Competitive effects of woody and herbaceous vegetation in a young boreal mixedwood stand

2008 ◽  
Vol 38 (7) ◽  
pp. 1817-1828 ◽  
Author(s):  
Cosmin D. Man ◽  
Philip G. Comeau ◽  
Douglas G. Pitt
Keyword(s):  
Soil Moisture ◽  
Populus Tremuloides ◽  
Soil Nitrogen ◽  
Picea Glauca ◽  
Nitrogen Availability ◽  
White Spruce ◽  
Soil Nitrogen Availability ◽  
Area Index ◽  
Promising Alternative ◽  
Light Soil

The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation on resource availability and white spruce ( Picea glauca (Moench) Voss) growth were examined as part of a long-term experiment established in 2002 near Whitecourt, Alberta, Canada. During the 2005 growing season, we examined the effects of herbicide treatments designed to control only woody (triclopyr ester) or both woody and herbaceous (glyphosate) vegetation on leaf area index (LAI) of both the woody and herbaceous components and relationships among LAI and light, soil moisture, air temperature, soil temperature, nitrogen availability, and spruce growth. Treatments reduced LAI and increased light, soil nitrogen availability, and white spruce growth. There were no apparent effects of the treatments on soil moisture in 2005. Both the woody and herb–grass layers appear to be competing for light and soil nitrogen in this young plantation. Controlling only woody vegetation resulted in an increase in herbaceous and total LAI (dominated by the grass Calamagrostis canadensis (Michx.) Beauv.). Spot treatment, involving control of vegetation within a 2 m radius of spruce seedlings while leaving 1 m of untreated ground between treated spots, may be a promising alternative to classical broadcast treatments for establishing spruce in a mixedwood stand. Spot treatments provided good growing conditions and reduced exposure of spruce seedlings to summer and winter frost injury during the first 3 years after planting.

scholarly journals Controls on spatial and temporal patterns of soil nitrogen availability in a High Arctic wetland

2017 ◽  
Author(s):  
Jacqueline K. Y. Hung ◽  
David M. Atkinson ◽  
Neal A. Scott
Keyword(s):  
Soil Moisture ◽  
Soil Nitrogen ◽  
Nitrogen Availability ◽  
Inorganic Nitrogen ◽  
High Arctic ◽  
Arctic Ecosystems ◽  
Soil Nitrogen Availability ◽  
Early Season ◽  
Environmental Controls ◽  
Sedge Meadows

Abstract. Increased soil nutrient availability, and associated increase in vegetation productivity, could create a negative feedback between Arctic ecosystems and the climate system, reducing the contribution of Arctic ecosystems to future climate change. To predict whether this feedback will develop, it is important to understand the environmental controls over nutrient cycling in High Arctic ecosystems, and how they vary over space and time. This study explores the environmental controls over spatial patterns of soil nitrogen availability in a High Arctic wet sedge meadow and how they influence carbon exchange processes. Ion exchange resin membranes measured available inorganic nitrogen in soils throughout the growing season at a high spatial resolution, while environmental variables (e.g. active layer depth, soil temperature, soil moisture) and carbon flux measurements were taken at frequent intervals during the 2016 field season. Environmental measures correlated highly with total and late season nitrate levels (total season dry tracks nitrate R2 = 0.533, total season wet tracks nitrate R2 = 0.803, late season nitrate R2 = 0.622), with soil temperatures at 5 cm depth having the greatest effect. Soil available nitrate and ammonium correlated highly with total and early season gross primary productivity (total season wet tracks R2 = 0.685, early season dry tracks R2 = 0.788, early season wet tracks R2 = 0.785). Higher ammonium concentrations coincided with greater carbon dioxide uptake. Nitrate concentrations correlated strongly to soil moisture, but nitrate levels were much lower than ammonium concentrations, suggesting low rates of nitrification vs. mineralization. Similar patterns were observed regardless of whether the wet-sedge meadow was classified as wet or dry, but the relationships were always stronger in areas classified as wet, indicating the importance of moisture and water availability on abiotic processes in High Arctic wet sedge meadows. Topography played an important role in the movement and transport of water, which influenced how nutrients were cycled and moved within the wetland. Generally, the low-lying areas had the highest inorganic nitrogen concentrations. These results suggest that finer scale processes altering nitrogen availability may influence the overall carbon balance of wet sedge meadows in the High Arctic, and how these ecosystems may respond to changes in climate.

Field evaluation of several chemical indexes of soil nitrogen availability

1990 ◽  
Vol 123 (1) ◽  
pp. 83-88 ◽  
Author(s):  
S. D. Hong ◽  
R. H. Fox ◽  
W. P. Piekielek
Keyword(s):  
Soil Nitrogen ◽  
Nitrogen Availability ◽  
Field Evaluation ◽  
Soil Nitrogen Availability
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