Abstract：
Plants modulate their phosphorus (P) acquisition strategies (i.e., change in root morphology, exudate composition, and mycorrhizal symbiosis) to adapt to varying soil P availability. However, how community- and species-level P-acquisition strategies change in response to nitrogen (N) supply under different P levels remains unclear. To address this research gap, we conducted an 8-year fully factorial field experiment in an alpine grassland on the Qinghai-Tibet Plateau (QTP) combined with a 12-week glasshouse experiment with four treatments (N addition, P addition, combined N and P addition, and control). In the field experiment (community-level), when P availability was low, N addition increased the release of carboxylate from roots and led to a higher percentage of colonisation by arbuscular mycorrhizal fungi (AMF), along with decreased root length, specific root length (SRL), and total root length colonised by AMF. When P availability was higher, N addition resulted in an increase in the plant\'s demand for P, accompanied by an increase in root diameter and phosphatase activity. In the glasshouse experiment (species-level), the P-acquisition strategies of grasses and sedge in response to N addition alone mirrored those observed in the field, exhibiting a reduction in root length, SRL, and total root length colonised, but an increased percentage of AMF colonisation. Forbs responded to N addition alone with increased investment in all P-acquisition strategies, especially increased root biomass and length. P-acquisition strategies showed consistent changes among all species in response to combined N and P addition. Our results suggest that increased carboxylate release and AMF colonisation rate are common P-acquisition strategies of plants in alpine grasslands under N-induced P limitation. The main difference in P-acquisition strategies between forbs and grasses/sedges in response to N addition under low-P conditions was an increase in root biomass and length.
摘要：
植物调节其磷(P)获取策略(即，根形态的变化，渗出物组成，和菌根共生）以适应不同的土壤磷有效性。然而,在不同的磷水平下，群落和物种水平的磷获取策略如何响应氮（N）供应而变化尚不清楚。为了解决这个研究空白，我们在青藏高原（QTP）的高寒草地上进行了为期8年的全因子田间试验，并进行了为期12周的温室实验，并进行了4种处理（N添加，P加法,结合N和P的加法，和控制）。在野外实验（社区水平），当P可用性较低时，添加N会增加根中羧酸盐的释放，并导致丛枝菌根真菌（AMF）定植的百分比更高，随着根长的减少，特定根长（SRL），和AMF定植的总根长度。当P可用性较高时，N的添加导致工厂对P的需求增加，伴随着根直径和磷酸酶活性的增加。在温室实验（物种水平）中，草和莎草的P获取策略仅响应于N的添加，反映了在田间观察到的结果，表现出根长的减少，SRL,和定殖的总根长度，而是AMF定殖的百分比增加。Forbs单独对N加法做出了回应，增加了对所有P收购策略的投资，特别是增加根生物量和长度。P获取策略在所有物种中都显示出一致的变化，以响应N和P的组合添加。我们的结果表明，增加的羧酸盐释放和AMF定殖率是氮诱导的P限制下高山草地植物的常见P获取策略。在低磷条件下，草丛和草/莎草对氮的响应在P获取策略上的主要差异是根生物量和长度的增加。
