Plant functional types and temperature control carbon input via roots in peatland soils
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Keywords:
Soil respiration
Soil carbon
Graminoid
Global carbon cycle is being profoundly altered by climate change. As an important component of the global carbon cycle, soil respiration is tightly linked to the carbon transfer among plants-soil-microbes. Soil respiration can be divided into the heterotrophic respiration and root-derived respiration (i.e., actual root respiration and rhizomicrobial respiration). Responses of soil respiration to climate warming may be different, since its components differ in occurrence sites and sources of soil organic carbon. However, the current literatures can not fully clarify the precise partition and quantification of soil respiration components. The influences of climate warming on soil respiration and related mechanisms are still unclear, which greatly limits our understanding of the accurate assessments of soil carbon cycle as well as the changes in the carbon balance of terrestrial ecosystems under climate change. We systematically summarized the progress of partitioning techniques of soil respiration components, and compared the results of partitioning of soil respiration components using different techniques. We further discussed the progress on the responses of soil respiration components to climate warming. To exactly distinguish and quantify soil respiration components, we proposed that the present techniques should be modified. Furthermore, future studies should focus on how to accurately partitioning root-derived respiration in the field for comprehensively understand soil carbon cycle and the changes of carbon budget in terrestrial ecosystems under global change. Moreover, more attention should be paid on the responses of soil respiration components to various environmental factors.气候变暖正在深刻地改变全球碳循环过程.土壤呼吸作为全球碳循环的重要环节,连接着植物-土壤-微生物之间的碳转移过程.土壤呼吸可分为异养呼吸和根源呼吸(根系呼吸和根际微生物呼吸)等组分.土壤呼吸各组分的发生部位与利用的有机碳源不同,其对气候变暖的响应可能存在显著差异.然而,目前的研究还不能完全实现土壤呼吸各组分的精确区分和量化,气候变暖对土壤呼吸各组分的影响及其具体机制仍存在很多悬而未决的问题,这极大地限制了人们对土壤碳循环评估的精确性以及对气候变暖背景下陆地生态系统碳收支格局变化的认识.本文系统综述了目前国内外土壤呼吸组分区分技术,分析了土壤呼吸组分区分的研究结果,并论述了土壤呼吸各组分对气候变暖的响应研究进展.提出仍需发展新的土壤呼吸组分区分技术或者改进和创新现有技术,未来的研究重点应放在精确区分野外条件下根源呼吸组分,同时开展土壤呼吸组分对多种环境因子变化的响应研究,以期更全面地认识土壤碳循环过程以及全球变化背景下陆地生态系统碳收支的变化趋势.
Soil respiration
Soil carbon
Terrestrial ecosystem
Carbon respiration
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Abstract. In the mesic grasslands of the central United States, the shrub Cornus drummondii has undergone widespread expansion in the absence of recurrent fire. We quantified alterations in light, water and N caused by C. drummondii expansion in tall‐grass prairie and assessed the hypothesis that these alterations are consistent with models of resource enrichment by woody plants. Responses in graminoid species, particularly the dominant C 4 grass Andropogon gerardii , were concurrently evaluated. We also removed established shrub islands to quantify their legacy effect on resource availability and assess the capability of this grassland to recover in sites formerly dominated by woody plants. The primary effect of shrub expansion on resource availability was an 87% reduction in light available to the herbaceous understorey. This reduced C uptake and N use efficiency in A. gerardii and lowered graminoid cover and ANPP at the grass‐shrub ecotone relative to undisturbed grassland. Shrub removal created a pulse in light and N availability, eliciting high C gain in A. gerardii in the first year after removal. By year two, light and N availability within shrub removal areas returned to levels typical of grassland, as had graminoid cover and ANPP were similar to those in open grassland. Recovery within central areas of shrub removal sites lagged behind that at the former grass‐shrub ecotone. These results indicate that the apparent alternative stable state of C. drummondii dominance in tall‐grass prairie is biotically maintained and driven by reductions in light, rather than resource enrichment. Within areas of shrub removal, the legacy effect of C. drummondii dominance is manifest primarily through the loss of rhizomes of the dominant grasses, rather than any long‐term changes in resource availability. C. drummondii removal facilitates grassland recovery, but the effort required to initiate this transition is a significant cost of woody plant expansion in mesic grasslands. Prevention of woody plant expansion in remnant tall‐grass prairies is, therefore, a preferred management option.
Graminoid
Andropogon
Ecotone
Tussock
Understory
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Soil carbon dioxide (CO2) evolution is a combined product of the metabolic activity of plant roots and both free-living and symbiotic heterotrophs. Soil CO2 efflux (Sf) rates are the second largest carbon flux in the global carbon cycle and the largest terrestrial contributor of CO2 (Raich and Schlesinger 1992). The components of Sf can be broken down into heterotrophic respiration (RH) and autotropic root respiration (RR). Quantifying Sf and understanding the contribution of RH and RR on intensively managed sites is fundamental to understanding the carbon cycle and implications for carbon sequestration (McElligott and others 2016).
Soil respiration
Soil carbon
Carbon respiration
Carbon fibers
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Graminoid
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As major contributor to the blue carbon sink, intertidal zones play a crucial role in the global carbon cycle. In recent years, more attention has been given to the carbon cycle in intertidal wetlands. However, due to highly variable and uncertain environmental conditions, it is difficult to clarify the quantitative relationship between soil respiration and environmental factors through in-situ experiments. In this study, the response of soil respiration characteristics to variations in the temperature and water table was investigated using a monitoring apparatus of CO2 flux at the soil–air interface in the intertidal zone. The results showed that soil respiration flux was significantly correlated with temperature, and the correlation best fitted the DoseResp function. Meanwhile, the respiration flux was enhanced with the descent of water table, a relationship could be described by a quadratic function. The effect of the water table on soil respiration became more pronounced with the rise of temperature. These results provide significant clarification of the impact of human activities on the carbon cycle in bare intertidal zones and as well as support for numerical simulations of the carbon cycle in bare intertidal zones.
Soil respiration
Soil carbon
Sink (geography)
Carbon sink
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Soil carbon plays an important role in global carbon cycle.Soil respiration is hot topic in the area of carbon cycle research.It has become the largest source that terrestrial ecosystems releases CO2 to atmosphere,and is also an index for many functional processes of ecosystems.Based on the research on soil respiration of other scholars,factors having an effect on soil respiration are temperature,humidity,the types of community,physical and chemical property of soil,etc,respectively.Some methods of measuring soil respiration and its characteristic were introduced.Finally,the paper made a summary of achievements on soil respiration in the world and suggested emphases of further study in this field.
Soil respiration
Terrestrial ecosystem
Soil carbon
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Abstract Questions Do shrubs regulate herbaceous plant community by modifying seed and plant distributions at the individual shrub scale? Do the magnitude and extent of effects at this scale change with shrub cover? Location A desert steppe, Mandalgobi, Mongolia. Methods We compared soil properties, seed accumulation and the establishment of plants of three functional types (annual forb, perennial forb and perennial graminoid) between shrub microsites (on mounds vs mound interspace) at sites differing in shrub coverage (high and low). Results Shrub patches (a legume Caragana microphylla ) promoted seed accumulation but inhibited plant establishment on mounds, relative to the mound interspace, for all functional types. However, the effects varied with shrub cover, particularly in the mound interspace, with responses specific to each functional type. The accumulation of soil and annual forb seeds increased with shrub cover at both microsites. Additionally, the density of annual forbs was positively related to shrub cover in the mound interspace. In contrast, the density of perennial forbs and graminoids decreased with increasing shrub cover at both microsites, possibly because of enhanced sand accumulation. Conclusion Shrubs shape herbaceous plant community by causing differences at the individual shrub scale in seed and plant distributions. Additionally, we showed that individual shrub effects are shrub cover‐dependent: dense shrub stands enhanced the dominance of annual forbs in spite of the negative effect found at the individual shrub scale, whereas perennial forbs and graminoids were less abundant in denser shrub stands. Shrubs can play an important role in structuring plant communities via shrub cover‐dependent variation at microsites.
Graminoid
Herbaceous plant
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Soil respiration
Soil carbon
Carbon fibers
Ecosystem respiration
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Peatlands, which contain large amounts of decaying plant matter, hold significant stores of carbon and can release that carbon into the atmosphere, affecting the global carbon cycle. Although previous studies have investigated the dynamics of peatlands within a particular region, few studies have looked at peatland dynamics globally over a long time period, and estimates of the amount of carbon stored in peatlands vary.
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We measured the proliferation of roots into experimental nutrient patches in a grassland community, distinguishing roots of graminoids and forbs. Biomass, length, and specific length were estimated for roots of each of the two functional groups, collected from patches differing in nutrient concentration, and established at four different times during a season. The ratio of graminoid and forb roots was compared with the graminoid-forb ratio in the above-ground biomass. Plant roots proliferated more intensively into patches with higher nutrient concentration, but the roots of the two functional groups had a similar ability to target richer patches. Relative proportion of graminoids was higher below-ground than above-ground and changed during the season, being lowest after mowing. Specific root length was higher for graminoid species, but did not respond to nutrient concentration in patches for either functional group. This is the first study to provide comparative information about root morphological response for graminoids and forbs, measured in a real, semi-natural plant community. The study shows no significant overall difference in the ability of these two functional types to place roots into nutrient-rich patches, but indicates other important differences among the two functional groups.
Graminoid
Growing season
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