Soil properties and tree nutrients on the Tusam (Pinus merkusii) plantations in central Java, Indonesia

抄録

I. IntroductionTusam (Pinus merkusii) is the only pine that occurs naturally in the south of EquatorIn Sumatra, 30 year-old stands with average diameter of 58.5 cm may have a standing volume of 397 m3 ha-1 with a total yield of 814 m3 ha-1. On favorable sites, it can reach heights up to 60 m and DBH of 150 cm (CABI, 2000). Growth apparently varies between sites. In general, tusam grows well on high lands where soil is strongly weathered, well drained, and acidic. Site Index (SI) is used to determine site quality and to estimate potential productivity. Although widely used for predicting productivity, SI has a weakness, i.e. for a given site index, growth of basal area vary between sites. Therefore, it cannot be used to predict what management practices will affect productivity in the short-and long-terms (Richardson et. al., 1999; Skinner et. al., 1999). The objectives of this research are (i) evaluating soil characters and plant nutrient contents; (ii) assessing the relationship among soil, tree nutrition, and tree growth, and (iii) interpreting the results in order to provide information for management practices.II. Material and Methods Research was conducted in tusam plantations belonging to Perum Perhutani (State Forest Enterprises), KPH Pekalongan Timur in Central Java, Indonesia in 7 compartments, namely, compartments 48a, 31a, 55i, 62d, 48d, 58a, and 74d This area is characterized by climate of type A (Schmidt and Ferguson classification) with rainfall of more than 4500 mm/yr; mean annual temperature between 20 to 30°C. The altitude ranges from 100 m to 1200 m asl. In each compartment, three permanent plots were established in the plantations of more than 25 years age. Circular plots were used where plot size varied between 0.04 to 0.20 ha depending on stand density..Diameter at breast height (DBH) of 1.3 m for all trees was measured using a diameter tape (YAMATO, Japan). Height was measured using a Hagameter for 10 dominant or co-dominant trees. In each plot, three soil profiles were excavated and each profile was divided into 3 soil depths: 0-10 cm, 10-30 cm, and 30-50 cm. Undisturbed soil samples were taken by core sampling (± 100 cm3 in volume. After air-drying and sieving with 2mm screen, samples were composited for each soil depth. Needles collected from the third fully expanded mature fascicle from the apex of three dominant/co-dominant trees were composited after drying at 70-80°C and ground. Samples were digested with nitric acid and perchloric acid (Jones, 2001). The relationships among soil, tree nutrition and tree growth were evaluated using the correlation procedure of the SPSS statistical package. III. Result and Discussion3.1. Soil Characteristics and Tree NutritionSoil pH of all sites was strongly acidic, ranging from 4.5 to 5.5. As a result, availability of Al, Cu, Fe, Mn, Zn increased; some nutrients (Al and Mn) however became toxic, whereas availability of major plant nutrients such as N, P, K, Ca, Mg, S declined (Lal, 1997; Jones, 2001). Additionally, many tropical soils have high P-fixing capacity due to low pH and predominance of Fe and Al ions that reduce P availability to plants. Oxisol is dominated by Kaolinites, which has low cation exchange capacity (3 to 8 cmol kg-1) and low inherent fertility. However, CEC in this study was found to be 30 to 40 cmol kg-1 because of the high content of clay and a possibility of some clay minerals 2:1 being present at this soil. Surprisingly, the CEC was slightly lower in the high SI (plot 58a and 74d) than in the low SI. Total base elements and P also were lower in the high SI, but exchangeable cations were high. The results revealed that nutrients availability to plants were high, although total contents were low. As a result, the growth in the high SI was better.