Abstract
Soil respiration, soil enzymes, and microbial biomass are important in carbon cycling in the terrestrial ecosystem which is generally limited by environmental factors and soil carbon availability. Hence, we tried to assess the factors affecting the functional aspects of these processes in a semi-arid climate. We monitored soil respiration (surface) using a portable infrared gas analyzer (Q-Box SR1LP Soil Respiration Package, Qubit Systems, Canada) equipped with a soil respiration chamber (Model: G 180). Soil respiration was measured at midday during each season throughout the study period. Soil enzymatic activities and microbial biomass carbon (MBC) were analyzed following the standard protocol for a year during peak time in four seasons at 0–10 cm and 10–20 cm depth. Soil respiration shows significant variation with highest in monsoon (3.31 μmol CO2 m−2 s−1) and lowest in winter (0.57 μmol CO2 m−2 s−1). Similarly, β-glucosidase, dehydrogenase, and phenol oxidase activity ranged from 11.15 to 212.59 μg PNP g−1 DW h−1, 0.11 to 16.47 μg TPF g−1 DW h−1, and 4102.95 to 10187.55 μmol ABTS+ g−1 DW min−1, respectively. MBC ranged from 17.08 to 484.5 μg C g−1. Besides, soil respiration, soil enzymes (except β-glucosidase), and MBC were significantly correlated with soil moisture. Seasonality, optimum moisture and temperature played a significant role in determining variations in soil microbiological processes (except β-glucosidase activity); the carbon cycling in the study area is assisted by enzyme activity; dehydrogenase and phenol oxidase played a significant role in soil respiration; hence, this landscape is sensitive to environmental changes.
Highlights
Soil respiration accounts for the largest potential source of atmospheric carbon; even small changes in soil respiration can increase or decrease the atmospheric carbon dioxide level (Schimel 1995)
The principal component analysis (PCA) was carried out on all the studied soil microbiological and physical variables as factors and the analysis revealed that two principal components with eigenvalue more than one are responsible for the variance observed in the studied factors
All the studied microbiological processes were found higher in the monsoon season because of optimum moisture and temperature during the period. This can be observed by a significant positive correlation of microbial biomass carbon (MBC) and enzymatic activity with soil moisture, which is considered an important factor controlling soil processes occurring in semi-arid conditions
Summary
Soil respiration accounts for the largest potential source of atmospheric carbon; even small changes in soil respiration can increase or decrease the atmospheric carbon dioxide level (Schimel 1995). Soil respiration is carbon dioxide emission from soil surface which controls the primary carbon cycle in ecosystems (Jin et al 2007). Soil microbial biomass can act as a source or sink of available nutrients (Singh et al 1989) and changes in microbial biomass affect soil organic matter turnover (Yang et al 2010). The main component of soil microbial biomass is microbial biomass carbon (MBC), it is responsible for controlling the carbon and nutrient flows in ecological systems (Ross et al 1995; Shao et al 2015). Necromass of dead micro-organisms represents a huge amount of carbon in soil and can act as a readily available source of carbon for living micro-organisms (Xu et al 2018)
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