scholarly journals Terrestrial trophic dynamics in the Canadian Arctic

2003 ◽  
Vol 81 (5) ◽  
pp. 827-843 ◽  
Author(s):  
Charles J Krebs ◽  
Kjell Danell ◽  
Anders Angerbjörn ◽  
Jep Agrell ◽  
Dominique Berteaux ◽  
...  
Keyword(s):  
Primary Production ◽  
Standing Crop ◽  
Net Primary Production ◽  
Canadian Arctic ◽  
Faecal Pellet ◽  
Trophic Dynamics ◽  
Balance Model ◽  
Arctic Ecosystems ◽  
Large Herbivore ◽  
Tundra Ecosystems

The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.

scholarly journals NET PRIMARY PRODUCTION, GROWTH, AND STANDING CROP OFMACROCYSTIS PYRIFERAIN SOUTHERN CALIFORNIA

Ecology ◽  
2008 ◽  
Vol 89 (7) ◽  
pp. 2068-2068 ◽  
Author(s):  
Andrew Rassweiler ◽  
Katie K. Arkema ◽  
Daniel C. Reed ◽  
Richard C. Zimmerman ◽  
Mark A. Brzezinski
Keyword(s):  
Primary Production ◽  
Standing Crop ◽  
Southern California ◽  
Net Primary Production ◽  
Production Growth

scholarly journals A comprehensive benchmarking system for evaluating global vegetation models

2012 ◽  
Vol 9 (11) ◽  
pp. 15723-15785 ◽  
Author(s):  
D. I. Kelley ◽  
I. Colin Prentice ◽  
S. P. Harrison ◽  
H. Wang ◽  
M. Simard ◽  
...  
Keyword(s):  
Primary Production ◽  
Fire Regime ◽  
Net Primary Production ◽  
Balance Model ◽  
Annual Variability ◽  
Benchmark System ◽  
Vegetation Models ◽  
Global Vegetation ◽  
The Impact ◽  
Benchmarking System

Abstract. We present a benchmark system for global vegetation models. This system provides a quantitative evaluation of multiple simulated vegetation properties, including primary production; seasonal net ecosystem production; vegetation cover, composition and height; fire regime; and runoff. The benchmarks are derived from remotely sensed gridded datasets and site-based observations. The datasets allow comparisons of annual average conditions and seasonal and inter-annual variability, and they allow the impact of spatial and temporal biases in means and variability to be assessed separately. Specifically designed metrics quantify model performance for each process, and are compared to scores based on the temporal or spatial mean value of the observations and a "random" model produced by bootstrap resampling of the observations. The benchmark system is applied to three models: a simple light-use efficiency and water-balance model (the Simple Diagnostic Biosphere Model: SDBM), and the Lund-Potsdam-Jena (LPJ) and Land Processes and eXchanges (LPX) dynamic global vegetation models (DGVMs). SDBM reproduces observed CO2 seasonal cycles, but its simulation of independent measurements of net primary production (NPP) is too high. The two DGVMs show little difference for most benchmarks (including the inter-annual variability in the growth rate and seasonal cycle of atmospheric CO2), but LPX represents burnt fraction demonstrably more accurately. Benchmarking also identified several weaknesses common to both DGVMs. The benchmarking system provides a quantitative approach for evaluating how adequately processes are represented in a model, identifying errors and biases, tracking improvements in performance through model development, and discriminating among models. Adoption of such a system would do much to improve confidence in terrestrial model predictions of climate change impacts and feedbacks.

scholarly journals Improved estimates of net primary production, growth, and standing crop of Macrocystis pyrifera in Southern California

Ecology ◽  
2018 ◽  
Vol 99 (9) ◽  
pp. 2132-2132 ◽  
Author(s):  
Andrew Rassweiler ◽  
Daniel C. Reed ◽  
Shannon L. Harrer ◽  
J. Clint Nelson
Keyword(s):  
Primary Production ◽  
Standing Crop ◽  
Southern California ◽  
Net Primary Production ◽  
Macrocystis Pyrifera ◽  
Production Growth
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