Dong, Xuejun , Nyren, Paul , Patton, Bob , Kreft, Brian , Nyren, Anne .
Specific leaf area, leaf thickness and density of two range plant species influenced by long-term cattle grazing.
Specific leaf area (SLA), leaf thickness (LT) and density (LD) influence whole plant survival, metabolism and nutrition value. However, systematic measurement of these plant attributes on rangelands with animal grazing is not well documented. This is a case study on two dominant cool-season grasses, Pascopyron smithii Rydb., and Poa pratensis L., growing in North Dakota rangelands. Leaf samples were collected during Jun-Jul and Aug of 2002 on the upland locations with similar topography in three non-grazing exclosures and three heavily grazed pastures with a stocking rate of 6.8 AUM/ha. During each field trip, 6 batches of leaves (each containing 12-20 young and fully expanded leaves) were collected from each of the pastures/exclosures. Leaf area was measured using contact paper and an image analysis system; leaf volume was measured by displacement of water in a cylinder; LT was calculated using volume and area data; LD was obtained from leaf volume and dry mass. Based ANOVA analysis, with the increase of grazing, SLA remained unchanged in Pascopyron, but tended to increase by 15% and 26% in Jun-Jul and Aug, respectively, in Poa. As SLA can be expressed as SLA = 1/(LDŽLT), the unchanged SLA in Pascopyron in Aug could be interpreted as the cancellation effects of the increased LT and decreased LD. The grazing associated increase in SLA in Poa in Aug resulted mainly from the decreased LD. A higher SLA is usually associated with a higher liquid content and metabolic rate, but it may also reduce leafs drought resistance capacity. Pascopyron is well adapted while Poa is sensitive to drought. Our results predict that Poa plants in this grassland may have become more sensitive to drought with the long-term animal grazing.
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1 - North Dakota State University, Central Grasslands Research Extension Center, 4824 48th AVE SE, Streeter, ND, 58483, USA
2 - North Dakota State University, Central Grasslands Research Extension Center
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM