Soil carbon and nutrients change with pine invasion into eucalypt forests

VIETORISZ, CORINNE; VILGALYS, RYTAS; ROJAS, J. ALEJANDRO; CHEN, KO-HSUAN; LIAO, HUI-LING; HOEKSEMA, JASON D.; POLICELLI, NAHUEL; PLETT, JONATHAN M; CARNEGIE, ANGUS; BISSET, ANDREW; BHATNAGAR, JENNIFER M.

New Orleans, LA

Congreso; American Geophysical Union (AGU) meeting 2021; 2021

AGU

The co-invasion of pine trees (Pinus spp.) and their associated mycorrhizal fungi into thesouthern hemisphere is one of the most widespread invasions of non-native species on Earth.However, little is known about how pine invasions affect soil carbon (C) and nutrient content,particularly when invading into eucalypt forests. Pine invasions may impact the soil C, nitrogen(N), and phosphorus (P) of native eucalypt forests in several ways: pine root symbionts may mineincreased amounts of N and P from the soil, soil C may be lost via soil disturbance, and/or C, N,and P could become ?locked? in a growing needle litter layer that decomposes slower thaneucalypt litter. Thus, we hypothesized that pine invasions would lower total soil C, N, and Prelative to uninvaded eucalypt forests. To test this hypothesis, we compared soil C, N, and Pconcentrations and soil fungal communities across pine invasion fronts in six Australian states.We measured total C, total N, and bulk P on soils from sites containing three forest types:uninvaded native Eucalyptus forest, pine-invaded Eucalyptus forest, and non-native pineplantation. We then tested for a relationship between soil C, N, P, C:N, and C:P ratios and foresttype. In support of our hypothesis, soils from pine-invaded eucalypt forests had significantlylower total N and P content than uninvaded eucalypt forests and non-native pine plantations.Additionally, soils from pine-invaded eucalypt forests and uninvaded eucalypt forests hadsignificantly lower total C than non-native pine plantations. Soil C:N and C:P were significantlyhigher in invaded eucalypt forests relative to uninvaded forests. These findings indicate thateither 1) pine invasions are changing soil systems to reduce the total N and P of native eucalyptforest soils as the invasion progresses, or 2) pines are preferentially invading eucalypt forestswith low soil nutrient content. Lower soil N and P relative to soil C under pine invasions suggeststhat pines and their associated root microbiome may be able to mine soil N and P, and/or that Nand P may become locked in a slow-decomposing needle litter layer. To further understand therole that soil fungal communities play in these soil nutrient dynamics, we are currently analyzinghow the soil fungal communities are related to forest type and soil C, N, and P.