scholarly journals Contrasting effects of nitrogen and phosphorus addition on soil respiration in an alpine grassland on the Qinghai-Tibetan Plateau

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Fei Ren ◽  
Xiaoxia Yang ◽  
Huakun Zhou ◽  
Wenyan Zhu ◽  
Zhenhua Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Soil Respiration ◽  
Heterotrophic Respiration ◽  
Interactive Effects ◽  
Alpine Grassland ◽  
Organic Carbon Content ◽  
N Addition ◽  
Alpine Grasslands ◽  
Nitrogen And Phosphorus ◽  
P Addition

Abstract High soil organic carbon content, extensive root biomass, and low nutrient availability make alpine grasslands an important ecosystem for assessing the influence of nutrient enrichment on soil respiration (SR). We conducted a four-year (2009–2012) field experiment in an alpine grassland on the Qinghai-Tibetan Plateau to examine the individual and combined effects of nitrogen (N, 100 kg ha−1year−1) and phosphorus (P, 50 kg ha−1year−1) addition on SR. We found that both N and P addition did not affect the overall growing-season SR but effects varied by year: with N addition SR increased in the first year but decreased during the last two years. However, while P addition did not affect SR during the first two years, SR increased during the last two years. No interactive effects of N and P addition were observed, and both N addition and P addition reduced heterotrophic respiration during the last year of the experiment. N and P addition affected SR via different processes: N mainly affected heterotrophic respiration, whereas P largely influenced autotrophic respiration. Our results highlight the divergent effects of N and P addition on SR and address the important potential of P enrichment for regulating SR and the carbon balance in alpine grasslands.

scholarly journals Patterns of soil respiration and its temperature sensitivity in grassland ecosystems across China

2018 ◽  
Vol 15 (17) ◽  
pp. 5329-5341 ◽  
Author(s):  
Jiguang Feng ◽  
Jingsheng Wang ◽  
Yanjun Song ◽  
Biao Zhu
Keyword(s):  
Soil Respiration ◽  
Soil Temperature ◽  
Temperature Sensitivity ◽  
Annual Precipitation ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
Organic Carbon Content ◽  
Alpine Grasslands ◽  
Q10 Values ◽  
Grassland Types

Abstract. Soil respiration (Rs), a key process in the terrestrial carbon cycle, is very sensitive to climate change. In this study, we synthesized 54 measurements of annual Rs and 171 estimates of Q10 value (the temperature sensitivity of soil respiration) in grasslands across China. We quantitatively analyzed their spatial patterns and controlling factors in five grassland types, including temperate typical steppe, temperate meadow steppe, temperate desert steppe, alpine grassland, and warm, tropical grassland. Results showed that the mean (±SE) annual Rs was 582.0±57.9 g C m−2 yr−1 across Chinese grasslands. Annual Rs significantly differed among grassland types, and was positively correlated with mean annual temperature, mean annual precipitation, soil temperature, soil moisture, soil organic carbon content, and aboveground biomass, but negatively correlated with soil pH (p<0.05). Among these factors, mean annual precipitation was the primary factor controlling the variation of annual Rs among grassland types. Based on the overall data across Chinese grasslands, the Q10 values ranged from 1.03 to 8.13, with a mean (±SE) of 2.60±0.08. Moreover, the Q10 values varied largely within and among grassland types and soil temperature measurement depths. Among grassland types, the highest Q10 derived by soil temperature at a depth of 5 cm occurred in alpine grasslands. In addition, the seasonal variation of soil respiration in Chinese grasslands generally cannot be explained well by soil temperature using the van't Hoff equation. Overall, our findings suggest that the combined factors of soil temperature and moisture would better predict soil respiration in arid and semi-arid regions, highlight the importance of precipitation in controlling soil respiration in grasslands, and imply that alpine grasslands in China might release more carbon dioxide to the atmosphere under climate warming.

scholarly journals Quantifying Degradation Classifications on Alpine Grassland in the Lhasa River Basin, Qinghai-Tibetan Plateau

2019 ◽  
Vol 11 (24) ◽  
pp. 7067
Author(s):  
Wangya Han ◽  
Huiting Lu ◽  
Guohua Liu ◽  
Jingsheng Wang ◽  
Xukun Su
Keyword(s):  
Remote Sensing ◽  
Tibetan Plateau ◽  
Carbon Content ◽  
Accurate Determination ◽  
Total Carbon ◽  
Alpine Grassland ◽  
Organic Carbon Content ◽  
Grassland Degradation ◽  
Total Carbon Content

The Qinghai-Tibetan Plateau (QTP) has the world’s largest alpine grassland ecosystem. The QTP ecosystem is extremely fragile and suffers continuous degradation. An accurate determination of the status of alpine grassland is the first crucial step in monitoring its degradation. A novel method combining field survey with remote sensing information based on ecological indicators is proposed. The degradation classification of alpine grassland was identified by multivariate hierarchical analysis based on 270 field plots. The spatial pattern of alpine grassland degradation was mapped by determining remote sensing variables that corresponded to field indicators of the degradation classification system. The results showed that clustering analysis divided the degradation classification of alpine grassland into five classes: Non-Degraded (ND), Slightly Degraded (SLD), Moderately Degraded (MD), Severely Degraded (SD), and Extremely Degraded (ED). The most significant factors for alpine grassland degradation included the dominance of Cyperaceae plants, soil total nitrogen content, soil organic carbon content, soil total carbon content, soil bulk density, soil pH, dominance of miscellaneous plants, and elevation among all 17 variables. The assessment and mapping of alpine grassland degradation provide an important basis for alpine grassland protection and management, particularly at a large scale.

scholarly journals Squalene Found in Alpine Grassland Soils under a Harsh Environment in the Tibetan Plateau, China

Biomolecules ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 154 ◽  
Author(s):  
Xuyang Lu ◽  
Shuqin Ma ◽  
Youchao Chen ◽  
Degyi Yangzom ◽  
Hongmao Jiang
Keyword(s):  
Tibetan Plateau ◽  
Relative Abundance ◽  
Alpine Grassland ◽  
Gas Chromatography Mass Spectrometry ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Grassland Soils ◽  
Pyrolysis Gas ◽  
Microbial Characteristics ◽  
Microbial Biosynthesis

Squalene is found in a large number of plants, animals, and microorganisms, as well as other sources, playing an important role as an intermediate in sterol biosynthesis. It is used widely in the food, cosmetics, and medicine industries because of its antioxidant, antistatic, and anti-carcinogenic properties. A higher natural squalene component of lipids is usually reported as being isolated to organisms living in harsh environments. In the Tibetan Plateau, which is characterized by high altitude, strong solar radiation, drought, low temperatures, and thin air, the squalene component was identified in five alpine grasslands soils using the pyrolysis gas chromatography–mass spectrometry (Py-GC/MS) technique. The relative abundance of squalene ranged from 0.93% to 10.66% in soils from the five alpine grasslands, with the highest value found in alpine desert and the lowest in alpine meadow. Furthermore, the relative abundance of squalene in alpine grassland soils was significantly negatively associated with soil chemical/microbial characteristics. These results indicate that the extreme environmental conditions of the Tibetan Plateau may stimulate the microbial biosynthesis of squalene, and the harsher the environment, the higher the relative abundance of soil squalene.

scholarly journals Effects of One-Year Simulated Nitrogen and Acid Deposition on Soil Respiration in a Subtropical Plantation in China

Forests ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 235 ◽  
Author(s):  
Shengsheng Xiao ◽  
G. Geoff Wang ◽  
Chongjun Tang ◽  
Huanying Fang ◽  
Jian Duan ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Acid Deposition ◽  
Underlying Mechanism ◽  
N Deposition ◽  
Interactive Effects ◽  
N Addition ◽  
Mean Values ◽  
Acid Addition ◽  
One Year ◽  
Co Addition

Atmospheric nitrogen (N) and acid deposition have become global environmental issues and are likely to alter soil respiration (Rs); the largest CO2 source is from soil to the atmosphere. However, to date, much less attention has been focused on the interactive effects and underlying mechanisms of N and acid deposition on Rs, especially for ecosystems that are simultaneously subjected to elevated levels of deposition of both N and acid. Here, to examine the effects of N addition, acid addition, and their interactions with Rs, we conducted a two-way factorial N addition (control, CK; 60 kg N ha−1 a−1, LN; 120 kg N ha−1 a−1, HN) and acid addition (control, CK; pH 4.5, LA; pH 2.5, HA) field experiment in a subtropical plantation in China. Our results showed the following: (1) During the one-year observation period, the seasonal dynamics of Rs presented a single peak curve model, which was closely related to the surface soil temperature. (2) The simulated N deposition and acid deposition significantly decreased the Rs in the subtropical plantation. Compared to the CK plots, the LN and HN treatments reduced the annual mean values of Rs by 41% and 56%, and the annual mean values of Rs were inhibited by 26% and 31% in the LA and HA plots. The inhibition of N application on Rs was stronger than that of the simulated acid deposition. (3) Significant interactions between N addition and acid addition on Rs were detected, and Rs was significantly inhibited under four co-addition treatments. (4) The underlying mechanism and main reason for the responses of Rs to simulated N and acid deposition in this study might be the inhibition of soil microbial biomass and soil enzyme activity due to soil acidification under increased N and acid input.

scholarly journals Nitrogen Addition Exacerbates the Negative Effect of Throughfall Reduction on Soil Respiration in a Bamboo Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 724
Author(s):  
Yi Wang ◽  
Shirong Liu ◽  
Junwei Luan ◽  
Chen Chen ◽  
Chunju Cai ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Global Climate ◽  
N Deposition ◽  
Interactive Effects ◽  
Carbon Limitation ◽  
N Availability ◽  
Bamboo Forest ◽  
N Addition ◽  
Negative Effect ◽  
Throughfall Reduction

Impacts of drought events and nitrogen (N) deposition on forests are increasingly concerning in the context of global climate change, but their effects, in particular, their interactive effects on soil respiration and its components remain unclear. A two-factor random block field experiment was conducted at a subtropical Moso bamboo forest in Southwest China to explore the response of soil respiration (Rs), autotrophic respiration (Ra), and heterotrophic respiration (Rh) to throughfall re-duction and N addition. Our results showed that throughfall reduction significantly decreased Rs, which is mainly attributed to the decrease in Ra as a result of the decline in fine roots biomass. The N addition led to microbial carbon limitation hence significantly decreased Rh, and thus Rs. We also observed the negative effect of throughfall reduction on Rs was exacerbated by N addition, which is attributed to the significant reduction in Ra under the interaction between throughfall reduction N addition. Our findings suggest that Ra tended to respond more sensitively to potential drought, while Rh responds more sensitively to N deposition, and consequently, increased soil N availability caused by N deposition might aggravate the negative effect of expected drought on soil carbon cycling.

scholarly journals Soil Bacterial Communities and Diversity in Alpine Grasslands on the Tibetan Plateau Based on 16S rRNA Gene Sequencing

2021 ◽  
Vol 9 ◽  
Author(s):  
Hongmao Jiang ◽  
Youchao Chen ◽  
Yang Hu ◽  
Ziwei Wang ◽  
Xuyang Lu
Keyword(s):  
Tibetan Plateau ◽  
Bacterial Communities ◽  
Soil Bacteria ◽  
Alpine Grassland ◽  
Rrna Gene ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Soil Bacterial Communities ◽  
Soil Bacterial ◽  
Grassland Types

The Tibetan Plateau, widely known as the world’s “Third Pole,” has gained extensive attention due to its susceptibility to climate change. Alpine grasslands are the dominant ecosystem on the Tibetan Plateau, albeit little is known about the microbial community and diversity among different alpine grassland types. Here, soil bacterial composition and diversity in the upper soils of five alpine grassland ecosystems, alpine meadow (AM), alpine steppe (AS), alpine meadow steppe (AMS), alpine desert (AD), and alpine desert steppe (ADS), were investigated based on the 16S rRNA gene sequencing technology. Actinobacteria (46.12%) and Proteobacteria (29.67%) were the two dominant soil bacteria at the phylum level in alpine grasslands. There were significant differences in the relative abundance at the genus level among the five different grassland types, especially for the Rubrobacter, Solirubrobacter, Pseudonocardia, Gaiella, Haliangium, and Geodermatophilus. Six alpha diversity indices were calculated based on the operational taxonomic units (OTUs), including Good’s coverage index, phylogenetic diversity (PD) whole tree index, Chao1 index, observed species index, Shannon index, and Simpson index. The Good’s coverage index value was around 0.97 for all the grassland types in the study area, meaning the soil bacteria samplings sequenced sufficiently. No statistically significant difference was shown in other diversity indices’ value, indicating the similar richness and evenness of soil bacteria in these alpine grasslands. The beta diversity, represented by Bray–Curtis dissimilarity and the non-metric multidimensional scaling (NMDS), showed that OTUs were clustered within alpine grasslands, indicating a clear separation of soil bacterial communities. In addition, soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), pH, and soil water content (SWC) were closely related to the variations in soil bacterial compositions. These results indicated that soil bacterial taxonomic compositions were similar, while soil bacterial community structures were different among the five alpine grassland types. The environmental conditions, including SOM, TN, TP, pH, and SWC, might influence the soil bacterial communities on the Tibetan Plateau.

scholarly journals Temporal Variability of Precipitation and Biomass of Alpine Grasslands on the Northern Tibetan Plateau

2019 ◽  
Vol 11 (3) ◽  
pp. 360 ◽  
Author(s):  
Meng Li ◽  
Jianshuang Wu ◽  
Chunqiao Song ◽  
Yongtao He ◽  
Ben Niu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Temporal Variability ◽  
Alpine Grassland ◽  
Anthropogenic Factors ◽  
Time Interval ◽  
Sensitivity Index ◽  
Alpine Grasslands ◽  
Northern Tibetan Plateau ◽  
Grassland Plants ◽  
Precipitation Events

The timing regimes of precipitation can exert profound impacts on grassland ecosystems. However, it is still unclear how the peak aboveground biomass (AGBpeak) of alpine grasslands responds to the temporal variability of growing season precipitation (GSP) on the northern Tibetan Plateau. Here, the temporal variability of precipitation was defined as the number and intensity of precipitation events as well as the time interval between consecutive precipitation events. We conducted annual field measurements of AGBpeak between 2009 and 2016 at four sites that were representative of alpine meadow, meadow-steppe, alpine steppe, and desert-steppe. Thus, an empirical model was established with the time series of the field-measured AGBpeak and the corresponding enhanced vegetation index (EVI) (R2 = 0.78), which was used to estimate grassland AGBpeak at the regional scale. The relative importance of the three indices of the temporal variability of precipitation, events, intensity, and time interval on grassland AGBpeak was quantified by principal component regression and shown in a red–green–blue (RGB) composition map. The standardized importance values were used to calculate the vegetation sensitivity index to the temporal variability of precipitation (VSIP). Our results showed that the standardized VSIP was larger than 60 for only 15% of alpine grassland pixels and that AGBpeak did not change significantly for more than 60% of alpine grassland pixels over the past decades, which was likely due to the nonsignificant changes in the temporal variability of precipitation in most pixels. However, a U-shaped relationship was found between VSIP and GSP across the four representative grassland types, indicating that the sensitivity of grassland AGBpeak to precipitation was dependent on the types of grassland communities. Moreover, we found that the temporal variability of precipitation explained more of the field-measured AGBpeak variance than did the total amount of precipitation alone at the site scale, which implies that the mechanisms underlying how the temporal variability of precipitation controls the AGBpeak of alpine grasslands should be better understood at the local scale. We hypothesize that alpine grassland plants promptly respond to the temporal variability of precipitation to keep community biomass production more stable over time, but this conclusion should be further tested. Finally, we call for a long-term experimental study that includes multiple natural and anthropogenic factors together, such as warming, nitrogen deposition, and grazing and fencing, to better understand the mechanisms of alpine grassland stability on the Tibetan Plateau.

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