施氮磷肥对杉木人工林3种林下植物养分动态及化学计量比的影响

林下植物在人工林生态系统中具有重要生态功能,而其对施肥的响应,尤其是氮(N)磷(P)同施的耦合效应少有研究。以中亚热带典型中龄杉木人工林为对象,布设施N、施P、两者同施和对照4种处理5次重复的野外试验,于施肥第3年的生长季和非生长季收集3种主要林下植物即2种草本地上部分和1种灌木叶片,测定其N、P含量,并计算其化学计量比动态变化。结果表明,施N肥分别提高林下植物狗脊(Cibotium barometz)、芒萁(Dicranopteris dichotoma)、黄瑞木(Adinandra millettii)的N含量18%、25.4%、19.6%;施P肥分别提高狗脊、芒萁、黄瑞木的P含量31.1%、33.9%、11.9%;植物体P含量是驱动N/P化学计量比变化的主因;施N可缩小林下植物养分在生长季与非生长季的差异,而施P增大其养分在生长季与非生长季的差距,但N、P同施对林下植物养分含量在生长季与非生长季的差距无显著影响。综上所述,在P相对缺乏的杉木生态系统,施P肥有利于保障植物N/P化学计量的稳定,有效维持林下植物资源分配平衡。

Effects of Nitrogen and Phosphorus Fertilization on Nutrient Dynamics and Stoichiometric Ratios of Three-Understory Plants in Chinese Fir Plantation

Understory plants have important function in the ecological system. However, the influence of fertilization on the understory,especially the effect of phosphorus (P) input,which alters the influence of nitro?gen ( N) deposition in a forest has seldom reported. A typical Chinese fir plantation was selected as the re?search object in a subtropical forest.Five replications were established on five separate hilly slopes,and four treatments with nitrogen addition,phosphorus addition,both N with P addition and a control plot were randomly arranged within each replication. The leafs of three dominant understory plants were collected including two herbs and one shrub in their growing season and non?growing season 3 years after the field experiment of nitro?gen and andphosphorus addition.The nutrient dynamic change of the understory plant leaves was measured by determining its nutrient content, and the effect of fertilizer on nutrient dynamic was analyzed. The results showed that nitrogen addition increased plant N concentrations,by 18% for Cibotium barometz,25.4% for Di?cranopteris dichotoma and 19.6% for Adinandra millettii.Phosphorus addition increased plant P concentrations, by 31.1% for Cibotium barometz,33. 9% for Dicranopteris dichotoma and 11. 9% for Adinandra millettii. The content of P in plant tissues was the major driver for N∶P alteration.Nitrogen addition decreased the gap of the understory plant leaf nutrient content between the growing season and the non?growing season,phosphorus ad?dition decreased the gap of understory plant leaf nutrient content between the growing season and the non?grow?ing season,while N+P addition had no significantly effect on the gap of understory plant leaf nutrient content between the growing season and the non?growing season. In conclusion,in the ecological system relatively lac?king,P addition P is favourable to the stability of plant N/P ratio,and the control of the resource allocation of understory plants effectively.