Understory plants are important components of forest ecosystem productivity and diversity. Compared to biomass models of overstory canopy trees, few are available for understory saplings and shrubs and therefore their roles in estimation of forest carbon pools are often ignored. In this study, we harvested 24 understory species including 4 saplings, 9 tree-like shrubs and 11 typical shrubs in coniferous and broadleaved mixed forest in northeastern China and developed the best fit allometric equations of above- and below-ground and total biomass by species-specific or multispecies using morphological measurements of basal diameter, height and crown area as independent variables. The result showed that single basal diameter, height or crown area had good explanatory power for both species-specific and multispecies (p<0.001). The best-fit models included only basal diameter in sapling and tree-like shrubs, and combinations of crown area, height, and basal diameter in typical shrubs. The logarithmic model was most desired among the 4 model forms of linear, quadratic, multiple linear and logarithmic, for species-specific and multispecies. The models we developed should help the estimation of forest ecosystem carbon stocks, especially for belowground component, and provide tools for quantification of individual species biomass of understory plants.

Sago (Metroxylon spp.) is an important crop in Maluku. This study aims to identify the biodiversity of sago palm and understorey vegetation around sago clumps in Maluku. The research was carried out in six sago area from September 2015 to October 2016. The Sago Plant identification was carried out through the growth phase of sago, i.e. seedlings, saplings, weaning, trunks, and ripening. Vegetation observation was done in radius 100 m2 surrounding sago clumps. The result shows that Metroxylon rumphii Mart type. (Tuni sago), M. sagus Rottb. (Molat sago) and M. Silvester Mart. (Ihur Sago) dominates sago palms area in Seram and Ambon Islands, Maluku. There are significant morphological differences between the types of sago, especially in stem height, midrib width, leaf midrib colour, number of thorns, and flower stalk length, as well as the difference of carbohydrate content. Understorey vegetation of each observation sites diverse consist of 15 families and 20 species. The families that dominate the vegetation under the sago palms are Araceae, Thelypteridaceae, and Athyriaceae. The types of plants from Araceae are taro types and broadleaf, while those from the Thelypteridaceae and Athyriaceae families are types of ferns.

The study was conducted in coniferous and deciduous old growth forests in two forest complexes located in: i) the fenced area of the Popielno Research Station of the Polish Academy of Sciences, with free-living Polish pony [Polish primitive horse (Equus ferus caballus)], and ii) open Maskulińskie Forest District managed (harvested) forest, without horses. The impact of forest animals on ground cover layer as well as on understory shrub layer and undergrowth, in i) area (horses and other forest animals) was compared with the results in ii) area (forest animals without horses). Very significant differences in the understory and undergrowth (above 0,5 m) layer vegetation communities structure between both areas and type of stands were found. The results suggest that the presence of the Polish horse substantially changed the species composition and increased the species diversity of the ground layer and shrub layer both on coniferous forest and in the deciduous forest habitats. The height of the shrub layer trees was lower by 30% in the area with the Polish horse.

Little is known about how differences in water availability within the “super humid” tropics can influence the distribution of understory plant species and the composition of understory plant communities. We investigated variation in the physiological drought tolerances of understory plants and plant communities across a large elevation and precipitation gradient. We established 58 understory plots along a gradient of 400 – 3600 m asl elevation and 1000 – 6000 mm yr-1 rainfall in and around Manu National Park in southeastern Peru. Within the plots, we sampled all understory woody plants and measured three metrics of physiological leaf drought tolerance - turgor loss point (TLP), cuticular conductance (Gmin), and solute leakage (SL) - and assessed how the community-level means of these traits related to mean annual precipitation (MAP) and elevation (in the study gradient temperature decreases linearly and vapor pressure deficit increases monotonically with elevation). We did not find any correlations between the three metrics of leaf drought tolerance, suggesting that they represent independent strategies for coping with low water availability. Despite being widely used metrics of leaf drought tolerance, neither TLP nor Gmin showed any significant relationships with elevation or MAP. In contrast, SL, which has only recently been developed for use in ecological field studies, increased significantly at higher precipitations and at lower elevations (i.e., plants in colder and drier habitats have lower SL, indicating greater drought tolerances). Our results illustrate that differences in water availability may play a strong role in structuring plant communities even in in the wet tropics and highlight the potential for SL assays to be an efficient and effective tool for measuring drought tolerances in the field.