Selective foraging by moose on hardwoods and avoidance of conifers alters community composition and structure, which in turn can affect nutrient cycles and pro- ductivity. The effect of moose browsing on the nutrient cycles of boreal forests was studied using three 40-yr-old enclosures on Isle Royale, Michigan. Two alternative mechanisms by which moose affect ecosystems were tested: (1) moose depress both the quantity and quality of litter return to the soil, and hence N mineralization and net primary productivity, by browsing on hardwoods and avoiding conifers; (2) moose stimulate N mineralization, and hence net primary productivity, by opening the canopy and by dropping fecal pellets. Soil nutrient availability and microbial activity, including exchangeable cations, total car- bon and nitrogen, nitrogen mineralization rates, and microbial respiration rates, were uniformly higher in exclosures than outside. These differences were more significant where browsing intensity was high and less often significant where browsing intensity was low. N mineralization in browsed plots declined with increasing moose consumption rates. Net primary production in enclosures and browsed plots was strongly correlated with N min- eralization. N mineralization in turn was positively correlated with litter N return and negatively correlated with litter cellulose content. These differences in litter quantity and quality were caused by an increased abundance of unbrowsed spruce outside the enclosures. Moose pellets alone mineralized less N but more C than soil alone, but pellets combined with soil stimulated N and C mineralization more than the sum of the two separately. However, this did not appear to be sufficient to offset the depression in nitrogen and carbon mineralization in soil resulting from the increased abundance of unbrowsed spruce. We conclude that, in the long term, high rates of moose browsing depress N mineralization and net primary production through the indirect effects on recruitment into the tree stratum, and subsequent depression of litter N return and litter quality. These results suggest that the effects of herbivores on ecosystems may be amplified by positive feedbacks between plant litter and soil nutrient availability.

/pdf/moose-browsing-and-soil-fertility-in-the-boreal-forests-of-54zn0v2x8f.pdf

Moose browsing and soil fertility in the boreal forests of isle royale national park

Water productivity in agriculture: limits and opportunities for improvement

In West Asia and North Africa, shortage of water limits wheat (Triticum aestivum L.) production. Current irrigation practices aim at maximizing grain yield, but achieve lower return for the water consumed. Maximizing water use efficiency (WUE) may be more suitable in areas where water, not land, is the most limiting factor. We examined the effects of various levels of supplemental irrigation (SI) (rainfed, 1/3 SI, 2/3 SI, full SI), N (0, 5, 10, 15 g N m -2 ), and sowing time (Nov., Dec., Jan.) on evapotranspiration (ET) and WUE of wheat. WUE was calculated for rain (WUE,), for total water (gross: rain + irrigation) (WUE g ), and for SI water only (WUE SI ). ET ranged from 246 to 328 mm for rainfed crops, with grain yield ranging from 130 to 270 g m -2 and total dry matter from 380 to 1370 g m -2 . Irrigated crops had ET of 304 to 485 mm, with grain yield of 170 to 500 g m -2 . The degree to which water supply limits grain yield was indicated by the ratio of pre- to post-anthesis ET (2.1-2.4:1). The SI treatments significantly increased WUE g : from 0.77 to 0.83 to 0.92 kg m -3 in November and December sowings for 1/3 SI and from 0.77 to 0.92 kg m -3 in November sowing for 2/3 SI. The highest WUE g and WUE SI were achieved at 1/3 to 2/3 SI. WUE was substantially improved by applying 5 and 10 g N m -2 , with little increase for higher rates. Delaying sowing had a negative effect on WUE for both irrigation and rainfed conditions. In this rainfed Mediterranean environment, WUE can be substantially improved by adopting deficit SI to satisfy up to 2/3 of irrigation requirements, along with early sowing and appropriate levels of N.

Water Use Efficiency of Rainfed and Irrigated Bread Wheat in a Mediterranean Environment

As we approach the end of the century, the disparity between the rich and poor nations of the world is startling. While poverty knows no climatic or geographical boundary, a disproportionate number of the less well-off are concentrated in dryland or rainfed areas of the world. There, poverty has many bedfellows; low literacy levels, underemployment, small land holdings, limited and poor quality resources, and, consequently, low agricultural output. Because of over-stocking and poor grazing management, soil degradation is an inevitable consequence and one that undermines a country’s agricultural production capacity. This phenomenon is apparent in virtually all dryland areas of the world (Majeed, 1986). While soil degradation is evident in such places as diverse as Brazil and China, most countries of Africa are affected. Though the sub-Saharan Sahel has attracted attention because of disastrous famine in the past two decades, the North Africa region is just as much threatened. Indeed, the problem is common in West Asian countries as well. It is ironic that water, a scarce resource, which dictates the course of man’s fortunes in dryland areas, can also cause a depletion of the soil resource, if not managed properly.

Soil and fertilizer phosphorus and crop responses in the dryland Mediterranean zone

Excessive nitrogen (N) fertilizer application and poor timing of N fertilizer application to winter wheat are common problems on the North China Plain. To study the possibilities of optimizing the timing and rate of N application, a field experiment was conducted from 1999 to 2001 in a suburb of Beijing. A control (no nitrogen) and two N fertilization strategies (conventional N application and optimized N fertilization) were designed to compare their effects on wheat growth, N nutrient status, grain yield and N balance. The conventional N fertilization strategy was given a fixed N rate of 300 kg N ha−1, which was split, half in autumn and half in spring as a top-dressing. The timing and rate of N and application of the optimized N fertilization strategy were determined by the target value of soil mineral nitrogen demand for three growth periods of wheat, which is related to the target yield, and soil mineral N (Nmin) in the effective rooting depth at the beginning of these three periods. Based on the optimized N fertilization strategy, a total of 55 and 65 kg N ha−1 had to be applied to winter wheat in the re-greening and shooting stages of the first and second experimental years, respectively. Compared with the high N rate before sowing in the conventional N fertilization treatment, the optimized N fertilization treatment did not require any N fertilizer before sowing of wheat. Despite a much lower N fertilization rate, no significant difference in N nutrient status, growth during the wheat growing period or grain yield was observed between optimized N and conventional N fertilization treatments. As a consequence of optimizing the rate and timing of the N fertilizer application to match wheat demand, a much lower residual Nmin and calculated apparent N loss was found as compared to the conventional N treatment. N recovery for the optimized N fertilization treatment (67% in 1999/2000 and 66% in 2000/2001) was much higher than that of the conventional N fertilization treatment (19% in 1999/2000 and 18% in 2000/2001). In conclusion, the optimized N fertilization strategy can synchronize N demand of wheat and the N supply from soil and fertilizer, and therefore drastically reduce N application rates without any yield losses.

Synchronizing N Supply from Soil and Fertilizer and N Demand of Winter Wheat by an Improved Nmin Method

To gain a better understanding of N availability in Mediterranean soils, 18 surface (0–20cm) soil samples were selected from soil groups of Syria for study of their N mineralization potentials. The...

Nitrogen mineralization potentials of selected mediterranean soils

Four procedures (desorption by anion resin, Olsen, ammonium oxalate and calcium lactate), to determine the available P in soils, were compared in a greenhouse study. Five rates of P (0, 55, 110, 165 and 220 mg/kg) were applied to 18 calcareous soils from Syria and yield response of perennial ryegrass (Lolium multiflorum L.) to applied P was measured. Dry weight of tops correlated very well with the anion resin‐P or Olsen‐P procedures while lactate P and oxalate P results were poorly correlated. Similarly, total P uptake were significantly correlated with both anion resin P (R2=0.85) and NaHCO3‐P (R2=0.82) and less so for the oxalate P (R2=0.63) and lactate P (R2=0.32) methods. All 4 soil test procedures were effective in classifying soils into responsive and non‐responsive to P. Critical soil P levels were 18.5, 11.5, 9.5 and 7.4 mg/kg for the anion resin, Olsen, lactate and oxalate soil test procedures respectively. The Olsen method is our recommendation for calcareous soils since it is a simple...

A comparison of four soil test procedures for determination of available phosphorus in calcareous soils of the mediterranean region

Forty factorial experiments with 4 levels of N (0, 40, 80, and 120 kg N/ha and 4 levels of P (0, 8.8, 17.5, and 35 kg P/ha) with two replicates were conducted in farmers’ fields during two consecutive seasons in 1987 and 1988. The sites chosen had different soil fertility levels and the precedent crop was either local lentil (Lens esculentium), local chickpea (Cicer arietinum), or summer crop, such as watermelon (Citrullus sp.) or sunflower (Helianthus annum). The mineral‐N (NO3 and NH4‐N) was determined in the soil profile down to 100 cm in 20‐cm increments. The NO3‐N concentration in the top 0 to 20 cm ranged between 3.2 and 17.6 mg/kg and NH4‐N between 2.9 and 18.3 ing/kg. The NaHCO3‐ extractable P for the 0 to 20 cm layer ranged between 1.0 and 11.8 mg/kg. Soils classification showed dominant suborders to be Typic Chromoxerert and Vertic Xerochrept. At harvest, grain yield (GY), total dry matter (TDM) and total N uptake (TNU) were determined. To study the relationships between soil N contents...

Nitrate‐n test as a guide to N fertilization of Weat in the mediterranean region

A series of researcher-managed wheat fertilizer trials was conducted on representative farmers' fields across north west Syria between 1986 and 1990. Wheat grain and straw yields were strongly correlated with seasonal (October-May) rainfall, almost irrespective of soil fertility, crop sequence or fertilizer rate, with a highly significant response to nitrogen fertilizer which increased with increasing rainfall and decreasing initial soil mineral-nitrogen values. These results were summarized in regression equations which express yield in terms of fertilizer rates, seasonal rainfall and their interactions. The equations with applied nitrogen and seasonal rainfall were the most appropriate for determining fertilizer needs. Economic analysis indicated that all fertilizer treatment rates were profitable under existing price conditions and that fertilizer use would still be beneficial for a nitrogen price up to three times higher than that ofthe price of grain (weight for weight) with a seasonal rainfall of 250 mm. and up to six times higher with a seasonal rainfall of 450 mm.

Assessment of the effects of environmental factors on the response of wheat to fertilizer in on-farm trials in a Mediterranean type environment.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

A.E. Matar

Author Tools

Chat about Author

Papers

Nitrogen mineralization potentials of selected mediterranean soils

A comparison of four soil test procedures for determination of available phosphorus in calcareous soils of the mediterranean region

Nitrate‐n test as a guide to N fertilization of Weat in the mediterranean region

Assessment of the effects of environmental factors on the response of wheat to fertilizer in on-farm trials in a Mediterranean type environment.