Data set on the effects of conifer control and slash burning on soil carbon, total N, organic matter and extractable micro-nutrients

Conifer control in sagebrush steppe of the western United States causes various levels of site disturbance influencing vegetation recovery and resource availability. The data set presented in this article include growing season availability of soil micronutrients and levels of total soil carbon, organic matter, and N spanning a six year period following western juniper (Juniperus occidentalis spp. occidentalis) reduction by mechanical cutting and prescribed fire of western juniper woodlands in southeast Oregon. These data can be useful to further evaluate the impacts of conifer woodland reduction to soil resources in sagebrush steppe plant communities.


Data format
Graphically summarized into means and standard errors Experimental factors Juniper woodlands were reduced by cutting trees and burning slash in fall winter and spring to determine treatment effects to soil micro-nutrients, total N, C, and organic matter. Experimental features Computational analysis of data: percentages, means and standard errors were computed using SAS ver. 9.3 and Microsoft Excel software. Data source location Harney County, Oregon, USA; 42°56′ 10″ N, 118°36′ 30″ W and 42°53′ 25″ N, 118°34′ 18″ W Data accessibility Data is with this article and available on request.

Value of the data
This is a unique and long-term dataset of soil nutrient availability, soil carbon (SC), soil organic matter (SOM), and total nitrogen (TSN) after various juniper reduction treatments, which are lacking in the literature.
The dataset would be useful to researchers comparing short versus longer-term micro-nutrient availabilities following mechanical and prescribed fire disturbance in sagebrush steppe plant communities invaded by conifers.
The data can be used for multivariate analysis for evaluating nutrient availabilities and vegetation composition (see [2], 2017) at spatial and temporal scales.

Data
The data shows micronutrient availability, 2007-2012, for two big sagebrush-bunchgrass communities at the BLUEBUNCH site (Figs. 1 and 2), and at the FESCUE site (Figs. 3 and 4) following western juniper control. Soil carbon, SOM, and TSN are presented for the BLUEBUNCH and FESCUE sites in Figs. 5 and 6, respectively. All graphical data are in means and standard errors.
The experimental design at each site was a randomized complete block with three cut-and-burn treatments, a cut-and-leave (CUT) treatment, and woodland controls. There were five treatment replicates at each site. Treatment plots ranged from 0.2 to 0.4 ha in size. Cut-and-burn treatments included fires applied in September (SEP), January (JAN), and April (APR). All juniper in the JAN, APR, and CUT treatments were felled in July, 2006. JAN fires were applied on 17 and 19 Jan, 2007, on the BLUEBUNCH, and FESCUE sites, respectively. These fires were rated at low severity [1][2][3]. APR fires were applied on 6 Apr 2007 at both sites and fires were of low (interspace) to high (beneath cut trees) severity. JAN and APR burns required igniting individual or clusters of trees as snow or green herbaceous vegetation prevented fire from carrying in the interspaces. On SEP treatments one-third of the juniper were cut in June 2006 and once dry were used to carry strip-head fires to kill remaining live trees. The SEP fires were of moderate to high severity and were applied on 25 and 26 Sep, 2006, at the BLUEBUNCH and FESCUE sites, respectively. Burn conditions were typical for applications used to broadcast burn (SEP) and reduce western juniper fuel loads in winter and spring [1].
Flame lengths, burn duration, area burned, soil temperatures and fuel consumption were lowest in JAN treatments and greatest in SEP treatments [1]. Juniper fuel consumption in canopy and felled tree zones of SEP and APR treatments consumed all 1-h, 10-h and 100-h fuels and partly consumed the 1000-h fuels. In interspaces of SEP treatments herbaceous fine fuels were consumed as were scattered shrubs. Interspace zones in APR treatments did not burn though heat damage was noted for plants in close proximity to burning trees. In JAN treatments, fire only consumed 1-h fuels in the felled tree zones while canopy and interspace zones did not burn.
Concentrations of soil micronutrients, were collected using Plant Root Simulator probes (PRS™probes; Western Ag Innovations, Saskatoon, Saskatchewan, Canada) for each treatment in three blocks at each site. Ion-exchange resin membranes on the PRS™-probes collect anions and cation in the soil solution using electrostatic attraction. The PRS™-probes were planted vertically below the soil surface with the membrane section of the probe collecting ions from 1.  extracted with 0.5 N HCl and analyzed either colourimetrically with an auto-analyzer or plasma emission spectroscopy to determine nutrient concentrations. Nutrient availability was measured in three zones; interspace, litter mats beneath formerly standing trees (canopy), and beneath felled trees (debris). The debris zone was former interspace overlain by felled trees. Four probe sets (one set is one cation and one anion probe) were randomly placed in each zone within a treatment plot. On control plots probes were placed in canopy (beneath live trees) and interspace zones.
Total soil nitrogen (N), carbon (SC), and organic matter (SOM) in the upper 10 cm of the soil profile were determined from five soil samples, collected in July 2006, 2007, and 2012 from each treatment zone per block. SC and N were determined using a LECO CN 2000. SOM was estimated using an amended Rather method.