Inter-annual variability of net ecosystem productivity (NEP) was assessed by a biometric method observing dynamics of coarse woody organs in a primeval lowland tropical rain forest in Pasoh, Peninsular Malaysia. Yearly changes of NEP estimated by biometric method well agreed with those measured by Eddy Covariance Method (ECM), when we observed a stand within a distance of 125‐150m from the tower for ECM. Annual NEP at a 2-ha stand ranged from -5.0t Carbon ha-1 y-1 to 2.1t Carbon ha-1 y-1 during the last 43 years (1969-2012) with two times depressions. They were caused by man-made and natural disturbances that affected as much as 10% of the 2-ha stand area, and negative NEP was maintained during around 10 years after disturbances. Inter-annual variances of NEP, biomass and necromass of coarse woody debris were evaluated by a mathematical simulation with observed properties of net primary productivity and a death rate of coarse woody organs. Simulated NEP was 0.00±1.52t C ha-1 y-1 under equilibrium regimes, and the variance increased under the conditions of a higher mean death rate leading to decrease of biomass. Basing on variances of NEP, we estimated a turnover time of an equilibrium system at 400 years for a 2-ha stand, which is equivalent to 800ha in area.
Trees in paddy fields characterize the landscape of plain areas in mainland Southeast Asia. Although they play an important role in providing subsistence materials to local communities and in maintaining biodiversity, their distribution patterns are affected during agricultural intensification. In this study, we compared the density and species diversity of trees in two types of paddy fields (i.e., with and without land consolidation) to examine the effects of agricultural intensification on the woody plant community. Aerial photographs and satellite images were used to record changes in land use and tree-unit density from 1975 to 2014 at 18 target sites in three different rural landscapes. Field surveys were conducted in 2015 to investigate the total individual trees, species richness, and individual tree density. Tree species diversity was low at the local scale and varied greatly among sites, resulting in greater diversity at the landscape level. Tree species composition changed, with an increase in the number of ruderal and planted trees. During 1975‐2014, the paddy plot size expanded three times due to land consolidation. As plot sizes increased, the density and species richness of remnant trees in the fields decreased, whereas planted trees on the levees were unaffected. Our results suggest that to enhance biodiversity in paddy fields, there should be a focus on improving the quality of trees planted on the levees. Smartly incorporation of various tree species onto paddy levees, together with appropriate guidelines for management of a paddy field-based agroforestry would be effective for preserving landscape sustainability.
The growth characteristics, anatomical characteristics, and wood properties of Dysoxylum mollissimum, a fast-growing tree species, were investigated. To clarify the effect of radial growth rate on these characteristics and properties, 10-year-old trees planted in Bengkulu, Indonesia were examined and classified into three categories (fast-, medium-, and slow-growing). Xylem maturation type was also evaluated in this species. The mean values of stem diameter, tree height, stem volume, and stress-wave velocity in the 50 measured trees were 18.0cm, 10.6m, 0.119m3, and 3.48km s-1, respectively. Mean values of anatomical characteristics and wood properties in nine selected trees were as follows: vessel diameter, 129µm; vessel frequency, 3.5 vessels mm-2; cell wall thickness of wood fiber, 1.2µm; percentages of vessels, wood fiber, ray parenchyma, axial parenchyma, and cell wall, 8.8, 72.9, 12.4, 5.9, and 33.5%, respectively; vessel element length, 0.36mm; wood fiber length, 1.04mm; basic density, 0.45g cm-3; and compressive strength parallel to the grain in green condition, 29.9MPa. These obtained values were similar to or smaller than previous results obtained in research on other Dysoxylum spp. For almost all of the anatomical characteristics and wood properties, no significant differences among the categories were found. This suggests that the trees with faster radial growth characteristics do not always produce lower quality wood in this species. Judging from the radial variation of anatomical characteristics, the xylem maturation of this species depends on the diameter growth, and it might occur at around 6 to 8cm from the pith.
The anatomical, chemical, and physical characteristics of tension wood were investigated in the commercially important tropical fast-growing plantation species Falcataria moluccana and Acacia auriculiformis. In both cases, pots containing seedlings of the two species were tilted at 50° from a vertical position to promote tension wood formation. During this period, upward bending occurred in the seedlings of both the species. Samples were collected from three different stem positions (lower position, middle position, and upper position). A distinct gelatinous (G-) layer was observed at the lower position in F. moluccana, and lower and middle positions in A. auriculiformis. Compared to normal wood, the anatomical and chemical characteristics, except for the vessel frequency, were significantly different at the lower position in F. moluccana, and at the lower and middle positions in A. auriculiformis, pointing to “typical” tension wood in the inclined stems of both species. Compared to normal wood, the basic density significantly increased at the lower position in F. moluccana, but not in A. auriculiformis. Although a common inclination method was used, the position of the G-layer differed between the two species, suggesting that the degree of response to the inclination stimulus varies among species.