Radial Growth Responses to Climate of Pinus yunnanensis at Low Elevations of the Hengduan Mountains, China

The relationship between climate and forest is critical to understanding the influence of future climate change on terrestrial ecosystems. Research on trees at high elevations has uncovered the relationship in the Hengduan Mountains region, a critical biodiversity hotspot area in southwestern China. The relationship for the area at low elevations below 2800 m a.s.l. in the region remains unclear. In this study, we developed tree ring width chronologies of Pinus yunnanensis Franch. at five sites with elevations of 1170–1725 m in this area. Monthly precipitation, relative humidity, maximum/mean/minimum air temperature and the standardized precipitation evapotranspiration index (SPEI), a drought indicator with a multi-timescale, were used to investigate the radial growth-climate relationship. Results show that the growth of P. yunnanensis at different sites has a similar response pattern to climate variation. Relative humidity, precipitation, and air temperature in the dry season, especially in its last month (May), are critical to the radial growth of trees. Supplemental precipitation amounts and reduced mean or maximum air temperature can promote tree growth. The high correlations between chronologies and SPEI indicate that the radial growth of trees at the low elevations of the region is significantly limited by the moisture availability. Precipitation in the last month of the previous wet season determines the drought regime in the following dry seasons. In spite of some differences in the magnitudes of correlations in the low-elevation area of the Hengduan Mountains region, chronologies generally matched well with each other at different elevations, and the differences are not evident with the change in elevation

Tree-ring δ18O from Southeast China reveals monsoon precipitation and ENSO variability

Considerable advances have been made in use of tree-ring delta O-18 for climate reconstructions in Southeast China, the East Asian summer monsoon region. However, the relationships among tree-ring cellulose delta O-18 (delta O-18(cell)), local hydroclimate, precipitation delta O-18 (delta O-18(pre)) and El Nino-Southern Oscillation (ENSO) have not yet been fully resolved. The usual interpretation has been that local hydroclimate influences delta O-18(cell) through both the "amount effect" on delta O-18(pre) and evaporative enrichment, but it cannot fully explain the high inter-site correlation of delta O-18(cell) chronologies or their response pattern to ENSO. In this study, we use a newly-developed delta O-18(cell) chronology of Pinus massoniana from a water-stressed site in Zhejiang province, in combination with another three delta O-18(cell) chronologies in Southeast China, to investigate their climatic implications from a regional perspective. The results show that besides local hydroclimate, delta O-18(pre) is also significantly correlated with delta O-18(cell) but with different effects. Spatially homogeneous delta O-18(pre) variation causes high spatial correlations among delta(18)O(cell )from different sites. Analyses show that ENSO variations are responsible for the large-scale common signals in delta O-18(cell) by modulating delta O-18(pre). Therefore, combining delta O-18(cell) chronologies from different locations can enhance ENSO signals, which provides us new opportunities to reconstruct paleo-ENSO activities. Furthermore, eliminating the part of ENSO signal that is not related to the growing season hydroclimate from delta O-18(cell) can increase the explained variance of observed values. These findings provide a guide for future optimized ENSO and local paleoclimate reconstructions using delta O-18(cell).National Natural Science Foundation of China24 month embargo; published online 6 August 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Ammonia removal from water using sodium hydroxide modified zeolite mordenite

Natural and modified mordenite zeolites were used to remove ammonium ions from aqueous solution and Koi pond water. The zeolite modification was conducted using sodium hydroxide solutions of different strengths at 75 degreeC for 24 h. Langmuir{,} Freundlich{,} Sips{,} and Toth equations with their temperature dependent forms were used to represent the adsorption equilibria data. The Langmuir and its temperature dependent forms could represent the data better than the other models. The pseudo-first order model has better performance than the pseudo-second order model in correlating the adsorption kinetic data. The controlling mechanism of the adsorption of NH4+ from aqueous solution onto the natural zeolite and the one treated with 6 M sodium hydroxide solution was dominated by physical adsorption. The competition with other ions occurred through different reaction mechanisms so it decreases the removal efficiency of ammonium ions by the zeolites. For the treated zeolite{,} the removal efficiency decreased from 81% to 66.9%. A Thomas model can represent the experimental data for both adsorption of ammonia from aqueous solution or from Koi pond water