scholarly journals Grassland productivity in response to nutrient additions and herbivory is scale-dependent

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2745
Author(s):  
Erica A.H. Smithwick ◽  
Douglas C. Baldwin ◽  
Kusum J. Naithani
Keyword(s):  
South African ◽  
Spatial Scales ◽  
Nutrient Concentrations ◽  
Entire Area ◽  
Nutrient Additions ◽  
P Concentration ◽  
Experimental Approaches ◽  
Grassland Productivity ◽  
One Year ◽  
Neutral Models

Vegetation response to nutrient addition can vary across space, yet studies that explicitly incorporate spatial pattern into experimental approaches are rare. To explore whether there are unique spatial scales (grains) at which grass response to nutrients and herbivory is best expressed, we imposed a large (∼3.75 ha) experiment in a South African coastal grassland ecosystem. In two of six 60 × 60 m grassland plots, we imposed a scaled sampling design in which fertilizer was added in replicated sub-plots (1 × 1 m, 2 × 2 m, and 4 × 4 m). The remaining plots either received no additions or were fertilized evenly across the entire area. Three of the six plots were fenced to exclude herbivory. We calculated empirical semivariograms for all plots one year following nutrient additions to determine whether the scale of grass response (biomass and nutrient concentrations) corresponded to the scale of the sub-plot additions and compared these results to reference plots (unfertilized or unscaled) and to plots with and without herbivory. We compared empirical semivariogram parameters to parameters from semivariograms derived from a set of simulated landscapes (neutral models). Empirical semivariograms showed spatial structure in plots that received multi-scaled nutrient additions, particularly at the 2 × 2 m grain. The level of biomass response was predicted by foliar P concentration and, to a lesser extent, N, with the treatment effect of herbivory having a minimal influence. Neutral models confirmed the length scale of the biomass response and indicated few differences due to herbivory. Overall, we conclude that interpretation of nutrient limitation in grasslands is dependent on the grain used to measure grass response and that herbivory had a secondary effect.

scholarly journals Quantifying spatial patterns of grass response to nutrient additions using empirical and neutral semivariogram models

2016 ◽  
Author(s):  
Erica A.H. Smithwick ◽  
Douglas C. Baldwin ◽  
Kusum J. Naithani
Keyword(s):  
South African ◽  
Sampling Design ◽  
Multiple Scales ◽  
Hybrid Approach ◽  
Nutrient Concentrations ◽  
Nutrient Additions ◽  
Ecological Patterns ◽  
Plot Area ◽  
One Year ◽  
Neutral Models

Disturbances influence vegetation patterns at multiple scales, but studies that isolate the effect of scale are rare, meaning that scale and process are often confounded. To explore this, we imposed a large (~3.75 ha) experiment in a South African coastal grassland ecosystem to determine the spatial scale of grass response to nutrient additions. In two of six 60 x 60 m grassland plots, we imposed nutrient additions using a scaled sampling design in which fertilizer was added in replicated sub-plots of varying sizes (1 x 1 m, 2 x 2 m, and 4 x 4 m). The remaining plots either received no additions, or were fertilized evenly across the entire plot area. We calculated empirical semi-variograms for all plots one year following nutrient additions to determine whether the scale of grass response (biomass and nutrient concentrations) corresponded to the scale of the sub-plot additions and compared these results to reference plots (unfertilized or unscaled). In addition, we calculated semi-variograms from a series of simulated landscapes generated using random or structured patterns (neutral models) and compared the semivariogram parameters between simulated and empirical landscapes. Results from the empirical semivariograms showed that there was greater spatial structure in plots that received additions at sub-plot scales, with range values that were closest to the 2 x 2 m grain. These results were in agreement with simulated semivariograms using neutral models, supporting the notion that our empirical results were not confounded by random effects. Overall, our results highlight that neutral models can be combined with empirical semivariograms to identify multi-scalar ecological patterns and this hybrid approach should be used more widely in ecological studies.

scholarly journals Quantifying spatial patterns of grass response to nutrient additions using empirical and neutral semivariogram models

2016 ◽  
Author(s):  
Erica A.H. Smithwick ◽  
Douglas C. Baldwin ◽  
Kusum J. Naithani
Keyword(s):  
South African ◽  
Sampling Design ◽  
Multiple Scales ◽  
Hybrid Approach ◽  
Nutrient Concentrations ◽  
Nutrient Additions ◽  
Ecological Patterns ◽  
Plot Area ◽  
One Year ◽  
Neutral Models

Disturbances influence vegetation patterns at multiple scales, but studies that isolate the effect of scale are rare, meaning that scale and process are often confounded. To explore this, we imposed a large (~3.75 ha) experiment in a South African coastal grassland ecosystem to determine the spatial scale of grass response to nutrient additions. In two of six 60 x 60 m grassland plots, we imposed nutrient additions using a scaled sampling design in which fertilizer was added in replicated sub-plots of varying sizes (1 x 1 m, 2 x 2 m, and 4 x 4 m). The remaining plots either received no additions, or were fertilized evenly across the entire plot area. We calculated empirical semi-variograms for all plots one year following nutrient additions to determine whether the scale of grass response (biomass and nutrient concentrations) corresponded to the scale of the sub-plot additions and compared these results to reference plots (unfertilized or unscaled). In addition, we calculated semi-variograms from a series of simulated landscapes generated using random or structured patterns (neutral models) and compared the semivariogram parameters between simulated and empirical landscapes. Results from the empirical semivariograms showed that there was greater spatial structure in plots that received additions at sub-plot scales, with range values that were closest to the 2 x 2 m grain. These results were in agreement with simulated semivariograms using neutral models, supporting the notion that our empirical results were not confounded by random effects. Overall, our results highlight that neutral models can be combined with empirical semivariograms to identify multi-scalar ecological patterns and this hybrid approach should be used more widely in ecological studies.

Dissolved organic matter as P source for biofilms in two contrasting low-order streams

2019 ◽  
Vol 193 (2) ◽  
pp. 131-142
Author(s):  
Verónica Díaz-Villanueva
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Deciduous Forest ◽  
Spatial Scales ◽  
Algal Species ◽  
Community Level ◽  
Nutrient Concentrations ◽  
Organic Substrates ◽  
One Year ◽  
Forest Streams

Forest streams receive large amounts of leaves whose leachates are an important source of dissolved organic matter (DOM), providing not only carbon but also organic nutrients to the microbial communities in streams. I carried out a field study to evaluate the effect of different DOM concentrations on the biofilm structure and functional traits in two similar forest streams belonging to the same catchment. I compared biofilm biomass and nutri- ent content throughout one year, algal species composition, and biofilm community-level physiological profiles in two streams with different DOM concentration and aromaticity. Dissolved nutrient concentrations were higher in the stream with higher DOM concentration, with a concomitant higher biofilm biomass, and there was also a temporal pattern, with higher values during the autumn. Phosphorus content in biofilms was also higher in the high DOM stream, coincidently with a higher capacity of the community to utilize organic P source (glucose-1-P) as a substrate. In contrast, the biofilms from the stream with lower DOM concentrations preferentially used N-organic substrates (amino acids and amines). These results reveal that the biofilms of forest streams make use of organic matter nutrients, so that streams with different DOM loads may differ in biofilm biomass due to changes in both bacterial and autotrophic biomass. In addition, biofilm dynamics may be related to forest phenology, as the highest OM input in this deciduous forest is represented by tree leaves, which supply DOM through leachates, and in particular, with P-rich leachates. In conclusion, different DOM concentrations in two nearby streams led to differences in the community-level physiological profile, as has been previously demonstrated at larger spatial scales in oceans, lakes and along larger rivers.

scholarly journals Insectivorous songbirds as early indicators of future defoliation by spruce budworm

2021 ◽  
Author(s):  
Marion Germain ◽  
Daniel Kneeshaw ◽  
Louis De Grandpré ◽  
Mélanie Desrochers ◽  
Patrick M. A. James ◽  
...  
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Spruce Budworm ◽  
Detection Methods ◽  
Maximum Probability ◽  
Point Count ◽  
Probability Of Presence ◽  
Time Lagged ◽  
One Year ◽  
Local Sampling

Abstract Context Although the spatiotemporal dynamics of spruce budworm outbreaks have been intensively studied, forecasting outbreaks remains challenging. During outbreaks, budworm-linked warblers (Tennessee, Cape May, and bay-breasted warbler) show a strong positive response to increases in spruce budworm, but little is known about the relative timing of these responses. Objectives We hypothesized that these warblers could be used as sentinels of future defoliation of budworm host trees. We examined the timing and magnitude of the relationships between defoliation by spruce budworm and changes in the probability of presence of warblers to determine whether they responded to budworm infestation before local defoliation being observed by standard detection methods. Methods We modelled this relationship using large-scale point count surveys of songbirds and maps of cumulative time-lagged defoliation over multiple spatial scales (2–30 km radius around sampling points) in Quebec, Canada. Results All three warbler species responded positively to defoliation at each spatial scale considered, but the timing of their response differed. Maximum probability of presence of Tennessee and Cape May warbler coincided with observations of local defoliation, or provided a one year warning, making them of little use to guide early interventions. In contrast, the probability of presence of bay-breasted warbler consistently increased 3–4 years before defoliation was detectable. Conclusions Early detection is a critical step in the management of spruce budworm outbreaks and rapid increases in the probability of presence of bay-breasted warbler could be used to identify future epicenters and target ground-based local sampling of spruce budworm.

Frost hardiness and winter photosynthesis of Thujapiicata and Pseudotsugamenzlesll seedlings grown at three rates of nitrogen and phosphorus supply

1995 ◽  
Vol 25 (1) ◽  
pp. 18-28 ◽  
Author(s):  
B.J. Hawkins ◽  
M. Davradou ◽  
D. Pier ◽  
R. Shortt
Keyword(s):  
Net Photosynthesis ◽  
Douglas Fir ◽  
Frost Hardiness ◽  
Nutrient Concentrations ◽  
Nitrogen And Phosphorus ◽  
Red Cedar ◽  
Air Temperatures ◽  
Foliar Nutrient ◽  
One Year ◽  
P Supply

One-year-old seedlings of western red cedar (Thujapiicata Donn ex D.Don) and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were grown for one season in five nutrient treatments with nitrogen (N) supplied in solution at rates of 20, 100, or 250 mg•L−1 and phosphorus (P) supplied at rates of 4, 20, or 60 mg•L−1. Growth, onset of dormancy, frost hardiness on six dates, and foliar nutrient concentrations in autumn and spring were measured. Midwinter rates of net photosynthesis and transpiration were measured at air temperatures of 4, 7, and 11 °C in seedlings from all nutrient treatments. Recovery of net photosynthesis and transpiration in whole seedlings from the three N treatments was assessed at intervals for 28 days after the seedlings were frozen to −5, −15, and −25°C. Foliar N content differed significantly among nutrient treatments and was positively correlated with supply. Mitotic activity ceased earliest in plants with low N supply. Douglas-fir seedlings in the low-N treatment also ceased height growth earliest. These differences in growth had no significant correlation with frost hardiness. No consistent differences in frost hardiness among nutrient treatments were observed. Higher rates of N and P supply resulted in higher rates of winter net photosynthesis. Net photosynthesis was reduced dramatically by night frost, with greater damage occurring at lower temperatures. Net photosynthesis recovery occurred most quickly in seedlings with the midrate of N and P supply.

The Changing State of the South African Nation

2014 ◽  
pp. 1400-1418
Author(s):  
Irina Turner
Keyword(s):  
Critical Discourse Analysis ◽  
South African ◽  
Global Scale ◽  
Critical Discourse ◽  
Wide Spread ◽  
The Core ◽  
The Media ◽  
Media Reception ◽  
Countries In Transition ◽  
One Year

The colonization of discourses (Chilton & Schäffner, 2002) is a wide-spread phenomenon of globalization and naturally affects politics. The power of business-speak over politics and the media seems to be steadily increasing. Most vulnerable to that development, which the author calls businification, seem to be countries in transition that have to assert themselves rhetorically on a global scale while keeping traditional voters content at home. In an application of critical discourse analysis, the chapter seeks to trace this businification by comparing three presidential state-of-the-nation-addresses (SoNA) of three South African presidents after one year in office (1995, 2000, and 2010). Through contextualizing these texts with their media reception from a corpus of 15 newspaper articles reporting on the speeches, the outer influences on the core text become transparent. The findings suggest a parallelism between a growing professionalism in politics and the businification of political rhetoric whose development cannot be viewed as exclusively negative.

scholarly journals Effects of Load Reductions on Phosphorus Concentrations in a Baltic Estuary—Long-Term Changes, Seasonal Variation, and Management Implications

2020 ◽  
Vol 44 (1) ◽  
pp. 30-43
Author(s):  
Jakob Walve ◽  
Maria Sandberg ◽  
Ragnar Elmgren ◽  
Christer Lännergren ◽  
Ulf Larsson
Keyword(s):  
Surface Water ◽  
Spring Bloom ◽  
Point Sources ◽  
Nutrient Concentrations ◽  
Nutrient Loads ◽  
P Concentration ◽  
Source Contributions ◽  
A Minor ◽  
Autumn And Winter

AbstractNutrient concentrations in coastal waters are influenced not only by land runoff, point sources, and water exchange with the sea but are also modified by settlement to and release from sediments. This complicates evaluation of measures to reduce nutrient loads. We used a mass-balance box model to calculate long-term (1968–2015) and seasonal source contributions to phosphorus (P) concentrations and cycling in the stratified Stockholm inner archipelago (IA), Baltic Sea. A drastic reduction of sewage P loads in the early 1970s reduced sewage from the major to a minor P source. Further P load reductions in the 1990s cut the direct contribution from the sewage point sources to the annual mean surface water P concentration from 10 μg l−1 (25%) to < 4 μg l−1 (12%). The largest contributions to the surface water P concentration are now (from 1996) inflowing seawater (37%), freshwater (25%), and P recycling from sediments below 20 m depth (26%). Variations in freshwater flushing give higher P concentrations in dry years, when dilution of P inputs from sediments and sewage is small, while in wet years, these inputs are greatly diluted. Source-partitioned phosphate uptake shows that the spring bloom is fueled mainly by P of seawater and freshwater origin, while the contribution from sewage point sources is minor. Since sediment P release is mostly recycled P from the settled spring bloom, the P inputs from seawater and freshwater are now the major drivers of the IA P cycle. Recycling of P from sediments boosts surface water P concentrations in autumn and winter, affecting management target concentrations.

Chemical Characterization of Environmental Samples after Oil Spill in Iguassu River, Parana, Brazil, July/2000

2003 ◽  
Vol 2003 (1) ◽  
pp. 579-588
Author(s):  
Maria de Fátima Guadalupe Meniconi ◽  
Irene Terezinha Gabardo ◽  
Silvana Maria Barbanti ◽  
Nelson Luna Caicedo
Keyword(s):  
Monitoring Program ◽  
Chemical Characterization ◽  
Hydrocarbon Contamination ◽  
Concentration Data ◽  
Entire Area ◽  
Monitoring Wells ◽  
South Of Brazil ◽  
One Year ◽  
The Impact ◽  
Spilled Oil

ABSTRACT On July 16, 2000, a rupture of a pipeline occurred in the Scraper area of the PETROBRAS refinery located in Araucaria, in the state of Parana, south of Brazil. This resulted in the spill of approximately 4,000m3 (1,060,000 gallons) of a crude oil (Cusiana − 41°API). The spilled oil spread over part of the refinery area, affecting the wetlands that are crossed by the Arroio Saldanha creek before discharging into the Barigui River, which is a tributary of Iguassu River. This entire area crossed by the creek is referred to as Point Zero (PO). This paper presents the chemical data of 2 monitoring programs: the Barigui, Iguassu and Arroio Saldanha Rivers, and the groundwater of Point Zero. The programs were carried out in 2 phases: for 3 months immediately after the spill and 1 year later. They included the analyses of BTEX, TPH, PAH, n-alkanes, UCM and biomarkers for the water and sediment samples. The rivers program encompassed 13 stations along Barigui and Iguassu Rivers and 1 station at Arroio Saldanha Creek. The results in water and sediments demonstrated the efficiency of the recovering of the spilled oil from the water. That suggested that the impact of the spill on the Barigui and Iguassu Rivers was of a short duration after the spill. On the other hand, the hydrocarbon concentration data for Arroio Saldanha Creek during the 3 months after the spill revealed high levels of hydrocarbon contamination, which corroborated the visual inspection. The groundwater monitoring program in the terrestrial area of Point Zero was initiated shortly after the spill. The groundwater program included about 80 monitoring wells (piezometers) installed, along the Arroio Saldanha Creek and in the wetlands crossed by the creek. It could be observed that BTEX and TPH groundwater concentrations decreased significantly after one year.

Field Determination of the Critical Nutrient Concentrations for Cladophora in Streams

1976 ◽  
Vol 33 (1) ◽  
pp. 85-92 ◽  
Author(s):  
S. L. Wong ◽  
B. Clark
Keyword(s):  
Plant Tissue ◽  
Stream Water ◽  
Dry Weight ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Nutrient Concentrations ◽  
P Concentration ◽  
P Content ◽  
Waste Load ◽  
Total P

Many streams in southern Ontario experience excessive seasonal growth of aquatic plants such as Cladophora and Potamogeton. A direct relation, with a regression coefficient of 0.87, was observed between ambient P concentration in the water and P content of plant tissue in six rivers. Critical or growth controlling total P concentration of 60 μg/liter in stream water and 1.6 mg/gram dry weight in plant tissue were determined. Unlike P, no significant correlation was observed between N content of plant tissue and N concentration in water. The correlation of total P with plant growth can be used to estimate the waste load which would result in maximum growth rate of Cladophora.

Influence of Glomus fasciculatus mycorrhizae on some physical and chemical characteristics of Platanus occidentalis seedlings

1980 ◽  
Vol 58 (14) ◽  
pp. 1601-1606 ◽  
Author(s):  
P. E. Pope
Keyword(s):  
Root Colonization ◽  
Dry Weight ◽  
Nutrient Concentrations ◽  
Nutrient Level ◽  
Soil P ◽  
Platanus Occidentalis ◽  
P Concentration ◽  
Glomus Fasciculatus ◽  
Foliar Phosphorus ◽  
Total Dry Weight

Inoculation of Platanus occidentalis seedlings with Glomus fasciculatus significantly increased plant dry weight and foliar phosphorus (P) concentration when compared with the uninoculated control. After 12 weeks inoculated seedlings were 73% taller and 200% greater in total dry weight. The largest dry weight increase was recorded for foliage (212%) followed in order by stem (202%) and root (171%). Averaged overall nutrient treatments, foliar P concentration was 22% greater for the inoculated seedlings. Nutrient regimes representing 1×, 2×, and 4× Hoagland's No. 2 solution and a control significantly influenced seedling height, dry weight, percentage of foliar N, P, and K, and the degree of root colonization. Maximum growth and foliar nutrient concentrations were associated with the 2× Hoagland's nutrient regime followed in order by the 4× and 1× nutrient treatments and the control. Degree of root colonization by G. fasciculatus increased from 42% of the root length in the unfertilized control to 48% at the 1× Hoagland's regime and sharply declined at the 2× and 4× levels. Total dry weight of inoculated seedlings was significantly greater than the noninoculated control at each nutrient level. Incremental differences were 2.71, 4.03, 4.37, and 3.08 g for the control, 1×, 2×, and 4× Hoagland's nutrient regimes, respectively. Seedling growth attributed to G. fasciculatus is directly related to degree of mycorrhizal colonization and inversely related to the amount of extractable soil P.

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