哈泥沼泽成炭植物对地表水氮和磷的适应性分析

Adaptation of peat-forming plants to nitrogen and phosphorus of surface water in Hani peatland

明晰泥炭沼泽中的成炭植物对地表水氮磷因子的适应性,对于退化泥炭地的植被恢复,从植物残体中重建过去的环境变化以及预测未来沼泽植物群落组成的变化具有十分重要的意义。2014—2016年生长季调查长白山区的哈泥泥炭地28种成炭植物盖度,测量样方附近地表水中的氮(N)、磷(P)浓度,采用广义加和模型模拟成炭植物的氮磷环境,分析其对地表水氮磷的适应性,并预测氮沉降背景下植物群落组成的变化。结果表明,沼泽地表水氮和磷的浓度具有较大的年际和季节变化。调查的大部分维管束植物盖度最大值对应的氮浓度集中在1~2 mg/L,磷浓度在0.02~0.03 mg/L,丘上的藓类植物所在地表水的氮磷浓度约高于维管植物的1/3。不同物种适应的氮磷环境的最适值有差异,例如,锈色泥炭藓(Sphagnum fuscum)对应氮的最适值为9 mg/L,羊胡子草(Eriophorum vaginatum)和狭叶泥炭藓(S.cuspidatum)对应磷的最适值分别为0.15 mg/L和0.2 mg/L。同时也发现,地表水中氮、磷浓度偏高的物种对应的氮磷的生态幅也比较宽。广义加和模型揭示出大果毛篙豆(Oxycoccus palustris)等成炭植物对氮的适应性呈单调递减,锈色泥炭藓(S.fuscum)呈现单峰模式;狭叶泥炭藓(S.cuspidatum)和羊胡子草(E.vaginatum)对磷的适应呈现单峰模式。根据模型预测结果,在氮沉降继续增加的背景下,研究区油桦(Betula ovalifolia)-苔草(Carex)群落将被金露梅(Potentilla fruticosa)-小叶杜鹃(R.parvifolium)群落取代。

To address adaptation of peat-forming plants in peatlands to nitrogen(N)and phosphorus(P)of surface water factors is of great importance for the vegetation restoration in degraded peatlands,reconstruction of past environmental changes based on plant residues and prediction of changes in the composition of plant communities in peatlands in the context of N deposition.This study investigated the cover of 28 species of peat-forming plants in Hani peatlands of the Changbai Mountains in the growing seasons from 2014 to 2016.The concentrations of N and P in surface water near the plant quadrats were measured.The generalized additive model(GAM)was used to simulate the relationship between N or P of surface water and peat-forming plants,and to predict changes in plant community composition in the context of N deposition.The results showed that there was a great inter-annual and seasonal variation in N and P concentrations in the surface water.When the cover of most surveyed vascular plants was close to maximum,most N concentrations were 1~2 mg/L and most P concentrations at 0.02~0.03 mg/L.The concentrations of N and P for the mosses were slightly higher by 1/3 than those for vascular plants.The optimum values of N and P for each plant varied for different species,such as 9 mg/L of N for Sphagnum fuscum,0.15 mg/L and 0.2 mg/L of P for Eriophorum vaginatum and S.cuspidatum.In addition,the plants with higher N(>2.0 mg/L)or P(>0.03 mg/L)had wider range of N or P concentrations while the species with lower N(<1 mg/L)or P(<0.02 mg/L)had narrower range of N or P concentrations.The generalized additive model(GAM)indicated that 5 species of peat-forming plants,including Oxycoccus palustris,showed a monotonically decreasing response,and S.fuscum a unimodal response to N,while S.cuspidatum and E.vaginatum unimodally adapted to P.GAM predicted that Betula ovalifolia-Carex community in the study area will be replaced by the Potentilla fruticosa-Rhododendron parvifolium community with a context of continuous increases in N deposition in the future.