Management Controls on Productivity

Menke, John W.

doi:10.1007/978-94-009-3113-8_15

Cited by 21 publications

(11 citation statements)

References 83 publications

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“…The response in cover of the plant functional group to RDM was generally similar to predictions made by others (Menke, 1989) with greatest cover of grass species on the highest RDM treatment. This response also varied between years but the higher of the intermediate RDM levels occasionally produced higher cover of grass species and the lowest RDM treatment always produced the lowest cover of grass species, often significantly.…”

Section: Discussionsupporting

confidence: 85%

Effects of residual dry matter on net primary production and plant functional groups in Californian annual grasslands

Bartolome

Jackson

Betts

et al. 2007

Grass and Forage Science

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A five-year experiment tested the response of aboveground net primary production (ANPP) and plant functional groups to manipulations in residual dry matter (RDM), reflecting typical grazing practices in Californian annual grasslands. The RDM treatments were 225, 560, 900 and 5000 kg ha )1 with the latter treatment representing no grazing by livestock. ANPP in autumn, winter and spring showed a strong year · RDM interaction indicating that, in periods with higher herbage mass, the highest RDM treatment, representative of no grazing, was usually more productive. However, the opposite pattern was observed for the autumn period when ANPP was lowest. Random effects models indicated that at most 0AE20 of the variation in ANPP for any of the three seasons stemmed from RDM treatments, with the remaining variation partitioned among temporal and spatial dimensions or not explained. Cover of grass species was highest under the highest RDM treatment in four of the five years, and lowest for the lowest RDM treatment compared with the two intermediate RDM treatments in the two years with the highest herbage masses. Cover of forbs and clover was higher on the lowest RDM treatment and lower on the highest RDM treatment than on the intermediate treatments. The results suggest that residual RDM values above 550 kg RDM ha )1 are appropriate for annual grasslands with a mean annual precipitation of more than 400 mm and offer a compromise between herbage use and promotion of future productivity and diversity, but direct control of ANPP and composition via management is not attainable because the environmental factors are predominant.

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Section: Discussionsupporting

confidence: 85%

Effects of residual dry matter on net primary production and plant functional groups in Californian annual grasslands

Bartolome

Jackson

Betts

et al. 2007

Grass and Forage Science

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“…High PC2 values reflect greater variation in seasonal temperatures and lower total annual precipitation, which typify areas of especially high C. solstitialis density in California (Dlugosch, Cang, et al, ). Previous studies in this system have proposed that C. solstitialis success stems from a lack of effective competitors in more drought prone habitats (Dlugosch, Cang, et al, ), due in part to the extensive conversion of these habitats to rangeland (Menke, ; Stromberg & Griffin, ). Other studies within the California invasion, however, have found that water availability (both naturally occurring and experimentally manipulated) is strongly and positively correlated with C. solstitialis density and fecundity (Enloe, DiTomaso, Orloff, & Drake, ; Eskelinen & Harrison, ; Hulvey & Zavaleta, ; Morghan & Rice, ), suggesting that fitness should be highest in wetter areas.…”

Section: Discussionmentioning

confidence: 99%

Expansion history and environmental suitability shape effective population size in a plant invasion

2019

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The margins of an expanding range are predicted to be challenging environments for adaptation. Marginal populations should often experience low effective population sizes (Ne) where genetic drift is high due to demographic expansion and/or census population size is low due to unfavourable environmental conditions. Nevertheless, invasive species demonstrate increasing evidence of rapid evolution and potential adaptation to novel environments encountered during colonization, calling into question whether significant reductions in Ne are realized during range expansions in nature. Here we report one of the first empirical tests of the joint effects of expansion dynamics and environment on effective population size variation during invasive range expansion. We estimate contemporary values of Ne using rates of linkage disequilibrium among genome‐wide markers within introduced populations of the highly invasive plant Centaurea solstitialis (yellow starthistle) in North America (California, USA), and within native Eurasian populations. As predicted, we find that Ne within the invaded range is positively correlated with both expansion history (time since founding) and habitat quality (abiotic climate). History and climate had independent additive effects with similar effect sizes, indicating an important role for both factors in this invasion. These results support theoretical expectations for the population genetics of range expansion, though whether these processes can ultimately arrest the spread of an invasive species remains an unanswered question.

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“…Grazing by livestock may enhance grassland species diversity through the classical mechanism of reducing biomass and slowing competitive displacement ( MacNaughton 1968; Noy‐Meir 1995; Collins et al 1998 ). It is used by conservation‐oriented grassland managers to suppress exotic species and enhance native species ( e.g., Menke 1989; Thomsen et al 1993; Barry 1998 ). Yet livestock grazing may also eliminate sensitive species and promote the spread of exotic species in grasslands ( e.g., Waser & Price 1981; Hobbs & Huenneke 1992; Fleischner 1994 ), and its positive effects on species richness may only be seen at small spatial scales ( Olff & Ritchie 1998; Stohlgren et al 1999 ).…”

Section: Introductionmentioning

confidence: 99%

Ecological Heterogeneity in the Effects of Grazing and Fire on Grassland Diversity

Harrison

Inouye

Safford

2003

Conservation Biology

162

158

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Grazing and fire and are major forces shaping patterns of native and exotic species diversity in many grasslands, yet both of these disturbances have notoriously variable effects. Few studies have examined how landscape-level heterogeneity in grassland characteristics, such as soil-based variation in biomass and species composition, may contribute to variation in the effects of fire or grazing. We studied the effects of livestock grazing and fire in a mosaic of serpentine and nonserpentine soils in California, where most grasslands are dominated by exotic annuals and serpentine soil is the major refuge for native grassland species. We predicted that the effects of disturbance would be proportional to productivity and therefore would be greater on nonserpentine than serpentine soils. We measured species composition at 80-100 grazed or ungrazed sites for 2 years before (1998)(1999) and 2 years after (2000)(2001) an autumn wildfire. Both disturbances increased total species richness on both soils. However, fire enhanced total and exotic species richness more on nonserpentine soils and enhanced native species richness more on serpentine soils. Grazing increased native species richness on serpentine soils but not on nonserpentine soils. These soil-disturbance interactions suggest that the use of fire and grazing to manage native species diversity in wildlands must be done with careful attention to background ecological heterogeneity.

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Management Controls on Productivity

Cited by 21 publications

References 83 publications

Effects of residual dry matter on net primary production and plant functional groups in Californian annual grasslands

Effects of residual dry matter on net primary production and plant functional groups in Californian annual grasslands

Expansion history and environmental suitability shape effective population size in a plant invasion

Ecological Heterogeneity in the Effects of Grazing and Fire on Grassland Diversity

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