Subjects: Biology >> Botany >> Applied botany submitted time 2023-09-20 Cooperative journals: 《广西植物》
Abstract： The spatial structure evolution of forests in karst areas is a key scientific issue in global forest research. In order to explore the dynamics of spatial structure in karst evergreen and deciduous broad-leaved forests, a study was conducted in the Guolin National Nature Reserve, focusing on a fixed monitoring plot of 2 hm2. Based on data from three surveys conducted in 2007, 2012, and 2017, the dynamics of community spatial structure were analyzed using the spatial structure parameters: individual distribution index (Wi), mixing degree (Mi), and size-number ratio (Ui). The results were as foloows: (1) The univariate distribution of spatial structure parameters revealed that the forest structure gradually shifted towards a slightly clumped distribution state as the stand age increased between 2007 and 2017. The mixing degree was at a level of strong mixing and showed a tendency towards extreme mixing. In terms of the size-number ratio, the stand exhibited a moderate state, shifting towards subdominance as the stand grew. (2) The study of spatial structure for different diameter classes of trees showed that the angle scale, size-number ratio, and mixing degree of trees in diameter classes 1~15 cm gradually increased with stand growth. As the diameter class increased, the values of the size-number ratio showed a decreasing trend while the mixing degree showed an increasing trend. (3) The study of spatial structure for dominant tree species revealed that, during the ten-year period from 2007 to 2017, all five dominant tree species groups exhibited a slightly clumped distribution. The size-number ratio showed a tendency towards subdominance and a moderate distribution state, while the mixing level was at a high degree and gradually shifted towards extreme mixing. The study concludes that the karst evergreen and deciduous broad-leaved forest in Guolin currently exhibits a slightly clumped distribution, a strong degree of mixing, and a tendency towards subdominance. The community is relatively stable, the stand regeneration is in good condition, and the forest is gradually transitioning towards a climax community. The analysis of the dynamic changes in vegetation structure in karst evergreen and deciduous broad-leaved forests is of great significance for predicting the future development and changes of forests.
Subjects: Biology >> Botany >> Plant ecology, plant geography submitted time 2016-05-03
Abstract： Aims Our objectives were to study the distribution of soil organic carbon (SOC) density and its influencing factors in main forest ecosystems in Guangxi province. Methods A total of 345 sample plots were established in Guangxi main forest, and the size of each plot was 50 m �20 m. Based on the forest resources inventory data and field investigation, the SOC storage of Guangxi main forest were estimated. The spatial pattern of SOC density was analyzed by the method of geostatistics, and the main influencing factors on SOC density were also explored by principal component analysis and stepwise regression. Important findings The total SOC storage in Guangxi forest was 1686.88 Tg, and the SOC density reached 124.70 Mg/hm2, which is lower than that of China. The best fitted semivariogram model of SOC density was exponential model in Guangxi forest, and had medium spatial autocorrelation. The Kriging contour map indicated that the high value region existed in northeast of Guangxi, and the low value region existed in northwest Guangxi., which manifested as high value in non-karst region and low value in karst region. The SOC density showed difference in five vegetation types and four soil types, following the sequence of bamboo forest > deciduous broadleaf forest > warm coniferous forest > mixed evergreen and deciduous broadleaf forest > evergreen broadleaf forest, and yellow soil > red soil > lateritic red soil > limestone soil. The environment factors including soil depth, longitude, latitude, altitude were the dominant affecting factors of SOC density in Guangxi forest. And the soil depth was the most influential factor, which was attributed to karst landscape.
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