【摘要】 以华北落叶松林下枯落物为研究对象,区分未分解、半分解和完全分解的状态,分别配置质量浓度为5.0、12.5、25.0和50.0 g/L的水浸液,设计枯落物分解程度和水浸液浓度的双因素随机区组试验,研究枯落物水浸液对华北落叶松种子萌发与幼苗生长的影响。结果表明:1)华北落叶松纯林半分解和完全分解枯落物水浸液处理下发芽率的化感作用响应指数(I_R)为-0.45～-0.18,发芽指数的I_R值为-0.49～-0.27,多数为中等抑制作用;12.5 g/L的华北落叶松云杉混交林半分解枯落物水浸液处理下,发芽指数的I_R值为-0.62; 50.0 g/L的完全分解枯落物水浸液处理的发芽率和发芽指数的I_R值分别为-0.54和-0.64,抑制作用较强;华北落叶松杨桦混交林的未分解枯落物水浸液处理下,发芽率的I_R值为-0.59～-0.41,发芽指数的I_R值为-0.51～-0.38,为中等及较强的抑制作用。2)华北落叶松纯林半分解和完全分解枯落物抑制幼苗胚轴、胚根和子叶的伸长,抑制作用中等;华北落叶松云杉混交林枯落物水浸液处理下,华北落叶松幼苗生长尤其子叶伸长显著受抑制,50.0 g/L完全分解枯落物处理的子叶长度仅(0.31±0.07) cm,I_R值高达-0.70;华北落叶松杨桦混交林的未分解枯落物水浸液对华北落叶松幼苗生长具中等及较强抑制作用,但抑制作用随枯落物分解程度加深而减弱,半分解和完全分解枯落物水浸液处理对幼苗胚根、子叶及鲜质量抑制作用微弱。3)不同林分枯落物的抑制作用依次为:华北落叶松纯林(I_R均值为-0.12)<华北落叶松云杉林(I_R均值为-0.21)<华北落叶松杨桦林(I_R均值为-0.27)。枯落物水浸液影响华北落叶松林下更新,在枯落物较厚的林地,可适当降低林分密度,以减弱枯落物的影响。更多还原

【Abstract】 [Background]Larix principis-rupprechtii is one of the main tree species in Guandi Mountain.The species is found to be poor regeneration,and the light,temperature and water conditions related to canopy density have been regarded as the main factors. However,litter is another limited factor. In this paper,the effects of litter on the seed germination and seedling growth of the species are studied.[Methods]Litters were collected from 3 types of L. principis-rupprechtii stands in Guandi Mountain,i.e. pure stand,stand mixed with Picea spp.,and stand mixed with Betula spp. and Poplar spp.,in 3 forms of undecomposed,semi-decomposed,and completely decomposed,respectively. Then 50 g of each litter was soaked for 2 d in 1 L distilled water to prepare the aqueous extracts of 5. 0,12. 5,25. 0 and50. 0 g/L,respectively. The 20 seeds were evenly placed in each petri dish and 5 mL aqueous extracts of litter were added. A two factor randomized block experiment was designed to study the effect of aqueous extracts of litter on seed germination and seedling growth of L. principis-rupprechtii. [Results]1) To the pure L. principis-rupprechtii stand,under the treatment of extract from semi-decomposed and completely decomposed litter,the response index( I_R) of the germination percentage was from-0. 45 to-0. 18,and the I_Rof germination index was from-0. 49 to-0. 27,most of them showed moderate inhibitions.In the mixed stand of L. principis-rupprechtii and Picea spp.,the I_Rof germination index was-0. 62 under the treatment of 12. 5 g/L semi-decomposed aqueous extracts,the I_Rof germination percentage and germination index was-0. 54 and-0. 64 under the treatment of 50. 0 g/L completely decomposed,respectively,which showed strong inhibition. As to the stand mixed by L. principis-rupprechtii,Betula spp. and Poplar spp.,the I_Rof the undecomposed litters was from-0. 59 to-0. 41. The I_Rof germination index was from-0. 51 to-0. 38,the inhibition effect was beyond moderate. 2) To the pure L. principis-rupprechtii stand,the elongation of radicle,hypocotyl and cotyledon was all moderately inhibited by the extracts of semi-decomposed and completely decomposed litter. To the mixed stand of L.principis-rupprechtii and Picea spp.,the growth of seedlings,especially the elongation of cotyledons,was significantly inhibited by the extract. The length of cotyledon was only( 0. 31 ± 0. 07) cm and the I_R value was as high as-0. 70 under the treatment of 50. 0 g/L completely decomposed. In the mixed stand composed of L. principis-rupprechtii,Betula spp. and Poplar spp.,the aqueous extracts of undecomposed litter showed moderate and strong inhibition,and the effect was weakened with the deepening of litter decomposition. As a result,the aqueous extracts of semi-decomposed and completely decomposed litter only had weak inhibition on radicle,cotyledon and fresh weight of seedlings was weak. 3) The inhibition order of litter extracts of three stands was,pure L. principis rupprechtii stand( mean I_R=-0. 12) <mixed stand of L. principis-rupprechtii and Picea spp.( mean I_R=-0. 21) < mixed stand composed of L. principis-rupprechtii,Betula spp. and Poplar spp.( mean I_R=-0. 27). [Conclusions] Litter has inhibition effects on the seed germination and seedling growth of L. principis-rupprechtii,and measures to decrease stand density could be taken to lessen the chemical effects of litter.更多还原