The Soil Drying Along the Increase of Warming Masks the Relation between Temperature and Soil Respiration in an Alpine Meadow of Northern Tibet

Soil respiration (Rs) is an important source of atmospheric CO2 flux and is sensitive to changes in soil nutrient and water contents. Despite extensive studies on the effects of enhanced atmospheric nitrogen (N) deposition and changes in precipitation (P) on Rs, few studies have taken into account the effects of interactions between these factors on Rs of alpine grasslands. To address these questions, we investigated the effects of N addition (10 g N m−2 yr−1), changes in precipitation (±50% precipitation), and their interaction on soil respiration and its components, including heterotrophic respiration (Rh) and autotrophic respiration (Ra),in a Tibetan alpine steppe during three consecutive growing seasons. We found that Rs differed in its response to N addition and precipitation regimes. Specifically, decreased precipitation led to a significant reduction in Rs during the last two years, whereas N addition minimally impacted Rs. Another important finding was that soil respiration components differed in their response to N addition and precipitation regimes. Nitrogen addition significantly enhanced Ra, whereas Rh was not altered in response to N addition. By contrast, the precipitation regime led to marked changes in Rh, but exhibited marginally significant effects on Ra. Therefore, our findings highlighted that soil respiration differed in its response to N addition and precipitation regimes mainly due to the different responses of soil respiration components to these factors. Therefore, carbon dynamics should take soil respiration components into account under global change scenarios.

Section: Discussionmentioning

confidence: 99%

Differential responses of heterotrophic and autotrophic respiration to nitrogen addition and precipitation changes in a Tibetan alpine steppe

Peng

Nie

et al. 2018

“…In a previous study, researchers set three warming treatments and found that the variation in soil respiration was explained by soil temperature for the control plots but was explained by soil moisture for the high warming treatment. Meanwhile, soil temperature and moisture together explained the variation in respiration for the low warming treatment 41 . These results also explained the above conclusion of this study.…”

Section: Discussionmentioning

confidence: 96%

“…The variation in reconstructed soils respiration before, after, and during the first precipitation event were explained by soil temperature, soil moisture, and both factors together, respectively. This was because the magnitude of change in soil temperature and moisture can affect the soils respiration response under various environmental conditions 10,11,41,42 . In a previous study, researchers set three warming treatments and found that the variation in soil respiration was explained by soil temperature for the control plots but was explained by soil moisture for the high warming treatment.…”

Section: Discussionmentioning

confidence: 99%

Effect of precipitation on respiration of different reconstructed soils

Lei

Han²

2020

Respiration and hydrothermal characteristics of four reconstructed soils in barren gravel land at a site in Shaanxi Province were monitored before, during, and after two precipitation events. Both precipitation events significantly reduced soil temperature but there were great fluctuations in temperature after the second precipitation event. Moreover, precipitation increased the moisture content of the reconstructed soils. Before the first precipitation event, the soil volumetric water content was relatively stable, while it gradually decreased before the second precipitation event. The first precipitation event significantly stimulated the respiration rate for all reconstructed soils, while the second precipitation event generally inhibited it, especially during the precipitation event. The key factors influencing respiration for different reconstructed soils were different between the precipitation events. When soil volumetric water content showed persistent variation before precipitation, soil moisture was the most influential factor. In contrast, if water content was stable, soil temperature was more influential. Soil moisture and temperature jointly influenced soil respiration before, during, and after the precipitation event, while soil moisture was always the most influential factor after precipitation. Soil respiration is the main component of the carbon cycle in terrestrial ecosystems. It is the second largest source of carbon emissions after atmospheric photosynthesis between the atmosphere and terrestrial ecosystems 1,2. Small changes in soil respiration significantly affected global carbon dynamics 3. A detailed analysis of the dynamics of soil respiration and its controlling factors is of great significance for accurately predicting changes in the carbon cycle under future climate change conditions 4. Soil temperature and soil moisture are the most important environmental factors affecting soil respiration 5,6 , and there is an interaction between the effects of soil temperature and soil moisture on soil respiration. Under conditions of future climate change, precipitation will change greatly, and the frequency of drought and extreme precipitation will increase 7. There are two different views on how precipitation might affect soil respiration. One is that precipitation will strongly and quickly stimulate soil respiration. This pulse is called the 'Birch effect' 8. However, it has been shown that the 'Birch effect' does not apply to all soils, and that for moist to wet soils, precipitation will instead inhibit soil respiration 9. The effect of precipitation on soil respiration is affected by environmental conditions such as soil temperature and moisture, and there is complex relationship of soil respiration with soil temperature and moisture. Several previous studies have demonstrated that there are many factors that could influence the response of soil respiration to precipitation events, including, both antecedent soil moisture and precipitation conditions 10 , different soil temperature and moistu...

“…Ts is one of the most important factors governing Rs processes on different spatial-temporal scales 69–76 , but much uncertainty remains regarding the influence of other factors on Rs 77–80 . In our study, Rs displayed a significant exponential correlation with Ts on the scale of diurnal variation (Figs 6 and 7), but no significant correlation at the seasonal scale.…”

Section: Discussionmentioning

confidence: 99%

“…5). Thus, some researchers have concluded that temperature does not adequately account for all Rs variations 76,81,82 , and that vegetation is also key factor influencing Rs on a seasonal scale 83,84 .…”

Section: Discussionmentioning

confidence: 99%

Dynamics of Soil Respiration in Alpine Wetland Meadows Exposed to Different Levels of Degradation in the Qinghai-Tibet Plateau, China

Gao

Wen

et al. 2019

The effects of degradation of alpine wetland meadow on soil respiration (Rs) and the sensitivity of Rs to temperature (Q 10 ) were measured in the Napa Lake region of Shangri-La on the southeastern edge of the Qinghai-Tibet Plateau. Rs was measured for 24 h during each of three different stages of the growing season on four different degraded levels. The results showed: (1) peak Rs occurred at around 5:00 p.m., regardless of the degree of degradation and growing season stage, with the maximum Rs reaching 10.05 μmol·m −2 ·s −1 in non-degraded meadows rather than other meadows; (2) the daily mean Rs value was 7.14–7.86 μmol·m −2 ·s −1 during the mid growing season in non-degraded meadows, and declined by 48.4–62.6% when degradation increased to the severely degraded level; (3) Q 10 ranged from 7.1–11.3 in non-degraded meadows during the mid growing season, 5.5–8.0 and 6.2–8.2 during the early and late growing seasons, respectively, and show a decline of about 50% from the non-degraded meadows to severely degraded meadows; (4) Rs was correlated significantly with soil temperature at a depth of 0–5 cm (p < 0.05) on the diurnal scale, but not at the seasonal scale; (5) significant correlations were found between Rs and soil organic carbon (SOC), between biomass and SOC, and between Q 10 and Rs (p < 0.05), which indicates that biomass and SOC potentially impact Q 10 . The results suggest that vegetation degradation impact both Rs and Q 10 significantly. Also, we speculated that Q 10 of alpine wetland meadow is probable greater at the boundary region than inner region of the Qinghai-Tibet Plateau, and shoule be a more sensitive indicator in the studying of climate change in this zone.