Forest@ (May 2010)
Tree biomass and deadwood density into ageing Turkey oak coppices in Tuscany
Abstract
Recent data from the National Forest Inventory point out the further reinforcement of coppice area under the position of “mature” standing crop or post-cultivation phase, both of them being spread throughout the original cultivation area. Such condition, mainly due to the less profitable fuel wood harvesting, involves also a share of the more productive types, i.e., Turkey oak forests. Here, a diffuse but forced approach among managers is to “wait and see”. The pro-active way of coppice conversion into high forest is otherwise being practiced in the public domain but on much smaller areas. Against management dilemmas, ageing stands growing under medium to good site conditions show a dynamic growth pattern resulting in a high age-related wood matter storage. At the same time, the heavy and prolonged regular mortality occurring in the fully-stocked shoot population builds up high amounts of deadwood, this becoming an attribute of these newly-formed types. Carbon storage is therefore coming to be one of the major tasks attributable to these systems within the post-cultivation phase. Aims of the work are to estimate both densities of living woody mass and standing+lying deadwood without any lower survey limit, given the small-sized stems building up these types; to check deadwood types/living biomass ratios; to survey deadwood decay; to analyse the dynamics of mass storage within the stands. Three case-studies, aged about three times the traditional rotation and different as for location and site-index, were selected at the purpose. Living woody mass density plus standing and lying deadwood per decay class were determined. Living woody mass density, made basically by stem+thick branches (95%), varies within 160 and 310 Mg ha-1. Total deadwood amount ranges from 22 to 30 Mg ha-1, i.e., 9 to 14% of living woody biomass. The lying/standing deadwood ratio is being reversed with ageing from 1/2 to 2/1-3/1. The intermediate decay class is prevailing (60-85%) across the sites. The observed dynamics and the age-related figures as well, suggest the role these types may play in soil conservation, forest recovery and carbon storage. The need of a consistent monitoring of the further post-cultivation progress is stressed to recognize the driving forces acting, the onset of possible limiting factors and feedbacks.
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