尾巨桉与红锥混交对林下植被和土壤性质的影响

Effects of Mixing Eucalyptus urophylla×E.grandis with Castanopsis hystrix on Understory Vegetation and Soil Properties

以尾巨桉(Eucalyptus urophylla×E.grandis)纯林(PEU)、红锥(Castanopsis hystrix)纯林(PCH)和尾巨桉-红锥混交林(MEC)为研究对象,探究在生态营林方式下尾巨桉与红锥混交对林下物种多样性、生物量、土壤理化性质的影响及其关联性。结果表明,(1)MEC林下植被群落的物种丰富度显著高于两种纯林,MEC和PEU灌木层的物种丰富度显著高于PCH,而MEC和PCH草本层的物种丰富度显著高于PEU;MEC显著提高灌木层的Shannon-Wiener指数和Simpson指数。(2)PEU显著提高灌木层的地上生物量,显著降低草本层生物量;PCH降低灌木层生物量,增加草本层生物量;而MEC则能在较高水平上维持灌草生物量和地上地下生物量的相对平衡。(3)MEC 0—20、20—40、40—60、60—80、80—100 cm土层的pH均显著高于两种纯林;PEU 5个土层的土壤容重均高于MEC和PCH,且0—20 cm土层达到显著差异;MEC和PCH各层次的土壤有机碳均显著高于PEU;除个别土层(60—80 cm)外,MEC和PEU各土层的全氮、全钾均显著高于PCH,3种林分各土层土壤全磷差异不显著。(4)影响林下植物群落物种多样性的主控因子为灌木层地下生物量(SBB)、草本层地上生物量(HAB)、乔木层地上生物量(TAB)、土壤全氮(TN)、土壤碳氮比(C꞉N)、土壤氮磷比(N꞉P)和pH;其中,TAB、SBB、TN、pH、N꞉P与PEU和MEC林下植物群落、灌木层的物种丰富度呈显著正相关,HAB、C꞉N与PCH草本层物种丰富度呈显著正相关。综上所述,尾巨桉与红锥混交能显著提高林下物种多样性,维持灌草生物量平衡,改良土壤质量,有效提升混交树种和混交林分的生长量和生物量,是一种较好的发展模式。

The effects of mixing E.urophylla×E.grandis with C.hystrix on understory species diversity,biomass,soil physicochemical properties and their correlations were studied in pure E.urophylla×E.grandis plantations(PEU),pure C.hystrix plantations(PCH)and mixed E.urophylla×E.grandis and C.hystrix plantations(MEC)under eco-silviculture regime.The results showed that(1)the understory species richness of MEC was significantly higher than that of the two pure forests.The species richness in shrub layer of MEC and PEU was significantly higher than that of PCH,while the species richness in herb layer of MEC and PCH was significantly higher than that of PEU.MEC significantly increased Shannon-Wiener index and Simpson index of the shrub layer.(2)The shrub aboveground biomass was significantly increased in PEU,while herb biomass was significantly decreased in PEU.The biomass of shrub layer was decreased and biomass of herb layer was increased in PCH.In addition,the relative balance of shrub and herb biomass and aboveground and underground biomass can be maintained at a high level in MEC.(3)The pH values of MEC in 0-20,20-40,40-60,60-80 and 80-100 cm soil layer were significantly higher than that of the two pure forests.The soil bulk density of five soil layers in PEU was higher than that in MEC and PCH,and the significant difference was observed in 0-20 cm soil layer.The soil organic carbon of MEC and PCH was significantly higher than that of PEU.Except for some soil layers(60-80 cm),the total nitrogen and total potassium in MEC and PEU soil layers were significantly higher than those in PCH,but there was no significant difference in soil total phosphorus in all soil layers of the three stands.(4)The main factors affecting the species diversity of understory plant community were shrub belowground biomass(SBB),herb aboveground biomass(HAB),tree aboveground biomass(TAB),total nitrogen(TN),C/N ratio,N/P ratio and pH.Among them,TAB,SBB,TN,pH and N꞉P were significantly positively correlated with the species richness in understory plant community and shrub layer of PEU and MEC,while HAB,C꞉N were significantly positively correlated with the species richness in herb layer of PCH.In conclusion,mixing E.urophylla×E.grandis with C.hystrix can significantly improve understory species diversity,maintain shrub and herb biomass balance,improve soil quality,and effectively increase the growth and biomass both at tree species and stands level.Consequently,we recommend the promotion and application of mixed E.urophylla×E.grandis and C.hystrix plantations in the southern Subtropical region.