模拟氮沉降条件下木荷幼苗光合特性、生物量与C、N、P分配格局
模拟氮沉降条件下木荷幼苗光合特性、生物量与C、N、P分配格局
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DOI：
10.5846/stxb201209101277
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
朱锦懋
中科院分区：
文献类型：
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作者：
王振兴;吴晓燕;黄儒珠;朱锦懋
近几十年来，人类活动通过肥料生产和化石燃料燃烧导致森林生态系统的氮输入增加，这种输入在不久的将来可能会继续。因此，研究氮沉降对植物形态和生理特性的影响日益成为生态环境科学领域的一大热点。为探讨亚热带森林对氮沉降的生理响应，选择木荷作为亚热带森林的重要建设树种。试验采用对照（CK,0 kg N hm-2·a-1）、低氮（LN,50 kg N hm-2·a-1）、中氮（MN,100 kg N hm-2·a-1）和高氮（HN,150 kg N hm-2·a-1） 4个处理。每个月初和月中，施施浓度分别为0 mol N/L（CK）、0.12 mol N/L（LN）、0.24 mol N/L（MN）和0.36 mol N/L（HM）的NH4NO3溶液。在9个月后，研究了1年生的苏木幼苗光合特性、生物量分配、C、N、P分布对不同氮沉降的响应。结果表明：(1)随着供氮量的增加，沙蚕的最大净光合速率（Pnmax）呈先升高后降低的趋势。MN和HN处理后，Pnmax分别增加21.1%（P0.01）和16%（P0.01）。光饱和点（LSP）的变化与Pnmax相似。LN和MN分别使LSP增加了10.6%（P0.01）和13.1%（P0.01）。但HN组的LSP显著低于CK组（P0.01）。不同氮处理下，LN组LCP显著降低（P0.05）， Rd显著降低（LN和MN组P0.01， HN组P0.05）。不同氮素处理对水稻的表观量子产率无显著影响。(2)氮沉降显著提高了沙蚕幼苗的总生物量、叶生物量、茎生物量和根生物量。MN和HN处理分别使总生物量增加168.5%（MN,P0.01）和130.5%（HN,P0.05）。MN处理使根系生物量增加了145.6% （P0.01）。施氮处理使叶片生物量显著增加了247.4%（MN,P0.01）和228.5%（HN,P0.01）。不同氮浓度处理的叶片重比升高，根重比和根冠比降低。(3)施氮增加了土壤氮含量，但降低了土壤磷含量。HN处理下，根、茎、叶中N含量分别增加了44.65%（P0.01）、35.06%（P0.01）和24.78%（P0.05）。随着根、茎、叶氮素供给的增加，碳浓度呈先倾斜后下降的趋势。与对照相比，锰处理显著提高了植株各器官的碳浓度（根、茎、叶分别为P0.01和P0.05）。根系P浓度的变化对LN和MN呈正相关，对HN呈负相关。茎叶中磷含量与氮沉降呈负相关（P0.01）。氮沉降在一定程度上导致了南芥幼苗根、茎、叶中C/N比值的降低和N/P比值的升高。
Human activities have caused increased nitrogen(N) input to forest ecosystems through fertilizer production and fossil fuel combustion in recent decades and this input is likely to continue in the near future.Therefore,studying the effects of N deposition on morphological and physiological characteristics of plants increasingly becomes a major focus in the field of ecological and environmental sciences.To explore physiological response of sub-tropical forest to N deposition,Schima superba was selected as an important constructive species of sub-tropical forest.Four treatments including Control(CK,0 kg N hm-2·a-1),Low N(LN,50 kg N hm-2·a-1),Medium N(MN,100 kg N hm-2·a-1) and High N(HN,150 kg N hm-2·a-1) were conducted in the present study.At the beginning and in the middle of each month,N-treated plots were sprayed with NH4NO3 solution with concentrations of 0 mol N/L(CK),0.12 mol N/L(LN),0.24 mol N/L(MN) and 0.36 mol N/L(HM) respectively.The photosynthetic characteristics,biomass allocation,C,N and P distribution in response to different N deposition were investigated in one-year-old S.superba seedlings after nine months.The results showed that:(1) The trend of maximum net photosynthetic rate(Pnmax) of S.superba was increased firstly,and then decreased with the increase of nitrogen supply.With the treatment of MN and HN,Pnmax increased by 21.1%(P0.01) and 16%(P0.01),respectively.The change of light saturation point(LSP) was similar as the Pnmax.LN and MN caused the increase of LSP by 10.6%(P0.01) and 13.1%(P0.01),respectively.But the LSP in the HN was significantly lower than that in the CK(P0.01).The LCP reduced significantly in LN(P0.05),and Rd reduced significantly under different N treatments(P0.01 for LN and MN;P0.05 for HN).The apparent quantum yield(AQY) were of no significant difference under the different N treatments.(2) N deposition enhanced total biomass,leaf biomass,stem biomass and root biomass of S.superba seedlings significantly.The treatments of MN and HN induced the increase of total biomass by 168.5%(MN,P0.01) and 130.5%(HN,P0.05),respectively.Root biomass increased by 145.6% with MN treatments(P0.01).N treatments caused significant increase of leaf biomass by 247.4%(MN,P0.01) and 228.5%(HN,P0.01).Leaf weight ratio increased while root weight ratio and root to shoot ratio reduced with different concentration of N treatments.(3) N concentrations increased,but P concentrations decreased in soil upon N deposition.Under HN,the N concentrations increased by 44.65%(P0.01),35.06%(P0.01) and 24.78%(P0.05) in roots,stems and leaves respectively.The C concentrations inclined firstly,and then declined with the increase of nitrogen supply in the roots,stems and leaves.Furthermore,C concentrations of different organs increased significantly under MN in comparison with CK(P0.01 for roots and stems,P0.05 for leaves).The change of P concentrations in the roots appeared positively to LN and MN,but negatively to HN.However,P concentrations in the stems and leaves appeared negatively to N deposition(P0.01).To a certain extent,N deposition induced the decrease of C/N ratio and the increase of N/P ratio in the roots,stem and leave of S.superba seedlings.