Riparian reforestation: are there changes in soil carbon and soil microbial communities?
Reforestation of pastures in riparian zones has the potential to decrease nutrient runoff into waterways, provide both terrestrial and aquatic habitat, and help mitigate climate change by sequestering carbon (C). Soil microbes can play an important role in the soil C cycle, but are rarely investigated in studies on C sequestration. We surveyed a chronosequence (0-23years) of mixed-species plantings in riparian zones to investigate belowground (chemical and biological) responses to reforestation. For each planting, an adjacent pasture was surveyed to account for differences in soil type and land-use history among plantings. Two remnant woodlands were included in the survey as indicators of future potential of plantings. Both remnant woodlands had significantly higher soil organic C (SOC) content compared with their adjacent pastures. However, there was no clear trend in SOC content among plantings with time since reforestation. The substantial variability in SOC sequestration among plantings was possibly driven by differences in soil moisture among plantings and the inherent variability of SOC content among reference pastures adjacent to plantings. Soil microbial phospholipid fatty acids (PLFA, an indicator of microbial biomass) and activities of decomposition enzymes (β-glucosidase and polyphenol oxidase) did not show a clear trend with increasing planting age. Despite this, there were positive correlations between total SOC concentration and microbial indicators (total PLFA, fungal PLFA, bacterial PLFA and activities of decomposition enzymes) across all sites. The soil microbial community compositions (explored using PLFA markers) of older plantings were similar to those of remnant woodlands. There was a positive correlation between the soil carbon:nitrogen (C:N) and fungal:bacterial (F:B) ratios. These data indicate that in order to maximise SOC sequestration, we need to take into account not only C inputs, but the microbial processes that regulate SOC cycling as well.
The Waite Research Institute and The School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, PMB1 Glen Osmond, SA 5064, Australia; School of Biological Sciences, Monash University, Clayton, VIC 3800, Australia. Electronic address: jessica.mackay@adelaide.edu.au.
J E
JE
Mackay
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia; Institute for Applied Ecology, University of Canberra, Bruce, ACT 2617, Australia.
S C
SC
Cunningham
The Waite Research Institute and The School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, PMB1 Glen Osmond, SA 5064, Australia.
T R
TR
Cavagnaro
D002244:Carbon / Q000032:analysis; D003247:Conservation of Natural Resources; D016468:Forestry; D065928:Forests; D009584:Nitrogen / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014739:Victoria
D012987:Soil; D002244:Carbon; D009584:Nitrogen
C sequestration; Fungi to bacteria ratio; Phospholipid fatty acids (PLFA); Soil ecology