『Abstract
Although northern temperate forests are generally not considered
phosphorus (P) limited, ecosystem P limitation may occur on highly
weathered or strongly acidic soils where bioavailable inorganic
P is low. In such environments, soil organisms may compensate
by increasing the utilization of organic P via the production
of extracellular enzymes to prevent limitation. In this study,
we experimentally increased available P and/or pH in several acidic
eastern deciduous forests underlain by glaciated and unglaciated
soils in eastern Ohio, USA. We hypothesized that where inorganic
P is low; soil microbes are able to access organic P by increasing
production of phosphatase enzymes, thereby overcoming biogeochemical
P limitations. We measured surface soil for: available P pools,
N mineralization and nitrification rates, total C and N, enzymes
responsible for C, N, and P hydrolysis, and microbial community
composition (PLFA). Increasing surface soil pH a whole unit had
little effect on microbial community composition, but increased
N cycling rates in unglaciated soils. Phosphorus additions suppressed
phosphatase activities over 60％ in the unglaciated soils but were
unchanged in the glaciated soils. All treatments had minimal influence
on microbial biomass, but available pools of P strongly correlated
with microbial composition. Microbes may be dependent on sources
of organic P in some forest ecosystems and from a microbial perspective
soil pH might be less important overall than P availability. Although
our sampling was conducted less than 1 year after treatment initiation,
microbial community composition was strongly influenced by available
P pools and these effects may be greater than short-term increases
in soil pH.
Keywords: Enzyme activity; Lime fertilization; Phosphorus fertilization;
PLFA; Temperate forests』
Introduction
Materials and methods
Study sites
Experimental design
Soil chemistry and nutrients
Extracellular enzyme activity
Phospholipid fatty acid analysis
Data analysis and statistics
Results
Physiographic regions
Soil properties
Microbial community
Discussion
Microbial response to elevated P
Response to elevated pH
Soil pH and N cycling
Conclusions
Acknowledgments
References