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• We tested ecophysiological traits in tropical dipterocarp trees and their hybrids. • Parent species traits were passed to their hybrids through introgression. • Drought tolerance was enhanced via crossing with more tolerant species. • Hybridization may enable adaptation to drought induced by climate change. Gene transfer through interspecific hybridization can enhance functions such as growth performance, although its role in the ecophysiological functions of tropical tree species remains unclear. Hybrid seedlings of genus Shorea (Dipterocarpaceae), which dominates the canopy layer, are found in fragmented tropical rainforests in Southeast Asia. To elucidate changes in dipterocarp environmental adaptability due to hybridization, we studied the ecophysiological traits of dipterocarp seedlings including leaf morphology, photosynthesis, and drought tolerance in two parent species (Shorea curtisii and Shorea leprosula) and their hybrids, including F 1 and backcross hybrids. Then, we induced drought stress to investigate drought tolerance in these seedlings. Photosynthetic ability was higher in S. leprosula than in S. curtisii , with the F 1 and backcross hybrids showing intermediate characteristics. By contrast, drought tolerance, as indicated by stem hydraulic safety, cuticle thickness, and leaf mass per area, was higher in S. curtisii , lower in S. leprosula , and intermediate in their hybrids. The leaf turgor loss point decreased in S. curtisii due to osmotic adjustment under drought conditions, which led to lower predawn leaf water potential and higher water absorption ability from drier soil. By contrast, these changes were smaller and drought tolerance was weaker in S. leprosula. The hybrids including backcrosses had higher drought tolerance than S. leprosula , suggesting that gene transfer through introgression may facilitate the acquisition of drought tolerance. Although increased drought stress due to climate change and forest degradation are likely to limit seedling regeneration in S. leprosula , drought-tolerant genes obtained through hybridization with S. curtisii may contribute to its survival. [ABSTRACT FROM AUTHOR]

Abstract: Shorea leprosula is one of the valuable species in the tropical rain forest and it has distributed widely in the lowland tropical rain forest with altitude up to 700 m above sea level. Due to decreasingthe number of forest area, it will affect the sustainability of S. leprosula in the tropical rain forest. Ex situ conservation through establishment of S.leprosula progeny test was one of the best way to evaluate the best genotypes of mother trees (family) in order toset up the breeding program and produce the improved planting stock materials for forest rehabilitation.The research was conducted in Balik Papan Forest Industries (BFI), a Forestry Company in East Kalimantan, Indonesia. A total of 60 open pollinated plus trees have been selected and used for the genetic materials of the study. The progeny test wasplanted in 2009and laid out in randomized completely block design (RCBD), 4-tree line plots/family with 3 replications and at a spacing6 x 3 meter. The result of research showed significant in both high and DBH variable at tα Family5%. The biggest and lowest of DBH growth were the family no. 51018 (2.78cm.year-1 of mean annual increment/MAI) and family no. 51052 (1.66cm.year-1 of MAI). Moreover, the highest and the lowest of height growth were family 51030 (2.6 m.year-1 of mean annual increment/MAI) and 51003 (1.5 m.year-1 of MAI) respectively. Families selected in this research could be used to produce the improved planting stock material for rehabilitation insecondary tropical rain forest [Copyright &y& Elsevier]

Abstract: Soil carbon (C) stocks in forest ecosystems have been widely estimated to a fixed soil depth (i.e., 0–30cm) to clarify temporal changes in the C pool. However, surface elevations change as a result of compaction or expansion of the soil under forest management and land use. On the other hand, the calculation of soil C stocks based on “equivalent soil mass” is not affected by compaction or expansion of forest soil. To contribute to the development of a forest C accounting methodology, we compared changes in soil C stocks over 4years between depth- and mass-based approaches using original soil data collected at 0–30cm depths in young plantations and secondary forests in West Java, Indonesia. Our methodology expanded on the mass-based approach; rather than using one representative value for the mass-based calculation of soil C stocks, we adjusted individual values, maintaining the coefficient of variance in soil mass. We also considered the effect of an increase or decrease in soil organic matter on equivalent soil mass. Both increasing and decreasing trends in soil C stocks became clearer when the mass-based approach was used rather than the depth-based approach. The trends in soil C stocks based on equivalent soil mass were particularly evident in the surface soil layers (0–5cm) and in plantation sites, compared with those for soil profiles including subsurface soil layers (0–30cm) and in secondary forests. These trends in soil C stocks corresponded with temporal trends in litter stocks. We suggest that equivalent mass-basis soil C stock for the upper 30cm of soil be calculated based on multiple soil layers to reduce estimation errors. Changes in soil organic matter mass had little effect on the estimation of soil C stock on an equivalent mass basis. For the development of a forest C accounting system, the mass-based approach should be used to characterize temporal trends in soil C stocks and to improve C cycle models, rather than simpler methods of calculating soil C stocks. These improvements will help to increase the tier level of country-specific forest C accounting systems. [Copyright &y& Elsevier]

Abstract: The impact of selective logging on genetic diversity of two tropical tree species with contrasting breeding systems was examined using direct comparison and simulation methods. Shorea leprosula is a diploid and predominantly outcrossed species, whereas Shorea ovalis ssp. sericea is an autotetraploid species with apomictic mode of reproduction. Direct comparison of adjacent natural and logged-over stands showed reduction of genetic diversity of S. leprosula, but not of S. ovalis ssp. sericea. These results clearly demonstrated that a single logging event would cause the genetic erosion of S. leprosula. However, the apomictic mechanisms and the effects of tetrasomic inheritance of S. ovalis ssp. sericea might be a way of maintaining the level of genetic diversity. These results clearly implied that outcrossing species might be more susceptible to the negative impact of logging on genetic diversity than apomictic species. Simulation studies were conducted using three approaches: (1) simulated-removal of individuals based on diameter size classes; (2) simulated-removal of individuals at random; and (3) simulated-removal of individuals in clump. The simulation study based on the first approach showed that the loss of genetic diversity was higher for the Malayan Uniform System (MUS) compared with the Selective Management System (SMS). This might suggest that SMS is more orientated towards the conservation of genetic diversity. In addition, the simulation study showed that to conserve 100% of the total number of alleles, the tolerable cutting limits of S. leprosula in the 50-ha plot of Pasoh FR should be >85cm diameter at breast height (dbh). Comparison of simulation studies based on the second and third approaches showed that the loss of genetic diversity was more rigorous if logging activities were anticipated through extraction of trees in clump rather than to extract trees at random. Implications of the studies for conserving and managing the tropical forests are discussed. [Copyright &y& Elsevier]