Soil Microbial Community Structure and Physicochemical Properties in Amomum tsaoko-based Agroforestry Systems in the Gaoligong Mountains, Southwest China

Guizhou Liu,Man Jin,Chaonan Ma,Zhongsuzhi Chen,Lunlun Gao,Chuantao Cai

doi:10.3390/su11020546

Abstract

Amomum tsaoko is cultivated in forests of tropical and subtropical regions of China, and the planting area is expanding gradually. However, little attention has been paid to the impact of A. tsaoko cultivation on the soil characteristics of the regions. We analyzed the effects of the A. tsaoko-forest agroforestry system (AFs) on the composition of soil microbial communities with increasing stand ages. We also compared the soil physicochemical properties, microbial biomass, and phospholipid fatty acid (PLFA) composition between native forest (NF) and AFs. The results showed that the level of total carbon, nitrogen, and organic matter dramatically dropped in AFs with increasing stand ages. pH affected other soil properties and showed close correlation to total carbon (P = 0.0057), total nitrogen (P = 0.0146), organic matter (P = 0.0075), hydrolyzable nitrogen (P = 0.0085), available phosphorus (P < 0.0001), and available potassium (P = 0.0031). PLFAs of bacteria (F = 4.650, P = 0.037), gram-positive bacteria (F = 6.640, P = 0.015), anaerobe (F = 5.672, P = 0.022), and total PLFA (F = 4.349, P = 0.043) were significantly affected by different treatments, with the greatest value for NF treatment, and least value for AF5. However, the microbial biomass declined during the initial 5 years of cultivation, but it reached the previous level after more than 10 years of cultivation. Our research suggests that AFs is a profitable land-use practice in the Gaoligong Mountains and that AFs showed a recovering trend of the soil nutrient condition with increasing stand ages. However, the severe loss of nitrogen in the soil of AFs requires additional nitrogen during cultivation to restore it to pre-cultivation levels.

Highlights

Land resources are limited, and the area of arable land is decreasing significantly in response to construction occupation, natural disasters, ecological restoration, and agricultural structure adjustment [1]
With increasing of agroforestry system (AFs) stand ages, soil fertility was mainly changed by the increase in the contents of available phosphorous, available potassium and total potassium, and the decrease in the contents of hydrolyzable nitrogen, total nitrogen, total carbon and organic matter
Our studies demonstrated that the soil microbial community structure was significantly changed from native forest (NF) to AFs (Figure 4)

Summary

Introduction

The area of arable land is decreasing significantly in response to construction occupation, natural disasters, ecological restoration, and agricultural structure adjustment [1]. Shifting cultivation has been forbidden by the government since the 1980s in this region to preserve natural resources, e.g., wild medicinal plants, threatened plants and animals, and to manage ecosystems sustainably in steeply-sloping environments. As an economic or medicinal plant with higher economic income and lower labor input, the planting area of A. tsaoko was expanding. It has developed into a mature planting model—the A. tsaoko-forest agroforestry system (AFs)

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Conclusion