Báo cáo lâm nghiệp: "Experimental research in ageing holm oak (Quercus ilex L.) coppices: preliminary results"

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Original article Experimental research in ageing holm oak (Quercus ilex L.) coppices: preliminary results Orazio la Marca* Pasquale A. Marziliano Nicola Moretti Istituto di Assestamento e Tecnologia forestale (IATF), Università di Firenze, Via S. Bonaventura n° 13 -I-50145, Florence, Italy (Received 23 September 1996; revised 9 January 1997; accepted 17 September 1997) Abstract - The initial data of a long-term research programme aimed at determining the silvi- cultural choices for management of ageing holm oak coppices are reported. The various treatments being tested are the following: treatments A and B, respectively, with 50 and 250 reserve trees per hectare, all of the same age; treatment C with 140 reserve trees per hectare, with three different ages; treatment D, conversion into high forest; and treatment E, natural evolution (the control). A total of 15 permanent plots were established (five treatments x three replicates) and the exper- imental design used is that of randomized blocks. The results presented regard the structural development of the coppice during the first 2 years after coppicing. Regeneration from seed showed a significant correlation with treatment. Data relative to the characteristics of the stands existing before the various interventions also are given. Such preliminary results need further peri- odical observations. (© Inra/Elsevier, Paris.) Quercus ilex L. / coppice / regeneration / cutting method / snow breakage Résumé - Expérimentation concernant les taillis vieillis de chêne vert (Quercus ilex L) : premiers résultats. Les résultats obtenus et ici présentés font partie d’un projet de recherche dont l’intention est d’individualiser des possibles options de culture pour les taillis de chêne vert vieillis. On a confronté les cinq thèses suivantes (avec trois répétitions) : les thèses A et B avec respectivement 50 et 250 réserves par hectare ayant toutes le même âge ; la thèse C avec 140 réserves par hectare, ayant trois âges différents ; la thèse D, conversion en futaie ; la thèse E, évolution naturelle. Les résultats exposés concernent l’évolution du peuplement pendant les deux premières années du cycle productif. Pour ce qui concerne la regénération, la présence des semis semble être favorisée par un couvert pas trop excessif des réserves. Il s’agit malgré tout de résultats préliminaires qui dérivent de parcelles d’échantillonage permanentes où, chaque année, réalisera des reliefs. (© Inra/Elsevier, Paris.) on Quercus ilex L. / taillis / regénération / méthode de coupe / bris de neige * Correspondence and reprints E-mail: IATF@cesit l.unifi.it
sideration the spread of this species over 1. INTRODUCTION the last 40 to 50 years, it is believed that the surface area covered by holm oak In ancient times the holm oak was con- woods is increasing. On the Gargano head- sidered a sacred tree. Reverence for this land, holm oak coppices form units, often tree probably derives from its importance of considerable extension, which in gen- to the economy, uncommon vigour and eral coincide with highly degraded soils. In longevity as well as its modest require- some particularly impervious areas, the ments when grown both as a coppice or holm oak is the dominant species. This high forest. As noted by Pavari [19], and species can be found isolated or in small still today, many place names in Italy are groups on slopes with a southern expo- in reference to this species. Holm oak sure up to the highest elevations of the wood was considered as an optimum fuel, Gargano headland (around 1 000 m a.s.l.). as it still is today, and also was used to make tools and other objects subject to Until 40 to 50 years ago, the most com- considerable wear. Its bark was used in management method for the holm mon the tanning industry, and the acorns and oak was coppicing with few reserve trees brushwood were used for food and bed- per hectare, in order to satisfy the high ding in the breeding of both wild and demand for fuelwood and for charcoal domestic animals. production. The coppicing, carried out at short intervals (the rotation period was 15 Holm oak woods have played and con- years), together with the practice of grub- tinue to play a key role in soil conservation bing (to increase the quantity of wood to in protecting the soil from excessive inso- be removed at the end of each cycle), lation, leaching and erosion, even in resulted in some zones in a notable degra- extremely difficult geomorphological con- dation. ditions. With the decrease in anthropic pres- spite of the human intervention of In and due to the considerable capacity sure replacing the holm oak with other species of regeneration characteristic of this where pedological and geomorphological species, the general situation of holm oak conditions allow, due to its uncommon coppices has improved considerably as resilience in unfavourable conditions and regards canopy closure and growing stock, its capacity to colonize the most impervi- and in the best edaphic conditions in ous areas, the holm oak justly remains one regard to biodiversity. of the species characteristic of the Mediter- ranean landscape. As observed by Pignatti The main problem to be confronted in [20], in a broad area of the Mediterranean forestry regarding management practices region, holm oak stands represent the the choice of silvicultural meth- concerns potential natural vegetation. In addition, ods suitable for the new economic and these stands also represent a rare exam- environmental situations in which holm ple of equilibrium in the interaction oak coppices are found, in particular between natural factors and anthrophic within the National Park of the Gargano. activity. Few references appear in the research literature regarding holm oak formations. On the Gargano headland (south-east- Interesting studies on holm oak carried ern Italy), in addition to colonizing the out in France do provide management low-lying areas at the edges of agricul- tural land, holm oak also tends to colo- indications of general application [2, 8-13, 21]. Studies on biomass estimation equa- nize the internal areas on sunny exposures tions for individual holm oak were devel- up to relatively high elevations (> 800 m oped in Spain [6, 7] and in Italy [4, 5]. A above sea level [a.s.l.]). Taking into con-
slope with a southern exposure where calcare- survey on the potential wood production ous outcrops frequently occur. According to and coppice rotations of holm oak has the FAO classification, the soils belong to been carried out by Hermanin and Pollini Chromic cambisols. The climate is of Mediter- [16] in Tuscany, Italy. A research on veg- type, with precipitations close to ranean etative regeneration during the first 3 years 650-700 mm/year, high rates of atmospheri- after coppicing of Quercus ilex in the cal humidity and 3 months of summer aridity (sensu Bagnouls-Gaussen). The coppice is Maremma Nature Park (Tuscany, Italy) located on steep slopes (around 40 % inclina- has been studied by Giovannini et al. [15]. tion). The experimental plots delineated for More recently in Italy, within the MED- this study were chosen in an ageing coppice COP project (Improvement of coppice around 45 years old which, during the sum- forests in the Mediterranean region), other mer months, was normally used as pasture land. research on holm oak coppices has been The coppice was dominated by holm oak with carried out [1, 14, 17]. a sporadic presence of flowering ash (Fraxi- nus omus) and European hophombeam (Ostrya The present study in the Gargano head- carpinifolia). The traditional management had land, initiated in 1993, is aimed at pro- a short rotation period (15 years) and release of results on which to viding experimental 60-70 reserve trees per hectare. Before the sil- vicultural interventions (February 1993), the base silvicultural choices (natural evolu- holm oak stand had a high density of stems of tion, conversion into high forest, coppice resprout origin (mean stand density 6 300 management) regarding the management stems/ha, of which about 70 reserve trees). The of ageing holm oak coppices at more or number of shoots per stump was 5.5. The diam- less maximal density. The effects of eter at breast height of shoots was 9.5 cm; basal reserve trees (from 50 to 250) on the area 44 m and volume about 200 m . -1 ·ha 3 -1 ·ha 2 development of seedlings and shoots dur- Undergrowth in the study area is repre- ing the first 2 years after coppicing are sented mainly by Asplenium onopteris, Asple- examined here. The treatments to be con- nium trichomanes, Cyclamen neapolitanum fronted are suitable for the new economic and Ruscus aculeatus, all species typically found in stands of holm oak. and environmental situations (national park) in which these holm oak coppices The main objective of the study (in the long to compare various types of manage- are found. term) is ment methods applied to ageing holm oak cop- The wind storm that occurred in pice. Gargano at the end of August 1994 (wind The experimental design adopted is that of speed around 150 km·h), and the excep- randomized blocks. The treatments compared tional snowfall at the beginning of Jan- are: treatment A: coppice with 50 even-aged uary 1995 (over 120 cm of snow with den- (40 years old) reserve trees per hectare; treat- sity between 0.25 and 0.30 g·cm ), -3 ment B: coppice with 250 even-aged (40 years old) reserve trees per hectare; treatment C: offered the opportunity to value the coppice with 140 uneven-aged reserve trees mechanical resistance of studied stands to per hectare, of three different ages - 80 of 40 the meteoric events of extraordinary inten- years and 60 from 55 to 70 years; treatment sity. D: conversion into high forest, obtained with the release of a great number (about 2 000) of trees to gain a transition high forest; treatment E: natural evolution (control). 2. MATERIALS AND METHODS In February 1993, a total of 15 permanent plots were established (five treatments x three The holm oak coppice used for the present replicates). The plots were square in shape, study is located in Monte S. Angelo (Promon- each with a surface area of 1 600 m They . 2 tory of the Gargano in southern Italy on a were separated from each other by a distance of peninsula of the Adriatic coast). The holm oak around 10 m on all sides in order to avoid stands cover about 2 500 ha. The coppice is a ’border effect.’ found at an altitude of around 650 m a.s.l. on a
Before cutting (i.e. the silvicultural inter- The choice of the trees to be left reserve standing was based on good development and vention), the inventory of the tree populations shape of the tree (this criterion led to decreas- in each of the 15 plots was taken. The ing ’quality’ as their number increased). height/diameter relationship was determined the basis of measurements carried out on After coppicing (March 1993), all of the on 100 trees, selected on the basis of representative plots relative to treatments A, B and C were surrounded by barbed wire to protect the young criteria from among all the diameter classes. shoots from free-roaming livestock. These trees have been used also to determine a single-entry volume table, showing the vol- In August 1993 a planimetric drawing umes and the fresh and dry weight of the trees showing the position of each reserve tree (fig- up to 3 cm in diameter (excluding brushwood). ure 1) was made for each of the plots in which
treatments A, B and C were adopted. In each among the shoots. In fact, in December 1993 all plot a transect diagonal with a NE-SW direc- the shoots were marked at the base with indeli- tion (20-m long and 1-m wide) was drawn and ble paint, so that it was possible to note on each mapped. For each species, the positions of all stump if there were any new shoots from the the seedlings and stumps in each transect were growing season following the first. indicated so that their evolution over the period of the study could be followed, including the effect of the shading potential of the reserve 3. RESULTS trees. In this regard, in the treatment plots A, B and C, 30 reserve trees of different ages were selected around which concentric plots were The main dendrometric parameters drawn, each having a radius up to three times before and after the cutting together with that of the radius of the canopy of the reserve the entity of the mass removed are shown tree. A detailed inventory of the seedlings and in tables I, II and III for each plot. shoots in these concentric areas was also made so that their evolution could be followed (fig- The analysis of variance (ANOVA) 1). ure carried out on the data for the number of stumps, total number of shoots per ha and The data collected on the coppice after cut- ting concerned the seed and vegetative regen- number of shoots per stump before the sil- eration. The inventory on the seed regenera- vicultural intervention show that there carried out both for the 20-m 2 tion was were no significant differences in any of transects and the concentric plots. In December these parameters. The average values for 1993 and November 1994, various dendro- the number of stumps, total number of metric features (collar diameter in mm and shoots per hectare and number of shoots height in cm) were measured on all the seedlings present in the transects and in the per stump are given in table IV for each concentric plots. In the course of the second treatment together with the relative statis- sampling (November 1994), a check was also tical indices calculated from the collected made to see if there were any new seedlings data. and whether any of the seedlings noted in the first sampling had died. The location of each seedling in the concentric plots was related to the projection of the canopy of the reserve tree. 3.1. Construction of volume table This was accomplished by specifying classes of distance from the edge of the projection of the Using the measurements carried out on canopy, each 1-m wide; the increasing dis- sample of 100 trees, the following semi- a tances outward from the edge of the canopy logarithmic equation was employed to cal- were indicated with positive numbers, while those under the canopy going inward towards culate the height curve (figure 3) of the the tree were indicated with negative numbers sampling stand before the various silvi- (figure 2). cultural interventions: Data on vegetative regeneration were col- lected for all the stumps present in the transect and in the concentric plots. The number of where H height and D diameter at 130 = = stumps per hectare were determined, in August breast height in cm. 1993, from the complete census of each plot. The volumes of the shoots taken in the The position of each stump in the concentric plots was related to the projection of the canopy sample are a function of their diameter at of the reserve tree, in order to evaluate any breast height (130 cm). The volume curve possible differences in growth or mortality of (figure 4) was calculated from the fol- the shoots. In December 1993 and November lowing model: 1994, the number of shoots per stump, the col- lar diameter of all the shoots and the total height of 15 shoots for each stump were determined. where V = volume and D diameter at 130 The sampling done in the 2nd year (Novem- = breast height in cm. ber 1994) determined the mortality occurring
Finally, the volume table (table V) was equation expresses the volume, This transformed into a weight determination including the bark, of the shoots (trees) in 3 m (with a 3-cm topping) as a function of table. The ratio between the weight of the timber and its volume was calculated for their diameter at breast height, expressed 300 samples collected from 100 trees at in cm. The correlation coefficient obtained good (R 0.967). 2 different heights (at the base of the tree, was = very
3.2. Gamic and vegetative regeneration at half-height and at the top of the tree). Both the volumetric mass (ratio between fresh weight and fresh volume) and the The data collected on seed regenera- basic density (ratio between the dry weight tion made it possible to determine the mor- and the fresh volume) were calculated. tality among seedlings, the number of The fresh weights were those measured seedlings per hectare in the various treat- on the same day as the cutting (February ments during the first 2 years after the sil- 1993), while the dry weights were those vicultural interventions (together to pre- determined by drying the samples to con- existent seedlings). In addition to the stant weight in an oven at 85 °C. seedlings recorded in the first years, approximately 1 000 were noted in the fol- The volumetric mass was 1.169 g·cm -3 lowing year. ANOVA was conducted on and the basic density was 0.746 g·cm . -3 all parameters considered. The number of The weight determination table (table V), seedlings per hectare, diameter at the col- therefore, was derived from the preced- lar and their height are shown in table VI. ing volume table simply by multiplying Mortality was found to be 11.0 % in treat- the volume values by 1 169 and 746, ment A, 13.5 % in treatment B and 7.3 % respectively. In this way, one obtains the in treatment C. ANOVA showed signifi- fresh and dry weights expressed in kilo- cant differences (P = 0.05) in the number grams as a function of tree diameter. of seedlings between treatments A and C
in both the 1st and 2nd years, while no The data collected on vegetative regen- eration made it possible to determine the significant differences in the dimensions of average diameter and height of the shoots the seedlings were found between the var- and the number of shoots per stump in ious treatments. The study on the pres- 1993 and 1994. ence of seedlings in relation to the dis- tance from the canopy of the reserve trees The average number of stumps per (table VII) has so far revealed no signifi- hectare, after cuttings, was found to be cant datum. However, the greatest con- 1 108 for treatment A, 865 for treatment B centration of seedlings seems to be found and 991 for treatment C. After the silvi- (in all treatments) around the edge of the cultural interventions, since treatments A, B and C differ in the number of reserve canopy.
hectare, clearly the number of number of shoots per hectare in treatment trees per left for vegetative regeneration is A is still significantly higher than that in stumps obtained by subtracting the number of other treatments, while there are no sig- reserve trees from the total number of nificant differences between the height of shoots and their diameters for the various stumps. treatments. Two years after the cutting, almost all The data collected in the concentric of the stumps were found to have living made it possible to determine pos- plots shoots. Some stumps without living shoots sible differences in diameter and number (four stumps per hectare) were found only of shoots between the areas falling under with treatment A. The number of shoots the canopy of the reserve tree (shoots per stump, in 1994, was 35.8 for treatment shaded by the tree) and those falling out- A, 31.2 for treatment B and 27.8 for treat- side the influence of the canopy (free ment C (table VIII). About 35 % of the shoots). The total number of stumps sur- holm oak shoots present in the 1st year veyed in the 30 concentric plots was 364. following felling died (table IX). Gener- ally, the dead shoots were found under the The processed data (table X) show that, canopy and growing in anomalous direc- where diameters are concerned, values tions. At the start of the second vegeta- slightly increasing from the trunk of the tive season, a fresh production of shoots reserve trees outwards as far as the edge of occurred on the stumps (an average of the canopy projection, from the edge of about 11 shoots per stump). During the the canopy outwards the findings take on next survey these new shoots will be a random character. observed, with their modest dimension (the fact that they are dwarfed by other shoots), to determine whether they are in 3.3. Damage from meteoric events a condition to develop or are destined to fail. Table XI indicates the number of trees Analysis of variance revealed that, at per hectare and the average diameter of distance of 2 years from coppicing, the the trees standing before the two meteoric a
events cited earlier, together with the num- 70. On the basis of these observations, in ber of trees uprooted or broken per hectare first approximation, the critical value of and the remaining number of trees per the height/diameter ratio for the shoots of hectare after the said events. The data holm oak is around 70. show that the intensity of the damage var- ied considerably depending on the treat- ment chosen (number of reserve trees per 4. DISCUSSION AND CONCLUSION hectare). In both absolute and relative terms, the greatest damage was found in The emergence and growth of the the plots in which treatment B (250 reserve seedlings took place chiefly in the year of trees per hectare) was used. On the aver- cutting and during the first vegetative sea- age, more than 50 % of the reserve trees son of the coppice. The number of were broken or uprooted, with an average seedlings emerging in the course of the volumetric loss of 7 m. -1 ·ha 3 2nd vegetative year proved to be rather small. in which treatment A In the (50 plots hectare) was adopted, an trees per reserve Regeneration from seed, which is still average of 37 % of the trees were broken abundant in all treatments (on average or uprooted during the two meteoric there are over 20 000 seedlings per events. It should be pointed out, however, hectare), showed a significant correlation that this percentage of damage is mainly with the treatment used. In treatment A the result of that occurring in a single plot (50 reserve trees per hectare), a larger where the diameters of the trees were number of seedlings was noted as com- small (in this plot 75 % of the trees were pared with the other treatments. A higher damaged). The average volumetric loss is proportion of reserve trees, therefore, did 1.59 m. -1 ·ha 3 not make for the emergence of a larger number of seedlings. Most likely, many In both cases, treatments A and B, the reserve trees in the stand have a negative trees belonged to the lowest damaged effect on the survival of the young diameter classes. With respect to the aver- seedlings, due perhaps to excessive shad- age diameter of the trees in the individual ing. Little is known about the performance plots, the damaged trees always had a of holm oak seedlings as a function of the lower diameter. cover made by the canopy of the reserve Damage in the plots where treatment trees, the latter being well spread out and C (reserve trees of different ages) was used stratified - insufficient research has been also was relatively low ( 12 % of the trees), done on this point. Holm oak seedlings with a volumetric loss of 1.39 m . -1 ·ha 3 under cover from deciduous trees seem to The caused the two mete- have a fair resistance because they have damage by oric events in the plots where treatments D the benefit of ample light during the win- and E (conversion to high forest and the ter [3]. As the experimental work proceeds control, in percent) were used was not high a detailed study will be made of the influ- (20 % and 3 %, respectively, of the stand- ence of the canopy of the reserve trees on ing trees). In absolute terms, instead, the the mortality and dimensional develop- loss was of 413 unity (27.38 m for ) -1 ·ha 3 ment of seedlings. the conversion into high forest and of 196 Another interesting fact is the low mor- unity (11.37 m for the control. ) -1 ·ha 3 tality among seedlings emerging in the The height/diameter ratio of the bro- coppice with uneven-aged reserve trees. ken trees ranged from 68 to 75, while that In this connection, certain authors [3, 18, of the trees still standing ranged from 57 to 19] suggest that this form of management
favour the trees; conversion into high forest; and regeneration of holm seems to oak, since cutting the trees releases a large allowing natural evolution to proceed of the acorns capable of germi- unhindered. amount nating and becoming established. Apart from these considerations, this Vegetative regeneration tends to regain study represents a contribution to the task upper-air levels very quickly. By the 2nd of acquiring an exact understanding of sil- year, shoot height will exceed 120 cm, vicultural techniques that are best suited to and contacts between the canopies of the achievement of a specific purpose, and shoots from different stumps are already of the effects of operations conducted in observable. In 2 years time, the shoots will stands. Given the socio-economic condi- be entirely under cover. tions obtained in the tract of country con- Coppices with fewer reserve trees have sidered, it is evident that coppice man- produced a greater number of shoots, the agement for the production of fuelwood latter also having an average diameter and not only constitutes the traditional forest average height greater (though not to any use in these parts but supplies a commod- significant extent) than in other treatments. ity for which there is still a market A coppice with uneven-aged reserve trees demand. produces the lowest number of shoots per stump, and the average diameters will be The holm oak coppice has undoubtedly smaller. been an important component of the At a distance of 2 years from the begin- Gargano landscape since ancient times. of this research, therefore, it seems Coppices consisting of this species have ning that, wherever a smaller number of reserve been in centuries-long equilibrium with trees has been, more shoots have become the environment - indeed, have charac- established and vegetative regeneration terized that environment. For this reason, has resulted in greater increments. Two too, even a partial return to this form of years from coppicing it becomes clear that management is desirable. ’Every forest,’ a high reserve tree-to-coppice ratio makes said Patrone, ’has its story.’ Within the for excessive shading and does nothing to area now declared a national park, it is increase regeneration from seed. essential to respect history and to turn this history to good account. In any case, It may be worth repeating, however, Framework Law No. 394/91, the Parks that the practice of leaving a large number Act, creates incentives for, and in other of reserve trees inevitably entails accept- ways promotes, traditional activities car- ing less rigour in the choice of trees to be ried on by man in the tract of country that left standing; and this can prove highly has been declared a park. dangerous when one considers the dam- age to the coppice caused by poor weather The results show that the holm oak cop- conditions. pice meets all the requirements for con- In conclusion, this study on manage- tinuing with this form of management. options conducted in a holm oak ment The number of reserve trees to be left stand in the Gargano has made it possi- standing should also be governed by the ble, albeit in strictly provisional terms, to shoot-bearing capacity of the stumps and discern differences among the effects of by the abundance and frequency of acorn the respective management practices. production. In this respect, the holm oak has excellent characteristics both in terms The ’coppice problem’ can, as a gen- eral rule, be approached via differing man- of agamic regeneration and in terms of agement formulas: coppice with reserve fruiting.
ACKNOWLEDGEMENTS des recherches récentes, Rev. For. Fr. 40 (4) (1988) 302-313. [9] Ducrey M., Peut-on rendre la yeuseraie moins The authors have all contributed equally to combustible ? Rev. For. Fr. 42, n° spécial the drawing up of this paper. The research has ’Espaces forestiers et incendies’ (1990) been realized with CEE funds MEDCOP pro- 202-206. ject. The operative unit was coordinated by [10] Ducrey M., Quelle sylviculture et quel avenir Prof. Orazio la Marca. Thanks are due to Anto- pour les taillis de chêne vert (Quercus ilex L.) nio Palumbo for his assistance in data collec- de la Région méditerranéenne française? Rev. tion. Sincere appreciation is also expressed to For. Fr. 44 (1)(1992) 12-34. the local government (’Amministrazione [11] Ducrey M., Boisserie M., Recrû naturel dans Comunale di Monte S. Angelo’), the Depart- des taillis de Chêne vert (Quercus ilex L.) à la ment of Forestry (’Ispettorato Ripartimentale suite d’exploitations partielles, Ann. Sci. For. 49 delle Foreste’) and the forest rangers of the (1992) 91-109. Gargano (’Corpo Forestale dello Stato’) for [12] Ducrey M., Toth J., Effects of cleaning and their collaboration. thinning on height growth and girth increment in holm oak coppices (Quercus ilex L.), Vege- tatio 99-100 (1992) 365-376. [13] Ducrey M., Turrel M., Influence of cutting REFERENCES methods and dates on stump sprouting in holm oak (Quercus ilex L.) coppices, Ann. Sci. For. [1]Amorini E., Bruschini S., Cutini A., Fabbio G., 49 (1992) 449-464. Struttura e produttività di popolamenti di leccio [14] Fabbio G., Manetti M.C., Puxeddu M., La lec- in Sardegna. Atti VI Congresso nazionale Soci- ecosistema ’in riserva’. Atti VI Con- ceta: un età italiana di Ecologia, 11-14 September 1996, gresso nazionale Società italiana di Ecologia, Naples, Italy, 1996. 11-14 September 1996, Naples, Italy, 1996. [2] Barbero M., Loisel R., Les Chênaies vertes du [15] Giovannini G., Perulli D., Piussi P., Salbitano Sud-Est de la France méditerranéenne : valeurs F., Ecology of vegetative regeneration after phytosociologiques, dynamiques et potentielles, in macchia stands in central coppicing Italy, Phytocoenologia 11 (2) (1983) 225-244. Vegetatio 99-100 (1992) 331-343. Bernetti G., Selvicoltura [3] speciale, UTET, Hermanin [16] L., Pollini M., Produzione legnosa e Torino, Italy, 1995. Considerazioni sull’ampiezza del paesaggio. Brandini P., Tabacchi G., Modelli di previsione [4] in cedui di leccio, Cellulosa e Carta 2 turno del volume e della biomassa per polloni di lec- (1990) 6-10. cio e di corbezzolo in boschi cedui della La Marca O., Marziliano P.A., Moretti N., Pig- [17] Sardegna meridionale, Comun. Ricerca ISAFA natti G., Dinamica strutturale e floristica in un 96 (1) (1996) 59-69. ceduo di leccio, Ann. Accad. Ital. Sci. For. [5] Bruno F., Gratani L., Manes F., Primi dati sulla XLIV (1995) 235-256. biomassa e produttivita della lecceta di Castel- [18] Merendi A., Boschi cedui e matricinatura, Ri. porziano (Roma): biomassa e produzione di For. Ital. 1-3 (1942) 33-36. Quercus ilex L, Ann. Bot. 35-36 (1976-77) 109-118. [19] Pavari A., Il leccio od elce, Alpe 17 (8) (1930) Canadell J., Rodà F., Root biomass of Quer- 390-398. [6] cus ilex in a montane Mediterranean forest, [20] Pignatti S., Ecologia del paesaggio, UTET, Can. J. For. Res. 21 (12)(1991) 1771-1778. Torino, 1994. [7] Canadell J., Reba M., Andrés P., Biomass equa- [21] Toth J., Ducrey M., Turrel M., Protocole tions for Quercus ilex L. in the Montseny Mas- d’étude du dépressage dans des taillis de Chêne sif, northeastern Spain, Forestry 61 (2) (1988) âges de 4à 25 de leur conver- vert ans en vue 137-147. sion futaiesouche, Station de Sylvicul- en sur [8] Ducrey M., Sylviculture des taillis de Chêne ture méditerranéenne, Avignon, Inra, Docu- vert. Pratiques traditionnelles et probiématique ment n° 19/86, 1986, 26 p.