg sand C1gg sand IIC2gg loamy sand G S-C Galio Sylvatici-Carpinetum, A -U Alno-Ulmion. The ph value in KCl in analyzed soils was within the range of 3.4 to 6.0 (Table 2). Thus, these were strongly acidic, acidic and faintly acidic soils characteristic of forest areas. The fen soils under Galio Sylvatici-Carpinetum forests with coniferous species were characterised by lower ph values. The highly acidic reaction of soils was caused by the presence of pine tree stands [5, 16], forming acid products of the decomposition and humification of remains accumulating in horizon A. They infiltrate inside the soil, where the amount of neutralising substances is insufficient, via precipitation [21]. The analyzed soils under Alno-Ulmion forests were characterised by better physicochemical properties when compared to soils under Galio Sylvatici-Carpinetum forests. The sum of base cations in humus horizons of these soils was within the range from 15.0 cmol (+) kg -1 (profile 6) to 23.7 cmol (+) kg -1 (profile 8) (Table 2). To make a comparison, in soils under Galio Sylvatici-Carpinetum forests this value in humus horizons was from 4.51 cmol (+) kg -1 in profile 3 to 12.4 cmol (+) kg -1 in profile 2. The considerably lower exchangeable acidity and high contribution of Ca 2+ ions mean that the degree of sorptive complex saturation with base cations (BS) of analyzed fen soils under Alno-Ulmion forests was high and exceeded 65% (the exception was BbrCgg horizon in profile 5). The soils under Galio Sylvatici-

7 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 123 TABLE 2. CHEMICAL AND PHYSICO-CHEMICAL PROPERTIES OF THE ANALYZED SOILS Object Horizon 1 G S-C* 2 G S-C Depth of horizon (cm) phkcl Organic C (%) Total N ( %) C/N Kw 1 Ca 2+ Mg 2+ K + Na 2+ S 2 CEC 3 BS 4 (cmol(+) kg-1 soil) O no no no no no no no no A Bbr ICg no no IICg no no IIIC no no O no no no no no no no no Ag Bbr Cg no no IICg no no IIIC no no IVC no no (%)

8 124 D. KAWA KO et al. TABLE 2. CONTINUATION Object Horizon 3 G S-C 4 G S-C 5 A-U* Depth of horizon (cm) phkcl Organic C (%) Total N ( %) C/N Kw 1 Ca 2+ Mg 2+ K + Na 2+ S 2 CEC 3 BS 4 (cmol(+) kg-1 soil) O no no no no no no no no A Bbr Cg no no IICg no no IIICg no no IVCg no no O no no no no no no no no A Bbr Cg no no IICg no no IICg no no Gox no no O no no no no no no no no A ABbr Bbr BbrCgg no no Cgg no no (%)

9 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 125 TABLE 2. CONTINUATION Object Horizon 6 A-U 7 A-U 8 A-U Depth of horizon (cm) phkcl Organic C (%) Total N ( %) C/N Kw 1 Ca 2+ Mg 2+ K + Na 2+ S 2 CEC 3 BS 4 (cmol(+) kg-1 soil) O no no no no no no no no A1g C1g no no IIA ABbr Bbrgg Cgg no no O no no no no no no no no A IIA Bbr Cgg no no O no no no no no no no no A Bbrg BbrCg no no IIC1gg no no IIC2gg no no (%) G S-C Galio Sylvatici-Carpinetum, A - U Alno-Ulmion. 1 exchangeable acidity; 2 base cation capacity; 3 cation exchange capacity; 4 base cation saturation; no no analyze.

10 126 D. KAWA KO et al. Carpinetum forests demonstrated a lower degree of base cation saturation (BS) at the level from 30.8 % (horizon A, profile 3) to 88.3 % (horizon Gox, profile 4) (Table 2). In humus horizons A the organic C was positively correlated with the sum of base cations (S) and the degree of sorptive complex saturation with base cations (BS), while negatively with exchangeable acidity (Kw) (Table 3). TABLE 3. COEFFICIENT OF CORRELATIONS BETWEEN FRACTIONAL COMPOSITION OF HUMUS SUBSTANCES AND SELECTED SOIL PROPERTIES OF A HORIZONS Variable C org Nt Kh S BS CEC t <0.002 C org 1.00* * 0.76* 0.79* Fraction Ia -0.78* -0.68* 0.83* * Fraction I - C extr * * -0.72* -0.87* Fraction I - C HA -0.85* * * Fraction II - C extr * * * Fraction II - CHA -0.91* * * Fraction III - C extr * * -0.75* -0.91* Fraction III - CHA -0.73* * -0.72* -0.89* C non-extr. 0.88* * 0.69* 0.86* CHA-Ca IH -0.88* * -0.69* -0.86* A4/A * statistically significant at p < 0.05, Nt total nitrogen, Kh exchangeable acidity, S base cation capacity, BS base cation saturation, CECt -sorption capacity, < mm - clay fraction. Fractional composition of humus compounds Many papers published so far emphasise the influence of moisture conditions on the intensity of mineralization and humification of organic matter that is reflected in the amount and quality of accumulated organic matter. The analysis of the fractional composition of humus compounds allows the transformations of organic matter, processes proceeding in the soil and its genesis to be posited [2, 3, 7, 9, 24-26]. The contribution of particular fractions of humic compounds was analyzed in the ectohumus horizons O and in mineral humus horizons A. Analyzing fractional composition of humus substances it may be noticed that a small contribution was represented by fraction Ia representing low-molecular organic connections easily relocated in the soil profile (Table 4). The contribution of Ia fraction in ectohumus horizons O was within the range of 1.96 to 3.77% C org, while in humus levels A in the range of 1.14 to 7.11 % C org. Fraction Ia in horizons under Galio Sylvatici-Carpinetum forests showed a clear trend of increased

11 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 127 TABLE 4. FRACTIONAL COMPOSITION OF HUMUS IN % OF ORGANIC C (TOC) Fraction Ia Fraction I Fraction II Fraction III Soil horizon C- extracted CHA CFA CHA:CFA C- extracted CHA CFA CHA:CFA C- extracted in % of TOC in % of TOC in % of TOC CHA CFA CHA:CFA Galio Sylvatici-Carpinetum O A * * * * * * * * * * * Alno-Ulmion * * * * * * O A * * * * * * * * * * * * * * * * * * Explanation: not determined, *mean values of 4 profiles.

12 128 D. KAWA KO et al. TABLE 4. CONTINUATION Soil horizon CHA I+II CFA I+II CHA/CFA I+II C-non extr. in % of TOC Galio Sylvatici-Carpinetum CHA-Ca in % of TOC O A * * * * * * Alno-Ulmion * * * O A * * * * * * * * * Explanation: not determined, *mean values of 4 profiles, **HI humification index (100%-C non extracted). HI** A4/ * * * * * * * *

13 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 129 TABLE 5. COEFFICIENT OF CORRELATIONS BETWEEN FRACTIONAL COMPOSITION OF HUMUS SUBSTANCES AND SELECTED SOIL PROPERTIES OF O HORIZONS Variable C org Nt Kh S BS CEC t C org 1.00* 0.96* Fraction Ia Fraction I - C extr * -0.77* -0.88* Fraction I - C HA * -0.79* -0.89* C non-extr * 0.78* 0.88* 0.38 HI * -0.78* -0.88* A4/A6 0.78* * * *Explanations as in Table 3. participation in the horizon A that demonstrates its high mobility in that site. In mineral humus horizon A the contribution of fraction Ia demonstrated a significant positive correlation with Kw (0.83*) and a significant negative correlation with C org (-0.78*), N og (-0.68*) and CEC (-0.73*). In all analyzed profiles, the highest share in terms of fractional content of humus substances was represented by fraction I the contribution of which in horizons O ranged from to 49.68% C org, while in the range from 9.14 to 33.93% C org in horizons A. Some differences in the amount of released fraction I were marked in the analyzed profiles. The distinctly higher amounts of released fraction I, and a higher value of the C HA /C FA ratio in the Galio Sylvatici-Carpinetum site prove the more favourable conditions of the course of the humification process and higher stability of humic acids of those habitat soils. As demonstrated by Dziadowiec [10], the high value of the ratio of humic acids to fulvic acids in forest soils is evidence of the fast rate of mineralisation of organic matter originating mainly from the fall of horizons and deciduous tree twigs. Lower values of the C HA /C FA ratio in organic horizons O both on the site of Galio Sylvatici-Carpinetum forest and Alno-Ulmion forest are connected to an inflow of fresh organic matter into those horizons, which leads to the formation of a considerable amount of organic connections of a simple molecular structure [4, 6]. Higher values of the C HA /C FA ratio in mineral humus horizons A are a result of an intense process of soil humification of organic matter and higher humus resistance to oxidation processes [20]. The contribution of fraction I and C HA of that fraction was significantly positively correlated with exchangeable acidity (Kw). A significant negative correlation of the discussed fractions in horizons O and A was noted with the sum of base cations (S) and the degree of sorptive complex saturation (BS), and in the case of humus horizon also with organic C.

14 130 D. KAWA KO et al. The higher contribution of humic acids carbon bonded to Ca (C HA -Ca) in mineral humus horizons A of soils on the sites of Alno-Ulmion forest when compared to Galio Sylvatici-Carpinetum forests was connected to a higher content of Ca +2 cation in sorptive complex and a higher degree of sorptive complex saturation with cations of a base character (BS). The contribution of fraction II in humus horizons was within the range of 1.30 to 6.09% C org, while the value of the C HA /C FA ratio of that fraction was within the range of 1.12 to A clearly higher contribution of fraction II and C HA of that fraction in the profiles of Galio Sylvatici-Carpinetum forest, when compared to soil profiles of Alno-Ulmion forest, resulted from a higher amount of colloid fraction that creates mineral-organic connections with fraction II. The contribution of fraction II and C HA of that fraction was higher in samples characterised by higher values of exchangeable acidity (Kw) and lower C org and a degree of sorptive complex saturation (CEC). That was confirmed by a significant positive correlation between these parameters. The contribution of non-hydrolysing carbon in ectohumus horizons O was in the range of to 77.68% C org, while in humic levels was considerably lower, in the range of 54.41% to 88.18% C org (Table 3). The higher contribution of non-hydrolysing carbon in the profiles of Alno-Ulmion forest may provide less beneficial conditions for humification processes connected to a higher level of groundwater and clear features of gley present at a shallow depth. Longer periods with anaerobic conditions in Alno-Ulmion forests contribute to carbon accumulation and humification process slow down which was confirmed in the values of the humification index. In analyzed samples, both from organic and humus horizons, the contribution of non-hydrolyzing carbon was significantly negatively correlated with exchangeable acidity (Kw) and significantly positively correlated with the sum of base cations (S) and the degree of sorptive complex saturation (BS), and in humus levels also with organic C. One of the basic physico-chemical properties determining the internal structure of humic acids is optical density. As was demonstrated by Kononowa [19], the optical density of humus substances depends on the ratio of carbon content in the aromatic nucleus to carbon in side radicals. The author noted that younger, as regards their chemistry, humic acids are characterised by lower optical density when compared to mature acids. This results from the high condensation of aromatic nucleus in mature humic acids, and the predominance of lateral chains in younger humic and fulvic acids. The changes in optical density of sodium humate solutions from organic subhorizons O and humic A were expressed by absorbance values with wave lengths of 465 and 665 nm, and the absorbance ratio, i A 465 :A 665 (A 4/6 ), (Table 3). It is accepted that the value A 465 determines the absorbance of the substance in an initial humification stage, and

15 FRACTIONAL COMPOSITION OF HUMUS COMPOUNDS IN THE ECTOHUMUS OF SOILS 131 A 664 substances of a high humification degree [13, 18]. The calculated lowest mean value of the A 4/6 absorbance ratio in humus horizons of profiles of Galio Sylvatici-Carpinetum forest sites point to the presence of humic acids of slightly higher molecular weight and a higher degree of aromatic structure condensation when compared to Alno-Ulmion forests soils. This confirms that of Galio Sylvatici-Carpinetum forest soils there are more favourable conditions of the course of the humification process and higher stability of humic acids of those habitat soils. CONCLUSIONS 1. The analyzed river alluvial brown soils under Alno-Ulmion forest demonstrated better physico-chemical properties when compared to fen soils under Galio Sylvatici-Carpinetum forest, which was determined by the different content of organic matter and fluming parts in particular genetic horizons. 2. The quantitative analysis of fractional composition demonstrated clear differentiation between humus compounds of organic levels and humus A in soils on analyzed Galio Sylvatici-Carpinetum and Alno-Ulmion forests. Distinctly higher amounts of released fraction I, and a higher value of C HA /C FA ratio in the Galio Sylvatici-Carpinetum site prove more favourable conditions of the course of the humifiction process and the higher stability of humic acids of that habitat soil. 3. The higher contribution of non-hydrolysing carbon in the profiles of Alno-Ulmion forest may probably prove less beneficial conditions for humification processes connected to a higher level of groundwater and clear features of gley present at a shallow depth. Longer periods with anaerobic conditions in Alno-Ulmion forests contribute to carbon accumulation and humification process slow down, which was confirmed by the values of the humification index. 4. The lowest calculated mean value of the A 4/6 absorbance ratio in humus level of profiles of Galio Sylvatici-Carpinetum forests sites points to the presence of humic acids of a slightly higher molecular weight and higher degree of aromatic structure condensation when compared to Alno-Ulmion forest soils. REFERENCES [1] B e d n a r e k R., D z i a d o w i e c H., P o k o j s k a U., P r u s i n k i e w i c z Z.: Badania ekologiczno-gleboznawcze. PWN, Warszawa, [2] B o r o w i e c S.: Roczn. Glebozn., 37(2-3), 91, 1986a. [3] B o r o w i e c S.: Roczn. Glebozn., 37(2-3), 101, 1986b. [4] C i a r k o w s k a K., N i e m y s k a - u k a s z u k J.: Zesz. Probl. Post. Nauk Roln., 60, 113, [5] C z u b a s z e k R., B a n a s z u k H.: Roczn. Glebozn., 55(1), 87, [6] D r o z d J.: Roczn. Glebozn., 24(1), 3, 1973.

16 132 D. KAWA KO et al. [7] D r o z d J., K o w a l i ñ s k i S., L i c z n a r M., L i c z n a r S.: Roczn. Glebozn., 38(3), 121, [8] D r o z d J., L i c z n a r S. E., L i c z n a r M.: Zesz. Probl. Post. Nauk Roln., 411, 149, [9] D r o z d J., J e z i e r s k i J., L i c z n a r M., L i c z n a r S.: Humic Subst. Environ., 2, 11, [10] D z i a d o w i e c H.: Humic Subst. Environ., 1, 93, [11] G a c k a - G r z e s i k i e w i c z E., C i c h o c k i Z.: Program ochrony dolin rzecznych w Polsce. Wyd. IOŒ, Warszawa, [12] G o n e t S., D ê b s k a B.: Post. Nauk. Roln., 411, 241, [13] G w o r e k B., B r o g o w s k i Z., D e g ó r s k i M., W a w r z o n i a k J.: Roczn. Glebozn., 51(1/2), 87, [14] H o r s k a - S c h w a r z S.: Struktura i funkcjonowanie geokompleksów w dolinie Odry miêdzy O³aw¹ a Wroc³awiem. Rozprawy Naukowe Instytutu Geografii i Rozwoju Regionalnego Uniwersytetu Wroc³awskiego, 2, [15] K a w a ³ k o D.: Zesz. Nauk. UP Wroc³aw, Roln., LXXXIX, 546, 109, [16] K a w a ³ k o D., K a s z u b k i e w i c z J.: Roczn. Glebozn., 59(3/4), 115, [17] Klasyfikacja Gleb Leœnych Polski: Centrum Informacji Lasów Pañstwowych, [18] K o n d r a t o w i c z - M a c i e j e w s k a K., G o n e t S.: Humic Subst. Environ., 1, 135, [19] K o n o n o w a M.: Substancje organiczne gleb. PWRiL, Warszawa, [20] M a z u r e k R., N i e m y s k a - u k a s z u k J.: Zesz. Probl. Post. Nauk Roln., 493, 659, [21] P o k o j s k a U.: Roczn. Glebozn., 37(2-3), 249, [22] R o y - R o j e w s k i S., B a n a s z u k H.: Roczn. Glebozn., 55(4), 115, [23] R o j - R o j e w s k i S., H r y n i e w i c k a I.: Roczn. Glebozn., 60(4), 85, [24] T u r s k i R.: Roczn. Glebozn., 37(2-3), 75, 1986a. [25] T u r s k i R.: Roczn. Glebozn., 37(2-3), 107, 1986b. [26] T u r s k i R.: Roczn. Nauk Roln., Seria-Monografie, 212, 69, [27] W a l e n d z i a k R. J.: Prace IBL, B, 21(1), 37, [28] b i k o w s k i A., e l a z o J.: Gospodarka Wodna, 1, 11, SK AD FRAKCYJNY ZWI ZKÓW HUMUSOWYCH GLEB LASÓW GR DOWYCH (GALIO SYLVATICI-CARPINETUM) I ÊGOWYCH (ALNO-ULMION) Celem niniejszej pracy by³o okreœlenie sk³adu frakcyjnego zwi¹zków humusowych gleb lasów gr¹dowych i ³êgowych na tle wybranych w³aœciwoœci fizyko-chemicznych. Analizowane gleby to mady brunatne œrednie, ciê kie i bardzo ciê kie o kwaœnym odczynie i korzystnych w³aœciwoœciach sorpcyjnych. W sk³adzie frakcyjnym zwi¹zków próchnicznych niewielki udzia³ stanowi³a frakcja Ia. Jej zawartoœæ waha³a siê w zakresie 1,14-7,11% C org. Wœród zwi¹zków próchnicznych dominuj¹c¹ grupê stanowi³a frakcja I (substancje humusowe zwi¹zane z wapniem i niekrzemianowymi formami R 2 O 3 ), której udzia³ mieœci³ siê w zakresie 9,14 do 49,68 % C org. W obrêbie frakcji I kwasy huminowe dominowa³y nad kwasami fulwowymi, a stosunek Ckh/Ckf przyjmowa³ wartoœci Frakcja II kszta³towa³a siê w granicach % C org, natomiast udzia³ wêgla niehydrolizuj¹cego mieœci³ siê w przedziale % C org.