Natural regeneration is an essential component of forest dynamics and the recovery of ecosystem functions. Therefore, understanding regeneration status, and how abiotic and biotic factors affect it, is important for ecological studies. This study discovered different regeneration statuses of tropical forests in response to differences in rainfall in Myanmar, and the environmental and overstory factors that had the most influence on understory regeneration. Study sites were set up in regions with 625 to 2035 mm of annual rainfall, and ecological characteristics were measured. According to the results, natural regeneration increased with rainfall, showing a good regeneration status at all sites. Forests within a range of 1411–2035 mm of annual rainfall had a significantly higher density and species diversity at specific natural regeneration stages than those with 625–1029 mm. Not only abiotic but also overstory structure affected the natural regeneration of forests. However, not all factors influenced natural regeneration status. Overstory size distribution parameters did not show a significant influence on natural regeneration. Average annual rainfall (abiotic), as well as ecosystem complexity, density, species richness, and diversity (overstory), were found to be the most influential factors for the density and diversity of natural regeneration. The results of this study will support silviculture and the management of tropical forests.
Global warming and ozone (O3) pose serious threats to crop yield and ecosystem health. Although neither of these factors will act individually in reality, most studies have focused on the responses of plants to air pollution or climate change. Interactive effects of these remain poorly studied. Therefore, this study was conducted to assess the effects of optimal (22/20 °C day/night) and elevated temperature (27/25 °C) and/or ambient (10 ± 10 nL L−1) and elevated O3 concentrations (100 ± 10 nL L−1) on the growth, physiology, and reactive oxygen species (ROS) accumulation of leaf mustard (Brassica juncea L.). The aim was to examine whether elevated temperature increase the O3 damage due to increasing stomatal conductance, and thus, O3 flux into the leaf. Significant reductions in photosynthetic rates occurred under O (elevated O3 with optimal temperatures) and OT (elevated O3 and temperature) conditions compared to C (controls). Stomatal conductance was significantly higher under T than in the C at 7 DAE. Under OT conditions, O3 flux significantly increased compared to that in O conditions at 7 days after exposure (DAE). Significant reductions in total fresh and dry weight were observed under OT conditions compared to those under O. Furthermore, significant reductions in levels of carotenoids and ascorbic acid were observed under OT conditions compared to O. Lipid peroxidation and accumulation of ROS such as hydroxyl radical, hydrogen peroxide, and superoxide radical were higher under O and OT conditions than in C conditions at 7 and 14 DAE. As a result of O3 stress, the results of the present study indicated that the plant injury index significantly increased under OT compared to O conditions. This result suggested that elevated temperature (+5 °C) may enhance O3 damage to B. juncea by increasing stomatal conductance and O3 flux into leaves.
Plants can undergo external fluctuations in the natural light and dark cycle. The photosynthetic apparatus needs to operate in an appropriate manner to fluctuating environmental factors, especially in light. Yellow-poplar seedlings were exposed to nighttime artificial high-pressure sodium (HPS) lighting to evaluate night light-adaptation strategies for photosynthetic apparatus fitness relative to pigment contents, photosystem II photochemistry, photosynthetic parameters, histochemical analysis of reactive oxygen species, and plant biomass. As a result, seedlings exhibited dynamic changes including the enhancement of accessory pigments, the reduction of photosystem II photochemistry, increased stomatal limitation, downregulation of photosynthesis, and the decreased aboveground and belowground biomass under artificial night lighting. Histochemical analysis with 3,3′-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) staining indicates the accumulation of in situ superoxide radicals (O2−) and hydrogen peroxide (H2O2) in leaves exposed to the lowest level of artificial night lighting compared to control. Moreover, these leaves exposed to artificial night lighting had a lower nighttime respiration rate. These results indicated that HPS lighting during the night may act as a major factor as repressors of the fitness of photosynthesis and growth patterns, via a modification of the photosynthetic light harvesting apparatus.
Home garden is a traditional agroforestry system, which is an ecologically and socio-economically sustainable land use system in West Java, Indonesia. It plays a fundamental role in providing subsistence food and income to local people through a multi-strata structure. Despite the importance of the home garden, which is strongly linked with quality of living, there is still a lack of quantitative data and information. Therefore, we quantified the economic and ecological characteristics of home gardens in the present study to evaluate their diverse roles. In addition, general strategies that are applicable to home gardens in West Java were developed for sustainable management. The results of this study indicated that: (1) large landholding size showed a significantly higher Net Present Value (NPV) than small landholding size when the home gardens were dominated by fruit tree species, (2) species richness, species diversity, and carbon stock did not differ significantly among the different types and sizes of home gardens in West Java, and (3) multi-layered and diverse species composition is considerable for sustainable management of home gardens in terms of income generation and against urbanization and commercialization in West Java, Indonesia. Further studies should be considered for developing a standardized and generalized model that is able to evaluate and quantify the various ecosystem values that are generally acceptable and applicable in rural areas.
Capparis macrantha Souvannakhoummane, Fici & Lanorsavanh sp. nov., a new shrub species characterized by erect or ascending habit, stipular thorns, large lanceolate-elliptic leaves and large flowers in supra-axillary rows, is described and illustrated from the deciduous forest in Nam Kading National Protected Area (central Lao PDR). The new species belongs to Capparis sect. Monostichocalyx Radlk. and is morphologically similar to C. radula Gagnep., a shrub widespread in the Indochinese area, differing in the shorter, straight stipular thorns, larger leaves, larger sepals and petals, higher number of stamens with longer filaments and longer gynophore and ovary. Its affinities with related taxa are discussed and a key is provided for the species of Capparis L. known from Lao PDR. The conservation status of the new species is provisionally assessed as Vulnerable (VU D1).