The Chronological Advancement of Soil Organic Carbon Sequestration Research: A Review

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<ul><li><p>REVIEW</p><p>The Chronological Advancement of Soil Organic CarbonSequestration Research: A Review</p><p>J. Dinakaran Mohammad Hanief </p><p>Archana Meena K. S. Rao</p><p>Received: 5 May 2013 / Revised: 10 December 2013 / Accepted: 29 January 2014</p><p> The National Academy of Sciences, India 2014</p><p>Abstract According to Kyoto protocol carbon seques-</p><p>tration in terrestrial ecosystem is a low cost option to</p><p>mitigate the increasing atmospheric CO2 concentrations. It</p><p>has been understood that the worlds forests and their soils</p><p>have a high potential to sequester the atmospheric carbon.</p><p>For the last two decades there has been increasing interest</p><p>among scientists in terrestrial soil carbon storage processes.</p><p>This review made an attempt to summarize the major</p><p>chronological advancement of soil organic carbon (SOC)</p><p>sequestration research and also to underpin the problems</p><p>yet to be focused on this research at global level. SOC</p><p>sequestration research began in the early seventies, where</p><p>most of the studies were estimating the size/stock of the</p><p>global SOC. In the early eighties, most of the researchers</p><p>have started to focus on the factors involved in the storage</p><p>of organic carbon in different ecosystems. Subsequently,</p><p>the researchers started to work on different types of SOC</p><p>pools, their size, turnover and chemical characterization in</p><p>different types of ecosystems. Recently the researchers</p><p>main focus has been the temperature sensitivity of organic</p><p>carbon in different types of soil and their mechanism of</p><p>stabilization. There has been interest among researchers on</p><p>the contribution of microbial derived (microbial necro-</p><p>mass) carbon in recalcitrant pool of SOC and their</p><p>sequestration process in different types of ecosystems.</p><p>Arguably, the contribution in SOC sequestration research</p><p>on the fate of sequestered carbon in different types of soil</p><p>and their stabilization mechanisms is insufficient. India is</p><p>the country spread over regions from temperate to dry</p><p>desert zones with different types of fragile ecosystems and</p><p>its vulnerable nature to the global climate change. There-</p><p>fore, the future research must focus on SOC sensitivity to</p><p>temperature and SOC stabilization mechanisms in different</p><p>ecosystems for better understanding of the soil carbon</p><p>cycle.</p><p>Keywords Carbon sequestration Carbon stabilization Soil organic carbon pools Labile and recalcitrant pool</p><p>Introduction</p><p>The rising level of global surface temperature is the major</p><p>concern for developed and developing countries around the</p><p>world since its impact has been felt mostly on changes in</p><p>monsoon scenario, drought, flood and sea level rise. The</p><p>amount of CO2 present in the atmosphere plays a crucial</p><p>role to maintain the global surface temperatures; and it has</p><p>historically fluctuated between about 180 ppm during gla-</p><p>cial periods and 280 ppm during interglacial periods [1, 2].</p><p>It has increased due to the burning of fossil fuels, cement</p><p>production, deforestation and agricultural development,</p><p>from the pre-industrial level of about 280 ppm to</p><p>*391 ppm now [3]. The amount of CO2 is increasing atthe rate of 0.4 % or 1.5 ppm year-1. Similarly, CH4 has</p><p>increased from 0.80 to 1.74 ppm and increasing at the rate</p><p>of 0.75 % or 0.015 ppm year-1 while N2O has increased</p><p>from 288 to 311 ppb and is increasing at the rate of 0.25 %</p><p>or 0.8 ppb year-1 [4]. Earths surface temperature has</p><p>increased by 0.74 C since year 1850 and is expected toincrease by another 1.1 to 6.4 C by the end of this century[5]. Thus understanding the terrestrial carbon cycle is very</p><p>important since the temperature affects almost all aspects</p><p>of terrestrial carbon processes, it likely enhances ecosystem</p><p>carbon flux, potentially feeding back to a buildup of</p><p>J. Dinakaran (&amp;) M. Hanief A. Meena K. S. RaoNatural Resource Management Laboratory, Department of</p><p>Botany, University of Delhi, North Campus, Delhi 110007, India</p><p>e-mail: jesudina@gmail.com</p><p>123</p><p>Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci.</p><p>DOI 10.1007/s40011-014-0320-0</p></li><li><p>atmospheric CO2 concentration and climate dynamics [6].</p><p>The need to identify options for mitigating atmospheric</p><p>concentrations of CO2 is widely recognized. The United</p><p>Nations Framework Convention on Climate Change (UN-</p><p>FCCC), adopted in 1992 in Rio de Janeiro, with the main</p><p>aim as the stabilization of greenhouse gases in the</p><p>atmosphere at a level that will prevent dangerous anthro-</p><p>pogenic interference with the climate system was the first</p><p>international treaty that set out to address the problem of</p><p>climate change by working to prevent anthropogenic</p><p>emissions that contribute to climate disturbances [7, 8].</p><p>The Kyoto Protocol, ratified by several countries but not by</p><p>the major CO2 emitters, mandates that industrialized</p><p>nations must reduce their net emissions with reference to</p><p>the 1990 level by an agreed amount and recognizes a wide</p><p>range of options to minimize the risks of global warming.</p><p>The efforts in the recent deliberations on climate change/</p><p>global warming in Copenhagen (2010) and Durban (2011)</p><p>among developed and developing countries became almost</p><p>futile to adapt the noteworthy regulations to combat cli-</p><p>mate change. India is also one of the more susceptible</p><p>nations to the influence of climate change than its devel-</p><p>oped counterparts. According to the Kyoto protocol (KP),</p><p>carbon sequestration in terrestrial sinks can be used to</p><p>offset greenhouse gas emissions [9].</p><p>Current growth rate in the economy and commitment to</p><p>environmental protection of India makes it necessary to</p><p>protect the forests and other important ecosystems. How-</p><p>ever, still, there is a lack of study on SOC sequestration in</p><p>fragile ecosystems such as forests, croplands, wetlands and</p><p>grass/pasturelands of India. An attempt has been made in</p><p>this review to summarize the major chronological</p><p>advancement of SOC sequestration research in terrestrial</p><p>ecosystems and also to underpin the problems yet to be</p><p>focused on this research at global and regional level. This</p><p>review has abridged the following major SOC research</p><p>areas viz., (i) estimation of carbon stock in different eco-</p><p>system (ii) factors affecting the SOC storage (iii) Soil</p><p>organic matter (SOM) models (iv) separation of discrete</p><p>SOC pools (v) to understand the temperature sensitivity of</p><p>SOC in different ecosystems (vi) chemical characterisation</p><p>of SOC (vii) measurement of carbon isotopes in SOC</p><p>dynamics and (viii) understanding the mechanisms/pro-</p><p>cesses involved in SOC stabilization in different</p><p>ecosystems.</p><p>Carbon Sequestration</p><p>Carbon sequestration implies capture and storage of</p><p>atmospheric CO2 into stable pools in the ocean, geologic</p><p>basalts, vegetation and soil by abiotic (engineered) and</p><p>biotic strategies</p><p>Abiotic Strategies</p><p>They involve separation, capture, compression, transport,</p><p>and injection of CO2 from industrial flue gases and efflu-</p><p>ents deep into geological basalts and the ocean [4]. Abiotic</p><p>strategies of sequestration of carbon are still in infancy, and</p><p>the implementation of abiotic strategies to sequester carbon</p><p>requires lot of money, chemicals and equipments, because</p><p>these strategies are totally based on new engineering</p><p>techniques.</p><p>Consequences of Abiotic Carbon Sequestration</p><p>The oceans are absorbing CO2 from the atmosphere and</p><p>this is causing chemical changes by making them more</p><p>acidic. In the past 200 years the oceans have absorbed</p><p>approximately half of the CO2 produced by fossil fuel</p><p>burning and cement production. The pH of the ocean sur-</p><p>face waters has already fallen by about 0.1 units from about</p><p>8.16 to 8.05 since the beginning of the industrial revolution</p><p>around 200 years ago. If global emission of CO2 from</p><p>human activities continues to rise on current trend then the</p><p>average pH of the oceans could fall by 0.5 units (equivalent</p><p>to a threefold increase in the concentration of hydrogen</p><p>ions) by the year 2100 [10]. Ocean acidification, as the</p><p>phenomenon is called, over time will create major negative</p><p>impacts on corals and other marine life, with anticipated</p><p>adverse consequences for fishing, tourism, and related</p><p>economies [10]. However, many of the ecological, chem-</p><p>ical, and geological elements of the deep sea are little</p><p>understood, and therefore, the effects of injecting carbon</p><p>dioxide into the ocean, are widely unknown. In addition, if</p><p>the CO2 leaks out of a storage formation, hazards may exist</p><p>for humans, ecosystems and groundwater.</p><p>Biotic Strategies</p><p>In contrast to oceanic and geologic carbon storage tech-</p><p>niques, the terrestrial carbon sequestration in biotic strate-</p><p>gies is based on the natural process of photosynthesis and</p><p>transfer of fixed atmospheric CO2 into vegetative biomass</p><p>and SOM pools [11, 12]. SOM is a complex mixture of</p><p>plants, animals and microbial materials in different stages of</p><p>decay pooled with a variety of decomposition products of</p><p>different turnover rates. SOM is a major storehouse of car-</p><p>bon on a global scale. The accumulation of SOM, of which</p><p>about 58 % is carbon, occurs during ecosystem development</p><p>as a result of interactions between biota (e.g., autotrophs and</p><p>heterotrophs) and environmental controls (e.g., temperature,</p><p>moisture) [13]. The rate of SOM accumulation in different</p><p>types of natural ecosystems depends upon the litter inputs</p><p>(quantity and quality) and the rate of decomposition.</p><p>J. Dinakaran et al.</p><p>123</p></li><li><p>Obviously the rate and accumulation of SOM is strongly</p><p>related to the productivity of the recent/past vegetation,</p><p>physical and biological conditions in the soil, and the past</p><p>history of SOM inputs and land management activities. Thus</p><p>the SOM accumulation differs from natural ecosystems to</p><p>man-made ecosystems. Schlesinger [14] documented the</p><p>rate of SOC accumulation from polar desert</p><p>(0.2 g C m2 year-1) to temperate forest (12 g C m2 year-1)</p><p>ecosystem across the world. SOC accumulation in Indian</p><p>forest soils is about 20.31 Tg year-1 [15]. However, for the</p><p>last two decades there have been considerable amount of</p><p>work based on simulation models to calculate the SOM</p><p>accumulation rate/turnover in different types of ecosystems</p><p>(see in detail in SOM model section). The naturally occur-</p><p>ring organic carbon (OC) forms are derived from the</p><p>decomposition of plants and animals. In addition to that, the</p><p>anthropogenic additions such as pesticides and municipal</p><p>wastes are also the part of OC in soils [12]. In soil a wide</p><p>variety of OC forms are present, ranging from freshly</p><p>deposited litter such as leaves, twigs, and branches to highly</p><p>decomposed forms such as humus. Plant litter and microbial</p><p>biomass are the major parent materials for SOM formation.</p><p>As the plants grow, they absorb CO2 through photosynthesis</p><p>and incorporate a portion of this carbon into their body</p><p>structure. Thus, carbon sequestration by growing perennial</p><p>vegetation has been shown to be a cost-effective option for</p><p>mitigation of global climatic change.</p><p>The biological management of carbon in tackling climate</p><p>change has therefore essentially two components: (i) the</p><p>reduction in emissions from biological systems and (ii) the</p><p>increase in their storage of carbon. These can be achieved in</p><p>three ways: existing stores could be protected and the current</p><p>high rate of loss reduced; historically depleted stores could be</p><p>replenished by restoring ecosystems and soil; and, potentially,</p><p>new stores could be created by encouraging greater carbon</p><p>storage in areas that currently have little, through afforestation</p><p>[16]. At the same moment, carbon sequestration (by growing</p><p>forests) can be appropriate from ecological, environmental</p><p>and a socioeconomic point of view. The environmental per-</p><p>spective includes the removal of CO2 from the atmosphere,</p><p>the improvement of soil quality, and the increase in biodi-</p><p>versity. Socioeconomic benefits can be reflected through</p><p>increased yields [17] and monetary income from potential</p><p>carbon trading schemes [18]. Carbon sequestration projects</p><p>could also enhance local participation and understanding of</p><p>sustainable forest management practices.</p><p>Chronological Progress of SOC Research Across</p><p>the World</p><p>Table 1 shows the major progress and development in SOC</p><p>research. The major hitch in SOC research across the world</p><p>is that most of the studies have focused only on carbon</p><p>stock estimation and/or the process involved in the storage</p><p>of organic carbon in different ecosystems. This is due to</p><p>some error and/or lack of understanding of the estimation</p><p>of SOC stock in different ecosystems.</p><p>SOC stocks</p><p>In the early seventies to the nineties, most of the</p><p>researchers around the world showed their interest in</p><p>estimating the size/stock of the global SOC [19]. They</p><p>followed two different approaches to estimate the global</p><p>SOC stock. They are (a) soil taxonomy and (b) ecosystem-</p><p>based estimates. In the first approach (taxonomic</p><p>approach), they tabulated the SOC stocks based on the</p><p>determination of the area/extent and the average carbon</p><p>content in each of major soil taxonomic groups of the</p><p>world [20]. Two major soil classification/mapping schemes</p><p>were used in global carbon tabulation, i.e., US department</p><p>of agriculture soil taxonomy (USDA) and the food and</p><p>agricultural organizations (FAO) world soil map. Eswaran</p><p>et al. [20] calculated the SOC stocks (1576 Pg C) of the</p><p>worlds different soil orders. Among the different soil</p><p>orders, SOC stock was low in vertisols and high in histo-</p><p>sols. In ecosystem based approach, SOC stock was esti-</p><p>mated on the basis of generalized ecological life zones</p><p>which are distributed in relation to specific combinations of</p><p>mean annual precipitation and mean annual temperature</p><p>[21]. This approach estimated the global soil storage about</p><p>to be 2542.3 Pg of carbon. A recent study [22] estimated</p><p>the global SOC storage in the top 3 m depth of soil as</p><p>2,344 Pg C, with the first, second and third meter mea-</p><p>suring 1,502, 491 and 351 Pg C, respectively.</p><p>In India, for the first time, Jenny and Raychaudhuri [23]</p><p>studied extensively on estimating organic carbon status in</p><p>forests and cultivated lands with respect to different rainfall</p><p>and temperature. After a long span of time Gupta and Rao</p><p>[24] estimated the organic carbon stock of about 24.33 Pg of</p><p>carbon in soil ranging from surface to an average subsurface</p><p>depth of 0.44 to 1.86 m with the database of 48 soil series.</p><p>Subsequently Bhattacharya et al. [25] estimated the OC stock</p><p>as 63 Pg in five major physiographic regions of India</p><p>(northern mountains, the great plains, peninsular India, pen-</p><p>insular plateau and coastal plains and the islands) up to</p><p>150 cm depth. Among different orders of soils in India,</p><p>aridisols and inceptisols stored more amount of carbon which</p><p>is about 20.3 and 15.07 Pg C respectively followed by alfi-</p><p>sols, vertisols, entisols, mollisols, oxisols and ultisols [26].</p><p>Bhadwal and Singh [27] used three Land Use and Carbon</p><p>Sequestration (LUCS) models to estimate the sequestration of</p><p>carbon in different land use scenarios in India. The amount of</p><p>carbon sequestered in scenario LUCS-III is estimated to be</p><p>The Chronological Advancement of Soil Organic Carbon</p><p>123</p></li><li><p>Table 1 Major progress and development in soil organic carbon sequestration research</p><p>S.No Type...</p></li></ul>