Stand structure adjustment influences the biomass allocation in naturally generated Pinus massoniana seedlings through environmental factors

Wenchun He; Yu Wang; Xiao Wang; Xiaochen Wen; Tianyi Li; Mengting Ye; Gang Chen; Kuangji Zhao; Guirong Hou; Xianwei Li; Chuan Fan

doi:10.3389/fpls.2022.997795

Stand structure adjustment influences the biomass allocation in naturally generated Pinus massoniana seedlings through environmental factors

Front Plant Sci. 2022 Oct 28:13:997795. doi: 10.3389/fpls.2022.997795. eCollection 2022.

Authors

Wenchun He¹, Yu Wang¹, Xiao Wang¹, Xiaochen Wen¹, Tianyi Li¹, Mengting Ye¹, Gang Chen¹, Kuangji Zhao¹, Guirong Hou¹, Xianwei Li¹, Chuan Fan¹

Affiliation

¹ Sichuan Province Key Laboratory of Ecological Forestry Engineering on the Upper Reaches of the Yangtze River, State Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River, College of Forestry, Sichuan Agricultural University, Chengdu, China.

Abstract

The natural regeneration of seedlings is a key factor for forest succession. Nevertheless, studies explaining the mechanism of growth and biomass allocation in regenerated seedlings after disturbance are lacking. Therefore, we measured the growth, biomass accumulation, and biomass allocation in current-age seedlings of Pinus massoniana after selective logging (logging of competitive trees, LCT; logging of inferior trees, LIT; and unlogged control, CK), and established structural equation models (SEMs) among the spatial structure characteristic indexes of the stand, environmental factors, and biomass allocation in different organs. As compared to the CK, the mingling index (M), uniform angle index (W), opening degree (O), soil organic carbon (SOC), available nitrogen (SAN), available phosphorus (SAP), available potassium (SAK), and bulk density (SBD) significantly increased (p < 0.05), while the competition index (CI) and neighborhood comparison (U) significantly decreased after logging (p < 0.05). After the LCT, seedling branch biomass improved, with an increase in the ground-diameter, crown-root ratio, and seedling quality index. More biomass was allocated to foliage and roots by an increase in the height and height-diameter ratio under the LIT. In the CK, increasing stem biomass helped the seedlings absorb and utilize more light. The Pearson correlation coefficient showed that biomass allocation to organs was independent, and seedlings adopted the strategies of heterogeneous adaptation and growth, thereby resulting in the separation of the allocation patterns among the organs. As per the redundancy analysis (RDA), CI was the main factor in biomass allocation. Environmental factors had direct effects on biomass allocation to organs, while the stand spatial structure characteristic indexes had indirect effects on biomass allocation based on SEMs. In summary, the LCT had significant, albeit indirect, effects on SOC, SAN, and SBD by reducing the CI for the regeneration and growth of seedlings in the stand, which was of great significance to the sustainable development of the forest stand of P. massoniana.

Keywords: Pinus massoniana; biomass allocation; environmental factors; natural regeneration; stand spatial structure characteristic indexes; structural equation models.