Drought suppresses soil predators and promotes root herbivores in mesic, but not in xeric grasslands

Precipitation changes among years and locations along gradients of mean annual precipitation (MAP). The way those changes interact and affect populations of soil organisms from arid to moist environments remains unknown. Temporal and spatial changes in precipitation could lead to shifts in functional composition of soil communities that are involved in key aspects of ecosystem functioning such as ecosystem primary production and carbon cycling. We experimentally reduced and increased growing-season precipitation for 2 y in field plots at arid, semiarid, and mesic grasslands to investigate temporal and spatial precipitation controls on the abundance and community functional composition of soil nematodes, a hyper-abundant and functionally diverse metazoan in terrestrial ecosystems. We found that total nematode abundance decreased with greater growing-season precipitation following increases in the abundance of predaceous nematodes that consumed and limited the abundance of nematodes lower in the trophic structure, including root feeders. The magnitude of these nematode responses to temporal changes in precipitation increased along the spatial gradient of long-term MAP, and significant effects only occurred at the mesic site. Contrary to the temporal pattern, nematode abundance increased with greater long-term MAP along the spatial gradient from arid to mesic grasslands. The projected increase in the frequency of extreme dry years in mesic grasslands will therefore weaken predation pressure belowground and increase populations of root-feeding nematodes, potentially leading to higher levels of plant infestation and plant damage that would exacerbate the negative effect of drought on ecosystem primary production and C cycling.

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Net Primary Production in the Shortgrass Steppe

Ecology of the Shortgrass Steppe ◽

10.1093/oso/9780195135824.003.0016 ◽

2008 ◽

Author(s):

William K. Lauenroth ◽

Daniel G. Milchunas

Keyword(s):

Global Change ◽

Primary Production ◽

Net Primary Production ◽

Regional Scale ◽

Ecosystem Dynamics ◽

Shortgrass Steppe ◽

Annual Precipitation ◽

Mean Annual Precipitation ◽

Spatial And Temporal Patterns ◽

Temporal And Spatial

Net primary production (NPP), the amount of carbon or energy fixed by green plants in excess of their respiratory needs, is the fundamental quantity upon which all heterotrophs and the ecosystem processes they are associated with depend. Understanding NPP is therefore a prerequisite to understanding ecosystem dynamics. Our objectives for this chapter are to describe the current state of our knowledge about the temporal and spatial patterns of NPP in the shortgrass steppe, to evaluate the important variables that control NPP, and to discuss the future of NPP in the shortgrass steppe given current hypotheses about global change. Most of the data available for NPP in the shortgrass steppe are for aboveground net primary production (ANPP), so most of our presentation will focus on ANPP and we will deal with belowground net primary production (BNPP) as a separate topic. Furthermore, our treatment of NPP in this chapter will ignore the effects of herbivory, which will be covered in detail in chapter 16. Our approach will be to start with a regional-scale view of ANPP in shortgrass ecosystems and work toward a site-scale view. We will begin by briefly placing ANPP in the shortgrass steppe in its larger context of the central North American grassland region. We will then describe the regional-scale patterns and controls on ANPP, and then move to the site-scale patterns and controls on ANPP. At the site scale, we will describe both temporal and spatial dynamics, and controls on ANPP as well as BNPP. We will then discuss relationships between spatial and temporal patterns in ANPP and end the chapter with a short, speculative section on how future global change may influence NPP in the shortgrass steppe. Temperate grasslands in central North America are found over a range of mean annual precipitation from 200 to 1200 mm.y–1 and mean annual temperatures from 0 to 20 oC (Lauenroth et al., 1999). The widely cited relationship between mean annual precipitation and average annual ANPP allows us to convert the precipitation gradient into a production gradient (Lauenroth, 1979; Lauenroth et al., 1999; Noy-Meir, 1973; Rutherford, 1980; Sala et al., 1988b).

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Long-term drainage reduces CO<sub>2</sub> uptake and increases CO<sub>2</sub> emission on a Siberian floodplain due to shifts in vegetation community and soil thermal characteristics

Biogeosciences ◽

10.5194/bg-13-4219-2016 ◽

2016 ◽

Vol 13 (14) ◽

pp. 4219-4235 ◽

Cited By ~ 17

Author(s):

Min Jung Kwon ◽

Martin Heimann ◽

Olaf Kolle ◽

Kristina A. Luus ◽

Edward A. G. Schuur ◽

...

Keyword(s):

Primary Production ◽

Ecosystem Respiration ◽

Gross Primary Production ◽

Thermal Characteristics ◽

Growing Season ◽

Co2 Uptake ◽

Vegetation Community ◽

Uptake Rates ◽

Soil Temperatures

Abstract. With increasing air temperatures and changing precipitation patterns forecast for the Arctic over the coming decades, the thawing of ice-rich permafrost is expected to increasingly alter hydrological conditions by creating mosaics of wetter and drier areas. The objective of this study is to investigate how 10 years of lowered water table depths of wet floodplain ecosystems would affect CO2 fluxes measured using a closed chamber system, focusing on the role of long-term changes in soil thermal characteristics and vegetation community structure. Drainage diminishes the heat capacity and thermal conductivity of organic soil, leading to warmer soil temperatures in shallow layers during the daytime and colder soil temperatures in deeper layers, resulting in a reduction in thaw depths. These soil temperature changes can intensify growing-season heterotrophic respiration by up to 95 %. With decreased autotrophic respiration due to reduced gross primary production under these dry conditions, the differences in ecosystem respiration rates in the present study were 25 %. We also found that a decade-long drainage installation significantly increased shrub abundance, while decreasing Eriophorum angustifolium abundance resulted in Carex sp. dominance. These two changes had opposing influences on gross primary production during the growing season: while the increased abundance of shrubs slightly increased gross primary production, the replacement of E. angustifolium by Carex sp. significantly decreased it. With the effects of ecosystem respiration and gross primary production combined, net CO2 uptake rates varied between the two years, which can be attributed to Carex-dominated plots' sensitivity to climate. However, underlying processes showed consistent patterns: 10 years of drainage increased soil temperatures in shallow layers and replaced E. angustifolium by Carex sp., which increased CO2 emission and reduced CO2 uptake rates. During the non-growing season, drainage resulted in 4 times more CO2 emissions, with high sporadic fluxes; these fluxes were induced by soil temperatures, E. angustifolium abundance, and air pressure.

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SPRING SOIL WATER, PRECIPITATION, AND NITROGEN FERTILIZER: EFFECT ON BARLEY YIELD

Canadian Journal of Soil Science ◽

10.4141/cjss80-051 ◽

1980 ◽

Vol 60 (3) ◽

pp. 461-469 ◽

Cited By ~ 8

Author(s):

J. B. BOLE ◽

U. J. PITTMAN

Keyword(s):

Soil Water ◽

Growing Season ◽

N Fertilizer ◽

Risk Level ◽

Similar Degree ◽

Model Equations ◽

Fertilizer Effect ◽

Summer Fallow ◽

Growing Season Precipitation

Results of a 5-yr field experiment were used to develop a regression model (R = 0.94) describing barley yield as a function of available soil water in the spring (Ws), growing season precipitation (GSP), and N fertilizer. Yields on independent fertility plots having Ws and GSP levels within the scope of the data used in deriving the equation were in close agreement with those predicted by the model. Equations were developed for Ws defined as soil water on either 15 May or 1 June and GSP from then until 31 July. Including rainfall received after 31 July in GSP decreased the accuracy of the model. At the levels of GSP occurring in the study, GSP and Ws affected yield to a similar degree, but with the long-term average GSP and Ws levels at Lethbridge, Ws was only about half as effective as GSP on stubble and one-third as effective on summer fallow. Growing season precipitation had a three times greater effect on barley response to N fertilizer than Ws. The model would allow a producer to base his fertilizer N rate on a gravimetrically determined Ws level at seeding and use the GSP probability as his risk level. Using the current cost:price ratio of N fertilizer and barley, he can optimize his N fertilizer level based on the measured Ws.

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Variations in and environmental controls of primary productivity in the Amundsen Sea

10.5194/bg-2021-296 ◽

2021 ◽

Author(s):

Jianlong Feng ◽

Delei Li ◽

Jing Zhang ◽

Liang Zhao

Keyword(s):

Primary Production ◽

Primary Productivity ◽

Sea Surface ◽

Iron Nitrate ◽

Amundsen Sea ◽

Dissolved Iron ◽

Environmental Controls ◽

Long Term Changes ◽

Temporal And Spatial

Abstract. The Amundsen Sea is one of the regions with the highest primary productivity in the Antarctic. To better understand the role of the Southern Ocean in the global carbon cycle and in climate regulation, a better understanding of the variations in and environmental controls of primary productivity is needed. Using cluster analysis, the Amundsen Sea was divided into nine bioregions. The biophysical differences among bioregions enhanced confidence to identify priorities and regions to study the temporal and spatial variations in primary productivity. Four nearshore bioregions with high net primary productivity or rapidly increasing rates were selected to analyze temporal and spatial variations in primary productivity in the Amundsen Sea. Due to changes in net solar radiation and sea ice, primary production had significant seasonal variation in these four bioregions. The phenology had changed at two bioregions (3 and 5), which has the third and fourth highest primary production, due to changes in the dissolved iron, nitrate, phosphate, and silicate concentrations. Annual primary production showed increasing trends in these four bioregions. The variation in primary production in the bioregion (9), which has the highest primary production, was mainly affected by variations in sea surface temperatures. In the bioregion, which has the second-highest primary production (8), the primary production was significantly positively correlated with sea surface temperature and significantly negatively correlated with sea ice thickness. The long-term changes of primary productivity in bioregions 3 and 5 were thought to be related to changes in the dissolved iron, nitrate, phosphate, and silicate concentrations, and dissolved iron was the limiting factor in these two bioregions. Bioregionalization not only disentangle multiple factors that control the spatial differences, but also disentangle limiting factors that affect the phenology, decadal and long-term changes in primary productivity.

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EFFECT OF SOIL PROFILE TYPE AND FERTILIZER ON MOISTURE USE BY WHEAT GROWN ON FALLOW OR STUBBLE LAND

Canadian Journal of Soil Science ◽

10.4141/cjss69-026 ◽

1969 ◽

Vol 49 (2) ◽

pp. 189-197 ◽

Cited By ~ 12

Author(s):

E. de Jong ◽

D. A. Rennie

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Soil Profile ◽

Growing Season ◽

Yield Functions ◽

Use Efficiency ◽

Lower Slope ◽

Growing Season Precipitation ◽

Upper Slope

Equations describing yield as a function of moisture use arc reported for fallow-seeded wheat for the years 1960 to 1965, inclusive, and for wheat seeded on stubble land from 1964 to 1967. In general, yields increased linearly with water use; second-degree functions did not greatly increase the correlation, but represent more realistic yield functions. The increase in yield per cm water used was larger on fallow than on stubble land, and increased with fertilization. Growing season precipitation ranged from 5 to 26 cm during the study period; the long-term average is 19 cm. Mean yields for unfertilized and fertilized fallow and stubble wheat were 1,500 and 1,860 kg/ha, and 1,340 and 1,720 kg/ha, respectively.Yield, water used, and water use efficiency varied somewhat, depending on whether the crop was grown on a knoll, upper slope, lower slope, or in depressional areas.

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Stocking rate impacts performance and economics of grazing beef steers on mixed-grass prairies of the Southern Great Plains1

Translational Animal Science ◽

10.1093/tas/txaa134 ◽

2020 ◽

Vol 4 (3) ◽

Author(s):

Paul A Beck ◽

Matthew R Beck ◽

Stacey A Gunter ◽

Jon T Biermacher ◽

Robert L Gillen

Keyword(s):

Growing Season ◽

Climatic Conditions ◽

Stocking Rate ◽

Animal Performance ◽

Grazing Season ◽

Net Return ◽

Mixed Grass ◽

Stocking Rates ◽

Growing Season Precipitation

Abstract Stocking rate is a fundamental management factor that has major impacts on animal performance, profitability, and long-term sustainability of native range ecosystems. This research was conducted to determine the effects of stocking rate on performance and economics of growing steers grazing a mixed-grass prairie on a rolling upland red shale ecological site at the Marvin Klemme Range Research Station (35° 25′ N 99° 3′ W). The recommended sustainable stocking rate at this location is suggested to be 25 animal unit days (AUD)/ha. Steers [n = 836, initial body weight (BW) ± SD = 216 ± 11.7 kg] grazed at seven stocking rates ranging from 4.13 ha/steer to 1.83 ha/steer over a 7-yr period, from 1990 to 1996, with year considered the random replication. During the experimental period, overall climatic conditions were favorable for forage production with average growing season precipitation of 118% of the long-term average over the 7-yr experiment, and only 1 yr (1994 with only 57% of the long-term average) with growing season precipitation substantially less than the long-term average. Over the entire summer grazing season, average daily gain (ADG) decreased linearly (P < 0.01) with increasing stocking rate, such that for each additional hectare available per steer ADG increased by 0.05 kg/d (R2 = 0.88). Contrary to ADG, BW gain per hectare over the grazing season increased linearly (P < 0.01) with increasing stocking rate, as stocking rate increased from 4.13 ha/steer to 1.83 ha/steer BW gain per hectare doubled from 33.1 kg/ha to 66.8 kg/ha, respectively. With land costs included in the economic analysis, net return per hectare increased linearly (P < 0.01) from $13 [U.S. Dollars [USD]) at the 4.13 ha/steer to $52/ha at the 1.83 ha/steer. For each additional hectare per steer, net return was reduced by $15.80 (USD)/steer and $15.70 (USD)/ha. In favorable climatic conditions, such as during this 7-yr experiment, economically optimal stocking rates can be more than doubled compared with the stocking rate recommended by the United States Department of Agriculture (USDA) Soil Conservation Service. Increasing stocking rates decrease individual animal performance but maximize BW gain per hectare, which leads to the increasing economic returns observed. Research is needed to determine the long-term implications of these stocking rates during unfavorable growing conditions and setting stocking rates based on seasonal weather patterns and extended weather outlook predictions.

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Risk simulation of the economics of manure application to restore eroded wheat cropland

Canadian Journal of Soil Science ◽

10.4141/cjss93-028 ◽

1993 ◽

Vol 73 (2) ◽

pp. 267-274 ◽

Cited By ~ 10

Author(s):

Brian S. Freeze ◽

C. Webber ◽

C. W. Lindwall ◽

J. F. Dormaar

Keyword(s):

Moisture Content ◽

Growing Season ◽

Soil Animal ◽

Manure Application ◽

Canadian Prairies ◽

Soil Zone ◽

Animal Wastes ◽

Risk Simulation ◽

Growing Season Precipitation

The economics of hauling manure as an amendment for restoring the productivity of artificially eroded wheat cropland was investigated using a simulation model. The model incorporated data on the long-term variability of wheat price, growing season precipitation and manure moisture content, and data from manure application experiments conducted on land where topsoil had been removed in levelling. Results showed that on average over the long term, the value of manure as an amendment for restoring the productivity of slightly eroded wheat cropland (< 20 cm soil lost/removed) is sufficient to allow manure to be hauled 3–5 km further than would be the case on non-eroded soils. On heavily eroded wheat cropland (> 80 cm soil lost/removed), hauling distance can be extended approximately 20 km. The disposal market for feedlot manure can be expected to extend to a distance of about 55 km from its source. Results are applicable to the dryland wheat areas of the dark brown soil zone of the Canadian prairies. Key words: Feedlot manure, fertilizer economics, eroded soil, animal wastes

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Legacies of precipitation fluctuations on primary production: theory and data synthesis

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2011.0347 ◽

2012 ◽

Vol 367 (1606) ◽

pp. 3135-3144 ◽

Cited By ~ 284

Author(s):

Osvaldo E. Sala ◽

Laureano A. Gherardi ◽

Lara Reichmann ◽

Esteban Jobbágy ◽

Debra Peters

Keyword(s):

Primary Production ◽

Net Primary Production ◽

Space Versus ◽

Annual Precipitation ◽

Mean Annual Precipitation ◽

Production Theory ◽

Relative Importance ◽

Data Synthesis ◽

Precipitation Changes

Variability of above-ground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space (based on multiyear averages for different locations) than through time (based on year-to-year change at single locations). Here, we propose a theory of controls of ANPP based on four hypotheses about legacies of wet and dry years that explains space versus time differences in ANPP–precipitation relationships. We tested the hypotheses using 16 long-term series of ANPP. We found that legacies revealed by the association of current- versus previous-year conditions through the temporal series occur across all ecosystem types from deserts to mesic grasslands. Therefore, previous-year precipitation and ANPP control a significant fraction of current-year production. We developed unified models for the controls of ANPP through space and time. The relative importance of current-versus previous-year precipitation changes along a gradient of mean annual precipitation with the importance of current-year PPT decreasing, whereas the importance of previous-year PPT remains constant as mean annual precipitation increases. Finally, our results suggest that ANPP will respond to climate-change-driven alterations in water availability and, more importantly, that the magnitude of the response will increase with time.

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