Estimating net primary productivity of grasslands from field biomass measurements in temperate northern China |
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Authors: | Ni Jian |
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Institution: | 1.Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Xiangshan Nanxincun 20, 100093, Beijing, China ;2.Max Planck Institute for Biogeochemistry, Hans Kn?l Strasse 10, P.O. Box 100164, D-07701, Jena, Germany ; |
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Abstract: | Data on field biomass measurements in temperate grasslands of northern China (141 samples from 74 sites) were obtained from
23 Chinese journals, reports and books. Net primary productivity (NPP) of grasslands was estimated using three algorithms
(peak live biomass, peak standing crop and maximum minus minimum live biomass), respectively, based on availability of biomass
data in sites. 135 samples which have aboveground biomass (AGB) measurements, have peak AGB ranges from 20 to 2021 g m–2 (mean = 325.3) and the aboveground NPP (ANPP) ranges from 15 to 1647.1 g m–2 per year (mean = 295.7). 72 samples which have belowground biomass (BGB) measurements, have peak BGB ranges from 226.5 to
12827.5 g m–2 (mean = 3116) and the belowground NPP (BNPP) ranges from 15.8 to 12827.5 g m–2 per year (mean = 2425.6). In total 66 samples have the total NPP (TNPP), ranging from 55.3 to 13347.8 g m–2 per year (mean = 2980.3). Mean peak biomass and NPP varied from different geographical sampling locations, but they had a
general rough regularity in ten grasslands. Meadow, mountain and alpine grasslands had high biomass and NPP (sometimes including
saline grassland). Forested steppe, saline grassland and desert had median values. Meadowed and typical steppes had low biomass
and NPP (sometimes including desert). The lowest biomass and NPP occurred in deserted steppe and stepped desert. Grassland
ANPP has significant positive relationships with annual and summer precipitation as well as summer temperature (all p<0.01).
However, grassland BNPP and TNPP have more significant negative relationships with summer temperature (p<0.01) than with annual
temperature (p<0.05). The analysis of climate – productivity correlations implied that aboveground productivity is more controlled
by rainfall, whereas belowground and total productivity is more influenced by temperature in the temperate grasslands of northern
China. The present study might underestimate grassland NPP in northern China due to limitation of biomass measurements. Data
on relative long-term aboveground and belowground biomass dynamics, as well as data of standing dead matter, litterfall, decomposition
and turnover, are required if grassland NPP is to be more accurately estimated and the role of temperate grasslands in the
regional to global carbon cycles is to be fully appreciated.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | Aboveground and belowground net primary productivity Data limitation Methodology in estimating NPP Peak biomass Precipitation Temperature |
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