子午岭土壤可培养微生物对植被演替的响应

Responses of Cultivable Soil Microorganisms to Vegetation Succession in Ziwuling Area

利用"空间序列代替时间序列"的方法,研究了黄土高原子午岭土壤可培养微生物对植被演替的响应。结果表明:(1)土壤细菌、真菌及微生物总数量按退耕地→草地→灌草地→白桦(Betula platyphylla)林→辽东栎(Quercus wutaishanica)林→辽桦混交林方向递增(p<0.01);放线菌数量呈波动性变化,较高值出现在灌草地和辽东栎林。(2)演替的过程中,土壤微生物综合性指标Shannon—Wiener指数呈波动性变化;真菌数量变化对土壤微生物Shannon—Wiener指数影响较大。(3)随着演替的进行,氨化细菌和硝化细菌数量显著增加(p<0.01);固氮菌数量略有增加,但差异不显著(p>0.05),最大值出现在辽桦混交林;纤维素分解菌数量在辽东栎林和辽桦混交林最高。研究表明,植被演替对土壤微生物3大类群及主要功能群数量影响显著,促进了土壤微生物数量的增加;土壤微生物多样性变化趋势并非总是与植被进展演替方向一致,其大小与植被类型有关,并依植被组成的变化而变化。

An in-depth understanding of the succession mechanism of natural vegetation is critical and badly needed.The responses of cultivable soil microorganisms to the vegetation succession in Ziwuling,the Loess Plateau were investigated with the method of ＂converting spatial series into temporal series＂.The results demonstrate that the gross amount of microbes,bacteria and fungi in the soil increased in lands as the order of abandoned land→grassland→shrub land→Betula platyphylla forest→Quercus liaot.ungensis forest→Quercus wutaishanica—Betula platyphylla forest（FF0.01,p0.01）.The amount of actinomyces fluctuated and relatively higher values were found in shrub land and Q.liaotungensis forest.The Shannon—Wiener value as a comprehensive index of soil microorganisms fluctuated as well,influenced by the variations of fungi population.As the succession progressed,the population sizes of ammonifying and nitrifying bacteria increased significantly（FF0.01,p0.01）.The nitrogen-fixing bacteria increased slightly in general but not significantly（FF0.05,p0.05）,with the largest population in Q.liaotungensis—B.platyphylla forest.Comparatively,the highest numbers of cellulose-decomposing microorganisms were found in Q.liaotungensis forest and Q.liaotungensis—B.platyphylla forest.As indicated,the vegetation succession has significant effects on the variations of the three soil microbial groups tested as well as on the main functional groups,promoting the proliferations of soil microorganisms.The changing of soil microorganism diversity was not always in the same pace as of vegetation succession;vegetation types determined the diversity,which varied with vegetation compositions.