Unique ecosystems distributed in alpine areas of the Qinghai–Tibetan Plateau play important roles in climate change mitigation, local food supply, and conservation of species diversity. To understand the water use efficiency (WUE) of this fragile and sensitive region, this study combined observed data from the eddy covariance system and the Shuttleworth–Wallace (S-W) model to measure the continuous mass exchange, including gross primary productivity (GPP), evapotranspiration (ET), and canopy transpiration (T) throughout 2 or 3 years (2016–2018) in three common alpine ecosystems (i.e., alpine steppe, alpine meadow, and alpine swamp). These ecosystems represent a water availability gradient and thus provide the opportunity to quantify environmental and biological controls on WUE at various spatiotemporal scales. We analyzed the ecosystem WUE (WUEe; defined as the ratio of GPP to ET) and canopy WUE (WUEc; defined as the ratio of GPP and canopy T). It was found that the yearly WUEe was 1.40, 1.63, and 2.16 g C kg–1 H2O, and the yearly WUEc was 8.93, 2.46, and 5.19 g C kg–1 H2O in the three typical ecosystems, respectively. The controlling factors of yearly WUE diverged between WUEe and WUEc. We found that plant functional group proportion (e.g., gramineous and Cyperaceae) highly explained the yearly WUEe variation across sites, and a good correlation was observed between community species diversity and WUEc. These findings suggest that community composition and trait change are critical in regulating WUEe and WUEc across different alpine ecosystems and that the regulation mechanisms may differ fundamentally between WUEe and WUEc.

No abstract

Aim This study aimed to analyse bacterial community and biomineralization products from Wudalianchi non‐active volcanic field and the relationship between magnetization and bacterial community. Methods and Results Eighteen sediment samples obtained from Wenbo Lake, high‐throughput sequencing and quantitative PCR (qPCR) were separately employed to investigate the bacterial community composition dynamics and abundance variation of the sediment sample with the highest iron‐reducing capacity during incubation. The mineralization products were characterized by transmission electron microscopy, scanning electron microscopy, X‐ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometer (VSM) and variable‐temperature magnetism analyses. The results showed that the highest iron reduction rate was 98·06%. Seven phyla were identified as dominant bacterial phyla during the incubation process. Iron‐reducing bacteria (FeRB) including Geobacter, Desulfosporosinus and Clostridium were involved in the iron mineralization process. The 16S rDNA copy numbers of sediment decreased quickly and then stayed steady during the incubation. Bacteria with rod‐shaped and spheroid species were involved in extracellular iron reduction to produce magnetic particles with massive aggregation and columnar structures on the mineral surface morphologies. The materials produced by the microbial community over the incubation period were sequentially identified as siderite, magnetite and maghemite. The magnetism of the mineral samples gradually increased from 0·31748 to 33·58423 emu g−1 with increased incubation time. The final products showed relatively stable magnetism under 0–400 K. Meanwhile, the saturation magnetization (MS) of the mineralized substance was tightly associated with bacterial diversity (P < 0·05). Conclusions Bacterial community varied during incubation of iron‐reducing sediment of volcanic lake. Various iron mineral crystals were in turn formed extracellularly by FeRB. The magnetism of mineralized products was tightly associated with bacterial community. Significance and Impact of the Study These results not only help us to better understand the iron mineralization of FeRB in the volcanic lake sediments but also provide basic information for the future application of FeRB in environmental bioremediation.

No abstract

Iron is the fourth most abundant chemical element by weight in the earth's crust and exists in the forms of ferrous Fe(II) and ferric Fe(III) [1]. Its cycling on our planet is an extremely complex process involving both abiotic and biotic components [2]. As important members in biotic cycling of iron, iron-cycling bacteria (ICB) including iron-oxidizing bacteria (IOB) and iron-reducing bacteria (IRB), and magnetotactic bacteria (MTB) can convert iron to biocomposites such as oxides, hydroxides [4][5][6].