Initial experimental effects of intensive forest management on avian abundance

Ecological Applications

Stokely

et al. 2017

Self Cite

Intensive forest management (IFM) promises to help satisfy increasing global demand for wood but may come at the cost of local reductions to forest biodiversity. IFM often reduces early seral plant diversity as a result of efforts to eliminate plant competition with crop trees. If diversity is a function of bottom-up drivers, theory predicts that specialists at lower trophic levels (e.g., insect herbivores) should be particularly sensitive to reductions in plant diversity. We conducted a stand-level experiment to test bottom-up controls on moth community structure, as mediated by degrees of forest management intensity. Using a dataset of 12,003 moths representing 316 moth species, moth richness decreased only slightly, if at all, as herbicide intensity increased (P = 0.062); the moderate treatment, which is most commonly applied in the northwestern USA, was estimated to have 4.72 (±2.14 SE, P = 0.039) fewer species than the control. Structural equation modeling revealed strong support for an effect of herbicide on plant abundance, which influenced plant species richness and subsequently moth species richness. Moth species richness was associated with plant species richness and followed a power law function (z = 0.42, P = 0.006), which is surprisingly consistent with a recent large-scale experiment in agricultural systems, and provides support for bottom-up drivers of moth community structure. Moth abundance was not influenced by the direct effects of silvicultural herbicide treatments. Site-level effects and variation in pre-harvest vegetation communities resulted in residual broadleaf and herbaceous vegetation in even the most intensive treatment. Even at low densities, these residual deciduous and herbaceous plants supported higher than expected moth abundance and richness. We conclude that forest management practices that retain early seral vegetation diversity are the most likely to conserve moth communities.

Section: Discussionsupporting

confidence: 56%

“…Stand selection followed a randomized complete block design with four treatment stands located within each of the eight blocks (Betts et al 2013; Fig. 1).…”

Section: Treatmentsmentioning

confidence: 99%

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Plant diversity enhances moth diversity in an intensive forest management experiment

Root

Ecological Applications

Stokely

et al. 2017

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“…; Betts et al . ). However, we emphasize that long‐term data are required to quantify whether this potential benefit of intensive management remains until stand rotation.…”

Section: Discussionmentioning

confidence: 97%

Assembly dynamics of a forest bird community depend on disturbance intensity and foraging guild

Kroll

Journal of Applied Ecology

Giovanini

et al. 2016

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Summary Tree plantations occur globally and are often promoted as a strategy to supply wood products for an expanding human population while reducing pressure on natural forests. Herbicides can accelerate growth of crop trees by suppressing competing vegetation, but little information is available about potential trade‐offs with early seral biodiversity resulting from more intensive management. Using data collected over 5 years immediately following stand‐replacing disturbance (clear‐felling), we used a large‐scale experiment to test how environmental filtering influences dynamics of avian community assembly. We evaluated avian responses to three levels of plant cover reduction (light, moderate and intensive herbicide applications) in relation to a control without herbicide. Under the environmental filtering hypothesis, we expected reduced avian species richness and higher turnover as broadleaf plant cover decreases with increasing management intensity. We predicted that the most intensive treatments would exert strong negative effects on leaf‐gleaning insectivores, including several species of conservation concern due to long‐term population declines. Richness of leaf‐gleaning bird species was reduced by 23–52% over the 5 years on moderate (standard practice) vs. control treatments, but effects were substantially smaller for the non‐leaf‐gleaner guild in years 1–4 (8–25%) and disappeared by year 5 (0%). Both leaf‐gleaner and non‐leaf‐gleaner functional groups continued to colonize moderate and intensive treatments at higher probabilities than the control in Year 5 (range: 0·17–0·29), likely due to rapid vegetation recovery after herbicide applications ceased. Planted conifers were >35% taller and >70% larger in diameter in the two most intensive treatments, leading to substantially more wood volume produced per unit area than on stands without herbicide applications. Synthesis and applications. Under current management regimes, stand‐level trade‐offs between conservation of avian diversity and production of wood commodities may be less severe than previously recognized. However, in landscapes where biodiversity conservation rather than wood production is the primary goal, managers can adjust the trade‐off by making relatively small reductions in herbicide use that should have positive impacts on richness of leaf‐gleaning insectivorous birds.

“…This criterion reduced within‐block variability while limiting the potentially confounding influences of animal movement among stands and differences in local deer and elk densities among blocks (Betts et al. , Kroll et al. , Root et al.…”

Section: Methodsmentioning

confidence: 99%

Herbicides and herbivory interact to drive plant community and crop‐tree establishment

Stokely

Ecological Applications

Hagar

et al. 2018

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Land management practices often directly alter vegetation structure and composition, but the degree to which ecological processes such as herbivory interact with management to influence biodiversity is less well understood. We hypothesized that large herbivores compound the effects of intensive forest management on early seral plant communities and plantation establishment (i.e., tree survival and growth), and the degree of such effects is dependent on the intensity of management practices. We established 225-m wild-ungulate (deer and elk) exclosures, nested within a manipulated gradient of management intensity (no-herbicide control, light herbicide, moderate herbicide, and intensive herbicide treatments), replicated at the scale of whole harvest units (10-19 ha). Vegetation structure, composition, and crop-tree responses to herbivory varied across the gradient of herbicide application during the first two years of stand establishment, with herbivory effects most evident at light and moderate herbicide treatments. In the moderate herbicide treatment, which approximates management applied to >2.5 million hectares in the Pacific Northwest, United States, foraging by deer and elk resulted in simplified, low-cover plant communities more closely resembling the intensive herbicide treatment. Herbivory further suppressed the growth of competing vegetation in the light herbicide treatment, improving crop-tree survival, and providing early evidence of an ecosystem service. By changing community composition and vegetation structure, intensive forest management alters foraging selectivity and subsequent plant-herbivore interactions; initial shifts in early seral communities are likely to influence understory plant communities and tree growth in later stages of forest development.