DOI: 10.5061/dryad.q573n5ttg
title: Dead tree removal after drought mortality increases understory plant diversity in a mixed conifer forest

description: Altered disturbance regimes during a time of rapid global change present
 challenges for decision-making concerning ecosystem recovery. In the
 Sierra Nevada of California, USA, 129 million trees died due to severe
 drought from 2012-2017, raising concerns over forest ecosystem health and
 dead fuel loads available for future wildfires. One approach to managing
 forests after tree mortality is to cut and remove standing dead trees, yet
 the ecological effects of this management practice are not well
 understood, particularly in western U.S. montane coniferous forests. We
 compared the management practice of dead tree removal versus no removal
 following severe drought and insect-induced tree mortality in the Sierra
 Nevada and evaluated the initial effects on understory plants in terms of
 diversity, vegetative cover, and community composition. Understory plants
 were sampled in 122 paired plots (treated and untreated; 22 m diameter)
 spanning 300 km of the Sierra Nevada one to five years after the removal
 of recently dead trees. We found that plant species diversity was higher
 where dead trees were removed across all plant subgroups (annuals,
 perennials, shrubs, natives, and non-natives). Higher total plant species
 richness and annual species richness were associated with lower live tree
 cover, but shrub and perennial richness were associated with higher
 estimated soil moisture and not with live tree cover. Understory
 vegetative cover was modestly lower with treatment, driven largely by
 decreases in tree sapling cover, but annual and non-native species cover
 were higher with treatment. Plant community composition was significantly
 different in treated and untreated plots (perMANOVA; p = 0.006), but
 communities were highly overlapping. Our results align with research in
 other western U.S. forests that found a near-term increase in understory
 diversity following drought-killed dead tree harvest, but future research
 is needed to identify longer-term patterns. Our project provides essential
 information to assess whether recovery goals related to understory
 vegetation are likely to be met under different post-disturbance
 management scenarios.
description: Field data were collected in 2020 and 2021 at six sites in the
 Sierra Nevada, California, USA on the Stanislaus, Sierra, and Sequoia
 National Forests, the Sequoia National Monument, on private lands owned
 and managed by Southern California Edison, and at Mountain Home
 Demonstration State Forest.  Soil lab data were
 processed at the University of California, Davis, Analytical
 Laboratory.  Treatment consisted of felling and removal
 of dead trees via single-tree selection.  Data are
 observational. Treatments were not implemented experimentally but rather
 as part of separately planned management actions. 
description: # Dead tree removal after drought mortality increases understory plant
 diversity in a mixed conifer forest
 [https://doi.org/10.5061/dryad.q573n5ttg](https://doi.org/10.5061/dryad.q573n5ttg) ## Description of the data and file structure These observational data were collected for the purpose of comparing ecological outcomes in treated and untreated areas after dead tree removal in Sierra Nevada mixed conifer forests. Dead tree removal was conducted in response to severe drought- and bark beetle-induced tree mortality.  Field data were collected in 2020 and 2021 at six sites in the Sierra Nevada, California, USA on the Stanislaus, Sierra, and Sequoia National Forests, the Sequoia National Monument, on private lands owned and managed by Southern California Edison, and at Mountain Home Demonstration State Forest. Soil lab data were processed at the University of California, Davis, Analytical Laboratory. Data are observational. Treatments were not implemented experimentally but rather as part of separately planned management actions.  ### Files and variables #### File: DATA\_Wayman\_and\_Sorenson.zip **Description:** Contains both the metadata file and the data files. **File: 0_Metadata_Wayman-and-Sorenson.xlsx** **Description:** Metadata, including short descriptions of each variable. Each tab includes metadata for a single .csv file. Data are provided in separate .csv files.  **File: fuel_cwd.csv** **Description:** Fuel data: coarse woody debris **File: fuel_fine.csv** **Description:** Fine fuel data: 1-hr, 10-hr, 100-hr, litter, duff, fuel depth **File: plot.csv** **Description:** Plot level data including location, plot physical characteristics, plant functional group covers, and ground covers. **File: regen_sapling**_**dbh.csv** **Description:** Diameter at breast height (DBH) and species of saplings (trees &gt;= 1.37 m tall and &lt; 7.6 cm DBH) **File: regen_sapling_height.csv** **Description:** Height, length of last year's growth, and species of saplings (trees &gt;= 1.37 m tall and &lt; 7.6 cm DBH) **File: regen_source.csv** **Description:** Species and distance from plot center of seed source trees (i.e. capable of producing seed) visible from plot **File: regen_seedling.csv** **Description:** Count by age class and species, plus height and length of last year's growth for tallest individual **File: species.csv** **Description:** Six letter species name code and percent cover of each understory species; see species_metadata.csv for full species names corresponding to codes **File: species_metadata.csv** **Description:** Species scientific names plus attributes for each documented plant species **File: trees_dead.csv** **Description:** Species six letter code, DBH, height, and other attributes of dead trees **File: trees_live.csv** **Description:** Species six letter code, DBH, height, and other attributes of live trees **File: trees_stump.csv** **Description:** Species six letter code, diameter, height, and other attributes of tree stumps **File: soil__lab_data.csv** **Description:** Organic matter and organic C processed at the UC Davis Analytical Laboratory **File: soil__sample_num.csv** **Description:** Crosswalk from laboratory sample numbers to plot number and soil sample depth **File: soil_litter.csv** **Description:** Dry weight of litter samples, including bag weights **File: soil_weights.csv** **Description:** Dry weights of soil samples NA - Not applicable