接种丛枝菌根真菌对模拟大气氮沉降下灌木铁线莲根系形态及养分承载的影响

为了解菌根化处理的灌木铁线莲（Clematis fruticosa）苗木根系形态及养分承载对氮沉降的应激响应，以1年生盆栽灌木铁线莲为对象，分别采用单接种和混合接种，即：单接种根内根孢囊霉（Rhizophagus intraradices，以下简称+R），单接种摩西斗管囊霉（Funneliformis mosseae，以下简称+F）；混合接菌（上述2菌种菌剂按体积1∶1混合，以下简称+RF）的菌根苗。以非菌根苗（未接菌，以下简称-M）为对照。氮沉降处理设置4个梯度（不施氮（0N，0 g·m^-2·a^-1）、低氮（LN，3 g·m^-2·a^-1）、中氮（MN，6 g·m^-2·a^-1）、高氮（HN，9 g·m^-2·a^-1）），1年后测定各处理细根形态（直径≤0.5 mm的总根长、总表面积、总体积、根尖数量）、菌根侵染率、土壤孢子密度及根、茎、叶各器官的养分（碳、氮、磷）含量等指标。①在+R和+RF处理下，LN处理的苗木菌根侵染率和孢子密度达到最大，且LN处理的苗木菌根侵染率显著高于HN处理；而+F处理的苗木菌根侵染率随氮沉降递增无显著差异。②0N处理下，+F和+R处理的灌木铁线莲苗木细根（直径≤0.5 mm）的总根长、总表面积、总体积和根尖数量均显著高于-M处理。然而，+F和+R处理的灌木铁线莲苗木上述根系形态指标随着氮沉降量的增加均呈下降的趋势。③+F和+R处理下，苗木养分承载量随氮沉降量增加呈增加的趋势。氮沉降处理下，接菌处理的苗木碳、氮、磷养分含量显著高于-M处理，其中+F处理下苗木碳氮磷养分含量最高。④直径≤0.5 mm细根形态指标与养分含量指标均呈正相关关系。综上，接菌处理可改变灌木铁线莲苗木细根形态对氮沉降的响应规律，接种摩西斗管囊霉有效增强苗木对氮沉降的适应能力，提高了高氮沉降处理下苗木的养分承载量。

AM Fungi Inoculation on Root Morphology and Nutrient Loading of Clematis fruticosa Seedlings under Simulated Atmospheric Nitrogen Deposition

In order to investigate the stress response of root morphology and nutrient loading of Clematis fruticose mycorrhizal seedlings to nitrogen deposition， 1-year-old C. fruticose mycorrhizal and non-mycorrhizal seedlings（-M） were used as materials. The inoculation treatments included single-inoculation（Rhizophagus intraradices， +R； Funneliformis mosseae， +F）， mixed-inoculation（AMF agents 1∶1 mixture， +RF）. Four nitrogen deposition treatment were set， including no nitrogen（CK， 0 g·m^-2·a^-1）， low nitrogen（LN， 3 g·m^-2·a^-1）， medium nitrogen（MN， 6 g·m^-2·a^-1）， high nitrogen（HN， 9 g·m^-2·a^-1）. The fine root morphology with diameter of ≤0.5 mm（including total root length， total surface area， total volume and tips）， mycorrhizal colonization rate， soil spore density and all parts nutrient loading of a plant（including carbon， nitrogen and phosphorus content） were determined under inoculation and nitrogen deposition treatments. The results indicated that： ①Under +R and +RF treatments， the seedlings mycorrhizal colonization rate and soil spore density were the maximum in LN treatment， and the mycorrhizal colonization rate in LN treatment was significantly higher than that in HN treatment. Under +F treatment， the mycorrhizal colonization rate was no significant difference between the different nitrogen deposition treatments. ②Under 0N treatment， the fine root morphology with diameter of ≤0.5 mm in +F and +R treatments， including total root length， total surface area， total volume and tips， were higher than that in -M treatment respectively. However， the above root morphological indicators of C. fruticose seedlings were decreased with the increase of nitrogen deposition under +F and +R treatment. ③Under +F and +R treatments， the nutrient loading of seedlings increased with the increasing of nitrogen deposition content. The carbon， nitrogen and phosphorus（C，N and P） contents of mycorrhizal seedlings were significantly higher than that of non-mycorrhizal seedlings， and the seedlings C， N and P contents were the maximum under +F treatment. ④There was a positive correlation between fine root morphology with diameter of ≤0.5 mm and nutrient content of seedlings. Thus， inoculation treatment changed the response of fine root morphology of C. fruticose seedlings to nitrogen deposition. The F. mosseae effectively enhanced the seedlings adaptability to nitrogen deposition， and that improved the seedling nutrient loading under high nitrogen deposition.