Introduction
Western Ghats, one of the world’s ten “hottest biodiversity hotspots”, was well covered with dense forest in the earlier days. Agro-ecosystems in the Western Ghats have depended on the forests for raw materials for food, fuel, fodder, fruits, timber, leaves, litter and various other products. Despite this, due to the expansion in area for agriculture, development of plantations and for other developmental activities, natural forests were cleared (Menon and Bawa, 1997; Jha et al., 2000). The burgeoning human population and decline in the per capita availability of land have resulted in increased exploitation of natural resources to a greater extent. The conversion of forest reserve to other land uses in recent times has resulted in many complex changes in the forest ecosystem, whose impact raises diverse ecological problems (Henrik et al., 2010; Awotoye et al., 2013). This destruction of natural forest from its niche as a result of its conversion has increased the need to assess the land use changes and their impact on land quality.
Global carbon cycle has gained paramount importance in the recent decades on account of alarming issues of climate change and global warming. Soil carbon is one of the components of global C cycle which plays a pivotal role in mitigating climate change by sequestering atmospheric carbon. Soil organic carbon pool is influenced by anthropogenic interventions, which could be by changes in land use or land cover (Khaledian et al., 2017; Hombegowda et al., 2016; Jaramillo et al., 2003). Changes in land cover and management practices result in changes in soil organic carbon stocks (Laganiere et al., 2010; Deng et al., 2013).
Land use changes such as forest clearing, cultivation and pasture introduction are also known to result in changes in soil chemical, physical and biological properties (Houghton et al., 1999), these changes vary with land cover and land management (Baskin and Binkley 1998; Celik, 2005). Soil physical and chemical properties are proposed as suitable indicators for assessing the effect of land use changes and management (Alvarez and Alvarez, 2000) .Assessment of soil properties upon conversion of natural forests for varying agricultural purposes is of utmost importance to detect early changes in soil quality (Islam and Weil, 2000). Several studies have been reported on assessment of C stocks upon conversion of natural forests to agricultural ecosystems indicating a decline in C concentration by 20- 50 per cent (Lal, 2005; Lemenih and Itanna, 2004). However, several physiological attributes of coffee make it interesting to understand the differences in soil nutrient status on cultivation of coffee. Coffee is an exhaustive crop and gives away major part of photosynthates and nutrients through coffee beans even at the level that may cause exhaustion of the plant (Anil Kumar et al., 2014). Thus, it becomes important to know how cultivation of coffee has affected forest soils in terms of soil fertility and land quality.
To understand the impact of land use changes from forest to coffee plantations, efforts were made to study and characterize soils from these ecosystems. The objectives of this study were to assess the changes in physical and chemical properties of soils with emphasis on soil organic carbon stocks in response to the land use changes. The tropical soils of selected study sites are characterized by high temperature, high and intensive rainfall and permeable soils, which are vulnerable to sheet erosion.