scholarly journals Variations in bacterial communities during foliar litter decomposition in the winter and growing seasons in an alpine forest of the eastern Tibetan Plateau

2016 ◽  
Vol 62 (1) ◽  
pp. 35-48 ◽  
Author(s):  
Yeyi Zhao ◽  
Fuzhong Wu ◽  
Wanqin Yang ◽  
Bo Tan ◽  
Wei He
Keyword(s):  
Tibetan Plateau ◽  
16S Rrna ◽  
Litter Decomposition ◽  
Bacterial Communities ◽  
Seasonal Changes ◽  
Growing Season ◽  
Elemental Content ◽  
Eastern Tibetan Plateau ◽  
Alpine Forest ◽  
Growing Seasons

Bacterial communities are the primary engineers during litter decomposition and related material cycling, and they can be strongly controlled by seasonal changes in temperature and other environmental factors. However, limited information is available on changes in the bacterial community from winter to the growing season as litter decomposition proceeds in cold climates. Here, we investigated the abundance and structure of bacterial communities using real-time quantitative PCR and denaturing gradient gel electrophoresis (DGGE) during a 2-year field study of the decomposition of litter of 4 species in the winter and growing seasons of an alpine forest of the eastern Tibetan Plateau. The abundance of the bacterial 16S rRNA gene was relatively high during decomposition of cypress and birch litter in the first winter, but for the other litters 16S rRNA abundance during both winters was significantly lower than during the following growing season. A large number of bands were observed on the DGGE gels, and their intensities and number from the winter samples were lower than those from the growing season during the 2-year decomposition experiment. Eighty-nine sequences from the bands of bacteria that had been cut from the DGGE gels were affiliated with 10 distinct classes of bacteria and an unknown group. A redundancy analysis indicated that the moisture, mass loss, and elemental content (e.g., C, N, and P) of the litter significantly affected the bacterial communities. Collectively, the results suggest that uneven seasonal changes in climate regulate bacterial communities and other decomposers, thus affecting their contribution to litter decomposition processes in the alpine forest.

Foliar litter decomposition in an alpine forest meta-ecosystem on the eastern Tibetan Plateau

2016 ◽  
Vol 566-567 ◽  
pp. 279-287 ◽  
Author(s):  
Kai Yue ◽  
Wanqin Yang ◽  
Changhui Peng ◽  
Yan Peng ◽  
Chuan Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Litter Decomposition ◽  
Eastern Tibetan Plateau ◽  
Alpine Forest

scholarly journals Critical minimum temperature limits xylogenesis and maintains treelines on the Tibetan Plateau

2016 ◽  
Author(s):  
Xiaoxia Li ◽  
Eryuan Liang ◽  
Jozica Gricar ◽  
Sergio Rossi ◽  
Katarina Cufar ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Tree Ring ◽  
Minimum Temperature ◽  
The Tibetan Plateau ◽  
Climatic Variable ◽  
Eastern Tibetan Plateau ◽  
Growing Seasons ◽  
Tree Ring Data ◽  
Xylem Growth ◽  
Ecological Mechanisms

ABSTRACTPhysiological and ecological mechanisms that define treelines are still debated. It is suggested that the absence of trees above the treeline is caused by the low temperature that limits growth. Thus, we raise the hypothesis that there is a critical minimum temperature (CTmin) preventing xylogenesis at treeline. We tested this hypothesis by examining weekly xylogenesis across three and four growing seasons in two natural Smith fir (Abies georgei var. smithii) treeline sites on the south-eastern Tibetan Plateau. Despite differences in the timing of cell differentiation among years, minimum air temperature was the dominant climatic variable associated with xylem growth; the critical minimum temperature (CTmin) for the onset and end of xylogenesis occurred at 0.7±0.4 °C. A process-based-modeled chronology of tree-ring formation using this CTmin was consistent with actual tree-ring data. This extremely low CTmin permits Smith fir growing at treeline to complete annual xylem production and maturation and provides both support and a mechanism for treeline formation.

scholarly journals Intra-Seasonal Changes in Height to Diameter Ratios for Lodgepole Pine in the Central Interior of British Columbia

2003 ◽  
Vol 18 (1) ◽  
pp. 52-59 ◽  
Author(s):  
Christopher Opio ◽  
Kona van Diest ◽  
Norman Jacob
Keyword(s):  
British Columbia ◽  
Repeated Measures ◽  
Seasonal Changes ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Growing Season ◽  
Diameter Ratio ◽  
Rate Of Change ◽  
Growing Seasons ◽  
Four Levels

Abstract Height to diameter ratio (HDR) has been proposed as an alternative to conventional procedures for assessing competition between crop trees and other vegetation. Yet HDRs vary throughout the growing season due to variations in the rate of change in height and diameter. There is an interest, therefore, in determining variations in HDR within a growing season (intra-seasonal changes) and the time of the year when measurements of HDR should be taken for operational purposes. HDR measurements were taken on five occasions at two lodgepole pine (Pinus contorta var. latifolia) sites in the central interior of British Columbia, from early May to late October through the 1999 growing season. Although the focus of the article is the investigation of intra-seasonal changes in HDR, we also compared August 1999 measurements with August 1998 measurements to determine the variation in HDR between growing seasons (inter-seasonal change). The study involved a completely randomized, one-factor experimental design, with replication over time. The removal of competing vegetation (known as brushing) was the factor. The design consisted of four levels of brushing, replicated three times on each study site. The results indicated that HDRs increased from early May to July and then decreased until October to levels equal to or lower than those obtained in August 1998. The highest HDR values were observed in control plots. The analysis of variance (ANOVA) with repeated measures indicated that treatment (brushing radius) and date of HDR measurement had significant (P < 0.05) effects on the intra-seasonal changes in HDR. The results suggest that HDR measurements should be taken either after mid-August, or before mid-May when changes in HDR are negligible. West. J. Appl. For.18(1):52–59.

scholarly journals Successional Trajectories of Rhizosphere Bacterial Communities over Consecutive Seasons

mBio ◽  
2015 ◽  
Vol 6 (4) ◽  
Author(s):  
Shengjing Shi ◽  
Erin Nuccio ◽  
Donald J. Herman ◽  
Ruud Rijkers ◽  
Katerina Estera ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Growing Season ◽  
Avena Fatua ◽  
Plant Roots ◽  
Annual Grass ◽  
Phylogenetic Conservation ◽  
Growing Seasons ◽  
Rhizosphere Competence ◽  
The Many ◽  
Rhizosphere Bacterial Communities

ABSTRACT It is well known that rhizosphere microbiomes differ from those of surrounding soil, and yet we know little about how these root-associated microbial communities change through the growing season and between seasons. We analyzed the response of soil bacteria to roots of the common annual grass Avena fatua over two growing seasons using high-throughput sequencing of 16S rRNA genes. Over the two periods of growth, the rhizosphere bacterial communities followed consistent successional patterns as plants grew, although the starting communities were distinct. Succession in the rhizosphere was characterized by a significant decrease in both taxonomic and phylogenetic diversity relative to background soil communities, driven by reductions in both richness and evenness of the bacterial communities. Plant roots selectively stimulated the relative abundance of Alphaproteobacteria, Betaproteobacteria, and Bacteroidetes but reduced the abundance of Acidobacteria, Actinobacteria, and Firmicutes. Taxa that increased in relative abundance in the rhizosphere soil displayed phylogenetic clustering, suggesting some conservation and an evolutionary basis for the response of complex soil bacterial communities to the presence of plant roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence. IMPORTANCE We document the successional patterns of rhizosphere bacterial communities associated with a “wild” annual grass, Avena fatua, which is commonly a dominant plant in Mediterranean-type annual grasslands around the world; the plant was grown in its grassland soil. Most studies documenting rhizosphere microbiomes address “domesticated” plants growing in soils to which they are introduced. Rhizosphere bacterial communities exhibited a pattern of temporal succession that was consistent and repeatable over two growing seasons. There are few studies assessing the reproducibility over multiple seasons. Through the growing season, the rhizosphere community became progressively less diverse, likely reflecting root homogenization of soil microniches. Phylogenetic clustering of the rhizosphere dynamic taxa suggests evolutionary adaptation to Avena roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence.

scholarly journals Restoration of Degraded Alpine Meadows Improves Pollination Network Robustness and Function in the Tibetan Plateau

2021 ◽  
Vol 9 ◽  
Author(s):  
Erliang Gao ◽  
Yuxian Wang ◽  
Cheng Bi ◽  
Christopher N. Kaiser-Bunbury ◽  
Zhigang Zhao
Keyword(s):  
Tibetan Plateau ◽  
Seed Set ◽  
Anthropogenic Activities ◽  
Growing Season ◽  
The Tibetan Plateau ◽  
Alpine Meadows ◽  
Growing Seasons ◽  
Management Regime ◽  
Pollination Network ◽  
And Function

Ecological restoration is widely used to mitigate the negative impacts of anthropogenic activities. There is an increasing demand to identify suitable restoration management strategies for specific habitat and disturbance types to restore interactions between organisms of degraded habitats, such as pollination. In the Tibetan Plateau, alpine meadows have suffered severe degradation due to overgrazing and climate change. Protecting vegetation by fencing during the growing season is a widely applied management regime for restoration of degraded grasslands in this region. Here, we investigated the effect of this restoration strategy on plant–pollinator communities and plant reproduction in the eastern Tibetan Plateau. We collected interaction and seed set data monthly across three grazed (grazed all year) and three ungrazed (fenced during growing season) alpine meadows in growing seasons of two consecutive years. We found ungrazed meadows produced more flowers and attracted more pollinator visits. Many common network metrics, such as nestedness, connectance, network specialization, and modularity, did not differ between grazing treatments. However, plants in ungrazed meadows were more robust to secondary species extinction than those in grazed meadows. The observed changes in the networks corresponded with higher seed set of plants that rely on pollinators for reproduction. Our results indicate that protection from grazing in growing seasons improves pollination network stability and function and thus is a viable restoration approach for degraded meadows.

scholarly journals Habitats Are More Important Than Seasons in Shaping Soil Bacterial Communities on the Qinghai-Tibetan Plateau

2021 ◽  
Vol 9 (8) ◽  
pp. 1595
Author(s):  
Rui Wang ◽  
Miao Wang ◽  
Jing Wang ◽  
Yinghua Lin
Keyword(s):  
Tibetan Plateau ◽  
Bacterial Community ◽  
Bacterial Communities ◽  
Seasonal Changes ◽  
Relative Effect ◽  
Soil Bacterial Communities ◽  
Bacterial Dynamics ◽  
Composition And Structure ◽  
Microbial Biomarkers ◽  
Soil Bacterial

Both habitats and seasons can determine the dynamics of microbial communities, but the relative importance of different habitats and seasonal changes in shaping the soil bacterial community structures on a small spatial scale in permafrost areas remains controversial. In this study, we explored the relative effect of four typical alpine meadow habitats (swamp wetland, swamp meadow, meadow and mature meadow) versus seasons on soil bacterial communities based on samples from the Qinghai-Tibetan Plateau in four months (March, May, July and September). The results showed that habitats, rather than seasons explained more variation of soil bacterial composition and structure. Environmental cofactors explained the greatest proportion of bacterial variation observed and can help elucidate the driving force of seasonal changes and habitats on bacterial communities. Soil temperature played the most important role in shaping bacterial beta diversities, followed by soil total nitrogen and pH. A group of microbial biomarkers, used as indicators of different months, were identified using random forest modeling, and for which relative abundance was shaped by different environmental factors. Furthermore, seasonality in bacterial co-occurrence patterns was observed. The data showed that co-occurrence relationships changed over months. The inter-taxa connections in May and July were more pronounced than that in March and September. Bryobacter, a genus of subgroup_22 affiliated to Acidobacteria, and Pseudonocardia belonging to Actinobacteria were observed as the keystone taxa in different months in the network. These results demonstrate that the bacterial community was clustered according to the seasonal mechanism, whereas the co-occurrence relationships changed over months, which indicated complex bacterial dynamics in a permafrost grassland on the eastern edge of Qinghai-Tibetan.

Sign in / Sign up

Export Citation Format

Share Document