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Questions Ungulate herbivory and formation of large termite mounds occur over different time scales, but both can affect plant community composition in savannas. Human-managed savanna systems are increasingly dominated by domesticated grazing herbivores. These have replaced a mix of indigenous browsers and grazers, leading to changes in plant communities such as increased bush encroachment. We compared the relative impacts of five decades of different types of ungulate herbivory (cattle grazing, browsing and grazing by wild herbivores, and exclusion of all larger herbivores) on woody plant assemblages in two habitats, namely, large termite mounds, which may be thousands of years old, and the surrounding matrix. Location Miombo woodland savanna, Zimbabwe. Methods To determine the influence of termite mounds and herbivory on spatial distribution and composition of woody assemblages, we compared 40 paired mound-matrix plots from the three herbivory treatments using PERMANOVA. We assessed whether mound plots were more similar to each other than matrix plots were to each other, and whether herbivory influenced similarity. We used SIMPER analysis to identify changes in abundance of indicator species for each habitat (i.e. mound or matrix). Results Species composition differed significantly between mound and matrix and also between herbivory treatments. Woody plant assemblages on mounds were more similar to each other than woody plant assemblages in matrix plots were to each other, regardless of type of herbivory, but herbivory reduced the mound/matrix contrast. Sample location (i.e. on mound or in matrix) explained 23% of the variation in woody species composition, compared to 12% explained by herbivory. Woody plant abundance was lowest where there were both grazers and browsers. Conclusions The influence of large termite mounds on plant assemblages was roughly double that of herbivory, which has occurred over five decades. Type of herbivory emerged as relatively influential on woody plant species composition, given that the time periods involved were short by comparison to the slow formation of termite mounds. Type of herbivory also influenced species composition and vegetation structure, with a diversity of herbivores necessary to reduce encroachment by woody species. [ABSTRACT FROM AUTHOR]

Questions We investigated whether soils of small mounds resembled large mound or matrix soils, whether changes in plant composition reflected changes in soils, and the sequence in which plants colonize and disappear from mounds of increasing size. Location Miombo woodland in northwest Zimbabwe. Methods Macrotermitinae termitaria vary in size and soil nutrient concentrations, harbouring distinct woody plant assemblages, making them foci for plant and animal diversity, and also influencing primary, secondary and tertiary productivity. In spite of the importance of termitaria to heterogeneity and diversity, no studies have investigated changes in plant species assemblages as mound surface area increases to the point where mound vegetation is distinct from that of the matrix. We compared woody plant assemblages on 43 matrix plots with 95 Macrotermes termitaria across a range of surface areas, using ANOSIM, cluster analysis and MDS ordination. We compared soil nutrients, p H and clay, from ten large and ten small termitaria, and ten matrix sites. We also assessed how relative representation of large mound or matrix indicator species changed with mound area. Results Change was apparent even at mound sizes of >10 m2, where both soils and plant assemblages on mounds were significantly different to those of the matrix. Plant assemblages fell into two main groups at 20% similarity; the first comprised of matrix plots, mounds <10 m2 and some mounds between 10 and 30 m2; the second, the remainder of the mounds between 10 and 30 m2 and all mounds >30 m2. At 40% similarity, four groups emerged: matrix, mounds <10 m2, mounds 10-30 m2 and mounds >30 m2. Woody plant composition changed gradually as mound area increased. On termitaria <10 m2, only 25% of indicators were mound indicator species, but on mounds between 10 and 30 m2 in size, 62.5% were mound indicators. On termitaria >30 m2 in surface area, only mound indicator species were found. Conclusions Through termite activities in concentrating nutrients and clay, termitaria provide habitat for species usually excluded from the matrix. The process of mound building and the nature of the plants that establish on them seem to establish a positive feedback for establishment of other non-woodland matrix species. [ABSTRACT FROM AUTHOR]