Positive Effect Of Fertilization Research Articles

Resilience of maize, wheat, and soybean cropping systems as affected by fertilization: Analysis of a long‐term field network

AbstractElucidating how different fertilization treatments affect the resilience of farming systems and the environmental adaptability of agricultural crops is relevant to assess their efficacy as a strategy for minimizing yield fluctuations and supporting global food security. The aim of this work was to compare the effects of fertilization practices and to distinguish the effect of macronutrients on the resilience of maize, wheat, and soybean cropping systems. A long‐term experiment involving the three crops and five fertilization treatments (control without fertilization, nitrogen and sulphur fertilization, phosphorus and sulfur fertilization, nitrogen and phosphorus fertilization, nitrogen, phosphorus and sulfur fertilization) was conducted for 19 years in the Pampean region (Argentina) that includes five study sites. The four combinations of nutrient additions increased crop yields in unfavorable environments, which indicates that even in adverse years, fertilization was a valid tool to sustain yield performance. The Finlay and Wilkinson regression slopes in maize and full‐season soybean did not differ between fertilization treatments, which suggests that fertilization did not change crop adaptation to the environment and that the observed positive effect of fertilization in unfavorable environments was maintained along the environmental gradient. In contrast, wheat and double‐cropped soybean were able to capitalize on the environmental conditions of favorable years, as shown by the progressive increases in yields as the environment became more favorable. Maize had the highest response to nitrogen, whereas wheat and double‐cropped soybean exhibited the highest responses to phosphorus and sulfur, respectively. Our findings are useful to extract guidelines that may lead to greater resilience through fertilization management practices.

Nitrogen fertilization of ‘I-214’ poplar trees with urea and different slow-release fertilizers: Yield, economic and environmental aspects

With an adequate cultivation methodology, in suitable environments, hybrid poplars can produce over 200–210 m3 ha−1 of wood in 10 years (with 278 trees ha−1). Some cultural inputs are fundamental for good yields, some others like fertilization can be evaluated because in the face of high environmental and economic costs they do not always increase the stand productivity. The purpose of this work is to show the variability of the poplar response to N fertilization and make a simple environmental and economic evaluation of this cultural practice. Four poplar trials with clone ‘I-214’ have been cultivated in different sites of Northern Italy and fertilized with Urea and other five N slow-release fertilizer and compared with no-fertilized plots. Growth and pedo-climatic data were collected. For the environmental and economic evaluation data were collected thought bibliography, dealers and farmers interviews. The trees response to N input can vary from no response up to a statistically greater yield; this variability was documented both between site and site, and within the same site between product and product. The environmental impact of the sole N fertilization input is always negative (net atmosphere CO2 eq. emissions), due to the high emissions for production; the economic income can vary from a loss of money, (no positive effect of fertilization), to an interesting net gain due to increase of yield. The N fertilization of poplar stands is a practice with high economic and environmental costs that it must be assessed on a case-by-case basis.

YIELD OF WINTER BARLEY DEPENDING ON MINERAL NUTRITION

The article presents the results of studies of the influence of mineral fertilizers on the yield of winter barley in the Western Forest-Steppe.
 It has been found that grain yield depends on providing plants with mineral nutrients throughout the growing season. The results of scientific research on the influence of mineral nutrition on seed germination, plant survival during the growing season, grain yield and structure of winter barley cultivated on gray podzolic soils in the Western Forest-Steppe are described. The authors of the research studied different doses of mineral fertilizers: 1) without fertilizers (control); 2) N30Р30К30; 3) N60Р60К60; 4) N90Р90К90.
 A decrease in field germination by 1.1–2.3 %, with an increase in the level of mineral nutrition was determined.
 The positive effect of mineral fertilization on the survival of winter barley has been proved. The lowest level of plant survival was in the areas without fertilizers, and the highest – under application of mineral fertilizers in the norm N90Р90К90.
 The positive effect of fertilization on the number of productive stems, the weight of grain from the ear and the number of grains in the ear was demonstrated. A positive correlation was established between fertilizer and the number of grains in the ear (r = 0.96) and fertilizer and grain weight from the ear (r = 0.77). It was found that the studied rates of fertilizers were effective for the nutritional regime of winter barley agrocenosis in the Western Forest-Steppe. The optimal dose of fertilizers which ensures maximum grain yield was determined. Application of phosphorus and potassium fertilizers (Р90К90) for plowing and nitrogen (N30+30+30) in three steps: during the restoration of spring vegetation, in the phase of tube emergence and earing provided a significant increase in yield as compared to control (without fertilizers) and options N30Р30К30 and N60Р60К60.

Quarter of a century of forest fertilization and liming research at the Department of Silviculture in Prague, Czech Republic

Abstract Fertilization and liming began to be used in forestry at the beginning of the 20th century in order to increase growth, for improvement of health status or higher resistance to biotic and abiotic factors. The review summarizes results of 48 studies of forest fertilization, nutrition and liming published in scientific journals by authors of Department of Silviculture in Prague over the past more than 20 years. They deal mainly with monitoring of the effect of fertilization and liming applied during planting or shortly after planting of 18 tree species. Moreover, the results of fertilization in older stands are presented. Separate chapters deal with enhancing substrates (soil conditioners and phytohormones). All forest vegetation ranges are covered, from lowland forests to the subalpine belt of grass vegetation in 11 Natural Forest Areas. Forest fertilizing and liming proved beneficial according to most of the studies. The use of fertilizers can be detected in soils after decades. On the other hand, only in a minority of cases was fertilization reflected in the chemistry of the assimilation apparatus and other parts of the trees for a longer period. The main positive effect of fertilization and liming was increase of tree growth and foliation and decrease of mortality and yellowing symptoms. Inconsistent results were documented in some cases, especially for brassinosteroids and alginite compared to good results in slow release fertilizer done by spot-application. The type of product, concentration, time and method of application play an important role in the appropriate use of fertilization and liming.

Forest management to increase carbon sequestration in boreal Pinus sylvestris forests

Background and aimsForest management towards increased carbon (C) sequestration has repeatedly been suggested as a “natural climate solution”. We evaluated the potential of altered management to increase C sequestration in boreal Pinus sylvestris forest plantations.MethodsAt 29 forest sites, distributed along a 1300 km latitudinal gradient in Sweden, we studied interactive effects of fertilization and thinning on accumulation of C in standing biomass and the organic horizon over a 40 year period.ResultsAbstention from thinning increased the total C stock by 50% on average. The increase was significant (14% on average) even when C in the removed timber was included in the total ecosystem C pool. Fertilization of thinned stands increased stocks similarly regardless of including (11%) or excluding (12%) removed biomass, and fertilization combined with abstention from thinning had a synergistic effect on C stocks that generated an increase of 79% (35% when removed timber was included in the C stock). A positive effect of fertilization on C stocks was observed along the entire gradient but was greater in relative terms at high latitudes. Fertilization also reduced soil respiration rates.ConclusionTaken together, our results suggest that changed forest management practices have major potential to increase the C sink of boreal forests. Although promising, these benefits should be evaluated against the undesired effects that such management can have on economic revenue, timber quality, biodiversity and delivery of other ecosystem services.

Effect of Bio and chemical Fertilizers on some physiological traits and yield of Arugula

A study was conducted in Erbil agricultural research directorate protected plastic tunnel to investigate the effect of five fertilization types; biofertilizer; locally prepared compost; manufactured compost; chemical fertilizer (DAP); and no fertilizer (control) on some physiological, yield traits of Arugula and some soil properties. Results indicated significant increase of green harvesting leaves dry weight in four cutting processes, leaf area, plant height, number of branches per plant, and chlorophyll content when arugula plants treated with different types of fertilizers compared to no fertilizer plots. Manufactured compost produced highestseed yield 1.98 (t. ha-1) comparing to other fertilizer treated plots and the lowest seed yield was 1.04 (t. ha-1) under no fertilization conditions. All yield component data revealed the positive effect of fertilization on arugula yield, straw and biological yield were at higher levels under local and manufactured compost as well as DAP fertilization treatments. The significant effect of fertilization enhanced chemical characteristics of arugula seeds data of nitrogen, phosphorus potassium, protein, oil percentage and poly phenol content comparing to no fertilizers treatment. Soil chemical characteristics were elevated after 45 days from finishing the study which insures the importance of organic fertilizers effect on soil and environment. Taste panel declare differences in leaf pungent taste, leaf texture and color according to fertilization type. Levels of positive effect of using fertilizers on fixed oil yield was from highest to lowest Manufactured compost, Local compost, DAP, Biofertilizer and no fertilizer (control).

Forage yield of orchard grass (Dactylis glomerata L.) under different fertility levels on a karewa upland of Kashmir Himalaya

The Union Territory of Jammu and Kashmir, with less than 4 % of its cultivable area under fodder crops, produces green fodder that is 30-40 % deficient than the demand. This shortage of fodder is the major cause of low productivity of the livestock in the hilly areas. Oat and berseem are the major fodder crops that are grown on about 25,000 hectares of land. Orchard grass or cocksfoot (Dactylis glomerata L.) is one of the important temperate perennial grasses with high productivity, forage quality, cold, drought and shade tolerance. Scanty information is available regarding the effect of nutrient management on forage productivity of orchard grass. Therefore, different fertility levels were evaluated to see the effect on different growth parameters and yield of Dactylis glomerata L. The study consisted of eight treatments: T1= NPK @ 100, 60, 40 kg/ha, T2= NPK @ 80, 45, 30 kg/ha, T3= NPK @ 60, 30, 20 kg/ha, T4= NPK @ 75 % 0f T1+ 25 % organic, T5= NPK @ 75 % of T2+ 25 % organic, T6= NPK @ 75 % of T3+ 25 % organic, T7= FYM @ 20 t/ha and T8= control (No fertilizer). Highest plant height (119.67 cm), number of tillers (484.33/m row), leaf-stem ratio (0.81), green fodder yield (21.43 t/ha) and dry fodder yield (7.97 t/ha) were recorded in the treatment T1 (NPK @ 100, 60, 40 kg/ha) followed by T2 and T4. Higher plant height, tiller number, leaf-stem ratio and consequently green and fodder yield in T1, T2 and T4 may be attributed to positive effect of fertilization particularly nitrogen and higher responsiveness of orchard grass to fertilization.

Can fertilization be a driver of rubber plantation intensification?

Improving the productivity of existing rubber plantations is necessary to cope with the growing demand for natural rubber (NR) while limiting the environmental and social impacts linked to the expansion of rubber cultivation at the expense of natural ecosystems and food crops. The effect of fertilization on NR yield is still unclear and is poorly documented particularly in Thailand, the world leader in NR production. Hence, the main objective of this study was to re-assess the possible effects of fertilization on the yield of intensively managed rubber plantations in Thailand. Our main hypothesis was that the effect of fertilization would be higher with intensive latex harvesting practices (high tapping frequency with ethylene stimulation). To test this hypothesis, we set-up a split-plot experiment with four fertilization doses (T1, no fertilization, T2, T3, T4, respectively low, medium and high doses of NPK fertilizer) and two tapping systems (S/2 d2 with and without ethylene stimulation). Here, we present the results of the first three years on dry rubber yield, latex metabolism assessed with the latex diagnosis method, and latex and rubber properties related to their technological properties. Our results showed a positive effect of fertilization on yield from the first year, but the effect was only statistically significant (p < 0.05) in the third year. The maximum effect of fertilization (+13%) compared to the control treatment (T1) was obtained with the highest dose of fertilizer (T4). Cumulatively over the 3-year period, the increase in yield was +5% with the T2 dose, and +8% with the T3 and T4 dose. Contrary to our main assumption, we observed no interaction between fertilization and ethylene stimulation. Latex diagnosis revealed that the effect of fertilization on yield was linked with a direct effect on latex metabolism mainly through an increase in inorganic phosphorus content (Pi). Finally, we observed no detrimental effect of the fertilizer treatments on latex and rubber quality. We can thus conclude that increasing latex yield through fertilization combined with intensive tapping does not involve any identified risks for the quality of rubber. Taken together, our results demonstrate that fertilization can help increase the yield of rubber plantations where intensive latex harvesting is practised. However, in a context of low NR prices for rubber farmers, the economic return of a +8% increase in yield is questionable. Our trial is continuing to assess the long term effects of the fertilization on yield as well as on the growth and nutritional status of the trees, and the nutrient balance of the plantation.

Twenty-six years of chemical fertilization decreased soil RubisCO activity and changed the ecological characteristics of soil cbbL-carrying bacteria in an entisol

Soil autotrophic bacteria are important for sequestrating atmospheric CO2 and thus contribute to the global carbon cycle. However, information is limited on how chemical fertilization can alter the composition of soil autotrophic bacteria. In this study, the cbbL gene (a key gene in the Calvin-Benson-Bassham cycle that encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RubisCO) was used to study the abundance and composition of autotrophic bacteria in an entisol with 26 years of continuous fertilization. In this process, five chemical fertilization regimes were examined: without fertilization control (CT), nitrogen and phosphorus fertilization (NP), N and potassium fertilization (NK), PK fertilization (PK), and NPK fertilization (NPK). The results showed that after the 26-year (1991–2017) period, the CT with a neutral pH (7.55) had a higher RubisCO activity than did the chemical fertilizer treatments, but the cbbL abundance was the lowest under CT. Soil RubisCO activity positively correlated with soil pH (R2 = 0.67, P < 0.001); soil cbbL abundance significantly positively correlated with soil available N (R2 = 0.54, P < 0.01) and significantly negatively correlated with pH (R2 = 0.30, P < 0.05). Meanwhile, the soil RubisCO activity significantly negatively correlated with cbbL abundance (R2 = 0.67, P < 0.001). In addition, the alpha-diversity of cbbL was lowest under CT, indicating a positive effect of fertilization on the soil cbbL diversity. In conclusion, a 26-year long-term chemical fertilization changed the community structure of soil cbbL-carrying bacteria, and soil pH and available N played crucial roles in controlling the ecological properties of soil cbbL-carrying bacteria.

The effects of fertilization on the health status, nutrition and growth of Norway spruce forests with yellowing symptoms

ABSTRACTWe studied the effects of magnesium (Mg) NPK fertilizer applied in 2000 to maturing Norway spruce (Picea abies /L./ Karst.) stands with yellowing symptoms and situated on poor acidified soils in the Šumava mountains (the Czech Republic). Long-term defoliation, nutrient content in the foliage and diameter increment were evaluated in three specific variants: yellowing trees, trees without yellowing symptoms and fertilized trees. The results indicate differences in soil characteristics, nutrient content and radial growth with response to climate. Fertilization increased Mg content and base saturation in the soil and decreased the amount of exchangeable aluminum and hydrolytic acidity. Differences were significant especially in magnesium, calcium and phosphorus contents in the foliage of yellowing trees. There was also a significant difference in manganese content; yellowing trees showed deficiency in comparison with both fertilized and unfertilized healthy trees. Two years after the initial fertilization (to present), defoliation and yellowing symptoms in the unfertilized yellowing trees were more pronounced compared to other variants. These symptoms were more influenced by fertilization than foliation. The duration of significant positive effects of fertilization on diameter increment lasted for a shorter time than the effect on foliage. Simultaneously, higher sensitivity to climatic factors was observed in the fertilized trees.

Shifting from a fertilization-dominated to a warming-dominated period.

Carbon dioxide and nitrogen fertilization effects on ecosystem carbon sequestration may slow down in the future because of emerging nutrient constraints, climate change reducing the effect of fertilization, and expanding land use change and land management and disturbances. Further, record high temperatures and droughts are leading to negative impacts on carbon sinks. We suggest that, together, these two phenomena might drive a shift from a period dominated by the positive effects of fertilization to a period characterized by the saturation of the positive effects of fertilization on carbon sinks and the rise of negative impacts of climate change. We discuss the evidence and processes that are likely to be leading to this shift.

Translocation of Trace Elements from Sewage Sludge Amendments to Plants in a Reclaimed Area.

The goal of the study was to evaluate bioaccumulation of trace elements in plants grown in post-mining soils amended with the biosolids material. Phaseolus vulgaris was investigated on the laboratory scale, and a mixture of grasses, Melilotus albus, Beta vulgaris, Zea mays L. and Miscanthus × giganteus were evaluated on the field scale. The results of the research showed that P. vulgaris fertilized with the Carbocrash substrate was able to grow. In addition, growth was enhanced following stimulation with gibberellic acid. Transfer of trace elements should be evaluated on the plot scale. Therefore, we monitored the level of trace elements on an experimental plot in a reclaimed area. Crops plants were sown in multi-year periods. During the growing season the mixture of grasses and crop plants had a low bioaccumulation factor, which also showed a positive effect of fertilization with the Carbocrash substrate.

Scale-dependent bi-trophic interactions in a semi-arid savanna: how herbivores eliminate benefits of nutrient patchiness to plants.

The scale of resource heterogeneity may influence how resources are locally partitioned between co-existing large and small organisms such as trees and grasses in savannas. Scale-related plant responses may, in turn, influence herbivore use of the vegetation. To examine these scale-dependent bi-trophic interactions, we varied fertilizer [(nitrogen (N)/phosphorus (P)/potassium (K)] applications to patches to create different scales of nutrient patchiness (patch size 2 × 2 m, 10 × 10 m, or whole-plot 50 × 50 m) in a large field experiment in intact African savanna. Within-patch fertilizer concentration and the total fertilizer load per plot were independently varied. We found that fertilization increased the leaf N and P concentrations of trees and grasses, resulting in elevated utilization by browsers and grazers. Herbivory off-take was particularly considerable at higher nutrient concentrations. Scale-dependent effects were weak. The net effect of fertilization and herbivory was that plants in fertilized areas tended to grow less and develop smaller rather than larger standing biomass compared to plants growing in areas that remained unfertilized. When all of these effects were considered together at the community (plot) level, herbivory completely eliminated the positive effects of fertilization on the plant community. While this was true for all scales of fertilization, grasses tended to profit more from coarse-grained fertilization and trees from fine-grained fertilization. We conclude that in herbivore-dominated communities, such as the African savanna, nutrient patchiness results in the herbivore community profiting rather more than the plant community, irrespective of the scale of patchiness. At the community level, the allometric scaling theory’s prediction of plant—and probably also animal—production does not hold or may even be reversed as a result of complex bi-trophic interactions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-016-3627-0) contains supplementary material, which is available to authorized users.

Response of Boreal Jack Pine (Pinus banksiana Lamb.) Stands to a Gradient of Commercial Thinning Intensities, with and without N Fertilization

This study examines tree and stand response to a gradient of commercial thinning intensities and nitrogen fertilization (200 kg N ha−1) in nine jack pine (Pinus banksiana) stands of Eastern Canada over a period of 14 years. Thinning intensity ranged from 0% basal area removal in control plots to 64% in thinned plots. Tree diameter increment, absolute and relative volume increment and mean volume increased with thinning intensity and were higher in fertilized plots. Individual tree response depended on tree diameter, with smallest trees exhibiting highest relative volume increment to thinning intensity. Stand basal area increment was positively associated to initial stand basal area and negatively to stand age. In thinned and fertilized plots, stand volume increment was higher and natural mortality lower than in fertilized only and unfertilized control plots over the 5–14 year period after thinning. However, the positive effect of fertilization on tree volume increment decreased with thinning intensity. Despite positive individual tree growth responses to thinning and fertilization, residual stand volume increment decreased with increased thinning intensity in both fertilized and unfertilized plots. While total cumulative stand volume (harvested + residual) also decreased with thinning intensity in unfertilized plots, comparable total volumes were observed in fertilized + thinned and unthinned control plots. Nitrogen fertilization in the years following commercial thinning enhanced the benefit of thinning on these relatively poor sites by increasing tree diameter growth, lowering mortality, and increasing total stand merchantable volume compared to unfertilized thinned stands.

Long-term effects of experimental fertilization and soil warming on dissolved organic matter leaching from a spruce forest in Northern Sweden

Nitrogen deposition and increasing temperature are two of the major large-scale changes projected for coming decades and the effect of this change on dissolved organic matter is largely unknown. We have utilized a long-term fertilization and soil warming experiment in Northern Sweden to study the effects of increased nutrient levels and increased temperature on DOC transport under the O horizon. The site is N limited and mean annual temperature 2°C. Experimental fertilization with ammonium nitrate and a physiological mixture of other macro- and micro-nutrients has been going on for 22years and soil warming, 5°C above ambient soil temperature for 14years, prior to the study. Experimental plots have been irrigated to avoid drying and we also studied the effect of this long-term irrigation on DOC by establishing control plots receiving no irrigation.DOC concentrations and fluxes under the O horizon were approximately 50% higher in fertilized plots than in non-fertilized control plots. We did not find any statistically significant effect of soil warming. There was a statistically significant effect of long-term irrigation on DOC with higher DOC concentration and fluxes in irrigated plots than in plots without irrigation. There were no major effects on DOC quality measured by specific UV absorbance. Fertilization approximately doubled soil organic matter stocks in the O horizon, whereas there were no such effects of warming or irrigation on soil organic matter amounts. There was no statistically significant treatment effect on DOC collected from the B horizon. We hypothesize that the positive effect of fertilization on DOC is related to increased soil C stocks.

Growth response of Alnus viridis to application of crushed limestone and amphibolite and forestry potential of the species in harsh acidic mountain sites

An experiment with seedlings of Alnus viridis was established on a clear-felled tract situated on a summit tableland of the Jizersk&amp;eacute; hory Mts. (central Europe, Czech Republic) at an altitude of 980 m a.s.l. The aims of the experiment were (i) to evaluate the response of A. viridis to the application of a basic mixture containing crushed limestone and amphibolite and (ii) to assess the growth potential of the species in a poor acidic site under climatically harsh conditions. Alnus viridis showed a good growth performance and survival rate, its initial response to fertilization was positive. The height growth and expansion of crowns were slightly but significantly stimulated by the treatment, the survival rate was also increased, though not significantly. The amendment application temporarily increased the foliar Ca and Mg concentrations. The content of foliar P, of the most deficient macroelement, was not improved by the treatment. However, the positive effect of fertilization was short-lasting and unconvincing from the aspect of practical use. In the second half of the reference period the control started to gain on the fertilized variant and as for mean height and crown diameter, both variants got almost equalized eight growing seasons after the treatment.

Stimulating the growth of trees with ashes of various biofuels (wood, peat) on a cutaway peatland

Puittaimede kasvu stimuleerimine erinevate biokütuste (puit, turvas) tuha liikidega ammendatud freesturbaväljal The aim of the study was to investigate the effect of fertilization on the growth of Silver birch Betula pendula Roth and Scots pine Pinus sylvestris L. seedlings on a cutaway peatland (Ulila, 58°22'N, 26°26'E). Five treatments were established: wood ash (10 000 and 5000 kg/ha), peat and wood ash mixture (10 000 and 5000 kg/ha) and control (unfertilized field). Results of analysis showed that the pH of peat in the cutaway peatland was before treatment 3.5 and it rose after fertilization by up to 0.7 units by the end of the first growing season. The treatment with 10 000 kg/ha of wood ash gave the best results: the annual height increment of Silver birches during the first growing season after fertilization was 4.5 times higher and that of Scots pines 1.1 times higher than control. In the second growing season after fertilization the increment was respectively 16.3 and 3.3 times higher than control. The root collar diameters of Silver birches were 4.4 time larger these of Scots pines 2.1 times larger than control. Scots pine needles were 2.2 times longer than control and the leaf area of the Silver birches was 6 times larger than control, which also shows a positive effect of fertilization. Peat ash treatment was also favourable, although its effect was much smaller than the effect of wood ash.

The impact of forest fertilization on growth of mature Norway spruce affected by Sirococcus shoot blight

The effects of forest fertilization and Sirococcus shoot blight on growth of mature Norway spruce ( Picea abies (L.) Karst.) were studied in a field experiment. The single tree fertilization experiment was established with 144 sample trees in the year 2000. These trees were selected among the dominant and co-dominant trees of the stand in a way that half of the trees exhibited symptoms of Sirococcus shoot blight and the other half did not. One-third of the sample trees were fertilized with dolomitic lime, one-third with kieserite and gypsum and one-third were left unfertilized as control. The treatments were randomly assigned to the sample trees. As the experimental design became unbalanced due to tree mortality caused by bark beetle infestation final analyses were performed with the volume growth data of 125 sample trees only. An analysis of covariance was used to evaluate the effect of fertilization and Sirococcus shoot blight on volume growth. The average volume increment of the period 1977–1980 was used as a covariate attribute, assuming that during this period growth was not yet affected by Sirococcus shoot blight. Indeed an effect of Sirococcus shoot blight on growth turned out to start after 1980 and the analysis revealed that over the whole period 1981–2006 trees with shoot blight symptoms had a significantly lower increment. The increment reduction of the nonfertilized trees by Sirococcus was 7.46 ± 2.90 % in 1981 and was continuously increasing with time to 37 ± 3.78 % by the year 2000. A significant positive effect of fertilization was only found for the kieserite + gypsum variant from 2002 to 2006, with the highest surplus increment in 2004 with 31.6 ± 15.2 %, calculated as average over the diseased and healthy group. However, a mitigation of the Sirococcus-caused increment loss via fertilization with kieserite and gypsum was statistically significant only for the year 2003. A moderate relationship between basal area increment and disease severity was found, indicating decreasing basal area increment with increasing disease severity.

Impacts of Climate Warming and Nitrogen Deposition on Alpine Plankton in Lake and Pond Habitats: an In Vitro Experiment

ABSTRACTThe combined effects of multiple ecological stressors determine the net impact of global change on environmentally sensitive alpine and polar environments. For example, climate warming and nitrogen deposition both increasingly affect ecosystems at high elevations. We hypothesized that the net impact of warming and nitrogen on alpine plankton differs between consumers and producers because of the greater environmental sensitivity of higher trophic levels. Also, we expected that habitat conditions would mediate the responses of plankton to these two stressors as sediments function as ecological buffers against environmental change. These hypotheses were tested in a growth chamber by applying temperature (8 vs. 15°C) and nitrogen (200 vs. 1000 µg N L−1) treatments to a planktonic alpine community in the presence and absence of sediments obtained from Pipit Lake, Banff National Park, Alberta. A significant nitrogen-temperature interaction affected phytoplankton abundance because the positive effect of fertilization depended on warming. Warming also amplified the effect of nitrogen on herbivores while suppressing the fecundity of omnivores. The presence of sediments suppressed the positive effect of warming on herbivores, but stimulated omnivores. The observed prevalence of non-additive effects highlights the strong potential for global change causing future ecological surprises in alpine environments.

Interacting effects of elevated CO2, nutrient availability and plant species on a generalist invertebrate herbivore

AbstractBy affecting plant growth and phytochemistry elevated CO2 may have indirect effects on the performance of herbivores. These effects show considerable variability across studies and may depend on nutrient availability, the carbon/nutrient‐balance in plant tissues and the secondary metabolism of plants. We studied the responses to elevated CO2 and different nutrient availability of 12 herbaceous plant species differing in their investment into secondary compounds. Caterpillars of the generalist herbivore Spodoptera littoralis were reared on the leaves produced and their consumption and growth rates analysed. Elevated CO2 resulted in a similar increase of biomass in all plant species, whereas the positive effect of fertilization varied among plant species. Specific leaf weight was influenced by elevated CO2, but the effect depended on nutrient level and identity of plant species. Elevated CO2 increased the C/N ratio of the leaves of most species. Caterpillars consumed more leaf material when plants were grown under elevated CO2 and low nutrients. This indicates compensatory feeding due to lower tissue quality. However, the effects of elevated CO2, nutrient availability and plant species identity on leaf consumption interacted. Both the effects of CO2 and nutrient availability on the relative growth rate of the herbivore depended on the plant species. The feeding rate of S. littoralis on plant species that do not produce nitrogen‐containing secondary compounds (NCSC) was higher under low nutrient availability. In contrast, in plants producing NCSC nutrient availability had no effect on the feeding rate. This suggests that compensatory feeding in response to low nutrient contents may not be possible if plants produce NCSC. We conclude that elevated CO2 causes species‐specific changes in the quality of plant tissues and consequently in changes in the preferences of herbivores for plant species. This could result in changes in plant community composition.