天山高寒草原土壤团聚体结构与养分含量对模拟氮磷沉降的响应

Response of soil aggregate structure and nutrient content to the simulated nitrogen and phosphorus deposition in an alpine steppe of Tianshan Mountains

为更好地理解高寒草原土壤团聚体结构及其养分含量对氮(N)、磷(P)沉降增加的响应,于2018年开始依托全球营养网络(Nutrient Network)在巴音布鲁克草原生态系统研究站开展模拟氮磷沉降的短期(<5年)氮磷添加控制实验,设置对照(CK)、N添加、P添加、NP交互添加4个处理。N、P添加量均为10 g m^(-2)a^(-1)。于2021年8月采集植物与土壤样品,采用湿筛法分析土壤水稳定性团聚体组成,测定全土和各粒级团聚体有机碳(SOC)、总氮(TN)、总磷(TP)、速效氮(AN)和速效磷(AP)含量。研究结果表明:(1)巴音布鲁克高寒草原各粒级土壤团聚体比例从低到高依次为:0.053—0.25 mm、<0.053 mm、0.25—2 mm、和>2 mm,以>2 mm团聚体占主导,其比例在45.48%—71.81%之间。(2)N添加显著降低了0—10 cm土壤层>2 mm团聚体比例和团聚体稳定性,而P添加则显著降低了10—20 cm土壤层>2 mm团聚体比例和团聚体稳定性。(3)0—10 cm土壤层各粒级团聚体SOC含量显著高于10—20 cm土壤层;N添加显著提高了0—10 cm土壤层各粒级团聚体AN含量与N有效率,但显著降低了AP含量;P添加和NP交互添加总体上对团聚体养分没有显著影响。(4)0—10 cm土壤层团聚体AN含量与地上生物量具有显著的正相关关系;而团聚体AN含量、N有效率分别与AP含量、P有效率呈显著负相关关系;10—20 cm土壤层团聚体TP、AN、AP含量与N、P有效率均呈显著正相关关系。综上,10 g m^(-2)a^(-1)的氮磷添加降低了土壤团聚体稳定性且影响的土壤层不同,N添加和P添加分别影响0—10 cm和10—20 cm土壤层稳定性;N添加驱动了土壤团聚体N元素和P元素的再分配,分别显著提高和降低了土壤团聚体AN、AP的含量;P添加和NP交互添加总体上对团聚体养分影响不显著。

In order to examine the effects of the simulated nitrogen(N)and phosphorus(P)deposition on soil aggregate structure and nutrient content in alpine steppe,a short-term(<5 years)N and P addition experiment was set up in 2018 in Bayinbuluk Grassland Ecosystem Research Station relying on the Nutrient Network.There were four treatments in the experiment,including control treatment(CK),N addition,P addition,N and P interactive addition.The addition amount of N and P were 10 g m^(-2)a^(-1).In August 2021,plants and soil samples at 0—10 cm and 10—20 cm depth were sampled separately.Soil aggregates were classified using wet sieving method.The content of soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),available nitrogen(AN)and available phosphorus(AP)of bulk soil and aggregates with different particle sizes were analyzed.Our results revealed the following.(1)In Bayinbuluk alpine steppe,the proportion of water-stable soil aggregates from low to high was shown as following:0.053—0.25 mm,<0.053 mm,0.25—2 mm,and>2 mm.The aggregates>2 mm was dominant,with the proportion ranging from 45.48%to 71.81%.(2)N addition significantly reduced the proportion of aggregates>2 mm and the mean weight diameter(MWD)of aggregates in the soil layer of 0—10 cm,while P addition reduced them in the soil layer of 10—20 cm.(3)The SOC content in soil aggregates in 0—10 cm soil layer was significantly higher than it in 10—20 cm soil layer.N addition significantly increased the AN content and N efficiency(Percentage of available N in total N)in aggregates in the 0—10 cm soil layer,but significantly decreased the AP content.P addition and NP interactive addition had no significant effect on aggregate nutrients overall.(4)The AN content of aggregates in the soil layer of 0—10 cm was positively correlated to aboveground biomass,while AN content and N efficiency of aggregates were negatively correlated to AP content and P efficiency(Percentage of available P in total P).In the soil layer of 10—20 cm,TP,AN and AP content of aggregates were positively correlated to N and P efficiency.In conclusion,N and P addition of 10 g m^(-2)a^(-1)decreased the stability of soil aggregates and affected different soil layers:N addition and P addition affected the stability of soil aggregates in 0—10 cm and 10—20 cm soil layers,respectively.N addition,which drove the redistribution of N and P in soil aggregates with different particle sizes,significantly increased and decreased the AN and AP content of soil aggregates respectively.P addition and NP interactive addition had no significant effect on aggregate nutrients overall.