Knowledge of natural animal behavior is essential for enhancing the protection and artificial breeding of animals. At present, the behavior of the Chinese giant salamander (Andrias davidianus) is studied through interviews with local people or occasional observations under artificial conditions, leading to a lack of systematic records. Thus, most reports are descriptive and lack quantitative analyses. To ascertain the types of reproductive activities and their corresponding time allocations, this study observed the reproductive behavior of A. davidianus using a digital monitoring system for the first time. The results showed that sand-pushing behavior is mainly carried out by the limbs, tail, head, and body of den-dominant males. Showering behaviors included rinsing the trunk, head, and tail. Courtship was composed of a series of behaviors, including standing side-by-side, belly colliding, mounting, mouth-to-mouth posturing, chasing, inviting, cohabitating, and rolling over. After chasing and interlocking with the male, the female discharged her eggs. The oviposition process began at either 02:04 or 04:09, and lasted either 66 or 182 min. Parental care included tail fanning, agitation, shaking, and eating dead and unfertilized eggs, and the durations of these behaviors accounted for 31.74 ± 4.35%, 17.42 ± 4.00%, 3.85 ± 1.18%, and 1.19 ± 0.69% of the entire incubation period, respectively. This paper reveals the characteristics of the reproductive behavior of A. davidianus and provides a scientific basis for the management of its ecological breeding and the conservation of its wild populations.

Soil degradation in low soil humus content karst areas is a serious problem. Humus is composed of a series of polymer organic compounds, with no fixed form, therefore it is difficult to study, especially humin. In this study, 13C CP/MAS NMR was used to study the humic acids (HA), fulvic acids (FA), and humin (HM) components in the soil profiles of carbonate rocks and argillaceous rocks in the Northern Guizhou region. Through the vertical distribution of humus in soil, the transformation mechanism among functional groups of humus was studied. The content of HA and FA in the soil of Zunyi New Area was low, and the humification degree was low. FA was the main HA with simple molecules, which were directly related to the surface vegetation in the area. There may have been some genetic relationship between Aliphatic C and Aromatic C, Aliphatic C and Carboxyl C in the same group of humus. In the phylogenetic relationship of HA, FA, and HM, more transformations existed between HA and FA, and between HA and HM, while the transformations between FA and HM were very rare. This study provides an important scientific basis for the theory of the formation and transformation of soil humus in karst area.