Soil respiration represents the second largest carbon flux, next to photosynthesis of the terrestrial biosphere, and thus plays a dual role in regional and global carbon cycles. However, soil respiration in Asian monsoon forests with high rainfall has rarely been studied. In this study, we continuously measured soil respiration using a 12-channel automated chamber system in a 61-year-old Japanese cedar forest in central Taiwan with annual rainfall greater than 2500 mm. A 4-year (2011–2014) continuous half-hourly dataset was used to quantify the influences of soil temperature and moisture, especially rainfall events, on both total soil respiration (Rs) and heterotrophic respiration (Rh). The annual mean Rs was approximately 10.8 t C ha⁻¹ (ranging from 10.7 to 10.9) t C ha⁻¹, with Rh contributing approximately 74.6% (ranging from 71.7% to 80.2%). Large seasonal variations in both Rs and Rh were primarily controlled by soil temperature. Over 45.8% of total annual rainfall amounts were provided by strong rainfall events (over 50 mm), and over 40% of rainfall events occurred during summers between 2012 and 2014. These strong rainfall events caused rainwater to enter soil pores and cover the soil surface, which resulted in limited soil microorganism activity and, consequently, restricted CO₂ production. The mean Q₁₀ values were 2.38 (ranging from 1.77 to 2.65) and 2.02 (ranging from 1.71 to 2.34) for Rs and Rh, respectively. The Q₁₀ values in this study, which were lower than in global forest ecosystems, may imply that the interannual Rs values observed in this study that were caused by high rainfall were less temperature-dependent than the Rs levels in global forest ecosystems. Both Rs and Rh were negatively correlated with soil moisture, which indicated that the soil moisture levels in the studied forest were usually under saturated conditions. These results also provide the lack of data for respiration in the Asian monsoon region under high-rainfall conditions.

Solvent extraction offers a better option for gallium recovery among many techniques. The liquid–liquid extraction of gallium(III)–copper(II) solution from hydrochloric acid medium using di-2-ethyl-hexylphosphoric acid (D₂EHPA) in kerosene was studied. The effect of the reagent concentration and other parameters on the extraction of gallium(III)–copper(II) was also studied. The stoichiometry of the extracted species of gallium(III) was determined based on the slope analysis method. The maximum extraction efficiency of gallium was 99.9%. The gallium that contained organic phase could be stripped completely by 1 M HCl.

The environmental stresses caused by climate change have become more severe in recent decades, affecting tree growth and physiology. Tropical forests have great potential for global carbon sequestration. However, they suffer from heavy rainfall and prolonged dry periods due to climate change. Swietenia macrophylla King and Melia azedarach L. are economically valuable trees that are widely planted in southern Taiwan. Plantations are exposed to either prolonged dry periods or heavy rainfall within the seasons of tropical monsoon areas. Photo-physiological comparisons may provide information that can improve management of S. macrophylla and M. azedarach plantations in tropical regions. Both species exhibited a midday depression in leaf photosynthesis regardless of the season. The net photosynthetic rate (P N), stomatal conductance (g s), and transpiration rate (E) in the dry season all significantly decreased in both tree species. In addition, M. azedarach used water more efficiently than did S. macrophylla during the dry season, but S. macrophylla had higher P N compared with that in M. azedarach during the wet season. Temperature and vapor pressure deficit influenced P N variation in S. macrophylla and M. azedarach, respectively. Our data suggested that the P N and g s of M. azedarach, but not of S. macrophylla, were linearly correlated during the dry season. The reduction of the leaf area was more sever in M. azedarach than in S. macrophylla, thus preventing water loss more efficiently. M. azedarach adapted to drought by reducing total leaf area and maintaining higher P N, g s, E, and WUE compared with those measured in S. macrophylla during the dry season. M. azedarach is more drought adaptation and more suitable for both humid and semi-humid areas than S. macrophylla, whereas the latter should be limited to more humid areas.

This study examined monthly carbon sequestration of the Himalayan ash (Fraxinus griffithii C. B. Clarke), an important plantation species in Taiwan. From January 2010 to December 2012, data were collected from an F. griffithii plantation in southern Taiwan, which experiences a typical Southeast Asia monsoon climate. To estimate CO₂ sequestration rate, we conducted diurnal measurements of photosynthetic rates and seasonal measurements of photosynthetic light response curves. We also calculated leaf area index to estimate the total leaf area of individual trees. The diurnal variation in photosynthetic rate, stomatal conductance, and transpiration exhibited seasonal and annual differences. The range of net CO₂ assimilation rates was 1.34–8.68 µmol·m⁻²·s⁻¹ in 2010, 1.02–6.60 µmol·m⁻²·s⁻¹ in 2011, and 1.13–4.45 µmol·m⁻²·s⁻¹ in 2012. A single F. griffithii tree sequestrated 12.21 kg·year⁻¹ CO₂ on average. Annual CO₂ sequestration occurred primarily during the summer for all years, averaging 14.89 Mg·ha⁻¹·year⁻¹ for three years. Correlation analyses between various environmental variables and CO₂ sequestration rates indicated that air temperature and soil water content were likely the main factors influencing carbon sequestration of F. griffithii at this study site.

Xylooligosaccharides (XO), derived from the alkaline (NaOH) extractant of Mikania micrantha, were produced using multiple staged membrane separation and enzymatic xylanolysis. Staged nanofiltration (NMX), ultrafiltration (EUMX), and centrifugation (EMX) processes for the ethanol precipitates were conducted. NMX recovered 97.26% of total xylose and removed 73.18% of sodium ions. Concentrations of total xylose were raised from 10.98 to 51.85 mg/mL by the NMX process. Recovered xylan-containing solids were hydrolyzed by the recombinant Paenibacillus xylanase. 68% XO conversions from total xylose of NMX was achieved in 24 hours. Xylopentaose (DP 5) was the major product from NMX and EMX hydrolysis. Xylohexaose (DP 6) was the major product from EUMX hydrolysis. Results of the present study suggest the applicability for XO production by nanofiltration, as NMX gave higher XO yields compared to those from a conventional ethanol-related lignocellulosic waste conversion process.

Afforestation sequesters carbon from atmosphere and thus is a primary strategy for mitigating global warming. To further the development and management of future plantations, this study examined the monthly CO₂ assimilation of four young broadleaf tree species to select the best performer. From December 2010 to December 2011, data were collected from a plantation in southern Taiwan, which experiences a typical tropical monsoon climate. Monthly measurements of diurnal gas exchange revealed that Melia azedarach maintained a high net photosynthesis rate during the dry season, whereas Swietenia macrophylla exhibited a low net photosynthesis rate and stomatal conductance in both the dry and wet seasons. Annual CO₂ assimilation occurred primarily during summer and autumn for all species. We measured leaf area indices and generated analytical models involving light response curves to calculate canopy-level, net assimilation rate. M. azedarach, S. macrophylla, Cassia fistula, and Pterocarpus indicus assimilated 38.15, 9.65, 32.19, and 19.14 kilograms tree^–1 yr^–1 of CO₂ at the canopy level and 52.65, 10.33, 46.35, and 22.59 megagrams ha^–1 yr^–1 at the stand level, respectively. Based on our results, we recommend M. azedarach and C. fistula as the most appropriate plantation tree species for increasing carbon assimilation in monsoon climates.