Effects of shrub encroachment on soil aggregate ecological stoichiometry and enzyme activity in alpine grassland

doi:10.11686/cyxb2020478

Abstract

Abstract:

Shrub encroachment is one of the key factors affecting soil organic carbon storage in alpine grassland. In this study， we compared soil properties with and without shrub encroachment in grasslands at the eastern margin of Qinghai-Tibetan Plateau. Soil parameters measured included the contents of organic carbon， total nitrogen， total phosphorus， and total potassium， and activities of sucrase， urease， phosphatase， catalase， protease and glucosidase， as well as the ecological stoichiometry characteristics of soil aggregates of various sizes. Our results showed that： 1） The contents of organic carbon， total nitrogen and total phosphorus in different sized aggregates decreased after shrub encroachment and were higher in large aggregates （0.053-0.25 mm） in size. 2） The C∶N， C∶P and N∶P ratios in soil aggregates increased after shrub encroachment. The maximum C∶N ratio was observed in the >2 mm aggregates. The maximum C∶P and N∶P ratios were observed in the 0.053-0.25 mm aggregates， and the minimum values were observed in <0.002 mm and 0.002-0.053 mm aggregates（P>0.05）. 3） Urease， sucrase， phosphatase， catalase and β-D glucosidase activities were elevated mainly in >0.25 mm aggregates at grassland and shrub encroachment. After shrub encroachment， sucrase activity increased， while the protease and phosphatase activities decreased. 4） Urease and β-D glucosidase activities were positively correlated with soil organic carbon and total nitrogen， sucrase and catalase activities were positively correlated with total potassium contents， and protease and phosphatase activities were positively correlated with total phosphorus. Soil biogenic materials are mainly concentrated in large aggregates in this region. However， large aggregates are easily broken by external interference， which shows that the phenomenon of shrub encroachment is not conducive to the sequestration of organic carbon in this area.

Key words: shrub encroachment in alpine grassland, soil aggregates, soil enzyme activity, soil biogenic material, ecological stoichiometric ratio

Wen-ming MA, Chao-wen LIU, Qing-ping ZHOU, Zhuo-ma DENGzeng, Si-hong TANG, Diliyaer·mohetaer, Chen HOU. Effects of shrub encroachment on soil aggregate ecological stoichiometry and enzyme activity in alpine grassland[J]. Acta Prataculturae Sinica, 2022, 31(1): 57-68.

Figures/Tables 7

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粒径 Particle size （mm）	草地类型 Grassland type	pH	土壤有机碳 Soil organic carbon （g·kg^-1）	全氮 Total nitrogen （g·kg^-1）	全磷 Total phosphorus （g·kg^-1）	全钾 Total potassium （g·kg^-1）
>2	未灌丛化草地Alpine grassland	5.57±0.07a	8.40±0.32a	0.74±0.03a	1.82±0.21a	19.55±1.08a
>2	灌丛化草地Shrub encroachment	5.49±0.22a	8.06±0.52a	0.70±0.02a	1.69±0.07a	19.58±1.69a
0.25~2	未灌丛化草地Alpine grassland	5.77±0.06a	8.41±0.46a	0.74±0.04a	1.92±0.26a	19.68±0.95a
0.25~2	灌丛化草地Shrub encroachment	5.45±0.10a	8.14±0.51a	0.72±0.03a	1.76±0.06b	19.80±1.51a
0.053~0.25	未灌丛化草地Alpine grassland	5.86±0.06a	8.84±0.53a	0.75±0.04a	1.92±0.21a	19.26±1.28a
0.053~0.25	灌丛化草地Shrub encroachment	5.67±0.07a	8.71±0.65a	0.76±0.05a	1.74±0.10a	20.10±1.65a
0.002~0.053	未灌丛化草地Alpine grassland	5.92±0.09a	6.59±0.38a	0.59±0.03a	1.49±0.21a	18.80±0.86a
0.002~0.053	灌丛化草地Shrub encroachment	5.76±0.07a	5.71±0.68a	0.51±0.05a	1.35±0.15a	19.03±1.25a
<0.002	未灌丛化草地Alpine grassland	6.03±0.06a	7.21±0.34a	0.66±0.44a	1.97±0.27a	20.20±1.34a
<0.002	灌丛化草地Shrub encroachment	5.77±0.09a	6.70±0.25a	0.61±0.02a	1.57±0.10a	20.20±1.82a

粒径 Particle size （mm）	草地类型 Grassland type	pH	土壤有机碳 Soil organic carbon （g·kg^-1）	全氮 Total nitrogen （g·kg^-1）	全磷 Total phosphorus （g·kg^-1）	全钾 Total potassium （g·kg^-1）
>2	未灌丛化草地Alpine grassland	5.57±0.07a	8.40±0.32a	0.74±0.03a	1.82±0.21a	19.55±1.08a
>2	灌丛化草地Shrub encroachment	5.49±0.22a	8.06±0.52a	0.70±0.02a	1.69±0.07a	19.58±1.69a
0.25~2	未灌丛化草地Alpine grassland	5.77±0.06a	8.41±0.46a	0.74±0.04a	1.92±0.26a	19.68±0.95a
0.25~2	灌丛化草地Shrub encroachment	5.45±0.10a	8.14±0.51a	0.72±0.03a	1.76±0.06b	19.80±1.51a
0.053~0.25	未灌丛化草地Alpine grassland	5.86±0.06a	8.84±0.53a	0.75±0.04a	1.92±0.21a	19.26±1.28a
0.053~0.25	灌丛化草地Shrub encroachment	5.67±0.07a	8.71±0.65a	0.76±0.05a	1.74±0.10a	20.10±1.65a
0.002~0.053	未灌丛化草地Alpine grassland	5.92±0.09a	6.59±0.38a	0.59±0.03a	1.49±0.21a	18.80±0.86a
0.002~0.053	灌丛化草地Shrub encroachment	5.76±0.07a	5.71±0.68a	0.51±0.05a	1.35±0.15a	19.03±1.25a
<0.002	未灌丛化草地Alpine grassland	6.03±0.06a	7.21±0.34a	0.66±0.44a	1.97±0.27a	20.20±1.34a
<0.002	灌丛化草地Shrub encroachment	5.77±0.09a	6.70±0.25a	0.61±0.02a	1.57±0.10a	20.20±1.82a

草地类型Grassland type	土壤团聚体Soil aggregate （mm）	碳氮比C/N	碳磷比C/P	氮磷比N/P
灌丛化草地 Shrub encroachment	>2	11.45±0.35a	4.79±0.70a	0.41±0.04ab
	0.25~2	11.33±0.36ab	4.62±0.62a	0.40±0.04ab
	0.053~0.25	11.43±0.34a	5.01±0.68a	0.43±0.04a
	0.002~0.053	11.18±0.62ab	4.27±0.90a	0.37±0.03b
	<0.002	11.02±0.22b	4.27±0.47a	0.38±0.03ab
未灌丛化草地 Alpine grassland	>2	11.37±0.27a	4.52±0.45a	0.39±0.03a
	0.25~2	11.41±0.24a	4.39±0.21a	0.38±0.02a
	0.053~0.25	11.29±0.23ab	4.44±0.56a	0.40±0.04a
	0.002~0.053	11.18±0.28ab	4.48±0.69a	0.40±0.58a
	<0.002	11.00±0.19b	4.08±0.39a	0.37±0.03a

草地类型Grassland type	土壤团聚体Soil aggregate （mm）	碳氮比C/N	碳磷比C/P	氮磷比N/P
灌丛化草地 Shrub encroachment	>2	11.45±0.35a	4.79±0.70a	0.41±0.04ab
	0.25~2	11.33±0.36ab	4.62±0.62a	0.40±0.04ab
	0.053~0.25	11.43±0.34a	5.01±0.68a	0.43±0.04a
	0.002~0.053	11.18±0.62ab	4.27±0.90a	0.37±0.03b
	<0.002	11.02±0.22b	4.27±0.47a	0.38±0.03ab
未灌丛化草地 Alpine grassland	>2	11.37±0.27a	4.52±0.45a	0.39±0.03a
	0.25~2	11.41±0.24a	4.39±0.21a	0.38±0.02a
	0.053~0.25	11.29±0.23ab	4.44±0.56a	0.40±0.04a
	0.002~0.053	11.18±0.28ab	4.48±0.69a	0.40±0.58a
	<0.002	11.00±0.19b	4.08±0.39a	0.37±0.03a

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