杉木×观光木异龄复层混交对林木生长及土壤理化性质的影响

为探究杉木纯林引入观光木转化为异龄复层林后土壤理化性质和土壤养分含量的变化特征,以及驱动土壤肥力变化的主要影响因子,以观光木纯林、杉木纯林和杉木林下套种观光木形成的杉木×观光木异龄复层林为对象,测定了3种林型下林分生长、林地土壤理化性质和养分含量及其化学计量比等指标,分析杉木×观光木异龄复层林林分结构、林木生长和土壤肥力质量特点。结果表明:1)异龄复层林中观光木和杉木的树高、胸径分别为5.3 m、2.52 cm和18.56 m、20.19 cm,显著高于纯林;2)3种林型间土壤物理性质差异显著。异龄复层林相比较纯林,土壤密度降低4.84%~11.94%,土壤孔隙度分别增加10.29%~22.27%,持水量增加8.62%~34.54%,有效改善了土壤孔隙结构和持水状况。3)各层土壤有机质、全N、全P、全K及速效养分与观光木、杉木纯林均差异显著,土壤养分含量随着土层加深而递减。各养分含量分别比杉木、观光木纯林高出7.87%~41.31%、14.32%~53.57%,各层土壤有机质和养分含量由大到小呈现为:异龄复层林、杉木纯林、观光木纯林。4)异龄复层林中C∶N、C∶P平均值分别为16.62、61.46,均低于杉木和观光木纯林,促进了土壤中N、P的有效释放。因此,在异龄复层林中观光木获得更适宜其生长的良好的遮阴环境,2个树种间形成生态位互补,提高了空间和自然资源的利用率,促进了树木生长。异龄复层林能显著提高土壤有机碳和养分含量,且明显高于纯林,在杉木林中套种观光木能加快土壤微生物的转化和矿化作用。

Composition and properties of soil humus in a mixed forest of Cunninghamia lanceolata and Tsoongiodendron odorum

This study was conducted in Xinkou Experimental Forestry Farm of Fujian Agricultural and Forestry University, Sanming, Fujian Province in January 1999. Taking pure stand of Chinese fir as control, the authors measured and studied the content of organic carbon, content of humic acid (HA), ratio of HA to fulvic acid (FA), and the characteristics of infrared light spectrum and visible light spectrum of soil humus in the mixed forest of Chinese fir and Tsoong?tree. Compared to humus composition in the pure stand of Chinese fir, the content of soil organic C, HA content, and the E4 value of HA for different layers of soil, except for the ratio of HA to FA, showed a significant increase in the mixed forest, while the ratios of E4 to E6 had a little decrease. The infrared light spectrum of humic acid had an absorptive peak at 1650 cm-1. It is concluded that the levels of humification and aromaticity of soil humus are higher in the mixed forest, which is favorable for the improvement of soil structure and nutrient supply, thus improving the soil fertility to a certain degree.

Dynamics of nitrogen and phosphorus concentrations of fine roots in a mixed forest of Cunninghamia lanceolata and Tsoongiodendron odorum

From September 1999 to July 2000, N and P concentrations of fine roots were measured with the method of sequential soil core at bimonthly intervals in a mixed forest of Tsoong's tree (Tsoongiodendron odorum Chun) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) in Sanming, Fujian. The results showed that N, P concentration of Chinese fir and Tsoong's tree in fine roots were negatively related to root diameter size. The concentrations of N and P in living roots and dead roots were compared. The order of N concentration in fine roots in different samples was Tsoong's tree>undergrowth>Chinese fir, while that of P was undergrowth>Tsoong's tree>Chinese fir. For Chinese fir, the seasonal change of N, P concentrations in fine roots with various diameter classes showed a single-apex curve with a maximum in September. For Tsoong's tree, maximized concentration of N in fine roots appeared in July or September and maximized P concentration in May.

Effect of Mixed Forests of Chinese Fir and Tsoong's Tree on Soil Properties

An investigation and on 13 year old (1984～1996) Chinese fir and Tsoong's tree mixed forests in Jianou City, Fujian Province, China was carried out to compare the influences of different interplanting types of individual tree tree, row row, row strip (three rows) and pure Chinese fir stands on soil properties. Compared with the pure stands of Chinese fir, the mixed stands exerted a positive effect on soil fertility, with increases in soil organic matter, total N, available P and available K. Moreover, improvements were also observed in soil enzymatic activities, aggregate structure, structure stability, status of soil porosity, soil aeration and penetrability in mixed stands. The row row interplanted stands had the best effect on tree growth and soil properties among these mixed forests. In the southern subtropical region, the spreading of the row row mixing model of the two tree species would be helpful to preventing the soil from fertility deterioration caused by successive plantation of Chinese fir.