高寒地区种植不同种类牧草对土壤节肢动物群落的影响

Effects of different forage species on soil arthropod communities on the Qinghai-Tibetan plateau

为了明确高寒地区种植不同种类牧草对土壤节肢动物群落的影响,于2016年7月,选取2013年建植的垂穗披碱草、老芒麦、早熟禾、羊茅、燕麦、苜蓿6种牧草地为研究样地,以外围天然草地为对照样地,采集0—15 cm混合土样,采用干漏斗法(Tullgren)分离土壤节肢动物。结果表明:(1)7种类型牧草种植地对土壤节肢动物群落组成结构、密度、类群数、Shannon多样性指数和Simpson优势度指数均有显著差异性(P<0.05或0.01)。群落密度、类群数和Shannon多样性指数均表现为燕麦显著高于垂穗披碱草和苜蓿牧草地,而Simpson指数与之相反,其他几种牧草地间土壤节肢动物群落指数均无显著差异性。(2)典范对应分析(CCA)结果表明,影响土壤节肢动物群落组成结构的主要因素是土壤pH、TN、N/P、C/N、AK;其中,在垂穗披碱草样地中土壤节肢动物群落与pH呈正相关,在早熟禾样地中土壤节肢动物群落与TN和N/P呈正相关,而在天然草地中土壤节肢动物群落与C/N和AK呈正相关。(3)回归分析表明,土壤节肢动物群落密度及多样性指数仅与TK含量呈显著正相关(P<0.05或0.01)。研究表明,在青藏高原种植不同种类牧草对土壤节肢动物的群落结构、密度和多样性均存在较大的影响。从长远的观点来看,种植苜蓿等其他种类牧草虽然能缓解草畜矛盾,但会降低土壤节肢动物多样性,不利于生物多样性保护和草地生态系统的可持续利用。

The objective of this study was to examine the effects of different forage species on soil arthropod communities in alpine ecosystems.Six grasslands dominated by six different forage species,viz.,Elymus nutans,Elymus sibiricus,Poa annua,Festuca ovina,Avena sativa,and Medicago sativa,and a natural grassland(NG)were selected for study in July 2016,in Hongyuan county,northwest Sichuan.Two plots measuring 2 m×4 m each were setup in each type of grassland.In the each areas,three sampling points were selected by the diagonal method and mixed soil samples in the 0—15 cm layer were collected.and soil arthropods were extracted from soil samples for 48 h at 38℃using the Tullgren method in the laboratory.(1)There were significant differences in soil arthropod community density,group number,Shannon diversity index and Simpson dominance index among the seven grasslands(P<0.05 or 0.01).The community density,group number and Shannon diversity index showed that Avena sativa were significantly higher than Elymus nutans and Medicago sativa,while the Simpson index was opposite.There was no significant difference in soil arthropod community index among other grassland types.Sex.(2)The results of canonical correspondence analysis(CCA)showed that the composition of soil arthropod community was mainly affected by pH,TN,N/P,C/N,and AK,among other parameters;and the soil arthropod community was positively correlated with pH in Elymus nutans,with TN and N/P in P.annua grassland,and with K in natural grassland.(3)The regression analysis between soil arthropod diversity indexshowed that only total K had a significant positive correlation(P<0.05 or 0.01).The effects of cultivating different forage species on the community structure,abundance,and diversity of soil arthropods varied among the seven grasslands in the Qinghai Tibet Plateau.Clutivating Medicago sativa and some other forage species will reduce the diversity of soil arthropods,and not benefit biodiversity conservation and the sustainable utilization of grassland ecosystems in the long term,although the contradictions between forage and livestock can be alleviated to some extent.We strongly recommend that a comprehensive ecological assessment should be conducted before planting forage species.