Why Trees Need Schwammerl

Do trees need the fungus at all or is it a symbiosis that only benefits the sponge? Forstmeister Gerhard Fischer gives the answer and also explains why porcini and egg swabs cannot be grown artificially.树木究竟是否必需这类真菌？抑或是这种共生（symbiosis）关系仅对海绵（sponge）有益？林务专家格哈德·费舍尔（Gerhard Fischer）不仅给出了答案，还阐释了牛肝菌（porcini）与鹅膏菌（egg swabs）为何无法进行人工栽培。