等高反坡阶措施下坡耕地球囊霉素相关土壤蛋白对土壤碳氮储量的贡献

Contribution of glomalin⁃related soil protein to soil carbon and nitrogen storage in sloping farmland under contour reverse⁃slope terrace measures

为证实坡面微地形改造措施—等高反坡阶(CRT)对坡耕地的生态修复功能,揭示CRT对球囊霉素相关土壤蛋白(GRSP)含量及土壤碳氮储量贡献的影响与机制至关重要。通过分析原状(CK)和CRT处理下旱季和雨季坡耕地0—5、5—15、15—30 cm土层中总GRSP(T-GRSP)、易提取GRSP(EE-GRSP)、土壤有机碳(SOC)与土壤全氮(TN)在CRT阶上和阶下及CK对应位置处的时空分布特征,探讨CRT措施下GRSP对土壤碳氮储量的贡献,揭示相关机制。结果表明:(1)CRT坡耕地土壤T-GRSP、EE-GRSP、SOC和TN的含量较CK显著提高(P<0.05),增幅分别为16.6%—189%、7.28%—102%、1%—68.3%和7.29%—79.7%。且CRT对坡耕地GRSP含量的提升效果总体表现为雨季强于旱季、表层(0—5 cm)土壤高于深层(15—30 cm)、阶下优于阶上。(2)相比CK,CRT坡耕地旱季和雨季SOC储量分别提高8.06%和13.5%,TN储量提高7.01%和12.1%。T-GRSP对SOC和TN储量的贡献率较CK分别提高8.5%—141%和2.58%—133%,EE-GRSP对SOC和TN储量的贡献率较CK分别提高1.38%—82%和5.25%—87.2%。且CRT对坡耕地SOC和TN储量提升效果雨季优于旱季,对表层土壤T-GRSP对SOC和TN贡献率的提升效果表现为雨季强于旱季、阶下强于阶上。(3)CRT极大提高了坡耕地T-GRSP与土壤孔隙度、SOC和TN的正相关性。相比CK,相关系数(R~2)分别由0.17、0.26和0.29增至0.51、0.66和0.64。因此,CRT措施不仅降低了坡耕地SOC和TN的流失,还通过提高有机质含量改善土壤通气透水性,进而提高坡耕地GRSP的分泌与累积,同时提高GRSP对碳氮的贡献率,促进了土壤碳氮的固持与封存。

In order to confirm the ecological restoration function of slope microtopographic modification measure—contour reverse⁃slope terrace(CRT)on sloping farmland,it is extremely critical to reveal the effects and mechanisms of CRT on the glomalin⁃related soil protein(GRSP)content and contribution to soil carbon and nitrogen storage.The total GRSP(T⁃GRSP),easily extractable GRSP(EE⁃GRSP),soil organic carbon(SOC),and total nitrogen(TN)contents were determined in the soil of two terrace positions(above and below the terrace)and three depths(0—10,5—15 and 15—30 cm)of CRT and the corresponding positions of unmodified(CK)sloping farmland.The contribution of GRSP to soil carbon and nitrogen storage under CRT was explored,and the relevant mechanism was revealed.The results showed that:(1)comparing with CK,the contents of T⁃GRSP,EE⁃GRSP,SOC,and TN in CRT significantly increased by 16.6%—189%,7.28%—102%,1%—68.3%,and 7.29%—79.7%,respectively(P<0.05).In addition,the promotion of CRT on GRSP content in sloping farmland was generally better in the rainy season than that in the dry season,higher in the surface soil(0—5 cm)than that in the deep soil(5—15 cm),and better in the slope below the terrace than that above the terrace.(2)Comparing with CK,SOC and TN storage in CRT sloping farmland increased by 8.06%vs.13.5%and 7.01%vs.12.1%in the dry and rainy seasons,respectively.Comparing with CK,the contribution rate of T⁃GRSP to SOC and TN in CRT increased by 8.5%—141%and 2.58%—133%,meanwhile,the contribution rate of EE⁃GRSP to SOC and TN in CRT increased by 1.38%—82%and 5.25%—87.2%.Moreover,the enhancement of CRT on SOC and TN storage in the rainy season was better than that in the dry season,and the enhancement of CRT on the contribution rate of T⁃GRSP to SOC and TN in surface soil was stronger in the rainy season than that in the dry season,and stronger in the slope below the terrace than that above the terrace.(3)CRT measures greatly improved the positive correlations between T⁃GRSP and soil porosity,SOC,and TN comparing with CK,while the correlation coefficients(R2)increased from 0.17,0.26,and 0.29 to 0.51,0.66,and 0.64,respectively.The results indicated that CRT measures not only reduced the loss of SOC and TN in sloping farmland,but also improved the soil aeration and permeability by increasing the content of organic matter,thus increasing the secretion and accumulation of GRSP in sloping farmland.In addition,soil carbon and nitrogen retention and storage were promoted through increasing the contribution rate of GRSP to carbon and nitrogen by CRT measures.