We used the longest-term data presented in a study, and except for analyses to evaluate treatment intensity or burn severity, we averaged data across different intensities of a treatment type (e.g., different levels of thinning) in the infrequent cases where different intensities were presented. From extracted data for
both understory abundance and richness, we calculated a ratio of treatment:control or after:before treatment. For studies with both pre-treatment data and controls, we first calculated the after:before ratio then used that to calculate the treatment:control Bortezomib supplier ratio. Some papers presented data as relative differences (such as percent change from pre- to post-treatment), which could result in negative ratios. Additionally, some studies had zeros as denominators (e.g., if controls had zero plants), precluding calculation of ratios. In these cases, we simply calculated the raw difference between
after/before or treated/control values. We considered conducting a formal statistical meta-analysis, but the available data had several features that limited meta-analysis. Presentation of relative differences (resulting in negative values) or presence of zeros in some studies, together with many papers not reporting a measure of variability or being unreplicated, complicated calculation of meta-analytical statistics (Harrison, 2011). It is noteworthy, but not uncommon, that some of the most ecologically LDN-193189 concentration insightful studies in our data set did not meet requirements for calculation of standard meta-analysis statistics, such as Knapp et al.’s (2013) remeasurement of 79-year-old silvicultural treatments installed in 1929. Another significant issue was that, for several of our questions, approximately equal proportions of decreases and increases were reported across studies. Analyzing an average or median effect size in this situation represented an effect size (i.e., zero
or no change) rarely or never actually occurring in the literature. We adopted a hybrid approach to data analysis by using a combination of effect sizes (after:before or treatment:control ratios) as appropriate, ranking relative Alanine-glyoxylate transaminase responses to treatments, and categorizing understory responses to treatment as relative increase (ratios >1, or raw difference >0), no change (ratios = 1 or difference = 0), or decrease (ratios <1, difference <0). For Question 1 (relative influences of treatments on total understory plant abundance and species richness), we ranked relative responses of an understory measure among treatments within a study (e.g., +++ signified the greatest increase among treatments in a study where an understory measure increased in all three treatments) and as increase (+) or decrease (−) if only one treatment was evaluated in a study. For Question 2 (influence of time since treatment), we regressed time since treatment with treatment : control ratio of total plant abundance and species richness.
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