Elevated CO\u3csub\u3e2\u3c/sub\u3e further lengthens growing season under warming conditions

Observations of a longer growing season through earlier plant growth in temperate to polar regions have been thought to be a response to climate warming. However, data from experimental warming studies indicate that many species that initiate leaf growth and flowering earlier also reach seed maturation and senesce earlier, shortening their active and reproductive periods. A conceptual model to explain this apparent contradiction, and an analysis of the effect of elevated CO2—which can delay annual life cycle events—on changing season length, have not been tested. Here we show that experimental warming in a temperate grassland led to a longer growing season through earlier leaf emergence by the first species to leaf, often a grass, and constant or delayed senescence by other species that were the last to senesce, supporting the conceptual model. Elevated CO2 further extended growing, but not reproductive, season length in the warmed grassland by conserving water, which enabled most species to remain active longer. Our results suggest that a longer growing season, especially in years or biomes where water is a limiting factor, is not due to warming alone, but also to higher atmospheric CO2 concentrations that extend the active period of plant annual life cycles

Assessing soil carbon storage and climate change mitigation in biosolids mine reclamation projects

Carbon release due to land-use change and clearance of natural cover contributes significantly to anthropogenic climate change. Biosolids, the treated and stabilized solids from municipal wastewater treatment, have been applied to mines for decades to facilitate reclamation success. Using biosolids as a soil amendment in mine reclamation may help mitigate climate change by reversing carbon losses in land degraded by surface mining. However, the magnitude of long-term soil carbon storage increases with biosolids use in reclamation is largely unknown. This study compared carbon storage in biosolids-amended and conventionally reclaimed mine soils several years after closure. Soil samples from 0-15 cm and 15-30 cm depths were taken from five surface mined areas, each containing sites reclaimed either with biosolids or with conventional reclamation approaches (e.g. topsoil + synthetic fertilizer). A focus of the sampling was to acquire information on sites with greater age since final reclamation (up to 27 years). Mines reclaimed with biosolids stored an average of 32.47 ± 3.16 tonnes of carbon per hectare more in the top 15 cm of soil than conventionally reclaimed sites; in the 15-30 cm soil layer differences in carbon storage were generally not significant. Using estimates of carbon storage from one of the mine areas and other published studies, a life cycle assessment was conducted to estimate the net greenhouse gas (GHG) emissions from the use of biosolids in reclamation in the Pacific Northwest region of the United States. The assessment compared using biosolids to reclaim and reforest degraded land versus using biosolids in agriculture combined with conventional reclamation to forest. Accounting for GHG flows such as biomass and soil carbon increases and project-related fuel use, the assessment showed that using biosolids for reclamation had a greater GHG sink potential than conventional reclamation combined with agricultural biosolids applications. The results of the life cycle assessment show that coupling land reclamation with biosolids reuse carried a large potential for increases in on-site carbon storage. Incorporating biosolids into a mine reclamation program can reduce reclamation costs as well as promote climate change mitigation through increased organic carbon storage on-site.Non UBCUnreviewedOthe

Clipping and long-term grazing effects on biomass and carbohydrate reserves of Indian ricegrass

Long-term heavy grazing had little effect on root and crown biomass of Indian ricegrass (Oryzopsis hymenoides [Roem. and Schult.] Ricker), nor did it significantly affect the total nonstructural carbohydrate (TNC) reserve levels or the seasonal cycle of reserves in this grass. Fifty years of protection from livestock use had not resulted in ecotypic differentiation in Indian ricegrass for these variables. Clipping reduced crown biomass more than root biomass and removal of 90% of the aboveground biomass resulted in more than a 50% reduction in crown biomass and reserve carbohydrate pool. Two commercial strains of Indian ricegrass ('Nezpar' and 'Paloma') were compared with native Chaco Canyon strains in a uniform garden study. The Nezpar strain was superior to Paloma and the Chaco Canyon strains in production of crown biomass and TNC reserves at the more mesic garden site. The native strains from the more arid Chaco Canyon site were superior to both cultivated strains in production of roots. The native Chaco Canyon strains were little affected by clipping and have promising genetic potential for tolerance of drought and heavy grazing.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Previous grazing or clipping affects seed of Indian ricegrass

Previous heavy grazing for more than 50 years, compared with protection from livestock grazing, in the semi-arid area of Chaco Canyon in the southwestern United States did not result in any significant decrease in seed production potential of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker]. There also were no significant differences in seed production between grazed and ungrazed collections of Indian ricegrass from the Chaco Canyon study site when transplanted and grown in a common garden. This indicated that long-term protection from livestock grazing probably had not genetically (ecotypically) altered seed production potential. Both grazed and ungrazed transplants of Indian ricegrass differed in seed production from the cultivars 'Paloma' and 'Nezpar'. Nezpar produced the greatest seed yield (312 kg/ha), while Paloma had the lowest yield (78 kg/ha). Defoliation about 1 June over a 2-year period reduced seed production and nitrogen fertilization did not increase seed yield. Previous grazing history had little effect on seed germination, but there were significant differences in germination among some collections and cultivars of Indian ricegrass. Germination was less than 5% for all entries. A tetrazolium viability test showed that seed of native strains were more viable than those of Paloma. Dormancy is a troublesome, but desirable, trait of Indian ricegrass seed for use in droughty areas.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Near-Ground Remote Sensing of Green Area Index on the Shortgrass Prairie

Drought is an inherent trait of most rangelands and sound management necessitates managers address two fundamental questions when facing a drought situation. The first question is, ‘‘what is the probability that a useful amount of precipitation will be received over the period of concern?’’ and the second question is, ‘‘if it does rain, what will the impact be in terms of quantity and quality of herbage produced?’’ The objective of this study was to address the second question. Our hypothesis was that herbage growth response to above normal summer precipitation (i.e., 23 in July and August) would be limited in the northern Great Plains because of a general absence of productive warm-season species. Study plots were twelve 5 X 10-m non-weighing lysimeters. Treatments were: 1) simulated (i.e., rainout shelter imposed), severe spring drought (i.e., 1 May - 1 July) followed by ambient precipitation thereafter; 2) simulated, severe spring drought followed by ambient precipitation thereafter plus summer irrigation (i.e., July and August); 3) ambient precipitation only; and 4) ambient precipitation plus summer irrigation. Results indicated substantial herbage production can be expected in this region during summer when precipitation is well above average because of the positive growth response of blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Griffiths), the dominant warm-season grass growing in this region. However, results also showed that level of production in the study situation (i.e., spring drought, wet summer) was only about 50% of that attained in a normal (i.e., wet spring/dry summer) year. Moreover, long-term weather data shows the probability of receiving 23 normal precipitation in both July and August (i.e., our irrigation treatments) is < 1%. Thus, although these rangelands possess the capacity to respond favorably to summer precipitation, the low probability of receiving substantial levels of summer precipitation ensures levels of ecological and economic risk remain high.  The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_jrm_v59i4_przeszlowsk

Grazing History Affects Willow Communities in a Montane Riparian Ecosystem

This study was conducted to compare data from 12 grazed and ungrazed areas and to examine the impacts of grazing treatments on a montane willow community during an 11-year period. Data were collected on willow canopy cover, species diversity, height, and stem density in a montane riparian ecosystem between 1988 and 1999 from 4 grazing treatments: long-term grazing (since the early 1900s), long-term grazing exclusion (exclosures built in the 1950s), recent grazing (sections of exclosures opened in 1988), and recent grazing exclusion (exclosures built in 1988). Willow canopy cover increased significantly for all treatments through time, with the recent grazing exclusion treatment becoming similar to that of the long-term exclusion treatment within 5 years. Species diversity was greatest in the long-term grazed treatment. Willow height averaged over treatments increased from 1988 to 1997 (P = 0.0001), but did not increase significantly after that. Height in the long-term exclosure averaged over time from 1988 to 1997 was 1.5 times greater than in the long-term grazing treatment. Stem density of willows was significantly greater in the recent exclosure than in the long-term exclosure (P = 0.008, 180%) and recent grazing treatments (P = 0.02, 120%). Recent grazing exclusion resulted in the greatest increase in canopy cover, height growth, and stem density during the 11 years of study, indicating that these variables respond positively to removal of livestock grazing. Results suggest that continued long-term grazing exclusion may lead to a closed canopy, lower willow species diversity, reduction in new stem height growth, and reduced stem recruitment. Information on the dynamics of willow growth under different grazing treatments should help resource managers determine appropriate livestock utilization levels in similar riparian areas, and develop management plans for these important ecosystems.  The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_rangelands_v58i2_leininge

Elevated CO\u3csub\u3e2\u3c/sub\u3e further lengthens growing season under warming conditions

Observations of a longer growing season through earlier plant growth in temperate to polar regions have been thought to be a response to climate warming. However, data from experimental warming studies indicate that many species that initiate leaf growth and flowering earlier also reach seed maturation and senesce earlier, shortening their active and reproductive periods. A conceptual model to explain this apparent contradiction, and an analysis of the effect of elevated CO2—which can delay annual life cycle events—on changing season length, have not been tested. Here we show that experimental warming in a temperate grassland led to a longer growing season through earlier leaf emergence by the first species to leaf, often a grass, and constant or delayed senescence by other species that were the last to senesce, supporting the conceptual model. Elevated CO2 further extended growing, but not reproductive, season length in the warmed grassland by conserving water, which enabled most species to remain active longer. Our results suggest that a longer growing season, especially in years or biomes where water is a limiting factor, is not due to warming alone, but also to higher atmospheric CO2 concentrations that extend the active period of plant annual life cycles

Soil and Vegetation Responses to Simulated Trampling

An artificial hoof was used to simulate trampling effects on native shortgrass sods in a greenhouse experiment. Severe to moderate trampling was applied to sods maintained under 3 soil water regimes. Trampling was done either throughout a 32-day period to represent a continuous grazing system, or only during the last 4 of the 32 days to simulate a short-duration grazing system. Soil bulk density increased 3%, and infiltration rate declined 57% under severe trampling. Trampling throughout the 32-day period resulted in 4% higher bulk density than did a similar level of trampling that was applied only during the last 4 days of the trial. Dead vegetation was more easily removed by hoof action than was living vegetation, and severe water stress made plant material more brittle. Aboveground biomass production was 7% greater under trampling that simulated short-duration grazing, and 17% more forage remained in the standing crop under this treatment. About 38% more vegetation was detached by hoof action under simulated continuous grazing as compared with the short-duration grazing treatment.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Runoff from simulated rainfall in 2 montane riparian communities

Riparian ecosystems are the final terrestrial zone before runoff water enters a stream. They provide the last opportunity to decrease non-point source pollution delivery to streams by removing sediments from overland water flow from uplands and roads. To quantify processes of sediment transport, filtration and deposition, it is necessary to determine runoff characteristics for the area. A rotating boom rainfall simulator was used to evaluate the effects of 3 vegetation height treatments (control, 10-cm stubble height, and clipped to the soil surface) in 2 montane riparian plant communities (grass and sedge) on runoff characteristics. Each rainfall simulation event consisted of 2 phases, a dry run of about 60 min followed by a wet run approximately 30 min later. There were no differences in time to runoff initiation for either dry or wet runs that could be attributed to vegetation height treatments for either plant community. It usually required more time for runoff to be initiated in the sedge community compared to the grass community. Generally, there were lower equilibrium runoff percentages from dry runs in the sedge community compared with the grass community. These differences were less during wet runs. Several runoff parameters had characteristics of runoff from water repellent soils. The organic layer on the soil surface exhibited signs of water repellency that reduced the water infiltration rate during the initial stages of a rainfall simulation. These results indicate that runoff and infiltration processes in the surface organic horizon of riparian zones may not respond in the classical manner. This characteristic has important implications if criteria developed in areas with less organic matter on the soil surface are used to manage overland flow in the zone. Additional studies are needed to fully describe infiltration and runoff processes in riparian plant communities.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

A Laser Point Frame to Measure Cover

The point sample method has been a standard plotless method for measurement of ground cover on ragelands since it was introduced by Levy in 1927. The instrument most commonly used to do point sampling is the point frame. Since its introduction, the point frame has undergone numberous modifications to improve efficiency and ease of use. This article introduces a laser point frame (LPF) that was designed by the Agricultural Research Service for measurement of ground cover and utilizes lasers in place of conventional metal pins. A comparative pilot study was conducted on a shortgrass prairie in northern Colorado to compare data collected using a magnetic point frame (MPF) with data collected using the LPF. Cover by species was measured from identical plots using 100 points per plot for each point frame, and sampling times were recorded for each plot. Correlations between cover data collected using the MPF and the LPF were relatively high (r2 = 0.62-0.81). Total average vegetative cover measured with the MPF was 35%, compared with 40%, using the LPF. Cover of total grasses, C4 grasses, C3 grasses, and litter, were significantly greater with the LPF method. Total sampling time per 100 points was almost half using the LPF compared with the MPF. The LPF was easy to use, efficient for measurement of cover, and is a potential replacement for conventional point frames.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_rangelands_v58i5_welt