草本竞争对白桦、五角枫更新幼苗高生长的影响

Effects of herbaceous competition on high growth of regeneration seedlings of Betula platyphylla and Acer mono

草本竞争在森林更新早期具有显著的生态效应,然而对其发生机理的理论认知仍相当有限.以白桦和五角枫为试验对象进行盆栽控制试验,设置4种竞争方式(无竞争、全竞争、地上竞争、地下竞争)、4种土壤养分梯度(0、8、16、32 g/m^(2))及2种养分分布水平(均、异质),各个处理8次重复,通过测量生物量及苗高、地径、叶片表面积、根系表面积和根长等形态指标,基于线性模型实现草本竞争效应的线性分解,精确衡量各竞争效应组分贡献率的相对重要性,进而基于结构方程模型揭示不同土壤养分状况下草本竞争对幼苗高生长的作用机理.结果显示:草本竞争对不同演替阶段幼苗生长存在显著的抑制作用(P<0.05).地上、地下竞争及二者交互作用贡献率分别处于40%-60%、20%-30%、20%-30%之间.不同土壤养分浓度及养分分布对其贡献率均有显著影响.草本植物分别主要通过影响白桦幼苗的养分吸收能力(0.62)和五角枫幼苗的光合能力(0.74)进而影响其高生长.在高养分浓度或异质土壤养分分布状况下,土壤养分吸收能力较光合能力更为重要.两种不同生态学习性树种的草本竞争效应存在明显差异(P<0.05).本研究表明草本竞争通过作用于白桦和五角枫幼苗的土壤养分吸收能力及光合能力,对更新幼苗高生长产生深远影响,草本竞争效应是维持幼苗高生长的重要生态学机制之一.(图7表8参42)

Herbaceous competition has a significant ecological effect on forest regeneration and is an important limiting factor for the growth stage of regenerated seedlings.However,the theoretical understanding of the mechanism of the herbaceous competitive effect remains limited.In this study,Betula platyphylla and Acer mono were used as experimental objects in a pot experiment.Four types of competition(non-competition,full competition,above-ground competition,and below-ground competition),four soil nutrient gradients(0,8,16,and 32 g/m^(2)),and two nutrient distribution levels(homogeneous and heterogeneity)were set up,and each treatment was repeated eight times.Linear decomposition of the herbaceous competition effect was realized using a linear model.The relative importance of the contribution rate of each competition effect component was accurately measured and the mechanism of herbaceous competition on seedling height growth under different soil nutrient conditions was revealed based on structural equation modeling.The results showed that herbaceous competition inhibited seedling growth at all succession stages(P<0.05).The contribution rates of above-ground competition,underground competition,and their interaction were 40%–60%,20%–30%,and 20%–30%,respectively.Different soil nutrient concentrations and distributions significantly affected the contribution rates.Herbaceous plants mainly affected the nutrient uptake capacity of B.platyphylla seedlings(0.62)and the photosynthetic capability of A.mono seedlings(0.74).This affected their growth.Nutrient uptake capacity was more important than photosynthetic capacity under high concentrations or heterogeneous soil nutrient distributions.The herbaceous competition effects of the two ecological learning tree species differed significantly(P<0.05).The results showed that herbaceous competition and soil nutrients profoundly affected the height growth of regeneration seedlings by affecting soil nutrient uptake and photosynthesis of B.platyphylla and A.mono seedlings.Notably,the mechanism of herbaceous competition on height growth of regeneration seedlings is an important ecological mechanism for maintaining the height growth of seedlings.