控制降水梯度对荒漠草原优势植物叶功能性状及土壤养分的影响

The effects of precipitation gradient control on the leaf functional traits and soil nutrients of the dominant plants in a desert steppe

探究植物叶功能性状随降水梯度的变化规律,对揭示干旱区优势植物对环境变化的响应和适应策略至关重要。以盐池荒漠草原为研究对象,采用遮雨棚和喷灌系统控制降水梯度,分析了优势植物蒙古冰草(Agropyron mongolicum)、短花针茅(Stipa breviflora)及达乌里胡枝子(Lespedeza davurica)叶功能性状变异,以及土壤水分、养分和微生物特性与响应性状间的相关关系。结果表明:HW(增水50%)处理下3个植物LA(叶面积)、LDMC(干物质含量)显著增大,LW处理(减水50%)下短花针茅和达乌里胡枝子LA、LDMC显著减小,降水处理对短花针茅和达乌里胡枝子SLA(比叶面积)影响不显著,LW处理显著提高了蒙古冰草SLA;LW处理显著提高了蒙古冰草和短花针茅LNC(叶氮含量)和LPC(叶磷含量);HW显著降低了土壤C、N含量,LW和HW均显著减少了真菌数量,而放线菌数量、微生物生物量C、N显著增加;3种优势植物LA均与土壤水分显著正相关,蒙古冰草和短花针茅通过提高SLA、LNC及LNP来适应干旱生境,蒙古冰草和短花针茅LNC及LNP是表征土壤P、微生物生物量有效性的关键指标,达乌里胡枝子通过自我调节养分利用策略来适应C、N、P含量和微生物活性较低的生境,从而决定其在群落中的优势地位。

Investigating how leaf functional traits change with precipitation gradients is important for understanding the dominant plant adaptation strategies to cope with environmental change.The functional traits of the desert steppe dominant plants,Agropyron mongolicum,Stipa breviflora,and Lespedeza davurica varieties,were analyzed,as were the correlations between soil moisture,nutrients,microbial characteristics,and the response traits.This field study was conducted at Dashuikeng Grassland Research Station,Yanchi County(106°58′E,37°24′N,average elevation,1560 m),Ningxia Hui Autonomous Region,China.This region covers a large ecosystem of desert steppe that characterized by low rainfall and uneven precipitation,along the southwest edge of the Mu Us Sandy Land.In the study desert steppe area on the southeastern margin of the Tengger Desert,the average annual precipitation was only 298.3 mm during the 60 years from 1959 to 2019.The precipitation was regulated by the measurement of artificial rain using rainwater shed and sprinkler irrigation technologies,in order to evaluate precipitation effects on the biological soil crusts in desert steppe compared with natural precipitation.12 precipitation treatments(6 m×6 m)were set up at the test station in early March 2018,where 3 m wide buffer zone was designed between each plot.Control conditions of precipitation were designed via the shelter and sprinkler irrigation system,including 3 precipitation treatments,natural precipitation(CK),low water treatment(LW,50%water reduction),and high water treatment(HW,50%increase).Each precipitation treatment has 4 replicates.In the same period,small weather stations were set up in the test area.TRIME⁃PICO TDR Portable Soil Moisture Meter(made in Germany)was used for the data collection of precipitation in the soil water depth of 10 cm.The results showed that the leaf area(LA)and leaf dry matter content(LDMC)of all plants increased significantly with high water treatment(HW,50%increase),and low water treatment(LW,50%water reduction)significantly reduced the LA and LDMC of Stipa breviflora and Lespedeza davurica.Precipitation had no effect on the specific leaf area(SLA)of Stipa breviflora but the SLA of Agropyron mongolicum significantly increased with the LW treatment.LW significantly improved the leaf nitrogen content(LNC)and leaf phosphorus content(LPC)of Agropyron mongolicum and Stipa breviflora.In Agropyron mongolicum and Stipa breviflora,LW significantly improved the leaf nitrogen content(LNC)and leaf phosphorus content(LPC).HW significantly reduced the soil carbon(C)and nitrogen(N)content,and both treatments significantly reduced the number of fungi,but the number of actinomycetes and the soil microbial biomass carbon(SMBC)and nitrogen(SMBN)significantly increased.All plants had a significant positive correlation between LA and soil moisture.Agropyron mongolicum and Stipa breviflora adapted to an arid habitat by increasing SLA,LNC,and LPC,and the key indicators of soil phosphorus(P)and the effectiveness of microbial biomass may be LNC and LPC.Lespedeza davurica used self⁃regulating nutrient utilization strategies to adapt to habitats with low C,N,and P and low microbial activity,thereby confirming its dominant position in the community.