Distribution of organic carbon and nutrients in soil aggregates under different stand types of Cunninghamia lanceolata in southern Guangxi of China

ABSTRACT

Revealing the dynamics of soil organic carbon (C_org) and nutrients at aggregate scales is essential for improving our understanding of soil C_org mitigation and nutrient restitution in the Cunninghamia lanceolata plantations. In this study, soil C_org, total nitrogen (N_tot), available phosphorus (P_ava), and exchangeable cations (including calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), and sodium (Na⁺)) received the analysis in aggregate fractions acquired from 0 to 10 cm and 10–20 cm depths in the three different stand types, namely mixed stands of Cunninghamia lanceolata and Michelia macclurei (stand A), Cunninghamia lanceolata and Mytilaria laosensis (stand B), and pure stand of Cunninghamia lanceolata (stand C). Soil aggregates were classified into macro-aggregates (>2 mm), meso-aggregates (2–0.25 mm), and micro-aggregates (<0.25 mm) by the dry-sieving process. The two mixed stands displayed higher level of soil aggregate stability than the pure stand. Moreover, micro-aggregates acted as the main fractions that carried soil C_org, N_tot, and P_ava, and both micro-aggregates and macro-aggregates referred to the main fractions that carried exchangeable cations. As for the soil nutrient stocks, only the exchangeable K⁺ stock of the pure stand dominated among the C_org and nutrient stocks, in addition, the rest of the other nutrient stocks of the mixed forests (stands A and B) took an advantage over the pure stand. Moreover, the C_org and nutrient stocks in stands A and B were reflected in the macro-aggregates, differently, those of stand C were mainly reflected in the micro-aggregates. Thus, selecting suitable broadleaf tree species mixed with Cunninghamia lanceolata can alleviate the reduction of soil aggregate stability and the loss of soil nutrients, thus promoting soil resources to be sustainably utilized and protecting soil quality and health in southern Guangxi of China.

KEY WORDS:

• Fir plantation
• soil aggregate
• organic carbon
• nutrient

Acknowledgments

This work was funded by the National Natural Science Foundation of China (No. 31460196). We thank editors and anonymous referees for their constructive comments on the early version of this manuscript, which greatly improved the quality of our article.

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [31460196].