Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau

<div><p>The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m^-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m^-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m^-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland.</p></div

Relationship between ecosystem carbon density and environmental (climate and grazing) factors in alpine grassland.

<p>Variation of annual average temperature and annual average precipitation from 1971–2010 in alpine grassland.</p

Relationships between above-ground biomass (AGB) carbon density and environmental (climate and grazing) factors in alpine grassland.

<p>Variation of annual average temperature and annual average precipitation from 1971–2010 in alpine grassland.</p

Values of biomass and biomass carbon for alpine grassland on the Qinghai Plateau

<p>Values of biomass and biomass carbon for alpine grassland on the Qinghai Plateau</p

Data_Sheet_1_SbbR/SbbA, an Important ArpA/AfsA-Like System, Regulates Milbemycin Production in Streptomyces bingchenggensis.docx

<p>Milbemycins, a group of 16-membered macrolide antibiotics, are used widely as insecticides and anthelmintics. Previously, a limited understanding of the transcriptional regulation of milbemycin biosynthesis has hampered efforts to enhance antibiotic production by engineering of regulatory genes. Here, a novel ArpA/AfsA-type system, SbbR/SbbA (SBI_08928/SBI_08929), has been identified to be involved in regulating milbemycin biosynthesis in the industrial strain S. bingchenggensis BC04. Inactivation of sbbR in BC04 resulted in markedly decreased production of milbemycin, while deletion of sbbA enhanced milbemycin production. Electrophoresis mobility shift assays (EMSAs) and DNase I footprinting studies showed that SbbR has a specific DNA-binding activity for the promoters of milR (the cluster-situated activator gene for milbemycin production) and the bidirectionally organized genes sbbR and sbbA. Transcriptional analysis suggested that SbbR directly activates the transcription of milR, while represses its own transcription and that of sbbA. Moreover, 11 novel targets of SbbR were additionally found, including seven regulatory genes located in secondary metabolite biosynthetic gene clusters (e.g., sbi_08420, sbi_08432, sbi_09158, sbi_00827, sbi_01376, sbi_09325, and sig24_sbh) and four well-known global regulatory genes (e.g., glnR_sbh, wblA_sbh, atrA_sbh, and mtrA/B_sbh). These data suggest that SbbR is not only a direct activator of milbemycin production, but also a pleiotropic regulator that controls the expression of other cluster-situated regulatory genes and global regulatory genes. Overall, this study reveals the upper-layer regulatory system that controls milbemycin biosynthesis, which will not only expand our understanding of the complex regulation in milbemycin biosynthesis, but also provide a basis for an approach to improve milbemycin production via genetic manipulation of SbbR/SbbA system.</p

Ecosystem (biomass and soil) carbon density in alpine grassland on the Qinghai Plateau.

<p>Ecosystem (biomass and soil) carbon density in alpine grassland on the Qinghai Plateau.</p

Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau - Fig 2

<p><b>Frequency distributions of above-ground biomass (AGB) carbon concentration and below-ground biomass (BGB) carbon concentration of alpine steppe (a and b) and alpine meadow (c and d).</b> The unit of the biomass carbon concentration is g kg^-2.</p

Relationship between belowground biomass (BGB) carbon density and environmental (climate and grazing) factors in alpine grassland.

<p>Variation of annual average temperature and annual average precipitation from 1971–2010 in alpine grassland.</p

Effects of environmental factors on biomass carbon and SOC density in a linear mixed-effects model (LME).

<p>Effects of environmental factors on biomass carbon and SOC density in a linear mixed-effects model (LME).</p

Spatial distribution of sampling sites in alpine grasslands on the Qinghai Plateau.

<p>The vegetation map of the plateau was obtained from China’s vegetation atlas at a scale of 1: 1,000,000 (Chinese Academy of Sciences, 2001). Also shown are locations of the 115 sites surveyed during 2011–2012.</p