Southern Qinghai-Tibetan Plateau Research Articles

Anthropogenic activities altering the ecosystem in Lake Yamzhog Yumco, southern Qinghai-Tibetan Plateau

Lakes on the Qinghai-Tibet Plateau (QTP) have been subject to multiple environmental pressures from rapid climate change and intensified human activity in recent decades. However, their ecological effects on the lake ecosystem remain largely unclear due to the lack of long-term monitoring data. This study presented the environmental and ecological changes of the lake Yamzhog Yumco (Southern QTP) over the past three decades based on multi-proxy analysis (geochemistry and sedaDNA) on a high-time resolution sediment core. The result showed that the lake exhibited a continuous eutrophication process from 2004 CE, which has accelerated since 2014 CE. The nutrient enrichment was mainly attributed to anthropogenic emissions from the catchment. The sedimentary ancient DNA (sedaDNA) metabarcoding data registered a sensitive response of aquatic communities to the additional nutrient supply. Eukaryotic algae and aquatic invertebrate communities exhibited similar temporal dynamics, characterized by the increase in eutrophic taxa and the decrease in oligotrophic taxa. Change points analysis suggested that lake ecosystems underwent a slight ecological shift in 2003 CE and an abrupt shift in 2012 CE driven by nutrient enrichment. Quantitative analysis revealed that nutrients and human activity accounted for 27.9 % and 21.7 % of the temporal variation in aquatic communities, whereas climate change only explained 6.9 % of the total variation. From a paleolimnological view, our study supported that regional human activity could distinctly alter the nutrient level and aquatic community structure of lake ecosystems in the QTP. Considering that anthropogenic disturbance will continuously increase, it is crucial to strengthen the field monitoring of the lakes on the plateau and make effective management measures to avoid irreversible ecological consequences.

Soil nutrients and plant diversity affect ectomycorrhizal fungal community structure and functional traits across three subalpine coniferous forests.

The symbiotic relationship between ectomycorrhizal fungi (EMF) and the roots of host plants is significantly important in regulating the health and stability of ecosystems, especially of those such as the climate warming affected subalpine forest ecosystems. Therefore, from the coniferous forest systems located in the Southern Qinghai-Tibetan Plateau, root tips from three forest tree species: Pinus wallichiana, Abies spectabilis and Picea spinulosa, were collected to look for the local causes of EMF community composition and diversity patterns. The EMF colonization rate, diversity and taxonomic community structure were determined by morphotyping and sanger sequencing of the fungal ITS gene from the root tip samples. Soil exploration types were identified based on the morphologies of the ectomycorrhizas, coupled with soil properties analysis and plant diversity survey. Contrasting patterns of EMF community and functional diversity were found across the studied three forests types dominated by different coniferous tree species. In terms of associations between soil and EMF properties, the total phosphorus (TP) and nitrate (NO3−) contents in soil negatively correlated with the colonization rate and the Shannon diversity index of EMF in contrast to the positive relationship between TP and EMF richness. The soil total nitrogen (TN), ammonium (NH4+) and plant diversity together caused 57.6% of the total variations in the EMF taxonomic community structure at the three investigated forest systems. Whereas based on the soil exploration types alone, NH4+ and TN explained 74.2% of variance in the EMF community structures. Overall, the findings of this study leverage our understanding of EMF dynamics and local influencing factors in coniferous forests dominated by different tree species within the subalpine climatic zone.

Relative Contributions of Climate Change and Human Activities on Vegetation Productivity Variation in National Nature Reserves on the Qinghai–Tibetan Plateau

National nature reserves (NNRs) are at the forefront of conservation efforts on the Qinghai–Tibetan Plateau (QTP). However, few studies have examined the vegetation dynamics and their driving forces at the whole QTP scale. In this study, we used potential Net Primary Productivity (PNPP), actual NPP (ANPP), and human-activity-induced NPP (HNPP) to analyze the vegetation dynamics of 42 NNRs on the QTP. Further, we determined the driving factors of vegetation dynamics from 2000 to 2020. The results indicate that, during the 21 years studied, ANPP increased at 83.4% of the NNRs area on the QTP. Additionally, the contributions of climate change and anthropogenic factors to ANPP variation were 59.53% and 40.47%, respectively. The contribution of temperature to ANPP variation was considered high and stable, whereas the contribution of precipitation was relatively lower and variable. Residual analysis showed that human activities had both positive (51.30%) and negative effects (48.70%) on ANPP. Using Hurst exponent analysis, we found that 31.60% of the vegetation for the NNRs on the QTP will likely remain a persistent trend, and 65.4% will be stochastic in the future. By contrast, 3.00% of the vegetation mainly located in southern QTP would show a reverse trend, with most of them distributing in southern QTP, which deserves more attention. This study may help policymakers understand the relative impacts of climate change and human activities on vegetation in the different nature reserves on the QTP.

Functional and phylogenetic structures of pheasants in China

Biodiversity has been subjected to increasing anthropogenic pressures. It is critical to understand the different processes that govern community assembly and species coexistence under biogeographic processes and anthropogenic events. Pheasants (Aves: Phasianidae) are highly threatened birds and China supports the richest pheasant species worldwide. Unravelling the spatial patterns and underlying factors associated with multi-dimensional biodiversity of species richness (SR), functional diversity (FD), and phylogenetic diversity (PD) of pheasants in China is helpful to understand not only the processes that govern pheasant community assembly and species coexistence, but also pheasant biodiversity conservation. We used a total of 45 pheasant species in China and analyzed the SR, FD, PD, and functional and phylogenetic structures by integrating species distribution maps, functional traits and phylogenies based on 50 ​km ​× ​50 ​km grid cells. We further used simultaneous autoregressive (SAR) models to explore the factors that determined these patterns. The southern Qinghai-Tibetan Plateau (QTP), Hengduan Mountains, southwestern Mountains, the east of the Qilian Mountains, the Qinling, southern China displayed higher SR, FD, and PD, which were determined by elevation, habitat heterogeneity, temperature seasonality, and vegetation cover. Elevation primarily determined the functional and phylogenetic structures of the pheasant communities. Assemblages in the highlands were marked by functional and phylogenetic clustering, particularly in the QTP, whereas the lowlands in eastern China comprised community overdispersion. Clustered pheasant assemblages were composed of young lineages. Patterns of functional and phylogenetic structures and richness-controlled functional and phylogenetic diversity differed between regions, suggesting that phylogenetic structures are not a good proxy for identifying functional structures. We revealed the significant role of elevation in pheasant community assemblages in China. Highlands interacted with community clustering, whereas lowlands interacted with overdispersion, supporting the environmental filtering hypothesis. Biogeographical drivers other than anthropogenic factor determined biodiversity of pheasants at the present scale of China. This study provides complementary background resources for multi-dimensional pheasant biodiversity and provides insights into avian biodiversity patterns in China.

Prioritizing conservation of biodiversity in an alpine region: Distribution pattern and conservation status of seed plants in the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau (QTP) harbors abundant and diverse plant life owing to its high habitat heterogeneity. However, the distribution pattern of biodiversity hotspots and their conservation status remain unclear. Based on 148,283 high-resolution occurrence coordinates of 13,450 seed plants, we identified hotspots by integrating data from species richness, species complementarity and spatial phylogenetics. Nine hotspot areas were identified that contained 89% of species but covered only 7% of the total land area of the QTP. Four of nine hotspots were identified firstly, including west Nyainqentanglha Mountains, the middle reaches of Lancang and Jinsha Rivers, the upper reaches of Yellow River and Qilian Mountains. Analysis of conservation efficiency indicated national nature reserves (NNRs) covered 55% of the hotspots, whereas NNRs and provincial nature reserves (PNRs) together protected 73% of the hotspots. Conservation efforts, such as establishing new protected areas and upgrading the level of existing nature reserves, should be strengthened in the conservation gaps. Targeted conservation should be carried out for species endemic to QTP due to their narrow distribution range and low conservation effectiveness. Niche modeling for 336 threatened plants indicated there were apparent range shifts of suitable habitat areas from the eastern edge to the center of the plateau under future climate scenarios, and conservation priority should be focused on the southern QTP for where have stable habitats. • Different plant categories showed mismatched distribution pattern on the QTP • Nine biodiversity hotspot areas confined mostly to southeast QTP were identified • Current nature reserves are insufficient for conserving plant diversity • Suitable habitat areas of threatened plants will shrink under climate change • Targeted biodiversity protection should be carried out for species endemic to the QTP

CMIP5 climate projections for the Yamzhog Yumco Basin: an environmental testbed for alpine lakes

As projections of future climate change rely on global climate model (GCM) results, the performances of five GCMs included in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) are compared with ground observations (temperature and precipitation, 1961–2005) in southern Qinghai-Tibetan Plateau (TP). The comparison suggests that the models capture the climatological patterns of the observed climate but with cold and wet biases. Future (twenty-first century) trends based on the GCMs’ projections produced a warming trend, and the annual precipitation of the multi-model mean is generally projected to increase. Relative to the 1986–2005 mean, both the average annual temperature and precipitation of the five GCMs are projected to increase in the short term (2016–2035), medium term (2046–2065), and long term (2081–2100) under the scenarios of rcp2.6, rcp4.5, and rcp8.5. While the temperature and precipitation changes and the difference among scenarios become substantial as time evolves. Possible regional climate change impact on the Yamzhog Yumco Basin in southern TP is demonstrated by future lake area estimates based on a minimalist parametric model and the average annual precipitation predicted by the five GCMs: the lake area of Yamzhog Yumco (including Kongmu Co) will expand under the three scenarios for the three periods relative to the 1974–1993 mean. It is expected to obtain more reliable local information with the downscaling of GCM simulations to regional scales by using regional climate models for assessing regional hydrological impacts in more detail for further studies in the southern TP.

Quaternary climate change and habitat preference shaped the genetic differentiation and phylogeography of Rhodiola sect. Prainia in the southern Qinghai-Tibetan Plateau.

There are two long‐standing biogeographic hypotheses regarding the glacial survival of plant species in the Qinghai–Tibetan Plateau (QTP): the in situ survival hypothesis and the tabula rasa hypothesis. We tested these two hypotheses in a phylogeographic study of Rhodiola sect. Prainia, a monophyletic section with ecologically divergent lineages. Molecular data from the nuclear internal transcribed spacer, six plastid markers and 13 nuclear microsatellite loci were analyzed for 240 individuals from 19 populations of this section. Environmental data were used to analyze the niches of major phylogenetic lineages within this section and to model changes in their distributions since the Last Glacial Maximum (LGM). We found that Rhodiola sect. Prainia consists of three evolutionary lineages: all populations of R. stapfii, R. prainii populations at the southern edge of the QTP, and R. prainii populations in the interior part of the QTP. During the LGM, the survival of R. prainii in the interior part of the QTP corresponded with the in situ survival hypothesis, while R. stapfii most probably survived the LGM in a manner corresponding with the tabula rasa hypothesis. The evolutionary history of different lineages of this section was shaped by topography, climate change, and lineage‐specific habitat preferences.

Assessing revegetation effectiveness on an extremely degraded grassland, southern Qinghai-Tibetan Plateau, using terrestrial LiDAR and field data

The Qinghai-Tibetan Plateau (QTP) is one of the most difficult eco-regions for revegetation on degraded grassland because of its harsh environment. Micro-topography could affect habitat conditions important to ecological restoration on sandy land; however, the interaction between revegetation and micro-topography has been rarely reported on sand dunes of the QTP. Here, we quantified vegetation (including coverage, leaf area index (LAI), height, and crown diameter) and micro-topographic parameters (including elevation, slope, and aspect) to assess the effects of topography on revegetation using field observation data during 2008–2017 and terrestrial laser scanning (TLS) in 2017. The results showed that: 1) the tested plant species for revegetation has changed significantly from 2008 to 2017, and the current dominant plant species were mainly introduced from north China, including Hedysarum scoparium, H. fruticosum, and Artemisia sphaerocephala. 2) The effectiveness of revegetation has been improved remarkably over the past ten years. The vegetation coverage varies from 68.4% to 80.5% at four big quadrats of 20 m × 20 m, while the LAI value varies from 2.30 to 3.27, the shrub height ranges from 1.12 m to 7.57 m, and the crown diameter ranges from 0.24 m to 6.96 m. 3) A total of 153 shrubs were extracted in these four quadrats using TLS; and 56.9%, 21.6% and 10.5% of them are distributed on the southeastern, southern, and eastern aspects, respectively. The height and crown diameter of individual shrubs are significantly correlated with the local slope (p < 0.05) of which could affect the distribution of artificial seeding. These results suggest that aspect and slope are two key limiting factors for revegetation, and the habitat conditions on the southeastern and eastern aspects favor revegetation on valley-slope sand dunes. These findings provide a useful guidance in developing an integrated ecological restoration plan for sand dunes and selecting the best practice management of ecosystem services on degraded grassland on the QTP.

Simulation of land surface heat fluxes in permafrost regions on the Qinghai-Tibetan Plateau using CMIP5 models

The variations in land surface heat fluxes affect the ecological environment, hydrological processes and the stability of surface engineering structures in permafrost regions of the Qinghai-Tibetan Plateau (QTP). Based on observation data from a meteorological station in the Tanggula site in 2005, which is located in a permafrost region on the QTP, the performances of seventeen selected the phase 5 of the Coupled Model Intercomparison Project (CMIP5) were evaluated. The results showed that these simulations did not perform well using sensible heat flux, downward shortwave radiation or upward shortwave radiation, and differences exist among the models. The average multimodel ensemble results were similar to the observed land surface heat fluxes. The results revealed that the monthly average latent heat flux and the net radiation were small in December and January and large in May, June and July. The fluctuation in the soil heat flux was well correlated with the net radiation, and the sensible heat flux was negative in January and December in northwest of the Plateau. The latent heat flux was the strongest over the southeastern QTP from May to August, and it decreased over the northwestern QTP. In contrast, the sensible heat flux was the weakest over the southeastern QTP, and it gradually increased and became dominant over the northwestern QTP. The results also indicated that there was a good correlation between the surface heating field intensity and the net radiation, with a correlation coefficient of 0.99; this indicates stronger heating over the eastern QTP than over the western QTP and stronger heating over the southern QTP than over the northern QTP. Furthermore, the Bowen ratio was higher during the freezing and thawing stages than that during the completely thawed stage. This ratio was larger over the central and northeastern QTP and smaller along the northwest edge of the QTP, which was lower (range from −0.81 to 4.86) due to the overestimation of precipitation, a smaller difference between the simulated monthly average surface temperature and the observed air temperature, and a decrease in wind speed when using the CMIP5 models in the permafrost region of the QTP. This research provides a foundation for understanding land surface heat flux characteristics in the permafrost regions on the QTP under climate change.

Effects of permafrost thaw-subsidence on soil bacterial communities in the southern Qinghai-Tibetan Plateau

Permafrost thaws cause ground subsidence as the ground ice melts and drains away. Little is known about the effects of this permafrost thaw subsidence on bacterial communities. In this study, using Illumina sequencing methods, we investigated the structure of bacterial communities in the upper 50 cm of the soil in a typical permafrost thaw subsidence area on the southern Qinghai-Tibetan plateau. The micro topographies in the study area were classified as control, collapsing, and subsided types. Results showed that the organic carbon content in the collapsing areas was slightly lower than that in the control areas, while there was a substantial decrease in the subsided areas, with a loss of 23.6 ± 13.2% of organic carbon. The microbial carbon contents showed the highest values in collapsing areas. For all three types of soils, the most abundant microbial groups were Proteobacteria, Acidobacteria, and Bacteroidetes. The Non-metricmultidimensionalscaling (NMDS) results showed that the bacterial communities were different in the subsided areas than in the control and collapsing areas. In the control and collapsing areas, the soil bacterial communities showed a clear vertical distribution pattern with depth, which was not apparent in the subsided areas. The bacterial communities also correlated with soil variables such as carbon, moisture, nitrogen contents, and the C:N ratio. The ground subsidence can greatly change these variables. The results suggested that permafrost thaw subsidence had important effects on microbial communities via the changes of soil properties.

Permafrost and land cover as controlling factors for light fraction organic matter on the southern Qinghai-Tibetan plateau

Permafrost degradation can stimulate the decomposition of organic soil matter and cause a large amount of greenhouse gas emissions into the atmosphere. The light fraction organic matter (LFOM) is a labile substrate for microbial decomposition and probably plays an important role in future permafrost carbon cycles. However, little is known about the distribution of LFOM and its relationship with permafrost and environmental factors. Here, we investigated the light fraction carbon (LFC) and nitrogen (LFN) contents and stocks under meadows and wet meadows with different permafrost conditions on the southern Qinghai-Tibetan Plateau. Our results showed that LFC and LFN were mainly distributed in the upper 30cm of soils, and the sites with permafrost had significantly higher contents of LFC and LFN than those from the sites without existing permafrost. The LFC and LFN decreased sharply with depth, suggesting that the soil organic matter (SOM) in this area was highly decomposed in deep soils. Soil moisture and bulk density explained approximately 50% of the variances in LFC and LFN for all the sampling sites, while soil moisture explained approximately 30% of the variance in permafrost sites. Both the C:N ratios and LFC:LFN ratios in the sites with permafrost were higher than those in the sites without permafrost. The results suggested that the permafrost and land cover types are the main factors controlling LFOM content and stock, and that permafrost degradation would lead to a decrease of LFOM and soil C:N ratios, thus accelerating the decomposition of SOM.

The geography and timing of genetic divergence in the lizard Phrynocephalus theobaldi on the Qinghai-Tibetan plateau

The Qinghai-Tibetan Plateau (QTP) represents one of the earth’s most significant physical features and there is increasing interest in the historical generation of biodiversity within this region. We hypothesized that there should be clear geographically coherent genetic structuring within one of the world’s highest altitude lizards, Phrynocephalus theobaldi, due to considerable historical population fragmentation in this environment. This was tested using a major mitochondrial DNA (mtDNA) survey and sequencing of two nuclear markers (AME and RAG-1) from P. theobaldi, from across the southern QTP. A Bayesian method (BPEC) was used to detect four geographically structured mtDNA clusters. A Bayesian phylogenetic tree, together with associated dating analyses, supported four corresponding evolutionary lineages with a timing of 3.74–7.03 Ma for the most basal P. theobaldi split and Pliocene splits of 2.97–5.79 Ma and 2.40–5.39 Ma in the two daughter lineages. Himalayan uplift and changes in the Jilong basin may have contributed to these divergences, but uplift of the Gangdese mountains is rejected due to its timing. The nuclear markers appeared to be sorted between the four mtDNA groups, and species delimitation analyses supported the four phylogeographical groups as candidate species. The study contributes to our understanding of biodiversity on the QTP.

Evolutionary history of passerine birds (Aves: Passeriformes) from the Qinghai–Tibetan plateau: from a pre-Quarternary perspective to an integrative biodiversity assessment

As one of the most prominent topographical features on Earth, the Qinghai–Tibetan plateau (QTP) underwent a long and complex history of the QTP uplift from the collision of the Indian and the Eurasian plates to the present. At its southern and southeastern margins, it is flanked by the most significant hotspots of organismic diversity of the northern hemisphere (including birds), the Sino-Himalayan mountain forests. In contrast, the central plateau region itself harbours species-poor communities but also a good number of endemics that presumably evolved from rather ancient (pre-Pleistocene) phylogenetic lineage splits. We discuss the evolutionary history of QTP passerines from a twofold perspective including examples from our own research. First, we provide an overview of those alpine QTP endemics that represent late Miocene and Pliocene lineage splits, i.e. early colonisations to the central alpine QTP region. As an example, true rosefinches (genus Carpodacus) presumably evolved from a forested eastern QTP centre of origin and colonised the (semi-)open plateau habitats several times independently. Second, we discuss younger speciation events corresponding to phylogeographic east–west divides along the southern QTP margin. A multidisciplinary approach combining genetic, bioacoustic and morphological markers shed new light on the phylogenetic relationships of Pnoepyga wren babblers and on the intraspecific subdivision of the Buff-barred Warbler (Phylloscopus pulcher).

Phylogeographic evidence for a link of species divergence of Ephedra in the Qinghai-Tibetan Plateau and adjacent regions to the Miocene Asian aridification.

The Qinghai-Tibetan Plateau (QTP) has become one of the hotspots for phylogeographical studies due to its high species diversity. However, most previous studies have focused on the effects of the Quaternary glaciations on phylogeographical structures and the locations of glacial refugia, and little is known about the effects of the aridization of interior Asia on plant population structure and speciation. Here the chloroplast DNA (cpDNA) trnT-trnF and trnS-trnfM sequences were used to investigate the differentiation and phylogeographical history of 14 Ephedra species from the QTP and northern China, based on a sampling of 107 populations. The phylogeographical analysis, together with phylogenetic reconstruction based on combined four cpDNA fragments (rbcL, rpl16, rps4, and trnS-trnfM), supports three main lineages (eastern QTP, southern QTP, and northern China) of these Ephedra species. Divergence of each lineage could be dated to the Middle or Late Miocene, and was very likely linked to the uplift of the QTP and the Asian aridification, given the high drought and/or cold tolerance of Ephedra. Most of the Ephedra species had low intraspecific variation and lacked a strong phylogeographical structure, which could be partially attributed to clonal reproduction and a relatively recent origin. In addition, ten of the detected 25 cpDNA haplotypes are shared among species, suggesting that a wide sampling of species is helpful to investigate the origin of observed haplotypes and make reliable phylogeographical inference. Moreover, the systematic positions of some Ephedra species are discussed.

Mid-Holocene East Asian summer climate as simulated by the PMIP2 models

In the present study, datasets derived from twelve coupled ocean–atmosphere general circulation models (OAGCMs) in the Paleoclimate Modelling Intercomparison Project phase two were used to analyze the East Asian summer climate during the mid-Holocene (about 6000 calendar years ago). On the whole, the OAGCMs reproduced warmer and wetter summer climate conditions in East Asia during the mid-Holocene. The multi-model ensemble showed that in East Asia, the regionally-averaged summer surface air temperature (SAT) increased by 0.89 °C, summer precipitation was 5.8% higher, and an obviously strengthened southerly wind corresponded to a strong summer monsoon in the mid-Holocene when compared to preindustrial levels. The data-model comparison in China reveals a good agreement between the OAGCMs' results and the reconstructed changes in the summer SAT in East China during the mid-Holocene. In North China, the simulated SAT anomalies are 0.5 °C lower overall than reconstruction. In contrast, the OAGCMs fail to capture the strongest warming in the southern Qinghai–Tibetan Plateau. On the other hand, the simulated precipitation agrees well with proxy data except for in the central parts of China, where the simulated summer precipitation disagrees in sign with reconstruction. In addition, there is a large spread among the simulations, particularly over and around the Qinghai–Tibetan Plateau, and inter-model discrepancies are larger for precipitation than for SAT as a whole.

Extensional Stress Field in the Central and Southern Qinghai-Tibetan Plateau and the Dynamic Mechanism of Geothermic Anomaly in Yangbajain

The central and southern regions of the Qinghai-Tibetan plateau are famous geothermal active zones in the world. Temperature of boiling spring is as high as 93°C, heat flow value is up to 364 mW/m2 in some areas in the plateau. In the present analysis the relationships among the depth of lithospheric brittle fracture, stress field and mechanism of geothermal anomaly were investigated using the seismic dada from ISC and Chinese seismic net and other geophysical data. The results suggest that earthquakes about M6 frequently occur in the geothermal active zones, the seismicity is more active than the average inside the plateau. The events are distributed along the belts near N-S direction coinciding to that of fault-depression zones with intense geothermal activity. Events of intermediate hypocenters also appear in the high heat flow zone, the hypocenter depth stretches to about 100km. Normal fault type earthquakes due to the extensional stress field dominate the seismicity in the southern and central plateau, differing from the reverse or strike-slip faulting events dominating the seismicity in the low edges around the plateau, although the directions of the main compressive and extensional stress field coincide to those in the low edges. Extension along near E-W direction dominates the lithospheric stress field in and around the Yangbajain area. Such stress acts as deep as over 100km, to the bottom of lithosphere. Strong extensional stress field near E-W direction results in a series of large-scale normal faulting events or fractures near N-S direction in the geothermal anomalous zones in the plateau. The fractures are beneficial to the upwelling of heat flows with high temperature from the asthenosphere to the surface, and probably result in geothermal anomalous zones with high temperature in the plateau.