林分密度对湿地松根系生物量及其分布的影响

Effects of stand density on the biomass and distribution of roots in Pinus elliottii plantations

为了确定湿地松中龄林的施肥位置和准确估测根系生物量,以湘北11年生5种造林密度湿地松为研究对象,采用全根分层挖掘法,对其根系生物量及其空间分布规律进行了研究。结果表明:湿地松根系发达,单株根系生物量随林分密度的增大而减小,林分根系生物量基本随林分密度的增大而增大。根桩和大根是构成根系的主体,合计占总根量的85.8%-89.4%。不同密度林分根系生物量随土层深度的增加而明显减小,63.1%以上的根系生物量集中分布在0-40 cm土层内,81.4%以上的根系(含根桩)生物量集中分布在距树干0-50 cm范围内,因此应在1/2株行距、20 cm深度的位置施肥最好;根系与树干相关性最大;建立的单株各径级根系生物量估测模型精度较高,可根据林木胸径、树高及林分密度估测根系生物量。

In order to determine the position of the fertilization of middle-aged Pinus elliottii and estimate the root biomass accurately , root biomass and root spatial distribution were investigated using layered total root excavation method in 5 different densities （1 667, 2 000, 2 400, 3 330, and 3 900 trees· hm-2） on 11 year-old P.elliottii plantations in the north Hunan, China.The results showed that the roots of P.elliottii developed well , the root biomass of individual tree decreased , but root biomass of the stand increased with the increase of the P.elliottii density.The rootstock and large-root biomass was up to 85.8%-89.4%of overall.The root biomass of P.elliottii decreased significantly with increased soil depth in plantations .More than 63.1%and 81.4%of the root biomass dis-tributed in soil depths 0-40 cm and 0-50 cm surrounding the trunk, respectively.Fertilization in between rows or/and plants, and soil depth of 20 cm should be optima .The root biomass and trunks was correlation .The results also showed that the mathematic models with fitting accuracy could be used estimate the root biomass by averaged stand breast diameter , averaged height and densities of stand .