摘要
Rapid spread and growth of plants that are poisonous to animals produce large amounts of plant litter in degraded grasslands.Nitrogen(N)input may promote the growth of these poisonous plants and alter the rhizosphere microbes and arbuscular mycorrhizal fungi(AMF)in particular.However,it is unclear how poisonous plant litter affects the growth of palatable plants and their associated AMF in the rhizosphere and whether and how N deposition may mediate these effects.A greenhouse experiment was performed to test the combined effects of litter addition of a poisonous plant,Stellera chamaejasme,and N addition on the growth of a dominant grass,Leymus chinensis,AMF characteristics and soil properties.Litter addition significantly increased the ramet number and aboveground biomass of L.chinensis and soil available phosphorus(AP)concentration and decreased the spore density of AMF.However,the interaction of both treatments had no significant effects on traits of L.chinensis and AMF properties.Stellera chamaejasme liter positively affected L.chinensis by increasing AP and negatively affected AMF by combining balanced changes in soil nutrients and litter-induced allelopathic compositions.High N addition may alleviate soil N limitation and inhibit litter decomposition,thus overriding the litter's effects on L.chinensis and AMF.These findings imply that it is necessary to objectively and comprehensively evaluate the ecological functions of poisonous plants beyond their harmful effects on livestock.Simultaneously,N deposition should be an indispensable factor in predicting the relationships between poisonous plants and edible plants indegraded grasslands.
退化草地上迅速蔓延、生长的有毒植物能产生大量的调落物,而氮输入能促进有毒植物的生长,并改变其根际微生物特别是丛枝菌根真菌(AMF)的特征。然而,有毒植物的调落物如何影响可食牧草的生长及其根际AMF,N沉降是否以及如何介导这些影响,目前尚不清楚。本文在中国东北的草甸草原上进行了温室实验以检验添加狼毒(Stellera chamaejasme)调落物和氮素对优势植物羊草(Leymus chinensis)的生长、AMF和土壤特征的影响。结果表明,添加调落物显著增加了羊草分株数、地上生物量和土壤速效磷(AP)浓度,并降低了AMF孢子密度。然而,调落物与氮素的交互作用并未显著影响羊草和AMF。狼毒调落物通过提高AP对羊草产生正效应,并结合土壤养分平衡与调落物诱导的化感成分的变化对AMF产生负效应。另外,高氮添加能缓解土壤的氮限制并抑制调落物分解,从而减缓调落物对羊草和AMF的影响。上述结果表明,除了关注有毒植物对家畜的有害作用外,还应客观地、全面地评价有毒植物的生态功能:同时,氮沉降应作为预测退化草地有毒植物与可食植物的种间关系的一项重要指标。
基金
National Natural Science Foundation of China(31570452,31670524).
