Diameter growth of trees in miombo and acacia woodland in an eroded landscape in NE Tanzania

Diameter increment of trees typical of miombo and acacia woodland was studied during a period of 20 years in Kondoa district, Tanzania. The study was performed in permanent plots in a severely degraded area subjected to considerable restoration efforts. A total of 15 species were selected from a database collected within a project for monitoring the landscape recovery. Growth performance of African woodland species was searched for in the literature for comparison, and a comprehensive list of citations was compiled. We found growth to fall within the range reported in earlier studies, although growth varied both between and within species. There are reports that the radial increments of trees are unimodal over their lifespan, but we found no clear support. In several species, the annual growth increased with stem diameter. Growth during the rainy ENSO year 1997/98 was pairwise compared with the preceding two years and was found to be significantly higher during the wet year, pointing to soil water as a limiting factor. We conclude that free development is an alternative to tree planting on marginal land

Understory diversity and composition after planting of teak and mahogany in Yogyakarta, Indonesia

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Wood and non-wood forest products of Central Java, Indonesia

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Influence of light availability and soil productivity on insect herbivory on bilberry (Vaccinium myrtillus L.) leaves following mammalian herbivory

Vegetative parts of bilberry (Vaccinium myrtillus) are important forage for many boreal forest mammal, bird and insect species. Plant palatability to insects is affected by concentration of nutrients and defense compounds in plants. We expected that palatability of bilberry leaves to insect herbivores is influenced by light availability and soil productivity (both affecting nitrogen concentration and constitutive carbon-based defense compound concentration) and herbivory by mammals (affecting nitrogen concentration and induced carbon-based defense compound concentration). We studied bilberry leaf herbivory under different light availability, soil productivity and mammalian herbivory pressure in small sampling units (1m x 1m) in boreal forest in Norway. We used generalized linear mixed models and generalized additive mixed models to model insect herbivory on bilberry leaves as a function of shade, soil productivity and mammalian herbivory. Observed insect herbivory on bilberry leaves increased with increasing shade levels. Predicted insect herbivory increased with increasing previous mammalian herbivory at high shade levels and this response was magnified at higher soil productivity levels. At low to intermediate shade levels, this response was only present under high soil productivity levels. Our results indicate that light availability is more important for variation in bilberry leaf palatability than soil nutrient conditions.publishedVersio

En integrerad förvaltning av älg och skog

I detta kapitel diskuterar vi möjligheten att i ökad omfattning utnyttja både värdet av skog och av älg genom en aktiv integrerad förvaltning av båda resurserna. En sådan samförvaltning bygger på att hålla ett riktigt förhållande mellan älgtäthet och foderresurser, till exempel genom att aktivt öka foderproduktionen medan älgtätheten bestäms av det tillgängliga fodret och det krav man har på täthet av oskadade stammar i unga furubestånd. I en experimentell studie prövar vi olika enkla åtgärder i skogsbruket för att öka produktionen av älgfoder som är smakligare för älgen än de träd som avses bilda det slutliga beståndet. Åtgärderna bygger på tidigare grundläggande studier av älgens matval i relation till bland annat beståndstäthet och tidigare bete på det enskilda trädet

Cascading effects of moose (Alces alces) management on birds

This is the preprint version of the articleLarge herbivores often have key functions in their ecosystems, and may change ecosystem processes with cascading effects on other animals. The mechanisms often involve relocations of resources of various kinds, including reduction in resource availability following large herbivore foraging and increase in resources from animal excreta. As large herbivore populations in Europe generally are intensely managed, management activities may interact with the activities of the herbivores themselves in the effect on other ecosystem components. We investigated the effects of moose (Alces alces) winter browsing, together with the effect of net nutrient input via supplementary winter feeding of moose on functional composition and species richness of birds in a boreal forest. Supplementary feeding stations for moose had a net zero effect on bird species richness and abundance, because negative effects of moose browsing were balanced by positive effects of nutrient input. Sites with a similar browsing intensity as at feeding stations but without nutrient input had lower abundance and species richness than feeding stations. Functional groups of bird species showed differing responses: Birds nesting at or below browsing height were negatively affected by moose browsing, whereas species nesting above the browsing zone were positively affected by moose browsing. Insect eating species responded negatively to moose browsing on birch but positively to nutrient input at feeding stations, whereas seed eating species responded positively to birch browsing and negatively to feeding stations. This study showed that both high levels of cervid activity and human management interventions influenced the bird community

Effects of Increased Soil Scarification Intensity on Natural Regeneration of Scots Pine Pinus sylvestris L. and Birch Betula spp. L.

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Does large herbivore removal affect secondary metabolites, nutrients and shoot length in woody species in semi-arid savannas?

This is the postprint version of the article published in Journal of Arid Environment. The published article can be located here: http://www.sciencedirect.com/science/article/pii/S0140196312002364We hypothesised that exclusion of long-term browsing leads to decreased nutrient concentrations, increased carbon-based secondary metabolites (CBSMs) and decreased shoot length in woody plants in semi-arid savannas. To test this, we sampled four deciduous woody species in a large-scale, long-term exclusion experiment. We found a tendency for large herbivore exclusion to either decrease nitrogen or increase tannin in two tree species. Phosphorus and total polyphenol responses indicated complex interactions with herbivore assemblage. Shoot length decreased under exclusion in two species, while a similar tendency existed in the remaining species. Therefore, we found limited support for our predictions that exclusion of browsing results in reduced nitrogen or increased CBSMs, but moderate support for decreased shoot length in semi-arid savannas. Dichrostachys cinerea, a fast-growing, aggressive invader in savannas, displayed C-limitation with removal of large herbivores because both shoot length and CBSMs decreased. In conclusion, effects of long-term browsing on deciduous trees in semi-arid savannas depend on the plant species, specific nutrients or CBSMs measured and the composition of the herbivore assemblages. Because elephant densities in the study area were high and most responses were associated with their exclusion, we conclude that elephants are important drivers of browse quality in the study area

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas

This is the postprint version of the article. The original publication is available at www.springerlink.comAbstract Carbon-based secondary metabolites (CBSMs) are assumed to function as defences that contribute to herbivore-avoidance strategies of woody plants. Severe browsing has been reported to reduce concentrations of CBSMs and increase N concentrations in individual plants, causing heavily browsed plants to be characterised by N-rich/C-poor tissues. We hypothesised that concentrations of condensed tannins (CT) and total polyphenols (TP) should decrease, or N increase, in relation to increasing intensity of browsing, rendering severely browsed plants potentially more palatable (increased N:CT) and less N-limited (increased N:P) than lightly browsed ones. We sampled naturally browsed trees (taller than 2 m) of four abundant species in southern Kruger National Park, South Africa. Species-specific relationships between N:CT, CT, TP and P concentrations and increasing browsing intensity were detected, but N and N:P were consistently invariable. We developed a conceptual post-hoc model to explain diverse species-specific CBSM responses on the basis of relative allocation of C to total C-based defence traits (e.g., spines/thorns, tough/evergreen leaves, phenolic compounds). The model suggests that species with low allocation of C to C-based defence traits become C-limited (potentially more palatable) at higher browsing intensity than species with high allocation of C to C-based defences. The model also suggests that when N availability is high, plants become C-limited at higher browsing intensity than when N availability is low