Genetics and analysis of quantitative traits

Geochemical and Hydrological Reactivity of Heavy Metals in Soils

Effect of stand density, canopy leaf area index and growth variables on Dendrocalamus brandisii (Munro) Kurz litter production at Simao District of Yunnan Province, southwestern China

Soil microorganisms provide valuable ecosystem services, such as nutrient cycling, soil remediation, and biotic and abiotic stress resistance. There is increasing interest in exploring total belowground biodiversity across ecological scales to understand better how different ecological aspects, such as stand density, soil properties, soil depth, and plant growth parameters, influence belowground communities. In various environments, microbial components of belowground communities, such as soil fungi, respond differently to soil features; however, little is known about their response to standing density and vertical soil profiles in a Chinese fir monoculture plantation. This research examined the assemblage of soil fungal communities in different density stands (high, intermediate, and low) and soil depth profiles (0–20 cm and 20–40 cm). This research also looked into the relationship between soil fungi and tree canopy characteristics (mean tilt angle of the leaf (MTA), leaf area index (LAI), and canopy openness index (DIFN)), and general growth parameters, such as diameter, height, and biomass. The results showed that low-density stand soil had higher fungal alpha diversity than intermediate- and high-density stand soils. Ascomycota, Basidiomycota, Mucromycota, and Mortierellomycota were the most common phyla of the soil fungal communities, in that order. Saitozyma, Penicillium, Umbelopsis, and Talaromyces were the most abundant fungal genera. Stand density composition was the dominant factor in changing fungal community structure compared to soil properties and soil depth profiles. The most significant soil elements in soil fungal community alterations were macronutrients. In addition, the canopy openness index and fungal community structure have a positive association in the low-density stand. Soil biota is a nutrient cycling driver that can promote better plant growth in forest ecosystems by supporting nutrient cycling. Hence, this research will be critical in understanding soil fungal dynamics, improving stand growth and productivity, and improving soil quality in intensively managed Chinese fir plantations.

Influence of Intraspecific Competition Stress on Soil Fungal Diversity and Composition in Relation to Tree Growth and Soil Fertility in Sub-Tropical Soils under Chinese Fir Monoculture

Chinese fir (Cunninghamia lanceolate [Lamb.] Hook.) is a fast-growing species which is not only important as a timber-supplier, but also as an available sink for carbon (C) storage in biomass. Stand age and density are two critical factors that can determine tree C sequestration as interrelated drivers through natural self-thinning. C. lanceolate were planted using 1-year-old bare-root seedlings at the initial density of 1800 stems ha−1 in a 15-ha montane area of Hunan Province, China in 1987. The plantation was thinned twice 10 and 20 years after planting to leave trees of 437.5 ± 26.6, 675.0 ± 155.2 and 895.8 ± 60.1 stems ha−1 as low, medium, and high densities, respectively. Tree height and diameter at breast height (DBH) were measured every 2 years beginning from 23 years (2009) to 31 years (2018) after establishment, timber volume (TV) and biomass C were estimated accordingly. We did not find any interactive effect of age and density on any variables except for height. Both TV and biomass C increased with stand age or decreased in higher densities. The allometric height-DBH relationship can be fitted by an exponential rising-to-maximum model with higher maximum value over time. The decline of biomass C along density fit with the inverse first-order polynomial model which indicated that at least 1300–1500 stems ha−1 may be needed to maximize TV and biomass C for a longer term over 20 years. Therefore, to control the density to a reasonable level, over 1300 stems ha−1 in a rotation over 20 years old will be practical for tree biomass C in Chinese fir plantations.

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Estimated biomass carbon in thinned Cunninghamia lanceolate plantations at different stand-ages

In order to study the characteristics of soil nutrient elements and the changes in biomass under different densities and soil layers of forest stand, this paper considers Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) density test forests with five densities (A: 1667 trees·ha−1; B: 3333 trees·ha−1; C: 5000 trees·ha−1; D: 6667 trees·ha−1; E: 10,000 trees·ha−1) as the research objects, located in Naxi District, Sichuan Province, China. Eleven soil physical and chemical property indicators, understory vegetation, and litter biomass were measured. The results were as follows: (1) The stand density had a significant effect on the soil nutrient content, understory vegetation, and litter biomass. A low density is conducive to the accumulation of soil organic matter, hydrolytic N, available P, available K, and total Ca. (2) With the increase in soil depth, the contents of soil organic matter, total N, hydrolytic N, and total P decreased gradually; pH and total Ca decreased gradually; and available P showed a trend of decrease-up-decrease. The soil layers had no significant effect on the total K, total Fe, and total Mg concentrations. (3) Low density (density A or B) was found to be beneficial to the growth of undergrowth vegetation and forest trees, the return of nutrients, long-term soil maintenance, and the stable high yield of Chinese fir plantations.

https://www.mdpi.com/2071-1050/11/19/5410/pdf

Aiguo Duan

Papers

Effect of Stand Density and Soil Layer on Soil Nutrients of a 37-year-old Cunninghamia lanceolata Plantation in Naxi, Sichuan Province, China

Aggregation distributions across stand age in provenances of Cunninghamia lanceolata (Lamb.) Hook