种植密度对干热河谷桉树人工林土壤养分、酶活性和微生物量的影响OA

This study established 3 planting density treatments—T1(1 050 trees·hm−2),T2(1 200 trees·hm−2),and T3(1 350 trees·hm−2)in Eucalyptus plantations in the dry-hot valley area of Guangxi.It systematically ana-lyzed the changes in soil chemical properties,key hydrolase activities,and microbial biomass along with their stoichiometric characteristics.The results showed that soil pH decreased initially and then increased with increas-ing planting density,reaching the lowest value under T2,while the contents of organic matter,total nitrogen(TN),total phosphorus(TP),alkali-hydrolyzable nitrogen(AN),and available phosphorus(AP)peaked in this treatment.Total potassium(TK)decreased continuously with increasing density,whereas available potassium(AK)showed an opposite trend.The activities of soil β-glucosidase(βG),N-acetyl-β-D-glucosaminidase(NAG),leucine aminopeptidase(LAP),and acid phosphatase(ACP)were highest under T2.Microbial biomass carbon(MBC),ni-trogen(MBN),and phosphorus(MBP)increased continuously with density and reached their maximum values under T3.The microbial C:N ratio was highest in T1,while the microbial C:P and N:P ratios were highest in T2.The organic matter,TN,AN,AP,and AK were significantly positively correlated with enzyme activities and MBC and MBN contents,whereas TK was significantly negatively correlated with βG,LAP,ACP,MBC,MBN,and MBP.The C:N ratio decreased significantly with increases in organic matter,TN,TP,AN,AP,and AK,while the N:P ratio was significantly positively correlated with organic matter,TN,TP,and AP,suggesting that phos-phorus may become a potential limiting factor for microbial growth under high-nitrogen conditions.Planting dens-ity synergistically influences enzyme activities and microbial functions by regulating soil nutrient availability,with the three components exhibiting a tightly interconnected"soil nutrient—enzyme activity—microbial bio-mass"association network Among the treatments,T2 was most favorable for maintaining soil fertility and enhan-cing enzyme activity,while T3 promoted greater microbial biomass accumulation.