Variation Of Rs Research Articles

Effect of litter on soil respiration in a man-made Populus L. forest in a dune-meadow transitional region in China’s Horqin sandy land

Human disturbance and climate change both influence the input quantity of plant litter, significantly affecting soil respiration (Rs). However, what leads to a change of relationship between Rs in on-litter input (Rs(NL)) and natural litter input (Rs(CL)) is not yet fully understood. This study selected a man-made Populus forest in a dune-meadow transitional region to observe Rs(NL) and Rs(CL), soil temperature and soil moisture at a depth of 0–10 cm, groundwater depth between April and October in 2014 and 2015, and diurnal variations were carried out during the early, middle, and late stages of the growing seasons. Complex Rs diurnal patterns were observed in different growth stages. The soil moisture beyond field capacity inhibited root respiration and soil microbial activities, thus making Rs(NL) smaller than Rs(CL). When soil moisture was below field capacity with the increase of groundwater depth, dry air and low litter moisture content resulted in the shielding effect of the litter on Rs beyond its decomposition, thus making Rs(NL) consistently larger than Rs(CL). The temperature sensitivity was significantly affected by soil moisture. These results indicate that interactions among the quantity of litter, soil temperature, soil moisture and groundwater, which cause diurnal variations in Rs were diverse. Negative litter respiration may not be a measurement error, but caused by soil moisture which changes the relationship between Rs(NL) and Rs(CL). Thus, this study shows that plant litter has a significant influence on Rs in the dune-meadow transitional region. The findings of this study will provide useful information to understand these fragile ecosystems and the terrestrial carbon cycle.

Spatial-Temporal Changes of Soil Respiration across China and the Response to Land Cover and Climate Change

Soil respiration (Rs) plays an important role in the carbon budget of terrestrial ecosystems. Quantifying the spatial and temporal variations in Rs in China at the regional scale helps improve our understanding of the variations in terrestrial carbon budgets that occur in response to global climate and environmental changes and potential future control measures. In this study, we used a regional-scale geostatistical model that incorporates gridded meteorological and pedologic data to evaluate the spatial Rs variations in China from 2000 to 2013. We analysed the relationship between Rs and environmental factors, and suggest management strategies that may help to keep the terrestrial carbon balance. The simulated results demonstrate that the mean annual Rs value over these 14 years was 422 g/m2/year, and the corresponding total amount was 4.01 Pg C/year. The Rs estimation displayed a clear spatial pattern and a slightly increasing trend. Further analysis also indicated that high Rs values may occur in areas that show a greater degree of synchronicity in the timing of their optimal temperature and moisture conditions. Moreover, cultivated vegetation exhibits higher Rs values than native vegetation. Finally, we suggest that specific conservation efforts should be focused on ecologically sensitive areas where the Rs values increase significantly.

Soil respiration of a Moso bamboo forest significantly affected by gross ecosystem productivity and leaf area index in an extreme drought event.

Moso bamboo has large potential to alleviate global warming through carbon sequestration. Since soil respiration (Rs) is a major source of CO2 emissions, we analyzed the dynamics of soil respiration (Rs) and its relation to environmental factors in a Moso bamboo (Phllostachys heterocycla cv. pubescens) forest to identify the relative importance of biotic and abiotic drivers of respiration. Annual average Rs was 44.07 t CO2 ha−1 a−1. Rs correlated significantly with soil temperature (P < 0.01), which explained 69.7% of the variation in Rs at a diurnal scale. Soil moisture was correlated significantly with Rs on a daily scale except not during winter, indicating it affected Rs. A model including both soil temperature and soil moisture explained 93.6% of seasonal variations in Rs. The relationship between Rs and soil temperature during a day showed a clear hysteresis. Rs was significantly and positively (P < 0.01) related to gross ecosystem productivity and leaf area index, demonstrating the significance of biotic factors as crucial drivers of Rs.

Effects of ridge–furrow mulching on soil CO2 efflux in a maize field in the Chinese Loess Plateau

Ridge–furrow mulching system (RFMS) is widely used in arid and semi–arid areas, but its effect on soil respiration (Rs) and its components, including heterotrophic (Rh) and autotrophic respiration (Ra) are still poorly understood. In this study, CO2 flux from the soil of furrows and ridges was measured across different RFMS practices (i.e., three different ridge/furrow ratios) and conventional flat planting (CK). A trenching method was used to estimate the contribution of Rh to Rs. Compared with CK, RFMS significantly increased soil temperature of the ridge, promoted soil moisture of the furrow, and enhanced microbial diversity at the early crop growth stage, resulting in increased Rs and its components. The ridge soils exhibited much higher Rs (3.43 μmol m–2 s–1) than the furrow soils (2.98 μmol m–2 s–1) under all three RFMS practices. The contribution ratios of Rh to Rs across the different practices ranged from 50.4% to 59.6%. Soil temperature rather than soil moisture explained the seasonal variation of Rs and its components for both CK and RFMS. Nonetheless, high Rs and Rh values in RFMS did not induce a decline of soil organic carbon during the two–year experimental period. Improved root growth in RFMS practices may provide more exudates to the soil, thus offsetting soil carbon decomposition. Compared with CK, RFMS with ridge/furrow ratios of 40:70 cm, 55:55 cm, and 70:40 cm, significantly increased soil CO2 emissions by 10.6%, 19.6%, and 20.4%, respectively, while increasing maize yield by 26.1%, 36.4%, and 50.3%, respectively. Carbon emission efficiency (CEE) was significantly higher in RFMS than in CK in both years. This study suggests that, due to its high CEE, RFMS with a ridge/furrow ratio of 70:40 cm could be a highly promising strategy for sustaining crop productivity while minimizing environmental impacts.

Interactive effects of hydrological conditions on soil respiration in China's Horqin sandy land: An example of dune-meadow cascade ecosystem

Soil moisture (Ms) strongly influences dynamic changes in soil respiration (Rs) and is thus an important factor when predicting soil carbon emissions. However, the various sources of Ms (rainfall, groundwater, and condensation) exert complicated and uncertain effects on Rs. This study examined the growth seasonal variation (from April to October) of Rs and the diurnal variation in a cascade ecosystem consisting of sandy bare ground, a transitional artificial Populus forest, and a meadow Phragmites communis community in China's Horqin sandy land. Simultaneous measurements of the 0–10 cm depth soil temperature (Ts) and Ms, rainfall, the surface air relative humidity and the groundwater depth were collected. The results revealed that in sandy bare ground with Ms below field capacity, Ms had a greater impact on Rs than Ts, and rainfall could increase Rs. The effect of condensation on Rs during periods of continuous drought could not be ignored. In the meadowlands with Ms above field capacity, the groundwater affected Rs indirectly by regulating Ms and the relationship with Ts, and rainfall had an adverse effect on Rs. The effects of rainfall, Ms and Ts on Rs were minimum as Ms approached the saturation water content. In the transitional forest, Ms and Ts were the main factors controlling Rs. The most favorable Ms for Rs was close to the field capacity. The results emphasize that field capacity and saturation water content are the demarcation points of a soil carbon emissions prediction model, and the effect of different hydrological conditions and Ts on Rs at each segment are reconsidered accordingly. Ultimately, the carbon emission patterns of the cascade ecosystems in arid and semi-arid areas are extremely complicated and have to be considered specially for estimating terrestrial carbon emissions.

Responses of soil respiration to rainfall addition in a desert ecosystem: Linking physiological activities and rainfall pattern

The tight linkage between photosynthesis (An) and soil respiration (Rs) has been verified in many terrestrial ecosystems. However, it remains unclear whether this linkage occurs in desert ecosystems, where water is considered an important trigger of carbon cycling. A field experiment was performed under seven simulated rainfall amounts (0, 3, 5, 10, 15, 25, and 40 mm) with two co-existing desert plants (Reaumuria soongorica and Nitraria sphaerocarpa) in June (early growing season, EGS) and August (middle growing season, MGS) in 2016. An, Rs, predawn water potential (Ψpd), soil temperature (Ts) and soil moisture (Swc) were measured for each treatment or control plot for 3 weeks. Our objective was to examine the effects of rainfall pattern on Rs and physiological responses of the two plants and the relationships between Rs and biotic and abiotic factors. No obvious variations in Ψpd or An were found under small rainfall events. However, when the rainfall amount exceeded 10 mm, both plants responded strongly, and the response patterns of Rs showed trends similar to those of An, which varied between species and seasons. Moreover, rain additions of 3–40 mm significantly increased Rs, and the relative changes in Rs (ΔRs) of both species were much larger in the EGS than in the MGS. Importantly, abiotic factors may have controlled the variations in Rs under small rain events while An played a more important role in regulating the variations in Rs when the rainfall amount exceeded 10 mm for both species, suggest that the rainfall pattern–driven changes in Rs composition interact with physiological activity and abiotic factors to regulate the response of Rs to rainfall variability in desert ecosystems. Thus, climate change in the coming decades may lead to carbon sequestration by desert plants, which may cause desert ecosystems to act as carbon sinks.

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

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&lt;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.

Effects of experimental warming and increased precipitation on soil respiration in an alpine meadow in the Northern Tibetan Plateau

Uncertainty on the response of soil respiration (Rs) to warming and increased precipitation on the Tibetan Plateau can limit our ability to predict how alpine ecosystems will respond to future climate change. Based on a warming (control, low- and high-level) and increased precipitation (control, low- and high-level) experiment, the response of Rs to experimental warming and increased precipitation was examined in an alpine meadow in the Northern Tibetan Plateau from 2014 to 2017. The low-level warming increased soil temperature (Ts) by 1.19°C and decreased soil moisture (SM) by 0.02m3m−3, whereas the high-level warming increased Ts by 2.88°C and decreased SM by 0.04m3m−3 over the four growing seasons in 2014–2017. The low- and high-level increased precipitation did not affect Ts, but increased SM by 0.02m3m−3 and 0.04m3m−3, respectively, over the four growing seasons in 2014–2017. No significant main and interactive effects of experimental warming and increased precipitation on Rs were observed over the four growing seasons in 2014–2017. In contrast, there was a significant inter-annual variation of Rs in 2014–2017. There was a marginally significant quadratic relationship between the effect of experimental warming on Rs and warming magnitude. There was a negligible difference of Rs between the low- and high-level increased precipitation over the four growing seasons in 2014–2017 and Rs also showed a quadratic relationship with precipitation. Therefore, experimental warming and increased precipitation did not change Rs and Rs responded nonlinearly to experimental warming and increased precipitation in the alpine meadow in the Northern Tibetan Plateau. Growing season precipitation may play a more important role than experimental warming and increased precipitation in affecting Rs in the alpine meadow in the Northern Tibetan Plateau.

Measurement strategies to account for soil respiration temporal heterogeneity across diverse regions

Soil respiration (Rs) rates fluctuate daily and seasonally; therefore, the timing of measurements is critical when estimating the daily mean and scaling up to annual Rs rates. Temporal fluctuations also vary with climate and biome, yet the current recommendation for when to measure Rs (e.g., 09:00 to 12:00) has not been evaluated for different climates, biomes, and seasons. To provide more refined recommendations for measuring Rs, we: 1) analyzed the diurnal and seasonal fluctuations of Rs and tested the accuracy of typical measurement practices under different climates and biomes, and 2) identified the measurement frequency necessary for different climates and biomes to achieve certain levels of accuracy in estimating annual Rs. Across biomes, diurnal variation in Rs is considerable in spring and summer, moderate in autumn, and minimal in winter, and closely related with soil temperature. Based on these diurnal patterns, the best measurement time for estimating the daily mean Rs was 10:00 in all climates and biomes, which is within the recommended range of 9:00 and 12:00 previously identified for temperate forests. Measurements made between 20:00 and 23:00 also accurately estimated the daily mean Rs. Regions with high plant coverage over the year have lower seasonal variation and require less measurement frequency. For global scale estimates, Rs needs to be measured once per day to attain an accuracy of ±10% of the Rs population mean with 95% confidence, and once per month to achieve ±30% with a confidence of 80%. Results from this study provide guidelines that reduce measurement frequency while retaining reasonable accuracy for better Rs estimates using manual chamber systems.

Negative effect of nitrogen addition on soil respiration dependent on stand age: Evidence from a 7-year field study of larch plantations in northern China

Increasing anthropogenic nitrogen (N) deposition will affect the global carbon (C) cycle, although the mechanisms and magnitudes of its effects are not yet fully understood. Soil respiration (Rs) and its components (i.e., heterotrophic (Rh) and autotrophic (Ra) respiration) represent the largest flux of carbon dioxide (CO2) from terrestrial ecosystems to the atmosphere. However, the potentially interactive effect of N addition and stand age on Rs in forests remains unclear. We conducted a 7-year (2010–2016) field experiment in three differently-aged larch plantations (11-, 20-, and 45-year-old, representing sapling, intermediate, and mature stands) to investigate the effects of different N addition rates (control: no N addition; low-N addition, N20: 20 kg N ha−1 year−1; and high-N addition, N50: 50 kg N ha−1 year−1) on Rs. We found significant seasonal variation in Rs, Rh, and Ra, with levels highest in summer and lowest in autumn. Rs correlated strongly with soil temperature and weakly with soil moisture, and Rs, Rh, and Ra increased exponentially with soil temperature. The temperature sensitivity (Q10) of Rs was lowest in the mature stand, which suggests that it will sequester relatively more C in a warmer climate. The Q10 of Ra was higher than that of Rh, indicating that it contributed proportionally more to the total soil CO2 efflux. N addition had no significant effect on Q10. Rs in the intermediate stand was significantly lower than Rs in the sapling and mature stands, which may be due to its lower soil temperature and poorer substrate quality. N addition decreased Rs by an average of 9%, but significant effects were only observed in the sapling and intermediate stands. The negative influence of N addition on Rs was largely dependent on soil temperature, with more negative effects observed in the summer when temperatures were higher, and attributable to a reduction in either Ra in the intermediate stand or Rh in the sapling stand. We hypothesize that N limitation in the young trees was alleviated by fertilization, which decreased C allocation to roots, whereas N addition may have exerted a more negative influence on soil microbial activity in the sapling stand. In summary, our results highlight the importance of stand age in regulating the negative effects of N addition on Rs and its components, which has implications for projecting the global C–climate feedback in the future.

Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert

Abstract. Soil respiration (Rs) is the most important source of carbon dioxide emissions from soil to atmosphere. However, it is unclear what the interactive response of Rs would be to environmental changes such as elevated precipitation, nitrogen (N) deposition and warming, especially in unique temperate desert ecosystems. To investigate this an in situ field experiment was conducted in the Gurbantunggut Desert, northwest China, from September 2014 to October 2016. The results showed that precipitation and N deposition significantly increased Rs, but warming decreased Rs, except in extreme precipitation events, which was mainly through its impact on the variation of soil moisture at 5 cm depth. In addition, the interactive response of Rs to combinations of the factors was much less than that of any single-factor, and the main response was a positive effect, except for the response from the interaction of increased precipitation and high N deposition (60 kg N ha−1 yr−1). Although Rs was found to show a unimodal change pattern with the variation of soil moisture, soil temperature and soil NH4+-N content, and it was significantly positively correlated to soil dissolved organic carbon (DOC) and pH, a structural equation model found that soil temperature was the most important controlling factor. Those results indicated that Rs was mainly interactively controlled by the soil multi-environmental factors and soil nutrients, and was very sensitive to elevated precipitation, N deposition and warming. However, the interactions of multiple factors largely reduced between-year variation of Rs more than any single-factor, suggesting that the carbon cycle in temperate deserts could be profoundly influenced by positive carbon–climate feedback.

Variation and repeatability of cutaneous water loss and skin resistance in relation to temperature and diel variation in the lizard Sceloporus consobrinus.

Variation in rates of water loss has been proposed to be an important mechanism in the survival of terrestrial organisms, as high rates of water loss in desiccating environments may lead to hydric stress and death. Vapor density deficit, the driving force for evaporative water loss, increases exponentially as temperature increases. Acute temperature changes may be the result of daily behavioral thermoregulation of ectotherms, which may influence the among individual variation rates of water loss. The goals of this study were to determine (1) how rates of cutaneous water loss (CWL) and skin resistance (Rs) are affected by acute temperature acclimation, (2) how rates of CWL and Rs vary throughout the day allowing behavioral thermoregulation and (3) the repeatability of CWL and Rs within and among sampling periods. We measured CWL and calculated skin resistance (Rs) of 30 male Sceloporus consobrinus lizards across three summers. We measured CWL on the dorsal and ventral surface of each lizard at 23°C followed by measurements at 35°C, and three separate times throughout the day. We found a significant increase in Rs and decrease in CWL at increased acclimation temperatures (35°C), a significant difference in CWL and Rs throughout the day allowing behavioral thermoregulation, and support for the repeatability of CWL and Rs. Our results demonstrate variability in CWL and Rs in relation to temperature acclimation and thermoregulation, but mixed evidence for repeatability across treatments. Our results suggest other factors, such as peripheral blood flow, may be influencing the inter-individual variation in CWL and Rs.

Seasonal and diurnal patterns of soil respiration in an evergreen coniferous forest: Evidence from six years of observation with automatic chambers.

Soil respiration (Rs) plays a key role in the carbon balance of forest ecosystems. There is growing evidence that Rs is strongly correlated with canopy photosynthesis; however, how Rs is linked to aboveground attributes at various phenological stages, on the seasonal and diurnal scale, remains unclear. Using an automated closed dynamic chamber system, we assessed the seasonal and diurnal patterns of Rs in a temperate evergreen coniferous forest from 2005 to 2010. High-frequency Rs rates followed seasonal soil temperature patterns but the relationship showed strong hysteresis. Predictions of Rs based on a temperature-response model underestimated the observed values from June to July and overestimated those from August to September and from January to April. The observed Rs was higher in early summer than in late summer and autumn despite similar soil temperatures. At a diurnal scale, the Rs pattern showed a hysteresis loop with the soil temperature trend during the seasons of high biological activity (June to October). In July and August, Rs declined after the morning peak from 0800 to 1400 h, although soil temperatures continued to increase. During that period, figure-eight-shaped diurnal Rs patterns were observed, suggesting that a midday decline in root physiological activity may have occurred in early summer. In September and October, Rs was higher in the morning than in the night despite consistently high soil temperatures. We have characterised the magnitude and pattern of seasonal and diurnal Rs in an evergreen forest. We conclude that the temporal variability of Rs at high resolution is more related to seasons across the temperature dependence.

间伐和改变凋落物输入对华北落叶松人工林土壤呼吸的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 间伐和改变凋落物输入对华北落叶松人工林土壤呼吸的影响 DOI: 10.5846/stxb201703160449 作者: 作者单位: 北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083,北京林业大学林学院 北京 100083 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2016YFD0600205） Thinning treatment and litterfall changes influence soil respiration in a Larix principis-rupprechtii plantation Author: Affiliation: Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University Fund Project: National Key R&D Plan 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:作为森林生态系统的第二大碳通量，土壤呼吸在全球碳循环和气候变化中发挥着重要作用。通过探究土壤呼吸对间伐和改变凋落物的响应规律以及响应之间的联系，能够为准确评价森林碳循环提供依据。针对不同强度（对照、轻度、中度、重度）间伐后的华北落叶松人工林，2016年5月至10月采用LI-8100土壤碳通量测量系统对其原状、凋落物去除、凋落物加倍的土壤呼吸进行观测。结果表明：土壤呼吸在生长季的8月份达到最高值，呈现出明显的季节动态。不同林分间伐处理下，中度间伐显著促进了土壤呼吸，使平均土壤呼吸速率升高了15.66%，轻度间伐和重度间伐对土壤呼吸的影响不显著；不同凋落物处理下，去除凋落物使平均土壤呼吸速率降低了40.16%，加倍凋落物使平均土壤呼吸速率升高了16.06%。中度间伐使土壤呼吸生长季通量增加了55.06 g C/m2；去除凋落物使土壤呼吸生长季通量减少了153.48 g C/m2，加倍凋落物使土壤呼吸生长季通量增加了79.87 g C/m2。土壤呼吸速率与土壤温度呈显著指数相关，而与土壤湿度无显著相关。不同林分间伐处理下，土壤呼吸的温度敏感性指数（Q10）为2.36-3.46，轻度间伐下Q10值最高；凋落物去除和加倍均降低了土壤呼吸的温度敏感性。土壤温湿度对土壤呼吸存在着显著影响，能够解释土壤呼吸28.7%-62.3%的季节变化。研究结果表明间伐和凋落物处理对华北落叶松人工林土壤CO2释放的影响表现出一定的交互作用，中度间伐和加倍凋落物的交互作用对土壤呼吸的促进作用显著大于单一因子。可见，间伐作业通过改变土壤微环境和凋落物量，对土壤呼吸以及森林生态系统碳循环产生着重要影响。 Abstract:Soil respiration (Rs), the second largest site of carbon flow in the forest ecosystem carbon budget, plays an important role in the global carbon (C) cycle and climate change. Understanding the effects of forest management practices (e.g. thinning) on Rs is crucial for the accurate estimation of forest carbon cycling. Simultaneously, aboveground litter management practices (removal, addition, and so on) can also influence Rs. However, little is known about the response of Rs to thinning and its relationship with the changes in litter production induced by thinning. We aimed to quantify the response of Rs rate to different thinning intensities and to explore the relationships between Rs and soil temperature and moisture as a result of different litter management practices. A thinning manipulation experiment was conducted in a Larix principis-rupprechtii plantation in Shanxi province, China, with the following treatments:heavy thinning, moderate thinning, low thinning and no thinning. In addition, three treatments-litterfall removal, litter addition and normal litterfall-were applied to analyze the relationship between differences in litter input and Rs. Rates of soil respiration were measured twice a month using the LI-8100 Automated Soil CO2 Flux System from May to October 2016, while soil temperature and moisture at a depth of 5 cm were measured using temperature and moisture probes and data loggers. A significant difference was noted in Rs among the different thinning treatments (P < 0.05). Clear monthly variations in Rs were noted in the growing season, and Rs reached its peak value in August. Overall, moderate thinning increased Rs rate during the growing season by 15.7% from that of the no-thinning treatment. During the growing season, the Rs rate was lower by 40.16% with litterfall removal than that of normal litterfall; however, Rs rate was higher by 16.06% with litter addition than that of normal litterfall. Moderate thinning increased accumulative Rs by 55.06 g C/m2 during the growing season. Under litter removal conditions, accumulative Rs decreased by 153.48 g C/m2 during the growing season, while accumulative Rs increased with litter addition by 79.87 g C/m2. During the growing season, Rs exhibited significant exponential relationships with soil temperature, while there were no significant differences in soil moisture among the various treatments. Temperature sensitivity (Q10) values of Rs ranged from 2.36 to 3.46 in the various thinning intensities, with the highest Q10 value in the low thinning stand. The Q10 value were lower with the litter removal and litter addition treatments than those of normal litterfall. The interaction of soil temperature and moisture had a significant effect on Rs. The best fitting model with temperature and moisture explained 28%-62% of the variation in Rs. The results indicated that the interaction between thinning treatments and litter changes has a significant effect on the Rs in L. principis-rupprechtii plantations. The compound effect of moderate thinning and litter addition on Rs is significantly greater than that of any single factor. In conclusion, thinning played a considerable role in altering Rs and carbon cycle in forest ecosystems by influencing the soil micro-environment and litter production rates. 参考文献 相似文献 引证文献

Effects of forest cover types and environmental factors on soil respiration dynamics in a coastal sand dune of subtropical China

Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration (R s) for secondary natural Litsea forest and plantations of casuarina, pine, acacia and eucalyptus. Results show that significant diurnal variations of R s occurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of R s were found in all five forest stands. R s changed exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of R s variations. Positive relationships between seasonal R s and soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter (Q 10 value) of R s ranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual R s was highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter, and soil properties (pH, total N, available P, and exchangeable Mg) were also significant factors.

Characterization and modelling of soil CO2 efflux in old and young irrigated citrus orchards

Soil respiration (Rs) represents the largest CO2 efflux to the atmosphere of terrestrial ecosystems. The regular alternation of wet and dry soil strips prevailing in irrigated orchards is a singular case-study among ecosystems as it may help to understand the impact of the spatial variability of abiotic factors on soil respiration in orange orchards having contrasting age and structural heterogeneity. We characterised Rs in adult (AO) and young (YO) drip-irrigated orange orchards with special focus on the main factors driving Rs site-by-site and across-sites. Tree structure (leaf area index, LAI) was measured fortnightly during two years, whereas Rs, soil temperature (Ts) and moisture (θs) were measured during the same period in dry and wet longitudinal transects parallel to the tree rows. The data sets collected in the field were used to carry out a modelling exercise aimed to predict Rs from only abiotic factors (here Ts and θs) or from a combination of abiotic and biotic (LAI) factors. The modelling results indicated that the seasonal changes of Rs were temperature-driven in predominantly wet transects and moisture-driven in predominantly dry ones; and that the emerging seasonal pattern of spatially-weighted mean soil respiration (Rs,mean) was mainly explained by abiotic factors. An abiotic model assuming a constant value of the reference respiration (Rb,10=Rs at Ts=10°C) was found suitable to describe the temporal variations in Rs,mean within an orchard, but was not able to reproduce the differences in Rs between orchards (R2=0.20). The model fitness was strongly improved (R2=0.80) when Rb,10 was assumed an increasing function of LAI, suggesting that LAI might be a suitable biotic variable for predicting the magnitude of soil respiration in citrus orchards.

Does precipitation affects soil respiration of tropical semiarid grasslands with different plant cover types?

Examination of the effects of altered precipitation and atmospheric temperature patterns on ecosystem processes are an active area of research. Influences of these climate factors may change when plant cover and species composition are disturbed as a consequence of land use change altering ecosystem processes, such as soil respiration. We addressed the following question: how does experimentally manipulated reduction in the size of each precipitation event influence soil respiration fluxes (Rs) in a tropical semiarid grassland with different plant cover and species composition? Rainout shelters were installed over eight yr old planted monospecific plots (4m2) of Bouteloua gracilis, the keystone species of the grassland biome, and over mixed grassland plots in sites that recovered from abandoned agricultural land, allowing full or a 50% reduction of ambient precipitation. Soil respiration rates as well soil temperature (Tsoil) and soil water content (SWC), as controlling factors, were monitored. Overall, SWC was the most important control for Rs explaining ∼70% of its variability, followed by Tsoil which explained ∼25% and plant cover type having a minor effect (3%) explaining Rs variability. Still, Rs exhibited differential responses when comparing plant cover types; SWC in the mixed grassland had up to 90% relative influence on Rs as compared to 10% by Tsoil. In contrast, Rs rates in monospecific B. gracilis plots exhibited less overall variability considering SWC (55–60%) and Tsoil (40–45%), suggesting that grasslands dominated by the keystone species are more resilient and better buffer the effects of extreme climatic drought conditions on ecosystem processes.

Environmental controls on soil respiration in alpine meadow along a large altitudinal gradient on the central Tibetan Plateau

Little is known about how environmental factors modify spatiotemporal variations of soil respiration (Rs) and its temperature sensitivity (Q10) in alpine grasslands on the Tibetan Plateau (TP). We conducted an altitudinal experiment across lower and upper limits of alpine meadows on the central TP. Soil respiration and related environmental factors were observed at each of 7 altitudes (from 4400m to 5200m) during the growing seasons of 2012 and 2013. Soil temperature (ST) rather than soil moisture (SM) was the major abiotic factor controlling seasonal variation of Rs in alpine grasslands across the seven altitudes. In addition to ST and SM, plant biomass is also an important factor controlling seasonal trends of Rs. The seasonal mean Rs increased with increasing altitude up to 4950m, and then decreased above 4950m. Below-ground biomass (BGB), ST and SM have direct effects on Rs, and the altitudinal trends of Rs can be well-predicated from these three variables (R2=0.65). The Q10 values of seasonal Rs generally increased with increasing altitude. Alpine meadows generally have higher Q10 values comparing with steppe meadows. Along the altitude gradient, Q10 was negatively correlated with ST, but positively correlated with SM, AGB, BGB and SOC. The results suggested that future climate warming would enhance Rs rates more dramatically in high-altitudes grasslands, and changes in vegetation structure under climate change might have a large impact on Rs in these alpine grasslands.

Soil water regulates the control of photosynthesis on diel hysteresis between soil respiration and temperature in a desert shrubland

Abstract. Explanations for the occurrence of hysteresis (asynchronicity) between diel soil respiration (Rs) and soil temperature (Ts) have evoked both biological and physical mechanisms. The specifics of these explanations, however, tend to vary with the particular ecosystem or biome being investigated. So far, the relative degree of control of biological and physical processes on hysteresis is not clear for drylands. This study examined the seasonal variation in diel hysteresis and its biological control in a desert-shrub ecosystem in northwest (NW) China. The study was based on continuous measurements of Rs, air temperature (Ta), temperature at the soil surface and below (Tsurf and Ts), volumetric soil water content (SWC), and photosynthesis in a dominant desert shrub (i.e., Artemisia ordosica) over an entire year in 2013. Trends in diel Rs were observed to vary with SWC over the growing season (April to October). Diel variations in Rs were more closely associated with variations in Tsurf than with photosynthesis as SWC increased, leading to Rs being in phase with Tsurf, particularly when SWC &gt; 0.08 m3 m−3 (ratio of SWC to soil porosity = 0.26). However, as SWC decreased below 0.08 m3 m−3, diel variations in Rs were more closely related to variations in photosynthesis, leading to pronounced hysteresis between Rs and Tsurf. Incorporating photosynthesis into a Q10-function eliminated 84.2 % of the observed hysteresis, increasing the overall descriptive capability of the function. Our findings highlight a high degree of control by photosynthesis and SWC in regulating seasonal variation in diel hysteresis between Rs and temperature.

Spatial and temporal variations in soil respiration among different land cover types under wet and dry years in an urban park

Soil respiration (Rs) determines land surface carbon balance; however, there have been few studies that measured Rs in heterogeneous urban landscapes. Here, we investigated the spatial and temporal variations in Rs in six land cover types (mixed forest, deciduous broadleaf forest, evergreen needleleaf forest, lawn, wetland, and bare land) in Seoul Forest Park, Republic of Korea, between March 2013 and September 2014, which included a wet (2013) and an extremely dry (2014) summer. Spatially, there was a three-fold difference (0.48–1.45kgCm−2) in annual Rs among the six land cover types. The soil organic carbon stock at a depth of 0.1m explained 72% of the spatial variation in the annual Rs across the land cover types. During the entire study period, the soil temperature explained 82–97% of the temporal variation in Rs among different land cover types. Comparing the two summers, the 2014 drought only resulted in a decrease in Rs in the lawn plots (25%), which was driven by a reduction in the leaf area index and the fine root density. The temperature sensitivity of Rs in 2014 (dry summer) compared to 2013 (wet summer) was significantly lower in mixed forest, deciduous broadleaf forest, and lawn, and did not change in evergreen needleleaf forest, wetland, or bare land. The differences in Rs in these drought responses highlight the importance of the careful selection of land cover type during park planning to better manage carbon cycles.