Potential Indicators of Soil Health Degradation in Different Land Use-Based Ecosystems in the Shiwaliks of Northwestern India

Arnab Bhowmik,Anu Kalia,Debasish Saha,Sandeep Sharma,Surinder Singh Kukal,Harmandeep Sharma

doi:10.3390/su11143908

Abstract

Identifying the importance of soil biology in different land use systems is critical to assess the present conditions of declining soil (C) and global land degradation while regulating soil health and biogeochemical nutrient cycling. A study was undertaken in a mixed watershed comprising of different land use systems (agricultural, grassland, agroforestry, and eroded); situated in the Shiwalik region in the foot hills of the lower Himalayas in India, a fragile ecosystem susceptible to land degradation. Soil samples from 0–15 and 15–30 cm depths were collected from these land use systems and analyzed for a suite of different soil health indicators, including physio-chemical soil properties, aggregate stability, soil microflora, and the enzymatic activities that are critical for nutrient cycling. Principal component analysis was used to group different land uses and understand their association with soil microflora, enzyme activities, and soil physio-chemical properties. We found that a greater number of soil microflora and enzymatic activities were associated with grassland and agroforestry land use systems. Aggregate-associated soil C correlated well with the soil microflora under different land use systems studied. The biplots revealed that the fungal:bacterial ratio (2 × 103–0.1 × 103) was a robust indicator of C accumulation and soil health, and was in greater association with the agroforestry land use system. Random forest, a non-parametric statistical test, on average explained that 68% to 92% of the variability in soil microbial population was due to land use and other soil health properties. Overall, the biological soil health indicators used in this study demonstrated the fact that land use management systems that employ constant crop cover with minimal disturbance have the potential to improve soil sustainability and ecological functioning.

Highlights

Human-induced land and environmental degradation has been a major global issue during the twentieth century, and is of high priority in the twenty-first century as well [1,2]
This study reports the potential use of microbial communities and soil enzymes as indicators of soil health degradation in a watershed with four different land use systems located in the lower Himalayas in India
The aggregate-associated soil organic C served as a better indicator of the soil microfloral population dynamics as compared to the enzymatic activity in these different land use systems, especially the eroded lands which had deposited organic matter debris

Summary

Introduction

Human-induced land and environmental degradation has been a major global issue during the twentieth century, and is of high priority in the twenty-first century as well [1,2]. Soil health indicators are measurable soil properties which are useful in defining the status of soil over a range of ecological situations reflecting the influence of soil management and in the future. It has always been a challenge for land managers to propose a set of effective, desirable, and sensitive soil health indicators due to the wide range over which these indicators vary in magnitude and importance. Effective soil health indicators should relate to major ecosystem functions like nutrient cycling (e.g., C and nitrogen (N) cycle) in the field under a specific land use management system. They vary at several spatial and temporal scales, biological soil health indicators are worth examining in relation to the key driving variables and knowledge of soil processes due to change in management [5]

Objectives

Results

Discussion

Conclusion