Title:

Impacts of fire history in a semi-arid woodland savanna

Publication Year:
2018
Abstract:

Fire is known to be an important element shaping semi-arid ecosystems. Within SASSCAL we conducted several projects in the woodland savanna of the Waterberg Plateau Park to gain a better understanding of the impact of fire on ecosystem properties and processes (soil characteristics, species composition and structure of the vegetation, changes in plant forage quality, insect biodiversity, and the utilization of habitat and plants by large herbivores). Four adjacent areas of around 2,000 ha–2,500 ha each with different times since last burn were studied (in 2014, when most of the measurements were done, the areas had been burnt 2, 3, 14, and 24 years prior to the study). We found inconsistent effects of different fire histories on soil nutrients, soil organic carbon, and soil respiration, which suggests that soil resources return rapidly (within a year or two) to pre-fire conditions at our sites. We also assume (based on the standing biomass of the four areas during the study) that the fires were likely to have not been sufficiently intense to cause long-term detrimental impacts and impair the recovery of soil resources at our sites. Furthermore, fire positively affected the grass component by increasing grass density and enhancing productivity. Fire maintained open savannas through the top-kill of woody plants but did not alter plant species composition. The influence of burning on the quality of grasses was relatively short-lived (two years after burning, grass quality in burnt sites was comparable with that of unburnt sites). However, trees, whose leaves are generally higher in protein, remained at a higher quality for longer periods after fire and thus served as supplementary food not only for browsers and mixed feeders but also for herbivores generally considered to be ‘pure’ grazers (e.g., red hartebeest, buffalo). Fire had a negative impact on small ground-nesting bees, whereas bigger and above-ground-nesting bees seemed to be favoured by fire. Ground-dwelling invertebrate communities differed with time since last burn, the main driver of the differences being litter cover. Our findings in relation to fire illustrate that heterogeneous habitats, as a result of pyrodiversity, are of great benefit for the habitat utilization and plant utilization of large herbivores as well as increasing the overall diversity of invertebrates. Managers can maximise biodiversity and diversity in resource and habitat utilization by maximising the diversity of fire histories in the managed areas (commonly termed patch-mosaic burning).

Publication Title:

Climate change and adaptive land management in southern Africa - assessments, changes, challenges, and solutions

Place:
Göttingen and Windhoek
Editor:
Revermann R, Krewenka KM, Schmiedel U, Olwoch JM, Helmschrot J, Jürgens N
Publisher:
Klaus Hess Publishers
Series Title:
Biodiversity and Ecology
Series Number:
6
Pages:
207-218
Item Type:
Book or Magazine Section
Language:
en

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