RÉSUMÉ
Shrub is an important part of forest ecosystem. Exploring the species composition, structure and spatial distribution of shrub layer can lay an important foundation for further clarifying the mechanisms underlying species coexistence, biodiversity maintenance and community succession. In this study, species composition, spatial distribution, and species diversity of shrub layer were analyzed in 25 hm2 of Huangguan forest plot. A total of 20716 individual shrubs (with 10463 branches) were recorded in the plot, belonging to 54 species, 45 genera, 28 families. The status of dominant species in the shrub layer was not obvious, with all the importance values being less than 10. The diameter structure of shrub layer vegetation was inverted 'J' type. Shrubs showed aggregated distribution in the plot, with obvious altitude differences in spatial distribution. The diameter structure and spatial distribution of the nine shrub species with the largest abundance in the plot were consistent with the overall situation of shrub layer. With increasing altitude, the Shannon diversity index (H) and Simpson dominance index (D) did not change significantly, while the Pielou evenness index (E) decreased. Those indices decreased with the increases of the abundance of dominant species in tree layer, and E increased with the increase of the number of dominant species in sub-tree layer. The indices of H, D, E were significantly negatively correlated with soil total phosphorus (TP). The H index was significantly positively correlated with soil pH, and the E index was significantly positively correlated with soil total potassium. The shrub layer was rich in species, stable in community structure and well regenerated. The species diversity of shrub layer was mainly affected by the number of dominant species in the tree layer, soil pH, and TP.
Sujet(s)
Écosystème , Forêts , Biodiversité , Chine , Humains , Phosphore , Sol , ArbresRÉSUMÉ
In this study, the spatial distribution patterns of individuals with different diameter classes of dominant shrub Lonicera fragrantissima var. lancifolia and the intraspecific and interspecific relationships were analyzed in Qinling Huangguan Plot. The results showed that the diameter class structure of L. fragrantissima var. lancifolia showed a pyramid shape, with a wide bottom and a narrow top. The number of small-diameter class individuals was the largest, showing a good state of renewal and a stable growth, which was conducive to community renewal and succession. Based on Ripley's K function, using univariate and bivariate paired correlation functions, under complete spatial randomness model, heterogeneous Poisson model and antecedent condition model, all individual of the species and their diameter-dividing classes were mainly aggregated, and the aggregation degree decreased with the increases of research scale, and gradually tended to random distribution. Affected by habitat heterogeneity, diffusion restriction and negative density dependence, there was a positive correlation among different intraspecific dia-meter classes, and also a certain degree of no correlation, but without negative correlation. The interspecific relationship was complex. All types of association (no, positive and negative) were observed, but negative association and no association were dominated.
Sujet(s)
Forêts , Lonicera , Chine , Écosystème , Humains , ArbresRÉSUMÉ
To explore the spatial distribution and intraspecific correlation of Quercus aliena var. acutiserrata, a domi-nant tree species in a 25 hm2 plot of warm temperate deciduous broadleaved forest in Qinling Mountains, the pair-correlation function g(r) was used to study the spatial pattern and intraspecific association. The results showed that the diameter class structure of Q. aliena var. acutiserrata was bimodal, with a large proportion of young trees (1 cm≤DBHï¼5 cm), indicating an increase population structure with good capability of regeneration. The abundance of middle trees (15 cm≤DBHï¼25 cm) was slightly more than that of big trees (25 cm≤DBHï¼35 cm) and old trees (DBH≥35 cm), but far less than that of young trees and small trees. The spatial distribution of Q. aliena var. acuteserrata was obviously altitude dependent, which mainly distributed in the middle and high altitude areas. Results of complete spatial randomness (CSR) model analysis showed that young trees, small trees, adult trees, big trees, and old trees were aggregated in the large scale (ï¼60 m). Heterogeneous Poisson (HP) model was used to eliminate habitat heterogeneity. The results of HP model showed that the individual aggregation degree of each diameter class decreased, indicating that the distribution was affected by habitat heterogeneity. At the small scale (ï¼40 m), spatial correlation was positively correlated between individuals with small diameter gap, whereas the spatial correlation was negative correlation and no correlation between individuals with large diameter gap. At large scale (>40 m), the spatial correlation was positively correlated between large-diameter individuals, but negatively correlated and unrelated between saplings and other diameter individuals. Our results indicated that biological cha-racteristics of Q. aliena var. acutiserrata and habitat heterogeneity were important drivers for the formation of population spatial pattern.
Sujet(s)
Quercus , Chine , Écosystème , Forêts , Humains , ArbresRÉSUMÉ
The Qinling Mountain is a natural boundary between warm temperate zone and subtropical zone. While the China Forest Biodiversity Monitoring Network (CForBio) have basically covered most of the climate regions in China, few plots were located in the climate transition zone. Following the field protocol of CForBio and the Center for Tropical Forest Science (CTFS), a 25 hm2(500 m×500 m) forest plot was established in Huangguan Nature Reserve in Shaanxi Province, China, in 2019. In this study, we analyzed species composition, flora characteristics, diameter class structure, and spatial distribution patterns of dominant tree species based on the data of all woody species with a diameter at breast height (DBH) ≥1 cm. The results showed that there were 75137 woody individuals with DBH ≥1 cm in the plot (95679 when including branching individuals), belonging to 121 species, 83 genera and 44 families. The flora type at the genera level was mainly temperate, accounting for 71.1% of the total genera, and mixed with some tropical components. The dominant species in the community were obvious, with the number of individuals in the top 5 species exceeding 40% of the total number of individuals, the number of individuals in the top 50 species accounting for 95% of the total number of individuals, and the number of individuals in the remaining 61 species being less than 5% of the total. The diameter distribution of all woody indivi-duals in the plot was inverted 'J' type. Spatial distribution patterns varied across the four most abundant species with importance value >5. The degree of aggregation within species decreased with the increases of scales, while the spatial distribution of different species was affected by environmental heterogeneity. Warm-temperate deciduous broadleaved forest in Qinling Mountains had abundant species, stable community structure and good regeneration, reflecting the typical characteristics of the transition from warm temperate zone to subtropical zone. Environmental heterogeneity might be an important factor affecting the spatial distribution of tree species in the plot.
