Effects of temperature and moisture manipulation on biological activity of Northern and Southern taiga peat soils 

<p>Peatlands comprise 19% of the permafrost area in the subarctic zone, they store 277 Pg of organic carbon. Peatlands in that area are represented by palsa mire. The palsa mire consists of frozen peat mounds (palsa), thermokarst depression and the wet bog without permafrost.</p><p>Climate change and thawing of permafrost leads to a change in soil moisture, both drying and wetting. This can lead to a change in the carbon balance of the ecosystem and increase or decrease the emission of greenhouse gases (CO<sub>2</sub> and CH<sub>4</sub>).</p><p>The aim of the work was to study the effect of changes in soil moisture on the biological activity of palsa mire peat soils in the north of Western Siberia (65°18'52"N, 72°52'32"E). The studies were conducted in 2018-2021 in the northern taiga in the discontinuous permafrost zone.</p><p>The two palsas (Cryic Histosol) and the surrounding bog (Fibric Histosol) were examined. Palsa soils were characterized by high variability of the studied parameters; active layer thickness was 0.66±0.07 m, soil moisture - 30.98±2.49%, soil temperature - 8.31±0.45°C. The soils of the bog were characterized by the absence of permafrost, a higher soil temperature - 13.58±0.26°C and soil moisture - 74.59±0.26%. Despite the difference in the studied parameters of these ecosystems, no significant differences in biological activity were found (185.97±30.51 mgCO<sub>2</sub>/m<sup>2</sup>/h).</p><p>Based on field measurements, 3 plots were identified with the same type of vegetation and soil temperature, but significantly differ in soil moisture. Depending on soil moisture, the plots were named “Dry” (25.73±1.89%), “Wet” (38.44±0.70%) and “Moist” (53.09±1.06%). Biological activity did not vary significantly between the studied sites but had a multidirectional dynamic in different years. This shows the complexity of palsa, their multifactorial nature and an ambiguous response to changes in moisture.</p><p>An added experiment was set up to change soil moisture - transplantation. Measured of CO<sub>2</sub> emissions from undisturbed peat soil of a large volume transferred from dry palsa to a wetting bog. And vice versa. The biological activity of the soils did not differ considerable both during wetting and draining. In different years, there was a vary dynamics in CO<sub>2</sub> emissions.</p><p>According to the results of the study, with climate change, thawing of permafrost and palsa degradation, there will be no significant CO<sub>2 </sub>flux. This may be due to the multifactorial nature of ecosystems, a wide optimum of soil moisture for peat soils. The influence of additional factors is also significant: the size of the methanotrophic barrier, the transport of CO<sub>2</sub> with solutions over the surface of the palsa permafrost.</p>

Understanding the moisture and temperature sensitivity of soil respiration is important as climate change brings more variation in soil moisture (e.g., drought, drying, and rewetting events) and soil temperature (e.g., warming). However, soil moisture and soil temperature sensitivity of soil respiration are often assumed fixed, neglecting environmental controls that might modulate them. Moreover, the soil moisture sensitivity is likely different during drying as opposed to rewetting periods due to the different processes involved, and soil temperature sensitivity is often estimated without separating the drying and rewetting periods, during which processes with contrasting temperature sensitivity are dominant. Here, we collected high-frequency field data on soil respiration, soil moisture, and soil temperature from COSORE (27 sites) and NEON (47 sites) and defined the moisture and temperature sensitivity of soil respiration in both the drying and rewetting periods. Using the monthly standardized precipitation evapotranspiration index (SPEI) and monthly temperature over the last 30 years of each site, we characterized the historical climate conditions by drought frequency and temperature amplitude. Then, the moisture and temperature sensitivity of soil respiration in both the drying and rewetting periods were explained by historical climate conditions, vegetation index, soil properties, and their interactions. The results will provide a better understanding of the environmental controls on soil moisture and temperature sensitivity of soil respiration.

PDF HTML阅读 XML下载 导出引用 引用提醒 天山北坡积雪消融对不同冻融阶段土壤温湿度的影响 DOI: 10.5846/stxb201901040044 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 自治区重点实验室课题(2018D04024);国家自然科学基金项目(U1603342,41961002) The influence of snowmelt on soil temperature and moisture in different freezing-thawing stages on the north slope of Tianshan mountain Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research 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:积雪作为一种特殊的覆被,直接影响着土壤温度、土壤水分分布及其冻结深度、冻结速率等,影响当地的生态水文过程。利用2017年11月1日至2018年3月31日天山北坡伊犁阿热都拜流域的土壤含水率资料,划分土壤不同冻融阶段,结合积雪不同阶段,进而分析积雪消融对季节性冻土温湿度的影响。结果表明:在整个土壤冻融期间,土壤温湿度的变化取决于积雪深度、大气温度和雪面温度的高低,且与其稳定性有关。土壤冻结阶段,土壤温湿度持续下降,表层土壤温湿度受气温影响较大,且波动明显,而深层土壤的温湿度变化平缓;土壤完全冻结时,有稳定积雪覆盖,由于积雪的高反射性、低导热性,影响着地气之间的热量传递,因此土壤的温湿度变化较为平稳,积雪有一定的保温作用;冻土消融阶段,气温回升,积雪消融,地表出露,各层土壤温度随气温变化而变化,且越靠近地表,土壤温度越高,变幅越大,与冻结期完全相反。由于融雪水的下渗,土壤湿度快速增加。进一步分析积雪与土壤温湿度的相关性得出,积雪对土壤温湿度的影响分不同时期,对土壤温度的影响主要在积雪覆盖时,对土壤湿度的影响主要是在积雪消融时期,这对于研究该地生态水文循环及后续融雪性洪水的模拟与预报具有一定的参考价值。 Abstract:As a special cover, snow cover directly affects soil temperature, soil moisture distribution, freezing depth and freezing rate, and affects the local eco-hydrological processes. The existence of snow can affect the frozen soil, the interaction of surface-atmosphere, and change the energy exchange and temperature transfer between the soil and the atmosphere. The freezing-thawing process of soil has an important impact on soil water content. It is of great significance for the effective utilization of frozen soil resources, the guidance of irrigation water, the study of soil evaporation, groundwater recharge and local eco-hydrological cycle. In this paper, meteorological data, soil temperature and moisture data and snow cover data were used to analyze the characteristics of seasonal frozen soil temperature and moisture changes in the study area. Based on the data of soil water content from November 1, 2017 to March 31, 2018 in the Alatobe Basin, Ili, on the northern slope of Tianshan Mountains, the different freezing-thawing stages of soil were divided, and the effects of snow melting on the temperature and moisture of seasonal frozen soil were analyzed. The results show that snow melting has a great influence on the temperature and moisture of seasonal frozen soil. The soil was frozen beginning in November in Alatobe Basin, and the soil freezing time lagged with the increase of soil depth. The soil freezing process is one-way, starting from the surface, while the melting process is two-way, starting from both the surface and the bottom. During the whole freezing-thawing period, the change of soil temperature and moisture depends on the depth of snow cover, atmospheric temperature and snow surface temperature. And it mainly affects the surface soil temperature. The deeper the soil depth is, the more slightly the change of soil temperature and moisture is. During the soil freezing stage, the soil temperature and moisture continued to decline, the surface soil temperature and moisture were greatly affected by temperature, and the fluctuation was obvious, while the deep soil temperature and moisture changed slightly. When the soil was completely frozen, there was stable snow cover. Because the high reflectivity and low thermal conductivity of snow affected the heat transfer of surface-atmosphere, the change of soil temperature and moisture was relatively stable, and the snow cover had a certain degree. During the thawing stage, the temperature rises, the snow melts and the surface exposes. The soil temperature varies with the change of temperature. The closer to the surface, the higher the soil temperature, the larger the change range, which is completely contrary to the freezing period. Soil moisture increases rapidly due to the infiltration of snowmelt water. Further analysis of the correlation between snow cover and soil temperature and moisture shows that the influence of snow cover on soil temperature and moisture can be divided into different periods. The influence on soil temperature is mainly in snow cover, and the influence on soil moisture is mainly in snow melting period, which has a certain reference value for the study of the eco-hydrology cycle and the simulation and prediction of subsequent snowmelt flood in this area. 参考文献 相似文献 引证文献

In the course of studies in typical forest ecosystems of the northern, middle, and southern taiga of Western Siberia performed at the peak of the growing season, the spatial variation of soil CO2 emissions and their relationships with the content of extractable and microbial soil carbon and soil hydrothermic parameters were estimated. The studied parameters of the soil carbon cycle are characterized by the high spatial variability in all the studied ecosystems. This fact indicates the need for a detailed investigation of the greenhouse gas soil emission in all ecosystems typical of a given natural zone. There is a statistically significant difference between the soils of the green-moss pine forests and the soils of the lichen pine forest of the northern taiga. In the green-moss pine forest, the carbon content of microbial biomass is 1.5 times higher (195 ± 24 and 127 ± 16 mg C/kg soil, respectively), the content of extractable carbon is 4 times higher (157 ± 25 and 41 ± 5 mg C/kg of soil, respectively), and the CO2 emission is 1.7 times higher (324 ± 20 and 190 ± 10 mg CO2/(m2 h), respectively) than those in the lichen pine forest. In the northern taiga zone, carbon dioxide emissions from soils in the green-moss pine forests are largely determined by the soil temperature; the role of soil moisture is less significant. In the soils of lichen pine forests, the CO2 emission is mainly controlled by the content of extractable carbon. Significant factors influencing the soil СО2 emission in forest ecosystems of the taiga zone are the content of extractable and microbial carbon and hydrothermic parameters of the soils.

The assessment of the carbon pool in representative forest stands of the northern, middle, and southern taiga subzones of Central Siberia, located in the territory of the Krasnoyarsk Kraihas, has been conducted. The area of these taiga regions accounts for 87.5% of the total territory of Central Siberia, and they make the main contribution to carbon deposition in this area. The total mass of deposited carbon in the representative stands of the northern taiga is 73970 thousand tons, in the stands of the middle taiga this value is 1257101 thousand tons, and for the southern taiga, it is 2766554 thousand tons. The average mass of deposited carbon for the northern taiga subzone is 13.2 tons per hectare, for the middle taiga it is 44.6 tons per hectare, and for the southern taiga, it is 64.5 tons per hectare. Such differences are due to the zonal characteristics of the natural and climatic conditions in these areas and, consequently, the varying productivity of the forest stands formed in these taiga subzones. The fractional composition of the carbon pool depends on many indicators, primarily on the bonitet (site quality), density, and fullness of the forest stand. For all the considered representative forest stands, the main contribution to carbon deposition comes from the trunks and roots of trees. In the northern taiga, the share of trunks accounts for 49.9% to 66.7% of the deposited carbon, while roots account for 18.1% to 34.8%. For the middle taiga, these values range from 53.8% to 70.4% for trunks and from 13.2% to 33.4% for roots. For the southern taiga, the share of deposited carbon in trunks is from 53.4% to 69.6%, and in roots, it is from 17.7% to 31.9%. The obtained data on the carbon pool of forest stands in the taiga zone of Central Siberia are important for understanding carbon exchange processes in forest ecosystems, as well as for developing effective strategies for the conservation and management of forest areas in the context of climate change.

Grasshopper eggs overwinter in soil for almost half a year. Changes in soil temperature and moisture have a substantial effect on grasshopper eggs, especially temperature and moisture extremes. However, the combinatorial effect of temperature and moisture on the development and survival of grasshopper eggs has not been well studied. Here, we examined the effects of different soil moistures (2, 5, 8, 11, 14% water content) at 26°C and combinations of extreme soil moisture and soil temperature on the egg development and survival of three dominant species of grasshopper (Dasyhippus barbipes, Oedaleus asiaticus, and Chorthippus fallax) in Inner Mongolian grasslands. Our data indicated that the egg water content of the three grasshopper species was positively correlated with soil moisture but negatively correlated with hatching time. The relationship between hatching rate and soil moisture was unimodal. Averaged across 2 and 11% soil moisture, a soil temperature of 35oCsignificantly advanced the egg hatching time of D. barbipes, O. asiaticus, and C. fallax by 5.63, 4.75, and 2.63 days and reduced the egg hatching rate of D. barbipes by 18%. Averaged across 26 and 35°C, 2% soil moisture significantly delayed the egg hatching time of D. barbipes, O. asiaticus, and C. fallax by 0.69, 11.01, and 0.31 days, respectively, and decreased the egg hatching rate of D. barbipes by 10%. The hatching time was prolonged as drought exposure duration increased, and the egg hatching rate was negatively correlated with drought exposure duration, except for O. asiaticus. Overall, the combination of high soil temperature and low soil moisture had a significantly negative effect on egg development, survival, and egg hatching. Generally, the response of grasshopper eggs to soil temperature and moisture provides important information on the population dynamics of grasshoppers and their ability to respond to future climate change.

Effects of moisture and temperature on net soil nitrogen mineralization: A laboratory study

The eastern hemlock (Tsuga canadensis) is an important foundation species that is currently declining throughout eastern U.S. forests due to the exotic pests hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa). Hemlock is often replaced by deciduous tree species, such as black birch (Betula lenta), and has been shown to have large consequences for carbon dynamics due to a substantial loss of soil organic layer carbon storage in hemlock forests when replaced by birch and higher decomposition found in black birch stands. Soil carbon is one of the most important components of the global carbon cycle and has high potential to feedback to climate change when large portions of stored carbon are lost to the atmosphere. There is a general consensus that soil respiration increases with temperature, but there has yet to be a consensus on how temperature sensitivity of soil respiration is affected by various biotic and abiotic factors, such as soil moisture and substrate quality. In this study, the effects of soil temperature and soil moisture on soil respiration (Rs), the temperature sensitivity of soil respiration (Q10), and soil basal respiration (R10) were investigated for hemlock, young birch, and mature birch forest types annually for three years. The Rs values of the three forest types were primarily driven by soil temperature rather than by soil moisture across all years. Soil respiration data collected from hemlock, young birch, and mature birch stands were used to determine annual Q10 and R10 values. The Q10 and R10 values were not significantly different between forest stands, but they were significantly different over the three years. Determinants of Q10 and R10 differed between forest type, with soil moisture primarily influencing Q10 in hemlock and mature birch stands and soil temperature primarily influencing R10 in mature birch stands. The results suggest a complex interaction of soil moisture and soil temperature, and potentially substrate quality and quantity, as determinants of temperature sensitivities in eastern U.S. forests that have transitioned from hemlock-dominated to black birch-dominated forests.

The temperature sensitivity (Q10) of soil respiration (Rs) plays a crucial role in evaluating the carbon budget of terrestrial ecosystems under global warming. However, the variability in Q10 along soil moisture gradients remains a subject of debate, and the associated underlying causes are poorly understood. This study aims to investigate the characteristics of Q10 changes along soil moisture gradients throughout the whole growing season and to assess the factors influencing Q10 variability. Changes in soil respiration (measured by the dynamic chamber method) and soil properties were analyzed in a poplar plantation located in the suburban area of Beijing, China. The results were as follows: (1) Q10 increased with the increasing soil water content up to a certain threshold, and then decreased, (2) the threshold was 75% to 80% of the field capacity (i.e., the moisture content at capillary rupture) rather than the field water-holding capacity, and (3) the dominant influence shifted from soil solid-phase properties to microbes with increasing soil moisture. Our results are important for understanding the relationship between the temperature sensitivity of soil respiration and soil moisture in sandy soil, and for the refinement of the modeling of carbon cycling in terrestrial ecosystems.

The temperature, moisture, and salt content of soil in alpine regions are sensitive to changes in climatic factors and are important indicators of ecosystem functions. In this study, we collected soil moisture, temperature and electrical conductivity data at different depths at a sampling site on Bird Island in Qinghai Lake during winter using a continuous soil temperature, moisture and salt content monitoring system and analyzed their variations and influential factors. The variation in soil moisture showed an obvious ‘V-shaped’ pattern from 00:00 to 23:00 and an upward trend with soil layer depth. From 00:00 to 23:00, the overall soil temperature data fitted a ‘unimodal’ curve and showed a clear and continuous upward trend with soil layer depth at a rate of 0.684 (p < 0.001). Soil electrical conductivity data also exhibited a distinct ‘V-shaped’ pattern from 00:00 to 23:00 and a continuous increase with increasing soil depth. The correlation between soil temperature, moisture, and conductivity and the spatial distribution of five climate factors indicated that climate factors accounted for 53.6% of the changes in soil temperature, moisture, and salinity. Climate factors showed a significant positive correlation with soil temperature, moisture, and conductivity (p < 0.001), and air temperature was the most important factor influencing soil temperature and soil moisture changes, whereas wind direction was the most important factor influencing soil conductivity. (Wind direction and wind speed affect soil evapotranspiration, and then affect soil moisture and solute transport process). The results of this preliminary study reveal the characteristics associated with soil temperature, moisture, and salinity changes in winter within the wetlands of Bird Island on Qinghai Lake in the context of climate change, and they can be used as valuable reference data in further studies investigating associated changes in ecosystem functions.

Carbon dioxide exchange and temperature sensitivity of soil respiration along an elevation gradient in an arctic tundra ecosystem

Quantifying the temporal and spatial patterns of temperature sensitivity (Q10) of soil respiration (Rs) as well as its controlling factors is critical to reveal the response the soil ecological processes to global warming and improve carbon budget estimations at a regional scale. The seasonal and annual variations in the temperature response of Rs were assessed during the two growing seasons in 2011 and 2012 in four different vegetation sites in a meadow steppe of the Songnen Plain, China. The Q10 values across all sites exhibited significant seasonal variations with a minimum value (1.81–2.34) occurring during summer and a peak value (3.82–4.54) occurring in either spring or autumn. The mean seasonal Q10 values showed no significant differences among the four different vegetation types. On the annual scale, however, the Chloris virgata site had significantly higher annual Q10 values (3.67–4.22) than the other three community sites in 2011 and 2012 and over the two years (2.01–3.67), indicating that the response of the Rs to climate warming may vary with vegetation type. The soil temperature and moisture had interactive effects on the variations of Q10 values. Soil temperature was the dominant factor influencing Q10 values, while soil moisture was an additional contributor to the variations of Q10. Due to the significant temporal and spatial variations in soil respiration response to temperature, acclimation of Rs to temperature variation should be taken into account in forecasting future terrestrial carbon cycle and its feedback to global warming.

Forest fires alter the trophic structure of soil nematode communities

Relatively little work has been published about soils in northwestern Russia, and soil-parent material-vegetation relationships are not well established for this region. Seven pedons developed on late-Pleistocence glacial deposits in the northern, middle, and southern taiga zones of northwestern Russia were described and classified according to the official classification systems of both the United States and Russia. Morphological descriptions and laboratory data that included pH, particle size distribution, selective dissolution analysis, and carbonate equivalent were used for classification. Psamments (Podzols) with Bs and Bhs horizons are most common in the northern taiga, where parent materials are dominated by felsic till and glacial outwash, and vegetation is mostly evergreen conifers. Parent material heterogeneity in the middle taiga promotes soil diversity. Soils on thin calcareous till over limestone are Rendolls (Soddy-calcareous soil); soils on thick calcareous till are Cryalfs (Podzolic soil), and those on slightly calcareous glacial-lacustrine deposits are Psamments (Podzol), with much weaker spodic character than the soils of the northern taiga. Vegetation in the middle taiga varies from broadleaf, deciduous trees on highly calcareous soils, to evergreen conifers on the weakly calcareous soils. The southern taiga region soil formed on calcareous two-layer till is a Cryept (Soddy-podzolic soil) under evergreen conifer forest. Soil properties are clearly linked to the composition of the glacial deposits and to the forest vegetation. We also show that strongly podzolized soils, as indicated by albic horizons and significant subsoil accumulations of carbon and oxalate-extractable Al and Fe, nonetheless fail U.S. taxonomic criteria for spodic material and Spodosols, primarily on the basis of soil color.

Wetlands are an important component of the terrestrial ecosystem, and play a crucial role in sequestering carbon. However, to date, there is little information about the land-use and nitrogen-fertilization effects on temperature sensitivity of soil respiration in wetland. In this investigation, effects of land use and nitrogen fertilization on temperature sensitivity of soil respiration (Q 10) in a freshwater marsh of northeast China were studied. The results showed that change of land use significantly affected Q 10-value, which followed the order: Intact Deyeuxia angustifolia wetland soil >upland forest soil >abandoned cultivated soil >cultivated soil. Our data confirmed that soil temperature and moisture were important factors affecting Q 10-values. Besides temperature and soil moisture, availability of C and N and microbial activity in soil were important factors affecting Q 10-values. Nitrogen fertilization resulted in an increase in Q 10-value not only in the intact wetland, but also in the cultivated soil. Although availability of N could stimulate temperature sensitivity of soil respiration, high nitrogen fertilization (i.e., 240 kg N ha−1 in this study) inhibited temperature sensitivity. Further studies are indicated as a means of answering these questions and providing additional information on the effects of nitrogen fertilization on Q 10-value.