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

doi:10.17521/cjpe.2018.0299

Abstract

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 β-1,4-glucosidase (BG, carbon (C) acquiring enzyme), β-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 NO₃ ^--N, NH₄ ⁺-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.

http://jtp.cnki.net/bilingual/detail/html/ZWSB201903008

Key words: plantation, soil extracellular enzyme, ecological stoichiometry, red soils

GAO Yu-Qiu, DAI Xiao-Qin, WANG Jian-Lei, FU Xiao-Li, KOU Liang, WANG Hui-Min. Characteristics of soil enzymes stoichiometry in rhizosphere of understory vegetation in subtropical forest plantations[J]. Chin J Plant Ecol, 2019, 43(3): 258-272.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2018.0299

https://www.plant-ecology.com/EN/Y2019/V43/I3/258

Figures/Tables 8

Table 1 Characteristics of understory shrub and herb species in three subtropical plantations

林分类型 Forest stand type	林下植被类型 Understory species	基径 Basal diameter (mm)	高度 Height (cm)	冠幅 Crown width (cm)	盖度 Coverage (%)	重要值 Importance value (%)
杉木林 Cunninghamia lanceolata forest	檵木 Loropetalum chinense	11.9 ± 2.7	126 ± 31	81 ± 15	-	19.72
	杨桐 Adinandra millettii	13.1 ± 1.0	152 ± 13	94 ± 7	-	30.44
	格药柃 Eurya muricata	13.2 ± 1.5	142 ± 16	86 ± 9	-	32.71
	狗脊蕨 Woodwardia japonica	-	94 ± 12	-	71 ± 7	3.09
	暗鳞鳞毛蕨 Dryopteris atrata	-	60 ± 5	-	43 ± 8	1.89
马尾松林 Pinus massoniana forest	檵木 Loropetalum chinense	18.9 ± 2.0	413 ± 41	144 ± 16	-	33.68
	杨桐 Adinandra millettii	26.7 ± 2.3	376 ± 64	160 ± 12	-	39.88
	格药柃 Eurya muricata	13.2 ± 1.1	302 ± 50	81 ± 6	-	31.43
	狗脊蕨 Woodwardia japonica	-	99 ± 6	-	60 ± 7	3.85
	暗鳞鳞毛蕨 Dryopteris atrata	-	64 ± 6	-	53 ± 7	3.41
湿地松林 Pinus elliottii forest	檵木 Loropetalum chinense	25.7 ± 1.7	244 ± 34	180 ± 11	-	36.39
	杨桐 Adinandra millettii	20.3 ± 3.1	206 ± 21	118 ± 16	-	33.11
	格药柃 Eurya muricata	19.6 ± 3.8	112 ± 25	106 ± 18	-	19.22
	狗脊蕨 Woodwardia japonica	-	86 ± 10	-	73 ± 8	4.15
	暗鳞鳞毛蕨 Dryopteris atrata	-	70 ± 4	-	38 ± 5	2.07

变异来源 Source of variation	酶相关参数 Parameter of soil enzyme
	BG	NAG+LAP	AP	BG:(NAG+LAP)	BG:AP	(NAG+LAP):AP
林分类型 Forest stand types (F)	0.061	0.881	0.156	0.013^*	0.092	0.938
林下植被类型 Understory species (U)	0.009^**	0.010^*	0.173	0.165	0.027^*	0.286
取样季节 Sampling seasons (S)	0.066	0.575	0.148	0.032^*	0.082	0.113
F × U	0.556	0.920	0.423	0.845	0.580	0.821
F × S	0.070	0.054	0.089	0.294	0.057	0.122
U × S	0.112	0.792	0.957	0.331	0.167	0.573
F × U × S	0.260	0.396	0.823	0.495	0.036^*	0.221

Fig. 1 Rhizosphere soil enzyme activities of understory vegetation under different forest stand types in subtropical plantations (mean + SE, n = 5). CL, Cunninghamia lanceolata forest; PM, Pinus massoniana forest; PE, Pinus elliottii forest. LC, Loropetalum chinense; AM, Adinandra millettii; EM, Eurya muricata; WJ, Woodwardia japonica; DA, Dryopteris atrata. Different lowercase letters were significantly different among different understory vegetation species of the same forest stand types at the same sampling season (p ＜ 0.05), Different uppercase letters were significantly different among different stand types at the same sampling season (p ＜ 0.05). BG, β-1,4-glucosidase; NAG+LAP, the sum of β-1,4-N-acetylglucosaminidase and leucine aminopeptidase; AP, acid phosphatase.

Fig. 2 Rhizosphere soil ecoenzymatic stoichiometry of understory vegetation under different forest stand types in subtropical plantations (mean + SE, n = 5). CL, Cunninghamia lanceolata forest; PM, Pinus massoniana forest; PE, Pinus elliottii forest. LC, Loropetalum chinense; AM, Adinandra millettii; EM, Eurya muricata; WJ, Woodwardia japonica; DA, Dryopteris atrata. Different lowercase letters were significantly different among different understory vegetation species of the same forest stand types at the same sampling season (p ＜ 0.05), Different uppercase letters were significantly different among different stand types at the same sampling season (p ＜ 0.05). BG, β-1,4-glucosidase; NAG+LAP, the sum of β-1,4-N-acetylglucosaminidase and leucine aminopeptidase; AP, acid phosphatase.

Fig. 3 Standardized major axis regressions of the log-transformed soil C-, N-, and P-acquiring enzyme activities in subtropical plantations (n = 150). The colors represent the forest stand types: red symbols, Cunninghamia lanceolata forest; green symbols, Pinus massoniana forest; blue symbols, Pinus elliottii forest. Filled symbols and open symbols respectively represent the sampling seasons at April and July.CL, Cunninghamia lanceolata forest; PM, Pinus massoniana forest; PE, Pinus elliottii forest. LC, Loropetalum chinense; AM, Adinandra millettii; EM, Eurya muricata; WJ, Woodwardia japonica; DA, Dryopteris atrata. BG, β-1,4-glucosidase; NAG+LAP, the sum of β-1,4-N-acetylglucosaminidase and leucine aminopeptidase; AP, acid phosphatase.

Fig. 4 Principal component analysis (PCA) of soil enzyme activities and ecoenzymatic stoichiometry in subtropical plantations. The effect of sampling seasons is from the average of PCA scores of soil enzyme activities and ecoenzymatic stoichiometry of understory vegetation within the same season. The effect of forest stand types is from the average of PCA scores of soil enzyme activities and ecoenzymatic stoichiometry of understory vegetation within the same forest stand type. The effect of understory species is from the average of PCA site scores of soil enzyme activities and ecoenzymatic stoichiometry of the same understory species. The colors represent the forest stand types: red symbols, Cunninghamia lanceolata forest; green symbols, Pinus massoniana forest; blue symbols, Pinus elliottii forest. CL, Cunninghamia lanceolata forest; PM, Pinus massoniana forest; PE, Pinus elliottii forest; LC, Loropetalum chinense; AM, Adinandra millettii; EM, Eurya muricata; WJ, Woodwardia japonica; DA, Dryopteris atrata.

Fig. 5 Redundancy analysis (RDA) of soil enzyme activities, ecoenzymatic stoichiometry and physical and chemical properties in subtropical plantations. NO3--N, nitrate nitrogen; NH4+-N, ammonium nitrogen; DOC, dissolved organic carbon; C:N, the ratio of total carbon to total nitrogen. BG, β-1,4-glucosidase; NAG+LAP, the sum of β-1,4-N-acetylglucosaminidase and leucine aminopeptidase; AP, acid phosphatase.

Table 3 Results (p-value) of multi-way repeated measures ANOVAs on the effects of forest stand types, understory species, sampling seasons and their interactions on four major soil nutrient factors in subtropical plantations

变异来源 Source of variation	DOC	NH₄⁺-N	NO₃^--N	C:N
林分类型 Forest stand types (F)	0.200	0.021^*	0.221	0.112
林下植被类型 Understory species (U)	0.000^**	0.002^**	0.002^**	0.000^**
取样季节 Sampling seasons (S)	0.226	0.003^**	0.178	0.296
F × U	0.735	0.658	0.506	0.058
F × S	0.407	0.384	0.009^**	0.623
U × S	0.311	0.095	0.084	0.267
F × U × S	0.129	0.511	0.270	0.800

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