西南亚高山针叶林主要树种互作及增温对根区土壤微生物群落的影响

Effects of plant interspecific interaction and warming on soil microbial community in root zone soil of two dominant tree species in the subalpine coniferous forest in southwestern China

温度与植物种类是生态系统土壤微生物群落组成与结构的重要影响因子。气候变暖背景下,不同树种及树种互作对土壤微生物群落产生的影响仍不清楚。该文以西南亚高山针叶林主要建群种粗枝云杉(Piceaasperata)和岷江冷杉(Abies faxoniana)为研究对象,采用红外加热器模拟增温,通过不同种植方式(云杉、冷杉单种和二者混种,以及裸地对照),研究不同物种及增温对土壤微生物磷脂脂肪酸(PLFAs)含量与群落结构的影响。结果表明:(1)无论增温与否,与裸地相比,云杉与冷杉单种均显著增加了土壤微生物群落主要类群及总PLFAs含量,而混种仅在非增温条件下增加了微生物群落PLFAs含量;另一方面,增温显著促进了裸地真菌(F)和云杉根区革兰氏阴性菌(GN)的生长,但对冷杉与冷杉-云杉混种小区微生物群落具有显著的抑制作用。(2)主成分分析(PCA)表明,非增温条件下,植物种植对土壤微生物群落组成的影响更为明显。非增温情况下云杉、冷杉单种和混种均对微生物群落结构有显著影响,显著降低了土壤革兰氏阳性菌/阴性菌(GP/GN),增加了土壤真菌细菌比(F/B)(64.29%–35.71%),而增温时,仅冷杉单种对GP/GN和F/B有显著影响。(3)PLFAs含量与土壤碳含量显著正相关,微生物群落结构(F/B)则与土壤pH及无机氮含量有显著相关关系。以上结果说明,在非增温情况下,无论单种还是混种均有利于土壤微生物生长,但在增温情况下混种对微生物群落PLFAs含量无显著影响,两个物种对微生物群落结构的影响在增温条件下也有减弱的趋势。

Aims Soil microbial community composition and structure were regulated by temperature and plant species.Picea asperata and Abies faxoniana were planted in the monoculture and mixture plantations of the subalpine region in southwestern China.However,the effects of these two species and their interactions on soil microbial community under future climate warming remain unclear.Methods An experiment was conducted to examine the effects of warming and plant species on soil microbial community composition with two levels of temperature(unwarming and warming with infrared heater)and four planting patterns(single A.faxoniana,single P.asperata,mixture of A.faxoniana and P.asperata,and unplanted bare land).Root zone soil of different planting treatments were sampled to estimating the microbial biomass and microbial community composition by the phospholipid fatty acids(PLFAs)content analysis.Important findings The results indicated that:(1)Both P.asperata and A.faxoniana mono-planting significantly increased the biomass(PLFAs content)of main soil microbial groups and the whole community,regardless of warming,but the PLFAs content was only increased by mixed planting in unwarming plots.On the other hand,warming enhanced fungi(F)in unplanted plots and gram-negative bacteria(GN)in the P.asperata plots,respectively.However,warming significantly decreased soil microbial biomass in A.faxoniana and the mixed planting plots.(2)Principal component analysis(PCA)showed that effects of planting P.asperata and A.faxoniana on soil microbial community composition were greater under unwarming than under warming conditions.All the planting treatments significantly decreased the ratio of gram-positive/gram-negative bacteria(GP/GN)and increased the ratio of fungi/bacteria(F/B)in unwarming plots.However,significant effects on GP/GN and F/B ratios were only observed in A.faxoniana plots under warming condition.(3)PLFAs content was positively correlated with soil organic carbon,and F/B ratio was significantly correlated with soil pH and inorganic N.These results showed that the effects of warming on soil microbial biomass and composition varied among the tree species,and the effects of P.asperata and A.faxoniana were weakened under warming condition than under unwarming condition.Our results provide a vital theoretical basis for further study on the responses of soil microbial communities to vegetation and global climate change in southwestern China.