Root biomass estimates require species-specific calibration, particularly in palms with distinct below-ground structures. We quantified root distribution and below-ground dry mass in 18 macauba palms (Acrocomia aculeata) aged 3.0–16.4 years and fitted height-based allometric models. Monolith sampling covered three radial classes and seven soil layers to 2.20 m. Total below-ground dry mass ranged from 13.62 to 93.94 kg plant−1 across age means. The 0–20 cm layer contained the largest root fraction in three-year-old palms, whereas 60–100 cm predominated at 5.4 and 12.2–16.4 years. The saxophone stem represented 26.8–44.0% of below-ground dry mass. Height-based models estimated root dry mass and total below-ground dry mass with relative RMSEs of 19.78% and 17.49%, respectively. These findings extend root distribution information to mature macauba and provide complementary estimates for root studies and below-ground biomass inventories within the calibration range.
Plant responses to prior soil conditioning depend on plant identity and soil context, yet how these responses vary among soils with contrasting land-use soil histories remains uncertain. We tested how experimental soil pool, plant conditioning, and gamma irradiation affected plant biomass, foliar chemistry, and microbial gene-copy abundance in soils from an Atlantic Forest–Cerrado ecotone. Two greenhouse experiments used one composite soil pool from each of three land-use histories: primary forest, secondary forest, and long-term pasture. In Experiment 1, soils were conditioned by Cecropia pachystachya, Cedrela fissilis, or Copaifera langsdorffii, and C. fissilis was then used as the phytometer. In Experiment 2, irradiated and non-irradiated soils were conditioned with Urochloa brizantha cv. Piatã before the three native tree species were grown. Biomass, foliar nutrients, and qPCR gene-copy abundances for archaeal and bacterial 16S rRNA and phoD genes and fungal ITS region based on genomic soil DNA were analyzed using factorial models and planned contrasts. In Experiment 1, biomass varied among soil pools and conditioning species, but none of six heterospecific-versus-conspecific conditioning contrasts was significant after multiplicity adjustment. In Experiment 2, U. brizantha biomass was greater in irradiated soil, whereas native-tree responses depended on experimental pool, irradiation, and species; in pasture-derived soil, all three native species produced more biomass in non-irradiated soil. Foliar nutrient profiles showed supported pairwise interactions, while molecular soil microbial results were interpreted cautiously because of persistent non-detections after repeat qPCR assays and influential observations. Plant responses to conditioning and irradiation were context dependent and plant specific. The results support treatment-level differences within the three experimental soil pools but not general land-use effects or microbial causation.
