2.3. Data collection
Essential physical and chemical properties of the Technosols were determined just after the beginning of the experiment (1st year) and six years later (6thyear) for every experimental plot.
Soil sampling consisted in one composite sample per plot resulting from the homogenization of six soil subsamples taken at random from below mulches, then dried and sieved to 2 mm. Moreover, and as reference soil, in three different points in nearby natural undisturbed soil around the quarry, composite samples (also in the surface layer 0-10 cm) were analyzed. Particle-size analysis was performed with the pipette method. The pH was determined in an aqueous solution 1/2 (w/v) in a pH meter (Crison 2002) and the electrical conductivity (EC) in a 1/5 (w/v) aqueous solution in a conductivity-meter (Basic 30, Crison, Carpi, Italy). Total calcium carbonate equivalent was measured with Bernard calcimeter. Total Organic Carbon (TOC) by colorimetric determination using the wet oxidation method (Nelson and Sommers, 1996) and total N, using a LECO Truspec C and N analyzer (St. Joseph, MI, USA).
Despite a monthly visual assessment of pines during the first years of the experiment looking at their growth, the inventory was carried out six years since the establishment of the experimental plots (five since the first seedlings appeared). The number of individuals was counted and their height (length of the main stem) and collar diameter (± 0.01 mm) (Fig. 3). Slenderness index was calculated as the ratio of height and collar diameter. As the amount of pine cones introduced with pine chips mulch was not known, the germination rate of pines per plot could not be considered.
We determined the plant cover, including pines, of planted and spontaneous species. The total cover was calculated as the sum of all of them. The methods used were the transect method for pines and the point-intercept frame, a modification of the method used by Floyd and Anderson (1982), with a 20 cm x 20 cm grid of 400 points arranged in a lattice with 1 cm grid spacing for the spontaneous vegetation; one grid point count represented 1 cm2 of cover. Percent cover for each subplot was determined by aggregating the data from three 400 cm2 sampling points. The diversity of vegetation species was calculated with the Shannon index (H) using the equation:
\begin{equation} H=-\sum_{i=1}^{n}\text{pi\ ln\ pi}\nonumber \\ \end{equation}
where pi is the relative abundance of each vegetal species in the total and n is the number of detected vegetal species. The whole pool of species found was analysed looking for a pattern of species distribution through the plots.