Introduction
With 1.39 billion populations, India is the world’s second largest populous country and is expected to overtake China by 2025 (UNDESA, 2019). Currently, India ranks third with the share of 7% of total carbon dioxide (CO2) emissions in the world (IEA, 2019) but ranks twentieth in the world per capita CO2emissions which is around 1.94 tonnes, less than half the global average of 4.8 tonnes CO2 (Ritchie and Roser, 2019). The lower value in per capita emissions of CO2 for India as when compared to the other major contributors of the world (except China) is due to inverse relationship between population of the contributors to that of per capita emissions of CO2.
Intergovernmental Panel on Climate Change (IPCC) categorized soil organic carbon (SOC) as one of five foremost carbon (C) pools that influences land use (LU) and land use change and forestry (LUC&F). SOC forms the major portion of the terrestrial carbon pool with reserve of about 1.5 x 103 to 2.0 x 103 billion metric tonnes of C in the global condition (Jobbágy and Jackson, 2000; Lal, 2016; Gaikwad et al ., 2018) whereas Indian soils stores 24.3 billion metric tonnes of C (Gupta et al ., 1994) representing two to three folds more than that of the atmosphere and foliage, respectively (Post et al ., 1990; Nath et al ., 2018). Forest land (FL) has been documented for amending atmospheric C concentration by behaving means of C source or sink (Wei et al ., 2015; Nath et al ., 2018). LUC from FL to agriculture/horticulture/ grass land/barren land/plantation caused soil degradation and soil properties resulted from intensive use, uneven terrain and changing climatic conditions (Palni et al ., 1998; Kumar et al ., 2017) may behave as C source (De Blécourt et al ., 2013; Abera and Wolde-Meskel, 2013; Guillaume et al ., 2015; Iqbal and Tiwari, 2016; Fan et al ., 2016). During the few decades earlier elevated CO2 in the atmosphere that has put forth the attention of the scientific researchers to the phenomenon of soil carbon storage (SCSt) (Negi & Gupta, 2010) and effect of LUC (Lal, 2004). LUC from FL to other land uses resulted loss of stored SOC. Stored SOC is the product of SCSt converted from atmospheric CO2 that is utilized for photosynthesis by plants (Koppad et al ., 2016).
India is at a very risk to climate change. The melting of Himalayan glaciers and changes in the monsoons are notable changes observed due to climate change. Agriculture releases around 16% of India’s total greenhouse gases (GHG) emissions. The climate change and losses of carbon from the soil has affected the soil health and ultimately crop productivity. To manage the problem of climate change, soil health and ensure food security, it is essential to sequester more carbon dioxide (CO2) in the soil. Recent years India has worked to increase the forest cover so that to become a net CO2sink and recent findings report that India has increased 7% of the global net leaf area in last 17 years during 2000 to 2017. Figure 1 represents the trend of share of the FL and CL in the total land area during the period 1990 to 2017. The FL has increased from 21.5% to 23.7% while the CL has decreased from 61.1% to 60.4%. This shows the efforts of the Indian governments of increasing area under forest and achieving the long-term target to fetch 33% of total area under FL cover-some 109 m.ha. from 79 m.ha.
Now management practices in the agriculture are shifting toward integrated nutrient management (INM) from inorganic alone (Sharmaet al ., 2019), conventional agriculture to conservation agriculture (Ladha et al ., 2009; Gathala et al ., 2013), and monocropping to crop rotation (Marais et al ., 2012) to restore the soil health and ensuring food security. These practices are integrated and approached through Climate Smart Agriculture Practices (CSAP) to the farmers. LUC by the appropriate land use managements (LUM) counteract several problems in the soils and help to obtain higher yields.
Conversion of FL to other LU especially to CL has occurred in want of fulfill the human needs. But past few years net emissions/removals of CO2by the FL has negative increased during 2000-2017 due to more absorption of CO2 by the increased FL area whereas net emissions/removal of CO2 of CL and GL remain constant positive consistently (Figure 2). But still several parts of the India are there where conversion of LU has changed the soil health adversely. This resulted intensive damage to soil carbon stocks (SCS) caused impacts on soil health and imbalance in environment.
LUC is identified via conversion of FL to other LU or vice versa (Kaulet al ., 2009). The efforts to accurately quantify the effects of various LUC on the global SCSt has been carried out large scale (Defrieset al ., 2002; Achard et al ., 2004; Houghton, 2008) but very few integrated approach to understand the impact of conversion of FL to other LU has been done in Indian context. Through this study the main objective is to attain a better knowledge of the Indian pattern of SOC changes with different land uses through a comparative analysis of data sets obtained through compilation of several studies carried out in the different parts of India in a holistic manner.
The pooled findings from several studies under different ecological variable regions are analyzed through meta-analysis approach. It is a statistical tool that considers experiments to assess the magnitude and direction of treatments outcome as well as pattern and sources of heterogeneity (Hedges et al ., 1999; Koricheva et al ., 2013). This study tells about the effect of LUCon SOC changesand nutrient management practice in rice and wheat crop with a meta-analysis approach to provide a quantitative analysis. In broad, the objective of this study is to 1). Quantify the effect of LUC on SOC and SCS, 2). Effect of organic matter addition on soil health and productivity related to LUM and 3). Correlations between SOC and soil properties in different LU.