半干旱区杨树-沙棘混交林杨树的养分特征

Nutrient Characteristics of Poplar in Poplar-Seabuckthorn Mixed Forest in Semi-Arid Area

为进一步阐明半干旱地区杨树-沙棘混交促进杨树生长的机理,以辽西地区杨树-沙棘混交林为研究对象,用杨树纯林为对照,研究杨树叶片、凋落物和土壤碳(C)、氮(N)、磷(P)化学计量特征及再吸收效率,并对能提高树木抗旱性的重要养分钙(Ca)的吸收进行了研究。结果表明:杨树在纯林和混交林中叶片N∶P分别为21.14和22.03,均大于16,表明杨树生长受到磷限制,混交未改变P对杨树的限制作用;混交林与纯林相比,杨树叶片C∶N和C∶P分别极显著低34.94%和32.82%,杨树叶片枯落物C∶N显著低40.16%,C∶P显著低41%;混交林中杨树叶片N和P的再吸收效率低于纯林,N再吸收效率较纯林低12.53%、P再吸收效率较纯林低22.08%;混交林土壤N和P含量比纯林分别显著提高27.54%和47.83%,但混交林土壤C∶N、C∶P和N∶P与纯林土壤无显著差异;混交林杨树叶片钙浓度显著高于纯林。杨树与沙棘混交后,虽然杨树仍受P限制,但是杨树在混交林中有更高比例的养分进入到养分循环,且凋落物的分解速率更快,土壤养分含量也更高,使杨树获得更多的养分供应,提高杨树生产力。同时,混交林提高了杨树Ca的吸收,使其在干旱环境下获得生长优势。

To explore the mechanism of growth promotion of poplar in poplar-seabuckthorn mixed forest,we studied poplar seabuckthorn mixed forest and poplar pure forest was taken as control in western Liaoning Province.The concentrations of C,N and P,stoichiometry and nutrient resorption efficiency of poplar leaves、litters and soil were analyzed.The absorption of calcium,an important nutrient for improving drought resistance of poplar was studied also.The results showed that Poplar foliar N∶P in pure forest and mixed forest were 21.14 and 22.03 respectively,both N∶P ratios were higher than 16,indicating that the limiting effect of P on poplar was not changed by mixing.In mixed forest,foliar C∶N and C∶P were significantly lower by 34.94%and 32.82%respectively,litter C∶N and C∶P were significantly lower by 40.16%and 41%respectively than pure forest.The N and P nutrient resorption efficiency of poplar leaves were 12.53%and 22.08%lower than that in pure forest respectively.Soil N and P of mixed forest were 27.54%and 47.83%higher than that of pure forest,respectively,but there was no significant differences in soil C∶N、C∶P and N∶P between mixed forest and pure forest.Foliar Ca concentration in mixed forest was significantly higher than pure forest.In poplar-seabuckthorn mixed forest,although the poplar was still limited by P,a higher proportion of nutrients entered the nutrient cycle in the mixed forest,and the decomposition rate of litter was faster,and the soil nutrient content was higher,which made more nutrient absorption and improved the poplar productivity. At the same time, the mixed forest increased the calcium absorption of poplar, which made it gain growth advantage in arid environment.