Tree defenses, variability

In fact, there are at least 3 possible solutions. All three have one thing in common they focus on the rapidly-growing body of evidence that trees are not uniform in defensive chemistry. Instead, most plants are highly complex, dynamic mosaics of variable chemistry and nutrient value. This observation suggests ways in which defensive chemistry may remain effective over many insect generations ... 

I suggest that variable plant chemistry, by restricting resource availability and focusing the activities of herbivores on a few tissues, promotes compromises between food-finding and risks from natural enemies which are not readily countered by most insects. The spatial and temporal heterogeneity which appears to be common in forest trees is the most important part of the tree s defensive system, and is the only way a plant s chemical defenses can remain effective over evolutionary time. This variable impact on natural enemies may be more important in regulating consumption than any single factor can be. 

LIEUTIER, F., GARCIA, J., ROM ARY, P., YART, A., JACTEL, H., SAUVARD, D., Inter-tree variability in the induced defense reaction of Scots pine to single inoculations by Ophiostoma brunneo-ciliatum, a bark-beetle-associated fungus, For. Ecol. Manage., 1993, 59, 257-270. 

To quantify flood risks, state of the art modeling techniques combine (i) probability density functions of hydraulic conditions (ii) probability density functions of the variables that determine the load bearing capacity of a flood defense, (iii) fault tree models to analyze failure modes, and (iv) flood propagation models, land-use data and loss functions to relate flood characteristics and land-use data to the consequences of flood scenarios (e.g. Van Manen Brinkhuis 2005). This paper focuses on the quantification of loss of life for a given flood scenario. The quantification of flood probabilities and flood characteristics (such as flow velocities, rise rates, and inundation depths) is outside the scope of the present paper and discussed in e.g. Steenbergen et al. (2004). 

Inside forest trees under water stress, the plugging of sieve-plate pores with P-protein is an almost instantaneous reaction to pressure release in active sieve tubes. P-protein plugs, or slime plugs, are now thought of as the first line of defense against the loss of assimilates. Wound callose further strengthens the cell s defenses but at variable rates (44 cf.. Sect. 5.1.3.4). 

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