Both evenness and dominant species identity have effects on litter decomposition.

Exploring how interactions between species evenness and dominant species identity affect litter decomposition processes is vital to understanding the relationship between biodiversity and ecosystem functioning in the context of global changes. We carried out a 127-day litter decomposition experiment under controlled conditions, with interactions of four species evenness types (high, medium, low and single species) and three dominant species identity (Leymus chinensis, Serratula centauroides, Artemisia capillaris). After collecting the remaining litter, we estimated how evenness and dominant species identity affected litter mass loss rate, carbon (C) loss rate, nitrogen (N) loss rate and remaining litter C/N directly or indirectly, and assessed relative mixture effects (RMEs) on litter mass loss. The main results are shown as follows. (1) By generalized linear models, litter mass loss rate was significantly affected by evenness after 69-day decomposition; N loss rate was affected by dominant species identity after 69-day decomposition, with treatment dominated by Serratula centauroides being at least 9.26% higher than that dominated by any of other species; and remaining litter C/N was affected by the interactions between evenness and dominant species identity after 30-, 69- and 127-day decomposition. (2) Twenty-three out of 27 RMEs were additive, and dominant species identity showed a significant effect on RMEs after 127-day decomposition. (3) By confirmatory path analyses, litter mass loss rate was affected by dominant species identity directly after 127-day decomposition, and by both species evenness and dominant species identity indirectly which was mediated by initial litter functional dispersion (FDis) after 30- and 69-day decomposition; remaining litter C/N was affected by evenness indirectly which was mediated by initial litter FDis after 127-day decomposition. These findings highlight the importance of evenness and dominant species identity on litter decomposition. The study provides insights into communities during retrogressive successions in semi-arid grasslands in the context of global changes.

Incidence rate and risk factors for suicide death in patients with skin malignant melanoma: a Surveillance, Epidemiology, and End Results analysis.

The purpose of this study was to use the Surveillance, Epidemiology, and End Results database to identify the incidence rate and risk factors for suicide death in patients with skin malignant melanoma (MM) in the USA. We screened cases of skin MM in the SEER database. The balance of covariates between the two groups was examined by the χ-test and Fisher's exact test. Logistic regression was used to identify independent risk factors for committing suicide. A propensity 1: 2 matched analysis was applied to minimize the risk of bias. In total, 103 500 patients with skin MM were included in the study, of whom 623 had died of suicide. The rate of suicide death did not differ significantly between different time intervals. In logistic regression before propensity score matching, age, being divorced, separated, or widowed, receiving radiation or chemotherapy, and the elapsed time since diagnosis were independently associated with an increased rate of suicide death. Only age (P < 0.001) and being in the first year after a diagnosis (P < 0.001) significantly increased the risk of suicide death after propensity score matching. In addition, after the propensity score matching, age was a risk factor for localized, regional, and unstaged, and being the first year after a diagnosis was only a risk factor for regional. It is important to identify and treat people at risk of suicide as early as possible. These results can help clinicians to understand suicidal patients and provide them with appropriate support.

Involvement of NO and ROS in sulfur dioxide induced guard cells apoptosis in Tagetes erecta.

Both nitric oxide (NO) and reactive oxygen species (ROS) are very important signal molecules, but the roles they play in signal transduction of sulfur dioxide (SO2) induced toxicities on ornamental plants is not clear. In this study, the functions of NO and ROS in SO2-induced death of lower epidermal guard cells in ornamental plant Tagetes erecta were investigated. The results showed that SO2 derivatives (0.4-4.0 mmol L(-1) of final concentrations) could reduce the guard cells' viability and increase their death rates in a dose-dependent manner. Meanwhile, the significant increase of cellular NO, ROS, and Ca(2+) levels (P<0.05) and typical apoptosis features including nucleus condensation, nucleus break and nucleus fragmentation were observed. However, exposure to 2.0 mmol L(-1) of SO2 derivatives combined with either NO antagonists (NO scavenger c-PTIO; nitrate reductase inhibitor NaN3; NO synthase inhibitor L-NAME), ROS scavenger (AsA or CAT) or Ca(2+) antagonists (Ca(2+) scavenger EGTA or plasma membrane Ca(2+) channel blocker LaCl3) can effectively block SO2-induced guard cells death and corresponding increase of NO, ROS and Ca(2+) levels. In addition, addition of L-NAME or AsA in 2.0 mmol L(-1) of SO2 derivatives led to significant decrease in the levels of NO, ROS and Ca(2+), whereas addition of LaCl3 in them just resulted in the decrease of Ca(2+) levels, hardly making effects on NO and ROS levels. It was concluded that NO and ROS were involved in the apoptosis induced by SO2 in T. erecta, which regulated the cell apoptosis at the upstream of Ca(2+).

Signal regulation involved in sulfur dioxide-induced guard cell apoptosis in Hemerocallis fulva.

Chronic and acute exposure to SO2 is associated with increased risks of various damages to plants. In the present study, epidermal strip experiment was employed to investigate SO2-induced guard cells apoptosis and the signal regulation in Hemerocallis fulva. The results showed that with the increase of treatment concentrate of SO2 derivates (a mixture of sodium sulfite and sodium bisulfite, 3:1, mmol L⁻¹/mmol L⁻¹, 1.0-5.0 mmol L⁻¹), the physiological activity of the guard cells declined and cell death occurred. While the concentration of SO2 derivatives exceeded 2.0 mmol L⁻¹, the percentage of cell death increased significantly (P<0.05). Typical features of apoptosis including nuclear condensation, nuclear elongation, fragmentation etc. were found. Meanwhile, concomitant presence of nitric oxide (NO), reactive oxygen species (ROS) and Ca²âº level increment appeared. However, SO2-induced cell death can be effectively blocked by either of the following substances with their respective optimal concentrations: antioxidant ascorbic acid (Asc; 0.05 mmol L⁻¹) or catalase (CAT; 200 U mL⁻¹), nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5- tetramethylmidiazoline-1-oxyl-3-oxide (c-PTIO; 0.20 mmol L⁻¹), nitrate reductase inhibitor NaN3 (0.20 mmol L⁻¹), Ca²âº chelating agent EGTA (0.05 mmol L⁻¹) or plasma membrane Ca²âº channel blocker LaCl3 (0.05 mmol L⁻¹). In addition to a significant decrease in cell death rate, a reduction in the levels of reactive oxygen species (ROS), NO and Ca²âº was observed. Further study showed that compared to treatment with SO2 alone, Asc treatment led to a decrease in NO and Ca²âº levels and NaN3 treatment led to a decrease in ROS and Ca²âº levels, but the NO and ROS levels of the LaCl3 treatment changed little. All results suggested that NO, ROS and Ca²âº were involved in the apoptosis induced by SO2 in H. fulva. The process might be related to the burst of NO or ROS, which would activate the plasma Ca²âº channel and result in the increase of intercellular Ca²âº.