Changes in soil properties and foliage nutrient composition in different age classes of eucalyptus camaldulensis plantation

Astudy was carried out on the changes in soil properties and foliage nutrients ofEucalyptus camaldulensis plantation in arid areas to determine the effect of establishingplantations on the fertility of a desert soil and their management. Distributionsof soil organic matter (SOM), nutrients, pH and their influences on growth andfoliage nutrient composition were investigated in a randomly selected blockplantation representing different age classes, namely, 4 years (Y4), 6 years (Y6), 8 years(Yg), 10 years (Y10), 12 years (Y12) and 18 years (Y]g). Height and diameter at breastheight (dbh) of the stand ranged from 9.2 to 25.7 m and 9.4 to 21.5 cm respectively,depending on the age of the stand. Foliage nutrients were in order ofCa>N>K >Mg > P and differed considerably between different ages. Foliage N and P increaseduntil Y12 and decreased afterwards. The other nutrients did not show any clear trendof increasing/decreasing except for Mn and Fe. Changes in canopy size and nutrientmobilisation during tree development were important in foliage nutrientcompositions. This is due to change in biogeochemistry of the soil, particularlythe amount of SOM which increased with increasing age of the stand. Soil organicmatter and nitrogen (NH4-N + NO3-N) were significantly higher in the 0-15 cmlayer compared with the 15-30 cm layer. Soil nutrients were significantly higherin the plantation area compared with the non-planted control plot. Soil pH, PO4-P,Ca, Mg and K concentrations decreased with stand age whereas SOM, NH4-N,NO,-N, Cu, Zn and Mn increased. There was a general decrease in basic cations;however, SOM, NH4-N and NO3-N increased in the soil. The study thus suggestedthat plantations require fertiliser application and/or thinning after 12 years tomanage the problem of nutrient depletion.