Recovery of soil microbial biomass, stoichiometry, and herb‐layer diversity with chronosequence of farmland land abandonment in the central Himalayas, India

Abstract

Revegetation after farmland abandonment not only changes the aboveground biodiversity but also soil physicochemical properties and soil microbial biomass. However, how the revegetation after farmland abandonment influences soil properties and herb‐layer biodiversity remains unclear. In the present study, we examined the variation in soil chemical and biological properties (soil microbial biomass, stock, and stoichiometry), herb‐layer diversity indices, and aboveground biomass, their relationships in a chronosequence of 2, 5, 7, 11, 16, and 35 years following revegetation of abandoned farmland in the central Himalaya, India. Results revealed that the diversity indices, biomass, and soil properties significantly changed over successional stages. The species in the plant community shifted from the forbs in earlier stages to grasses and sedges in later stages. Our results indicated that the soil microbial carbon (C) and nitrogen (N) contents and stocks increased along the chronosequence and were highest at the 35‐year‐old fallow. However, soil microbial phosphorus (P) contents and stock generally decreased with time. The soil nutrient and microbial biomass were significantly correlated, which indicate close coupling between soil and microbial C, N, and P contents. Soil, microbial C/P, and N/P ratios were the lowest in 7‐ and 11‐year‐old fallows, indicating that middle‐aged fallows were more P‐limited. Our results suggest that revegetation changes the soil and microbial stoichiometry, potentially changing the vegetation composition and nutrient cycling of the abandoned farmland ecosystems.