哈泥泥炭地落叶和常绿两类灌木对氮磷输入增加响应的对比

Comparative study on the response of deciduous and evergreen shrubs to nitrogen and phosphorus input in Hani Peatland of Changbai Mountains

大气氮沉降及磷输入正影响泥炭地的生态过程,而其重要植物成分灌木对氮磷输入如何响应尚鲜有研究。在哈泥泥炭地,通过连续6年的人工氮、磷添加后对3种落叶灌木和3种常绿灌木生长状况进行测定,研究泥炭地两种类型灌木对氮磷输入的响应。落叶灌木(多度和盖度下降,高度上升)与常绿灌木(多度、盖度和重要值下降)对氮输入增加的响应存在差异,对磷输入增加的响应一致。从物种的角度看,存在种间差异,施氮抑制落叶灌木金露梅和笃斯越桔的生长,其多度和盖度均下降,对落叶灌木油桦有促进作用,使其高度、盖度和重要值增加。施氮仅对常绿灌木甸杜产生了影响,降低了其多度和重要值,对常绿灌木小叶杜鹃和狭叶杜香无影响。施磷缓解了部分灌木的养分限制,提高了落叶灌木油桦的盖度、常绿灌木小叶杜鹃的高度和重要值以及常绿灌木甸杜的多度。同时,氮磷对落叶灌木存在交互作用,未施氮肥和低浓度施氮时,施磷对落叶灌木的高度和重要值无影响,在高浓度施氮情况下,施磷使落叶灌木的高度和重要值增加,即氮和磷只有在一定比例下才会促进灌木植物的生长。研究表明,氮磷输入可影响泥炭地灌木间的竞争平衡,使落叶灌木油桦获得生长优势,抑制其他灌木的生长,进而对泥炭地的植被格局产生深远影响。

It is not clear how the shrubs in peatlands respond to nitrogen deposition and phos- phorus input, which could impact ecosystem processes. Our objective was to investigate the effects of different levels of nitrogen and phosphorus addition on three deciduous shrubs and three evergreen shrubs in Hanl Peatland of Changbai Mountains through six years of simulation experl- ment. The responses of deciduous shrubs （with reduced abundance and coverage and increased height） and evergreen shrubs （with reduced abundance, coverage, and importance value） to nitrogen addition were different, while their respo^ases to phosphorus addition was similar. Inter- specific difference existed at species level. Nitrogen addition inhibited the growth of Potentillafru- ticosa and Vaccinium uliginosum, and decreased their abundance and coverage. Meanwhile, ni- trogen addition facilitated the growth of Betula ovalifolia, and height, coverage and importance value increased. Among the evergreen shrubs, nitrogen additiofi only decreased the abundance and importance value of Chamaedaphne calyculata but had no effect on Ledum palustre andR. parvifolium. Phosphorus addition relieved nutrient limitation of these shrubs and increased the coverage of B. ovalifolia, the height and importance value of R. parvifolium and the abundance of C. calyculata. Interactive effects of nitrogen and phosphorus addition were observed for deciduous shrubs. When little or no nitrogen was amended, phosphorus addition had no effects on the height or importance value of deciduous shrubs. Under the condition of high nitrogen addition rate, phosphorus addition increased the height and importance value of deciduous shrubs. This result indicated that only addition of nitrogen and phosphorus at a certain ratio can promote the growth of shrubs. Our study suggests that nitrogen and phosphorus addition can affect shrub performance and change the competitive balance between the two types of shrubs. B. ovalifolia may obtain growth advantage and restrain the growth of other shrubs, which will have a profound impact on vegetation pattern in peatlands.