Báo cáo khoa học: "Micronutrients in biomass fractions of holm oak, beech and fir forests of the Montseny massif (Catalonia, NE Spain)"

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Original article Micronutrients in biomass fractions of holm oak, beech and fir forests of the Montseny massif (Catalonia, NE Spain) J Terradas A Caritat CREAF, Facultat de Ciències, Universitat Spain Autònoma de Barcelona, 08193 Bellaterra, Barcelona, February 1990) 28 July 1989; accepted 24 (Received Summary - This study is part of a larger research programme on different forest ecosystems in the Montseny massif (Barcelona, NE Spain). The contents of 4 micronutrients (Mn, Fe, Zn and Cu) are given for some biomass fractions in individual monospecific stands of holm oak (Quercus ilex L), beech (Fagus sylvatica L) and fir (Abies alba). The behaviour of different micronutrients is related to relative mobility. Mn, Fe and Zn concentrations increase with leaf age. Nutrient levels of the Montseny stands are compared with those found in other forests of the same species. We have observed relatively high Mn concentrations in different biomass fractions of the holm oak forest studied. This can be related to the low soil pH values. Our 3 forests show different micronutrient allocational patterns. Total quantities of the micronu- trients in the biomass are only calculated for Q ilex forest. Values found are 33.6 kg Mn/ha, 15.0 kg Fe/ha, 2.8 kg Zn/ha and 0.17 kg Cu/ha. / Abies alba Fagus sylvatica biomass fraction / micronutrient / Quercus ilex / Résumé - Éléments traces dans la biomasse de la chênaie, de la hêtraie et de la sapinière du massif de Montseny. Ce travail fait partie d’une étude sur les différents écosystèmes fo- restiers du massif de Montseny (Barcelone, NE, Espagne). La composition en Mn, Fe, Zn et Cu de différents compartiments de la biomasse est analysée pour des parcelles monospécifiques de chêne vert (Quercus ilex), de hêtre (Fagus sylvatica) et de sapin (Abies alba). Les concen- trations en Mn, Fe et Zn augmentent au cours du vieillissement de la feuille. Les niveaux de ces concentrations ont été comparés pour les espèces correspondant à celles d’autres forêts. Le niveau du Mn est relativement élevé dans les différents compartiments des arbres de l’espèce chêne vert. Cette différence est à mettre en relation avec la basse valeur du pH du sol. A chacune des 3 forêts étudiées correspond un type différent de répartition de ces éléments traces. Hospital, Present address: Estudi General de Girona, Laboratori del suro, C/ * and reprints. Correspondence Spain 6 -17071- Girona,
L’immobilisation totale dans la biomasse de ces éléments traces n’a été calculée que pour le peuplement de chêne vert. Elle est évaluée pour le Mn, le Fe, le Zn et le Cu respectivement à 33,6, 15, 0, 2,8 et 0,17 kg/ha. de la biomasse / élément trace / Quercus ilex / compartiment Fagus sylvatica / Abies alba INTRODUCTION monospecific forest canopies, in 3 different stands of the Montseny range in northern Spain, and also to look for Studies on mineral element cycling in differences related to the life cycles forest ecosystems have focused mainly and leaf morphology in these 3 species on the major nutrients. Data on micro- by comparing the micronutrient con- nutrients are relatively scarce, and tents of the various biomass fractions. most aspects of the role of micro- nutrients in ecosystems’ components are poorly understood. We know that THE STUDY AREA micronutrients accumulate in highly me- tabolically active parts of the plant, like The experimental plots are located in leaves and twigs, because of their in- the Montseny massif, about 40 km NNE volvement in enzymatic reactions within of Barcelona. coenzyme molecules (Kramer and Koz- lowski, 1979). Concentrations of the The evergreen oak plot (41°16’ N, 2° 21’ E, 665 m asl) measures 0.23 ha relatively immobile elements increase with the age of leaves, probably due and lies within La Castanya Biological to a passive accumulation in the tran- Experimental Station, at the foot of a spiration flow and to relatively low ab- rough mountain slope (30°). The slope sorption rates (Larcher, 1977). The in the plot is slight, varying from 7 to lowest concentrations are found in 23°, and the orientation is W and NW. wood; nevertheless, wood is the bio- The bedrock consists of a metamorphic mass fraction containing the greatest schist, and the soil is a ranker (U 2 b/c, quantity of micronutrients, simply be- gravelly phase) associated with a dys- cause it is the largest one. Concentra- tric cambisol (Bd). Mean annual pre- tions usually decrease as the stem cipitation is around 900 mm and mean diameter increases. Bark is an area of annual air temperature is 9 - 10 °C. accumulation and usually has high mi- The tree layer is dense and formed ex- cronutrient concentrations (Denaeyer clusively of Quercus ilex. The basal area was 26.6 m in 1979. There /ha 2 De Smet, 1971). were 2 100 stems/ha with a DBH > 5 As occurs frequently with major cm and 536 stems with DBH > 15 cm. nutrients, rates of change and total The dominant trees were 9-12 m in content of oligoelements vary greatly height and had an estimated age of among species. The aim of this study 60 - 90 years. was to determine the levels of 4 micro- The beech plot (41° 46’ N, 2° 28’ E, nutrients (Mn, Fe, Zn and Cu) in the different biomass fractions of holm oak 1 165 m asl) measures 0.12 ha and is (Quercus ilex), beech (Fagus sylvatica) located in the Santa Fe Valley. The slope is gentle (5°). The bedrock is a and silver fir (Abies alba), growing in
wood from 10 trees (September 1983). In the deep altered granodiorite, and the soil fir forest (Passavets) we collected samples is a dystric-humic cambisol (Bd - Bh, of leaves, 1-5 yr-old branches and wood 1 a). Mean annual precipitation is about boles belonging to 3 fir trees. average air 1 200 mm (Rod, 1983) and Bulked samples of each biomass fraction is 8 - 9 °C. The canopy is from the different trees in each plot were temperature analysed. They were dried to constant dense and consists of Fagus sylvatica weight at 80 °C. Mn, Fe, Zn and Cu were with some isolated individuals of Ilex analysed by atomic absorption with a PYE aquifolium as subdominants. The basal UNICAM Sp-1900 (Spectroscopy Service, area was 26.7 m in 1980. There are /ha 2 Barcelona University) after acid digestion, 1 460 stems/ha with a DBH > 5 cm and following the methods described by Allen et 625 stems/ha with DBH > 15 cm. The al (1974) for Mn, Fe and Zn. For Cu, due to the low concentrations, it was necessary to dominant trees are 16 -20 m in height adopt a different procedure: the samples and 50-60 years old. The last tree thin- were digested with HNO and HClO on a4 3 ning was carried out between 15 to 30 hot plate, gradually increasing the tempera- years ago. ture to 210 °C and maintaining it at this level The fir plot (41° 47’ N, 2° 27’ E, to the end of the digestion. These Cu ana- lyses were carried out in the Department of 1 355 m asl) is in the Passavets fir for- Soil Science of the University of Aberdeen. est. It measures 0.12 ha and is situated The micronutrient concentrations were on a NNW slope. The bedrock is a analysed in order to determine individual hornfels and the soil is a ranker (U 2 d, tree variability in the different biomass frac- stony phase) associated with dystric tions of 11 holm oaks. The variability of the lithosols. The mean annual precipitation different elements is less than 12% in all the biomass fractions except in the stem wood is 1200 mm and the mean temperature where it is between 12 and 22%. Total mi- is 7-8 °C. The tree layer is dense and cronutrient quantities have been calculated is composed entirely of Abies alba Mill. from the biomass values obtained by dimen- The basal area was 42.4 m in 1980. /ha 2 sional analysis (Ferres, 1984) and micro- There were 567 stems/ha with a DBH > nutrient concentrations. 5 cm and 467 stems/ha with DBH > 15 cm. The dominant trees were 21-25 m in height and from 120-160 years old. RESULTS AND DISCUSSION METHODS Micronutrient concentrations For the holm oak forest (La Castanya stand) The concentrations in the different frac- used the field samples of the biomass we tions agree with the general trends dis- fractions collected previously by Ferres (1984). These samples, obtained from 15 cussed in the introduction, as can be trees from even stem diameter class, were seen in table I. divided into: leaves (separated into age In the holm oak, we can combine our classes); 1 or 2 year-old twigs of 0-1 cm dia- data with those of Ferres (1984) for meter (bark included); wood from the branches (divided into 1 cm diameter major nutrients to obtain the following classes); wood from the boles, and bark nutrient ranking: Ca > N > K > Mg - from the branches and boles. We took ad- P > Mn > Fe > Na > Zn > Cu. In the ditional bole wood samples from 10 trees cases of the beech and fir stands, we with a Pressler borer. lack similar data on the major nutrients, In the beech stand (Santa Fe) we col- but the micronutrient ranking is identi- lected samples of leaves, twigs and thin
cal. Concentrations in the individual bi- (table II). Montseny beech leaves show omass components are as follows. Fe levels similar to other beech forests (Guha and Mitchell, 1966; Heinrichs and Mayer, 1980), but for Mn we observed rela- Leaves tively low values. Fir has low Mn concen- In the holm oak, Fe concentrations in the trations. As expected, at Montseny the leaves are similar to these found in the beech leaves are richer in Fe than the leaves of the holm oak or the fir. Rouquet (Rapp, 1971) and Zn concentra- tions are close to those found in Prades The Mn requires further comment. We (Escarre et al, 1983). Mn levels are higher know that micronutrients are, in general, than those at either Rouquet or Prades more available in areas with a slightly acid
Thus, the Mn concentrations in the (Sutcliffe and Baker, 1979). This is pH Montseny holm oak could be a con- reflected in the biomass content of sequence of the relatively high amounts these nutrients. Nihlgård and Lindgren of Mn in the soil and the low pH values (1977) studied 3 beech forests growing when compared with the other sites with on different soil types and found that holm oak forests studied by Lossaint and Mn oxidizes and precipitates, becom- Rapp (1971) and Escarré et al (1983). ing unavailable to plants at a pH higher Incidentally, the beech and fir stands than 6. As a result, the concentrations studied here have relatively less acidic and contents of this element in plant soils than at the other European sites tissues are higher in beech forests where the same species have been growing on acid soils where production studied, and this may explain why Mn is also low. Olsen (1948) observed that, levels are lower in Montseny. on calcareous soils, beech leaves show concentrations of Fe higher than those of Mn, while on acid soils, the reverse and stems Twigs, branches is true. Passama (1970) analysed Mn, Fe and Zn in the leaves of holm oaks growing on acid and calcareous soils The twigs in the holm oak stands have and found that there was a general ten- Mn and Zn concentrations similar to dency for the levels to increase with acid- those found in Prades (Escarre et al, ity, especially for Mn. 1983) and higher concentrations of Fe.
The concentration of Cu in the twigs Other fractions is higher than that of the leaves for holm We have considered the bark, inflores- oak and fir, but for beech the reverse is cences and fruits for the holm oak alone true. In general, fir branches are rela- (table I). Our results do not require much tively rich in micronutrients. The obser- comment. It is worth noting, however, that vations of micronutrient accumulation, Fe and Zn are present in relatively low and especially of Fe, in relation to the concentrations in acorns, showing a pat- age of the twigs, made by Heinrichs and tern similar to that observed for Na Mayer (1980) for Picea abies forests, (Ferres, 1984) in the same stand. Mn suggest a storage function. Our results and, especially, Zn have quite high for fir could also be the result of the values in the inflorescences. storage of the less mobile elements in that biomass fraction. The stem wood is poor in micro- Micronutrient levels in the biomass nutrients in the 3 species, except for Cu in the beech (table I). The micronutrient levels in the biomass Using the data collected by Rodin and obviously depend on the quantity of the Bazilevich (1967) on temperate forests, biomass. In figure 1 we show the dis- tribution of Mn, Fe and Zn in the holm holm oak leaves contain, in general, lower concentrations than are found in oak. Table III shows data from the differ- the leaves of deciduous trees and are ent types of forests. Note that the 3 holm closer to the concentrations found in con- oak forests are rather poor in Mn and Fe ifers; however, the holm oak wood is when compared with the F sylvatica and richer than that of deciduous trees. This P abies stands. However, they are rela- pattern is not observed clearly in our tively rich in Mn when compared with Montseny data. stands of Mediterranean pines.
CONCLUSION quantities of Mn and Ca are found in the bark. As for the macronutrients, the foliar The concentration ranking of the micro- micronutrient levels represent an impor- nutrients studied in the Montseny tant percentage of the total amount of stands is the same for all 3 types of these elements if we bear in mind that forest: Mn > Fe > Zn > Cu. The holm the leaf biomass is only 3.8% of the oak shows values similar to those found total biomass of this forest. The per- at other sites with the same species, centage of Mn located in leaves is except for Mn. The high levels of Mn especially high and is greater than the in Montseny are probably due to low percentage of N. Leaf nutrients have a soil pH and the resulting high concen- higher turnover rate than the nutrients trations of soluble Mn in the soils. stored in other biomass fractions. Usually, high micronutrient concen- Our 3 forests show different micro- trations are found in the most metabo- nutrient allocational patterns, and this lically active tissues: the leaves and is probably related to their different twigs. The levels in fir branches are the modes of life (deciduous, evergreen exception. Mn, Fe and Zn levels in- conifers, broad-leaved evergreens). crease with leaf age as do the other Beech tends to have higher concentra- accumulating elements such as Ca and tions of Mn and Fe in the leaves. Holm Na (Ferres, 1984). On the other hand, oak has a relatively even distribution N and P are translocated more easily. (except for the high levels of Mn in Concentrations of these metals in the leaves). Fir, as other conifers, shows wood decrease as the diameter in- high micronutrient levels in the creases, as do the marcronutrients, be- branches. cause of a dilution phenomenon. The wood and bark of the holm oak forest contain a large proportion of the ACKNOWLEDGMENTS nutrient content, as is usual in forest ecosystems, because of their great This work was supported financially by the quantity. The main part of the Fe, Zn CAICYT. We thank Estació Biològica de la and Cu is found in the wood, bark, Castanya de la Generalitat de Catalunya and leaves and twigs. Mg, Na, N and K the Servei de Parcs Naturals de la Diputació show the same pattern. The highest de Barcelona. We also thank Dr Miller and
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