Effect of the silvicultural treatment on canopy properties, litter and seed production in beech coppices under conversion to high forest.

摘要

European beech (Fagus sylvatica L.) is widely distributed in Italy where it covers 1035103 ha, mainly concentrated in the mountainous areas at altitudes above 900 m. The major part is represented by high forest often issued from the conversion of coppice woods, which in the past was the silvicultural system most widely applied mainly to provide fire wood. The social changes occurred in the second half of the last century –fire wood market crisis and the increasing importance of environmental issues- enhanced the conversion into high forest of large areas previously managed as coppice by means of different silvicultural treatments and practices. Nevertheless, the environmental benefits of this choice were not adequately investigated. Results of annual measurements (1992-2009) made in a beech coppice stand aged 65 are here reported. The study area is located on the Alpe di Catenaia, a pre-Apennine outcrop close to Arezzo (Central Italy). Variables strictly related to stand productivity and dynamics such as annual litter and seed production, leaf area index (LAI) and transmittance (PAR) were measured in the research area of Buca Zamponi to estimate the effects of two theses, natural evolution (TEST) and conversion into high forest (DIR). Three thinnings were undertaken in the latter thesis in 1972, 1987 and 2002. Additional theses of natural evolution (CONTR) and advance seed cutting (TS) were added in 2002 in a nearby study area (Eremo della Casella). Results showed the high productivity of coppice stands, under conversion to high forest, with mean values of annual total litter, leaf litter and leaf area index of 5 Mg ha-1, 3 Mg ha-1 and 6 m2m-2, respectively. These findings confirm both the prompt response of beech to intensive thinning cycles and the reliability of undertaking coppice conversion into high forest. Furthermore, the positive trend observed in the ecological parameters and the high consistency of leaf fraction, highlight the still juvenile phase in progress in these stands. These results will be investigated further because of their significance in stands aged over 60. The applied silviculture produced positive outcomes in all the tested theses. Annual total litter, leaf area index and transmittance showed significant differences comparing DIR and TEST. The gap tends to vanish within 8-10 years after thinning occurrence. Seed cutting (TS) produced on the contrary heavy and lasting differences compared with all the theses. Leaf area index and transmittance were 1.97 m2m-2 and 24.8 % in TS vs. 4.22 m2m-2 and 7.89% in DIR. Seed cutting increased also the development of stand canopy and hastened seed production. The amount of seed production in TS was higher than in DIR representing 25% of total litter production. The DIR thesis resulted to be more appropriate for coppice conversion into high forest. Silvicultural practices hasten the conversion process and allow both ecological and economic returns throughout the conversion cycle by the repeated intermediate harvestings that amount to 250-300 m3ha-1 at the age of 60. A 15 yrs timeis recognized as the optimal interval between moderate to heavy thinnings. The complementary thesis of undertaking an advance seed cut (TS) relies more on management planning criteria than on ecologically-based issues. st1:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabella normale"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}.