@article {BF-2926,
	title = {Ecosystem Respiration in a Seasonally Snow-Covered Subalpine Grassland},
	journal = {Arctic, Antarctic, and Alpine Research},
	volume = {43},
	year = {2011},
	month = {02/2011},
	pages = {137 - 146},
	abstract = {Ecosystem respiration is important because it is the small imbalances between CO2 uptake via photosynthesis and CO2 release by ecosystem respiration that determine the effect of the biosphere on atmospheric CO2. For subalpine grasslands with mild winters we do not know the size of under-snow respiration relative to the total annual ecosystem respiration. This study determines the contribution of respiration through snow to total annual respiration, and models annual ecosystem respiration based on relationships with soil temperature and water content. Measurements were made monthly for two years in an unmanaged subalpine grassland in the Snowy Mountains of Australia. The vegetation is sparse (aboveground mass  =  355{\textendash}605 g m-2, belowground mass  =  570{\textendash}1010 g m-2) and dominated by native perennial C3 grasses and sedges. Ecosystem respiration was positively related to temperature, and there was some evidence that ecosystem respiration was more temperature sensitive at temperatures between 0 and 2 {\textdegree}C than at warmer temperatures. Annual ecosystem respiration was 12.1 Mg C ha-1 yr-1 in 2007/2008 and 10.5 Mg C ha-1 yr-1 in 2008/2009. Maximum daily rates of ecosystem respiration of 7 {\textmu}mol CO2 m-2 s-1 occurred during summer, while minimum rates occurred under snow cover and were 0.2 to 0.9 {\textmu}mol CO2 m-2 s-1. The duration of permanent snow cover was 60{\textendash}68 days (equivalent to 16{\textendash}18\% of the year) and ecosystem respiration under snow was 4.1 to 4.3\% of annual ecosystem respiration, which is smaller than the 10{\textendash}50\% commonly reported from studies in areas with longer snow-covered periods.},
	doi = {10.1657/1938-4246-43.1.137},
	author = {Warren, Charles R. and Taranto, MT}
}
@article {BF-2925,
	title = {Temporal variation in pools of amino acids, inorganic and microbial N in a temperate grassland soil},
	journal = {Soil Biology and Biochemistry},
	volume = {42},
	year = {2010},
	month = {2/2010},
	pages = {353 - 359},
	abstract = {Plants can take up intact amino acids, even in competition with soil microbes, yet we lack detailed information on which amino acids dominate the soil and whether amino acid composition varies seasonally. This study tested the hypotheses that 1) the pool of amino acid N is generally larger than inorganic N; 2) temporal changes in the concentration of amino acid N is related to changes in the size of the microbial N pool; and 3) amino acid N is dominated by simple, neutral amino acids during warm months, whereas during cold months the amino acid N is dominated by more complex aromatic and basic amino acids. Approximately every month for two years we collected soil from a temperate, sub-alpine grassland in the Snowy Mountains of Australia. We quantified exchangeable pools of amino acids, nitrate and ammonium in 1 M KCl extracts. Microbial N was quantified by chloroform fumigation. Averaged across the 21 monthly samples, nitrate was 13\% of the quantified pool of soluble non-protein N, ammonium was 34\% and amino acid N was 53\%. These data are consistent with our hypothesis that the pool of amino acid N is larger than inorganic N. There was substantial variation between months in concentrations of amino acids and inorganic N, but no clear temporal pattern. Microbial N did not vary between months, and thus changes in amino acid N were unrelated to microbial N. Principal components analysis indicated multivariate groupings of the different pools of N that were broadly indicative of function and/or biosynthetic relationships. Thus PCA identified a grouping of aromatic amino acids (Phe and Try) with amino acids derived from oxaloacetate (Asp, Ala, Val, Leu, Ile), and a second group comprising microbial N, nitrate and glycine. The pool of exchangeable amino acid N was dominated by Arg (26\% of amino N) Val (20\%) Gln (18\%), Try (8\%) and Asn (8\%). Contrary to our hypothesis, the composition of the amino acid pool did not vary in a consistent way between months, and there was no evidence simple amino acids were relatively more abundant in warm months and complex amino acids in cool months.},
	doi = {10.1016/j.soilbio.2009.11.017},
	author = {Warren, Charles R. and Taranto, MT}
}
