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Sod culture (SC) and no tillage (NT) are modern orchard management systems, and are two different bases for the sustainable development and production of citrus orchards in Taiwan. However, there is no information about the efficiency of either NT or SC on the photosynthetic physiology of farmed citrus under different seasons and varying light intensities. The objective of this study was to clarify the impacts of SC and NT under eco-friendly farming management on the photosynthetic apparatus of an important plantation citrus species in response to varying light intensities over the seasons. The results showed that Rd (dark respiration rate of CO2), Qy (light quantum yield of CO2), LCP (light compensation point), Amax (maximum net assimilation of CO2), and Fv/Fm values of citrus plants under SC were somewhat higher under NT in the same season, particularly in the fall and in winter. As light intensity increased from 200 to 2000 μmol photon m−2 s−1 PPFD, higher Pn (net photosynthesis rate), Gs (stomatal conductance), ETR (electron transport rate), NPQ (non-photochemical quenching), and Fv/Fm (potential quantum efficiency of PSII) values were observed in spring and summer compared to the fall and winter, and increasing NPQ and decreasing Fv/Fm values were observed in all seasons. Positive and significant correlations were shown between the Pn and Gs under NT and SC in all seasons with all light illuminations, whereas significant and negative relationships were observed between the ETR and NPQ under NT in fall and winter at 1200~2000 PPFD. In short, ETR was useful for non-destructive estimations of Pn and NPQ since these indices were significantly and positively correlated with ETR in citrus leaves exposed to 0~1200 PPFD in all seasons and 1200~2000 PPFD in spring, the fall, and winter, providing a quick means to identify the physiological condition of plants under various seasons and tillages. The precise management of photosynthetic parameters such as ETR in response to light irradiances under varied seasons also provides implications for sustainable citrus production for tillage cropping systems in future higher CO2 and potentially wetter or drier environments. The tillages may hold promise for maximizing the economic efficiency of the growth and development of citrus plants grown in the field.

Blue carbon ecosystems (BCEs) are a promising resource for the mitigation of global warming; however, climate spectrums and anthropogenic activities could influence the fragile balance of BCEs as carbon sinks or sources. We assess how oyster farming affects dissolved inorganic carbon (DIC) and total alkalinity (TA) on CO

This study investigated in-situ the seasonal and diurnal variation of emissions of greenhouse gases (GHGs) from both indigenous and exotic plant species and different environments in the Kaomei Estuary Wetland in central Taiwan with a self-designed non-dispersive infrared monitoring system. This study computed CO2 equivalent (CO2-e) emissions to identify their contribution to global warming. The net primary production and carbon sequestration were then estimated to determine the carbon budget of the coastal estuarine wetland. It concluded that the Kaomei Estuary Wetland functioned as a GHG source and a carbon sink. A significant diurnal variation of GHG emissions was observed, with generally lower daytime CO2 emissions than those at nighttime, while an opposite trend was observed for CH4 and N2O emissions. High solar radiation in the daytime enhanced the CO2 uptake by plant species via photosynthesis, and also accelerated the microbial activities in waters and soil/mud, both resulting in the decrease in atmospheric CO2 concentration. The highest GHG emissions were observed in summer, followed by fall, spring, and winter. Although the concentrations of GHG emissions from the coastal estuarine wetland were in the order as CO2>CH4>N2O, N2O has the highest impact on global warming. Biomass debris played an important role in carbon sequestration, which is stored in soils and muds and stimulated methanogenic bacteria to emit CH4. Tidal fluctuation and sewage discharge brought nitrogen-containing organics to the coastal estuarine wetland, resulting in high emission of N2O from nitrification and denitrification processes. Two vascular plants, Spartina alterniflora, and Phragmites australis emitted more GHGs than the other two plant species. However, the highest GHG emissions from the Kaomei Estuary Wetland was attributed to Bolboschoenus planiculmis due to its largest coverage area. The annual net primary production (NPP) varied mainly with vegetation coverage and season. The exotic Spartina alterniflora had the highest annual NPP compared to the indigenous plant species because of its high nutrient uptake from the soil/mud by its thriving roots.

The Daniaopi free-water surface constructed wetland (DNCW), which treats municipal wastewater and nitrogen removal, was compared between the warm and cool seasons in northern Taiwan from March 2009 to August 2010. The results showed that the nitrogen removal in terms of area removal rates (ARRs) were significantly positively regressed with the area loading rates (ALRs) for ammonia nitrogen (NH 3 -N), nitrite and nitrate nitrogen (NO X ), particulate organic nitrogen (Org-N), and total nitrogen (TN). The ARR of NH 3 -N was 1.69 N g m −2 d −1 during the warm season and 1.51 N g m −2 d −1 during the cool season, whereas the concentration removal efficiency (CRE) was approximately 85% for both seasons. The ARR of TN was 1.77 N g m −2 d −1 during the warm season and 1.32 N g m −2 d −1 during the cool season. The CRE of TN of 67% during the warm season was higher than the CRE of TN of 46% during the cool season. The CRE of TN was lower than that of NH 3 -N, particularly during the cool season, due to the increase in NO X -N and Org-N in the treatment cells. However, the ARR of NH 3 -N and TN were not significantly different between the cool and warm seasons. Our results show that mass loading was a major factor in the nitrogen removal. Atmospheric gains (precipitation minus evapotranspiration) appear to cause an increase in water flow, thereby reducing the loading rate, which reduces the nitrogen removal rate.

Mangroves are recognized as one of the richest carbon storage systems. However, the factors regulating carbon sinks in mangrove ecosystems are still unclear, particularly in the subtropical mangroves. The biomass, production, litterfall, detrital export and decomposition of the dominant mangrove vegetation in subtropical (Kandelia obovata) and tropical (Avicennia marina) Taiwan were quantified from October 2011 to July 2014 to construct the carbon budgets. Despite the different tree species, a principal component analysis revealed the site or environmental conditions had a greater influence than the tree species on the carbon processes. For both species, the net production (NP) rates ranged from 10.86 to 27.64 Mg C ha-1 year-1 and were higher than the global average rate due to the high tree density. While most of the litterfall remained on the ground, a high percentage (72%-91%) of the ground litter decomposed within 1 year and fluxed out of the mangroves. However, human activities might cause a carbon flux into the mangroves and a lower NP rate. The rates of the organic carbon export and soil heterotrophic respiration were greater than the global mean values and those at other locations. Only a small percentage (3%-12%) of the NP was stored in the sediment. The carbon burial rates were much lower than the global average rate due to their faster decomposition, indicating that decomposition played a critical role in determining the burial rate in the sediment. The summation of the organic and inorganic carbon fluxes and soil heterotrophic respiration well exceeded the amount of litter decomposition, indicating an additional source of organic carbon that was unaccounted for by decomposition in the sediment. Sediment-stable isotope analyses further suggest that the trapping of organic matter from upstream rivers or adjacent waters contributed more to the mangrove carbon sinks than the actual production of the mangrove trees.

Field measurements at various wetland ecosystems were conducted to investigate the coefficients b for different scalars in the relaxed eddy accumulation method. These measurements were performed at paddy, marsh and lagoon fields using the eddy covariance system to collect data with a sampling rate of 10 Hz. Without the application of a wind deadband, the mean median values of b were found to be 0.55 for paddy, 0.57 for marsh and 0.56 for lagoon for all scalar quantities under unstable and near-neutral conditions. However, the median values of b under stable conditions steadily increase with stability. The results of estimated b were well described by proposed relationships as a function of the dimensionless stability parameter z / L . Scalar similarity between carbon dioxide, temperature and water vapor showed a distinct diurnal pattern and change within the day where good scalar correlations were observed at paddy and marsh during daytime, but poor scalar correlations were observed at lagoon. With the application of wind deadband, the reductions of the normalized b factors, b REA , related to the increase of deadband values were evaluated and the results were compared with the reported relationships in the literature. The relative minimal variability of the normalized b REA was found when the wind deadband was equal to 0.8. From the diurnal variation of b REA , the relative maximum values of b REA factors occurred around noon, and lower values were observed in the early morning and late afternoon. Daily median b 0 values for various scalars under unstable and neutral conditions over paddy from the beginning to the end of the study period were used to verify the independence of the variations in surface roughness.

Few studies of atmospheric deposition come from the fast growing region of Southeast Asia. Precipitation in Changhua City in central Taiwan was collected to examine its chemical composition and relationship with meteorological patterns. Fifty percent of the precipitation measurements had pH

In a survey of 1992 to 1994, mangrove forests withfour species of true mangroves, Kandelia candel(L.) Druce, Avicennia marina(Forsk.) Vierh.,Rhizophora stylosaGriff., and Lumnitzera racemosaWilld., were found at 22locations in the west coast of Taiwan. The northernrange of their distribution was at Tanshui Estuary(Latitude 25°11′N) and the southern range atTapen Bay (22°28′N). The total area wasestimated to be 286.95 ha. There was an obvious changein species composition and a decrease in speciesnumber of true mangroves from south to north: the fourspecies dominated by A. marinain thesouth and K. candelas thesole species in the north. Air temperature associatedwith sea surface temperature and oceanic currents inwinter, but not soil property, was found to be theprimary environmental factor, affecting the diversityand distribution of true mangroves in Taiwan as wellas in the northeast region of Asia.