高寒藏嵩草(Kobresia tibetica)草甸植物对土壤氮素利用的多元化特征

论文以藏嵩草草甸为研究对象，利用¹⁵N 同位素标记技术，野外原位定量研究高寒藏嵩草草甸7 个主要植物种对土壤有机氮（甘氨酸）和无机氮（铵态氮、硝态氮）的吸收，以证明不同植物对土壤氮素吸收的生态位分化特征。结果表明：① 高寒藏嵩草草甸7 种植物δ¹⁵N天然丰度值为0.840‰～5.015‰，变异范围为4.175‰，地上组织氮浓度为14.38～23.31g·kg^-1；② 从7 种植物吸收土壤甘氨酸、铵态氮和硝态氮的比例看，草地早熟禾偏好吸收土壤有机态氮，其体内氮的36%来源于土壤甘氨酸。冷地早熟禾和雅毛茛吸收土壤无机氮的能力最强，其体内氮的41%～43%来源于铵态氮。溚草偏好吸收土壤硝态氮，其体内氮的35%来自于硝态氮。③ 优势植物藏嵩草、华扁穗草和黑褐苔草对¹⁵N-Gly、¹⁵N-NO₃^-和¹⁵N-NH₄⁺的吸收均较低，仅为0.085～0.475 μmol ¹⁵N·g^-1 DW，表明这3 种莎草科植物不能有效吸收土壤中的甘氨酸和无机氮源。④ 高寒沼泽湿地生态系统中，不同植物种对土壤氮素的吸收存在差异和多元化的特点，其中莎草科植物对土壤氮的利用较低，而早熟禾、溚草禾本科牧草及双子叶植物雅毛茛以土壤无机氮和可溶性有机氮作为氮源。

The Uptake Strategy of Soil Nitrogen Nutrients by Different Plant Species in Alpine Kobresia tibetica Meadow on the Qinghai-Tibet Plateau

Using ¹⁵N tracer technique, we quantify the uptake of soil organic N (glycine) and inorganic N (ammonium N, nitrate N) by diffeerent plant species in the Kobresia tibetica alpine meadow in situ. and examine the extent of niche separation in N source uptake by different plant species in alpine communities. Six treatment sampling plots were randomly set in alpine. We had three types of ¹⁵N labeled chemicals including ¹⁵NH₄Cl, K¹⁵NO₃ and ¹⁵N labeled glycine (abundance of 98%). The ¹⁵N concentration of all the chemicals was the same at 11 mmol ·L^-1. The six sampling plots all contained two reduplications and each replication was set as 96 cm × 96 cm and at 2 m intervals. The results show: 1) δ¹⁵N natural abundance values of seven plant species lie between 0.840‰ and 5.015‰, and the scope is 4.175‰. The N concentrations of seven plant species lie between 14.38－23.31 g·kg^-1. 2) As far as the plant uptake of organic N (glycine) is concerned, Poa pretensi can effectively uptake organic nitrogen, and about 36% of the nitrogen of these species comes from soil organic nitrogen sources. Poa crymophila and Ranunculus pulchellus can effectively uptake ammonium, and 41%-43% of its nitrogen comes from soil ammonium. Koeleria cristata can effectively absorb nitrate in comparason to other plant species in the meadow, and about 35% of the nitrogen in this plant comes from soil nitrate. 3) The dominant sedge plant species Kobresia tibetica, Blysmus sinocompressus and Carex atrofusca uptake low amounts of ¹⁵N labeled ammonium, nitrate and glycine in soil. The uptake scope is just at 0.085-0.4750 μmol ¹⁵N·g^-1 DW. This suggested that the sedges cannot use effectively soil organic nitrogen sources at experimental period. 4) These data show the plant species have diverse ways to uptake soil nitrogen in alpine swomp meadows. Two grasses such Poa spp. and dicotyledons such as Ranunculus pulchellus may effectively utilize soil N sources including dissolved organic nitrogen such as amino acids.