PINUS-RADIATA SITE QUALITY STUDY IN THE BASQUE COUNTRY (SPAIN) USING NUTRITIONAL AND PHYSIOGRAPHICAL CRITERIA

Nutrient status in Pinus radiata sites in the Basque Country (Spain) h ave been established. Current-year, 1-year-old needles, and soil sampl es were collected in 7 sites. Needle samples were analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and nitrogen (N). Soil samples were analyzed for pH (H2O), N, P, Ca, Mg, K and aluminiu m (Al). The results indicate differences between sites and needles of different ages. In general, nutrient concentrations in needles are suf ficient for the nutritive requirements, but some low concentrations of Mg and P found in 1-year-old needles, indicate that some trees may sh ow signs of deficiency in the near future. In turn, N concentrations a re, in many cases, higher than those usually found in this species and may originate growth disorders. These concentrations may be related t o NO3- and NH4+ deposition. Soil nutrients are sufficient for trees re quirements, but the levels of K and Mg art low. Soil pH values art not very acid, and the value of the Ca/Al ratio is, in general, near 1. A n arrangement of sites and physiographical and nutritional parameters based on correlation and principal component analysis is also presente d.