Use of shelter tubes,grass‐specific herbicide,and herbivore exclosures to reduce stressors and improve restoration of semiarid thornscrub forests |
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| Authors: | Krysten Dick Heather D Alexander Jonathan D Moczygemba |
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| Affiliation: | 1. U.S. Fish and Wildlife Service, Laguna Atascosa National Wildlife Refuge, Los Fresnos, TX, U.S.A.;2. Department of Forestry, Forest and Wildlife Research Center, Mississippi State University, MS, U.S.A. |
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| Abstract: | In semiarid south Texas, land conversion has reduced thornscrub forests by greater than 95%, and stressors, including competition with invasive grasses, mammalian herbivory, and drought, threaten the success of restoration efforts. This study assessed the effectiveness of multiple restoration treatments aimed at improving survival and growth of thornscrub forest seedlings planted in old agricultural fields. In January 2013, we treated greater than 1,100 seedlings with grass‐specific herbicide, herbivore exclosures, and shelter tubes, used separately or combined. We further evaluated the effects of shelter tube duration (0, 6, 12, and 18 months). For each seedling, we quantified surrounding invasive grass cover, browse intensity, height, and basal diameter every 4 months until September 2014. Herbicide application decreased invasive grass cover approximately 5‐fold and increased seedling survival (23%) and basal diameter (26%). Shelter tube application for 12 and 18 months increased seedling survival (10%) and height (43 and 74%, respectively), whereas seedlings treated with tubes for only 6 months performed similar to those left untreated. Exclosures had no impact on seedling survival but increased seedling height (23%) and basal diameter (26%). We found no significant interactive effects of treatments. Overall, herbicide most effectively increased seedling survival and basal diameter growth, whereas shelter tubes proved most useful for promoting height growth. Combined, these treatments increased implementation and maintenance costs 2‐fold, but minimized seedling mortality and maximized restoration potential. These findings highlight the necessity of post‐planting seedling management to reduce stress from invasive grasses, mammalian herbivory, and drought and improve restoration potential in semiarid thornscrub forests. |
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| Keywords: | herbicide revegetation seedling semiarid shelter tube thornscrub forest |
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