Fine roots play a prominent role in forest carbon flux, nutrient and water acquisition; however, information on fine roots remains scarce due to the limitation of measuring methods. In this study, a nested regression method was used to estimate the biomass and surface area of fine roots of individual Larix gmelinii trees that dominate northernmost China. Aboveground traits including leaf biomass, leaf area, stem volume and aboveground biomass were also investigated. In particular, the relationships between leaves and fine roots, in terms of biomass and area, were examined. The results revealed that allometric models of fine roots, total roots, and leaves consistently fit well with Adj. R² = 0.92–0.97. The root-shoot ratio at the individual tree level was approximately 0.28. There were robust positive linear correlations between absorption (fine root biomass, fine root surface area) and production (leaf biomass, leaf area) (Adj. R² = 0.95, p < 0.001). In conclusion, the close coupling between fine roots and leaves presented in this study provides support for the theory of functional equilibrium.

Accurate estimates of tree component and aboveground biomass strongly depend on robust and precise allometric equations. However, site-specific and suitable biomass equations are currently scarce for natural Larix gmelinii forests in the western Daxing’anling Mountains, northeastern China. This study aimed to evaluate the biomass allocation patterns within tree components and develop additive allometric biomass equations for species of L. gmelinii. A total of 58 trees were destructively sampled and measured for wood (inside bark), bark, branch and leaf biomass. For each component, we assessed the share of biomass allocated to different components by computing its ratio; we also tested two allometric equations based on diameter at breast height (dbh) alone, and dbh fitted with height (h) as independent variables. Seemingly unrelated regression methodology was used to fit an additive system of biomass allometric equations. We performed an independent dataset to evaluate the predictive ability of the best model system. The results revealed that wood biomass accounted for approximately 60% of the aboveground biomass. Wood and branch biomass ratios increased with increasing dbh, while a reverse trend was observed for bark and leaf biomass ratios. All models showed good fitting results with Adj.R² = 0.958–0.995. Tree dbh provided the lowest estimation errors in the regressions associated with branches and leaves, while dbh² × h generated the most precise models for stems (wood and bark). We conclude that these allometric equations will accurately predict biomass for Larix trees in the western Daxing’anling Mountains.

The superior provenance is a prerequisite for ecological restoration, and a better mastery on the growth rhythms of Ormosia species is fundamental to reforest effectively. For the selection of better provenance and the formulation of artificial cultivation methods, the height and the ground diameter of Ormosia hosiei Hemsl. et Wils., O. xylocarpa Chun ex L. Chen and O. henryi Prain seedlings of different provenances were monitored in the first year. The results showed that their dynamic growths presented a slow-fast-slow trend that fit a “S” growth curve by the logistic mathematical model, and the growth of Ormosia species seedlings of different provenances significantly differed. The accumulated growth increment of O. xylocarpa was the largest (averagely 45.50 cm) and the accumulated growth increment of O. henryi was the least (averagely 20.33 cm). Thus, O. hosiei of Jiujiang provenance, O. xylocarpa of Liping provenance and O. henryi of Longquan provenance have a stronger adaptability for future artificial cultivation in Jiangxi China.

Sarcandra glabra in-forest planting, an anthropogenic activity that may introduce a variety of disturbances into the forest, is being popularly promoted in southern China, while its consequential influences on soil nutrients, as well as the arbuscular mycorrhiza fungal (AMF) community of key forest keystone plants, are still unelucidated, which hampers the assessment of ecological safety and the improvement of agronomic measurements. In this research, topsoil from a 3-year-old Sarcandra glabra planted forest and a nearby control forest were sampled, and the annual variation in the soil nutrients and AMF community of the keystone tree Cunninghamia lanceolata were investigated. Our result showed that the total amount of soil organic carbon of the Sarcandra glabra cultivation group was significantly higher than that of the control group (p < 0.05), which indicated that Sarcandra glabra cultivation significantly enhanced the topsoil carbon storage. Yet, there were only insignificant differences in the Shannon index and Chao index of the AMF community between the two groups (p > 0.05). PCoA analysis found that the compositional differences between two groups were also insignificant. This indicated that Sarcandra glabra cultivation had no significant influence on the diversity and composition of the Cunninghamia lanceolata AMF community. However, we found that the differences in the total amounts of nitrogen and total phosphorus between the two groups were relatively lower in April and September, which indicated the higher nutrient demands and consumption of Sarcandra glabra in these two periods and suggested that a sufficient fertilizer application in these two stages would reduce the potential competition for nutrients between Sarcandra glabra and Cunninghamia lanceolata in order to ensure Sarcandra glabra production and forest health. Lastly, our results reported a total extra income ranging from of CNY 127,700 hm⁻² (7 years of cultivation) to CNY 215,300 hm⁻² (10 years cultivation) provided by Sarcandra glabra in-forest planting, which indicated its powerful potential for mitigating poverty. Our research systematically investigated the annual variation in the soil nutrient content and keystone tree AMF community caused by Sarcandra glabra cultivation and offers constructive guidance for Sarcandra glabra cultivation and fertilization management and ecological safety assessment.