Biomass removal, initiation of biodiversity experiment

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Sum of dry mass removed for each plant growth form from each plot of biodiversity experiment. Amount of plant material removed in initial establishment of plant diversity treatments was recorded for later use as covariate or measure of disturbance. Material was weighed in the field by species, and species-level data are available from Huenneke; however, this file summarizes plant material removed (dry mass) by growth form (shrub, subshrub, perennial grass, succulent) and by total live dry mass. Also provided are mass of dead material collected from plots (same species as live material removed for each treatment) and total dry mass, live plus dead.

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field data sheets; plant material weighed in field with dairy scale and fresh mass recorded in field. Plant material from first 10 plots returned to lab for oven drying (45 C) to constant mass, then oven-dry mass recorded and ratio (dry mass/fresh mass) calculated.

Treatments were randomly assigned to plots within each of 6 blocks in the experimental area (blocking to allow for spatial heterogeneity in environment and vegetation). There are 6 replicates of each of the 8 treatments. We identified perennial woody, succulent, and grass species as belonging to a particular growth form: shrub, subshrub, grass, or succulent. The treatments imposed on a plot involved the following removal of species: growth form removals: S Shrub Removal = all shrubs removed (Larrea, Prosopis, Ephedra, etc.) Ss Subshrub Removal = all subshrubs removed (Zinnia, Xanthocephalum, etc.) PG Perennial Grass Removal = all perennial grasses removed (Muhlenbergia, Dasychloa, Setaria, etc.) Succ Succulent Removal = all leaf and stem succulents removed (Yucca, Opuntia, etc.) modifications of species richness within growth forms: Simp Simplified Only a single species (the dominant) of each growth form remaining, all subordinate species removed; plot contains only LATR, ZIAC, MUPO, and YUBA as woody or grass perennials. RedL Reduced minus Larrea Dominant of each growth form removed, only subordinates remain; Larrea removed as dominant shrub. RedP Reduced minus Prosopis Dominant of each growth form removed, only subordinates remain; Prosopis removed as dominant shrub C Control All species of all growth forms remain. For any species to be removed from a plot, each individual rooted in the plot (or that portion of an individual entering the plot from outside) was cut at ground level, minimizing soil disturbance where possible. Aboveground portions were weighed in the field (fresh weight) with a dairy scale; conversions of data from English units to g were done in the lab. Plant material for each species from the first 10 plots was brought back to the lab for drying (oven temperature 45 C) to constant mass. Ratio of dry mass to fresh mass was used to calculate dry mass for all other fresh weight measurements. Where a species was encountered in a later plot, for which there had been no collection and calculation of dry/fresh ratio, we applied the ratio from a species of similar growth form and phenology. Dead material of shrubs and subshrubs removed from a plot was picked up and weighed (assumed to be dry so no oven-drying). Dead material that was part of a live plant was not separated from the plant and was included in the live mass weight. Dead material was identified as that lying on the ground or a rooted plant that was completely dead. Dry mass of each species was summed for each plot; then species' masses were summed by growth form for each plot.

Additional information: 

The experimental area is a 250 m x 250 m area located on the NMSU Chihuahuan Desert Rangeland Research Center, immediately northeast of the intersection of the Summerford powerline road and the road running along the southern boundary of the Jornada Experimental Range and the CDRRC. The area was gridded into 25 m x 25 m plots; because of some existing environmental gradients (the area slopes to the east, and mesquite abundance varies from north to south) blocks were established and treatments were randomly assigned to plots within blocks. Plot boundaries are marked with rebar in the corners and simple steel wire stretched along boundaries; plots are identified by number and treatment on aluminum tags and on plastic rebar caps in the southwest corner.


once (removals and weighing completed fall 1995)

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