京北山区人工刺槐水源涵养林主要养分元素含量特征分析

Studies on the nutrient content property of Robinia pseudoacacia water resource protection forest ecosystem in northern mountain area of Beijing

北京北部山区刺槐水源涵养林生态系统的总生物量(包括乔木层、灌木层、草本层和枯落物层)为26 301kg/hm2。刺槐林不同器官中各养分元素的含量差异较大,在叶和枝中各养分元素的含量顺序相同,均是Ca>N>K>Mg>P;在干中的含量顺序是N>Ca>Mg>K>P;根系中的养分元素除Ca随着根系直径的增加呈升高的趋势外,其余的养分元素的含量随着根系直径的增加而降低。刺槐林生态系统5种养分元素的贮存量为514.90 kg/hm2,其中,乔木层中的养分贮存量占总贮存量的85.5%。若以各养分元素在生态系统生物层中的贮存量来计,则Ca的贮存量最大,P的最小,不同养分元素贮存量的顺序为Ca>N>K>Mg>P。

Robinia pseudoacacia is the mainly afforosted tree species in North China ,and is mainly distributed in the gully and hilly areas. The paper studios its forest ecosystem nutrient concentration properties in the northem mountain area of Beijing.Its results show that the total biomass of the forest ecosystem in the .stand is 26 301 kg/hm^2 ,the arboreal layer biomass is 2416.5 kg/hm^2, the shrub layer biomass is 795 kg/hm^2, the herb layer biomass is 442 kg/hm^2, the debris layer biomass is 898 kg/hm^2, respectively. They account for 91.9%, 3.0%, 1.7% ,and 3.4% of the total biomass, respectively. The nutrient elements of nitrogen （N）, phosphorus （P）, potassium （K）, calcium （Ca） and magnesium （Mg） eoneentratiom were analyzed in the different organs of Robinia pseudoacacia forest ecosystem. The five kinds of nutrients in different organs of ahoveground show that the different nutrient elements concentration sequence in leaf and branch are follows： Ca 〉 N 〉 Mg 〉 K〉 P,and in the trunk is follows： N〉 Ca〉 Mg〉 K〉 P.And in the different diameter of the root, the N,P,K,and Mg content show that the concentrations become smaller accomparied with the root diameter increased, but Ca show the reversed trends.The total store is 514.90 kg/hm^2 of the five kinds nutrient elements in the Robinia pseudoacacia forest ecosystem, and the tree layer nutrient element storage amount accouts for about 85.5 percent of total storage. If summing up the total nutrient amount according to the different nutrient element, then the nutrient elements N, P, K, Ca and Mg store in the Robinia pseudoacacia forest ecosystem are 180.12 kg/hm^2, 11.19 kg/hm^2, 39.93 kg/hm^2, 261.31 kg/hm^2 and 22.35 kg/hm^2, respectively. The sequence of nutrient storage of five kinds of nutrient element are as follows： Ca 〉 N 〉 K 〉 Mg 〉 P.