Research Status, Problems and Direction of Soil Organic Carbon in Zoige Peat Wetland

Peatlands,as a special type of wetland,occupy only 3%of the Earth’s surface,but bear about one-third of the world’s soil carbon storage and play an important role in the global carbon cycle.The Zoige Wetland is located on the eastern edge of the Qinghai-Tibet Plateau,and its peat reserves are up to 1.9 billion tons,accounting for more than 40%of the country’s peat resources,which is an important support for China to achieve the“double carbon”goal.This paper reviews the research status and storage estimation of soil organic carbon in Zoige Wetland.The statistical results show that there is a large difference in the estimation of carbon storage in the peatland of Zoige(0.43-1.42 Pg).The reasons are mainly related to marked differences in values reported for soil densities,organic carbon levels,and accu­mulation rates.There are still great uncertainties in the estimation of wetland carbon stocks,and future studies should focus on reducing soil carbon sink uncertainties,climate change,the impact of permafrost melting on carbon sink functions,the impact of degraded ecosystem restoration and sink enhancement pathways,and other greenhouse gas functions.In order to accurately reveal the current situation and future trend of carbon sink in peat wetlands,a model-multi-source observation data fusion system was constructed to complement the observation shortcomings in key ar­eas,and provide reference and support for the construction of carbon neutral ecological civilization.

Driving forces of land use and land cover change (LUCC) in the Zoige Wetland, Qinghai-Tibetan Plateau

The Zoige Wetland is located in the northeastern Qinghai-Tibetan Plateau, which is highly sensitive to global environment change and human disturbance because of its high elevation and cold environment, thus, it＇s a hotspot for land use and land cover change （LUCC） research. We used Landsat MSS images from 1975, Landsat ETM images from 2000, and Landsat TM images fi：om 1990 and 2005 to assess the LUCC in the study area, using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. The monitoring result shows that the study area＇s environment degraded rapidly between 1975 and 2005, including wetland shrinkage from 5,308 km2 to 4,980 lan2, sandy land expansion from 112 krn2 to 137 krn2, forest land decreasing from 5,686 km2 to 5,443 km2, and grassland degradation from 12,309 km2 to 10,672 km2. According to the analysis of meteorological data and social-economic statistical data, we concluded that the LUCC in the Zoige Wetland was caused by both natural and anthropogenic factors, but human activities were primarily responsible for the observed LUCC, thereby, we suggest human behaviors must be adjusted to control environmental degradation.

The Response of Vegetation Biomass to Soil Properties along Degradation Gradients of Alpine Meadow at Zoige Plateau

Alpine grassland of the Tibetan Plateau has undergone severe degradation, even desertification. However, several questions remain to be answered, especially the response mechanisms of vegetation biomass to soil properties. In this study, an experiment on degradation gradients was conducted in an alpine meadow at the Zoige Plateau in 2017. Both vegetation characteristics and soil properties were observed during the peak season of plant growth. The classification and regression tree model(CART) and structural equation modelling(SEM) were applied to screen the main factors that govern the vegetation dynamics and explore the interaction of these screened factors. Both aboveground biomass(AGB) and belowground biomass(BGB) experienced a remarkable decrease along the degradation gradients. All soil properties experienced significant variations along the degradation gradients at the 0.05 significance level. Soil physical and chemical properties explained 54.78% of the variation in vegetation biomass along the degradation gradients. AGB was mainly influenced by soil water content(SWC), soil bulk density(SBD), soil organic carbon(SOC), soil total nitrogen(STN), and pH. Soil available nitrogen(SAN), SOC and p H, had significant influence on BGB. Most soil properties had positive effects on AGB and BGB, while SBD and p H had a slightly negative effect on AGB and BGB. The correlations of SWC with AGB and BGB were relatively less significant than those of other soil properties. Our results highlighted that the soil properties played important roles in regulating vegetation dynamics along the degradation gradients and that SWC is not the main factor limiting plant growth in the humid Zoige region. Our results can provide guidance for the restoration and improvement of degraded alpine grasslands on the Tibetan Plateau.

New Evidence for Genesis of the Zoige Carbonate-Siliceous-Pelitic Rock Type Uranium Deposit in Southern Qinling:Discovery and Significance of the 64 Ma Intrusions

The carbonaceous-siliceous-argillitic rock type uranium deposit in the Zoige area is located in the northeastern margin of the Tibetan Plateau, and has gained much attention of many geologists and ore deposit experts due to its scale, high grade and abundant associated ores. Because of the insufficient reliable dating of intrusive rocks, the relationship between mineralization and the magmatic activities is still unknown. In order to study this key scientific issue and the ore-forming processes of the Zoige uranium ore field, the LA-ICP-MS zircon U-Pb dating of magmatic rocks was obtained：64.08±0.59 Ma for the granite-prophyry and ~200 Ma for the dolerite. U-Pb dating results of uraninite from the Zoige uranium ore field are mainly concentrated on ~90 Ma and ~60 Ma. According to LA-ICP-MS U-Pb zircon dating, the ages for the dolerite, porphyry granite and granodiorite are 200 Ma, 64.08 Ma approximately and 226.5-200.88 Ma, respectively. This indicates that the mineralization has close relationship with activities of the intermediate-acidic magma. The ages of the granite porphyry are consistent with those uraninite U-Pb dating results achieved by previous studies, which reflects the magmatic and ore-forming event during the later Yanshanian. Based on the data from previous researches, the ore bodies in the Zoige uranium ore field can be divided into two categories：the single uranium type and the uranium with polymetal mineralization type. The former formed at late Cretaceous（about 90 Ma）, while the latter, closely related to the granite porphyry, formed at early Paleogene（about 60 Ma）. And apart from ore forming elemental uranium, the latter is often associated with polymetallic elements, such as molybdenum, nickel, zinc, etc.

A New Species of the Genus Elaphe(Squamata: Colubridae) from Zoige County,Sichuan,China

Previous phylogenetic analyses of DNA sequence data reveal a likely new species of Elaphe Fitzinger from China,which forms the sister group of all extant Elaphe. One of the three original specimens is crushed and the other two are neonates,which precludes a morphological analysis. Three adult snakes(2 females,1 male) collected from Jiangzha Hot Spring in Zoige County,Sichuan,China on 26 July 2010 now facilitate the species’ description. Mitochondrial DNA nucleotide sequences of cytochrome b(cyt b),NADH dehydrogenase subunit 4(ND4),12S ribosomal RNA(12S rRNA),and cytochrome oxidase subunit 1(CO1) from the adults are identical to sequences from the crashed specimen. Interspecific uncorrected p-distances of partial CO1 gene of 26 sequences from all 11 species of Elaphe,including this new species,are large(8.5–15.2%). This new species is morphologically distinguished from all other species of Elaphe by several characters: 'M'-shaped marking on the supraoculars and adjacent frontal; four parallel series of red-brown spots on the dorsum extending from the neck to the vent; four longitudinal stripes associated with the spots; each spot is usually composed of a whole(or incomplete) red-brown scale with puce borders; spots of each stripe are similar in shape,they occur at relatively regular intervals of one or two scales,and they are slightly red-brown in color; and it has three preoculars,whereas all other species have one or two. Now Elaphe contains 11 species and this discovery highlights the need for continued exploration of temperate regions.

Oviposition Site Selection of the Plateau Frog (Nanorana pleskei) in the Zoige Wetland, China

For oviparous species, oviposition site selection influences adult reproductive success as well as the fitness of the resulting offspring. Females usually choose potential egg-laying sites depending on abundance and quality to maximize their reproductive success. We focused on the oviposition site selection of this plateau frog in Zoige wetland and investigated how the egg-laying pattern of the females influences their offspring＇s survival. We found that shallow waters, decentralized spawning patterns, and egg attachment to appropriate distance to the water surface were the main spawning strategies of Nanorana pleskei endemic to Qinghai-Tibet Plateau. We argued that drought caused by increasing temperature and variable precipitation has probably influenced N. pleskei reproductive success, which may be a crucial reason for its population decline. Our findings have important significance for habitat preservation, increasing embryo survival and establishing practical conservation policies.

Peat record reflecting Holo-cene climatic change in the Zoige Plateau and AMS radiocarbon dating

Through the use of reliable AMS dating of high resolution (15-30 years) peat and the establishment of monsoon climate proxies sequence, we have been able to recognize several cold, dry events in the Tibetan Plateau during the Holocene. The more obvious ones occurred around 12800, 11300, 10200, 9580, 8900, 6400, 4400, 3700, 2800 and 1500 cal. aBP. These events correlate well with both ice rafting events recorded in high latitude North Atlantic Ocean sediment cores and cooling events in the low latitude SST. Spectral analysis indicates high frequency climate variation on centennial-millennial time scale during the Holocene. This further reflects Holocene climate instability and the existence of centennial-millenium scale rhythm in mid latitude areas as well.

The uplifting and environmental change of Qinghai-Xizang (Tibetan) Plateau in the past 0.9 Ma inferred from core RM of Zoige Basin

According to the synthetic multi-disciplinary study on the lake sediments from core RM of Zoige Basin, i.e. the deepest wholly-collected core in Tibetan Plateau, the palaeoclimate and palaeoenvironment for the basin in the past 0.9 Ma have been reconstructed. The analytical results suggest that there distinctively exist 3 accelerated uplifting periods for the east Plateau in the past 0.9 Ma, i.e. 800, 360 and 160 kaB.P., with the study on the sedimentary characteristics, the texture of sedimentary cycles and variations of depositional rates, in conjunction with the environment features of cold/warm to dry/wet combination. The paper also probes into the environmental effect under the 3 accelerated tectonic-upliftings on the background of global change.

Sedimentological evidence of the piracy of fossil Zoige Lake by the Yellow River

The Yellow River, the birthplace of China’s culture, is well known over the world forits huge sediment yield and unruly temper. The origin of the river was considered bymany foreign and domestic scholars through long-term studies as: the Yellow River turnedgradually to the present features through the way that the river was eroded headwards

Environmental evolution of Zoige Basin since 900 kaB.P. and comparison study with Loess Plateau

The Zoige Basin is located in the eastern margin of the Qinghai-Xizang Plateau, in which two cores, RH and RM, have been drilled, with the depths of 120 m and 310 m respectively. The former with the bottom age of 826 kaB. P. has been divided into 21 stages according to the multi-proxy analysis , which could be basically compared with the oxygen isotope record of deep-sea core. The palaeoclimatic and palaeoenvironmemal process of the Zoige Basin over the past 900 kaB. P. is reconstructed, and the comparison of core RH with the Luochuan Loess record is made.

Temperature estimation by oxygen-stable record over the past 200 ka in Zoige basin

According to the evolutionary processes of stable oxygen isotope in lake water, a physical model has been established to calculate paleotemperature and used to quantitatively rebuild the temperature sequences in the past 200 ka in Zoige basin, eastern Tibet. The results show that in the Zoige region the maximum temperature of the period equivalent to stage 7 in deep-sea stable oxygen record was 2.7℃ higher than that of the present; in stage 6, it was 4.3℃ lower and the value of the peak temperature of stage 5 was 5.2℃ higher than the present air temperature; in stage 4, the average temperature was 2-3℃ lower; in stage 3, the curve of the temperature estimated displayed the character of two peaks and one valley, and the value of the temperature difference in the period was above 4℃. Moreover, by comparing the tendency of the curves of paleotemperature calculated and responsive stable oxygen isotope of authicarbonate, we also found that during stage 6 the environment in the Zoige basin was

Diversity of methanotrophs in Zoige wetland soils under both anaerobic and aerobic conditions

Zoige wetland is one of the most important methane emission centers in China. The oxidation of methane in the wetland affects global warming, soil ecology and atmospheric chemistry. Despite their global significance, microorganisms that consume methane in Zoige wetland remain poorly characterized. In this study, we investigated methanotrophs diversity in soil samples from both anaerobic site and aerobic site in Zoige wetland using pmoA gene as a molecular marker. The cloning library was constructed according to the pmoA sequences detected. Four clusters of methanotrophs were detected. The phylogenetic tree showed that all four clusters detected were affiliated to type I methanotrophs. Two novel clusters （cluster 1, cluster 2） were found to relate to none of the recognized genera of methanotrophs. These clusters have no cultured representatives and reveal an ecological adaptation of particular uncultured methanotrophs in Zoige wetland. Two clusters were belonging to Methylobacter and Methylococcus separately. Denaturing gradient gel electrophoresis gel bands pattern retrieved from these two samples revealed that the community compositions of anaerobic soil and aerobic soil were different from each other while anaerobic soil showed a higher metanotrophs diversity. Real-time PCR assays of the two samples demonstrated that aerobic soil sample in Zoige wetland was 1.5 times as much copy numbers as anaerobic soil. These data illustrated that methanotrophs are a group of microorganisms influence the methane consumption in Zoige wetland.

δ^(13)C values and hydrogen index records in sediment organic matter of RH core of Zoige Basin,eastern Qing-Zang(Tibet)Plateau and their environmental significance

Total organic carbon （TOC） content correlates very well with hydrogen index （HI） in the sedi-ments of RH core in the Zoig Basin.And the δ13C values of TOC become more positive while both TOCcontent and HI decline,indicating the subaerial exposure or the lake sedimonts approaching to the water lev-el.On the basis of the above,RH core sediments are divided into 23 climatic fluctuation stages,including 12 warm-humid stages and 11 dry-cold stages,which can he compared with oceanic oxygen isotopestages,loess profile and polar ice-core records.

Methane emissions from natural and drained peatlands in the Zoigê, eastern Qinghai-Tibet Plateau

Peatlands are one of the major natural sources of methane （CH4）, but the level of CH4 efflux is uncertain, especially in alpine peatlands. In this study, CH4 emission fluxes from natural and drained peatlands on the Qinghai- Tibet Plateau, southwest China, were measured from June to October in 2013 using the opaque static chamber technique and the Fast Greenhouse Gas Analyzer （DLT-100, Los Gatos Research Corp.）. CH4 emission fluxes ranged from 2.07 to 56.33 mg m^-2 h^-1 in natural peatlands and from 0.02 to 0.42 mg m^-2 h^-1 in drained peatlands. Mean CH4 emission flux was 19.13 mg m^-2 h^-1 in natural peatlands and 0.14 mg m^-2 h^-1 in drained peatlands. These results showed that drainage led to a significant decrease in CH4 emissions. CH4 emission fluxes for all sampling plots were significantly correlated with variation in water table depth for linear （R^2 = 0.453, P 〈 0.01） and exponential functions （R^2 = 0.429, P 〈 0.01）.

A remote sensing monitoring method for alpine grasslands desertification in the eastern Qinghai–Tibetan Plateau

Alpine grassland is the typical vegetation in the eastern Qinghai–Tibetan Plateau,which has important ecological service functions,and also supports the development of alpine stock farming.In recent years,under both the natural and human disturbance,alpine grasslands in this area have appeared to different degrees of desertification.A diagnosis of the desertification degree serves as the basis for grassland ecological restoration.This study constructs a comprehensive index based on remote sensing called alpine grassland desertification index(AGDI)to monitor the areas and degree of desertification.The most relevant indicators of desertification,namely,vegetation fraction,aboveground biomass,soil moisture,and land surface temperature,were selected to establish AGDI.The geographical detector is used to reselect and assess these indicators.The results show that the overall verification accuracy of AGDI is 82.05%.In particular,the accuracy of identifying severe desertification is the highest.Our study confirms that the desertification of alpine grasslands in the eastern Qinghai–Tibetan Plateau is characterized by fragmentation.Thus,Landsat-8 OLI data with a spatial resolution of 30 m is more suitable than MODIS data for alpine grasslands desertification monitoring.The research results can provide a methodological reference for monitoring desertification of alpine grasslands and other grassland regions in the world.

Structural Deformation of Zoigê Basin Along the Deep Seismic Reflection Profile

Being the core of the Songpan-Ganze block,Zoig(?) Basin is a favorable zone of oil and gas exploration. And it not only is the important deposition area of the northern Songpan-Garze in the Middle-Late Triassic, but also impacts on the formation and evolution of the structural belt.To further understand the Zoig(?) Basin, we reprocessed the 0-20.0 s data of the Tangke-Hezuo deep seismic reflection profiles across the majority

COMPOSITIONS OF δ^(18)O AND δ^(13)C IN VARIOUS CARBONATES OF CORE RM IN THE ZOIGê BASIN AND CLIMATIC SIGNIFICANCE

The hole RM, the deepest one fully obtained core in the Qinghai-Xizang Plateau, situated in the depositional center of the Zoire Basin (33°57′N; 102°21′E) in the northeastern QinghaiXizang Plateau with a depth of 310.46 m. From 14C dating and Paleomagnetic stratigraphic study,the core RM can date back to 900 ha B.P.. In this paper we analyzed the compositions of δ18O and δ13C in various carbonates can date (snail, obstrode, chemical Cabonate) in core RM and discussed preferably the paleoclimatic record by the proxies of δ18O and δ13C Of chemical carbonate (authicalbonate) from core RM in the past 140 ka. The results showed that the values of δ18O in various carbonates are generally identical, and the values of δ13C in it are inconsistent, while there exist better relativity. The studies also demonstrated that there was a negative correlation between δ18O and δ13C of authicabonate in core RM in the past 140 ka, showing that the changes of δ18O values were mainly relative to the water temperature. According to above, the climatic evolutionary sequence were rebuilt in the past 140 ka in the region.

Construction of Zoigê Animal Corridor Based on the Idea of Low Impact

With the rapid urbanization and construction of new roads in Zoigê County, the migration routes of many animals have been cut off, leaving a buffer zone between wetlands and mountains which suffered from industrial water pollution in the northwest of the city. Based on the analysis of site status and the concept of low impact, a Zoigê ecological corridor crossing National Highway 213 was constructed by means of four core strategies to restore and protect animal migration routes, restore original wetlands, and create new habitats, thus achieving the unity of human, animal and nature.

Climatic variations in the past 140 ka recorded in core RM, east Qinghai-Xizang Plateau

The sequences of climatic evolution are reconstructed by the analyses of δ13C and δ18O of carbonate from core RM in the Zoige Basin since 140 kaB. P. During the Last Glaciation there existed at least seven warm climatic fluctuations and five cold events correlated with the records of ice core and deep sea, and during the preceding last in-terglacial period there were two cold climatic variations coinciding with the record of ice core GRIP. These results depict climatic instability in east Qinghai-Xizang Plateau over the last interglacial period. In addition, the environmental proxies of the carbonate content and pigments indicate the similar results to the stable isotope record from core RM.

Paleovegetational and paleoclimatic evolution series on northeastern Qinghai-Xizang Plateau in the last 30 ka

Palynological study of 2 lacustrine suites by limnological and 14C dating reveals the local evolutionary history of the paleovegetation and the paleoclimate of Zoige Plateau, northeastern Qinghai-Xizang Plateau, since the last 30ka. The territorial paleovegetation evolution experienced 7 stages: alpine desert vegetation, grassland, marsh and sub-alpine meadow, islet forest, marsh and meadow, Picea and Abies forest, marsh and sub-alpine meadow, islet dark conifer, marsh and sub-alpine meadow, and the inferred paleoclimate evolution shared similar variations correspondingly. The major climatic events during the periods of post-glacial and the Holocene left their distinct marks in sediment record.