Effects Of Experimental Treatments Research Articles

Mycorrhizal responsiveness trends in annual crop plants and their wild relatives—a meta-analysis on studies from 1981 to 2010

Background and aims Year of release of a cultivar reflects the agricultural and breeding practices of its time; we hypothesize that there are differences in mycorrhizal responsiveness of new high yielding and old crop plants and landraces. We evaluated the importance of the year of release on mycorrhizal responsiveness, arbuscular mycorrhizal (AM) fungal root colonization and P efficiency. We also analyzed the effect of experimental treatments, P efficiency (P acquisition and P utilization efficiency) and AM fungal root colonization on a potential mycorrhizal responsiveness trend for year of release.

Artificial soils from alluvial tin mining wastes in Malaysia – A study of soil chemistry following experimental treatments and the impact of mycorrhizal treatment on growth and foliar chemistry

For decades Malaysia was the world's largest producer of Sn, but now the vast open cast mining operations have left a legacy of some 100,000 ha of what is effectively wasteland, covered with a mosaic of tailings and lagoons. Few plants naturally recolonise these areas. The demand for such land for both urban expansion and agricultural use has presented an urgent need for better characterisation. This study reports on the formation of artificial soils from alluvial Sn mining waste with a focus on the effects of experimental treatments on soil chemistry. Soil organic matter, clay, and pH were manipulated in a controlled environment. Adding both clay tailings and peat enhanced the cation exchange capacity of sand tailings but also reduced the pH. The addition of peat reduced the extractable levels of some elements but increased the availability of Ca and Mg, thus proving beneficial. The use of clay tailings increased the levels of macro and micronutrients but also released Al, As, La, Pb and U. Additionally, the effects of soil mix and mycorrhizal treatments on growth and foliar chemistry were studied. Two plant species were selected: Panicum milicaeum and Pueraria phaseoloides. Different growth patterns were observed with respect to the additions of peat and clay. The results for mycorrhizal treatment (live inoculum or sterile carrier medium) are more complex, but both resulted in improved growth. The use of mycorrhizal fungi could greatly enhance rehabilitation efforts on sand tailings.

Facilitated Assessment of Tissue Loss Following Traumatic Brain Injury

All experimental models of traumatic brain injury (TBI) result in a progressive loss of brain tissue. The extent of tissue loss reflects the injury severity and can be measured to evaluate the potential neuroprotective effect of experimental treatments. Quantitation of tissue volumes is commonly performed using evenly spaced brain sections stained using routine histochemical methods and digitally captured. The brain tissue areas are then measured and the corresponding volumes are calculated using the distance between the sections. Measurements of areas are usually performed using a general purpose image analysis software and the results are then transferred to another program for volume calculations. To facilitate the measurement of brain tissue loss we developed novel algorithms which automatically separate the areas of brain tissue from the surrounding image background and identify the ventricles. We implemented these new algorithms by creating a new computer program (SectionToVolume) which also has functions for image organization, image adjustments and volume calculations. We analyzed brain sections from mice subjected to severe focal TBI using both SectionToVolume and ImageJ, a commonly used image analysis program. The volume measurements made by the two programs were highly correlated and analysis using SectionToVolume required considerably less time. The inter-rater reliability was high. Given the extensive use of brain tissue loss measurements in TBI research, SectionToVolume will likely be a useful tool for TBI research. We therefore provide both the source code and the program as attachments to this article.

Effects of A-solution on Halitosis and Oral Status in Preoperative NPO Patients

The aim of this study was to explore the effects of A-solution on halitosis and oral status in preoperative NPO patients. A nonequivalent control group, non-synchronized pretest-posttest design was used in this study. The participants in this study were 66 patients who were admitted for gynecologic surgery. The experimental treatment was to give oral gargling with A-solution, blended essential oils and diluted with distilled water. To identify the experimental treatment effects, halitosis, salivary pH, and oral status were measured by a portable halitosis detector, visual analogue scale, Bromo Thymol Blue (BTB), Bromo Cresol Purple (BCP) test paper and oral assessment guide. Data were analyzed using χ²-test, t-test with PASW 18.0 version. Participants were homogeneous before experimental treatment. Objective halitosis in the experimental group, measured by a portable halitosis detector (t= -8.34, p<.001) was significantly lower than the control group. Subjective halitosis was significantly lower in the experimental group (t= -9.29, p<.001). Salivary pH was significantly different between two groups (t=8.81, p<.001). Oral status was significantly better in the experimental group (t= -13.31, p<.001). These findings indicate that oral gargling using A-solution is effective in reducing patient halitosis, and improving oral status.

Effect of Gibberellic acid and Organic fertilizer on certain chemical compounds for Wheat plant Triticum aestivum L.

The experiment was conducted on plastics pots with capacity 9 kgs soil according to completely randomized design (CRD) with three replicates and used wheat cultivar (Abu-Ghraib) and used in this experiment the plant hormone gibberillic acid (100ppm) and organic fertilizer (144 gm/pot) and (gibberellic acid 100 ppm + organic fertilizer 144 gm/ pot). The aim of this research to study the effect of gibberillic acid and organic fertilizer and (gibberellic acid 100 ppm +organic fertilizer 144 gm/ pot) with control treatment on qualitative of amino acid in grain and dry shoot of wheat plant and also to study the effect of experimental treatments on Fe, Mn, Mg concentration in wheat grain and dry shoot. The results showed: gibberellic acid (100 ppm) and organic fertilizer and (gibberillic acid + organic fertilizer) lead to new amino acids comparative with the amino acid in the control treatment in wheat grain and dry shoot. And the results also showed,The gibberellic acid treatment led to increased Fe concentration in wheat grain and dry shoot, Their values were 148.6 and 114 ppm respectively. And also for organic fertilizer treatment this led to increase Fe concentration in wheat grain and dry shoot this value were 173.3 and 175.3 ppm respectively. The treatment (gibberellic acid + organic fertilizer) showed great increase in Fe concentration in wheat grain and dry shoot also and the results showed also, gibberellic acid led to decrease of Mn concentration in wheat grain and dry shoot of plant, Their values were 112.6 and 101 ppm respectively. While the organic fertilizer led to increase Mn concentration in grain and dry shoot of wheat plants and intraction in grain and dry shoot of wheat plants and increase Mn concentration in treatment (gibberellic acid + organic fertilizer) comparative with the control and the results also showed: gibberellic acid and organic fertilizer and (gibberillic acid + organic fertilizer) increased Mg concentration in grain and dry shoot of wheat plants comparative with the control treatments, Their values were 1359 and 1569 and 1899 ppm in wheat grain respectively and 2299 , 2308 , 3859 ppm in dry shoots of wheat respectively.

Direct Thrombus Imaging as a Means to Control the Variability of Mouse Embolic Infarct Models

High experimental variability in mouse embolic stroke models could mask the effects of experimental treatments. We hypothesized that imaging thrombus directly would allow this variability to be controlled. We optically labeled thrombi with a near-infrared fluorescent (NIRF) probe C15 that is covalently linked to fibrin by factor-XIIIa. Labeled thrombus was injected into the left distal internal carotid artery (ICA) of C57/BL6 mice (n=47), near its bifurcation, and laser-Doppler cerebral-blood-flow (CBF) was assessed for 30 minutes. NIRF thrombus imaging was done ex vivo at 24 hours. CBF variably decreased to 43.9±17.3% at 5 minutes (rCBF; 11.2∼80.4%). NIRF thrombus imaging at 24 hours showed variability in distribution (ICA bifurcation, adjacent and/or remote areas) and burden (2279±1270 pixels; 0∼5940 pixels). Final infarct size was also variable (21.0±10.3%; 4.7∼60.3% of the bihemispheric volume). Despite this heterogeneity, a strong thrombus-infarct correlation was maintained. The left hemispheric target infarct size (% of the hemisphere) correlated with thrombus burden, as a stronger predictor of infarct volume (P<0.001, r=0.50) than rCBF (P=0.02, r=-0.34). The infarct size was best predicted by a combination of thrombus imaging and CBF: left-hemispheric big-thrombi (>1865 pixels)/low-rCBF (≤42%) had an infarct volume of 56.9±10.4% (n=12), big-thrombi/high-rCBF had 45.9±23.5% (n=11), small-thrombi/low-rCBF 35.7±17.3% (n=11) and small-thrombi/ high-rCBF 27.3±16.4% (n=12). This is the first study to demonstrate that the highly heterogeneous nature of the mouse embolic stroke model can be characterized and managed by using near-infrared fluorescent thrombus imaging combined with CBF monitoring to stratify animals into useful subgroups.

English

Lands mined for coal and reclaimed under the Surface Mining Control and Reclamation Act (SMCRA) can be used to produce woody biomass. This study evaluates woody biomass production on SMCRA-reclaimed lands after ripping to reduce soil compaction. Four species treatments were established at two planting densities on three Wise County, Virginia, mine sites. Here, we review experimental treatment effects on biomass production after three years, and we compare results to those of two other current studies that are also evaluating biomass production on post-SMCRA mined lands. After three growing seasons, black locust produced more volume and biomass than other planted species. High-density plantings produced greater per-hectare biomass than low-density plantings. For black locust, sycamore, and a hybrid poplar clone (Populus trichocarpa x P. deltoides, clone 52-225), per-tree volume growth increments were nominally greater in year three than in year two, and fertilizers applied after year two nominally increased growth. A low-density red oak planting and a mix of red oak and eastern cottonwood planted at high density produced low amounts of biomass compared to other species. The Wise County study's hybrid poplars are growing less rapidly than hybrid poplars of the same clonal variety growing on VA, WV, and OH mine sites in a multi-state study, and its black locust biomass production is comparable to the best performing of the multi-state study's hybrid poplars. In a third study, ninety-eight hybrid poplar genotypes of three taxons (P. deltoides x P. trichocarpa (DT and reciprocal), P. deltoides x P. nigra (DN), and P. deltoides x P. maximowiczii (DM)) completed two years of growth on a VA mine site. Average biomass production by the DM clones exceeded production on the multi-state trial's best performing site and is comparable to the Wise County study's black locust production over comparable time periods. Within each taxon including DM, growth by the fastest growing genotypes is exceeding taxon means by factors of >2x. In both the Wise County and the multi-state study, significant effects by site and other non-species factors on biomass production are apparent, but which factors are driving performance differences is not clear. In order for biomass production on post-SMCRA mine sites to achieve commercial potential, factors causing the major growth differences observed in these studies must be understood and managed.

Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status

The impact of elevated CO₂, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO₂ throughout the growing season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO₂ interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO₂. At peak drought, the D × CO₂ interaction antagonistically down-regulated photosynthesis, suggesting a limited ability of elevated CO₂ to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO₂) could be explained by the main effect of experimental treatments (T, D, CO₂) and the two-factor interactions (D × CO₂, T × CO₂). The interactive responses in the experimental treatments including elevated CO₂ seemed to be linked to the realized range of treatment variability, for example with negative effects following experimental drought or positive effects following the relatively higher impact of night-time warming during cold periods early and late in the year. Longer-term experiments are needed to evaluate whether photosynthetic down-regulation will dampen the stimulation of photosynthesis under prolonged exposure to elevated CO₂.

Finding solutions for bird restoration and livestock management: comparing grazing exclusion levels

Riparian habitats in the western United States support high avian abundance and diversity and are important areas for livestock grazing, although grazing contributes to the degradation of riparian vegetation. Complete removal of livestock is generally the most beneficial for bird communities, but alternative management approaches allowing for seasonal livestock grazing may also increase avian habitat quality. Determining management approaches that integrate conservation priorities and human use has the potential to improve conditions for birds across many grazed landscapes. We anticipated that both the full and seasonal exclusion of cattle from riparian areas would result in the recovery of avian populations. To test this, we experimentally compared the effects of total cattle exclusion vs. seasonal usage on bird populations in the riparian areas of two creeks in the San Joaquin Valley, California, USA. Avian species richness and average abundance were measured over six years, from 2001 to 2006. In general, native avian abundance and richness increased in both full- and seasonal-exclosure areas, with increases compared to the pretreatment year for all years except 2005. Habitats that had complete cattle exclusion recovered more significantly, with 29% lower avian abundance in seasonally grazed habitats. There was no significant difference in avian richness between the two grazing treatments, although richness did increase over time. In addition to increases in native species, abundance of nonnative birds and brood parasites also increased significantly, with a greater avian abundance in the full-exclusion areas. A direct comparison with the Breeding Bird Survey (BBS), to further investigate annual avian population trends, explained the native species decline in 2005. This comparison revealed that observed trends were the effect of experimental treatment rather than a reflection of regional trends. Although the overall trends indicate that the full exclusion of livestock from riparian areas results in more abundant bird populations, seasonal exclusion is also a successful method for avian recovery. Land managers should consider both options in riparian areas, selecting full cattle removal for avian management only and seasonal cattle removal for situations where incorporating conservation and land use practices is advantageous.

Effects of postpartum uterine diseases on milk production and culling in dairy cows

The objective was to quantify the effect of postpartum uterine diseases on milk production and culling. Data from 2,178 Holstein cows in 6 herds enrolled in a randomized clinical trial were used. Milk production data from the first 4 Dairy Herd Improvement Association (DHIA) test-days and culling data from farm records were collected. Retained placenta (RP; ≥24 h after parturition) and metritis [≤20 d in milk (DIM)] were diagnosed by farm managers using standardized definitions. Farms were visited weekly and cows were examined at 35 and 56 (±3) DIM using endometrial cytology (cytobrush device), vaginal discharge scoring (Metricheck device), and measurement of cervical diameter by transrectal palpation. Diagnostic criteria for cytological endometritis (CYTO) and purulent vaginal discharge (PVD) were established based on a detrimental effect on subsequent reproduction. Statistical analyses were performed using linear mixed models, logistic regression models, and Cox proportional hazard models, accounting for the effects of experimental treatments and herd clustering. Milk production and culling were the outcomes. Primiparous and multiparous cows were modeled separately for milk production. Milk production of primiparous cows was unaffected by uterine diseases. The effect of metritis on milk production was variable over time in multiparous cows: it decreased production per cow by 3.7 kg at the first DHIA test, but was not different at later tests. Retained placenta decreased milk production by 2.6 kg/d in multiparous cows through the first 4 DHIA tests. The projected effects of metritis and RP in multiparous cows were reductions of 259 kg and 753 kg over 305 DIM, respectively; these effects were additive. Neither CYTO nor PVD affected milk production. Culling risks at 30 and 63 DIM were unaffected by RP and metritis. Culling hazard up to 300 DIM was unaffected by RP, metritis, CYTO, or PVD, whether or not pregnancy status, milk production, and displaced abomasum were accounted for. Uterine disease decreased pregnancy rate, which was a substantial risk factor for culling; however, if affected cows became pregnant they were not at greater risk of culling.

Effects of sagebrush treatments on multi‐scale resource selection by pygmy rabbits

AbstractThe effects of widespread sagebrush removal treatments on pygmy rabbits (Brachylagus idahoensis) are not well understood. Due to reliance on sagebrush, pygmy rabbits are among the species for which these treatments may be detrimental. Our objectives were to evaluate the effects of experimental sagebrush treatment on 8 radio‐collared pygmy rabbits between and within home range habitat selection using Monte Carlo simulation from null models. Pygmy rabbits were not extirpated from plots containing habitat treatments, and we found no evidence that treatments affected home range placement. The mean treatment distance of observed home range centers did not differ from repeated trials of random points. However, we found evidence of within home range selection against treatments from 2 of 8 rabbits located close to the treatments. The mean treatment distance of all observed locations for these 2 rabbits was greater than expected based on a null model. We also used snow tracking to show that pygmy rabbits entered treatments in 4 out of 21 trials, which was less often than expected by chance (G2 = 8.662, P = 0.003). Conservatively, sagebrush removal treatments should not be conducted on active or recently active pygmy rabbit burrows. Elsewhere near known pygmy rabbit sites, treated patches should be small and connected by untreated corridors to prevent potentially limiting movement of rabbits among the untreated habitat. © 2011 The Wildlife Society.

Evaluation of Amyloid Plaque in an Alzheimer's Disease Mouse Model with the Use of Stereological Versus Aperio Analysis

Alzheimer's disease is a progressive neurodegenerative disorder and the most common form of dementia, affecting as many as 10% of people older than the age of 65. One pathological hallmark of the disease is a buildup of beta amyloid plaques between the neurons in the brain. Transgenic mice that overexpress beta amyloid have a deposition of plaques in their brains and are often used to test hypotheses related to the effects of drug therapies on the pathogenesis of Alzheimer's disease. Various methods of histopathological analysis can be performed on brain tissue from these mouse models to determine changes in plaque deposition. One such method, stereology, involves systematic sampling of planar tissue sections to determine the properties of three-dimensional objects contained in those sections and is the standard method for quantifying plaque burden in the brain. Stereology, however, is extremely time intensive and a greater-throughput method would therefore be preferable. Aperio analysis combines slide scanning with batch image analysis techniques to speed up the histopathological analysis of tissue samples. The present results show that Aperio analysis can be used to objectively analyze the effect of experimental treatments on plaque distribution in the brain of transgenic mice and obtain results that are comparable with those seen when stereological analysis is used.

PISC Expert Team White Paper: Toward a Consistent Standard of Evidence When Evaluating the Efficacy of an Experimental Treatment From a Randomized, Active-Controlled Trial

The double-blind placebo-controlled trial is the established standard for determining the efficacy of an experimental treatment. However, there are circumstances where the use of a placebo is unethical or impractical, and active-controlled trials are a common alternative. In an active-controlled trial, the objective is typically to show that the effect of the experimental treatment is within some prespecified margin of the control effect. The margin is often chosen specifically to guarantee 50% or 75% preservation of the control effect over placebo. An implicit assumption is that a higher standard of efficacy is required when a new treatment is evaluated in an active-controlled trial. In this article, we argue that standards based on margins and/or percent preservation are inherently arbitrary and lacking in objective clinical or scientific justification. The use of these ad hoc standards introduces logical inconsistencies for regulatory evaluation such that safe and effective treatments may be denied regulatory approval. We therefore argue that active-controlled trials should not require an arbitrarily higher standard of evidence than placebo-controlled trials. We discuss how “synthesis” analyses combining the results of both an active-controlled trial and one or more historical trials can address methodological challenges and provide for adequate estimation and testing of an experimental treatment effect relative to placebo.

Efficacy of experimental treatments compared with standard treatments in non-inferiority trials: a meta-analysis of randomized controlled trials

There is concern that non-inferiority trials might be deliberately designed to conceal that a new treatment is less effective than a standard treatment. In order to test this hypothesis we performed a meta-analysis of non-inferiority trials to assess the average effect of experimental treatments compared with standard treatments. One hundred and seventy non-inferiority treatment trials published in 121 core clinical journals were included. The trials were identified through a search of PubMed (1991 to 20 February 2009). Combined relative risk (RR) from meta-analysis comparing experimental with standard treatments was the main outcome measure. The 170 trials contributed a total of 175 independent comparisons of experimental with standard treatments. The combined RR for all 175 comparisons was 0.994 [95% confidence interval (CI) 0.978-1.010] using a random-effects model and 1.002 (95% CI 0.996-1.008) using a fixed-effects model. Of the 175 comparisons, experimental treatment was considered to be non-inferior in 130 (74%). The combined RR for these 130 comparisons was 0.995 (95% CI 0.983-1.006) and the point estimate favoured the experimental treatment in 58% (n = 76) and standard treatment in 42% (n = 54). The median non-inferiority margin (RR) pre-specified by trialists was 1.31 [inter-quartile range (IQR) 1.18-1.59]. In this meta-analysis of non-inferiority trials the average RR comparing experimental with standard treatments was close to 1. The experimental treatments that gain a verdict of non-inferiority in published trials do not appear to be systematically less effective than the standard treatments. Importantly, publication bias and bias in the design and reporting of the studies cannot be ruled out and may have skewed the study results in favour of the experimental treatments. Further studies are required to examine the importance of such bias.

Comparison of Two Sampling Methods for Quantifying Changes in Vegetation Composition Under Rangeland Development

Rapid vegetation sampling methods based on visual estimation are useful for monitoring changes in rangeland vegetation composition because large spatial and temporal scales are often involved and have limited sampling resources available. Here we compared two sampling methods in their ability to detect changes in vegetation composition following rangeland development: 1) species percent cover estimates within subplots (the percent cover [PC] method) and 2) rankings of relative biomass of the 10 most abundant species across the whole plot and the ratio of two of them (the visual ranking [VR] method). Both methods were applied on 30 experimental plots at year 26 of a long-term factorial trial of five soil fertility levels and three sheep grazing intensities. Multivariate statistical methods showed significant effects of experimental treatments (fertilizer level and sheep grazing intensity) and of vegetation sampling method (VR vs. PC) on vegetation composition. Importantly, we detected no significant interactions involving sampling method, indicating that the effect of sampling method was consistent across experimental treatments. Effects of fertilizer on vegetation composition were an order of magnitude greater than the effect of sampling method, whereas the latter was twice as important as the effect of grazing. Results were robust to differential weights given to relative abundances vs. compositional changes. Differences between methods were primarily driven by the PC method giving lower abundance estimates of one species, lupin (a hybrid of Lupinus polyphyllus Lindl.), relative to the VR method. Our results support the use of the VR method as a rapid yet powerful method for monitoring changes in vegetation composition under rangeland development.

Effect of experimental treatment on GAPDH mRNA expression as a housekeeping gene in human diploid fibroblasts

BackgroundSeveral genes have been used as housekeeping genes and choosing an appropriate reference gene is important for accurate quantitative RNA expression in real time RT-PCR technique. The expression levels of reference genes should remain constant between the cells of different tissues and under different experimental conditions. The purpose of this study was to determine the effect of different experimental treatments on the expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA so that the reliability of GAPDH as reference gene for quantitative real time RT-PCR in human diploid fibroblasts (HDFs) can be validated. HDFs in 4 different treatment groups viz; young (passage 4), senescent (passage 30), H2O2-induced oxidative stress and γ-tocotrienol (GTT)-treated groups were harvested for total RNA extraction. Total RNA concentration and purity were determined prior to GAPDH mRNA quantification. Standard curve of GAPDH expression in serial diluted total RNA, melting curve analysis and agarose gel electrophoresis were used to determine the reliability of GAPDH as reference gene.ResultsHDFs with different experimental treatments exhibited diverse cell morphology with different expression of senescence-associated β-galactosidase (SA β-gal) activity. However the expression level of GAPDH was consistent in all treatment groups.ConclusionThe study demonstrated that GAPDH is reliable as reference gene for quantitative gene expression analysis in HDFs. Therefore it can be used as housekeeping gene for quantitative real time RT-PCR technique in human diploid fibroblasts particularly in studying cellular senescence.

Statistical Inference for Tumor Growth Inhibition T/C Ratio

The tumor growth inhibition T/C ratio is commonly used to quantify treatment effects in drug screening tumor xenograft experiments. The T/C ratio is converted to an antitumor activity rating using an arbitrary cutoff point and often without any formal statistical inference. Here, we applied a nonparametric bootstrap method and a small sample likelihood ratio statistic to make a statistical inference of the T/C ratio, including both hypothesis testing and a confidence interval estimate. Furthermore, sample size and power are also discussed for statistical design of tumor xenograft experiments. Tumor xenograft data from an actual experiment were analyzed to illustrate the application.

Enhancing the internal validity of entrepreneurship experiments by assessing treatment effects at multiple levels across multiple trials

Treatment effects in entrepreneurship experiments could vary significantly due to environmental uncertainty and individual heterogeneity. Drawing on critical realism, experimental replication is useful for assessing the generalizability of the treatment effects or for confirming treatment effects across diverse entrepreneurship settings. Yet, experiments in entrepreneurship have traditionally relied on single experimental trials and have not considered potential variance in treatment effects across contexts. Accounting for variance in treatment effects is even more pertinent under higher levels of environmental uncertainty. To help assess the contingent effects of treatments across contexts, we propose a set of methodological and statistical approaches for entrepreneurship researchers. Using different types of experimental replications and proposed statistical methods, one may draw inferences about treatment effects at the trial-, the treatment-, and at the individual-level. We illustrate the proposed approach using experimental replications across three randomized, post-test, experiments.

Long-term dynamics of aboveground fungal communities in a subalpine Norway spruce forest under elevated nitrogen input

As anthropogenic N deposition has been suspected to be the main reason for the decline of macromycetous sporocarp production in forest ecosystems, various N-fertilization experiments were started in the mid 1990s. The dynamics of ectomycorrhizal (root-inhabiting) and terricolous saprobic (litter-inhabiting) fungal communities were studied by exhaustive sporocarp inventories in a substitution Norway spruce (Picea abies) forest in two 256-m(2) plots sampled for periods of 1 week at 1-m(2) resolution between 1994 and 2007. N was added to the soil twice per year in one plot from the fourth year onwards. The effects of N input and time on aboveground fungal communities were assessed using redundancy analysis, principal response curves and non-parametric multivariate ANOVA. Results of this long-term experiment revealed that both ectomycorrhizal and saprobic fungal communities responded to an increase in soil N input. The ectomycorrhizal community reacted by a fast decrease in sporocarp production and in species richness, whereas the saprobic community was less affected. The response was highly species specific, especially for the saprobic community. The difference in species composition between control and fertilized plots was significant after 1year of N addition for ectomycorrhizal fungi and only after 3years for saprobic fungi. An aging effect affected sporocarp production in the whole area. For both communities, this unidirectional drift in species composition was as important as the treatment effect. This result highlights the importance of considering the respective role of treatment and year effects in long-term field experiments on fungal communities.

Finding solutions for bird restoration and livestock management: Comparing grazing exclusion levels

Riparian habitats in the western United States support high avian abundance and diversity and are important areas for livestock grazing, although grazing contributes to the degradation of riparian vegetation. Complete removal of livestock is generally the most beneficial for bird communities, but alternative management approaches allowing for seasonal livestock grazing may also increase avian habitat quality. Determining management approaches that integrate conservation priorities and human use has the potential to improve conditions for birds across many grazed landscapes. We anticipated that both the full and seasonal exclusion of cattle from riparian areas would result in the recovery of avian populations. To test this, we experimentally compared the effects of total cattle exclusion vs. seasonal usage on bird populations in the riparian areas of two creeks in the San Joaquin Valley, California, USA. Avian species richness and average abundance were measured over six years, from 2001 to 2006. In general, native avian abundance and richness increased in both full- and seasonal-exclosure areas, with increases compared to the pretreatment year for all years except 2005. Habitats that had complete cattle exclusion recovered more significantly, with 29% lower avian abundance in seasonally grazed habitats. There was no significant difference in avian richness between the two grazing treatments, although richness did increase over time. In addition to increases in native species, abundance of nonnative birds and brood parasites also increased significantly, with a greater avian abundance in the full-exclusion areas. A direct comparison with the Breeding Bird Survey (BBS), to further investigate annual avian population trends, explained the native species decline in 2005. This comparison revealed that observed trends were the effect of experimental treatment rather than a reflection of regional trends. Although the overall trends indicate that the full exclusion of livestock from riparian areas results in more abundant bird populations, seasonal exclusion is also a successful method for avian recovery. Land managers should consider both options in riparian areas, selecting full cattle removal for avian management only and seasonal cattle removal for situations where incorporating conservation and land use practices is advantageous.