Abstract Ecological benefits and production of grassland on the Loess Plateau are limited by low soil N and P availability. Extraneous N and P fertilization is an efficient management measure to enhance grassland productivity and accelerate grassland restoration. However, biodiversity decline and species loss induced by N and P addition must be noticed. Two grassland communities dominated by tall clonal grass (TCG) and tall clonal forb (TCF) on Loess Plateau were selected. A two-year split-plot experiment (main-plot: 0, 25, 50, and 100 kgN ha−1 yr−1; subplot: 0, 20, 40 and 80 kg P2O5 ha−1 yr−1) was conducted to evaluate the effect of N and P addition on aboveground net primary production (ANPP), light availability, diversity and functional group composition. N and P addition slightly increased ANPP mainly benefiting from clonal species and had few effects on species composition and diversity due to the deficient precipitation during growing season in 2017. However, N or P addition alone resulted in significant ANPP increase, and adding N and P together had larger effects in 2018. The changes in ANPP and diversity after P alone addition were driven by legumes. The ANPP responses to 50 and 100 kg N ha−1 yr−1 combined with P addition in 2018 were mainly driven by pronounced increases in tall clonal or annual species. This large shift of species composition caused diversity decline only in TCF community. The extent of diversity decline was significantly correlated with the degree of light availability reduction. Diversity decline in TCF was a result of strong and uniform light availability reduction induced by increased tall annual forb. Tall clonal and annual species are the key functional groups that drive changes in productivity and diversity in the two communities. The optimum N and P amount to tradeoff productivity improvement and diversity decline were 50 kg N ha−1 yr−1 and 20 kg P2O5 ha−1 yr−1 combination for TCG and 25 kg N ha−1 yr−1 and 20 kg P2O5 ha−1 yr−1 combination for TCF.

中文翻译：

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草地生产力和多样性对氮磷添加响应的变化主要取决于半干旱黄土高原的高大无性系和一年生物种

摘要 黄土高原草地的生态效益和生产受到土壤氮磷利用率低的限制。外施氮磷肥是提高草地生产力、加快草地恢复的有效管理措施。然而，必须注意N和P添加引起的生物多样性下降和物种损失。选取了黄土高原上以高克隆草（TCG）和高克隆草（TCF）为主的两个草地群落。进行了为期两年的裂区试验（主区：0、25、50 和 100 kgN ha−1 yr−1；子区：0、20、40 和 80 kg P2O5 ha−1 yr−1）评估 N 和 P 添加对地上净初级生产 (ANPP)、光照可用性、多样性和官能团组成的影响。2017年生长季降水不足，N、P添加略微增加ANPP，主要受益于无性系物种，对物种组成和多样性影响不大。 但单独添加N或P导致ANPP显着增加，添加N和P 2018 年的影响较大。单独添加磷后 ANPP 和多样性的变化是由豆类驱动的。ANPP 对 2018 年 50 和 100 kg N ha-1 yr-1 结合磷添加的响应主要是由高大无性系或一年生物种的显着增加驱动的。这种物种组成的巨大变化仅导致 TCF 群落的多样性下降。多样性下降的程度与可用光减少的程度显着相关。TCF 的多样性下降是由于一年生高粱增加引起的强烈而均匀的光照减少的结果。高大的无性系和一年生物种是推动两个群落生产力和多样性变化的关键功能群。权衡生产力提高和多样性下降的最佳 N 和 P 量是 TCG 的 50 kg N ha-1 yr-1 和 20 kg P2O5 ha-1 yr-1 组合以及 25 kg N ha-1 yr-1 和 20 kg P2O5 的组合TCF 的 ha-1 yr-1 组合。