The biomass and spatial distribution of root system of dipterocarps in the tropical rain forest.

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 17570020
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Ecology/Environment
• Research Institution: Nara University of Education
• Principal Investigator: KIKUCHI Junichi Nara University of Education, Faculty of Education, Associate Professor (10379521)
• Project Period (FY): 2005 – 2007
• Keywords: dipterocarps / root system / mycorrhiza / biomass / tropical rain forest

Research Abstract

Spatial distribution and biomass of root system of dipterocarp trees were studied in the University forest of Gadja Mada Univ. in Jambi, Sumatera. Annual rain fall in the research area is around 2600 mm, mean temperature is around 28 C.
For the estimation of biomass of- dipterocarp trees, a study plot (1 ha) was established in a mixed dipterocarp forest. A total of 402 trees were mapped and dipterocarp trees occupied 25% of the basal area in the plot. Many rubber trees are also found because this area was long been used as rubber plantation, which protected this area from illegal logging. Other dominant tree families were Myrtaceae, Burseraceae, Sapindanaceae, Euphorbiaceae, Mimosaceae, Rhizophoraceae, Oxalidaceae. Several dipterocarp trees and one Eugenia exceeded more than 1 m diameter at breast height.
Root biomass and spatial distribution was measured for 11 Shorea parvifolia trees. The diameters of sampled trees were 10-75 cm at breast height. For the smaller trees (<20cm), half of roots were excavated and weighed. For the larger trees, about one fourth of the roots were sampled. Root distribution of trees were mostly restricted within 4 to 8 m from the trunk for smaller trees while those of larger trees ranged 12-25m from the trunk. Most of the lateral roots distributed in the upper 80 cm soil layer. The biomass of roots ranged between 3 and 620 kg. The tap and buttress roots accounted the around half of the biomass of the root systems and the ratio of tap roots to lateral roots were high in the smaller trees than the larger tree. The amount of mycorrhizas were quantified for the smallest tree. The biomass of mycorrhizas was very small and ranged 30-1670 g. However, they seems to play important roles in the absorption of nutrients because most of mycorrhizas and fine roots were distributed within the LFH layer where most of the nutrients were released. In the deeper soil layer almost no mycorrhizas were found and amount of fine roots with heavy branching was also rare in the deeper soil.