# Patterns and Drivers of Soil Respiration under Long-Term Citrus reticulate in Southern China

## TL;DR

This study examines how long-term citrus cultivation affects soil respiration and nutrients in southern China.

## Contribution

The study identifies specific soil properties and cultivation practices influencing soil respiration in citrus systems.

## Key findings

- Citrus cultivation increased soil carbon, nitrogen, and organic matter at different depths and slopes.
- Soil respiration decreased exponentially over time, with intercropping showing the highest respiration rate.
- Soil carbon and nitrogen were key drivers of respiration upslope, while dissolved organic carbon was important downslope.

## Abstract

Soil respiration (Rs) is a major source of carbon emission in terrestrial ecosystems. Despite the fact that the influence of land use practice on Rs has been widely studied, the patterns and drivers on Rs of Citrus reticulata cultivation, a worldwide land use practice are unclear. In this current study, we investigated the influence of long-term cultivation of Citrus reticulata (CO) and of CO intercropped with soybean (CB) on soil nutrients, water availability, and Rs in southern China. Results indicated that after 21 years of cultivation, CO and CB significantly increased total soil carbon (TC), total soil nitrogen (TN), and soil organic matter (OM) at 0–20 cm and 20–40 cm, both at upslope and downslope compared with bare soil (CK). However, soil moisture (SM), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) decreased under CB. In addition, no significant variation was found in soil pH between CK, CO, and CB. Across incubation time (56 days), Rs decreased exponentially with incubation time and CB showed the highest Rs rate irrespective of soil depth or topography. Linear regression further showed TC and TN as the two major factors influencing Rs upslope, while DOC was the dominant factor in regulating Rs downslope. These findings demonstrated that long-term cultivation of citrus significantly changed soil nutrients, water availability, and Rs rate.