Hunan Provincial Key Laboratory of Rural Ecosystem Health in Dongting Lake Area, College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, China.
Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Brisbane, QLD, 4111, Australia.
Appl Microbiol Biotechnol. 2021 Dec;105(23):8907-8920. doi: 10.1007/s00253-021-11663-7. Epub 2021 Nov 4.
Carbon dioxide (CO) emissions from forest ecosystems originate largely from soil respiration, and microbial heterotrophic respiration plays a critical role in determining organic carbon (C) stock. This study investigated the impacts of successive nitrogen (N) and phosphorus (P) fertilization after 9 years on soil organic C stock; CO emission; and microbial biomass, community, and function in a Chinese fir plantation. The annual fertilization rates were (1) CK, control without N or P fertilization; (2) N50, 50 kg N ha; (3) N100, 100 kg N ha; (4) P50, 50 kg P ha; (5) N50P50, 50 kg N ha + 50 kg P ha; and (6) N100P50, 100 kg N ha + 50 kg P ha. The N100P50 treatment had the highest cumulative soil CO emissions, but the CK treatment had the lowest cumulative soil CO emissions among all treatments. The declines of soil organic C (SOC) after successive 9-year fertilization were in the order of 100 kg N ha year > 50 kg N ha year > CK. Compared to the CK treatment, successive N fertilization significantly changed soil microbial communities at different application rates and increased the relative gene abundances of glycoside hydrolases, glycosyl transferases, carbohydrate-binding modules, and polysaccharide lyases at 100 kg N ha year. Relative to P fertilization alone (50 kg P ha year), combined N and P fertilization significantly altered the soil microbial community structure and favored more active soil microbial metabolism. Microbial community and metabolism changes caused by N fertilization could have enhanced CO emission from heterotrophic respiration and eventually led to the decrease in organic C stock in the forest plantation soil. KEY POINTS: • N fertilization, alone or with P, favored more active microbial metabolism genes. • 100 kg N ha fertilization significantly changed microbial community and function. • N fertilization led to a "domino effect" on the decrease of soil C stock.
二氧化碳（CO）排放主要来自森林生态系统的土壤呼吸，而微生物异养呼吸在决定有机碳（C）储量方面起着关键作用。本研究调查了连续 9 年施氮（N）和磷（P）肥后对杉木人工林土壤有机 C 储量、CO 排放以及微生物生物量、群落和功能的影响。每年的施肥率分别为（1）CK，不施 N 或 P 的对照；（2）N50，50kgNha；（3）N100，100kgNha；（4）P50，50kgPha；（5）N50P50，50kgNha+50kgPha；和（6）N100P50，100kgNha+50kgPha。N100P50 处理的土壤 CO 累积排放量最高，但 CK 处理的土壤 CO 累积排放量最低。连续 9 年施肥后土壤有机 C（SOC）的减少量顺序为 100kgNha 年>50kgNha 年>CK。与 CK 处理相比，连续 N 施肥在不同施用量下显著改变了土壤微生物群落，并增加了 100kgNha 年糖苷水解酶、糖基转移酶、糖基结合模块和多糖裂解酶的相对基因丰度。与单独施 P（50kgPha 年）相比，N 和 P 联合施肥显著改变了土壤微生物群落结构，有利于土壤微生物代谢更活跃。N 施肥引起的微生物群落和代谢变化可能增强了异养呼吸的 CO 排放，最终导致森林人工林土壤有机 C 储量减少。关键点：•N 施肥，单独或与 P 一起，有利于更活跃的微生物代谢基因。•100kgNha 施肥显著改变了微生物群落和功能。•N 施肥导致土壤 C 储量减少的“多米诺效应”。
