Resilient trees as mechanisms of nitrogen retention following bark beetle attack

Watershed disturbances (a land area sharing a single drainage point for all surface and groundwater flow paths) are often accompanied by a significant increase in the export of nitrogen from the terrestrial to the aquatic ecosystem, mainly in the form of nitrate (NO3-). Unlike other watershed disturbances, infestation by the mountain pine beetle (Dendroctonus ponderosae Hopkins) is not associated with elevated nitrate concentrations in the stream channel (Leigh Cooper, Personal Communication). The lodgepole pine ecosystem of Colorado is nitrogen-limited (Fahey et al. 1985. Biogeochemistry 1: 257-275). Across a landscape, outbreaks of the mountain pine beetle leave a patchy distribution of surviving trees. Surviving trees are nonviable hosts to the beetle. Trees of a smaller diameter at breast height are not host to the beetle, as they do not provide a sufficient food source to developing larvae in the inner bark (Cole and Amman 1969 USDA Forest Service Research Paper: INT-95). Younger, smaller lodgepole pine and spruce that survive an outbreak are, therefore, resilient to mountain pine beetle infestation. Resilient trees are potential nitrogen sinks for any release of inorganic soil nitrogen as a result of neighboring tree death. Foliar nitrogen concentrations were used as a proxy for plant nitrogen uptake of surviving trees. Of variables estimated, neighboring tree mortality was a strong predictor of foliar nitrogen concentrations of surviving trees (p\u3c0.001, R2 = 0.17). The data suggest increased nitrogen uptake by resilient trees in response to neighboring tree death. Across a watershed, resilient trees that are no longer competing for nitrogen with neighboring trees represent a nitrogen sink for available inorganic soil nitrogen, mitigating significant nitrate loss from the terrestrial to the aquatic ecosystem. Belowground measurements of soil nitrogen availability and the partitioning of nitrogen between the microbial and plan community could further explain the relative importance of resilient trees in nitrogen retention of watersheds affected by the mountain pine beetle

Validation Results: Utah and Western Sierra Variants of the Forest Vegetation Simulator

The Forest Vegetation Simulator (FVS) is the most widely available and used growth and yield model in the US. It is used in both forest management and research and the basic model framework is integrated with post-processors which can be used for many useful analyses (e.g., fire effects, bark beetle susceptibility, etc.). Recent identification of the nomenclature and a basic validation procedure has resulted in a nation-wide effort to objectively test individual FVS variants following a specific protocol (FVS Validation Subcommittee 2009). Despite the huge range of possibilities for model use, and some independent testing of various model components, (e.g., Pokharel and Froese 2009; Vacchiano et al. 2008) and variants (Lacerte et al. 2004) a comprehensive evaluation of the basic model output has yet to be done. In this project, deliverables identified as necessary to inform an appropriate model testing procedure included: (1) data set description; (2) model verification; (3) model validation; and (4) model sensitivity analysis

Colorado Native Plant Society Newsletter, Vol. 8 No. 1, January-February 1983

https://epublications.regis.edu/aquilegia/1170/thumbnail.jp

Effect of osmotic stress on plant growth promoting Pseudomonas spp.

Not AvailableIn this study we isolated and screened drought tolerant Pseudomonas isolates from arid and semi arid crop production systems of India. Five isolates could tolerate osmotic stress up to ¡0.73 MPa and possessed multiple PGP properties such as P-solubilization, production of phytohormones (IAA, GA and cytokinin), siderophores, ammonia and HCN however under osmotic stress expression of PGP traits was low compared to non-stressed conditions. The strains were identiWed as Pseudomonas entomophila, Pseudomonas stutzeri, Pseudomonas putida, Pseudomonas syringae and Pseudomonas monteilli respectively on the basis of 16S rRNA gene sequence analysis. Osmotic stress aVected growth pattern of all the isolates as indicated by increased mean generation time. An increase level of intracellular free amino acids, proline, total soluble sugars and exopolysaccharides was observed under osmotic stress suggesting bacterial response to applied stress. Further, strains GAP-P45 and GRFHYTP52 showing higher levels of EPS and osmolytes (amino acids and proline) accumulation under stress as compared to non-stress conditions, also exhibited higher expression of PGP traits under stress indicating a relationship between stress response and expression of PGP traits. We conclude that isolation and screening of indigenous, stress adaptable strains possessing PGP traits can be a method for selection of eYcient stress tolerant PGPR strains.Not Availabl

The promoted growth of genetically lodgepole and white spruce in Western Alberta compared to natural stocks

Forest regeneration has been an important focus across Alberta and the rest of Canada over recent decades. An industrial company in Alberta known as Canfor have recently began regenerating using a genetic stock where a seed bank has been used from an orchard to create the tallest, strongest and fastest growing trees in the vicinity. Although the trees are genetically improved they are not considered GMO’s simply because they have been bred properly and have not endured any unnatural tampering. GMO’s are considered genetically modified organisms which have had modification done on them. Orchard trees are improved be breeding the best mother and father within the orchard for cone production and reproducing with these cones. The idea behind this stock is to speed up the reforestation process in post-harvest stands to shorten the harvest rotation and to recreate habitat in a shorter period of time. The results from the findings show a direct comparison between the genetic stock and the natural stock at different age classes from seedling to 5 years of age. The results derived from this experiment are significant to forestry due to its potential for rapid growth which will speed up block regeneration and harvest rotations noticeably in the future

Shelterbelt: soybean production model (SBELTS)

Wind may desiccate and cause direct mechanical injury to plants. Shelterbelts, which reduce wind speed, can be beneficial to crops grown near them. However, they are not often used in the United States because there is not adequate economic information that clearly shows their benefits. It is difficult to obtain the information because shelterbelts grow slowly, taking many years to show a yield improvement, and there are also an enormous number of combinations of crops, soil types and types of shelterbelts to consider. An alternative approach to evaluating the combinations is to develop a computer model that can simulate the production of crops grown under the influence of different shelterbelts on various soil types. Therefore, the primary objective of this study was to develop a ShelterBELT - Soybean (Glycine max L.) production model (SBELTS) by linking a microclimate model and a soybean production model with a tree foliage distribution model. The secondary objective was to develop a tree foliage distribution model for use with SBELTS;The tree foliage distribution model used the two parameter Weibull distribution to model crown surface area distribution curve. We found that the shape parameter of the Weibull distribution for a hybrid cottonwood clone (Populus euramericana, NC-5326) is close to a constant 2, and the scale parameter is strongly related to height for these trees. By combining the tree foliage distribution model that predicts tree height, shelterbelt width, and other characteristics, a micrometeorological model that predicts wind speed at various distances from a shelterbelt, and a soybean growth model that is sensitive to wind speed, SBELTS model was developed;No data were available to evaluate SBELTS so the model was evaluated by comparing predicted results with published information. SBELTS was used to predict soybean yield across a field with a shelterbelt. The predicted yield curve compared well with published yield curves. SBELTS was also used to predict yields for shelterbelts in wet, average, and dry years. The results showed no shelterbelt influence in wet years, some influence in average years, and a sizeable influence in dry years

The Water Table and Soil Moisture Response Following the Removal of Conifers from an Encroached Meadow

Montane meadows play a key role in the physical and biologic processes of coniferous forests in the western United States. However, due to climate change, over grazing, and fire suppression, conifer encroachment into meadows has accelerated. In some western regions, nearly half of all meadow habitat has been loss due to conifer encroachment. To combat this issue, encroaching conifers can be removed in an attempt to increase meadow habitat and function. While multiple studies have assessed changes in soil structure and vegetation composition, few studies directly investigate changes in hydrology following meadow conifer removal projects. The goal of this study is to determine if the removal of conifers from an encroached meadow (Marian Meadow) has an effect on soil moisture and groundwater depth such that meadow hydrologic conditions are promoted. This goal will be accomplished by the following objectives: 1) develop a water budget incorporating groundwater depth, soil moisture, and climate measurements to quantify the hydrologic processes prior to and after conifer removal, 2) conduct a statistical analysis of the project meadow’s wet season water table depth prior to and after conifer removal, 3) conduct a statistical analysis of the meadow’s soil moisture prior to and after conifer removal. Marian Meadow is located in Plumas County, CA at an elevation of 4,900 feet. This 45-acre meadow enhancement project is part of a 2,046-acre timber harvest plan implemented by the Collins Pine Company. Soil moisture and water table depth sensors were installed in Marian Meadow and a control meadow in September 2013. The soil moisture sensors were installed at one and three foot depths. Soil moisture and water table depth measurements used in this study span from September 2013 through June 2016. The removal of encroaching conifers from Marian Meadow occurred in July 2015. Evapotranspiration was estimated using the Priestly Taylor equation. Electrical Resistivity Tomography (ERT) was used to determine maximum water table depths. A groundwater recession curve equation was used to model water table depths between water table depth sensor measurements and ERT measurements. Standard least squared linear regression and ANCOVA was used to determine any statistical significant difference in soil moisture and water table depths prior to and after conifer removal. The water balance indicated that the majority of Marian Meadow and the control meadow’s water storage can be attributed to precipitation and not upland sources. This hydrologic characteristic is common in dry meadows. The statistical analysis indicated that measured water table depths increased on average by 0.58 feet following conifer removal. Relative to the control meadow, soil moisture in Marian Meadow initially decreased following conifer removal. However, from November 2015 through June 2016 soil moisture increased. On average soil moisture increased by 4% following conifer removal. Also, growing season (April through September) water table depths indicated that meadow vegetation communities could be supported in Marian Meadow following conifer removal. The removal of conifers from an encroached meadow appears to promote soil moisture and water table depth conditions indicative of a meadow and meadow plant community types

Plant-growth-promoting rhizobacteria: drought stress alleviators to ameliorate crop production in drylands

Drylands are known for being a drought stressed environment, which is an alarming constraint to crop productivity. To rescue plant growth in such stressful conditions, plant-growth-promoting rhizobacteria (PGPR) are a bulwark against drought stress and imperilled sustainability of agriculture in drylands. PGPR mitigates the impact of drought stress on plants through a process called rhizobacterial-induced drought endurance and resilience (RIDER), which includes physiological and biochemical changes. Various RIDER mechanisms include modification in phytohormonal levels, antioxidant defense, bacterial exopolysaccharides (EPS), and those associated with metabolic adjustments encompass accumulation of several compatible organic solutes like sugars, amino acids and polyamines. Production of heat-shock proteins (HSPs), dehydrins and volatile organic compounds (VOCs) also plays significant role in the acquisition of drought tolerance. Selection, screening and application of drought-stress-tolerant PGPRs to crops can help to overcome productivity limits in drylands