Contribution Of Root Respiration Research Articles

Timeseries partitioning of ecosystem respiration components in seasonal, non-tropical forests; comparing literature derived coefficients with evaluation at two contrasting UK forest sites

IntroductionUnderstanding carbon flows within ecosystems is key to quantifying the impacts of land-use change in the climate. However, while the net exchange of CO2 between the ecosystem and atmosphere indicates global warming potentials, partitioning into individual flux components is needed to understand sinks and sources, residence times, and sensitivities to land-use impacts. Scaling from research site to region requires modelling evaluated against in situ measurements, but there is often a mismatch between outputs of process models (e.g., soil heterotrophic respiration (Rh)) and site-measured parameters (e.g., total soil surface respiration (Rs) or whole ecosystem respiration (Re)).MethodsThis study took a literature review approach to determine fractional coefficients for estimating Rh from Re or Rs and considered whether these fractions differed across a year in seasonal forests, where relative contributions of root respiration might be expected to vary between growing and dormant seasons. Compiled timeseries data were grouped by forest type (broadleaf, needleleaf, and mixed), and coefficients for a fraction of each component (Rs or Re) that Rh represented were calculated using two approaches, namely a simple annual mean value over all months and individual monthly means. These coefficients were then used to estimate Rh separately from higher-level fluxes (Re from eddy covariance and Rs from soil chambers), measured concurrently at two UK forest sites, and compared to Rh estimated from the same datasets using previously published generic coefficients as well as to concurrently measured Rh and Re.ResultsBoth approaches resulted in much closer convergence of the two separate estimates of Rh (derived from Re or Rs) than previously published coefficients, particularly for Rh/Re coefficients that had previously been measured under peatland blanket bog rather than forest.Discussion/ConclusionThis result suggests that land cover is an important factor in determining the relative contribution of heterotrophic respiration to higher-level fluxes and that the coefficients used would ideally be derived from studies on similar ecosystems.

Contribution of the Root Component to Soil Respiration in Oriental Beech Stands in Artvin, Turkey

Abstract Autotrophic (root) and heterotrophic respiration components respond differently to environmental variables, and each component behaves differently at different time scales, so it is necessary to partition total soil respiration into its components. The aims of this study were determine soil respiration and its root and heterotrophic components in beech stands, examine the relationship between respiration and biogeochemical factors, and assess seasonal variation in soil respiration. Trenching was applied to separate soil respiration components 6 months before measurements. Monthly soil respiration, temperature and moisture measurements, and seasonal soil and root sampling were carried out in Oriental beech (Fagus orientalis L.) stands located in Artvin Saçinka, Turkey from April 2018 to November 2018 and also (except soil sampling) from May 2019 to November 2019. The average contribution of root respiration and heterotrophic respiration to total soil respiration were 58.8% and 41.2%, respectively. Carbon and nitrogen dynamics explained variations of soil respiration with significant models. This study indicates that soil respiration and its components are associated with biogeochemical factors as well as environmental climatic conditions, and each component of respiration responds differently to changes in them.

Assessing soil carbon dioxide and methane fluxes from a Scots pine raised bog-edge-woodland

Scots pine bog edge woodland is a type of habitat typical on raised bogs where trees cohabitate with bog vegetation to form a low-density stand. Even though nowadays this habitat does not cover large areas, in a future scenario it is possible that this environment will expand, either naturally (drier climate) or anthropogenically, as the result of the application of new restoration strategies that could increase net landscape carbon benefits from both peatland and woodland environments. This study is the first reported investigation in Scotland exploring carbon flux dynamics from sparse woodlands on raised bogs. We examined how Scots pine trees directly or indirectly affected soil temperature and moisture, ground vegetation, and consequently carbon dioxide (CO2) and methane (CH4) soil fluxes. Soil CO2 and CH4 were measured at different distance from the tree and thereafter assessed for both spatial and temporal variability. Our results showed that these low-density trees were able to modify the ground vegetation composition, had no effect on soil temperature, but did affect the soil moisture, with soils close to tree roots significantly drier (0.25 ± 0.01 m3 m-3) than those on open bog (0.39 ± 0.02 m3 m-3). Soil CO2 fluxes were significantly higher in the vicinity of trees (34.13 ± 3.97 μg CO2 m−2 s−1) compared to the open bog (24.34 ± 2.86 μg CO2 m−2 s−1). On the opposite, CH4 effluxes were significantly larger in the open bog (0.07 ± 0.01 μg CH4 m−2 s−1) than close to the tree (0.01 ± 0.00 μg CH4 m−2 s−1). This suggests that Scots pine trees on bog edge woodland may affect soil C fluxes in their proximity primarily due to the contribution of root respiration, but also as a result of their effects on soil moisture, enhancing soil CO2 emissions, while reducing the CH4 fluxes. There is, however, still uncertainty about the complete greenhouse gas assessment, and further research would be needed in order to include the quantification of soil nitrous oxide (N2O) dynamics together with the analysis of complete gas exchanges at the tree-atmosphere level.

Contribution of root respiration to total soil respiration during non-growing season in mine reclaimed soil with different covering-soil thicknesses

An accurate assessment of root respiration in mine reclaimed soil is important for effectively evaluating mining area ecosystems. This study investigated dynamic changes in root respiration and the contribution of root respiration to total soil respiration (Rr/Rt ratio) during the non-growing season in mine reclaimed soil, with different covering-soil thicknesses. According to the covering-soil thicknesses, the study area was divided into four sites: 10–25 cm (site A), 25–45 cm (site B), 45–55 cm (site C), and 55–65 cm (site D). From November 2017 to April 2018 (except February in 2018), the soil respiration, root respiration, temperature at 5 cm, water content, and root biomass were measured. The results show that soil temperature and root respiration exhibited similar diurnal and monthly variations. The root respiration is strongly influenced by soil temperature during the non-growing season, with an exponential and positive relationship (P < 0.001). Root respiration varies with the covering-soil thickness and is greatest with a covering-soil thickness of 25–45 cm. The Rr/Rt ratio also exhibits monthly variations. During the non-growing season, the mean value of the Rr/Rt ratio is 51.15% in mine reclaimed soil. The study indicates that root respiration is the primary source of soil respiration and is an important factor for estimating the potential emission of soil CO2 from mine reclaimed soil at the regional scale.

Nonlinear responses of total belowground carbon flux and its components to increased nitrogen availability in temperate forests.

With the increased interest in allocating more carbon (C) belowground for C sequestration, total belowground C flux (TBCF) and its dynamics have become an important research topic. However, it remains uncertain whether TBCF responds nonlinearly to increased nitrogen (N) availability and how its main components (root and ectomycorrhizal (ECM) fungi) contribute to TBCF. We established a four-yearN addition experiment with control, low-N, medium-N, and high-N fertilization treatments in a N-limited temperate forest in northern China. We measured TBCF and its three main components including root respiration, ECM fungal respiration, and root production. The involved edaphic and plant factors were also measured. TBCF showed a nonlinear response to the increasing amounts of N addition, accelerated by 10.37% in low-N addition and restrained by 10.29% in high-N addition. Contrasting patterns of the contributions of root respiration and ECM fungal respiration to TBCF implies different strategies of investment in roots and ECM fungi under the different N-availability statuses. The ratio of production and respiration in roots under N addition was nearly 1:2, which indicated that when soil N availability increases, roots prefer to lose C by overflow respiration rather than fix C in new biomass. The low-N addition increased TBCF by directly increasing root respiration and indirectly increasing coarse root biomass. The medium-N addition positively affected TBCF by increasing root respiration but this positive effect was cancelled out by the significantly negative effect of the increased soil total N concentration. The decrease in soil pH was the most effective pathway to decrease TBCF in high-N addition. Because of a large-scale reforestation program for C sink management in recent years, our findings of the nonlinear response of TBCF to different N fertilization treatments could provide insight for predicting belowground C sequestration potential and its response to atmospheric N deposition.

Autotrophic and Heterotrophic Soil Respiration in Cryolithozone: Quantifying the Contributions and Methodological Approaches (The Case of Soils of the North of Western Siberia)

In the course of research performed in the continuous and discontinuous permafrost zone of the north of Western Siberia, the values of autotrophic (root) and heterotrophic (microbial) soil respiration and their ratio were estimated for typical ecosystems of the area. The data were obtained on the basis of a complex of field, laboratory, and calculation methods: shading, the root exclusion technique (comparison of emissions at similar sites with and without vegetation), the method of component integration or separate incubation, and the regression method. For soils of plateau palsa, the root contribution to total soil respiration was 16–30% with the use of the shading method and 14 ± 6% under the application of the component integration method. The contribution of root respiration was 60% for soils of shrub–green-moss pine forests and 30% for lichen pine forests. It may be assumed that, in forest ecosystems of the studied area, the contribution of root-derived respiration is even higher, which is related to the undercounting of respiration of tree roots and/or of rhizomicrobial microorganisms and priming effect by some methods. The contribution of root respiration in soils of mound palsa averaged 40%. For tundra with frost-boil ecosystems, the variation in the contribution of root respiration was 15–70%, depending on the location on microelements of cryogenic topography (boils and interboils). All the methods are characterized by disadvantages and some assumptions. These require additional studies to check or correct the data. The interpretation of the results is not always obvious. When using different techniques, similar results were obtained at a large number of replications of experiments during several seasons. The work also presents data on the absolute values of the specific root respiration for different species and size fractions, the value of the root biomass, and the microbial respiration of soils of different permafrost landscapes.

Contribution of Root Respiration to Soil Respiration during Rainy Season in Dry Dipterocarp Forest, Northern Thailand

Soil respiration (Rs) plays a key role in regulating the terrestrial carbon cycle. The nature of this role is determined by the different responses of root respiration (Rr) and microbial respiration (Rm) to environmental factors such as precipitation, soil moisture and temperature. Understanding these responses is fundamental to improving our predictions of climate change impacts on carbon cycling processes. In this study, the ratio of root respiration to soil respiration (Rr/Rs) was studied to improve our understanding of soil CO2emissions. The study aimed to improve our knowledge of Rr in relation to rainy season soil environmental factors in a dry dipterocarp forest in northern Thailand. With values of Rrranging from 41.04-61.97 mgCO2m-2h-1, with a Rr/Rsratio from 23-48%,the results suggest that soil moisture was a main driver for emitted CO2from Rr while soil temperature was only weakly related with Rr during the rainy season. However, longer-term studies are needed, including measurements of root biomass to improve accuracy and understanding of the dynamics of root respiration and their linkages with CO2emissions.

Contribution of root respiration to total soil respiration in a semi-arid grassland on the Loess Plateau, China

Using the trenching method, a study was conducted in a grassland on the Loess Plateau of northern China in 2008 and 2009 to partition total soil respiration (Rt) into microbial respiration (Rm) and root respiration (Rr). Using the measurements of soil CO2 diffusivity and soil CO2 production, an analytical model was applied to correct the data, aiming to quantify the method-induced error. The results showed that Rm and Rr responded differently to biotic and abiotic factors and exhibited different diurnal and seasonal variations. The diurnal variation of Rm was strongly controlled by soil temperature, while Rr might be mainly controlled by photosynthesis. The combination of soil temperature and moisture could better explain the seasonal variation in Rm (r2=0.76, P<0.001). The seasonal variation of Rr was influenced mainly by the plant activity. The contribution of root respiration to total soil respiration (Rr/Rt ratio) also exhibited substantial diurnal and seasonal variations, being higher at nighttime and lower at daytime. In the different growing stages, the Rr/Rt ratios ranged from 15.0% to 62.0% in 2008 and 14.5% to 63.6% in 2009. The mean values of the Rr/Rt ratio in the growing season and the annual mean Rr/Rt ratio were 41.7% and 41.9%, respectively, during the experiment period. Different precipitation distributions in the two years did not change the yearly Rr/Rt ratio. Corrected with the analytical model, the trenching method in small root-free plots led to an underestimation of Rr and Rr/Rt ratio by 4.2% and 1.8%.

Carbon Balance in Forest Ecosystems of Southern Part of Moscow Region under a Rising Aridity of Climate

This study estimates carbon balance in a mixed mature forest on sod-podzolic sandy-loamy soil (Albeluvisols sandy, the Prioksko-Terrasny Nature Reserve) and in a secondary deciduous forest at the Experimental Field Station of the Institute of Physicochemical and Biological Problems of Soil Sciences, Russian Academy of Sciences (gray forest loamy soil, Luvisols loamy). CO2 emissions from soils have been continuously measured every week since 1998. Net primary production was estimated in 2000–2014 by remote sensing using the normalized difference vegetation index. Long-term weather monitoring has revealed a distinctive trend toward increasing aridity of climate in the southern part of Moscow region in the observation period (1998–2014). Based on long-term ground-based and satellite monitoring data, this study shows that in the growing season, mixed and deciduous forests of the southern part of Moscow region are the sink of carbon with a mean flux of 41–112 g C m–2, depending on the contribution of root respiration. Taking into account the CO2 emissions from soils during the cold season, the forests are very likely to function as sources of atmospheric carbon at an amount of 30–100 g C m–2 yr–1, sometimes reaching very significant values of C flux (170–300 g C m–2 yr–1). In mature forest ecosystems, a significant influence on the quantitative estimate of the C balance is hampered by the CO2 emission activity from coarse woody debris, which can reach up to 14% of the total losses of C during the decomposition of soil organic matter in the mixed forest, which turns it into a persistent source of CO2 to the atmosphere. It is shown that the sink function of the forest ecosystems was more pronounced in dry years, whereas the excessive wetness diminishes their sink potential, turning the forests into sources of carbon dioxide.

Contribution of root respiration to spatial-temporal variation of soil respiration in a Haloxylon ammodendrons ecosystem in Gurbantunggut Basin

On the basis of the sparse distribution of Haloylon ammodendrons, we designed experiment to study the spatial-temporal variation of soil respiration in a Haloxylon ammodendrons ecosystem in Gurbantunggut Basin. A 401cm transect between two Haloxylon ammodendrons was built on 11 April, 2005. We started to measure soil respiration along the built transect in May, 2005. The experiment completed in September, 2007. The result of experiment showed that soil respiration under Haloxylon ammodendron crown decreased with distance from stem to the edge of crown. In the open area, shrub roots have no influence on soil respiration. Considering the results of the experiment, the contribution of root and rhizosphere respiration (Rr) to total soil respiration was determined. We deduced that Haloxylon ammodendrons root respiration averaged as 0.0768gCO2m−2h−1, account for 51.3% of total soil respiration. The seasonal pattern of soil CO2 efflux under trees, in open areas and estimated root respiration was simulated by temperature-respiration models, moisture-respiration models and bivariable models driven by soil temperature (Ts) and moisture (Ms), respectively. We inferred that bivariable models driven by soil temperature and moisture describe the seasonal variation of soil respiration better than other two kinds of models. The components of soil respiration, Rd and Rr, respond differently to environmental change. Rr is more sensitive to the dynamic of temperature. And combined model of soil temperature and moisture on respiration explain the seasonal variation of Rd. better than that of Rr.

The emission of carbon dioxide from soils of the Pasvik nature reserve in the Kola Subarctic

The emission of carbon dioxide (CO2) from podzols (Albic Podzols (Arenic)) and the factors controlling its spatiotemporal variability in the forest ecosystems of the Pasvik Reserve in the Kola Subarctic are characterized. Relatively favorable climatic conditions beyond the polar circle in summer are responsible for intensive soil respiration. The type of forest affects the emission of CO2 from the soil surface. The lowest rate of the CO2 emission is typical of the soils under lichen pine forest (105–220 mg C/(m2 h) or 180 g C/m2 during the summertime). Higher rates are observed for the soils under green moss pine (170–385 mg C/(m2 h) or 360 g C/m2 during the summertime) and birch (190–410 mg C/(m2 h) or 470 g C/m2 during the summertime) forests. This may related to a higher contribution of root respiration (44, 88, and 67%, respectively). Soil respiration and the contribution of root respiration to it increase with an increase in the canopy density; mass of small roots; microbial biomass; depth of the stony layer; soil moistening; and the contents of available carbon, nitrogen, phosphorus, and potassium compounds. At the same time, they decrease with an increase in the portion of lichens in the ground cover. The seasonal dynamics are characterized by the CO2 emission maximums in the summer and fall and minimum in the spring. The daily dynamics are smoothed under conditions of the polar day.

Response of Soil Respiration and Heterotrophic Respiration to Returning of Straw and Biochar in Rape-Maize Rotation Systems

Soil respiration has become the main way of farmland ecosystem carbon emissions. Soil respiration and its responses to soil moisture and soil temperature under straw and biochar returning were investigated. Combined soil CO2 fluxes system(ACE-002/OPZ/SC) with the method of root exclusion, this study conducted a long-term field experiment in the national monitor station of soil fertility and fertilizer efficiency of purple soils. The total soil respiration and heterotrophic respiration rate and the soil hydrothermal factors were measured during the growth period of rape and maize in rape-maize rotation systems, and the difference between total soil respiration and heterotrophic respiration was calculated as the contribution of root respiration to soil respiration. There were five treatments including CK(no organic material), CS(straw), CSD(straw+microorganism), BC(biochar), CSBC(50%straw+50%biochar), which were replicated three times. The results showed that straw and biochar returning significantly affected the seasonal variations and the peak of soil respiration. In addition to BC treatment, other treatments promoted soil respiration and cumulative emissions of soil CO2. Soil respiration rate was significantly different under different treatments, the changes in soil respiration rates showed a single peak curve under all treatments, the seasonal variations in soil respiration rates under rape was 0.12-2.29 μmol·(m2·s)-1, displaying an order of CS > CSD > CSBC > CK > BC. Soil respiration was pretty complex in maize season, the seasonal variation in soil respiration rates under rape was 1.02-15.32 μmol·(m2·s)-1, displaying an order of CSD > CS > CSBC > CK > BC, the changes in soil respiration rate presented a double peak curve under CS and CSD and CSBC treatments and a single peak curve under BC and CK treatments. Heterotrophic respiration could explain 86.50%-93.94% of seasonal variations in the soil total respiration, and the contribution of root respiration(26.49%-32.86%) was significantly lower than CK treatment(53.65%).Straw and biochar returning did not change soil temperature and soil moisture. Soil temperature at 5 cm depth had significant effects on the change dynamics of soil respiration rates, but soil moisture did not. Soil temperature at 5 cm depth could explain 82%-94% of the variations in soil respiration. The values of temperature sensitivity coefficient changed from 3.28 to 4.47. Compared with CK treatment, Q10 of CS, CSD and CSBC decreased by 26.62%, 18.12%, 20.58%, respectively, while BC increased by 12.53%. There was no synergistic effect between soil temperature and soil moisture on soil respiration, the dynamic changes of soil respiration rate could be simulated by single factor index function of soil temperature. Overall, soil respiration was significantly promoted by returning of straw, straw+microorganism, straw+biochar, while it was inhibited by returning of biochar.

Seasonal changes in the contribution of root respiration to total soil respiration in a freshwater marsh in Sanjiang Plain, Northeast China

Separating the two major components of soil respiration, root respiration (Rr) and heterotrophic respiration (Rh), is an important step for understanding and modelling carbon cycling in organic soils. However, few partitioning studies exist regarding wetland ecosystems. For this study, we selected a freshwater marsh on Sanjiang Plain, Northeast China and used a trenching method to determine the contribution of Rr to soil respiration during the two growing seasons in 2010 and 2011. The decomposition rate of dead roots (RD) was estimated to correct the soil respiration of the trenching plots. The soil respiration rates in the control plot increased from May (288–508 mg CO2 m−2 h−1) to late June (1103 mg CO2 m−2 h−1 in 2010) or early July (1278 mg CO2 m−2 h−1 in 2011) and later decreased during the last growing season. The soil respiration rate in the trenching plot exhibited a similar pattern of seasonal change, but the rates were lower than in the control plot, except at the beginning of trenching. When considering the dead root decomposition in the trenching plots, the contributions of Rr to total soil respiration in the two growing seasons were estimated to range from 22 to 77 % (2010) and 46 to 81 % (2011). The mean contribution of RD was approximately 12 % in the growing season of the first year (2010) and later decreased to approximately 6 % in the second year (2011). The contents of soil NH4+-N and NO3−-N were significantly greater in the trenching plots than in the control plots. The content of microbial biomass nitrogen tended to increase after trenching for the 0- to 30-cm soil depth. These results indicate that the microbial community may change in the second year, which may affect the estimation of the contribution of root respiration to total soil respiration.

Quantification of ecosystem C dynamics in a long-term FACE study on permanent grassland.

Because of the wide-ranging appearance and high soil organic carbon (C) content of grasslands, their ecosystems play an important role in the global C cycle. Thus, even small changes in input or output rates lead to significant changes in the soil C content, thereby affecting atmospheric [CO2 ]. Our aim was to examine if a higher C supply provided under elevated CO2 will increase the soil C pool. Special attention was given to respirational processes, where CO2 emission rates and its sources (plant vs. soil) were considered. The Giessen-FACE experiment started in 1998 with a moderate CO2 enrichment of +20% and +30% above ambient on an extensively managed grassland. The experiment consists of three control plots where no CO2 is applied, three plots where [CO2 ] is enriched by +20% and one plot receiving [CO2 ] +30%. To exclude initial CO2 step increase effects, a detailed examination of respirational processes over 30 months was carried out after 6 years of CO2 enrichment starting in June 2004. At that time, the δ(13) C signature of the enrichment-CO2 was switched from -25‰ to -48‰ without a concomitant change in CO2 concentration. After 9 years, the fraction of new C under [CO2 ] +20% was 37 ± 5.4% in the top 7.5 cm but this decreased with depth. No CO2 effect on soil carbon content was detected. Between June 2004 and December 2006, elevated [CO2 ] +20% increased the ecosystem respiration by 13%. The contribution of root respiration to soil respiration was 37 ± 13% (5 cm) and 43 ± 14% (10 cm) for [CO2 ] +20% and 35 ± 13% and 40 ± 13% for [CO2 ] +30%, respectively. Our findings of an increased C turnover without a net soil C sequestration suggest that the sink strength of grassland ecosystems might decrease in the future, because the additional C may quickly be released as CO2 to the atmosphere. Copyright © 2016 John Wiley & Sons, Ltd.

马尾松林土壤呼吸组分对不同营林措施的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 马尾松林土壤呼吸组分对不同营林措施的响应 DOI: 10.5846/stxb201503020398 作者: 作者单位: 中国林业科学研究院森林生态环境与保护研究所 国家林业局森林生态环境重点实验室,中国林业科学研究院森林生态环境与保护研究所 国家林业局森林生态环境重点实验室,中国林业科学研究院森林生态环境与保护研究所 国家林业局森林生态环境重点实验室,中国林业科学研究院森林生态环境与保护研究所 国家林业局森林生态环境重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项（CAFRIFEEP201101）；林业公益性行业科研专项（201104008） Responses of soil respiration and its components to forest management in Pinus massoniana stands Author: Affiliation: Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, State Forestry Administration Key Laboratory of Forest Ecology and Environment;National Forest Ecosystem Station of Three Gorges Reservoir in Zigui County,,Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, State Forestry Administration Key Laboratory of Forest Ecology and Environment;National Forest Ecosystem Station of Three Gorges Reservoir in Zigui County, Fund Project: 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:针对不同营林措施（对照、除灌、采伐1（15%）、采伐2（70%）后的三峡库区马尾松飞播林，采用LI-8100对其土壤呼吸组分的呼吸速率和土壤温度、湿度进行为期1年的连续观测分析表明，不同营林措施对土壤呼吸组分的影响不同。1）观测期内，各营林措施下凋落物层呼吸速率差异并不显著，对照、除灌、采伐1、采伐2的根呼吸速率均值分别为：1.00、0.83、0.86、1.11μmolCO2m-2s-1；采伐处理下矿质土壤呼吸显著高于对照和除灌（P<0.05）；2）与对照相比，营林措施并未显著改变凋落物呼吸对于土壤总呼吸的贡献率（18.78%-23.70%），但降低了根呼吸的贡献率，其中以采伐1最为显著（P<0.05）；除灌的矿质土壤呼吸贡献率（37.00%）与对照（38.32%）相近，而采伐1（45.63%）和采伐2（43.07%）均显著增加了矿质土壤呼吸的贡献率，矿质土壤呼吸的变化是造成采伐措施下土壤呼吸变化的主要土壤呼吸组分；3）营林后仅采伐2措施下土壤温湿度显著高于对照，土壤温湿度双因子模型较单因子模型能更好的解释土壤呼吸组分变化，但仅能解释其部分变化（4.6%-59.3%），仍需对营林后其他相关因子进行深入的综合研究。 Abstract:Forest soils play a critical role in the carbon cycle and carbon sequestration at both global and local scales, and forest management practices (e.g., harvesting, burning, and thinning) influence soil carbon processes by altering organic matter quality and quantity, key microclimatic conditions, microbial communities, and other factors. However, the effects of forest management on soil carbon effluxes in different ecosystems are still largely unknown, despite being critical to estimate global carbon fluxes. Quantifying the responses of soil respiration and its components to forest management is vital to accurately evaluate forest carbon balance. Thus, an aerially seeded Pinus massoniana forest was chosen in the Three Gorges reservoir area to evaluate the effects on soil respiration of different forest management practices (i.e., control; shrub-cutting:harvesting all shrubs and removing all harvest residues. Harvest strategy 1%-15% harvest intensity and removing main harvest residues without leaves and small branches; Harvest strategy 2%-70% harvest intensity and the same harvest residue management as that in harvest 1). All experimental treatments were located in similar habitats and consisted of three 20 m×20 m plots. The treatments were conducted in October 2013. A combination of trenching and litter removing methods were employed in order to partition soil respiration into components of litter layer respiration, root respiration, and mineral soil respiration. The soil temperature, soil moisture, and rate of soil respiration and its components were observed continuously for one year (from November 2013 to October 2014) using a Li-8100 system. Management did not affect litter layer respiration within the measuring period. Root respiration in the control, shrub-cutting, harvest strategy 1, and harvest strategy 2 treatments were 1.00, 0.83, 0.86, and 1.11 μmol CO2 m-2 s-1, respectively. The mineral soil respiration of harvested stands was significantly higher than that of control and shrub-cutting stands (P < 0.05). The proportion of litter layer respiration to total respiration was not significantly influenced by forest management (18.78%-23.70%), but the contribution of root respiration to total respiration was reduced, especially in the harvest strategy 1 treatment (P < 0.05). The contribution of mineral respiration to total respiration significantly increased in harvested stands, which was mainly attributed to the decrease in total soil respiration. Management effects on soil temperature and soil moisture were only observed in the stands of harvest strategy 2. A two-factor model that included soil temperature and moisture better explained the variations in soil respiration (4.6%-59.3%) than that by a model using temperature (4.2%-59.1%) or moisture (0.3%-23.5%) alone. Other factors that influence soil respiration and its components need to be further elucidated. 参考文献 相似文献 引证文献

Enhancing prediction accuracy of soil respiration in an apple orchard by integrating photosynthetic activity into a temperature-related model

Temperature is often used as the primary driver to model soil respiration (RS) and several models based only on temperature have been used to estimate it, with a variable degree of accuracy. An adequate availability of photosynthates translocated from the canopy also affects root respiration (RR) and therefore RS. In this work, carried out in an apple orchard for three years, we assessed the role of temperature to RS and its autotrophic (RR) and heterotrophic (RH) components. We also determined the variation over the season of RS at a reference temperature and related it to concurrent data of gross primary productivity at ecosystem level (GPP), light (PPFD), air temperature (Tair), orchard net primary productivity (NPP) and root growth rate. Several of these factors were then incorporated into a model to estimate RS. Data showed that temperature alone explained less than 50 % of RS variability at yearly scale. GPP, NPP, PPFD and Tair were correlated to RS at a reference temperature. The contribution of root respiration to RS increased with increasing photosynthetic activity, total tree and root growth, PPFD and Tair. On a diurnal scale, the time lag between the pattern of GPP and the pattern of RR was between 2.5 and 3 h during the growing season, decreasing to 1.5 after fruit harvest. Including GPP, NPP, PPFD and Tair to a temperature-based model improved its predicting power of RS. The results confirm the existence of a tight coupling between plant metabolism and root-derived soil respiration in the apple orchard.

Soil respiration and the contribution of root respiration of cotton (Gossypium hirsutum L.) in arid region

In northwest China, cotton field is the main cropping system in dry-land agriculture system, and the root respiration of cotton is an important component for the local carbon cycling. Our objectives were to characterize the temporal variation of soil respiration (Rt) and the contribution of root respiration of cotton. A field study was conducted to estimate root respiration by gap information method, and divide the components of root respiration (Rr) and heterotrophic respiration (Rh). Soil respiration was measured by using CIRAS chamber from August to October in 2012. Mean values of Rt and Rh were 2.65 ± 1.43 and 0.86 ± 0.51 µmol m−2 s−1, respectively. Rr estimated from gap information method was 1.98 ± 1.15 µmol m−2 s−1, and the contribution of root respiration (Rr %) was 71.37 ± 7.97% during the study period. Overall, Rr was the main component of soil respiration in cotton field. Soil abiotic and biotic factors played critical roles in the dynamics of soil respiration. Soil respiration increased exponentially with soil temperature, and soil temperature at 10 cm depth could explain 84.9, 70.5 and 82.0% of variations for Rt, Rh and Rr, respectively. The values of Q10 were 2.25, 1.97 and 2.36 for Rt, Rh and Rr, respectively, indicating that root respiration was more sensitive to soil temperature than heterotrophic respiration. R10 also showed a hyperbolic relationship with soil water content, which explained 50.4 and 56.4% of variations for Rt10 and Rr10, respectively. However, we found no significant correlation between soil water content and Rh10, indicating that excessive soil water mainly depresses root activity. In addition, soil respiration and CO2 concentration were significantly influenced by irrigation. After farmland irrigation, the reduction of CO2 concentration at 5 and 10 cm depths was probably due to the limitation of soil CO2 production and exchange with atmosphere.

Seasonal controls on patterns of soil respiration and temperature sensitivity in a northern mixed deciduous forest following partial-harvesting

Disturbances can alter CO2 efflux from soils (FCO2) by altering the microclimate, structure, and biogeochemical properties of forest ecosystems. Results of prior studies are unclear if and how partial harvesting of northern deciduous forests affects FCO2. These mixed responses may be due to differences in harvesting levels, time since harvest, and the spatial and seasonal heterogeneity of treatment effects and soil properties. To account for this spatio-temporal dependence, we produced subject-level regression models from regular measurements of FCO2 and soil temperatures during the 2010–2012 growing seasons following tree-length (TL) and more intensive biomass (BIO) harvests. In this paper, we compare seasonal and inter-annual post-harvest recovery trends for measured and temperature-corrected soil respiration rates and the sensitivity of soil respiration to temperature (as Q10).FCO2 values from TL/BIO treatments exceeded unharvested controls, recurrently peaking in the autumn (average for TL/BIO: 28%/17%, p⩽0.05) and waning in the summer (14%/10%, not significant). A comparison of measured FCO2 vs. modelled respiration values corrected for temperature differences indicated that higher soil temperatures following canopy thinning accounted for 34–41% of these differences in 2010 but <15% by 2012. Initially lower in 2010, Q10 and summer respiration values for harvested treatments exceeded those of controls by 2012, and despite waning temperature differences, average annual effect sizes corrected for temperature differences did not decline. Autumn and basal respiration rates were correlated with post-harvest fine woody debris volumes in 2010 (r2=0.58/0.57, p=0.01), summer rates in all years decreased with harvested tree basal area (r2=0.43–0.58, p⩽0.05), and the post-harvest basal area of understorey vegetation predicted increasing Q10 effect sizes from 2010 to 2012 (r2=0.81, p⩽0.01). With consideration to studies demonstrating that the contribution of root respiration (RR) to FCO2 is highest in summer, we propose that partial harvesting initially restricts RR and peak summer respiration rates, but compensates for this decline by increasing basal respiration rates and FCO2 through elevated soil temperatures and decomposition rates from canopy thinning and harvest residue substrate inputs (i.e., woody debris and root necromass). During post-harvest recovery, forest understorey regrowth reduces soil temperatures but influences patterns of FCO2 by increasing summer respiration and Q10 values in harvested treatments, likely by increasing RR.

Radiocarbon-Based Partitioning of Soil Respiration in an Old-Growth Coniferous Forest

Temperate forests play an important role in the global carbon cycle, and are thought to currently be a sink for atmospheric CO2. However, we lack understanding of the drivers of forest carbon accumulation and loss, hampering our ability to predict carbon cycle responses to global change. In this study, we used CO2 flux and radiocarbon (14C) measurements to investigate the role of seasonal drivers on soil respiration. Radiocarbon measurements of CO2 evolved during incubation of fine roots and root-free soils at the beginning and end of the growing season (April and August) showed that these two soil respiration sources (fine roots vis-à-vis soils) have different mean residence times that stayed constant between seasons. Radiocarbon measurements show that root respiration was made up of carbon fixed 3–5 years prior to sampling, and that heterotrophic respiration was made up of carbon fixed 7–10 years prior. The difference in radiocarbon signature between the two sources allowed us to partition autotrophic and heterotrophic respiration sources for soil respiration measurements in the field. We observed a small but significant increase in ∆14C of soil respiration between April and August, suggesting an increase in heterotrophic respiration sources over the growing season. Using a two end-member mixing model, we estimate that 55 ± 22% of soil respiration originated from autotrophic (root) sources in April, but their contribution dropped to 38 ± 21% in August. These findings suggest that the contribution of root respiration increases at a time of high productivity and/or as a result of relatively low microbial respiration in the early spring in this old-growth coniferous forest.

Global annual soil respiration in relation to climate, soil properties and vegetation characteristics: Summary of available data

Soil respiration (Rs) is a key process in the terrestrial carbon cycle. Measurement and simulation of Rs has received much attention recently. We collected annual Rs field datasets to examine key controls of temporal and spatial variability in annual Rs at the global scale. Published studies that reported annual field Rs, mean annual temperature (MAT), annual precipitation (AP), soil (0–20cm) properties and vegetation characteristics were compiled. MAT, AP and soil organic carbon (SOC) were the three most important variables in these datasets, together being responsible for 50% of the variance in annual Rs in a global model (MAT&AP&SOC-model). Combining other site soil properties (e.g. pH) and vegetation variables, such as tree age (TA), tree height (TH), litter fall biomass (LF) and leaf area index (LAI), into the MAT&AP&SOC-model improved model performance. The site characteristic that explained the most variation in Rs was AP followed by MAT, SOC, net primary productivity (NPP), pH, TA, TH, LF, LAI, elevation (EL) and diameter at breast height (DBH). Among the simulated models, the model based on MAT, AP, SOC and pH had the best fit for annual Rs variance. There was a highly significant logarithmic relationship between Rr/Rs (the contribution of root respiration to Rs) and AP. The AP value of 0.4m was a threshold for Rr/Rs, corresponding to Rr/Rs of 0.4 which reflects water limitation of root growth and plant productivity.