Plant diversity and richness metrics across inter-annual precipitation variability treatments at a grassland site in the Jornada Basin, 2019-2014

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This ongoing dataset contains metrics of plant diversity, evenness, and richness from a study at the Jornada Experimental Range (JER) in southern New Mexico. The study was designed to assess the effect of interannual variability in precipitation on average aboveground net primary productivity (ANPP) in Chihuahuan Desert grasslands. The study began in 2009, has five precipitation treatments (see Methods) and contains 50 plots (10 per treatment). This data package contains 6-year (2009 to 2014) means of metrics per plot. Annual and more recent data are available and will be released pending an upcoming publication.

Meaures of plant diversity &  richness by treatment:

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Plant diversity and richness metrics from interannual precipitation variability study


These data are part of the “Ecosystem responses to changes in inter-annual precipitation variability” study conducted in Exclosure 4 of Pasture 13 on the Jornada Experimental Range (JER) in Dona Ana County, southern New Mexico, USA. The study is designed to assess the effect of interannual variability in precipitation on average aboveground net primary productivity (ANPP) in Chihuahuan Desert grasslands. It began in 2009 and has five treatments: 1) ambient precipitation, 2) alternating +50% and -50% precipitation, 3) alternating -50% and +50% precipitation, 4) alternating + 80% and -80% precipitation, and 5) alternating -80% and +80% precipitation. Ambient precipitation plots serve as controls and have no water manipulation. Rainout shelters are used to exclude 50% and 80% precipitation and an irrigation system is used to add 50% and 80% of natural PPT (Gherardi and Sala 2013). The +50% variability, in even years, receives one half of ambient PPT by installing rainout shelters and, in odd years, receives 150% of ambient PPT via experimental watering. The +80% variability treatment alternates years of +80% with years of -80%. For the alternating treatments, annual changeover takes place during the third week of May. At the end of the study period, each treatment will have received the same relative amount, but one treatment received a natural PPT each year while the other treatments experienced sequences of dry and wet years resulting in different interannual variability. We use ten replicates per treatment for a total of 50 plots.

Vegetation cover is measured in the fall at peak biomass (between September 17th and October 5th) in 50 2.5m x 2.5m plots. There are three parallel permanent cover lines per plot, each of 250 cm length, and 60 cm apart, with ends permanently marked by rebar. Green interception is recorded per species for all plants present to a 1cm interval. Diversity indices are derived according to: 1) Tuomisto, H. 2011. Commentary: do we have a consistent terminology for species diversity? Yes, if we choose to use it. Oecologia 167:903-911 and 2) Tuomisto, H. 2012. An updated consumer’s guide to evenness and related indices. Oikos 121:1203-1218. Species richness is calculated counting the number of species with cover greater than zero.

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