Stem water content serves as a pivotal parameter that reflects the plant vitality and maintains their internal water balance. Given the insufficient comprehension regarding the stem water content characteristics and its influencing factors during different stages of the overwintering period, the study focused on Acer truncatum Bunge and developed an Internet of Things (IoT)-based ecological information monitoring system. The system incorporated a proprietary stem water content sensor, allowing non-invasive, in-situ and real time acquisition of stem water content while monitoring diverse environmental parameters. We conducted a detailed elucidation of stem water content variation characteristics and their responses to diverse environmental factors. The results showed: (1) During the overwintering period, stem water content exhibited diurnal variations characterized by \" daytime ascent and nighttime descent\" across the three stages, exhibiting differences in the moment when the stem water content reaches extremal values and daily fluctuations ranges. Stem water content exhibited minimal fluctuations during deciduous and bud-breaking stages but experienced significant freezing-thawing alternations during the dormant stage, leading to an increased daily fluctuation range. (2) The Pearson correlation coefficients between environmental parameters and stem water content varied dynamically across stages. Path analysis revealed that during the deciduous stage, stem temperature and saturation vapor pressure deficit were dominant factors influencing stem water content; during dormant stage, air temperature and saturation vapor pressure deficit directly impacted stem water content; during the bud-breaking stage, the primary parameters affecting stem water content were saturation vapor pressure deficit and stem temperature. The study provides valuable insights into unveiling the water transport patterns within tree stems tissue and their environmental adaptation mechanisms during the overwintering period, aiding in the scientific development of winter management strategies to protect trees from severe cold and freezing damage, while fostering healthy growth in the subsequent year.

The distribution characteristics, sources and ecological risk of thallium (Tl) in the surface sediments of Yangtze Estuary and its adjacent sea were studied. Tl concentrations ranged from 0.369 to 1.197 μg g-1 with an average of 0.674 μg g-1, which was slightly higher than the corresponding background values. Tl concentrations were relatively high in sediments of the south bank of Chongming Island and the Hangzhou Bay mouth, and gradually decreased from inner shelf to outer seas. The variation trend of Tl concentrations was controlled by sediment characteristics, hydrodynamic conditions and sources together. The sediment flux of Tl in the study area was 428.6 t/yr. The Yangtze River, the Yellow River and atmospheric inputs of Tl accounted for 52.7%, 10.5%, and 0.15% of the total sediment flux, respectively. The result of potential ecological index indicated that Tl in surface sediments of the study area had no threat to the ecological environment.