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Biochar has shown potential as a sorbent for reducing Cd levels in water. Euhalophytes, which thrive in saline-alkali soils containing high concentrations of metal ions and anions, present an intriguing opportunity for producing biochar with inherent metal adsorption properties. This study focused on biochar derived from the euhalophyte Salicornia europaea and aimed to investigate its Cd adsorption capacity through adsorption kinetics and isotherm experiments. The results demonstrated that S. europaea biochar exhibited a high specific surface area, substantial base cation content, and a low negative surface charge, making it a highly effective adsorbent for Cd. The adsorption data fit well with the Langmuir isotherm model, revealing a maximum adsorption capacity of 108.54 mg g−1 at 25 °C. The adsorption process involved both surface adsorption and intraparticle diffusion. The Cd adsorption mechanism on the biochar encompassed precipitation, ion exchange, functional group complexation, and cation-π interactions. Notably, the precipitation of Cd2+ with CO32− in the biochar played a dominant role, accounting for 73.7% of the overall removal mechanism. These findings underscore the potential of euhalophytes such as S. europaea as a promising solution for remediating Cd contamination in aquatic environments. [ABSTRACT FROM AUTHOR]

Glycophyte biomass − derived biochars have proven to be effective in the amelioration of acidic soil. However, there is scarce information on the characteristics and soil amelioration effects of halophyte-derived biochars. In this study, a typical halophyte Salicornia europaea, which is mainly distributed in the saline soils and salt-lake shores of China, and a glycophyte Zea mays, which is widely planted in the north of China, were selected to produce biochars with a pyrolysis process at 500 °C for 2 h. S. europaea-derived and Z. mays-derived biochars were characterized in elemental content, pores, surface area, and surface functional groups, and then by using a pot experiment their potential utilizable value as acidic soil conditioner was evaluated. The results showed that compared with Z. mays-derived biochar, S. europaea-derived biochar displayed higher pH, ash contents, base cations (K+, Ca2+, Na+, and Mg2+) contents and exhibited more larger surface area and pore volume than Z. mays-derived biochar. Both biochars had abundant oxygen-containing functional groups. Upon treating the acidic soil, the pH of acidic soil was increased by 0.98, 2.76, and 3.36 units after the addition of 1%, 2%, and 4% S. europaea-derived biochar, while it was increased only by 0.10, 0.22, and 0.56 units at 1%, 2%, and 4% Z. mays-derived biochar. High alkalinity in S. europaea-derived biochar was the main reason for the increase of pH value and base cations in acidic soil. Thus, application of halophyte biochar such as S. europaea-derived biochar is an alternative method for the amelioration of acidic soils. [ABSTRACT FROM AUTHOR]

Key message: We explored topography-dependent variations of spruce (Picea jezoensis var. komarovii) growth in response to climatic change, and abrupt decline in its climatic sensitivities to temperature under global warming in the Changbai Mountain, Northeast China. Variations in the mountain slope direction, being different in radiation intensity and soil moisture, might exert a profound influence on the growth-climate relationship, which potentially brings indeterminacy in sensitivity to temperature under climate warming. To better understand the spatial variation in this influence, we used dendrochronological methods to determine the relationship between the radial growth of spruce (P. jezoensis var. komarovii) and climate in three aspects at an elevation of approximate 1200 m in the Changbai Mountain. The results indicated obvious correlations among the three spruce chronologies, and the radial growth presented more positive correlations with spring temperature (rather than summer or winter temperature), with April temperature on the south-facing slope and negative with precipitation on the north- and west-facing slopes. Despite the sensitivities to temperature were abruptly declined by the increasing temperature, the year- occurrences were inconsistent with records from 1996, 1995 and 1989 on the north (in May), west (in May) and south (in Apr), respectively. The negative relationship with May precipitation has become stronger since 1982 on the north and west for the increasing amount of precipitation. Therefore, given the declined sensitivity of spruce growth to climate warming, which can be shown among three different slopes, the divergent point would be difficult to precisely disentangle in investigating the temporal stability base on the variation in species, habitat and data analytical method. [ABSTRACT FROM AUTHOR]

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid- and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth–climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii (V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce–fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth–climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at all three elevations was influenced primarily by maximum temperature during May (Tmax5) and mean minimum temperature from January to March (Tmin1–3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980. Increase in Tmin1–3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a "divergence problem" of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios. [ABSTRACT FROM AUTHOR]