不同修剪频次和丝茅入侵量对细叶结缕草竞争力和草坪质量的影响

Effects of mowing frequency on competitiveness and quality of Zoysia tenuifolia lawn invaded by Imperata koenigii

针对亚热带地区暖季型草坪夏季易受丝茅入侵影响的问题,通过设置4个修剪频次(0~3次·月-1),对取代试验设计形成的5个丝茅侵入量(10%、20%、30%、40%、50%)的细叶结缕草草坪,进行留茬高度7 cm,连续3个月修剪处理后,测定丝茅和结缕草地下和地上相对产量、相对产量和、攻击力、竞争平衡指数等竞争参数,分析丝茅和结缕草的株高、分蘖数、叶数、生物量和根茎比等生长参数,以密度、质地、叶色、均一性、草层高度和生物量等指标对草坪质量进行综合评定,研究修剪频次对不同丝茅侵入量下结缕草竞争力、单株生长及草坪质量的影响。结果表明:1)修剪频次对丝茅和结缕草的地上和地下竞争参数产生显著影响(P<0.05),修剪增加了两种植物地上部分的拮抗作用,2~3次·月-1修剪则降低了地下部分的拮抗作用。2)结缕草地上部分受修剪频次和丝茅比例的影响大于地下部分,1次·月-1修剪可提高结缕草地上竞争力,2次·月-1修剪可提高其地下竞争力,修剪频次和侵入量协同作用增加了丝茅对结缕草的根系攻击力。3)修剪频次和侵入量对丝茅和结缕草的后续生长产生显著影响(P<0.05),1~2次·月-1修剪增加了两种植物的分蘖数和叶片数,2次·月-1修剪下结缕草的分蘖数和叶片数增加约40%,丝茅比例≥10%下结缕草生物量降低,≥20%下结缕草分蘖减少,≥30%下结缕草株高增加而叶数减少,修剪频次是影响结缕草株高、分蘖数、叶片数和根茎比的主要因子,丝茅侵入量主要影响结缕草的单株生物量。4)修剪频次主要影响草坪的密度、高度和生物量,丝茅比例主要影响草坪的质地、叶色和均一性(P<0.05),≤10%丝茅比例和2次·月-1修剪下草坪综合质量高于其他处理,草坪质量主要受修剪频次影响,丝茅比例影响次之。5)1~2次·月-1修剪可显著提高受丝茅入侵的细叶结缕草的地上或地下竞争力,促进结缕草分蘖形成,降低草坪高度,提升草坪密度和质地,但修剪无法改变结缕草相对丝茅地上、地下竞争力弱的特点,故控制丝茅侵入量≤10%和2次·月-1修剪是夏季结缕草草坪养护的基本要求。

Warm-season lawns are vulnerable to Imperata koenigii invasion in summer in subtropical regions.The purpose of this study was to determine the effects of mowing frequency on the competitiveness,plant growth,and quality of a Zoysia tenuifolia lawn invaded by I.koenigii to varying degrees.We established an experiment in which Z.tenuifolia lawn was artificially planted with I.koenigii at five different proportions(10%,20%,30%,40%,50%)and mowed at four different frequencies(0-3 times per month)to a stubble height of 7 cm for 3 consecutive months.Competitive parameters such as relative yield,total relative yield,attack power,and competitive balance index were determined for both plants.Growth parameters including plant height,number of tillers,number of leaves,biomass,and root-shoot ratio were also analyzed.The quality of the lawn was evaluated comprehensively by calculating indexes of density,texture,leaf color,and uniformity,and by determining grass height and biomass.The results showed that:1)The mowing frequency significantly affected the aboveground and underground competition parameters of Z.tenuifolia and I.koenigii(P<0.05).Mowing increased the antagonistic effect of the aboveground parts between the two plants,while the antagonistic effect of the underground parts between the two plants was reduced by mowing 2-3 times per month.2)Mowing frequency and the proportion of I.koenigii had stronger effects on the aboveground parts of Z.tenuifolia than on its underground parts.Mowing once per month improved the aboveground competitiveness of Z.tenuifolia,while mowing twice per month improved its underground competitiveness.The synergistic effect of mowing frequency and increased proportions of I.koenigii increased its attacking power against the Z.tenuifolia root system.3)The mowing frequency and proportion of invasion significantly affected the growth of I.koenigii and Z.tenuifolia.Mowing 1-2 times per month increased the tiller number and leaf number of both plants.Mowing twice per month increased the tiller number and leaf number of Z.tenuifolia increased by about 40%.The biomass of Z.tenuifolia decreased when the proportion of I.koenigii was 10%or more,and the tiller number of Z.tenuifolia decreased when the proportion of I.koenigii was 20%or more.When the proportion of I.koenigii was 30%or more,the plant height of Z.tenuifolia increased but its leaf number decreased.Mowing frequency was the main factor affecting the plant height,tiller number,leaf number,and root-shoot ratio of Z.tenuifolia.The proportion of I.koenigii mainly affected the biomass of single Z.tenuifolia plants.4)Mowing frequency mainly affected the density,height,and biomass of the lawn,but the proportion of I.koenigii mainly affected the texture,leaf color,and uniformity of the lawn(P<0.05).The best combination in terms of the comprehensive quality of the lawn was 10%or less I.koenigii and mowing twice per month.The lawn quality was mainly affected by the mowing frequency,followed by the proportion of I.koenigii.5)Mowing 1-2 times·month-1 significantly increased the aboveground and underground competitiveness of Z.tenuifolia against invading I.koenigii,and promoted tiller formation in Z.tenuifolia,reduced lawn height,and improved the density and texture of the lawn.However,mowing could not change the fact that the aboveground and underground competitiveness of Z.tenuifolia lower than that of I.koenigii.Therefore,the basic requirements for maintaining the quality of a Z.tenuifolia lawn in summer are to control the proportion of I.koenigii at 10%or less and mow twice per month.