施肥当年对科尔沁沙地退化草地不同功能群植物群落特征的影响

Effect of fertilization year on plant community characteristics of different functional groups in degraded grassland in Horqin Sandy Land

为了研究施肥当年不同肥料及组合对退化草地不同功能群植物群落特征的影响,并观察施肥当年的效应,试验以通辽市科尔沁沙地中度退化草地为研究对象,在围栏内设置单施氮肥(N)、单施磷肥(P)、混施氮磷肥(N+P)和混施氮磷钾肥(N+P+K)4种施肥处理,同时以围栏封育为对照(CK处理),2017年6月初施肥,采用小区试验随机区组设计,重复3次。根据样地植物群落组成,把植物划分为一二年生植物、多年生禾本科植物、杂类草、多年生豆科植物4个功能群,其中前3种为浅根系植物,多年生豆科植物为深根系植物,2017年8月下旬(与施肥间隔80 d)对小区内各功能群植物地上现存量、盖度、高度和密度进行调查。结果表明:一二年生植物经N处理后地上现存量增加最多,显著高于CK处理(P<0.05)。与CK处理相比,经N+P处理后盖度增加效果最好(P<0.05);各施肥处理的平均高度均有所增加但未达到显著水平(P>0.05);而植物密度均显著增加(P<0.05),其中经N+P处理的植物密度效果最好。多年生禾本科植物经N+P+K处理后地上现存量和盖度增加最多,显著高于CK处理(P<0.05);与CK处理相比,经N和N+P+K处理后平均高度显著增加(P<0.05);而各施肥处理的植物密度与CK处理相比均差异不显著(P>0.05)。杂类草经N+P+K处理后地上现存量增加最多,经P处理后平均高度和密度增加最多,且均显著高于CK处理(P<0.05);而各施肥处理的盖度与CK处理相比均差异不显著(P>0.05)。多年生豆科植物经N+P和N+P+K处理后地上现存量,以及经N+P+K处理后密度显著低于CK处理(P<0.05)。说明施肥当年不同肥料处理对不同功能群植物群落的影响明显。由于根系深浅的不同,不同功能群植物对肥料的反应也不同。浅根系的一二年生植物对肥料较敏感,深根系的多年生豆科植物由于对肥料吸收有限,并且受竞争关系的影响,肥料的正面效果小。

In order to study the effect of different fertilizers and combinations in the fertilization year on plant community characteristics of different functional groups in degraded grassland,and to observe the effect of the fertilization year,the experiment took the moderately degraded grassland in Horqin Sandy Land,Tongliao City,as the research object.Four fertilization treatments were set in the enclosure:single nitrogen(N),single phosphorus(P),mixed nitrogen and phosphorus(N+P),and mixed nitrogen,phosphorus and potassium(N+P+K);at the same time,enclosure closed planting was used as control(CK)treatment.Fertilization was applied in early June 2017,and the fields were arranged in random blocks;repeat 3 times.According to the composition of the plant community in the plot,the plants were divided into four functional groups:annual and biennial plants,perennial Poaceae plants,broad-leaved herbs,and perennial leguminous plants.Among them,the first three species are shallow root plants,and the perennial legumes are deep root plants.In late August 2017(80 days interval from fertilization),the aboveground stock,coverage,height and density of plants of each functional group in the plot were investigated.The results showed that the aboveground stock of annual and biennial plants increased the most after N treatment,which was significantly higher than that of CK treatment(P<0.05).Compared with CK treatment After N+P treatment,the coverage increase effect was the best(P<0.05).Compared with CK treatment,the average height of each fertilization treatment increased but did not reach a significant level(P>0.05),while the plant density increased significantly(P<0.05),among which N+P treatment had the best effect.The aboveground stock and coverage of perennial Poaceae plants increased the most after N+P+K treatment,which was significantly higher than CK treatment(P<0.05).Compared with CK treatment,the average heights of N and N+P+K treatments were significantly increased(P<0.05),while there was no significant difference in plant density between each fertilization treatment and CK treatment(P>0.05).Broad-leaved herbs with N+P+K treatment had the largest increase in ground stock,and P treatment had the largest increase in average height and density,both of which were significantly higher than CK treatment(P<0.05).There was no significant difference in coverage of all fertilization treatments compared with CK treatment(P>0.05).The aboveground stock of perennial legumes by N+P and N+P+K treatments,and the density by N+P+K treatment were significantly lower than those treated by CK(P<0.05).The results suggested that different fertilization treatments in the fertilization year had significant effect on plant community of different functional groups.Due to the different depths of the root system,different functional groups responded differently to fertilizers.Primary and biennial plants with shallow root system were more sensitive to fertilizer effect,and perennial legumes with deep root system had limited fertilizer absorption and were affected by competition,so the positive effect of fertilizer was small.