黄土丘陵区草地植被群落优势种叶片功能性状对氮磷添加的响应

以黄土丘陵区草地植被群落3种优势种白羊草、长芒草和达乌里胡枝子为对象,采用裂区试验设计,设置0、50和100 kg N·hm^-2·a^-13个氮处理和0、40和80 kg P₂O₅·hm^-2·a^-1 3个磷处理,于生长旺盛期测定了各植物的叶长、叶宽、比叶面积、叶片干物质含量、叶片氮、磷含量和氮磷比等指标,分析不同优势种叶片功能性状对氮磷添加的响应差异.结果表明:与未施肥相比,50和100 kg N·hm^-2·a^-1处理下白羊草叶长和叶宽分别显著增加35.3%和64.4%,而长芒草仅有叶长显著增加58.8%,达乌里胡枝子仅有叶宽显著增加33.9%,但三者叶片干物质含量分别显著降低10.7%、15.3%和11.2%,白羊草和长芒草叶片氮含量分别显著增加23.0%和99.2%,氮磷比分别显著增加45.8%和96.9%;40和80 kg P₂O₅·hm^-2·a^-1处理下达乌里胡枝子叶长、叶宽和比叶面积分别显著增加56.9%、41.4%和19.6%,叶片干物质含量显著下降14.9%,三者叶片磷含量分别显著增加96.7%、110.9%和238.4%,氮磷比分别显著降低45.8%、42.8%和53.7%.50 kg N·hm^-2·a^-1处理下,与未施磷相比,40和80 kg P₂O₅·hm^-2·a^-1处理后仅达乌里胡枝子叶长和叶宽显著增大,3种植物叶片磷含量显著增加,白羊草和长芒草叶片氮含量显著降低;100 kg N·hm^-2·a^-1处理下,施磷后白羊草和长芒草叶长、达乌里胡枝子叶宽显著增大,三者叶片磷含量显著增加,白羊草叶片氮含量显著降低.综上表明,3个优势种植物叶片功能性状对短期氮磷添加的响应存在明显差异,这些差异与物种属性和施肥水平有关,不同优势种对氮磷添加响应的差异对维持草地群落多样性和稳定性具有重要作用.

Responses of leaf functional traits of dominant plant species in grassland communities to nitrogen and phosphorus addition in loess hilly-gully region.

To analyze plant functional traits of dominant species to nitrogen and phosphorus addition, three species (Bothriochloa ischaemum, Stipa bungeana, and Lespedeza davurica) were selected in the loess hilly-gully region. A split-plot experiment which included three N treatments (0, 50, and 100 kg N·hm^-2·a^-1) and three P treatments (0, 40, and 80 kg P₂O₅·hm^-2·a^-1) was conducted. At the fast-growing stage, leaf length, leaf width, specific leaf area, leaf dry matter content, leaf N content, leaf P content, and leaf N:P were measured. Results showed that under 50 and 100 kg N·hm^-2·a^-1 treatments, leaf length and width of B. ischaemum increased significantly by 35.3% and 64.4%, respectively, while only the leaf length of S. bungeana and the leaf width of L. davurica increased significantly by 58.8% and 33.9%, respectively. Leaf dry matter content of the three species decreased significantly by 10.7%, 15.3% and 11.2%, respectively. Leaf N content and N:P of B. ischaemum and S. bungeana increased significantly by 23.0% and 99.2%, 45.8% and 96.9%, respectively, compared with unfertilized treatments. Under 40 and 80 kg P₂O₅·hm^-2·a^-1 treatments, leaf length, leaf width and specific leaf area of L. davurica increased significantly by 56.9%, 41.4% and 19.6%, respectively, while leaf dry matter content decreased significantly by 14.9%. Leaf P content of three species increased significantly by 96.7%, 110.9% and 238.4%, while the N:P decreased significantly by 45.8%, 42.8% and 53.7%, respectively, compared with those under unfertilized. Under 50 kg N·hm^-2·a^-1 treatment, compared with no P application, leaf length and leaf width of L. davurica and leaf P content of the three species significantly increased, and leaf N content of B. ischaemum and S. bungeana decreased significantly at 40 and 80 kg P₂O₅·hm^-2·a^-1 treatments. Under 100 kg N·hm^-2·a^-1 treatment, leaf length of B. ischaemum and S. bungeana, leaf width of L. davurica and leaf P content of three species significantly increased, while leaf N content of B. ischaemum decreased significantly after P application. In summary, functional traits of dominant species showed significant responses to short-term nitrogen and phosphorus addition, with the different responses were mainly related to species traits and fertilization levels. Such difference reflected plant adaptation to habitat changes. The divergent responses of different species to nitrogen and phosphorus addition played an important role in maintaining diversity and stability of grassland communities.