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.

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.

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.

Rangeland Privatization and Its Impacts on the Zoige Wetlands on the Eastern Tibetan Plateau

The high Zoige Basin (Ruoergai Plateau) on the eastern Tibetan Plateau is a fault depression formed during intensive uplifting of the Tibetan Plateau. The wetland is globally important in biodiversity and is composed of marshes,bogs,fens,wet meadows and shallow water interspersed with low hills and sub-alpine meadows. Most of the Zoige wetlands have long been one of the most important grazing lands in China. Recent rangeland policy has allowed grazing,and usable wetland areas have been being legally allocated to individuals or groups of households on a long-term lease basis. Privatization of the wetland has impacted the Zoige wetlands in aspects of hydrologic condition,landscape and biodiversity. The uneven spatial distribution of water resources on private lands has led to the practice of extracting ground water,which has decreased the perched water table in Zoige. Fencing off the rangelands and grazing on expanding sand dunes have affected landscapes. Variation in the water table has led to the changes in vegetation diversity,resulting in the changes in wildlife and aquatic diversities and ecosystem processes. Making use all year round of the pasture that was previously grazed only in summer has shrunk the daily activity space of wildlife,and the newly erected fences blocked the movement of wild animals looking for food in the snow to lower and open areas. To maintain the favorable conditions of the Zoige wetland ecosystem,the author suggests that,in addition to biophysical research and implementation of conservation practices,there is an immediate need to initiate an integrated management program,increase public awareness of wetland functions and provide better training for the local conservation staff.

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.

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.

Landscape Pattern Evolution Processes of Alpine Wetlands and Their Driving Factors in the Zoige Plateau of China

Zoige Plateau wetlands are located in the northeastern corner of the Qinghai-Tibet Plateau.The landscape pattern evolution processes in the Zoige Plateau and their driving factors were identified by analyzing the dynamic changes in landscape modification and conversion and their dynamic rates of alpine wetlands over the past four decades.The results showed that the landscape conversion between wetlands and non-wetlands mainly occurred during the period from 1966 to 1986.The marsh wetland area converted from lake and river wetlands was larger because of swamping compared to other wetland landscapes.Meanwhile,the larger area of marsh wetlands was also converted to lake wetlands more than other types of wetlands.The modification processes mainly occurred among natural wetland landscapes in the first three periods.Obvious conversions were observed between wetland and nonwetland landscapes(i.e.,forestland,grassland,and other landscapes) in the Zoige Plateau.These natural wetland landscapes such as river,lake and marsh wetlands showed a net loss over the past four decades,whereas artificial wetland landscapes(i.e.,paddy field and reservoir and pond wetlands) showed a net decrease.The annual dynamic rate of the whole wetland landscape was 0.72%,in which the annual dynamic rate of river wetlands was the highest,followed by lake wetlands,while marsh wetlands had the lowest dynamic rate.The integrated landscape dynamic rate showed a decreasing trend in the first three periods.The changes in wetland landscape patterns were comprehensively controlled by natural factors and human activities,especially human activities play an important role in changing wetland landscape patterns.

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.

Quantifying land degradation in the Zoige Basin,NE Tibetan Plateau using satellite remote sensing data

Considerable efforts have been dedicated to desertification research in the arid and semi-arid drylands of central Asia. However,there are few quantitative studies in conjunction with proper qualitative evaluation concerning land degradation and aeolian activity in the alpine realm. In this study,spectral information from two Landsat-5 TM scenes(04.08.1994 and 28.07.2009,respectively) was combined with reference information obtained in the field to run supervised classifications of eight landscape types for both time steps. Subsequently,the temporal and spatial patterns of the alpine wetlands/grasslands evolutions in the Zoige Basin were quantified and assessed based on these two classification maps. The most conspicuous change is the sharp increase of ~627 km^2 degraded meadow. Concerning other land-covers,shallow wetland increases ~107 km^2 and aeolian sediments(mobile dunes and sand sheets) have an increase of ~30 km^2. Considering the deterioration,an obvious decrease of ~440 km^2 degraded wetland can be observed. Likewise,decrease of deep wetland(~78 km^2),humid meadow(~80 km^2) and undisturbed meadow(~88 km^2) were determined. These entire evolution matrixes undoubtedly hint a deteriorating tendency of the Zoige Basin ecosystem,which is characterized by significantly declined proportion of intact wetlands,meadow,rangeland and a considerable increase ofdegraded meadow and larger areas of mobile dunes. In particular,not only temporal alteration of the landcover categories,the spatial and topographical characteristics of the land degradation also deserves more attention. In the alpine rangelands,the higher terraces of the river channels along with their slopes are more liable to the degradation and desertification. This tendency has significantly impeded the nomadic and agriculture activities. The set of anthropozoogenic factors encompassing enclosures,overgrazing and trampling,rodent damaging and exceedingly ditching in the wetlands are assumed to be the main controlling mechanisms for the landscape degradation. A suite of strict protection policies is urgent and indispensable for self-regulation and restoration of the alpine meadow ecosystem. Controlling the size of livestock,less ditching in the rangeland,and the launching of a more strict nature reserve management by adjacent Ruoergai,Maqu and Hongyuan Counties would be practical and efficacious in achieving these objectives.

A Study on the Effects of the Surrounding Faults on Water Loss in the Zoige Wetland,China

The Zoige wetland is the biggest alpine wetland in the world,and an important water resource of the Yellow River.Due to natural and human factors,the Zoige wetland has been seriously degraded.Existing studies on the Zoige wetland mainly focus on the macro features of the wetland,while the influence of the surrounding faults on the Zoige wetland degradation is rarely studied.This study uses terrain data to analyze the cover change and the water loss caused by the Wqie-Seji fault based on the distributed hydrological model.The simulated water loss demonstrates that the Normalized Difference Vegetation Index(NDVI) is the most important factor for inducing water loss.The fault is also a factor that cannot be neglected,which has caused 33% of the wetland water loss.Therefore,it is of importance to study the influence of the fault on the wetland degradation.

Analysis of Dynamics and Driving Factors of Wetland Landscape in Zoige,Eastern Qinghai-Tibetan Plateau

Zoige Wetland is one of the largest plateau wetlands in the world.This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8.7 and ArcGIS9.0.It is the first comparative analysis of a system of rapidly changing wetland with landscape patterns in Zoige, using 3 classified landsat Thematic Mapper images of 1977, 1994 and 2001.The classified images were used to generate wetland distributing maps, and shape index(S), diversity index(H), dominance index(D), evenness index(E), fragmentation index(F) and fractal dimension(Fd) were calculated and analyzed spatiotemporally across pure grazing area in Zoige for each landscape type and in different periods(before 1977, during 1977～1994 and 1994～2001), as well as the driving forces of natural and anthropogenic.The study shows that for a comprehensive understanding of the shapes and trajectories of the shrinking and desertificated land expansion of the wetland, a spatiotemporal landscape metrics analysis in different periods is an improvement than only with landscape changing rates.This type of analysis can also be used to infer underlying social, economic, and political processes that drive the observed wetland forms.The results indicate that wetland patterns can be changed over relatively short periods of time.Thetotal area of lake reduced by 164.86 km2,grassland extended by 141.74 km2,semi-marsh extended by 105.94 km2 , marsh reduced by 86.00 km2;the number of landscape patches reduced by 56, and their average area decreased by 2.68 km2;the successions within lake, marsh, semi-marsh and grassland were found obviously;S decreased stepwise;D and F increased but H decreased;The changing rate after 1994 was 2.3 to 2.9 times greater than that before.The change of the wetland landscape patterns resulted in the interaction between socio-economic and natural forces of positive and negative aspects;and natural factors affected as assistant aspect.Some important human activities in this period led to the change of the landscape patterns in this region directly.Some measurements made by government and NGO delayed the converting process partly.

Sensitivity analysis of the De Nitrification and De Composition model for simulating regional carbon budget at the wetlandgrassland area on the Zoige Plateau,China

Although mathematical models(e.g., De Nitrification and De Composition(DNDC) provide a powerful tool to study regional carbon budget, it is still difficult to obtain accurate simulation results because there exists large uncertainties in modeling regional carbon budget. Through the investigation on the sensitivity of model output parameters to the input parameters, sensitivity analysis(SA) has been proved to be able to identify the key sources of uncertainties and be helpful to reduce the model uncertainties. However, some input parameters with discrete values(e.g., land use type and soil type) and the regional effect of the sensitive parameters were rarely examined in SA. In this paper, taking the Zoige Plateau as a case area, we combined the one-factor-ata-time(OAT) with Extended Fourier Amplitude Sensitivity Test(EFAST) to conduct a SA of DNDC for simulating the regional carbon budget, including Gross Primary Productivity(GPP), Net Primary Productivity(NPP), Net Ecosystem Productivity(NEP), autotrophic respiration(Ra), soil microbial heterotrophic respiration(Rh) and ecosystem respiration(Re). The result showed that the combination of OAT and EFAST could test the contribution of the input parameters with discrete values to the output parameters. In DNDC model, land use type and soil type had a significant impact on the regional carbon budget of the Zoige Plateau, and daily temperature was also confirmed to be one of the most important parameters for carbon budget. For the other input parameters, with the change of land use type or soil type at regional scale, the sensitive parameters of carbon budget would vary accordingly. The SA results would provide scientific evidence to optimize DNDC model and they suggested that we should pay attention to the spatial/temporal effect of SA and try to use the appropriate data in simulation of the regional carbon budget.

Responses of soil inhabiting nitrogen-cycling microbial communities to wetland degradation on the Zoige Plateau,China

The wetlands on the Zoige Plateau have experienced serious degradation,with most of the original marsh being converted to marsh meadow or meadow.Based on the 3 wetland degradation stages,we determined the effects of wetland degradation on the structure and relative abundance of nitrogencycling(nitrogen-fixing,ammonia-oxidizing,and denitrifying) microbial communities in 3 soil types(intact wetland:marsh soil;early degrading wetland:marsh meadow soil;and degraded wetland:meadow soil) using 454-pyrosequencing.The structure and relative abundance of nitrogen-cycling microbial communities differed in the 3 soil types.Proteobacteria was the predominant phylum in most soil samples but the most abundant soil nitrogenfixing and denitrifying microbial bacteria differed at the class,order,family,and genus levels among the 3soil types.At the genus level,the majority of nitrogenfixing bacterium sequences related to Bradyrhizobium were from marsh and marsh meadow soils;whereas those related to Geobacter originated from meadow soil.The majority of ammonia-oxidizing bacterium sequences related to Nitrosospira were from marsh(except for the 40-60 cm layer),marsh meadow and meadow soils;whereas those related to Candidatus Solibacter originated from 40-60 cm layer of marsh soil.The majority of denitrifying bacterium sequences related to Candidatus Solibacter and Anaeromyxobacter were from marsh and meadow soils;whereas those related to Herbaspirillum originated from meadow soil.The distribution of operational taxonomic units(OTUs)and species were correlated with soil type based upon Venn and Principal Coordinates Analysis(PCoA).Changes in soil type,caused by different water regimes were the most important factors influencing compositional changes in the nitrogen-fixing,ammonia-oxidizing,and denitrifying microbial communities.

A METHOD TO ESTIMATE PALEOTEMPERATURE FROM ENVIRONMENTAL PROXIES IN LAKE SEDIMENTSDISSOLVED AND PARTICULATE ORGANIC CARBON IN YANTAI SISHILI BAY AQUICULTURE WATERS——A STUDY ON ZOIGE BASIN IN EASTERN TIBETAN PLATEAU,CHINA

Seeking for an effective method to probe further the relation among Tibetan Plateau, climatic events, and natural environmental changes in the Zoige Basin, we proposed a physical model for the reconstruction of climate and environment and a preliminary application was conducted on the 45 m (about 200 ka BP ), upper part of Core RM (310 m long) drilled in the Zoige Basin (33°57’N, 102°21’E), on the eastern Tibetan Plateau. The results showed that: a) in the Zoige region, the maximum temperature in the period equivalent to Stage 7 in the deep sea stable oxygen record was 2.7℃ higher than that at present; b) Stage 6 temperature was 4.3℃ lower than that at present; c) Stage 5 peak temperature was 5.2℃ higher than that at present; d) Stage 4 average temperature should have been 2-3℃ lower than that at present; and e) Stage 3 temperature differences within the period were more than 4℃. It was found that during Stage 6 (140-160 ka BP) the environment in the Zoige Basin was extraordinary, representing a transition period from warm dry and cold wet to warm wet and cold dry environmental conditions due to the uplift that occurred on the Tibetan Plateau at this period.

若尔盖国家公园评估区种子植物区系特征

为探讨若尔盖国家公园种子植物区系性质和特征,以川、甘两省拟建国家公园评估区(面积23338.49 km2)为研究对象,地理坐标位于101°1′49″—103°24′52″E,32°9′34″—34°32′25″N之间,通过实地调查,了解若尔盖国家公园评估区种子植物组成,并进行区系特征分析。结果表明:(1)评估区有种子植物96科454属1757种,其中大科(50种以上)有9个,共计908个种,占种子植物总种数的51.68%;菊科、禾本科、蔷薇科属于广布的世界科,在本区系中占优势地位;单种属(仅1种)有220个,占种子植物总属数的48.46%,表明本区系年轻和衍生的进化性质。(2)科的分布区可划分为8个类型和7个变型,除世界广布类型外,温带性质有32个科,占比为64.00%,温带性质明显;东亚特有科有1个,即星叶草科Circaeasteraceae,表明与东亚古老植物区系有关。(3)属的分布区可划分为14个类型和15个变型,除世界分布和外来属以外,温带性质的属占比为90.38%,其中北温带占比为44.81%,具有从北温带向中温带过渡的性质。(4)评估区内有中国特有种763种,高原特化现象明显,其中甘肃和四川省分布的狭域特有植物有24种。

若尔盖高寒湿地空间分布及景观格局动态研究

若尔盖地区拥有全球面积最大的高寒泥炭沼泽湿地。基于30 m全球地表覆盖数据集,利用Arcgis和Fragstats软件对2000年、2010年和2020年若尔盖地区的湿地面积变化、空间分布及景观格局变化进行分析。结果表明:若尔盖地区湿地主要集中在四川若尔盖县,四川范围内3个时期湿地面积分别占各个时期研究区湿地面积的84.97%、78.33%和77.43%;湿地面积在2000-2020年呈缓慢增长趋势,湿地面积增加559.68 km^(2) ,其中甘肃地区湿地增加面积为423.23 km^(2) ,增长区域主要集中在甘肃玛曲县黄河左侧区域和四川阿坝县曼泽塘区域;地表覆盖变化趋势是以草地转化为湿地(水体)类别为主,变化面积为844.92 km^(2);湿地景观破碎化程度有所减缓,在2000-2010年降低了2.11,2010-2020年降低0.65,湿地景观格局更加稳定。

若尔盖草原生态系统服务价值评估与保护对策

为保护黄河上游最重要的水源涵养地之一——若尔盖高寒湿地草原,构建若尔盖草原生态系统综合评估体系,定量评估其生态系统服务价值并提出相应保护对策。结果表明:若尔盖草原生态系统服务功能重要性等级为中等以上的区域占比达90.86%,其中水源涵养功能重要性最高;生态系统质量等级为中等和良好的区域占比达84.85%;生态保护重要性等级为中等以上的区域占比达96.58%;生态环境敏感性等级为中敏感及以上的区域占比87.31%;生态系统恢复潜力等级为较弱和一般等级的区域占比86.79%。因此,亟需开展山水林田湖草沙冰一体化保护和修复工作。建立以水源涵养为导向的生态价值实现机制,推进黄河国家文化公园和相关生态项目建设,推动若尔盖生态和文化协同保护。

基于NSGA-Ⅱ算法的若尔盖高原高寒湿地生态修复格局优化

随着全球气候变暖和人类活动增强,高寒湿地面临着面积萎缩、动植物生境恶化、生态系统结构和功能退化等环境问题。以若尔盖高原高寒湿地为研究对象,基于生态系统稳态转化理论,使用湿地景观演变函数和第二代非支配排序遗传算法(non-dominated sorting genetic algorithmⅡ,NSGA-Ⅱ)分析1980—2015年7期湿地动态变化,计算多情景多目标函数值,选择适宜目标并基于社会经济生态可持续性发展、湿地生态系统稳态平衡原则,制订湿地修复优化策略。结果表明,可持续发展区、过度关注区与过度扰动区呈围绕发展,分别占湿地总面积的45.25%、17.27%与37.48%;基于NSGA-Ⅱ算法评价无偏好(等权最优)、经济效益最大化、生态效益最大化、空间紧凑度最大化、修复适宜性最大化5个目标下的湿地修复策略,无偏好策略函数值在经济效益、生态效益与湿地修复适宜性方面分别提升41.45%、9.18%和1.65%;基于社会经济可持续性发展的需求,构建保护优先、自然恢复、近自然恢复和适度修复4类若尔盖高原湿地生态修复空间优化格局。

若尔盖湿地土壤及水体重金属分布特征及健康风险评价

若尔盖湿地属典型的高寒湿地生态系统,是我国青藏高原生态屏障的重要组成部分.青藏高原地区重金属监测多集中在青藏高原西南部,针对若尔盖湿地重金属分布特征、污染来源及潜在人体健康风险尚未完全清楚.于2022年7月采集湿地土壤(退化湿地和未退化湿地)及地表水水样,分别对4种重金属(Cr、As、Cd和Pd)进行分析,阐述其浓度分布特征,并进行人体健康风险评估.结果表明:Cr、As、Cd和Pd在未退化湿地和退化湿地的浓度(mgkg-1)分别为6.23~26.19、2.06~45.00、0.01~0.63和1.32~10.87,7.56~23.56、5.10~21.87、0.01~0.43和2.16~11.13.参照《土壤环境质量——农用地土壤污染风险管控标准》,Cr、Pd、Cd和As达标率为100%、88%、94.4%、80%;地表水中Cd未检出,Cr、As和Pd浓度(μg·L-1)分别为0.04~1.14、0.15~23.77和0.01~0.94,符合国家地表水质量Ⅰ类标准.参照美国环保署(USEPA)和国际辐射防护委员(ICRP)标准,若尔盖湿地土壤总非致癌风险指数(HI)均小于1;总致癌风险(TCR)范围为2.53×10^(-6)~1.20×10^(-4),均在可接受致癌健康风险水平10-6~10-4数量级范围内;地表水中总健康风险指数(R)为1.97×10^(-6)~2.01×10^(-4),人体最大可接受风险水平为5.0×10^(-5),其中,21.4%地表水样品超过健康风险水平.As是导致健康风险的主导因子.研究结果可补充若尔盖地区环境背景值的基础数据库,为该地污染防治及环境质量改善提供一定的数据支撑.

若尔盖湿地水文连通及重要湿地斑块变化

湿地水文连通对维持及修复湿地生态系统结构及功能有重要意义。近年来,若尔盖湿地发生不同程度的退化,其水文连通也发生显著变化。为量化若尔盖湿地水文连通变化并识别重要湿地斑块,基于1977—2020年若尔盖Landsat遥感影像,利用监督分类法对若尔盖湿地斑块进行提取并分析了其面积变化;采用基于图论的景观连通度指数分析了若尔盖湿地1977—2020年水文连通动态变化,并采用重要性指数对重要斑块进行识别。结果表明,1977—2016年若尔盖湿地面积从2660.50减少到2378.53 km^(2),降幅为10.60%;2016—2020年若尔盖湿地面积逐渐恢复,2020年湿地面积已恢复至1977年的90.78%。若尔盖湿地结构和功能连通性随时间变化呈现先下降后上升的趋势。2016年若尔盖湿地结构和功能连通性分别为1977年的65.51%和60.73%,2020年恢复到1977年的70.23%和72.39%。若尔盖高重要性的湿地斑块主要位于现有保护地内,目前开展的湿地保护修复措施对恢复湿地水文连通性具有重要作用。