Altitude patterns of seed C, N, and P concentrations and their stoichiometry in an alpine meadow on the eastern Tibetan Plateau

Understanding the altitudinal patterns of plant stoichiometry in seeds is critical for characterizing important germination and dormancy strategies, soil seed bank composition, seed predation probability, efficiency of seed dispersal and seedling performance, and to predict how biodiversity might be influenced by climate change. However, our understanding of the altitudinal patterns of seed stoichiometry is extremely limited. In this study, we measured the concentrations of carbon (C), nitrogen (N) and phosphorus (P) in the seeds of 253 herbaceous species along an altitudinal transect (2,000–4,200 m) on the eastern Tibetan Plateau, China, and further to characterize seed C:N:P stoichiometry. The geometric means of C, N, and P concentrations were 569.75 mg/g, 34.76 mg/g, and 5.03 mg/g, respectively. The C:N, C:P, and N:P ratios were 16.39, 113.31, and 6.91, respectively. The seed C, N, and P concentrations and C:N:P ratios varied widely among major plant groups and showed significant altitudinal trends. In general, C, N, and P concentrations increased, whereas seed C:N:P ratios decreased with elevation. These results inform our understanding of the altitudinal patterns of seed stoichiometry and how to model ecosystem nutrient cycling

Historical context modifies plant diversity–community productivity relationships in alpine grassland

While most studies yield positive relationships between biodiversity (B) and ecosystem functioning (EF), awareness is growing that BEF relationships can vary with ecological context. The awareness has led to increased efforts to understand how contemporary environmental context modifies BEF relationships, but the role of historical context, and the mechanisms by which it may influence biodiversity effects, remains poorly understood. We examined how historical context alters plant diversity–community productivity relationships via plant species interactions in alpine grassland. We also tested how historical context modifies interactions between plants and arbuscular mycorrhizal (AM) fungi, which can potentially mediate the above processes. We studied biodiversity effects on plant community productivity at two grassland sites with different histories related to grazing intensity—heavy versus light livestock grazing—but similar current management. We assembled experimental communities of identical species composition with plants from each of the two sites in disturbed soil from a contemporary heavily grazed grassland, ranging in species richness from one to two, three and six species. Moreover, we carried out a mycorrhizal hyphae-exclusion experiment to test how plant interactions with AM fungi influence plant responses to historical context. We detected a significantly positive diversity–productivity relationship that was driven by complementarity effects in communities composed of plants from the site without heavy-grazing history, but no such relationship in plant communities composed of plants from the site with heavy-grazing history. Plants from the site with heavy-grazing history had increased competitive ability and increased yields in low-diversity communities but disrupted complementarity effects in high-diversity communities. Moreover, plants of one species from the site with heavy-grazing history benefitted more from AM fungal communities than did plants from the site without such history. Synthesis. Using the same experimental design and species, communities assembled by plants from two sites with different historical contexts showed different plant diversity–community productivity relationships. Our results suggest that historical context can alter plant diversity–community productivity relationships via plant species interactions and potentially plant–soil interactions. Therefore, considering historical contexts of ecological communities is of importance for advancing our understanding of long-term impacts of anthropogenic disturbance on ecosystem functioning

Soil Moisture but Not Warming Dominates Nitrous Oxide Emissions During Freeze–Thaw Cycles in a Qinghai–Tibetan Plateau Alpine Meadow With Discontinuous Permafrost

Large quantities of organic matter are stored in frozen soils (permafrost) within the Qinghai–Tibetan Plateau (QTP). The most of QTP regions in particular have experienced significant warming and wetting over the past 50 years, and this warming trend is projected to intensify in the future. Such climate change will likely alter the soil freeze–thaw pattern in permafrost active layer and toward significant greenhouse gas nitrous oxide (N2O) release. However, the interaction effect of warming and altered soil moisture on N2O emission during freezing and thawing is unclear. Here, we used simulation experiments to test how changes in N2O flux relate to different thawing temperatures (T5–5°C, T10–10°C, and T20–20°C) and soil volumetric water contents (VWCs, W15–15%, W30–30%, and W45–45%) under 165 F–T cycles in topsoil (0–20 cm) of an alpine meadow with discontinuous permafrost in the QTP. First, in contrast to the prevailing view, soil moisture but not thawing temperature dominated the large N2O pulses during F–T events. The maximum emissions, 1,123.16–5,849.54 μg m–2 h–1, appeared in the range of soil VWC from 17% to 38%. However, the mean N2O fluxes had no significant difference between different thawing temperatures when soil was dry or waterlogged. Second, in medium soil moisture, low thawing temperature is more able to promote soil N2O emission than high temperature. For example, the peak value (5,849.54 μg m–2 h–1) and cumulative emissions (366.6 mg m–2) of W30T5 treatment were five times and two to four times higher than W30T10 and W30T20, respectively. Third, during long-term freeze–thaw cycles, the patterns of cumulative N2O emissions were related to soil moisture. treatments; on the contrary, the cumulative emissions of W45 treatments slowly increased until more than 80 cycles. Finally, long-term freeze–thaw cycles could improve nitrogen availability, prolong N2O release time, and increase N2O cumulative emission in permafrost active layer. Particularly, the high emission was concentrated in the first 27 and 48 cycles in W15 and W30, respectively. Overall, our study highlighted that large emissions of N2O in F–T events tend to occur in medium moisture soil at lower thawing temperature; the increased number of F–T cycles may enhance N2O emission and nitrogen mineralization in permafrost active layer

Temporal and Spatial Dynamics of Carbon Storage in Qinghai Grasslands

Accurate quantification of ecosystem carbon storage dynamics is very important in regional ecological management. However, the dynamics of grassland carbon storage in Qinghai, China, are still unexplored. We investigated the temporal and spatial dynamics of carbon storage in the Qinghai grasslands from 1979 to 2018, using the spatially explicit Biome-BGCMuSo model. The average annual value of vegetation carbon density (VCD) was 52.71 gC·m−2. After 2000, VCD showed an overall increasing trend, with an average rate of 2.14 gC·m−2. The VCD was relatively high in the eastern and southeastern regions of Qinghai compared with that in the western and central areas. The increasing trend in VCD was mainly observed in the eastern and southeastern regions, while a decreasing trend was evident in western and central Qinghai. Annual soil organic carbon density (SOCD) in Qinghai grasslands generally increased from 1979 to 2018. After 2001, the SOCD increased by an average rate of 7.07 gC·m−2. The SOCD was relatively high in eastern and southeastern Qinghai compared with that in western and central Qinghai. The pronounced increasing trend of SOCD was mainly distributed in the southeast and northeast parts of Qinghai, while the decreasing trend was mainly distributed in the area between southeast and northeast Qinghai, and in the central and western regions. This study deepened our understanding of carbon dynamics in the Qinghai grasslands and provided data for guiding the ecological restoration and carbon management of local grasslands

Temporal and Spatial Dynamics of Carbon Storage in Qinghai Grasslands

Accurate quantification of ecosystem carbon storage dynamics is very important in regional ecological management. However, the dynamics of grassland carbon storage in Qinghai, China, are still unexplored. We investigated the temporal and spatial dynamics of carbon storage in the Qinghai grasslands from 1979 to 2018, using the spatially explicit Biome-BGCMuSo model. The average annual value of vegetation carbon density (VCD) was 52.71 gC·m−2. After 2000, VCD showed an overall increasing trend, with an average rate of 2.14 gC·m−2. The VCD was relatively high in the eastern and southeastern regions of Qinghai compared with that in the western and central areas. The increasing trend in VCD was mainly observed in the eastern and southeastern regions, while a decreasing trend was evident in western and central Qinghai. Annual soil organic carbon density (SOCD) in Qinghai grasslands generally increased from 1979 to 2018. After 2001, the SOCD increased by an average rate of 7.07 gC·m−2. The SOCD was relatively high in eastern and southeastern Qinghai compared with that in western and central Qinghai. The pronounced increasing trend of SOCD was mainly distributed in the southeast and northeast parts of Qinghai, while the decreasing trend was mainly distributed in the area between southeast and northeast Qinghai, and in the central and western regions. This study deepened our understanding of carbon dynamics in the Qinghai grasslands and provided data for guiding the ecological restoration and carbon management of local grasslands

The complete chloroplast genome and phylogenetic analysis of Astragalus scaberrimus Bunge 1833

Astragalus scaberrimus Bunge 1833 is a widespread perennial herb in northern China. The plant has white flowers and white hairs on the leaves and stems. To determine the chloroplast genome, total DNA was extracted from a sample and sequenced on the Illumina HiSeq4000 platform. After sequencing, the reads of chloroplast DNA were assembled and annotated via NOVOPlasty and PGA respectively. The chloroplast genome of this plant has a circular form with a length of 123,492 bp, a 34% GC content and IR loss. After annotation, a total of 113 genes were predicted for this cp genome, comprising 79 encoded proteins, 4 rRNAs and 30 tRNAs. The evolutionary history indicates that A. scaberrimus was grouped within Astragalus and formed a clade with Astragalus laxmannii with a 100% BS support value. The complete chloroplast genome can serve as a reference for future studies on molecular biology, evolution, population genetics, taxonomy and resource protection

Modeling the effect of grazing on carbon and water use efficiencies in grasslands on the Qinghai–Tibet Plateau

Abstract Background Carbon and water use efficiencies (CUE and WUE, respectively) are vital indicators of the adaptability of plants to environmental conditions. However, the effects of grazing and climate change on the spatiotemporal changes in CUE and WUE in Qinghai–Tibet Plateau grasslands (QTPG) are still unclear. Results Using the enhanced Biome-BGCMuSo model in combination with observed data, we estimated and analyzed the spatiotemporal variations in CUE and WUE and their responses to grazing in QTPG from 1979 to 2018. The mean annual CUE was 0.7066 in QTPG from 1979 to 2018 under the actual climate scenario. In general, the grassland CUE was low in the southeast and high in the northwest. Grazing generally decreased CUE in QTPG from 1979 to 2018, and there was an increasing trend in the difference in CUE between the grazing and nongrazing scenarios. The difference in CUE was generally greater in the northwest than in the southeast. The mean annual WUE was 0.5591 g C/kg H2O in QTPG from 1979 to 2018 under the actual climate scenario. After 2000, the grassland WUE exhibited a fluctuating upward trend. In general, the grassland WUE was greater in the southeast than in the northwest. Grazing generally decreased WUE in QTPG from 1979 to 2018, and there was an increasing trend in the difference in WUE between the grazing and nongrazing scenarios. The difference in WUE was generally greater in the northwest than in the southeast. Conclusions The findings of this study suggested that the spatiotemporal changes in CUE and WUE in QTPG were closely related to changes in the natural environment and grazing management

The complete chloroplast genome and phylogenetic analysis of Potentilla sischanensis Bunge ex Lehm

Potentilla sischanensis Bunge ex Lehm. is a widespread perennial herb in north China. The plant has little yellow flowers, and the petioles are white-tomentose and sparsely villous. To determine the chloroplast genome, total genomic DNA was extracted from fresh leaves and sequenced. The complete chloroplast genome was assembled and annotated. The chloroplast genome of this plant is a circular form with a length of 156,240 bp, including a large single-copy region (LSC, 85,748 bp), a small single-copy region (SSC, 18,566 bp), and two inverted repeats (IRs, 25,963 bp). A total of 132 genes were predicted, comprising 87 encoded proteins, 8 rRNAs and 37 tRNAs. The evolutionary history indicates that P. sischanensis was grouped within Potentilla and formed a clade with Potentilla chinensis and Potentilla stolonifera with a 100% bootstrap support value. The complete cp genome can serve as a reference for future studies on molecular biology, evolution, population genetics, taxonomy and resource protection

Quantifying and Mapping Human Appropriation of Net Primary Productivity in Qinghai Grasslands in China

Human appropriation of net primary productivity (HANPP) is an important indicator for assessing ecological sustainability. However, the spatiotemporal dynamics of HANPP in the Qinghai grasslands remain unclear. In this study, we used the spatially explicit Biome-BGCMuSo model to quantify and map HANPP in the Qinghai grasslands from 1979 to 2018. Generally, the actual net primary productivity (NPPact) was slightly lower than the potential net primary productivity (NPPpot), and the difference between the NPPpot and NPPact increased slightly over time. From 1979 to 2001, the NPPpot and NPPact were relatively stable; however, from 2001 to 2018, both showed significant fluctuating upward trends. From 1979 to 2018, HANPP showed a fluctuating upward trend from 6.36 to 31.85 gC/m2/yr, with an average increase of 2.14 gC/m2/yr. The average HANPP was 16.90 gC/m2/yr, which represented 18.80% of the NPPpot of Qinghai grasslands. High HANPP mainly occurred in eastern Qinghai, whereas it was low in central and western Qinghai. Conversely, from 1979 to 2018, the HANPP efficiency decreased in a fluctuating way from 98.28% to 72.05%, with an average annual decrease of 0.66%. The interannual variations in the HANPP efficiency and harvest were negatively correlated, with a correlation coefficient of −0.46 (p < 0.01). The average HANPP efficiency was 85.33%, and the values in most grids were between 80% and 100%, being relatively low in southern and eastern Qinghai. In rare cases, the HANPP efficiency was greater than 1. This study clarifies the details of spatiotemporal dynamics of HANPP in the Qinghai grasslands and indicates the need to optimize local management of grassland resources to ensure future ecological sustainability

Quantifying and Mapping Human Appropriation of Net Primary Productivity in Qinghai Grasslands in China

Human appropriation of net primary productivity (HANPP) is an important indicator for assessing ecological sustainability. However, the spatiotemporal dynamics of HANPP in the Qinghai grasslands remain unclear. In this study, we used the spatially explicit Biome-BGCMuSo model to quantify and map HANPP in the Qinghai grasslands from 1979 to 2018. Generally, the actual net primary productivity (NPPact) was slightly lower than the potential net primary productivity (NPPpot), and the difference between the NPPpot and NPPact increased slightly over time. From 1979 to 2001, the NPPpot and NPPact were relatively stable; however, from 2001 to 2018, both showed significant fluctuating upward trends. From 1979 to 2018, HANPP showed a fluctuating upward trend from 6.36 to 31.85 gC/m2/yr, with an average increase of 2.14 gC/m2/yr. The average HANPP was 16.90 gC/m2/yr, which represented 18.80% of the NPPpot of Qinghai grasslands. High HANPP mainly occurred in eastern Qinghai, whereas it was low in central and western Qinghai. Conversely, from 1979 to 2018, the HANPP efficiency decreased in a fluctuating way from 98.28% to 72.05%, with an average annual decrease of 0.66%. The interannual variations in the HANPP efficiency and harvest were negatively correlated, with a correlation coefficient of &minus;0.46 (p &lt; 0.01). The average HANPP efficiency was 85.33%, and the values in most grids were between 80% and 100%, being relatively low in southern and eastern Qinghai. In rare cases, the HANPP efficiency was greater than 1. This study clarifies the details of spatiotemporal dynamics of HANPP in the Qinghai grasslands and indicates the need to optimize local management of grassland resources to ensure future ecological sustainability