The cloud computing technology is utilized for achieving resource utilization of remotebased virtual computer to facilitate the consumers with rapid and accurate massive data services.It utilizes on-demand resource pr...The cloud computing technology is utilized for achieving resource utilization of remotebased virtual computer to facilitate the consumers with rapid and accurate massive data services.It utilizes on-demand resource provisioning,but the necessitated constraints of rapid turnaround time,minimal execution cost,high rate of resource utilization and limited makespan transforms the Load Balancing(LB)process-based Task Scheduling(TS)problem into an NP-hard optimization issue.In this paper,Hybrid Prairie Dog and Beluga Whale Optimization Algorithm(HPDBWOA)is propounded for precise mapping of tasks to virtual machines with the due objective of addressing the dynamic nature of cloud environment.This capability of HPDBWOA helps in decreasing the SLA violations and Makespan with optimal resource management.It is modelled as a scheduling strategy which utilizes the merits of PDOA and BWOA for attaining reactive decisions making with respect to the process of assigning the tasks to virtual resources by considering their priorities into account.It addresses the problem of pre-convergence with wellbalanced exploration and exploitation to attain necessitated Quality of Service(QoS)for minimizing the waiting time incurred during TS process.It further balanced exploration and exploitation rates for reducing the makespan during the task allocation with complete awareness of VM state.The results of the proposed HPDBWOA confirmed minimized energy utilization of 32.18% and reduced cost of 28.94% better than approaches used for investigation.The statistical investigation of the proposed HPDBWOA conducted using ANOVA confirmed its efficacy over the benchmarked systems in terms of throughput,system,and response time.展开更多
The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- veri...The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory （GFDL） has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.展开更多
Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozo...Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozone in North America. The aim of this study was to research the nitrogen (N) and phosphorous (P) content and nutrient limitation (defined as N and P limitation) of growth of cyanobacteria in a northern prairies reservoir (Lake Diefenbaker [LD], SK, Canada). A combination of concentration balance analysis for N and P, controlled bioassays with the natural consortium of phytoplankton or defined monocultures of cyanobacteria, and satellite imagery was applied to address this aim. The current trophic status of Lake Diefenbaker is one of moderate eutrophication. Primary production in the lake is P-limited, and N did not represent a limiting factor for algal production. There was no significant increase in TP con- centrations between the upper and lower portions of the reservoir, indicating that most of the phosphorus in LD comes from upstream sites in Alberta. Anabaena circinalis, a species that has the potential to seriously degrade lake ecosys- tems, was identified as the predominant cyanobacteria in LD. Together with the fact that TP influxes into the reservoir primarily originate from upstream sources, these results suggest the need for remedial measures in the upstream reach of the South Saskatchewan River. Satellite imaging represented a promising approach in support of monitoring for po- tential algal blooms in LD;however, due to limited sensitivity and issues associated with atmosphere interference this methodology should only be used in combination with in situ water quality monitoring. In summary, while this study indicated that Lake Diefenbaker is potentially at risk with cyanobacteria blooms (some of which such as Anabena sp. that can produce toxins) during late summer and fall, development of clear causal relationships and risk assessment strategies is currently limited due to lack of monitoring data and programs.展开更多
We examined suitability of arbuscular mycorrhizal fungi (AMF) associated with cool-season nonnative forages on reclaimed surface-mined land in southeast Ohio for establishment of native warm-season grasses. The goal o...We examined suitability of arbuscular mycorrhizal fungi (AMF) associated with cool-season nonnative forages on reclaimed surface-mined land in southeast Ohio for establishment of native warm-season grasses. The goal of establishing these grasses is to diversify a post-reclamation landscape that is incapable of supporting native forest species. A 16-week glasshouse study compared AMF from a 30-year reclaimed mine soil (WL) with AMF from native Ohio tallgrass prairie soil (CL). Four native grasses were examined from seedling through 16 weeks of growth. Comparisons were made between CL and WL AMF on colonized (+AMF) and non-colonized plants (–AMF) at three levels of soil phosphorus (P). Leaves were counted at 4 week intervals. Shoot and root biomass and percent AMF root colonization were measured at termination. We found no difference between WL and CL AMF. Added soil P did not reduce AMF colonization, but did reduce AMF efficacy. Big bluestem (Andropogon gerardii Vitman), Indiangrass (Sorghastrum nutans (L.) Nash), and tall dropseed (Sporobolus asper (Michx.) Kunth) benefited from AMF only at low soil P while slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners) exhibited no benefit. Establishment of tallgrass prairie dominants big blue-stem and Indiangrass would be supported by the mine soil AMF. It appears that the non-native forage species have supported AMF equally functional as AMF from a regionally native tallgrass prairie. Tall dropseed and slender wheatgrass were found to be less dependent on AMF than big bluestem or Indiangrass and thus would be useful in areas with little or no AMF inoculum.展开更多
Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increase...Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increased soil erosion and soil organic carbon (SOC) mineralization rates, turning a large carbon sink into a source. The purpose of this study was to compare by land use the retention of SOC, TSN, and fly ash on sloping landscapes with an emphasis on measuring the subsoil in addition to the surface soil. Eight paired plots were established on adjacent, sloping landscape profiles in western Iowa;one site a cropland and the other a remnant tallgrass prairie. The prairie landscape had a baseline SOC stock of 232 Mg-C ha-1. After roughly 150 years of agriculture the cropland had 52% less SOC, 39% less TSN, and 22% less fly ash which equates to annual losses of 0.55 Mg-C ha-1 yr-1, 0.04 Mg-N ha-1 yr-1, and 0.0002 Mg-fly ash ha-1 yr-1.展开更多
Landuse change from native prairie to managed agriculture can have substantial impacts on soil nutrient properties. Nutrient release from soil organic matter decomposition is the soil’s inherent source of long-term f...Landuse change from native prairie to managed agriculture can have substantial impacts on soil nutrient properties. Nutrient release from soil organic matter decomposition is the soil’s inherent source of long-term fertility</span><span style="font-family:Verdana;font-size:12px;">;</span><span style="font-family:Verdana;font-size:12px;"> thus it is imperative to understand the effects of continued landuse over </span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">time to avoid mistaking actual soil property changes with simple inter-annual </span><span><span style="font-size:12px;font-family:Verdana;">variability from one year to the next. The objective of this study was to evaluate the effects of landuse (</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;"> managed agriculture and native prairie) in two contrasting physiographic regions (</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;"> the Ozark Highlands region of northwest Arkansas and the Grand Prairie region of east-central Arkansas) on the change in extractable soil nutrients over a 15-yr period from 2001 to 2016. Extractable soil Ca, Mg, and Zn increased at least two times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) under cultivated agriculture in the Grand Prairie than under native prairie in the Grand Prairie or either landuse in the Ozark Highlands. </span></span></span><span style="font-family:Verdana;font-size:12px;">Averaged across landuse</span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">, extractable soil S increased nine times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) in the Ozark Highlands than in the Grand Prairie, while extractable soil Na and Mn increased at least six times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) in the Grand Prairie than in the Ozark Highlands. </span></span><span style="font-family:Verdana;font-size:12px;">Averaged across region,</span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;"> extractable soil Mn increased 2.5 times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) under native prairie than under agricultural landuse. Results from this long-term field study clearly demonstrate how landuse and regional soil characteristics can affect near-surface soil nutrient contents, which should be taken into consideration when implementing conservation and/or ecosystem restoration activities.展开更多
Background:Incorporation of legume species into native North American pastures is considered an effective method to increase native pasture productivity and improve the nutritive value of forage.This study evaluated t...Background:Incorporation of legume species into native North American pastures is considered an effective method to increase native pasture productivity and improve the nutritive value of forage.This study evaluated the effects of inclusion of purple prairie clover(PPC,Dalea purpurea Vent.),a native legume forage,with native coolseason grasses on the in vitro fermentation and in situ digestibility of mixed forages.Methods:Whole plant PPC and mixtures of cool-season grasses were harvested when the PPC reached the vegetative(VEG),full flower(FL)and seedpod(SP)stages,and were combined in ratios(DM basis)of 0:100,25:75,50:50,75:25 and 100:0 at each maturity.In vitro ruminal incubations using these mixtures were conducted for 48 h to determine gas production(GP),in vitro DM disappearance(IVDMD),total volatile fatty acids(VFA)and ammonia-N production.Mixtures of forages harvested when the PPC reached the FL stage and 50:50 mixture of forages harvested at VEG,FL and SP stages were incubated in the rumen of three heifers for 0,2,6,12,24,48,72 and 96 h to determine in situ degradabilities of DM,neutral detergent fibre(aNDF)and crude protein(CP).Results:Contents of aNDF and ADF increased(P<0.01),while CP decreased(P<0.001)as PPC matured.Concentrations of extractable condensed tannins in PPC ranked as FL>VEG>SP(P<0.05).Regardless of PPC proportions in the mixture,GP decreased(P<0.05)with increasing PPC maturity.Increasing PPC proportions linearly increased(P<0.001)GP,IVDMD and total VFA at VEG,but linearly decreased(P<0.001)them at SP.Irrespective of PPC maturity,ammonia-N production linearly increased(P<0.01)with increasing proportions of PPC and the concentration was higher(P<0.05)at VEG than at FL and SP stages.Increasing proportion of PPC at either maturity linearly increased(P<0.001)molar percentage of acetate(A)and branched-chain VFA,but linearly decreased(P<0.001)molar percentage of propionate(P),resulting in a linearly increase(P<0.001)in the A:P ratio.Increasing FL PPC in the mixture linearly and quadratically(P<0.01)increased a(soluble fraction),but linearly and quadratically decreased(P<0.01)b(potentially degradable fraction)for DM and aNDF,resulting in linear(P<0.05)and quadratic(P<0.01)increases in DM and aNDF maximum potential degradabilities(a+b).Effective degradabilities of DM and aNDF were also linearly and quadratically increased(P<0.05),and CP was quadratically increased(P<0.05)with increasing FL PPC,with the greatest effective degradability being observed with ratios between 50:50 and 75:25.Ruminal maximum potential degradabilities of DM and aNDF decreased(P<0.001)as the forage matured.Effective degradability of DM ranked as VEG>FL>SP(P<0.001),whereas the effective degradability of aNDF was similar between VEG and FL and both were greater(P<0.01)than SP.Conclusions:Inclusion of vegetative PPC in a mixed forage diet resulted in the greatest digestibility and incorporation of PPC before seedpod stage with native grasses had a positive effect on ruminal fermentation.Effects of PPC on ruminal digestion depend on both the stage of maturity and its proportion in mixed legume-grass pastures.Pastures containing 50%of PPC in full flower stage would likely provide the greatest quality diet to grazing ruminants subject to potential animal selectivity.展开更多
Low-lying prairie wetland, which has characteristics of both grassland and wetland, has irreplaceable ecological functions in inland river basins of Northwest China. Owing to its small-scale distribution, so far, the ...Low-lying prairie wetland, which has characteristics of both grassland and wetland, has irreplaceable ecological functions in inland river basins of Northwest China. Owing to its small-scale distribution, so far, the observation and research on it are rare. The estimation of evapotranspiration is significant to ecological and environmental construction, scientific management of pasture and protection of wetland. For studying the evapotranspiration （ET） of low-lying prairie wetland in the middle reaches of the Heihe River, an inland river, in Northwest China, the automatic weather station in Linze Ecological Experimental Station of Lanzhou University （39°15′ 3″N, 100°03′ 52″ E）, Linze, Gansu Province, was selected as a case study. Based on meteorological data collected, Bowen-Ratio Energy Balance （BREB） method was used to calculate the evapotranspiration （ET） of low-lying prairie wetland. The analysis results showed that in a whole year （September 2003 -August 2004）, the total ET was 611.5mm and mean daily 1.67mm/d. The ET varied with different growing stages. In non-growing stage （NGS）, initial growing stage （IGS）, middle growing stage （MGS） and end growing stage （EGS）, the ET was 0.57, 2.01, 3.82 and 1.49mrrdd, with a percentage of total ET of 18.26%, 9.20%, 61.83% and 10.71% respectively. In March, ET began to increase. But in April, the ET increased most. After that, it increased gradually and got the maximal value in July. From then on, the ET decreased gradually. In September, the ET decreased rapidly. With the ending of growing and the freezing of soil, the ET stopped from the middle of November to February in next year. Hourly ET analysis showed that at 8：00 a.m. （during MGS at 7：00 a.m.）, the evapotranspiration began, at 13：00 p.m. got its maximal value and at 19：00 p.m. （during MGS at 20：00 p.m.）, the evapotranspiration stopped. The intensity of ET in sunny day was much larger than that in cloudy day in the same growing stage.展开更多
This study examines a management strategy for restoring grassland and prairie communities that have become degraded due to high density stands of invasive nitrogen-fixing plants. The novel management applications mini...This study examines a management strategy for restoring grassland and prairie communities that have become degraded due to high density stands of invasive nitrogen-fixing plants. The novel management applications minimize the use of herbicides and maximize the competitive interactions of native species. The management method includes two seasons of application of organic fertilizer （4-1-4）, an initial herbicide （Pasture Gard, Dow Agro） application, and mowing, where mowing was a necessary treatment to control secondary growth in prairie habitats, to control high density patches of Lespedeza （L.） Cuneata, in a completely randomized factorial experiment. The herbicide was effective in reducing L. Cuneate stem density 0 stems/m^2 from an initial 88 stems/m^2 with cover reduced to 0% from 16%. The fertilizer only treatment reduced L. Cuneata percent cover to 6% from initial cover of 16%, but did not reduce the number of stems. The management strategy is an effective fast step in restoring a native prairie invaded by a nitrogen-fixing plant.展开更多
The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temp...The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temperature line moved north in the US and the former frigid soils were cultivated. The conversion of prairie to agricultural use, as a result of climate shift, would release SOC to atmosphere and enhance greenhouse gas emissions. The SOC and TSN differences between the prairie site and agricultural land were compared in South Dakota. The agricultural land had 18% less SOC and 16% less TSN or only half of the expected loss from prairie levels. An attempt was made to document the land use history of the prairie site to understand why SOC and TSN losses were less than anticipated. The fly ash concentration levels on prairie side slopes suggested that the prairie was historically disturbed and eroded. Intensive grazing and burning contributed to the disturbance. The SOC and TSN stock losses appear to represent the minimal change that would occur in the next 100-year time period if a prairie was shifted to agricultural use as a result of climate shift and the mesic-frigid temperature line in US was to move north.展开更多
Many studies have evaluated nitrate-N leaching from tile-drained agricultural soils, but little longterm research has been performed on well-drained soils commonly throughout the Midwest. Equilibrium tension lysimeter...Many studies have evaluated nitrate-N leaching from tile-drained agricultural soils, but little longterm research has been performed on well-drained soils commonly throughout the Midwest. Equilibrium tension lysimeters installed at a depth of 1.4 m were used to measure year-round (12 month) nitrate-N leaching below chisel-plow (CP) and no-tillage (NT) continuous corn (Zea mays L.) agroecosystems to determine the potential effects of common agricultural practices on subsurface water quality. The corn systems were fertilized at a rate of 10 kg N ha-1 of starter fertilizer and 180 kg N ha-1 as NH4NO3. For comparison, nitrate-N leaching from a natural ecosystem was performed on a nearby prairie restoration (PR). Drainage, nitrate-N leaching loss, and flow-weighted mean nitrate-N concentrations for 8 years of data (1996-2003) are reported for the CP, NT and PR ecosystems. Results show that 52%, 37%, 16% of cumulative precipitation was collected as drainage, while 18%, 19%, 0.5% of the total N input was leached as nitrate-N in the CP, NT, and PR, respectively. Nearly three-quarters of the total nitrate-N was leached from each ecosystem during the period from 1 April to 30 June. The 8-yr, flow-weighted mean nitrate-N concentration measured in leachate was 9.5, 12.2 and -1 for the CP, NT and PR treatments. Annual drainage volumes and nitrate-N leaching losses were highly variable, stressing the importance of long-term studies capable of measuring year-round drainage for understanding N leaching dynamics and evaluating effects of cropping practices on potential groundwater quality.展开更多
Utah prairie dogs have been extirpated in 90% of their historical range. Because most of the population occurs on private land, this threatened species is continually in conflict with land-owners due to burrowing. The...Utah prairie dogs have been extirpated in 90% of their historical range. Because most of the population occurs on private land, this threatened species is continually in conflict with land-owners due to burrowing. The Utah Division of Wildlife Resources has been relocating Utah prairie dogs from private to public land since the 1970s, but relocations have been largely unsuccessful due to high mortality. Utah prairie dogs were relocated in 2010 and 2011 from the golf course in Cedar City, Utah to two prepared sites near Bryce Canyon National Park, Utah. Vegetation transects were established at each site to determine if there was a correlation between site vegetation composition and structure, and Utah prairie dog survival at relocation sites. The vegetation at the two sites was significantly different. One site had significantly less grass cover, more invasive plant cover, and rockier soils. The sites also had different soil structures and long-term Utah prairie dog retention rates. Newly established burrows were clustered rather than randomly distributed. Utah prairie dogs appeared to avoid placing burrows in areas with tall vegetation and rocky soils. More research is needed to determine how site selection determines longterm retention and colonization of a relocation site.展开更多
The Ozark Highlands is a unique botanical transition zone where native prairie and forest once co-existed, but conversion to managed agricultural land</span><span style="font-size:12px;font-family:Verdan...The Ozark Highlands is a unique botanical transition zone where native prairie and forest once co-existed, but conversion to managed agricultural land</span><span style="font-size:12px;font-family:Verdana;">use has severely reduced the extent of native tallgrass prairie. Quantifying soil nutrient changes over time can contribute to improved understan</span><span style="font-size:12px;font-family:Verdana;">ding of the importance of soil fertility in prairie restoration success. The objective of t</span><span><span style="font-size:12px;font-family:Verdana;">his study was to evaluate the effects of prairie ecosystem [</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;">, chronose</span></span><span style="font-size:12px;font-family:Verdana;">quence of four prairie restorations and a native prairie (NP)] and soil moisture regime (SMR;aquic and udic) on the change in extractable soil nutrients </span><span><span style="font-size:12px;font-family:Verdana;">over a 12-yr period from 2005 to 2017 in the Ozark Highlands region of northwest Arkansas. Soil Ca content decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05</span></span><span style="font-size:12px;font-family:Verdana;">) in the 17-year-old-aquic and NP-udic combinations, which did not differ and averag</span><span style="font-size:12px;font-family:Verdana;">ed </span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">55.7 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">, but did not change over time in all other ecos</span></span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">ystem-SMR combinations. Soil Na content also decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05) in the 17-year-old-aquic combination (</span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">0.7 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">), but did not change over time in any of the other ecosystem-SMR combinations. Averaged across SMR, soil P content decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05) in the 17-year-old restoration (</span></span><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">1.6 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">), while did not change over time in the other three restorations and NP. Soil K, Mg, and Zn content changes over time did not differ (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> > 0.05) among ecosystem or between SMRs.</span><b> </b><span style="font-size:12px;font-family:Verdana;">Soil nutrient changes are manifestations of soil organic matter dynamics over time and contribute to the inherent soil fertility status of an ecosystem, which needs to be balanced for proper ecosystem functioning and restoration success.展开更多
On the Silk Road, the grassland mountains of Tekes County are scattered with ancient stone people and stone statues in the Han-Wei-Jin periods. There are diseases such as weathering and cracking. In combination with t...On the Silk Road, the grassland mountains of Tekes County are scattered with ancient stone people and stone statues in the Han-Wei-Jin periods. There are diseases such as weathering and cracking. In combination with the characteristics of climate change over the past 35 years, a rain-proof shed has been designed. The appearance refers to ″Horse riding Huns″ in front of the Huoqubing tomb in the Han dynasty, and ″Yungang Grottoes″ in the Northern Wei dynasty, and combine the concept of contemporary Kazakh Boz yu. Different from the general wooden straw shed, it is light in weight, easy to install, resistant to rain and snow, strong in corrosion resistance, strong in structural strength and Readily available materials, and low in cost, which is beneficial to improving the status of cultural relic protection and delaying the speed of diseases damage.展开更多
Native prairie species have been both promoted and questioned in their ability to serve as vegetative covers for green roofs.The green roof environment with its exposure to intense sun and wind and limited moisture re...Native prairie species have been both promoted and questioned in their ability to serve as vegetative covers for green roofs.The green roof environment with its exposure to intense sun and wind and limited moisture restricts the capacity for a large diversity of species.The result has been,in many cases,a standard,low-diversity mix of Sedum species often focused on ornament and minimizes the potential for wider environmental benefits.We reviewed the ecological literature on prairie and grassland communities with specific reference to habitat templates from stressed environmental conditions and examined analogs of prairie-based vegetation on twenty-one existing green roofs.We found that many,but not all prairie and grassland species will survive and thrive on green roofs,especially when irrigated as needed or given adequate growing medium depth.We raise several important questions about media,irrigation,temperature,biodiversity and their interactions needing more study.展开更多
Yersinia pestis,causative agent of plague,occurs throughout the western United States in rodent populations and periodically causes epizootics in susceptible species,including black-tailed prairie dogs(Cynomys ludovic...Yersinia pestis,causative agent of plague,occurs throughout the western United States in rodent populations and periodically causes epizootics in susceptible species,including black-tailed prairie dogs(Cynomys ludovicianus).How Y.pestis persists long-term in the environment between these epizootics is poorly understood but multiple mechanisms have been proposed,including,among others,a separate enzootic transmission cycle that maintains Y.pestis without involvement of epizootic hosts and persistence of Y.pestis within epizootic host populations without causing high mortality within those populations.We live-trapped and collected fleas from black-tailed prairie dogs and other mammal species from sites with and without black-tailed prairie dogs in 2004 and 2005 and tested all fleas for presence of Y.pestis.Y.pestis was not detected in 2126 fleas collected in 2004 but was detected in 294 fleas collected from multiple sites in 2005,before and during a widespread epizootic that drastically reduced black-tailed prairie dog populations in the affected colonies.Temporal and spatial patterns of Y.pestis occurrence in fleas and genotyping of Y.pestis present in some infected fleas suggest Y.pestis was introduced multiple times from sources outside the study area and once introduced,was dispersed between several sites.We conclude Y.pestis likely was not present in these black-tailed prairie dog colonies prior to epizootic activity in these colonies.Although we did not identify likely enzootic hosts,we found evidence that deer mice(Peromyscus maniculatus)may serve as bridging hosts for Y.pestis between unknown enzootic hosts and black-tailed prairie dogs.展开更多
文摘The cloud computing technology is utilized for achieving resource utilization of remotebased virtual computer to facilitate the consumers with rapid and accurate massive data services.It utilizes on-demand resource provisioning,but the necessitated constraints of rapid turnaround time,minimal execution cost,high rate of resource utilization and limited makespan transforms the Load Balancing(LB)process-based Task Scheduling(TS)problem into an NP-hard optimization issue.In this paper,Hybrid Prairie Dog and Beluga Whale Optimization Algorithm(HPDBWOA)is propounded for precise mapping of tasks to virtual machines with the due objective of addressing the dynamic nature of cloud environment.This capability of HPDBWOA helps in decreasing the SLA violations and Makespan with optimal resource management.It is modelled as a scheduling strategy which utilizes the merits of PDOA and BWOA for attaining reactive decisions making with respect to the process of assigning the tasks to virtual resources by considering their priorities into account.It addresses the problem of pre-convergence with wellbalanced exploration and exploitation to attain necessitated Quality of Service(QoS)for minimizing the waiting time incurred during TS process.It further balanced exploration and exploitation rates for reducing the makespan during the task allocation with complete awareness of VM state.The results of the proposed HPDBWOA confirmed minimized energy utilization of 32.18% and reduced cost of 28.94% better than approaches used for investigation.The statistical investigation of the proposed HPDBWOA conducted using ANOVA confirmed its efficacy over the benchmarked systems in terms of throughput,system,and response time.
基金Financial support for this work was provided by Global Change Research Program of the Ministry of Science and Technology of China (2012CB956103)International Partnership Program and External Cooperation Program of the Chinese Academy of Sciences (KZZD-EW-TZ-08,GJHZ1214)Key Directional Program of the Chinese Academy of Sciences (KZCX2-YW-338-2)
文摘The worst droughts in the central part of the North American Prairie in the past several hundred years have been reconstructed from tree-ring chronologies, suggesting that some drought years have exceeded the se- verity shown by the gauge record. A general circulation model of the Geophysical Fluid Dynamics Laboratory （GFDL） has simulated climate changes for the area during the past 250 years driven by c^imatic forces, providing scenarios of extreme climate that can further diagnose the mechanisms. This study refined the drought signals from the tree ring data and GFDL modeling at inter-annual and decadal time scales and analyzed the potential mecha- nisms driving the droughts. Results showed that drought years with summer precipitation Ilower than the 10th per- centiles occurred during 1777-1789, 1847-1861 and 1886-1879 AD in the area. Both tree rings and model re- vealed that the frequency of droughts has been relatively consistent in a similar timing andl frequency with climate change. Monte Carlo analysis have detected that the tree ring chronologies have recorded drought years with probabilities of 9.3%-12.8%, and the model has simulated the droughts with probabilities 5..7%-17.8%. Under CO2 and aerosol forcing, the GFDL modeled the drought recurrences of 13 years and 25 years, which are very syn- chronous changes with tree rings and consistent with gauge records. The 20-a and 10-a time scale reoccurrences of droughts are very consistent with solar radiation cycles, and similar to the length of cycles in oceanic records, suggesting that terrestrial precipitation modeling is properly driven from sun-land-sea dynamics. Detected severity, variability and return periods of droughts from the present study make potential improvements in drought predictions and constructing scenarios for climate impacts and adaptation strategies.
文摘Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozone in North America. The aim of this study was to research the nitrogen (N) and phosphorous (P) content and nutrient limitation (defined as N and P limitation) of growth of cyanobacteria in a northern prairies reservoir (Lake Diefenbaker [LD], SK, Canada). A combination of concentration balance analysis for N and P, controlled bioassays with the natural consortium of phytoplankton or defined monocultures of cyanobacteria, and satellite imagery was applied to address this aim. The current trophic status of Lake Diefenbaker is one of moderate eutrophication. Primary production in the lake is P-limited, and N did not represent a limiting factor for algal production. There was no significant increase in TP con- centrations between the upper and lower portions of the reservoir, indicating that most of the phosphorus in LD comes from upstream sites in Alberta. Anabaena circinalis, a species that has the potential to seriously degrade lake ecosys- tems, was identified as the predominant cyanobacteria in LD. Together with the fact that TP influxes into the reservoir primarily originate from upstream sources, these results suggest the need for remedial measures in the upstream reach of the South Saskatchewan River. Satellite imaging represented a promising approach in support of monitoring for po- tential algal blooms in LD;however, due to limited sensitivity and issues associated with atmosphere interference this methodology should only be used in combination with in situ water quality monitoring. In summary, while this study indicated that Lake Diefenbaker is potentially at risk with cyanobacteria blooms (some of which such as Anabena sp. that can produce toxins) during late summer and fall, development of clear causal relationships and risk assessment strategies is currently limited due to lack of monitoring data and programs.
文摘We examined suitability of arbuscular mycorrhizal fungi (AMF) associated with cool-season nonnative forages on reclaimed surface-mined land in southeast Ohio for establishment of native warm-season grasses. The goal of establishing these grasses is to diversify a post-reclamation landscape that is incapable of supporting native forest species. A 16-week glasshouse study compared AMF from a 30-year reclaimed mine soil (WL) with AMF from native Ohio tallgrass prairie soil (CL). Four native grasses were examined from seedling through 16 weeks of growth. Comparisons were made between CL and WL AMF on colonized (+AMF) and non-colonized plants (–AMF) at three levels of soil phosphorus (P). Leaves were counted at 4 week intervals. Shoot and root biomass and percent AMF root colonization were measured at termination. We found no difference between WL and CL AMF. Added soil P did not reduce AMF colonization, but did reduce AMF efficacy. Big bluestem (Andropogon gerardii Vitman), Indiangrass (Sorghastrum nutans (L.) Nash), and tall dropseed (Sporobolus asper (Michx.) Kunth) benefited from AMF only at low soil P while slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners) exhibited no benefit. Establishment of tallgrass prairie dominants big blue-stem and Indiangrass would be supported by the mine soil AMF. It appears that the non-native forage species have supported AMF equally functional as AMF from a regionally native tallgrass prairie. Tall dropseed and slender wheatgrass were found to be less dependent on AMF than big bluestem or Indiangrass and thus would be useful in areas with little or no AMF inoculum.
文摘Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increased soil erosion and soil organic carbon (SOC) mineralization rates, turning a large carbon sink into a source. The purpose of this study was to compare by land use the retention of SOC, TSN, and fly ash on sloping landscapes with an emphasis on measuring the subsoil in addition to the surface soil. Eight paired plots were established on adjacent, sloping landscape profiles in western Iowa;one site a cropland and the other a remnant tallgrass prairie. The prairie landscape had a baseline SOC stock of 232 Mg-C ha-1. After roughly 150 years of agriculture the cropland had 52% less SOC, 39% less TSN, and 22% less fly ash which equates to annual losses of 0.55 Mg-C ha-1 yr-1, 0.04 Mg-N ha-1 yr-1, and 0.0002 Mg-fly ash ha-1 yr-1.
文摘Landuse change from native prairie to managed agriculture can have substantial impacts on soil nutrient properties. Nutrient release from soil organic matter decomposition is the soil’s inherent source of long-term fertility</span><span style="font-family:Verdana;font-size:12px;">;</span><span style="font-family:Verdana;font-size:12px;"> thus it is imperative to understand the effects of continued landuse over </span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">time to avoid mistaking actual soil property changes with simple inter-annual </span><span><span style="font-size:12px;font-family:Verdana;">variability from one year to the next. The objective of this study was to evaluate the effects of landuse (</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;"> managed agriculture and native prairie) in two contrasting physiographic regions (</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;"> the Ozark Highlands region of northwest Arkansas and the Grand Prairie region of east-central Arkansas) on the change in extractable soil nutrients over a 15-yr period from 2001 to 2016. Extractable soil Ca, Mg, and Zn increased at least two times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) under cultivated agriculture in the Grand Prairie than under native prairie in the Grand Prairie or either landuse in the Ozark Highlands. </span></span></span><span style="font-family:Verdana;font-size:12px;">Averaged across landuse</span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">, extractable soil S increased nine times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) in the Ozark Highlands than in the Grand Prairie, while extractable soil Na and Mn increased at least six times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) in the Grand Prairie than in the Ozark Highlands. </span></span><span style="font-family:Verdana;font-size:12px;">Averaged across region,</span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;"> extractable soil Mn increased 2.5 times more over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> < 0.05) under native prairie than under agricultural landuse. Results from this long-term field study clearly demonstrate how landuse and regional soil characteristics can affect near-surface soil nutrient contents, which should be taken into consideration when implementing conservation and/or ecosystem restoration activities.
基金This study was funded from AAFC/Canadian Beef Cattle Industry Science ClusterAlberta Livestock and Meat Agency.This is Lethbridge Research and Development Centre contribution number 38717038.
文摘Background:Incorporation of legume species into native North American pastures is considered an effective method to increase native pasture productivity and improve the nutritive value of forage.This study evaluated the effects of inclusion of purple prairie clover(PPC,Dalea purpurea Vent.),a native legume forage,with native coolseason grasses on the in vitro fermentation and in situ digestibility of mixed forages.Methods:Whole plant PPC and mixtures of cool-season grasses were harvested when the PPC reached the vegetative(VEG),full flower(FL)and seedpod(SP)stages,and were combined in ratios(DM basis)of 0:100,25:75,50:50,75:25 and 100:0 at each maturity.In vitro ruminal incubations using these mixtures were conducted for 48 h to determine gas production(GP),in vitro DM disappearance(IVDMD),total volatile fatty acids(VFA)and ammonia-N production.Mixtures of forages harvested when the PPC reached the FL stage and 50:50 mixture of forages harvested at VEG,FL and SP stages were incubated in the rumen of three heifers for 0,2,6,12,24,48,72 and 96 h to determine in situ degradabilities of DM,neutral detergent fibre(aNDF)and crude protein(CP).Results:Contents of aNDF and ADF increased(P<0.01),while CP decreased(P<0.001)as PPC matured.Concentrations of extractable condensed tannins in PPC ranked as FL>VEG>SP(P<0.05).Regardless of PPC proportions in the mixture,GP decreased(P<0.05)with increasing PPC maturity.Increasing PPC proportions linearly increased(P<0.001)GP,IVDMD and total VFA at VEG,but linearly decreased(P<0.001)them at SP.Irrespective of PPC maturity,ammonia-N production linearly increased(P<0.01)with increasing proportions of PPC and the concentration was higher(P<0.05)at VEG than at FL and SP stages.Increasing proportion of PPC at either maturity linearly increased(P<0.001)molar percentage of acetate(A)and branched-chain VFA,but linearly decreased(P<0.001)molar percentage of propionate(P),resulting in a linearly increase(P<0.001)in the A:P ratio.Increasing FL PPC in the mixture linearly and quadratically(P<0.01)increased a(soluble fraction),but linearly and quadratically decreased(P<0.01)b(potentially degradable fraction)for DM and aNDF,resulting in linear(P<0.05)and quadratic(P<0.01)increases in DM and aNDF maximum potential degradabilities(a+b).Effective degradabilities of DM and aNDF were also linearly and quadratically increased(P<0.05),and CP was quadratically increased(P<0.05)with increasing FL PPC,with the greatest effective degradability being observed with ratios between 50:50 and 75:25.Ruminal maximum potential degradabilities of DM and aNDF decreased(P<0.001)as the forage matured.Effective degradability of DM ranked as VEG>FL>SP(P<0.001),whereas the effective degradability of aNDF was similar between VEG and FL and both were greater(P<0.01)than SP.Conclusions:Inclusion of vegetative PPC in a mixed forage diet resulted in the greatest digestibility and incorporation of PPC before seedpod stage with native grasses had a positive effect on ruminal fermentation.Effects of PPC on ruminal digestion depend on both the stage of maturity and its proportion in mixed legume-grass pastures.Pastures containing 50%of PPC in full flower stage would likely provide the greatest quality diet to grazing ruminants subject to potential animal selectivity.
基金Underthe auspicesofthe Sino-Japan Cooperation Projectand the SpecialFund ofC hina M etrologicalA dm inistration(N o.C CSF-2005-2-Q H 39)
文摘Low-lying prairie wetland, which has characteristics of both grassland and wetland, has irreplaceable ecological functions in inland river basins of Northwest China. Owing to its small-scale distribution, so far, the observation and research on it are rare. The estimation of evapotranspiration is significant to ecological and environmental construction, scientific management of pasture and protection of wetland. For studying the evapotranspiration （ET） of low-lying prairie wetland in the middle reaches of the Heihe River, an inland river, in Northwest China, the automatic weather station in Linze Ecological Experimental Station of Lanzhou University （39°15′ 3″N, 100°03′ 52″ E）, Linze, Gansu Province, was selected as a case study. Based on meteorological data collected, Bowen-Ratio Energy Balance （BREB） method was used to calculate the evapotranspiration （ET） of low-lying prairie wetland. The analysis results showed that in a whole year （September 2003 -August 2004）, the total ET was 611.5mm and mean daily 1.67mm/d. The ET varied with different growing stages. In non-growing stage （NGS）, initial growing stage （IGS）, middle growing stage （MGS） and end growing stage （EGS）, the ET was 0.57, 2.01, 3.82 and 1.49mrrdd, with a percentage of total ET of 18.26%, 9.20%, 61.83% and 10.71% respectively. In March, ET began to increase. But in April, the ET increased most. After that, it increased gradually and got the maximal value in July. From then on, the ET decreased gradually. In September, the ET decreased rapidly. With the ending of growing and the freezing of soil, the ET stopped from the middle of November to February in next year. Hourly ET analysis showed that at 8：00 a.m. （during MGS at 7：00 a.m.）, the evapotranspiration began, at 13：00 p.m. got its maximal value and at 19：00 p.m. （during MGS at 20：00 p.m.）, the evapotranspiration stopped. The intensity of ET in sunny day was much larger than that in cloudy day in the same growing stage.
文摘This study examines a management strategy for restoring grassland and prairie communities that have become degraded due to high density stands of invasive nitrogen-fixing plants. The novel management applications minimize the use of herbicides and maximize the competitive interactions of native species. The management method includes two seasons of application of organic fertilizer （4-1-4）, an initial herbicide （Pasture Gard, Dow Agro） application, and mowing, where mowing was a necessary treatment to control secondary growth in prairie habitats, to control high density patches of Lespedeza （L.） Cuneata, in a completely randomized factorial experiment. The herbicide was effective in reducing L. Cuneate stem density 0 stems/m^2 from an initial 88 stems/m^2 with cover reduced to 0% from 16%. The fertilizer only treatment reduced L. Cuneata percent cover to 6% from initial cover of 16%, but did not reduce the number of stems. The management strategy is an effective fast step in restoring a native prairie invaded by a nitrogen-fixing plant.
文摘The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temperature line moved north in the US and the former frigid soils were cultivated. The conversion of prairie to agricultural use, as a result of climate shift, would release SOC to atmosphere and enhance greenhouse gas emissions. The SOC and TSN differences between the prairie site and agricultural land were compared in South Dakota. The agricultural land had 18% less SOC and 16% less TSN or only half of the expected loss from prairie levels. An attempt was made to document the land use history of the prairie site to understand why SOC and TSN losses were less than anticipated. The fly ash concentration levels on prairie side slopes suggested that the prairie was historically disturbed and eroded. Intensive grazing and burning contributed to the disturbance. The SOC and TSN stock losses appear to represent the minimal change that would occur in the next 100-year time period if a prairie was shifted to agricultural use as a result of climate shift and the mesic-frigid temperature line in US was to move north.
文摘Many studies have evaluated nitrate-N leaching from tile-drained agricultural soils, but little longterm research has been performed on well-drained soils commonly throughout the Midwest. Equilibrium tension lysimeters installed at a depth of 1.4 m were used to measure year-round (12 month) nitrate-N leaching below chisel-plow (CP) and no-tillage (NT) continuous corn (Zea mays L.) agroecosystems to determine the potential effects of common agricultural practices on subsurface water quality. The corn systems were fertilized at a rate of 10 kg N ha-1 of starter fertilizer and 180 kg N ha-1 as NH4NO3. For comparison, nitrate-N leaching from a natural ecosystem was performed on a nearby prairie restoration (PR). Drainage, nitrate-N leaching loss, and flow-weighted mean nitrate-N concentrations for 8 years of data (1996-2003) are reported for the CP, NT and PR ecosystems. Results show that 52%, 37%, 16% of cumulative precipitation was collected as drainage, while 18%, 19%, 0.5% of the total N input was leached as nitrate-N in the CP, NT, and PR, respectively. Nearly three-quarters of the total nitrate-N was leached from each ecosystem during the period from 1 April to 30 June. The 8-yr, flow-weighted mean nitrate-N concentration measured in leachate was 9.5, 12.2 and -1 for the CP, NT and PR treatments. Annual drainage volumes and nitrate-N leaching losses were highly variable, stressing the importance of long-term studies capable of measuring year-round drainage for understanding N leaching dynamics and evaluating effects of cropping practices on potential groundwater quality.
文摘Utah prairie dogs have been extirpated in 90% of their historical range. Because most of the population occurs on private land, this threatened species is continually in conflict with land-owners due to burrowing. The Utah Division of Wildlife Resources has been relocating Utah prairie dogs from private to public land since the 1970s, but relocations have been largely unsuccessful due to high mortality. Utah prairie dogs were relocated in 2010 and 2011 from the golf course in Cedar City, Utah to two prepared sites near Bryce Canyon National Park, Utah. Vegetation transects were established at each site to determine if there was a correlation between site vegetation composition and structure, and Utah prairie dog survival at relocation sites. The vegetation at the two sites was significantly different. One site had significantly less grass cover, more invasive plant cover, and rockier soils. The sites also had different soil structures and long-term Utah prairie dog retention rates. Newly established burrows were clustered rather than randomly distributed. Utah prairie dogs appeared to avoid placing burrows in areas with tall vegetation and rocky soils. More research is needed to determine how site selection determines longterm retention and colonization of a relocation site.
文摘The Ozark Highlands is a unique botanical transition zone where native prairie and forest once co-existed, but conversion to managed agricultural land</span><span style="font-size:12px;font-family:Verdana;">use has severely reduced the extent of native tallgrass prairie. Quantifying soil nutrient changes over time can contribute to improved understan</span><span style="font-size:12px;font-family:Verdana;">ding of the importance of soil fertility in prairie restoration success. The objective of t</span><span><span style="font-size:12px;font-family:Verdana;">his study was to evaluate the effects of prairie ecosystem [</span><i><span style="font-size:12px;font-family:Verdana;">i.e.</span></i><span style="font-size:12px;font-family:Verdana;">, chronose</span></span><span style="font-size:12px;font-family:Verdana;">quence of four prairie restorations and a native prairie (NP)] and soil moisture regime (SMR;aquic and udic) on the change in extractable soil nutrients </span><span><span style="font-size:12px;font-family:Verdana;">over a 12-yr period from 2005 to 2017 in the Ozark Highlands region of northwest Arkansas. Soil Ca content decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05</span></span><span style="font-size:12px;font-family:Verdana;">) in the 17-year-old-aquic and NP-udic combinations, which did not differ and averag</span><span style="font-size:12px;font-family:Verdana;">ed </span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">55.7 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">, but did not change over time in all other ecos</span></span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">ystem-SMR combinations. Soil Na content also decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05) in the 17-year-old-aquic combination (</span></span><span style="font-family:""><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">0.7 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">), but did not change over time in any of the other ecosystem-SMR combinations. Averaged across SMR, soil P content decreased over time (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> ≤ 0.05) in the 17-year-old restoration (</span></span><span style="font-size:12px;font-family:Verdana;">?</span><span><span style="font-size:12px;font-family:Verdana;">1.6 kg?ha</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">?yr</span><sup><span style="font-size:12px;font-family:Verdana;">?1</span></sup><span style="font-size:12px;font-family:Verdana;">), while did not change over time in the other three restorations and NP. Soil K, Mg, and Zn content changes over time did not differ (</span><i><span style="font-size:12px;font-family:Verdana;">P</span></i><span style="font-size:12px;font-family:Verdana;"> > 0.05) among ecosystem or between SMRs.</span><b> </b><span style="font-size:12px;font-family:Verdana;">Soil nutrient changes are manifestations of soil organic matter dynamics over time and contribute to the inherent soil fertility status of an ecosystem, which needs to be balanced for proper ecosystem functioning and restoration success.
文摘On the Silk Road, the grassland mountains of Tekes County are scattered with ancient stone people and stone statues in the Han-Wei-Jin periods. There are diseases such as weathering and cracking. In combination with the characteristics of climate change over the past 35 years, a rain-proof shed has been designed. The appearance refers to ″Horse riding Huns″ in front of the Huoqubing tomb in the Han dynasty, and ″Yungang Grottoes″ in the Northern Wei dynasty, and combine the concept of contemporary Kazakh Boz yu. Different from the general wooden straw shed, it is light in weight, easy to install, resistant to rain and snow, strong in corrosion resistance, strong in structural strength and Readily available materials, and low in cost, which is beneficial to improving the status of cultural relic protection and delaying the speed of diseases damage.
文摘Native prairie species have been both promoted and questioned in their ability to serve as vegetative covers for green roofs.The green roof environment with its exposure to intense sun and wind and limited moisture restricts the capacity for a large diversity of species.The result has been,in many cases,a standard,low-diversity mix of Sedum species often focused on ornament and minimizes the potential for wider environmental benefits.We reviewed the ecological literature on prairie and grassland communities with specific reference to habitat templates from stressed environmental conditions and examined analogs of prairie-based vegetation on twenty-one existing green roofs.We found that many,but not all prairie and grassland species will survive and thrive on green roofs,especially when irrigated as needed or given adequate growing medium depth.We raise several important questions about media,irrigation,temperature,biodiversity and their interactions needing more study.
基金This study was funded by the NSF/NIH joint program in Ecology of Infectious Diseases(DEB-0224328)the National Center for Environmental Research(NCER)STAR program of the US-EPA(R-82909101-0)+2 种基金the National Institutes of Health-National Institute of Allergy and Infectious Diseases(1R15AI070183)the Pacific-Southwest Regional Center of Excellence(AI065359)Achievement Rewards for College Scientists Foundation Inc.,and the Cowden Endowment at Northern Arizona University.
文摘Yersinia pestis,causative agent of plague,occurs throughout the western United States in rodent populations and periodically causes epizootics in susceptible species,including black-tailed prairie dogs(Cynomys ludovicianus).How Y.pestis persists long-term in the environment between these epizootics is poorly understood but multiple mechanisms have been proposed,including,among others,a separate enzootic transmission cycle that maintains Y.pestis without involvement of epizootic hosts and persistence of Y.pestis within epizootic host populations without causing high mortality within those populations.We live-trapped and collected fleas from black-tailed prairie dogs and other mammal species from sites with and without black-tailed prairie dogs in 2004 and 2005 and tested all fleas for presence of Y.pestis.Y.pestis was not detected in 2126 fleas collected in 2004 but was detected in 294 fleas collected from multiple sites in 2005,before and during a widespread epizootic that drastically reduced black-tailed prairie dog populations in the affected colonies.Temporal and spatial patterns of Y.pestis occurrence in fleas and genotyping of Y.pestis present in some infected fleas suggest Y.pestis was introduced multiple times from sources outside the study area and once introduced,was dispersed between several sites.We conclude Y.pestis likely was not present in these black-tailed prairie dog colonies prior to epizootic activity in these colonies.Although we did not identify likely enzootic hosts,we found evidence that deer mice(Peromyscus maniculatus)may serve as bridging hosts for Y.pestis between unknown enzootic hosts and black-tailed prairie dogs.
