树种之间,有的互助,彼此有利;有的竞争,使一方受害,或两败俱伤。例如,桦木喜光,云杉耐荫,桦木林下种植云杉幼树,既无害桦木,又有利于云杉幼树的更新,两者形式互助关系。以后虽寿命长的云杉更替了生长发育周期短的桦木,但桦木的效益已得到了充分发挥,退出林地理所当然。又如杨树与刺槐混交造林,剌槐根部具根瘤菌,可以固定大气中的游离氮,提高土壤肥力,树皮分泌的一些挥发性物质能阻碍多种草本植物生长;杨树的叶能分解出大量氨基酸,从而有利于两者的生长。据说,樟与茶混交,樟树的分泌物可抑制 Some tree species, some mutual aid and mutual benefit; some competition, so that one victim, or lose both. For example, birch hi light, spruce shade, birch groves planted spruce saplings, both harmless birch, but also conducive to the regeneration of spruce saplings, both forms of mutual assistance. Although long-lived spruce replaced birch growth and development of short cycle, but the benefits of birch has been brought into full play, exit the forest of course. Another example is the poplar and Robiniai afforestation, Rhus spp. Roots Rhizobia, can fix the free nitrogen in the atmosphere, improve soil fertility, some of the bark secretion of volatile substances can hinder the growth of a variety of herbs; poplar leaves can decompose A large number of amino acids, which is conducive to the growth of both. It is said that camphor and tea mixed, camphor tree secretions can be inhibited