Response of soil aggregate-associated microbial and nematode communities to tea plantation age

Abstract

Understanding the changes of soil microbial and nematode communities within aggregate fractions is essential for maintaining the stability of soil biological communities and soil health in agricultural ecosystems. However, the short- and long-term influence of converting abandoned land to tea (Camellia sinensis L.) plantations on soil aggregate-associated biological communities is still poorly understood. In this study, soil microbial and nematode communities were analyzed in soil fractions of different sizes collected from 0 to 20 cm depth in four tea plantations with the same plants (cultivar was “Sichuan tea”) of various ages (16-, 23-, 31-, and 53-years) in the hilly area of western Sichuan in China. The aggregates were separated by a dry-sieving procedure into four fractions: large (>2 mm), medium (2–1 mm), small (1–0.25 mm) macro-aggregates, and micro-aggregates (<0.25 mm). Although soil microbial biomass (bacteria, fungi, and actinomycetes) was not correlated (P > 0.05) with most nematode abundance (bacterivores, plant-parasites, fungivores, and omnivores and predators) across aggregate fractions in different tea plantation ages, not only microbial biomass and nematode abundance but also their diversity was highest in the large macro-aggregates, indicating that these fractions had a complex biological community structure with more connections in soil food web, thus providing biological buffering and prohibiting the dominance of individual organisms via competition or predation. In the process of tea cultivation, the abundance of soil nematodes was largely dependent on microbial biomass in the macro-aggregates where pore space was large enough for nematodes to prey on microbes, while there were no correlations (P > 0.05) between microbial biomass and nematode abundance in the micro-aggregates. The 23-year-old tea plantation provided a relatively stable soil environment for the development of microbial and nematode communities, and subsequently induced an increase of soil microbial biomass, nematode abundance, and their diversity. Notably, the degradation of soil biological communities after 23-years underscores the need for sustainable soil management practices that would maintain the stability of soil biological communities and soil health after 23-years of tea cultivation in the hilly area of western Sichuan in China.