杉木人工林土壤微生物对林分密度的响应

Response of soil microorganism to stand density in Cunninghamia lanceolata plantation

[目的] 为研究不同密度杉木Cunninghamia lanceolata人工林土壤微生物对碳源的利用情况及土壤理化性质与微生物多样性的相关关系。 [方法] 运用Biolog微平板技术,对江西大岗山5种不同密度38年生杉木人工林(密度分别为1 667、3 333、5 000、6 667和10 000株·hm-2,造林前3 a抚育,后基本无人工干扰)土壤微生物的功能多样性进行研究,探讨了土壤微生物碳代谢对林分密度的响应及土壤理化性质与微生物碳代谢的关系。 [结果] 在杉木存活密度为2 600~4 600株·hm-2时,反映土壤微生物代谢功能多样性的平均颜色变化率较高。该密度范围下土壤微生物多样性高,适合有机质的分解和养分的转化与积累;不同密度杉木人工林土壤微生物对6种碳源的利用量不同,密度在2 600~4 600株·hm-2时,土壤微生物利用的主要碳源为糖类,其次为羧酸类和氨基酸类,但密度小于或超出这一范围时,土壤微生物对羧酸类的利用大于对糖类的利用;主成分分析结果显示:α-D-乳糖对土壤微生物的利用贡献最大,是杉木人工林中利用最多的物质;相关性分析结果显示:全氮和碱解氮与微生物多样性显著相关(P < 0.05),是微生物利用碳源的决定性因素。 [结论] 综合考虑微生物碳代谢与土壤理化性质,符合杉木人工林可持续发展要求的理想林分密度为2 600株·hm-2。

Objective To provide theoretical basis for the sustainable development of Cunninghamia lanceolata public welfare forest, a study is conducted of the response of soil microbial carbon metabolism to stand density and the relationship between soil physico-chemical properties and microbial carbon metabolism. Method With the Biolog-ECO method employed, five 38-year-old C. lanceolata plantations with various densities were selected in Dagang mountain to study the functional diversity of carbon-source metabolism. Result (1) When the survival density of C. lanceolata was 2 600-4 600 plants·hm-2, the average color change rate (AWCD) which is reflective of the diversity of soil microbial metabolic function was higher and such density range comes with a high soil microbial diversity, which contributes to the soil organic matter decomposition and soil nutrients' transformation and accumulation. (2) The utilization amount of six carbon sources by soil microorganisms varies for C. lanceolata plantations of different densities. When the density was 2 600-4 600 plants·hm-2, the main carbon sources were carbohydrates, followed by carboxylic acids and amino acids. When the density was lower or higher, the soil microorganisms utilized more carboxylic acids than carbohydrates. It is shown in the principal component analysis that α-D-lactose contributed the greatest to the utilization of soil microorganisms and was the most utilized substance in C. lanceolata plantation. It is demonstrated in the correlation analysis that the total nitrogen and alkali-hydrolyzable nitrogen were significantly correlated with microbial diversity, and were the decisive factors for microbial carbon utilization. Conclusion With both the microbial carbon metabolism and soil physico-chemical properties taken into consideration, it was found that the density of 2 600 plants·hm-2 was the most suitable for the sustainable development of C. lanceolata plantation.