Dongmei Deng

Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems, but whether species‐richer communities are also more disturbance‐tolerant remains controversial. In this study, we investigated the bacterial communities based on 472 soil samples from 28 forests across China with associated edaphic and climatic properties. We developed two indexes (i.e., community mean tolerance breadth [CMTB] and community mean response asynchrony [CMRA]) to explore the relationship between diversity and community resistance potential. Moreover, we examined this resistance potential along the climatic and latitudinal gradients. We revealed that CMTB was significantly and negatively related to species richness, resulting from the changes in balance between relative abundances of putative specialists and generalists. In comparison, we found a unimodal relationship between CMRA and richness, suggesting that higher biodiversity might not always lead to higher community resistance. Moreover, our results showed differential local patterns along latitude. In particular, local patterns in the northern region mainly followed general relationships rather than those for the southern forests, which may be attributed to the differences in annual means and annual variations of climate conditions. Our findings highlight that the community resistance potential depends on the composition of diverse species with differential environmental tolerance and responses. This study provides a new, testable evaluation by considering tolerance breadth and response asynchrony at the community level, which will be helpful in assessing the influence of disturbance under rapid shifts in biodiversity and species composition as a result of global environmental change.

An auto‐focusing beam with adjustable symmetry is proposed numerically and experimentally. The initial field of the auto‐focusing Lommel Gaussian vortex beam (ALoGVB) consists of the Lommel function and the Gaussian term. When the asymmetry factor ε of the beam approaches zero, the ALoGVB will degenerate into a circular Bessel Gaussian vortex beam (CBGVB). Compared with the CBGVB, the ALoGVB is more diverse. The shape, symmetry, normalized focusing intensity, and focus distance of the ALoGVB can be controlled by flexibly adjusting the asymmetry factor ε and the topological charge n. In addition, the effect of off‐axis vortices on the propagating characteristics of the beam is also discussed. The experiment is in good agreement with the numerical simulation. The results could be beneficial for potential applications in optical trapping or micromachining.

Si(111)-3 × 1-Ag reconstruction at elevated temperatures during Ag adsorption and desorption has been identified for the first time by optical second-harmonic generation (SHG). Si(111)-3 × 1-Ag may be described by an unstable distribution of structures of p1 symmetry. The largest Si(111)-3 × 1-Ag area observed in the range from 500°C to 600°C during Ag desorption from Si(111)-√3×√3-Ag is ascribed to a nearly full Si(111)-3 × 1-Ag surface.