| 1. |
- Bergvall, Ulrika A, et al.
(author)
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A test of simultaneous and successive negative contrast in fallow deer foraging behaviour
- 2007
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In: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 74:3, s. 395-402
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Journal article (peer-reviewed)abstract
- The study of contrast investigates how rewards influence behaviour when animals are exposed to two or more levels of rewards compared to when they experience only a single level. The appearance of an exaggerated response to a shift in reward is referred to as a contrast effect and is an empirically well-established phenomenon. Although contrast effects could be important in foraging behaviour, no direct experimental tests of contrast effects in foraging by mammalian herbivores exist. During foraging, mammalian herbivores can encounter a range of plants that vary in the amount of nutrients and toxins. They may thus compare food items by taste, which in turn can give rise to contrast effects. In feeding experiments with fallow deer, Dama dama, we investigated the presence of simultaneous negative contrast. We found that the deer consumed less from a bowl of pellets containing 1% tannin when they shifted to it from a bowl with pellets containing only 0.25% tannin than when they shifted from another bowl with pellets containing 1% tannin. We estimated a fourfold difference between treatments in test food consumption at the highest levels of preloading, but none at the lowest levels. We found no support for successive negative contrast in experiments where the deer approached food in a runway, comparing a current reward with the memory of a previous reward. We suggest that simultaneous negative contrast can influence foraging decisions in mammalian herbivores.
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| 2. |
- Bergvall, Ulrika A, et al.
(author)
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Associational effects of plant defences in relation to within- and between-patch food choice by a mammalian herbivore : neighbour contrast susceptibility and defence
- 2006
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In: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 147:2, s. 253-60
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Journal article (peer-reviewed)abstract
- A basic idea of plant defences is that a plant should gain protection from its own defence. In addition, there is evidence that defence traits of the neighbouring plants can influence the degree of protection of an individual plant. These associational effects depend in part on the spatial scale of herbivore selectivity. A strong between-patch selectivity together with a weak within-patch selectivity leads to a situation where a palatable plant could avoid being grazed by growing in a patch with unpalatable plants, which is referred to as associational defence. Quite different associational effects will come about if the herbivore instead is unselective between patches and selective within a patch. We studied these effects in a manipulative experiment where we followed the food choice of fallow deer when they encountered two patches of overall different quality. One of the two patches consisted of pellets with low-tannin concentration in seven out of eight buckets and with high concentration in the remaining bucket. The other patch instead had seven high- and one low-tannin bucket. We performed the experiment both with individuals one at a time and with a group of 16-17 deer. We found that the deer were unselective between patches, but selective within a patch, and that the single low-tannin bucket among seven high-tannin buckets was used more than a low-tannin bucket among other low-tannin buckets. This corresponds to a situation where a palatable plant that grows among unpalatable plants is attacked more than if it was growing among its own kind, and for this effect we suggest the term neighbour contrast susceptibility, which is the opposite of associational defence. We also found that the high-tannin bucket in the less defended patch was less used than the high-tannin buckets in the other patch, which corresponds to neighbour contrast defence. The neighbour contrast susceptibility was present both for individual and group foraging, but the strength of the effect was somewhat weaker for groups due to weaker within-patch selectivity.
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| 3. |
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| 4. |
- Bergvall, Ulrika A, et al.
(author)
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The effect of spatial scale on plant associational defences against mammalian herbivores
- 2008
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In: Ecoscience. - 1195-6860. ; 15, s. 343-348
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Journal article (peer-reviewed)abstract
- Intraspecific variation in plant toxins at different spatial scales can influence foraging decisions by wild herbivores. In order to investigate plant associational defences in relation to spatial scale, we performed an experiment with fallow deer encountering 2 patches of low- and high-tannin hazel branches. One patch was good, consisting of 7 low- and I high-tannin branch, and the other bad, with low- and 7 high-tannin branches. We kept the between-patch spatial scale constant and varied the within-patch spatial scale: the branches in a patch were either spread out or close together in a bundle. When the low-tannin branches were spread out, the deer showed a clear preference for low_tannin branches both patches and consumed similar amounts from low-tannin branches in the good and the bad patch, which means that there was no associational defence. In contrast, when the branches instead were together in a bundle, within-patch selectivity decreased and between-patch selectivity increased, and the low-tannin branches in the bad patch were less eaten than the low-tannin branches in the good patch, which corresponds to associational defence. We conclude that small inter-plant distances can be crucial for the operation of plant associational defences
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| 5. |
- Etzold, Sophia, et al.
(author)
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Nitrogen deposition is the most important environmental driver of growth of pure, even-aged and managed European forests
- 2020
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In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 458
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Journal article (peer-reviewed)abstract
- Changing environmental conditions may substantially interact with site quality and forest stand characteristics, and impact forest growth and carbon sequestration. Understanding the impact of the various drivers of forest growth is therefore critical to predict how forest ecosystems can respond to climate change. We conducted a continental-scale analysis of recent (1995–2010) forest volume increment data (ΔVol, m3 ha−1 yr−1), obtained from ca. 100,000 coniferous and broadleaved trees in 442 even-aged, single-species stands across 23 European countries. We used multivariate statistical approaches, such as mixed effects models and structural equation modelling to investigate how European forest growth respond to changes in 11 predictors, including stand characteristics, climate conditions, air and site quality, as well as their interactions. We found that, despite the large environmental gradients encompassed by the forests examined, stand density and age were key drivers of forest growth. We further detected a positive, in some cases non-linear effect of N deposition, most pronounced for beech forests, with a tipping point at ca. 30 kg N ha−1 yr−1. With the exception of a consistent temperature signal on Norway spruce, climate-related predictors and ground-level ozone showed much less generalized relationships with ΔVol. Our results show that, together with the driving forces exerted by stand density and age, N deposition is at least as important as climate to modulate forest growth at continental scale in Europe, with a potential negative effect at sites with high N deposition.
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| 6. |
- Huttunen, Piritta, et al.
(author)
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Leaf trichome production and responses to defoliation and drought in Arabidopsis lyrata (Brassicaceae)
- 2010
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In: Annales Botanici Fennici. - Helsinki : Finnish Zoological and Botanical Publishing Board. - 0003-3847 .- 1797-2442. ; 47:3, s. 199-207
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Journal article (peer-reviewed)abstract
- Leaf trichomes can protect plants against herbivory and drought, but can be costly to produce. Theory suggests that selection for reduced costs of resistance may result in the evolution of inducible defences. We quantified variation in tolerance to drought and defoliation, and tested the hypotheses that (a) tolerance is associated with cost, (b) leaf trichome production increases tolerance to drought, and (c) trichome production is increased in response to defoliation and drought stress in Arabidopsis lyrata (Brassicaceae). Eight maternal half-sib families were exposed to two watering regimes and four defoliation treatments in a factorial design. Tolerance to drought varied among families and was inversely related to leaf size, but was not related to trichome density. Family mean performance in the low-watering treatment tended to correlate negatively with that in the control treatment. Trichome production was not induced by defoliation or drought stress. The results suggest that there is genetic variation in tolerance to drought in the study population, that tolerance to drought is associated with a cost, and that trichome production does not increase tolerance to drought in A. lyrata.
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| 7. |
- Rautio, Pasi, et al.
(author)
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Bitter problems in ecological feeding experiments: commercial tannin preparations and common methods for tannin quantifications
- 2007
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In: Biochemical systematics and ecology. - : Elsevier BV. - 0305-1978. ; 35:5, s. 257-262
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Journal article (peer-reviewed)abstract
- In the field of plant-herbivore interactions research methods manipulating plant secondary metabolites are becoming more and more popular. In most cases food offered to herbivores is manipulated with commercially available compounds, or more specifically, compound mixtures. Among the most commonly used is tannic acid, the almost sole commercial source of hydrolysable tannins. However, recent studies have shown that different tannic acid preparations are not comparable in their tannin structures. While tannic acids are meant to contain only gallotannins (GTs), some commercial preparations compose mainly of more simple galloglucoses (that have e.g. much lower protein precipitation capacity than GTs) or even of gallic acid (the hydrolysis product of GTs). Another commonly used group of tannins used in feeding trials is condensed tannins (CTs), usually in the form of quebracho tannin. One of the problems in using quebracho is that it contains different CT structures than e.g. leaves of many deciduous trees. Additionally, when analysed with the common acid-butanol assay for total CTs, quebracho tannins give even 30-fold lower absorbance than the CTs of those deciduous trees. This dilemma is highlighted by the fact that quebracho tannin is commonly used as a standard when analysing CT concentrations in plant tissues. In addition to above problems, different herbivore species are known to react differently to varying tannin structures. Therefore, ecologically the most serious concern lies in that our commercial tannin compounds might have biological activities highly different from the tannins of our study plants. Below we discuss these problems, as well as some means to deal with them.
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| 8. |
- Rautio, Pasi, et al.
(author)
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Food selection by herbivores and neighbourhood effects in the evolution of plant defences
- 2012
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In: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 49:1-2, s. 45-57
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Journal article (peer-reviewed)abstract
- A number of studies have reported how neighbouring plants may influence herbivory on palatable or unpalatable plants. Such neighbourhood effects can have important evolutionary consequences as they may either promote the evolutionary stability of plant defences or, alternatively, select against the fixation of plant defences and instead promote a stable polymorphism of palatable and unpalatable plants. These consequences depend on whether the difference in herbivore damage between unpalatable and palatable plants is smaller or, alternatively, greater when the neighbours are unpalatable instead of palatable. Such relations can arise when the neighbourhood effects are non-parallel among palatable and unpalatable plants. We outline two basic situations of non-parallel neighbourhood effects and illustrate how they can come about. A detailed dissection of these interactions reveals that there are several qualitatively distinct mechanisms that promote either evolutionary stability of plant defences or alternatively polymorphism. Our classification of mechanisms can be used to clarify and explain observations obtained in the field of plant herbivore interactions and predator prey interactions, both at the population and the community level.
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| 9. |
- Rautio, Pasi, et al.
(author)
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Lean forestry – A paradigm shift from economies of scale to precise and sustainable use of ecosystem services in forests
- 2023
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In: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 530
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Journal article (peer-reviewed)abstract
- Modern forestry practices are based on the idea of ‘big is beautiful’. Especially in the regeneration phase, the operations are often excessive in relation to the profit that one can expect to gain in decades to come. Excessive operations also constrain the use of ecosystem services. Lean forestry is a novel philosophy of forestry practise that aims to direct the idea of “big is beautiful” in modern silviculture more into “do cost effectively only what is needed to fulfil the goals”. To succeed Lean forestry requires exact spatial information to be able to carry out forestry measures very precisely only where they are really needed to fulfil goals. This kind of a paradigm shift requires systems with new kinds of abilities to remotely sense the surrounding environment and to make better and faster decisions based on sensed data. Automated unmanned offroad vehicle that is able to sense the environment and to make lean decisions is presented as an example of initiatives that can make forestry more cost-effective and simultaneously improve utilisation of wide range of ecosystem services in forests.
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| 10. |
- Rautio, Pasi, et al.
(author)
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Spatial scales of foraging in fallow deer: Implications for associational effects in plant defences
- 2008
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In: Acta Oecologica. - : Elsevier BV. - 1146-609X. ; 34
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Journal article (peer-reviewed)abstract
- Large herbivores select food at several spatial scales: plant communities are chosen at a landscape scale, plant patches are chosen within a plant community, and individual plants within a patch. Foraging decision at the patch level can result in associational effects in plant communities and populations. Several studies have shown that herbivore attack and consumption rates may not only depend on a plant's own defence traits, but also on the defence traits of its neighbours. In the present experiment we investigated whether the spatial scale of the food distribution affects food selection by fallow deer and whether the foraging behaviour gives rise to associational effects in plant defences. In a population of captured wild fallow deer we simulated a natural situation where two separate plant patches are exposed to intense herbivory pressure. We presented different spatial arrangements of low- and high-tannin food to the deer, varying the frequency of the feeder types within and between patches. We found that the deer consumed palatable food among the unpalatable food on average as much as they consumed palatable food among other palatable feeders. However, when unpalatable food occurred among the palatable food it was more consumed than among other unpalatable feeders. Hence, we did not find support for associational defence, but our results supported associational susceptibility. At the between patch level a patch of mainly high-tannin feeders was consumed less when presented near to a patch of mainly low-tannin feeders, suggesting that for well-defended plants having palatable neighbours in a nearby patch might accentuate the effectiveness of their defence.
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