Population Structures and Dynamics of Rhododendron Communities with Different Stages of Succession in Northwest Guizhou, China

Abstract

To explore the population structures and dynamics of Rhododendron shrub communities at different stages of succession in northwest Guizhou, China, this study examined the populations of Rhododendron annae and Rhododendron irroratum shrub with two different stages. A space-for-time substitution was employed to establish the diameter class/height structures, static life tables, and survival/mortality rate/disappearance rate curves of both Rhododendron populations with different orders of succession. Their structural and quantitative dynamics were analyzed, and their development trends were predicted. The results showed that, quantitatively, the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession were dominated by age classes one, two, and three as well as height classes i, ii, and iii. The number of Rhododendron plants at the three age classes and the three height classes accounted for 97.61–100% of the total. The quantitative dynamic indices of R. annae and R. irroratum were both greater than 0, with and without considering external interference. In terms of age class and height structures, both Rhododendron populations were expanding populations, presenting “inverted-J-shaped” and irregular pyramid patterns. There was a sufficient number of young individuals, but few or no old individuals. Both survival curves of the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession belonged to the Deevy-II type. In the late stage of succession, the mortality curves and disappearance curves of both Rhododendron populations in these communities presented a trend of increasing first and then decreasing with increasing age class. This result indicates that at each age class, R. annae and R. irroratum showed a trend of gradual increase after two, four, and six years. In brief, the populations of R. annae and R. irroratum have rich reserves of seedlings and saplings, but high mortality and disappearance rates. In this context, it is necessary to reduce human interference and implement targeted conservation measures to promote the natural renewal of Rhododendron populations.

Selection of the minimum data set and quantitative soil quality index for different Rhododendron simsii forest communities in southwestern China

“…It features a rare primitive azalea forest belt, which is circular, extending for more than 50 km in length, with a width of 1-5 km, covering an area of approximately 125.80 km 2 (Yu et al 2021;Zhang et al 2023). Within this region, there are approximately 35 species of Rhododendron simsii (including subspecies and varieties), belonging to 6 subgenera, 4 sections, and 9 subsections, with the dominant species being Rhododendron delavayi and Rhododendron irroratum (Zhang et al 2024). The study area has a subtropical monsoon humid climate, with an average annual temperature of 11.8°C and an average annual rainfall of 1181 mm, at an altitude of 1300-2000 m. According to the Food and Agriculture Organization (FAO) soil classi cation system, the predominant soil types are Acrisols and Luvisols, with soil thicknesses ranging from 30-60 cm or more and a surface soil pH ranging from 4.5-6.5 (Tian et al 2020).…”