Báo cáo khoa học: "Litter fall and nutrient turnover in Kermes oak (Quercus coccifera L.) shrublands in Valencia"

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Original article Litter fall and nutrient turnover in Kermes oak (Quercus coccifera L.) shrublands in Valencia (eastern Spain) b Miguel Isabel Cañellas Alfonso San a a Apdo. 8111, 28080 Madrid, Spain CIFOR-INIA, b Ingenieros de Montes, E.T.S. UPM Ciudad Universitaria, 28040 Madrid, Spain (Received 12 May; accepted 26 November 1997) Abstract - Litter fall has been measured in three Kermes oak (Quercus coccifera) shrublands, 10, 40 and 70 years after fire in the province of Valencia (eastern Spain). Annual inputs varied between 3.2 and 5.2 t ha year (D.M.), with more than 90 % of them coming from Kermes oak. -1-1 In spite of the perennial character of this species, under our experimental conditions it behaved as a deciduous one, and showed litter fall peaks in May. Leaf litter was the most important source of nutrient return to the soil (60-70 %) followed by twig (6.8-14.5 %) and flower and fruit (4.4-17.3 %) litter. The total nutrient input (macro- and oligo-elements) due to litter fall was 85.3-167.8 kg ha year Ca is the most important element followed by N, K, Mg and Na. The -1 -1. input of Fe, Mn, Zn and Cu due to litter fall was 0.55-2.31 kg ha year(© Inra/Elsevier, -1 -1. Paris) Kermes oak / litter fall / nutrient turnover / retranslocation / Quercus coccifera Résumé - Production de litière et apport au sol d’éléments minéraux dans des garrigues de chêne Kermès (Quercus coccifera L.) dans la région de Valence (Espagne). La production de litière du chêne Kermès (Quercus coccifera) a été déterminée à Valencia (Espagne) dans des garrigues âgées de 10, 40 et 70 ans après incendie. La production varie de 3.2 à 5.2 t ha andont -1 -1 plus du 90 % correspond au chêne Kermès. Bien que le chêne Kermès soit une espèce à feuilles persistantes, dans les conditions de notre expérience, le rythme de retombée de litière est de type annuel et le chêne Kermès se comporte comme une espèce décidue facultative, avec une chute des feuilles pendant le mois de mai. Les feuilles constituent la source principale de restitution des élé- ments minéraux au sol (60-70 %). Elles sont suivies des rameaux (6.8-14.5 %) et des inflores- cences et des fruits (4.4-17,3 %). La minéralomasse totale de la litière (macro- et oligo-élé- ments) se situe entre 85,3 à 167,8 kg haanselon la parcelle. Le calcium est l’élément le plus -1-1 * Correspondence and reprints E-mail: canellas@inia.es
important (50 %) suivi de N, K, Mg et Na. Les quatre oligo-éléments analysés (Fe, Mn, Zn et Cu) -1 ha . -1 an (© Inra/Elsevier, Paris) représentent de 0,55 à 2,31 kg chêne Kermès / chute litière / restitution des nutriments sol / Quercus coccifera au 1. INTRODUCTION 16, 25], Greece [7, 9, 10, 15, 26], Spain [3, 4] and other Mediterranean countries [8, 24]. However, the litter fall and nutri- (Quercus coccifera L.) is Kermes oak ent cycles of those ecosystems have sel- of the most important shrub species one dom been studied[14, 17, 18, 23]. There- in the Mediterranean Basin, where it cov- fore, the objectives of our study were 1) to ers more than 2 million hectares [8]. It contribute to the knowledge of litter fall grows under a typical Mediterranean cli- and nutrient cycles in Kermes oak shrub- mate and on a great variety of soil types, lands in Spain and 2) to provide new data either on acidic or basic parent materials from stands with different ecological con- [3]. In Spain, it is widely distributed along ditions and fire histories. the Mediterranean coastal provinces, where it sometimes constitutes the poten- tial vegetation, either as climax or as par- 2. MATERIALS AND METHODS aclimax (disclimax) communities [19]. It is also present in the interior, where it is 2.1. Study area and sampling methods associated with degraded stands of scle- rophyllous perennial forests, such as those Our experiments were conducted in Valen- dominated by holly oak (Quercus rotun- cia (eastern Spain), where Kermes oak shrub- difolia Lamk.) and cork oak (Quercus lands constitute the major vegetation type. suber L.). Due to its ability to regenerate There were three experimental sites: 1) Chera, vigorously from stumps and roots and to old growth Kermes oak shrubland more than 70 years old; 2) Buñol, mature Kermes oak shrub- resist browsing, it plays a fundamental land 40 years old; and 3) Venta Moro, young role in erosion control (especially after Kermes oak 10 years old. Cover was always fire) and as a major fodder source for almost100 %. The age of the aerial part of the wildlife and livestock (mostly goats and stand was estimated using the date of the last sheep). It is also a refuge for small game fire (table I). animals, such as rabbit (Oryctolagus cun- The climate could be included in the lower niculus) and red legged partidge (Alec- meso-Mediterranean belt of Rivas Martínez toris rufa), which are often the most inter- [ 19] with a dry ombrotype. The mean annual esting natural resources of these plant rainfall is 515 mm, and the average temperature communities from an economic point of is 13.5 °C. There is a possible frost period from late autumn (November) to early spring view [3, 4]. Finally, it contributes to soil (March), with an absolute minimum temper- formation and increases soil fertility ature of -12 °C. The soil belongs to the Calcic through the dynamics of its large root sys- Cambisol-Calcaric Regosol association [5]. tem [3] and also through litter fall. This The potential vegetation is an evergreen scle- is especially important on nutrient-poor rophyllous forest: Bupleuro rigidi-Quercetum soils, where plant communities rely to a rotundifoliae with Pistacia lentiscus [19]. How- ever, due to fire, browsing and other human great extent upon the recycling of litter influences, the current vegetation type is a con- nutrients. tinuous Kermes oak garrigue (Rhamno lycioidis-Quercetum cocciferae). Structure, function and potential usage of Kermes oak shrublands have been dis- Our sampling methods were similar to those cussed by several authors in France [11, used by Rapp and Lossaint [18] and Merino
digestion. The amount of the other mineral ele- and Martin [ 14]. Fifteen 0.25-m collecting 2 present in each fraction was determined ments baskets in each plot were randomly positioned by ignition of the plant material (1-2 g/sam- 25 cm above the soil in the Kermes oak shrub- ple) for 24 h at 490 °C. Fe, Cu, Mn, Zn, Ca lands. They had a 2-mm nylon mesh screen and Mg were determined by atomic absorp- bottom, and were identified by a number. tion (lanthanum chloride was used to control Freshly fallen litter was collected every month interference of other elements in the Ca and for 2 years. Then, it was divided into two sub- Mg analyses). Na and K were determined by samples: one for Kermes oak and another for emission spectrophotometry. Finally, P was other species. The first was subdivided again determined colorimetrically, after reduction of into three fractions including leaves, woody phospho-molybdate by stannous chloride to materials, flowers and fruits. All samples were molybdenum blue. oven-dried at 75 °C, and then weighed to the nearest milligram. The different fractions of litter samples were bulked on a monthly basis for each plot and then ground for chemical 3. RESULTS AND DISCUSSION analyses. 3.1. Litter fall 2.2. Chemical analyses In terms of quantity (table II), the aver- age annual litter production was 5 229 ± Each litter fraction was analysed monthly 538 kg ha year (D.M.) in the oldest -1 -1 for the main major-elements (N, P, K, Ca, Mg stand (Chera), 3 733 ± 284 in the mature and Na) and also for those trace-elements one (Buñol) and 3 242 ± 302 in the involved in oxidation-reduction processes (Fe youngest one (Venta Moro). These fig- and Cu) and in catalytic reactions (Zn and Mn). ures are higher than those found in the The ground samples were analysed for total N French literature [17, 18] in Q. coccifera by semimicro distillation following a Kjeldahl
fall was low in our experimental plots shrublands but similar to or only slightly ter higher than those offered by Merino and in contrast to French garrigues, where lit- Martin [14] for low shrublands of SW ter fall peaks occur in April [18]. Shoot Spain. growth occurred from late May to early June. On shallow and nutrient-poor soils Peaks of litter fall occurred in May at all (e.g. Buñol, Venta Moro), Kermes oak sites (figure 1). During that month, the shoots lost almost all their old leaves dur- leaf fraction was the most important one, ing a short period of time immediately amounting to more than 80 % of the total litter production (figure 2). The April lit- before shoot growth occurred. However,
species such as holly oak and cork oak [6, deciduous behaviour was not observed in 20] and Quercus faginea [22]. Chera, though the litter fall peak also occurred in May. This behaviour, which agrees with that described by Addicot and Lyon [1] and Specht [23] for other 3.2. Nutrient concentration Mediterranean evergreen species, could be regarded as a strategy to reduce evapo- The mineral composition of the leaf transpiration in that critical period. Ver- and woody fractions of litter fall is shown nal abscission seems to be related to for each experimental site in table III. All intense movements of nutrients to the these values are the weighted averages of growing points of plants. Therefore, in our the composition of materials shed through- case it could also be considered as a strat- out the year. egy to favour the replacement of old leaves by new ones with a greater photosynthetic Venta del Moro sites contained the low- efficiency. In consequence, on shallow concentration, except for Mg, est mineral soils and under long drought periods, Ker- for every month which was related to the mes oak could behave as a facultative soil analyses (high Mg and low levels of deciduous species. This situation could be N, Ca, P and K). related to the ability of the species to sus- We observed monthly variations in the tain summer drought. When leaf abscis- elements of different fractions; for exam- sion occurs before the summer drought ple, the concentration of N and P in leaf period, the litter decomposition process fractions seemed to decrease when litter does not begin until the first autumn rains. fall was higher. After June we observed Thus, litter may reduce herb growth more an increase in these mineral concentra- than in plant communities with other tions. The reason could be that the plant abscission cycles. In addition, we must needs these elements, which are very not forget the role of litter fall in summer scarce in forests soils, and seems to retain in reducing soil evapotranspiration. them through leaves before autumn. On the other hand, this process had not been our case, leaf litter is the most impor- In observed for the other elements (for exam- litter fall fraction, amounting to more tant ple K was at maximum from August to than 60 % of the total litter fall (table II). December, and Zn was highest from This figure, and those of the other litter fall fractions agree with the general situa- September to October). tion described by Bray and Gorham [2] and Rodin and Bazilevich [2 1] for forests of the world. However, Kermes oak does 3.3. Nutrient inputs not show cladoptosis, an active process of branch abscission that makes them fall The nutrient input due to litter fall simultaneously with leaves (figure 2). This (table IV) increases with the age of the process has been observed by Escudero stand and obviously with the amount of and Arco [6] and Martin et al. [13] in other litter fall. The total annual input for the Mediterranean and sub-Mediterranean nutrients analysed in our experiments was Quercus species. 85.3 kg ha yearat Venta Moro (the -1 -1 youngest stand), 130.9 at Buñol (the The litter fall cycle is clearly annual in mature one) and 167.8 at Chera (the oldest three experimental sites, just as other our stand). Leaf and woody litter are espe- scientists [17, 18] have described for the cially important both because of their French garrigue. This contrasts with the major contribution to total litter fall (table litter fall cycle of other Mediterranean tree
II) and their high nutrient Moro, it alone represents 50 % of the (table content III). litter- major-elements recycled through fall. N is next, with amounts of 45.5, 36.7 Ca input through litterfall was the and 24.4 kg ha year(30 % of the ele- -1 -1 largest among those of the nutrients anal- ysed. With amounts of 78.6 kg hayear -1-1 ments analysed), respectively, at those at Chera, 57.6 at Buñol and 34.4 at Venta experimental areas. The other elements,
in descending order of importance (by the present case, the process of ents. In weight), are K, Mn, Na and P. The four vernal abscission and subsequent resprout- trace-elements analysed return to the soil ing seems to be related to intense move- through litter fall in total quantities of 1.3 ments of nutrients to the growing points kg hayearat Chera, 2.3 at Buñol and -1-1 of the plant. The major nutrient content 0.6 at Venta Moro. This means 0.7-1.7 % of leaves, wood and bark of live Kermes of the total amount of the elements anal- oak shoots (table V) is slightly higher than ysed. that of leaf and woody litter fall. It seems, therefore, that retranslocation of nutrients Comparison of our data with those of occurs before leaves and shoots are shed. the French garrigues presented by Rapp This behaviour could be regarded as a [17] and Rapp and Lossaint [18] is not strategy to increase efficiency in the uti- easy owing to differences in sampling and lization of nutrients. It might constitute a laboratory techniques. However, though valuable process for plants growing on the nutrient (major- and trace-elements) nutrient-poor soils (such as those of our content of the French garrigue litter fall experimental sites) and under adverse cli- was higher than that of ours (maybe owing mates (such as the semiarid Mediterranean to higher nutrient concentrations in the one). However, it usually gives an inac- soil), the total amount of nutrients returned curate estimate of resorption because it to the soil is slightly higher in the Spanish does not include correction for weight loss Kermes oak shrublands owing to higher of leaves. For instance, nutrients that are figures of litter biomass. not resorbed at all will increase their con- A final aspect that should be discussed centration (and hence give negative resorp- is that related to retranslocation of nutri- tion values) owing to the weight loss of
Escudero A., del Arco J.M., Ecological sig- [6] leaves during senescence as a consequence nificance of the phenology of leaf abscission, of reduction of other mobile nutrients and Oikos 49(1) (1987) 11-14. compounds such as carbohydrates. This Koukoura Z., Composition of Kermes oak [7] is probably the main reason for the browse as affected by shade and stage of increase in Mg and Ca and the rather low maturity, Anim. Feed Sci. Technol. 21 (1988) 1-9. of resorption for most mobile elements, Le Houerou H.N., Impact of man and his ani- [8] for example N and P. mals on Mediterranean vegetation, in: di Cas- tri F., Goodall D.W., Specht R.L. (Eds.), Mediterranean-Type Shrublands. Origin and Structure, Elsevier Scientific Publishing Com- ACKNOWLEDGEMENT pany, Amsterdam, 1981, pp. 479-521. Liacos L.G., Grazing management of ever- [9] This work was funded by the Spanish green brushlands in Greece, in: Conrad C.E., National Institute for Agricultural Research Oechel W.C. (Eds.), Dynamics and Manage- ment of Mediterranean-Type Ecosystems, (INIA), Research Project 8147. USDA Gen. Tech. Rep. PSW-58, Berkeley, 1982, pp. 270-275. Liacos L.G., Moulopoulos Ch., Contribution [ 10] REFERENCES to the identification of some range types of Quercus coccifera L. in the north of Greece, For. Res. Center Es. Bull. 16, Thessaloniki, Addicott F.T., Lyon J.L., Physiological ecol- [1] 1967, 54 pp. ogy of abscission, in: Kozlowski T.T. (Ed.), Long G., Fay F., Thiault L., Essais de déter- [11] Shedding Ecology of Plant Parts, Academic mination expérimentale de la productivité Press, New York, 1973, pp. 235-265. d’une garrigue à Quercus coccifera, CEPE- Gorham E., Litter production in Bray J.R., [2] CNRS, Doc. 39, Montpellier, 1967, 22 pp. forests of the world, Adv. Ecol. Res. 2 (1964) Lossaint P., Rapp M., Répartition de la [12] 101-158. matière organique, productivité et cycles des características y Cañellas I., Ecología, elements minéraux dans des écosystèmes de [3] usos de los coscojares (Quercus coccifera L.) en climat mediterranéen, in: Duvigneaud P. España, Ph.D. thesis, Polytechnic University (Ed.), Productivité des écosystèmes forestiers, of Madrid, Madrid, 1993, 574 pp. Brussels, 1971,pp. 587-617. Martin A., Gallardo J.F., Santa Regina I., [13] Cañellas I., San Miguel A., Structure and [4] Aboveground litter production and bioele- browse production of Kermes oak shrublands ment potential return in an evergreen oak in Spain, in: Gaston A., Kernick M., Le (Quercus rotundifolia) woodland near Sala- Houerou H.N. (Eds.), Proc. IVth Int. Range- manca (Spain), Ann. Sci. For. 53 (1996) land Congress, vol. I, Association Française 811-818. de Pastoralisme, Montpellier, France, 1991, pp. 518-520. Merino O., Martin A., Producción de [14] hojarasca en dos formas de matorral del SW Commision of the European Communities, [5] Español, Lagascalia 15 (1988) 535-540. Soil Map of the European Communities (1: Liacos L., Productivity Papanastasis V.P., 1.000.000), D.G.A. Luxenbourg, 1985, 124 [15] and management of Kermes oak brushlands pp.
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