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Purpose: Acid rain is a problem of increasing agricultural, environmental, and ecological concerns worldwide. In recent years, coupled studies have been conducted to evaluate impacts of simulated acid rain (SAR) on Latosol in China. However, no efforts have been devoted to investigating which soil parameters are most sensitive to the influences of SAR. In this study, we addressed the issue using the principal component analysis (PCA) and principal factor analysis (PFA) techniques. Materials and methods: A plastic cylinder with a 10-cm inner diameter was used to contain a 20-cm-long Latosol (acidic red soil) column. A total of 24 column spray treatments, namely 6 pH levels (i.e., 2.5, 3.0, 4.0, 4.5, 5.0, and 7.0) × 4 spray periods (i.e., 5, 10, 15, and 21 days) with triplicates, were carried out in this study. The SAR solution was slowly sprayed at a rate of 6 cm min to the top of the column every 24 h. The effluent and soil samples from the columns were collected and analyzed for soil quality parameter contents. These parameters were then analyzed by the PCA and PFA techniques. Results and discussion: Changes in Ca content in the Latosol due to the influences of SAR did not have discernable impacts on soil parameters. In contrast, Mg had fairly good positive correlations with Fe (0.642) and negative correlation with humic acid (−0.644); K had good positive correlations with Mn (0.724) and negative correlation with Fe (−0.703); Fe had good negative correlations with $$ {\hbox{PO}}_4^{3 - } $$(−0.755); Na had fairly good positive correlations with Cu (0.656); Cu had fairly good positive correlations with humic acid (0.638) and good negative correlations with phosphatase (−0.766); Zn had good positive correlations with $$ {\hbox{PO}}_4^{3 - } $$ (0.722); and OM had fairly good negative correlations with $$ {\hbox{PO}}_4^{3 - } $$ (−0.696). Soil cations (i.e., Mg, K, Na, Cu, and Zn) and enzymes (i.e., peroxidase, urease, and amylase) were positively influenced by the SAR, while the most susceptible soil parameters under the SAR stress were in the following order: Mg (91%) > Na (89.61%) > urease (89.6%) > amylase (89%) > Cu (85.2%). Conclusions: Impacts of the SAR on soil cations (i.e., Mg, K, Na, Cu, and Zn) and enzymes (i.e., peroxidase, urease, and amylase) were larger than those of OM and $$ {\hbox{PO}}_4^{3 - } $$ in the Latosol. The most susceptible soil parameters under the influences of the SAR were in the following order: Mg > Na > urease > amylase > Cu. [ABSTRACT FROM AUTHOR]

Agricultural activities are important contributors to the emissions of greenhouse gases. This study ascertained the dynamic emission of nitrous oxide (N2O) from a paddy field under a rice-duck farming system in South China. Two different cultivation and fertilizer treatments, namely, organic fertilizer + ducks (OF+D) and chemical fertilizer + ducks (CF+D) treatments, were employed in this study. Experimental data showed that diurnal variations of N2O emission were highly correlated with the activities of ducklings. The rates of N2O emission were normally increased in the early morning and late afternoon due to the frequent movement of ducklings at these time periods. Our study further revealed that the rates of N2O emission from the paddy field varied with the types of fertilizers used as well as with the stages of the rice growth. In general, the rates of N2O emission were higher for the CF+D treatment than for the OF+D treatment, whereas more N2O was emitted from the paddy field at the tillering stage than at the heading stage. The global warming potential with the use of the organic fertilizer was about 22% lower than with the use of the chemical fertilizer. [ABSTRACT FROM AUTHOR]

Acid rain is a problem of increasing agricultural, environmental, and ecological concerns worldwide. This study investigated impacts of simulated acid rain (SAR) on cation leaching from the Latosol in south China. Latosol is an acidic red soil and occurs in the tropical rainforest biome. Laboratory experiments were performed by leaching the soil columns with the SAR at a pH range from 2. 5 to 7. 0 over a 21-day period. A linear increase in effluent K+ concentration was found at the SAR pH ⩽3. 0, whereas an exponential decrease in effluent Na+ concentration was observed at all levels of the SAR pH. In general, leaching of Ca2+ and Mg2+ from the Latosol increased as the SAR pH decreased. There was a very good nonlinear correlation between the removal of soil K+ and the SAR pH (R 2 =0. 91), a good nonlinear correlation between the removal of soil Mg+2 and the SAR pH (R 2 =0. 83), a fairly good nonlinear correlation between the removal of soil Ca+2 and the SAR pH (R 2 =0. 56), and no correlation between the removal of soil Na+ and the SAR pH (R 2 =0. 06). Our study further revealed that the removal of soil cations such as K+, Ca+2, and Mg+2 can be quantified by the quadratic polynomial equations. In addition, impacts of the SAR on cation leaching depended not only on the SAR pH but also on the original soil pH. [Copyright &y& Elsevier]

Forest ecosystems in an ecotone and their dynamics to climate change are growing ecological and environmental concerns. Phenology is one of the most critical biological indicators of climate change impacts on forest dynamics. In this study, we estimated and visualized the spatiotemporal patterns of forest phenology from 2001 to 2017 in the Qinling Mountains (QMs) based on the enhanced vegetation index (EVI) from MODerate-resolution Imaging Spectroradiometer (MODIS). We further analyzed this data to reveal the impacts of climate change and topography on the start of the growing season (SOS), end of the growing season (EOS), and the length of growing season (LOS). Our results showed that forest phenology metrics were very sensitive to changes in elevation, with a 2.4 days delayed SOS, 1.4 days advanced EOS, and 3.8 days shortened LOS for every 100 m increase in altitude. During the study period, on average, SOS advanced by 0.13 days year−1, EOS was delayed by 0.22 days year−1, and LOS increased by 0.35 day year−1. The phenological advanced and delayed speed across different elevation is not consistent. The speed of elevation-induced advanced SOS increased slightly with elevation, and the speed of elevation-induced delayed EOS shift reached a maximum value of 1500 m from 2001 to 2017. The sensitivity of SOS and EOS to preseason temperature displays that an increase of 1 °C in the regionally averaged preseason temperature would advance the average SOS by 1.23 days and delay the average EOS by 0.72 days, respectively. This study improved our understanding of the recent variability of forest phenology in mountain ecotones and explored the correlation between forest phenology and climate variables in the context of the ongoing climate warming. [ABSTRACT FROM AUTHOR]

• The number of organic phosphate-solubilizing bacteria (PSB) increased with soil TP. • The number of phosphate-solubilizing fungi (PSF) increased with soil carbon content. • The ability to solubilize phosphate was organic PSB > PSF > inorganic PSB. • The organic PSB was the best bacterial group to solubilize phosphate. Some soil bacteria and fungi are known to solubilize phosphates and play an important role in supplying phosphorus (P) to plants. In this study, we characterized the phosphate-solubilizing bacteria and fungi as well as P availability in latosols from southern China under different land use practices. Three different latosols (i.e., red soil, lateritic red soil and laterite red soil), each with four different land uses (i.e., agricultural land, grass land, forest land and orchard land), from Guangdong Province, China, were chosen to determine the amounts of phosphate-solubilizing bacteria (PSB) and phosphate-solubilizing fungi (PSF) and their phosphate solubilizing abilities. Our results show that the amount of available P (AP) increased with the amount of PSB favored in solubilizing organic P (or PSBop), while the amount of PSF increased with the content of soil organic carbon (SOC). The average rates of phosphate solubilization were 28.23% for PSBop, 6.97% for PSF, and 0.16% for PSBip (PSB favored in solubilizing inorganic P). An increase in soil pH decreased the ability of PSB to solubilize phosphate in latosols. This ability occurred in the following order: PSBop > PSF > PSBip. No significant difference in the amount of PSF was observed among the four different land uses for the lateritic red soil and laterite red soil, whereas a profound significant difference was found for the red soil, with the highest number of PSF in the grass land. Reasonable linear correlations between the PSB and the AP and between the PSF and the SOC were obtained and could provide a good reference to characterize soil PSB and PSF. Additionally, PSBop was the best bacterial species to solubilize phosphate in the latosols. [ABSTRACT FROM AUTHOR]

Vertical-flow constructed wetland (VFCW) is an effective alternative for removal of nutrients, heavy metals, and organic pollutants from wastewaters. This study investigated the uptake and removal of total phosphorus (TP) by Cyperus alternifolius from domestic wastewaters in the simulated VFCWs, The total of eight simulated VFCW treatments, including two different substrates, two different wet-to-dry ratios, and with and without C. alternifolius species (2 x 2 x 2 = 8), were utilized for an operation period of two years in this study. Results show that about 1.1 to 1.4 times more TP was removed from the influent with the presence of C. alternifolius as compared to without this plant species. A linear correlation existed between the aboveground biomass and its TP content. An increase in total biomass by 1000 g would result in an increase in TP accumulation in the aboveground biomass by 4.9 g. Large amounts of TP were removed by the substrate adsorption as compared to those by the aboveground biomass. Results suggest that, although substrate adsorption played a major role in TP removal, C. alternifolius uptake was an alternative pathway for further removal of TP from wastewaters in the VFCWs.