Significance
Governments spend billions of dollars each year managing invasive plant species. Many invasive plants have escaped from pastures and now degrade natural areas and transform ecosystems. New pasture taxa are promoted to help achieve sustainable intensification of agriculture by increasing production without using more land. However, plant characteristics that increase production also increase invasion risk. Combined with inadequate regulation and management to establish large feed-plant populations, new taxa will likely exacerbate problems with invasive species. Livestock production accounts for 30% of the world's land area. Risks associated with invasive feed-plants have been largely overlooked, even by studies explicitly critiquing the environmental risks of sustainable intensification. We suggest a suite of protocols to reduce these risks in sustainable intensification of agriculture.
Bamboos are one of the most economically important plant groups globally, but this world-wide trade creates risks of invasions. Here we identified 1662 species of bamboo, of which almost a seventh (232) have been introduced outside their native range, with Asiatic and larger species preferred. Only 12 species were found to have become invasive. However, invasiveness was found to be more a function of human-usage than specific species traits, suggesting the recent upsurge in bamboo cultivation could pose future invasion risks.
Grasses using the C4 photosynthetic pathway dominate frequently burned savannas, where the pathway is hypothesized to be adaptive. However, independent C4 lineages also sort among different fire environments. Adaptations to fire may thus depend on evolutionary history, which could be as important as the possession of the C4 photosynthetic pathway for life in these environments. Here, using a comparative pot experiment and controlled burn, we examined C3 and C4 grasses belonging to four lineages from the same regional flora, and asked the following questions: Do lineages differ in their responses to fire, are responses consistent between photosynthetic types, and are responses related to fire frequency in natural habitats? We found that in the C4 Andropogoneae lineage, frost killed a large proportion of aboveground biomass and produced a large dry fuel load, which meant that only a small fraction of the living tissue was lost in the fire. C3 species from the Paniceae and Danthonioideae lineages generated smaller fuel loads and lost more living biomass, while species from the C4 lineage Aristida generated the smallest fuel loads and lost the most living tissue. Regrowth after the fire was more rapid and complete in the C4 Andropogoneae and C3 Paniceae, but incomplete and slower in the C3 Danthonioideae and C4 Aristida. Rapid recovery was associated with high photosynthetic rates, high specific leaf area, delayed flowering, and frequent fires in natural habitats. Results demonstrated that phylogenetic lineage was more important than photosynthetic type in determining the fire response of these grasses and that fire responses were related to the frequency that natural habitats burned.
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