Characteristics of soil enzymes stoichiometry in rhizosphere of understory vegetation in subtropical forest plantations

Authors Gao Yuqiu; Dai Xiaoqin; Wang Jianlei; Fu Xiaoli; Kou Liang; Wang Huimin

Journal Chinese Journal of Plant Ecology , 2019,3:43

Abstract Aims The objective was to explore the stoichiometry of rhizosphere soil enzymes under major understory vegetation and their responses to plantation types and seasons. Methods Rhizosphere soils of understory shrubs (Loropetalum chinense, Adinandra millettii and Eurya muricata) and herbs (Woodwardia japonica and Dryopteris atrata) were sampled in the early growth stage (April) and the vigorous growth stage (July) in Cunninghamia lanceolata, Pinus massoniana and Pinus elliottii plantations at Qianyanzhou Ecological Research Station, Taihe, Jiangxi. Potential activities of beta-1,4-glucosidase (BG, carbon (C) acquiring enzyme), beta-1,4-N-acetylglucosaminidase (NAG, nitrogen (N) acquiring enzyme) and leucine aminopeptidase (LAP, N-acquiring enzyme), acid phosphatase (AP, phosphorus (P) acquiring enzyme) and their stoichiometric ratios were measured. Soil physical and chemical properties were also analyzed. Important findings The results found that (1) rhizosphere soil extracellular enzyme activities associated with C and N acquisition and BG:AP (enzyme C:P) were significantly different among understory species, but P acquisition were not. Both forest stand types and sampling seasons influenced BG:(NAG+LAP) (enzyme C:N). Interactions of understory species, forest stand types and seasons observably affected enzyme C:P. Principal component analysis showed that rhizosphere soil enzyme activities and ecoenzymatic stoichiometry differed significantly among different understory species (Loropetalum chinense was obviously different from Eurya muricata, and both of them were evidently different from other understory species), forest stand types (Cunninghamia lanceolata was different from Pinus massoniana and Pinus elliottii plantations) and sampling seasons. Soil NO_3~--N, NH_4~+-N, DOC content and C:N were the main edaphic abiotic factors influencing the rhizosphere soil enzyme activities and ecoenzymatic stoichiometry. (2) Standardized major axis analysis showed that there were significantly linear relationship among lg(BG), lg(NAG+LAP) and lg(AP) of rhizosphere soils of understory species. lgBG:lg(NAG+LAP):lgAP(enzyme C:N:P) was approximately 1:1:1.3. Rhizosphere soil enzyme C:P and (NAG+LAP):AP (enzyme N:P) of understory species were 0.14 and 0.15, respectively. The regression slopes of lg(BG), lg(NAG+LAP) and lg(AP) deviated significantly from 1 because AP activities were much higher than BG activities and NAG+LAP activities. This study found that rhizosphere soil enzyme activities and ecoenzymatic stoichiometry were affected by understory species, forest stand types and sampling seasons in which substrate availability played an important role. Compared with C- and N-acquiring enzymes, microorganisms allocated more resources to the production of P-acquiring enzymes, which implied that the growth and activity of soil microorganisms were much more limited by P in rhizosphere soil of understory vegetation in subtropical plantations.

Species covered 杉木 Cunninghamia lanceolata 马尾松 Pinus massoniana 檵木 Loropetalum chinense 杨桐 Adinandra millettii