Species-specific responses to restoration interventions in a Tamaulipan thornforest

Mohsin, Faeqa; Arias, Mylen; Albrecht, Clifton; Wahl, Kimberly; Fierro‐Cabo, Alejandro; Christoffersen, Bradley

doi:10.1016/j.foreco.2021.119154

Cited by 9 publications

(13 citation statements)

References 74 publications

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“…Soil warming also alters the activity of beneficial and pathogenic soil organisms and the overall balance of their interactions with plants [ 54 ]. Seedling survival after planting is relatively low among thornscrub reforestation projects in south Texas, with much mortality attributable to drought stress and herbivory [ 22 , 55 , 56 ]. Seedlings with better-developed root systems should be more resilient to both stressors, so approaches that promote root development could have large impacts on the success of planting efforts.…”

Section: Introductionmentioning

confidence: 99%

Effects of Scarification, Phytohormones, Soil Type, and Warming on the Germination and/or Seedling Performance of Three Tamaulipan Thornscrub Forest Species

Luera

Wahl-Villarreal

Christoffersen

et al. 2021

Plants

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The Tamaulipan thornforests of south Texas and northeast Mexico are an ecologically and economically important conservation hotspot. Thornforest restoration is limited by native tree and shrub seedling availability for planting. Seedling shortages arise from low seed availability and knowledge gaps regarding best practices for germinating and growing the 70+ thornforest species desired for restoration plantings. To fill key knowledge gaps, we investigated three ecologically important thornforest species with low or highly variable germination or seedling survival rates: Ebenopsis ebano, Cordia boissieri, and Zanthoxylum fagara. For each, we quantified the effects of different dosages of chemical seed treatments used to promote germination (sulfuric acid, SA; gibberellic acid, GA; indole-3-butyric acid, IBA) on germination likelihood and timing. We also quantified the effects that these chemical seed treatments, soil media mixture type, and soil warming had on seedling survival, growth, and root morphology. Ebenopsis germination peaked (>90%) with 40–60 min SA treatment. Cordia germination peaked (40%) with 100 mg/L GA treatment. Zanthoxylum germination was negligible across all treatments. Seed molding was rare but stirring during SA treatment reduced Ebenopsis molding by 4%. Ebenopsis seedling survival, height, leaf count, and root morphology were minimally affected by seed treatments, generally reduced by warming, and influenced by soil mix, which also mediated responses to warming. These results suggest improvements to existing practices that could increase Ebenopsis germination by 10–20% and potentially double Cordia germination.

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Section: Introductionmentioning

confidence: 99%

Effects of Scarification, Phytohormones, Soil Type, and Warming on the Germination and/or Seedling Performance of Three Tamaulipan Thornscrub Forest Species

Luera

Wahl-Villarreal

Christoffersen

et al. 2021

Plants

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“…A subset of 3600 individuals (150 individuals per each of 24 species) were assessed in intensive seedling demography plots for growth and mortality over 1 year (Mohsin et al., 2021). In May 2019, we opportunistically designed the present experiment using pre‐existing planted seedlings and preliminary data from the intensive seedling demography plots.…”

Section: Methodsmentioning

confidence: 99%

“…Reforestation, primarily through seedling transplantation, has been ongoing in the region for more than 30 years, but assessment of such efforts has been limited until recently. Previous work has experimented with restoration interventions such as tube shelters (Dick et al., 2016), slow‐release moisture and mycorrhizal inoculation (Mohsin et al., 2021). Collectively, this work has shown that seedling shelters significantly reduce mammalian browsing, and, together with management of invasive grasses, can improve first‐year seedling survival, yet large species differences in survival remain.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Do early‐successional weeds facilitate or compete with seedlings in forest restoration? Disentangling abiotic versus biotic factors

Arias

Kariyat

Wahl

et al. 2021

Ecol Sol and Evidence

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Semi‐arid forests need cost‐effective restoration strategies to address their severe degradation. Tree shelters are often used to minimize abiotic and biotic stress during seedling establishment. We asked if early‐successional weeds act as a natural shelter by facilitating native seedlings, contingent on abiotic and biotic stressors and seedling ecological strategy. We conducted a manipulative weed exclusion experiment at a semi‐arid site in South Texas targeted for large‐scale forest restoration to discern the net effect of weeds on the growth and survival of target thornscrub tree and shrub seedlings. We assessed the roles of contrasting seedling ecological strategies (fast vs. slow growth habit), temporal variation in abiotic stress, microclimate and mammalian herbivory in modulating weed–seedling interactions. Ungulate herbivory on seedlings was common, of similar frequency across most species, but not diminished by the presence of weed neighbours. On average, seedlings growing adjacent to weed neighbours experienced modest but non‐significant increases in both height and mortality after 6 months, relative to weed‐excluded areas. However, seedlings without significant herbivory and adjacent to weed neighbours grew more vigorously (increased height and branching) during hot and dry periods, particularly those species with a fast growth habit. Although seedling light‐saturated photosynthetic capacity (Asat) and air temperature were unaffected by weed presence during hot and dry periods, afternoon light levels were reduced by approximately 50%, possibly indicative of lower leaf temperatures and improved seedling water status. Our results show that realizing the facilitative potential of weeds in semi‐arid forest restoration requires minimizing mammalian herbivory and temporally separating competition for resources. Managing for intermediate but not excessive levels of forb canopy cover is likely required to reduce high radiation loads and reduce transpiration without adverse competitive effects. Longer‐term experiments manipulating cover crop identity, cover and mammalian herbivory will inform whether forbs can be effectively exploited to enhance restoration success at large scales.

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“…Despite the scale and expense of this project, post‐planting assessments of seedling survival, species recruitment, and forest development are lacking and the few studies which have been carried out have focused solely on seedling growth and survival and for a maximum of 2 years post‐planting (Alexander et al 2016; Dick et al 2016; Mohsin et al 2021). Chronic drought and extreme summer heat pose significant challenges to seedling survival in the LRGV, especially in the context of old‐field restoration where established woody nurse plants are absent and soil structure and organic content may be impaired.…”

Section: Introductionmentioning

confidence: 99%

Winners and losers in dryland reforestation: species survival, growth, and recruitment along a 33‐year planting chronosequence

Albrecht

Contreras

Wahl-Villareal

et al. 2022

Restoration Ecology

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Reforestation in the Lower Rio Grande Valley (LRGV) of Texas began in the 1960s and to date over 6,475 ha of land has been reforested. However, there has been minimal assessment to understand differential species success, compositional trends, and the aboveground carbon sequestration potential of these developing forests. We coupled quantitative planting information of >50 native woody tree and shrub species with surveys of 5,223 stems of 4,606 individuals in a chronosequence of restored forests ranging in age from 1 to 33 years to estimate species‐specific mortality rates, biomass accumulation and recruitment, as well as compositional trends in the herbaceous understory. We show that 7–15 years are required for mortality rates of the transplanted cohort to stabilize to background levels observed in other dry forests. A small number of species, mostly N‐fixing trees with a deep rooting habit, persisted on the landscape beyond 15 years. Even so, aboveground biomass (corrected for differences in initial planting density) accumulated at an average rate of 1.41 Mg ha−1 yr−1 compared to 0.35 Mg ha−1 yr−1 for a fallow old‐field. Species biomass growth rates increased with decreasing mortality, as did the abundance of recruits, suggesting a degree of reproduction by initial planted cohorts. However, a suite of highly competitive exotic grasses increases in density over a 25‐year period, which we link to suppressed seedling recruitment. This poses a serious challenge to the long‐term sustainability of planted forests in the LRGV. We highlight potential avenues of research and modification to restoration methodologies.

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Species-specific responses to restoration interventions in a Tamaulipan thornforest

Cited by 9 publications

References 74 publications

Effects of Scarification, Phytohormones, Soil Type, and Warming on the Germination and/or Seedling Performance of Three Tamaulipan Thornscrub Forest Species

Effects of Scarification, Phytohormones, Soil Type, and Warming on the Germination and/or Seedling Performance of Three Tamaulipan Thornscrub Forest Species

Do early‐successional weeds facilitate or compete with seedlings in forest restoration? Disentangling abiotic versus biotic factors

Winners and losers in dryland reforestation: species survival, growth, and recruitment along a 33‐year planting chronosequence

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