Heterogeneity decreases as time since fire increases in a South American grassland. Issue 1 (13th September 2020)

• Record Type: Journal Article
• Authors: López‐Mársico, Luis; Lezama, Felipe; Altesor, Alice
• Editors: Hölzel, Norbert
• Is Part Of: Applied vegetation science. Volume 24:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-13
• Subjects: burn -- grazing -- plant coverage -- plant groups -- Saccharum angustifolium -- species richness -- succession -- Uruguayan grasslands; Plant ecology -- Periodicals; Plant communities -- Periodicals; Plant populations -- Periodicals; Nature -- Effect of human beings on -- Periodicals; 581.705
• DOI: 10.1111/avsc.12521
• Languages: English
• ISSNs: 1402-2001

Abstract

Abstract: Questions: Disturbances change the fundamental properties of grasslands on different spatio‐temporal scales. Uruguay is part of the Río de la Plata grasslands, and 60% is occupied by native grasslands dominated by perennial species. In plant communities dominated by tall tussock grasses, patchy and asynchronous field burns are a traditional practice among ranchers. We asked: how do the structural characteristics of vegetation vary in patches with different time since the last fire? Location: Grassland of the Eastern Hills, Uruguay. Methods: We selected 18 grazed sites in order to obtain a spatial chronosequence with four age categories since the last fire: 6, 18, 30, and more than 60 months before sampling. Plant composition, species richness, coverage of each species, bare soil, and standing dead biomass were determined in plots of 25 m 2 . We used non‐metric multidimensional scaling (NMDS) and the multiresponse permutation procedure (MRPP) to determine differences in community composition, and the ANOVA or the Kruskal–Wallis test to compare structural variables between patches of different burning ages. Results: Patches of different burning age had different species compositions. Species richness, Shannon diversity index, evenness, and bare soil decreased, whereas plant coverage, standing dead biomass, and vegetation strata increased as time since the last fire increased. Conclusions: Our study confirmed occasional and localized field‐burns as major driver of vegetation change and structural diversity in a grazed native grassland dominated by a tall tussock grass. On a larger scale, we observed the coexistence of patches in different successional stages and differences in species composition between patches belonging to early stages. These grasslands require asynchronous burning of patches to generate structural changes that maximize both the spatial and temporal heterogeneity. Abstract : In a sub‐humid Uruguayan grassland community, dominated by Saccharum angustifolium, a large amount of standing dead biomass is accumulated. Fire removes above‐ground biomass of the dominant species and causes a release of resources, such as space and light. The bare soil gaps that appear are quickly colonized by herbaceous monocots and dicots. Photo: Andrea Geymonat.