Effect of Biochar and Manual Vegetation Control on Early Growth and Survival of Planted Jack Pine (Pinus banksiana Lamb.) Seedlings in Northern Minnesota

Survival of planted seedlings following a regeneration harvest can be challenging and early interventions through silvicultural treatments may be required for successful stand establishment. We tested the influence of soil amendment (biochar+compost, compost-only, or control) and vegetation control (VC; applied either initially or annually for five years using brush saws) on the growth and survival of jack pine at three sites in northern Minnesota. Application of the biochar+compost soil amendment increased seedling survival by 30% relative to the control in the first year, but there was no significant difference in survival among soil amendment treatments after five years. Both soil amendments increased diameter growth relative to the control (14% increase with biochar+compost, 10% increase with compost only), with most of the biochar+compost effect attributed to the compost. Annual VC increased diameter growth by 17% relative to initial VC, but overall effects on survival and growth were generally small relative to reported effects of VC via herbicide. The limited short-term influence of biochar and manual VC on growth and survival of jack pine indicates that these practices are likely not an effective means to increase jack pine establishment, but other benefits (e.g., increased carbon storage) may become apparent with time. Study Implications Emerging changes to forest conditions and climate are likely to create challenges for successful regeneration in even-aged silvicultural systems. Early interventions such as application of soil amendments and vegetation control may be required to increase seedling survival. However, our findings indicate that biochar application and manual vegetation control were not very effective at increasing survival and growth of planted jack pine seedlings across a range of site conditions in northern Minnesota. Further study is warranted to determine whether other biochar application rates and techniques or other forms of vegetation control are more effective for successful jack pine establishment.

Risk factors and plant management activities for the terraced agricultural systems on the Amalfi coast (Italy): an interdisciplinary approach

Cultivated terraces are outstanding modifications of mountains and hills to obtain arable land. These terraced agricultural systems are widespread traditional landscapes within the Mediterranean area. The cultivated terraces of the Amalfi Coast (Southern Italy) are outstanding examples of cultural landscapes, and they represent one of the key descriptors of the UNESCO Site. Terraces have characterized the landscape of the Amalfi Coast for a long time as their construction started during the Middle Age. However, their conservation is now threatened by abandonment, which has dramatically risen in the last 60 years, and by the ongoing climatic changes with the increased incidence of heavy rainfall events. We combined interviews with local farmers and vegetation surveys to understand which management activities are carried out to improve the conservation of cultivated terraces on the Amalfi Coast. To this end, we analyzed the linkages between these management practices and their influence on the vegetation growing on the terrace risers. Our informants identified the maintenance of waterways and walls as crucial factors influencing terrace and slope stability. The preservation of the integrity of terraces depends on periodic vegetation control and the maintenance of water drainage systems, which are carried out thanks to the active presence of farmers. According to our informants, the vegetation growing on the walls has a relevant role in the stability of terraces, and we found a prevalence of Hemicryptophytes that increase with the number of interventions over the year. Thus, active and vital agriculture becomes pivotal for the preservation of this cultural heritage.

A Dynamic Stand Growth Model System for Loblolly Pine Responding to Mid-Rotation Treatments

Intensive loblolly pine (Pinus taeda L.) plantation management in the southeastern United States includes mid-rotation silvicultural practices (MRSP) like thinning, fertilization, competitive vegetation control, and their combinations. Consistent and well-designed long-term studies considering interactions of MRSP are required to produce accurate projections and evaluate management decisions. Here we use longitudinal data from the regional Mid-Rotation Treatment study established by the Plantation Management Research Cooperative (PMRC) at the University of Georgia across the southeast U.S. to fit and validate a new dynamic model system rooted in theoretical and biological principles. A Weibull pdf was used as a modifier function coupled with the basal area growth model. The growth model system and error projection functions were estimated simultaneously. The new formulation results in a compatible and consistent growth and yield system and provides temporal responses to treatment. The results indicated that the model projections reproduce the observed behavior of stand characteristics. The model has high predictive accuracy (the cross-validation variance explained was 96.2%, 99.7%, and 98.6%; and the prediction root mean square distance was 0.704 m, 19.1 trees ha−1, and 1.03 m2ha−1 for dominant height (DH), trees per hectare (N), and basal area (BA), respectively), and can be used to project the current stand attributes following combinations of MRSP and with different thinning intensities. Simulations across southern physiographic regions allow us to conclude that the most overall ranking of MRSP after thinning is fertilization + competitive vegetation control (Fert + CVC) > fertilization only (Fert) > competitive vegetation control only (CVC), and Fert + CVC show less than additive effect. Because of the model structure, the response to treatment changes with location, age of application, and dominant height growth as indicators of site quality. Therefore, the proposed model adequately represents regional growth conditions.

An ABCC-type transporter endowing glyphosate resistance in plants

Glyphosate is the most widely used herbicide in world agriculture and for general vegetation control in a wide range of situations. Global and often intensive glyphosate selection of very large weedy plant populations has resulted in widespread glyphosate resistance evolution in populations of many weed species. Here, working with a glyphosate-resistant (GR) Echinochloa colona population that evolved in a Western Australia agricultural field, we identified an ATP-binding cassette (ABC) transporter (EcABCC8) that is consistently up-regulated in GR plants. When expressed in transgenic rice, this EcABCC8 transporter endowed glyphosate resistance. Equally, rice, maize, and soybean overexpressing the EcABCC8 ortholog genes were made resistant to glyphosate. Conversely, CRISPR/Cas9-mediated knockout of the EcABCC8 ortholog gene OsABCC8 increased rice susceptibility to glyphosate. Subcellular localization analysis and quantification of glyphosate cellular levels in treated ABCC8 transgenic rice plants and isolated leaf protoplasts as well as structural modeling support that EcABCC8 is likely a plasma membrane–localized transporter extruding cytoplasmic glyphosate to the apoplast, lowering the cellular glyphosate level. This is a report of a membrane transporter effluxing glyphosate in a GR plant species, and its function is likely conserved in crop plant species.

Does It Pay to Conduct Midrotation Competition Control and/or Fertilization? Results from Two Thinned Loblolly Pine Studies in the Coastal Plain of Georgia

The effects of midrotation competition control and fertilization were studied in two loblolly pine stands in the Coastal Plain of Georgia. The use of fertilizer or herbicide alone did not enhance wood yields above the control, which negates the cost spent to conduct these practices. The combined treatment of fertilization and herbicide promoted higher average pine annual increment and greater proportion of sawtimber. Site limiting factors, most likely both competing woody vegetation and low nutrient status, largely determined the effectiveness and priority of midrotation treatments. The economic returns of the combined treatment varied considerably depending on stumpage prices, treatment costs, and magnitude and duration of the growth response. Sawtimber prices (absolute value and relative to pulpwood and chip-n-saw) play a critical role in the marginal returns of midrotation treatments. Continued depressed sawtimber prices will discourage private landowners from investing in midrotation vegetation control and fertilization. Study Implications: Midrotation fertilization and vegetation control can be attractive silvicultural treatments to increase timber volume and economic returns. Assessment of site variables that limit growth, especially soil fertility and plant competition, must be conducted before prioritization of treatments. The economic returns of midrotation treatments vary greatly depending on treatment costs, stumpage prices, and magnitude and duration of pine growth response compared with controls. The pine growth response of particular concern is ingrowth of trees into the sawtimber size class and growth of sawtimber-sized trees. Sawtimber prices play a critical role in the marginal internal rate of return of the additional investment. Lackluster timber prices (especially sawtimber prices) may render investment in midrotation fertilization and vegetation control unattractive and have detrimental effects on timber supply and forest health of the region in the long term.

Impact of vegetation control measures on the bedform of braided gravel-bed river

<p>Braiding is among the most dynamic landscape on Earth. It provides diverse habitats for freshwater creatures. Unfortunately, the number of braided rivers is reducing affected by human activities in the Anthropic period. The increase of the vegetation cover within the river corridor is one important factor, which is induced by flow regime change, land-use change, or alien vegetation invasion. Vegetation clearance could be a promising measure to mitigate vegetation overexpansion. Several previous research suggested vegetation clearance may induce geomorphological metamorphosis. However, quantitative prediction of the morphological change resulted from the vegetation clearance is still an open question to date. We simulated the river morphological response of vegetated braided river with gravel bed to the vegetation clearance using the Nays2DH model combined with a vegetation module. Except for vegetation removal, the developed conceptual model considered vegetation colonization and the destruction induced by floods. Multiple scenarios have been tested, considering two vegetation types (strong and weak vegetation), two clearance methods (full clearance and partial clearance), and two maximum discharge. The full clearance scenario stood for the removal of above-ground and underground biomass simultaneously, and the partial clearance scenario stood for the removal of above-ground biomass. Braided rivers had developed for both no vegetation and river with weak vegetation cover. The bedform affected by strong vegetation coverage consisted of a main channel and small channels on the floodplain, which was consistent with previous experimental results. The distinctive morphology of developed bed form depended on the dominant factor in the vegetation-geomorphology interaction: vegetation dominant or physical process dominant. River morphology responded differently to the vegetation control measure based on the dominating factor. For the vegetation dominated river, the developed main channel tended to be braiding after the vegetation removal, and the river morphology change was sensitive to the vegetation clearance method. By contrast, river morphology changed insignificantly by vegetation colonization and after vegetation removal if the river physical process was dominant. We also found that the small channels on the floodplain promoted sediment transport from the floodplain to the main channel after the vegetation clearance. Thus, the morphological response to the vegetation clearance method was also affected by the reduction of maximum discharge because the connectivity between floodplain and channel was reduced. To improve vegetation clearance effectiveness, we recommend increasing the connectivity between the floodplain and the main channel, such as excavating small channels on the floodplain.</p>

The influence of fencing on seedling establishment during reforestation of oak stands: a comparison of artificial and natural regeneration techniques including costs

In temperate Europe, oak-dominated forests are widespread, supporting high biodiversity and providing important ecosystem services. Insufficient natural regeneration has, however, been a concern for over a century. The objective of this study was to gain insights into differences in regeneration success using artificial and natural regeneration techniques for reforestation of oak (Quercus robur L.) stands. We monitored seedlings following planting, direct seeding and natural regeneration over five years in a randomized block experiment in southern Sweden with fenced and non-fenced plots. Fencing had a strong positive effect on height growth, especially for planted seedlings that were taller than the other seedlings and more frequently browsed in non-fenced plots. In contrast, there was little effect of fencing on survival, establishment rate and recruitment rate of seedlings. Due to aboveground damage on seedlings from voles, protection of acorns did not improve establishment rate following direct seeding. Under current circumstances at the site with a sparse shelterwood of old oaks, we conclude that natural regeneration was the most cost-efficient regeneration method. It resulted in the most seedlings at the lowest cost. However, regeneration success was heavily influenced by interference from herbaceous vegetation. With a small additional investment in vegetation control, the results might have been improved for planting and direct seeding.

Effect of biofuel waste, urea, deer browsing and vegetation control on Pinus banksiana seedling growth on a dry upland site in central Canada

Ash from biofuels and nitrogen fertilizer are increasingly being used as soil amendments. While this can increase tree growth, it can also increase mammalian grazing and competition with vegetation. We applied moderate amounts (1.5 t ha^-1 y^-1) of ash and 74 kg N ha^-1 y^-1 of urea in each of two years to a well-drained site in southeastern Manitoba, planted with <i>Pinus banksiana</i>. Subplots received deer browsing and/or vegetation control. The ash resulted in an increase in pH in the upper 15m of mineral soil from ca. 5.7 to 6.6, and the urea created short-term spikes in soil inorganic N (NH₄ and NO₃) levels. Urea combined with ash significantly increased seedling relative growth rates in the first two years, with seedlings being largest with urea, with or without ash. However, by the fourth year seedling growth and size did not differ between the amendments. Urea application increased browsing damage to 91 %, but only when vegetation was mowed. Browsing guards resulted in seedlings having 1.6 times greater shoot mass by the end of the fourth growing season. These results suggest that on sandy soils in the dry region of central Canada, <i>P. banksiana</i> may get little benefit from ash applications.