黄土高原人工林枯落叶对苜蓿的化感效应

Allelopathic Effects of Plantation Defoliations on Medicago sativa in the Loess Plateau

以苜蓿(Medicago sativa)种子为材料,研究了黄土高原13种人工林当年枯落叶经室内混土分解培养后,所获得的枯落叶分解水浸提液对苜蓿的化感效应。结果表明:对苜蓿种子萌发,油松(Pinus tabulaeformis)、樟子松(Pinus sylvestris var.mongolica)、辽东栎(Quercus liaotungensis)、小叶杨(Populus simonii)、白榆(Ulmus pumi-la)、柠条(Caragana microphylla)、沙棘(Hippophae rhamnoides)和紫穗槐(Amorpha fruticosa)落叶水浸液表现为显著抑制作用,而侧柏(Platycladus orientalis)落叶水浸液在中低浓度下表现为显著促进作用;对苜蓿幼苗生长,樟子松、白榆和辽东栎表现为显著抑制作用,侧柏、落叶松(Larix principis-rupprechtii)、小叶杨、刺槐(Robiniapseudoacacia)、旱柳(Salix matsudana)和白桦(Betula platyphylla)在中低浓度下表现为显著促进作用;对苜蓿幼苗CAT活性,油松、樟子松、落叶松、白榆、刺槐和3种灌木表现为显著抑制作用,侧柏(中低浓度)和小叶杨表现为促进作用;对苜蓿幼苗根系活力,紫穗槐表现为显著促进作用,油松、侧柏、落叶松、小叶杨、旱柳和白桦与之相反,樟子松、白榆和刺槐表现为"低促高抑";对苜蓿叶片叶绿素含量,油松、落叶松、侧柏、辽东栎、旱柳和白桦表现为显著促进作用,樟子松、沙棘和紫穗槐高浓度表现为显著抑制作用。综合对苜蓿的化感效应,辽东栎、白榆和紫穗槐整体上表现为较强的抑制作用,侧柏、白桦和旱柳表现为较强的促进作用,樟子松、落叶松、小叶杨、刺槐、油松、柠条和沙棘表现为"低促高抑"。

Defoliations were collected from 13 plantations in the Loess Plateau, mixed with soil separately, and then incubated in laboratory. The allelopathic effects of aqueous solutions extracted from these decom- posed defoliations on Medicago sativa were studied. Results indicated that Pinus tabulaeformis, Pinus sylvestris var. mongolica, Quercus liaotungensis , Populus simonii , Ulmus purnila , Caragana microph yl- la , Hippophae rhamnoides and Amorpha f ruticosa defoliations significantly inhibited M. sativa seed ger- mination, but Platycladus orientalis defoliations （at low and middle concentrations） significantly promo- ted it. P. sylvestris, U. pumila and Q. liaotungensis defoliations significantly inhibited M. sativa seed- ling growth, whereas P. orientalis, Larix principis-rupprechtii, P. simonii, Robinia pseudoacacia, Salix matsudana and Betula platyphylla defoliations （at low and middle concentrations） significantly pro- moted it. Promoting effects decreased as the concentration of extracts increased. P. abulaeformis, P. sylvestris, L. principis-rupprechtii, U. pumila, R. pseudoacacia and three broad-leaved shrubs defolia- tions significantly inhibited the CAT activities of M. sativa seedlings, whereas P. orientalis （at low and middle concentrations） and P. simonii defoliations promoted it. A. fruticosa defoliations significantly im- proved the root vigor of M. sativa seedlings, whereas P. tabulaeformis, P. orientalis, L. principis-rup- prechtii, P. simonii, S. matsudana and B. platyphylla significantly inhibited it. P. sylvestris var.mongolica, U. pumila and R. pseudoacacia promoted it at low concentrations then inhibited it at high concentrations. P. tabulaeformis, L. principis-rupprechtii, P. orientalis, Q. liaotungensis, S. matsu- dana and B. platyphylla significantly promoted chlorophyll content of M. sativa, whereas P. sylvestris var. mongolica, H, rhamnoides and A. fruticosa （at high concentration） significantly inhibited it. Com- prehensive analyses of allelopathic effects indicated that U. pumila, Q. liaotungensis and A. fruticosa o- verall showed strong inhibition, P. orientalis, B. platyphylla and S. matsudana showed strong promo- tion P. sylvestris var. mongolica, L. principis-rupprechtii, P. simonii, R. pseudoacacia, P. tabulae- formis, C. microphylla and H. rhamnoides showed promotion at low concentration then inhibition at high concentration.