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Rhododendron aureum Georgi is a perennial evergreen dwarf shrub that grows at all elevations within the alpine tundra of northern China. Previous research has investigated the plant communities of R. aureum; however, little information is available regarding interspecific competition and underground soil microbial community composition. The objective of our study was to determine whether the presence of R. aureum creates a unique soil microbiome and to investigate the relationship between R. aureum and other plant species. Our study site ranged from 1,800 to 2,600 m above sea level on the northern slope of the Changbai Mountain. The results show that the soil from sites with an R. aureum community had a higher abundance of nitrogen-fixing bacteria and a higher resistance to pathogens than soils from sites without R. aureum. We emphasize that R. aureum promotes a unique soil microbial community structure that is distinct from those associated with other plants. Elevation and microbial biomass were the main influencing factors for plant community structure. Analysis of interspecific relationships reveals that R. aureum is negatively associated with most other dominant shrubs and herbs, suggesting interspecific competition. It is necessary to focus on other dominant species if protection and restoration of the R. aureum competition is to occur. In the future, more is needed to prove whether R. aureum decreases species diversity in the tundra ecosystems of Changbai Mountain. [ABSTRACT FROM AUTHOR]

The vegetation and soil are mutual environmental factors, soil characteristics, such as chemical properties and microorganism that affect the vegetation occurrence, development and succession speed. In this study, we evaluated the structure of microbial communities of rhizosphere of Cowskin Azalea ( Rhododendron aureum Georgi) populations and compared with non-rhizosphere soils at four sample sites of the Changbai Mountains, China, and analyzed the correlation between chemical properties of soil and microbial communities. The results showed that microbial structure and soil chemical properties are significant superior to non-rhizosphere at all four sample sites. The rhizosphere microorganisms are mainly composed of bacteria, actinomycetes, followed by fungi least. The principal component analysis (PCA) biplot displayed that there are differences between rhizosphere and non-rhizosphere soils for microflora; Through correlation analysis, we found that the bacteria is clearly influenced by pH on the Changbai Mountains, besides pH, other soil features such as NO-N. These data highlight that R. aureum as the dominant vegetation living in the alpine tundra is a key factor in the formation of soil microorganism and improving soil fertility, and is of great significance for the maintenance of alpine tundra ecosystem. [ABSTRACT FROM AUTHOR]

Rhodiola sachalinensis is an endangered species with important medicinal value. We used inter-simple sequence repeat (ISSR) and methylation-sensitive amplified polymorphism (MSAP) markers to analyze genetic and epigenetic differentiation in different populations of R. sachalinensis, including three natural populations and an ex situ population. Chromatographic fingerprint was used to reveal HPLC fingerprint differentiation. According to our results, the ex situ population of R. sachalinensis has higher level genetic diversity and greater HPLC fingerprint variation than natural populations, but shows lower epigenetic diversity. Most genetic variation (54.88%) was found to be distributed within populations, and epigenetic variation was primarily distributed among populations (63.87%). UPGMA cluster analysis of ISSR and MSAP data showed identical results, with individuals from each given population grouping together. The results of UPGMA cluster analysis of HPLC fingerprint patterns was significantly different from results obtained from ISSR and MSAP data. Correlation analysis revealed close relationships among altitude, genetic structure, epigenetic structure, and HPLC fingerprint patterns (R2 = 0.98 for genetic and epigenetic distance; R2 = 0.90 for DNA methylation level and altitude; R2 = –0.95 for HPLC fingerprint and altitude). Taken together, our results indicate that ex situ population of R. sachalinensis show significantly different genetic and epigenetic population structures and HPLC fingerprint patterns. Along with other potential explanations, these findings suggest that the ex situ environmental factors caused by different altitude play an important role in keeping hereditary characteristic of R. sachalinensis. [ABSTRACT FROM AUTHOR]

Land use changes are known to alter soil organic carbon (SOC) and microbial properties, however, information about how conversion of natural forest to agricultural land use as well as plantations affects SOC and microbial properties in the Changbai Mountains of Northeast China is meager. Soil carbon content, microbial biomass carbon (MBC), basal respiration and soil carbon mineralization were studied in five selected types of land use: natural old-growth broad-leaved Korean pine mixed forest (NF); spruce plantation (SP) established following clear-cutting of NF; cropland (CL); ginseng farmland (GF) previously under NF; and a five-year Mongolian oak young forest (YF) reforested on an abandoned GF, in the Changbai Mountains of Northeast China in 2011. Results showed that SOC content was significantly lower in SP, CL, GF, and YF than in NF. MBC ranged from 304.4 mg/kg in CL to 1350.3 mg/kg in NF, which was significantly higher in the soil of NF than any soil of the other four land use types. The SOC and MBC contents were higher in SP soil than in CL, GF, and YF soils, yielding a significant difference between SP and CL. The value of basal respiration was also higher in NF than in SP, CL, GF, and YF. Simultaneously, higher values of the metabolic quotient were detected in CL, GF, and YF soils, indicating low substrate utilization of the soil microbial community compared with that in NF and SP soil. The values of cumulative mineralized carbon and potentially mineralized carbon ( C) in NF were significantly higher than those in CL and GF, while no significant difference was observed between NF and SP. In addition, YF had higher values of C and C mineralization rate compared with GF. The results indicate that conversion from NF into agricultural land (CL and GF) uses and plantation may lead to a reduction in soil nutrients (SOC and MBC) and substrate utilization efficiency of the microbial community. By contrast, soils below SP were more conducive to the preservation of soil organic matter, which was reflected in the comparison of microbial indicators among CL, GF, and YF land uses. This study can provide data for evaluating soils nutrients under different land use types, and serve as references for the rational land use of natural forest in the study area. [ABSTRACT FROM AUTHOR]

Abstract: Old-growth forest ecosystems are large carbon pools, and recent research has found that old-growth forests generally serve as global carbon sinks. However, the impact of climate change on the capacity for carbon sequestration in old-growth forest ecosystems is uncertain. Combining data from 30-year monitoring of permanent plots with that measuring variations in radial growth of dominant trees in an old-growth forest on Changbai Mountain in Northeast China, this study investigated the net biomass carbon sequestration and the effects of climate warming on carbon sequestration for dominant living trees in this forest ecosystem. The results showed that in 2010 biomass carbon density for living trees was 201.22tha−1 in Korean pine and broad-leaved mixed forest (KBF), 106.46tha−1 in spruce-fir forest (SFF), and 89.49tha−1 in Erman’s birch forest (EBF). During the past 30years the net biomass carbon density has increased in KBF and EBF, with annual net increases of 1.79tha−1 and 1.22tha−1, respectively; while net carbon density has decreased in SFF, with an annual net decrease of 0.55tha−1. Despite the increase of carbon density in KBF, climate warming has contributed to a decrease of 0.96tha−1 in biomass carbon sequestration for the period of 1981–2010, an amount equivalent to 1.8% of total stand biomass carbon increase. The increase in net carbon density in KBF was primarily age- or size-related, since that forest is still maturing. The decreased density in SFF may be caused by climate-induced radial growth decline and mortality of dominant trees in these stands. For the period of 1981–2010, climate-induced decrease of carbon sequestration in SFF was 7.30ha−1. Wind-related tree mortality in SFF may have led to the stand carbon sequestration decrease of 75.09tha−1, about 10.3 times that induced by climate warming. In EBF, climate warming has led to a small increase in stand carbon sequestration, and the increase in net carbon density was also primarily age- or size-related, reflecting the fact that this forest is also still maturing. Our study also suggests that the dominance of Korean pine in KBF will decrease and that of Manchurian ash will increase under continuing climate warming, which is in agreement with the results from previous forest models. [Copyright &y& Elsevier]

Rhododendron aureum Georgi (Ericaceae) is a perennial alpine shrub endemic to Changbai Mountain in China. We used ISSR and RAPD markers to describe the diversity and genetic structure within and among four natural populations located at different altitudes. DNA from 66 individuals was amplified with ten ISSR markers and seven RAPD markers. High genetic diversity was observed by these two techniques at the species level. The genetic diversity of populations increased with altitudinal gradients from low to high. The coefficient of gene differentiation (G 0.3652 in ISSR and 0.2511 in RAPD) and AMOVA analysis revealed that most genetic diversity was distributed within populations (61.96% in ISSR and 70.23% in RAPD). The estimate of gene flow based on G was 0.8690 in ISSR and 1.4910 in RAPD. The UPGMA clustering results using ISSR and RAPD showed that all individuals from the same altitude were gathered together, and the two populations (TYD2a and YHLa) from middle altitudes always clustered together. Compared with populations from different altitudes, similar genetic diversity and low genetic differentiation were obtained from populations at the same altitudes, as revealed by ISSR markers. In addition to the reproductive strategy of R. aureum, these data highlight that local environmental conditions may play an important role in shaping the diversity and genetic structure of this species. [ABSTRACT FROM AUTHOR]

Introduction: Long-term ecological studies are essential for understanding the dynamics of natural systems. However, describing long-term dynamics in old-growth forests is often hindered by a lack of archival data. Methods: In this study, we investigated (1) changes in forest structure and tree species composition and (2) population dynamics of the dominant tree species over a 29-year period (1981-2010) in two old-growth forests with stand ages exceeding 200 years on Changbai Mountain in Northeast China. Results: Results showed that the stem density of the broad-leaved/conifer mixed forest at 740 m asl increased slightly from 510 to 515 trees per hectare and the total basal area increased significantly from 36.19 to 46.53 m ha, suggesting that the forest was still maturing over the study period. However, the coniferous forest at 1,680 m asl displayed structural changes in the form of a significantly decrease in both stem density and total basal area over the study period. No changes in tree species composition in the two forests were observed. Discussion: Wind was considered to be a frequent natural disturbance affecting the forest structure and dynamics, especially for the coniferous forest at the higher altitude. Dominant tree species in the two forests exploited different biological characteristics in maintaining their respective populations. [ABSTRACT FROM AUTHOR]