不同蚯蚓采样方法对比研究

蚯蚓种类组成和丰度变化是反映农业管理措施对土壤质量影响的重要指标。为研究利用芥末悬液等方法进行蚯蚓样品采集的有效性和准确性,寻求合理有效的蚯蚓种群特征调查方法,在我国东北玉米连作黑土上分别运用手拣法、福尔马林溶液驱赶法、芥末+水悬液及芥末+乙酸悬液驱赶法,以及驱虫剂与手拣法相结合的方法进行蚯蚓样品采集,将上述7种方法测得的蚯蚓丰度、生物量及年龄组成信息进行了系统分析。结果表明,福尔马林溶液驱赶法不结合手拣法使用时测得的蚯蚓丰度及生物量远远低于其他方法,尤其幼年蚯蚓比例偏低,并不能反映真实的蚯蚓种群特征。使用芥末悬液做驱虫剂有效性明显提高,尤其芥末+乙酸悬液,测得的蚯蚓丰度比手拣法高22.3%。福尔马林溶液结合手拣法后有效性大大提高,测得的蚯蚓丰度和生物量分别是其单独使用时的19.1和9.3倍,但相对其他驱虫剂方法仍高估了成年蚯蚓的比例;芥末+水悬液和芥末+乙酸悬液方法结合手拣法后收集到蚯蚓的数量分别提高了67.8%和89.1%,平均个体重量分别是原来的1.8和1.3倍,说明芥末悬液不会杀死小个体的幼年蚯蚓,但少部分大个体蚯蚓及洞穴不与地表相接的蚯蚓可能并不能被其驱赶至地表,结合手拣法后可以弥补这个缺陷。芥末+乙酸悬液结合手拣法收集到的成年及幼年蚯蚓数量和生物量均显著高于其他方法(P<0.05),既能有效地驱赶小个体和幼年蚯蚓,又可以收集到洞穴不与地表相接的土栖型蚯蚓,因此可以作为真实有效地反映蚯蚓种群特征的采样方法之一。

Comparative study of different earthworm sampling methods

The species composition and abundance of earthworms are important indicators for the impacts of agricultural management on soil quality. In order to develop a proper method for investigating earthworm population in agricultural soils, the effectivity and accuracy of seven sampling methods including: hand-sorting; formalin expulsion; mustard water suspension expulsion; mustard acetic acid suspension expulsion; and the three corresponding chemical expulsions in combination with hand-sorting, were reported in this paper. The experiment was carried out in the Black soils in northeast China under continuous corn cropping with four replicates. The abundance, biomass and age of the earthworm population obtained with these methods were analyzed synthetically. Results showed that the formalin expulsion without hand-sorting yielded the lowest earthworm abundance and biomass relative to other methods, especially for the juveniles, which indicated that this method is not suitable for earthworm population studies. The mustard suspension expulsion, especially mustard acetic acid suspension, was more efficient than formalin solution, which acquired abundance 22.3% higher than hand-sorting. The earthworm abundance and biomass acquired from formalin expulsion combined with hand-sorting were 19.1 and 9.3 times higher than formalin solution without hand-sorting. However, the proportion of adult earthworms was overestimated by this formalin method compared to other expellants methods studied. The hand-sorting combined with mustard water suspension and mustard acetic acid suspension had 67.8% and 89.1% more earthworms individuals collected, respectively, than those chemicals used independently, and the average of individual weight was 1.8 and 1.3 times higher, respectively. The results indicated that unlike formalin solution, mustard suspension was not likely to kill young or small-sized earthworm species. The mustard suspension without hand-sorting was not efficient to collect adult earthworms and the ones without burrows connected to the soil surface. However, these inefficiencies could be corrected with hand-sorting and the mustard suspension application. Earthworm abundance and biomass acquired using mustard acetic acid suspension in combination with hand-sorting were significantly greater than the other methods (P < 0.05). Using this method, we could collect not only the juvenile earthworms efficiently, but also the endogeic earthworms without burrows connected to soil surface. Accordingly, the method of mustard acetic acid suspension in combination with hand-sorting could be used as a better sampling method compared with other sampling methods for investigation of species composition and abundance of earthworms in agricultural soils.