The arrival of novel pathogens and pests can have a devastating effect on the market values of forests. Calibrating management strategies/decisions to consider the effect of disease may help to reduce disease impacts on forests. Here, we use a novel generalisable, bioeconomic model framework, which combines an epidemiological compartmental model with a Faustmann optimal rotation length model, to explore the management decision of when to harvest a single rotation, even-aged, plantation forest under varying disease conditions. Sensitivity analysis of the rate of spread of infection and the effect of disease on the timber value reveals a key trade-off between waiting for the timber to grow and the infection spreading further. We show that the optimal rotation length, which maximises the net present value of the forest, is reduced when timber from infected trees has no value; but when the infection spreads quickly, and the value of timber from infected trees is non-zero, it can be optimal to wait until the disease-free optimal rotation length to harvest. Our original approach provides an exemplar framework showing how a bioeconomic model can be used to examine the effect of tree diseases on management strategies/decisions.

Livestock farmers in Newfoundland use most available land for forages. The local production of feed grains is negligible and expensive imported feed accounts for almost one half of farm operating expenses. Here, our objectives were to develop basic agronomic principles of mechanized spring grain production and to demonstrate grain production techniques to the Newfoundland farming community. Barley seeding date trials were conducted at five environments in eastern and western Newfoundland between 1996 and 1998. The relationship between soil pH and barley grain yield was explored through grid soil and yield sampling in two large fields in both 1997 and 1998. Between 1993 and 1998 over 20 livestock farmers throughout Newfoundland cooperated with the Newfoundland Grain Project, growing and comparing varieties of barley (Hordeum vulgare L.), spring wheat (Triticum aestivum L.) and oats (Avena sativa L.) on their farms. Late seeding of barley in the spring/summer resulted in linear grain yield reductions. A levelling off of yield response did not occur at greater cumulated growing degree days, possibly because optimum accumulation for maximum barley yield potential does not occur in Newfoundland. Resistant regression lines, describing the relationship between soil pH and grain yield were developed for two barley varieties, indicated that Sterling reached a yield plateau around a soil pH 6 in 1998, while Chapais reached a yield plateau at soil pH 5.4 in 1997. Barley is well adapted to Newfoundland growing conditions, normally providing a high-yielding, mature grain of good feeding quality. Farmers collaborating with the project were generally impressed with the potential of growing barley for grain and some are now regularly doing so. Key words: Seeding date; barley; wheat; oats; precision farming research

HighlightsNovel bioeconomic model assesses effect of tree disease on tree species mixtures.Risk and damage of disease alters the optimal planting proportion of two species.Diversifying reduces loss from disease even if resistant species benefit is small.Optimal planting proportion sensitive to disease characteristics and economic loss.

Forests deliver multiple benefits both to their owners and to wider society. However, a wave of forest pests and pathogens is threatening this worldwide. In this paper we examine the effect of disease on the optimal rotation length of a single-aged, single rotation forest when a payment for non-timber benefits, which is offered to private forest owners to partly internalise the social values of forest management, is included. Using a generalisable bioeconomic framework we show how this payment counteracts the negative economic effect of disease by increasing the optimal rotation length, and under some restrictive conditions, even makes it optimal to never harvest the forest. The analysis shows a range of complex interactions between factors including the rate of spread of infection and the impact of disease on the value of harvested timber and non-timber benefits. A key result is that the effect of disease on the optimal rotation length is dependent on whether the disease affects the timber benefit only compared to when it affects both timber and non-timber benefits. Our framework can be extended to incorporate multiple ecosystem services delivered by forests and details of how disease can affect their production, thus facilitating a wide range of applications.

Emerging infectious diseases are a substantial threat to native populations. The spread of disease through naive native populations will depend on both demographic and disease parameters, as well as on habitat suitability and connectivity. Using the potential spread of squirrelpox virus (SQPV) on the Isle of Arran as a case study, we develop mathematical models to examine the impact of an emerging disease on a population in a complex landscape of dierent habitat types. Furthermore, by considering a range of disease parameters, we infer more generally how complex landscapes interact with disease characteristics to determine the spread and persistence of disease. Specic ndings indicate that a SQPV outbreak on Arran is likely to be short lived and localised to the point of introduction allowing recovery of red squirrels to pre-infection densities; this has important consequences for the conservation of red squirrels. More generally, we nd the extent of disease spread is dependent on the rare passage of infection through poor quality corridors connecting good quality habitats. Acute, highly transmissible infectious diseases are predicted to spread rapidly causing high mortality. Nonetheless the disease typically fades out following local epidemics and is not supported in the long-term. A chronic infectious disease is predicted to spread more slowly but can remain endemic in the population. This allows the disease to spread more extensively in the long-term as it increases the chance of spread between poorly connected populations. Our results highlight how a detailed understanding of landscape connectivity is crucial when considering conservation strategies to protect native species from disease threats.