Mean annual precipitation accounts for a large proportion of the variation in mean above-ground net primary production (ANPP) of grasslands worldwide. However, the inter-annual variation in production in any grassland site is only loosely correlated with precipitation. The longest record of variation in production and precipitation for a site corresponds to a shortgrass steppe in Colorado, USA. A previous study of this record showed that current-year precipitation accounted for 39% of the inter-annual variation in ANPP. In this note, we show that ca. one third of the unexplained variation is related to previous-year ANPP: ANPP per mm of precipitation was higher in years preceded by wet, more productive years than in years preceded by average years; similarly, ANPP per mm of precipitation was lower in years preceded by dry, less productive years than in years preceded by average years. Since previous-year ANPP was, in turn, associated with precipitation of a year before, current-year ANPP was also explained by precipitation of two previous years. Our finding not only increases our predictive ability, but it also changes our understanding of how ANPP responds to fluctuations in precipitation. If ANPP is thought to vary according to current-year precipitation only, it will simply track annual precipitation in time. According to this new result, however, ANPP fluctuations are buffered if wet, more productive years alternate with dry, less productive years, and they are amplified if wet or dry sequences of several years take place.
The Journal of Vegetation Science publishes papers on all aspects of vegetation science, with particular emphasis on papers that develop new concepts or methods, test theory, identify general patterns, or that otherwise are likely to interest a broad readership. Papers may focus on any aspect of vegetation science including theory, methodology, spatial patterns (including plant geography and landscape ecology), temporal changes (including palaeoecology and demography), processes (including ecophysiology), and description of ecological communities (by phytosociological or other methods), provided the focus is on increasing our understanding of plant communities. Papers with a more applied focus should be directed to our sister journal, Applied Vegetation Science. The Journal of Vegetation Science accepts original papers (including shorter ones), reviews, forum contributions and reports. It commissions reviews of selected books.
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