Dinamics of phytocoenoses and regeneration in the conditional clear cutting of the mesophyte herbs subtaiga larch forest of East Khentey, Mongolia

The article presents the results of a 40 years study of the reforestation of undergrowth and the dynamicsof the plant community after conditionally clear cutting of the larch forest of Eastern Khentey. In the conditionally clearcutting of the mesophyte herbs subtaiga larch forest the regenerative succession goes through 5 serial stages: 1) Herbssheep fescue community (2–6 years), 2) Grass-herbs-sheep fescue community (8–15 years), 3) Sedge-sheep fescue-herbsbirch-larch young stands (22–28 years old), 4) Sheep fescue-herbs larch-birch young stands (37 years old), 5) Grass-herbsbirch-larch young stands (40 years old).

Wildfire Alters the Linkage Between Total and Available Soil C:N:P Ratios and the Stoichiometric Effects on Fine Root Growth in a Chinese Boreal Larch Forest

Background and aimsWildfire is a primary driver of ecosystem functioning, and the fire-induced changes in the cycling and balance of multiple nutrients may influence the response of plant growth to burning. However, the relationships between total and available soil stoichiometry and stoichiometric effects on the growth of fine roots following fire in forests remain unclear.MethodsWe measured the total and available soil C, N and P concentrations, their ratios and fine root biomass (FRB) at an unburned control, 1-year-postfire and 11-year-postfire sites in a Chinese boreal larch forest. The relationships between soil stoichiometry and FRB were analyzed.ResultsWildfire significantly reduced the total and available soil C:N:P ratios and FRB immediately postfire. Eleven years postfire, most indicators recovered to the pre-fire levels except total soil C:P and N:P ratios, and available C:N ratio. Wildfire immediately increased the correlations between total and available soil C:N:P ratios, as well as between FRB and soil C:N:P ratios, but reduced the correlations between FRB and soil nutrient supply. These effects became weaker over time.ConclusionsThe effects of wildfire on biogeochemical processes in boreal ecosystems extend to the relationships between total and available soil stoichiometry. Wildfire strengthens the linkage between fine roots and soil stoichiometry, but weakens the effects of soil nutrient supply in the Great Xing’an Mountains. Therefore, the effects of wildfire on the coupling of soil C, N and P cycling can produce a more complex soil-plant interaction in the postfire early succession stage of boreal larch forest.

The relationships among structure variables of larch forests in China

Background Larch (Larix Mill.) forests are widely distributed in the upper parts of mountainous areas in China, playing vital roles in constructing mountain landscapes and maintaining mountain environments. Despite their importance, our knowledges on the large-scale patterns of structure characteristics and the relationships between different structure variables are unclear. In this paper, we investigated 155 plots from 11 natural larch forest types across the country to explore the biogeographic patterns of the structure characteristics and the allometric relationships between different structure variables for Chinese larch forests. Results The structure characteristics were significantly different among larch forest types. For different larch forest types, the power function fits the relationships between tree height and diameter at breast height (DBH), average DBH and stem density, and taper and stem density well, but with different exponents among larch forest types. The power exponents of the allometric relationships between tree height and DBH for different larch forest types varied from 0.61 to 0.93 (mean = 0.86) by standard major axis regression (SMA), and from 0.51 to 0.78 (mean = 0.56) by ordinary least square regression (OLS). The 50%, 75% and 95% quantile regression (QR) and OLS indicated that the average DBH and taper of the L. gmelinii forests, L. gmelinii var. principis-rupprechtii forests, and L. sibirica forests were significantly correlated with stem density. Conclusions The relationship between tree height and DBH showed a power function relationship for all larch forest types in China, but with different exponents. Overall, stem density was negatively correlated with average DBH and taper. The Sect. Larix forests exhibited stand density effect. Our findings provide an important basis for recognizing the biogeographic patterns of structure factors and for the management of larch forests in China.

Distribution diversity of fungi and bacteria communities in the pure plantation of Larix gmelinii and Fraxinus mandshurica

BackgroundLarix gmelinii （larch）and Fraxinus mandshurica （ash）are two important tree species in northeast China and are infected by Ectomycorrhizal fungi and arbuscular mycorrhizal fungi, respectively.MethodUsing the high-throughput sequencing method, we analyzed the composition of Fungi and bacterial communities in the roots, Rhizosphere, and Non-rhizosphere soil of 21-year-old larch and ash pure plantations. Furthermore, we also analyzed the impact of soil environmental factors on the Fungi and bacterial community diversity according to soil nutrition. ResultsThere were differences in the fungal community diversity between larch and ash. Ascomycota increased gradually from the larch root to non-rhizosphere soil, whereas Streplophyta decreased sharply from the larch root to non-rhizosphere soil. However, the trend of Basidiomycota and Streplophyta under the ash forest was opposite to that of the larch. At the same time, it was found that Larix , Pyronemataceae _Unclassified, Cenococcum , and Ulmus were endemic to larch, whereas Anemone and Monographella were endemic to ash. The bacteria were similar under larch and ash forest. Proteobacteria decreased gradually from rhizosphere to non-rhizosphere soil, and the relative abundance of Acidobacteria , Actinobacteria , Chloroflexi , Rokubacteria , Gemmatimonadetes , Firmicutes, and Nitrospirae were the lowest in the roots of the two species. Pseudomonas , one of the Plant Growth-Promoting Rhizobacteria（PGPR）, had high relative abundance in the roots of the two tree species. The fungal and bacterial communities in the root, rhizosphere soil, and non-rhizosphere soil of the same tree species were different. The distribution diversity of the fungal and bacterial community of larch was non-rhizosphere soil > rhizosphere soil > root. The bacterial community diversity of the ash rhizosphere soil was the highest, whereas the fungal community diversity in the root was the highest. The Larix , the special fungus in the larch, were mainly distributed in the root and decreased sharply outside the root. The Pyronemataceae _Unclassified, Cenococcum, and Ulmus were mainly distributed in the rhizosphere soil. The special fungi of ash were mainly distributed in the rhizosphere. Burkholderiaceae -Unclassified, one of the PGPR, was mainly distributed in the roots of larch, but it was the opposite in the ash. Bacillus and Paenibacillus existed widely in the rhizosphere soil of ash. However, the abundance of Paenibacillus in larch was low, and it gradually increased from the root to the outside. The relative abundance of Streptomycetaceae _Unclassified was slightly high in the larch non-rhizosphere soil and ash rhizosphere soil. There was a correlation between PGPR and some fungi under the two tree species. Among them, Bacillus had a significant synergistic effect with Mortierella and Mucor under larch forest. There was a positive correlation between total nitrogen and bacteria in rhizosphere soil under larch forest, and its content was significantly higher than that of other treatments. There was a positive correlation between total phosphorus and fungi in ash rhizosphere soil, and the content was significantly lower than that in non-rhizosphere soil. However, the relationship between soil fungi and bacteria to soil nutrients was not significant.ConclusionTherefore, compared with the bacterial community, endomycorrhizal tree species have greater differences in the fungal community. The diversity of fungal and bacterial communities in ectomycorrhizal trees increase from rhizosphere soil to non-rhizosphere soil, while the diversity of fungal communities in endomycorrhizal trees is the highest in roots.