Nitrogen transformations and microbial biomass in soils associated with Chinese and hybrid chestnut trees

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Alana, R Reynolds, Environmental Science, Robert Morris University, Moon Twp, PA, Michael, C Gasdick and Carsen, L Bathke, Biology, Robert Morris University, Moon Twp, PA, William J. Dress, Biology, Robert Morris University, Moon Twp., PA

Background/Question/Methods
The American chestnut (Castanea dentata) was a dominant component of Eastern deciduous forests prior to the introduction of Cryphonectria parasitica, the causative agent of the chestnut blight. Over the past decade, hybrid American/Chinese chestnuts have been planted to reintroduce a blight resistant chestnut tree within its former range. It is well established that individual tree species can impact soil biogeochemical cycling and microbial communities. The goal of this study is to compare nitrogen transformations and microbial communities in soils under Chinese and hybrid chestnut trees. Chinese and hybrid chestnut trees were planted in a 2 hectare reintroduction plot within the Sewickley Heights Borough Park between 2012 and 2014. In August 2019, soils were collected at the base of 8 Chinese chestnut trees and 8 hybrid chestnut trees within the reintroduction plot. Control samples were collected from 8 sites in the contiguous forested area adjacent to the reintroduction plot. Samples were analyzed for organic matter, nitrogen mineralization and nitrification, soil microbial biomass and microbial composition.
Results/Conclusions
Overall, there was no significant difference in organic matter and soil pH among hybrid chestnut, Chinese chestnut and control soils. Extractable PO4was significantly lower in control soils (1.6 mg PO4/kg soil) compared to hybrid chestnut soils (3.7 mg PO4/kg soil) and Chinese chestnut soils (5.3 mg PO4/kg soil). Similarly, there was significantly lower extractable NH4 and NO3 in control soils (11.7 mg NH4 /kg soil and 24.1 mg NO3 /kg soil) compared to both hybrid chestnut soils (13.8 mg NH4 /kg soil and 33.1 mg NO3 /kg soil) and Chinese chestnut soils (16.7 mg NH4 /kg soil and 32.0 mg NO3 /kg soil). There was no significant difference in extractable nutrients between the hybrid and Chinese chestnut soils. In contrast with extractable nutrients, potential nitrogen mineralization rate was significantly greater in control soils (88.3 mg NH4/kg soil/30 days) compared to hybrid chestnut soils (61.5 mg NH4/kg soil/30 days) and Chinese chestnut soils (66.2 mg NH4/kg soil/30 days). Overall, the preliminary results indicate that reintroduced chestnut trees may impact soil biogeochemical cycling.