Hyönteistuhoriskien hallinta uusilla teknologioilla

Tieteen tori: Luonnonvarariskien hallint

Response of Soil Surface Respiration to Storm and Ips typographus (L.) Disturbance in Boreal Norway Spruce Stands

Disturbances such as storm events and bark beetle outbreaks can have a major influence on forest soil carbon (C) cycling. Both autotrophic and heterotrophic soil respiration may be affected by the increase in tree mortality. We studied the effect of a storm in 2010 followed by an outbreak of the European spruce bark beetle (Ips typographus L.) on the soil surface respiration (respiration by soil and ground vegetation) at two Norway spruce (Picea abies L.) dominated sites in southeastern Finland. Soil surface respiration, soil temperature, and soil moisture were measured in three types of plots—living trees (undisturbed), storm-felled trees, and standing dead trees killed by I. typographus—during the summer–autumn period for three years (2015–2017). Measurements at storm-felled tree plots were separated into dead tree detritus-covered (under storm-felled trees) and open-vegetated (on open areas) microsites. The soil surface total respiration for 2017 was separated into its autotrophic and heterotrophic components using trenching. The soil surface total respiration rates at the disturbed plots were 64%–82% of those at the living tree plots at one site and were due to a decrease in autotrophic respiration, but there was no clear difference in soil surface total respiration between the plots at the other site, due to shifts in either autotrophic or heterotrophic respiration. The soil surface respiration rates were related to plot basal area (living and all trees), as well as to soil temperature and soil moisture. As storm and bark beetle disturbances are predicted to become more common in the future, their effects on forest ecosystem C cycling and CO2 fluxes will therefore become increasingly important

Hemlokin villakirvan nissimallit invaasion kattamasta Pohjois-Amerikan levinneisyysalueesta ja projektiot alkuperäiseltä levinneisyysalueelta ja tulevaisuuden ilmastosta

The hemlock woolly adelgid (Adelges tsugae Annand - HWA) is invasive in eastern North America where it causes extensive mortality to hemlock communities. The future of these communities under projected climate change is an issue of landscape ecological interest and speculation. We employed the MaxEnt algorithm with the random subset feature selection algorithm (RSFSA) in creating HWA niche models. Final models were ensembles of 12 statistically best models with six predictors each. Out of 119 climatic, topographic, and soil variables, 42 were used in at least one final model. Soil features, followed by climate and topographic features, were most common in selected models. The three most important variables among all models were November potential evapotranspiration, slope, and percent Ochrepts soil. The potential distributions of HWA within eastern North America were projected under historical and four future climate scenarios for 2050 and 2070 under low and high CO2 emissions. The mean of the minimum values for the minimum temperature of the coldest month from the 12 MaxEnt model projections in eastern North America was -15.8°C. This value was close to -15°C, the extreme minimum temperature found for both HWA occurrence points and previously reported HWA cold temperature limits. These results indicate that HWA may be close to equilibrium distribution in eastern North America under current climate. We also reverse-casted the eastern North American MaxEnt model back onto the HWA native ranges in eastern Asia and western North America. The projections match best with native ranges in Asian islands, such as Japan, and the Cascade Mountains in western North America. Statistically significant HWA range shifts of 221-468 km northwards and 110-164 km eastwards were projected by the 12 models for 2050-2070. The 2070 high CO2 emission scenario models projects HWA suitability throughout most of the northern range of eastern hemlock.Peer reviewe

Influence of soil and topography on defoliation intensity during an extended outbreak of the common pine sawfly (Diprion pini L.)

Insect herbivore disturbances are likely to intensify as a consequence of climate change. In Finland, outbreaks of the common pine sawfly (Diprion pini L.), which feeds on Scots pine (Pinus sylvestris L.) needles, and resulting damage to forests have already increased. Although drivers of sawfly outbreak dynamics have been investigated, the effects of topography and soil fertility have not been fully elucidated. We studied the effect of elevation, slope and soil properties (carbon and nitrogen contents, C/N ratio, pH, texture and horizon thicknesses) on the defoliation intensity of 28 plots (227-531 m(2)), located in a 34.5 km(2) forested area in eastern Finland suffering from an extended outbreak of D. pini. Plot elevation and slope (relative relief 35 m, maximum elevation 200 m a. s.l.) were derived from a digital elevation model and the soil properties from samples of the humus layer (Of + Oh), (Ah+) E and B horizons of podzol profiles. Defoliation was greater on the more fertile and flatter sites than on less fertile and steeper sites, but independent of elevation. The soil property most strongly correlated to plot mean defoliation was the C/N ratio of the humus layer (Spearman's rho = -0.68). However, logistic modelling showed that the thickness of the (Ah+) E-horizon had the highest classification accuracy in predicting the probability of a plot having moderate to severe (> 20%) defoliation. Our study showed that forest damage caused by D. pini was related to topography and soil fertility. Taking these factors into account could help in understanding the population dynamics of D. pini, in modeling of insect outbreaks and in forest management planning.Peer reviewe

Development of a method for monitoring of insect induced forest defoliation - limitation of MODIS data in Fennoscandian forest landscapes

We investigated if coarse-resolution satellite data from the MODIS sensor can be used for regional monitoring of insect disturbances in Fennoscandia. A damage detection method based on z-scores of seasonal maximums of the 2-band Enhanced Vegetation Index (EVI2) was developed. Time-series smoothing was applied and Receiver Operating Characteristics graphs were used for optimisation. The method was developed in fragmented and heavily managed forests in eastern Finland dominated by Scots pine (Pinus sylvestris L.) (pinaceae) and with defoliation of European pine sawfly (Neodiprion sertifer Geoffr.) (Hymenoptera: Diprionidae) and common pine sawfly (Diprion pini L.) (Hymenoptera: Diprionidae). The method was also applied to subalpine mountain birch (Betula pubescens ssp. Czerepanovii N. I. Orlova) forests in northern Sweden, infested by autumnal moth (Epirrita autumnata Borkhausen) and winter moth (Operophtera brumata L.). In Finland, detection accuracies were fairly low with 50% of the damaged stands detected, and a misclassification of healthy stands of 22%. In areas with long outbreak histories the method resulted in extensive misclassification. In northern Sweden accuracies were higher, with 75% of the damage detected and a misclassification of healthy samples of 19%. Our results indicate that MODIS data may fail to detect damage in fragmented forests, particularly when the damage history is long. Therefore, regional studies based on these data may underestimate defoliation. However, the method yielded accurate results in homogeneous forest ecosystems and when long-enough periods without damage could be identified. Furthermore, the method is likely to be useful for insect disturbance detection using future medium-resolution data, e. g. from Sentinel-2.Peer reviewe

Storm and Ips typographus disturbance effects on carbon stocks, humus layer carbon fractions and microbial community composition in boreal Picea abies stands

Tree-killing forest disturbances such as storms and bark beetle outbreaks can lead to notable changes in the carbon (C) balance and functioning of forest ecosystems. In this study, the effects of a storm in 2010 followed by an outbreak of European spruce bark beetle (Ips typographus L.) on tree, litter and soil C stocks as well as humus layer C fractions and microbial community composition were examined in boreal Norway spruce (Picea abies L.) stands. Tree (aboveground), litter detritus (distinguishable twig, bark and cones) and soil (humus layer and 0-6 cm mineral soil) C stocks were quantified for undisturbed (living trees), storm disturbed (in 2010) and I. typographus disturbed (tree mortality in circa 2013-2014) plots in 2015-2016. Additional humus layer samples were collected in 2017 for determination of total microbial biomass C, ergosterol (fungal biomass indicator) and K2SO4 extractable (labile) C concentrations, as well as fungal and bacterial community composition (DNA sequencing). Ectomycorrhizal (ECM) fungal mycelial growth in topsoil was also quantified. In spite of the differing initial development and intensity of the two disturbance types, there was little difference in humus layer C and microbiology between the storm and bark beetle disturbed plot types at the time of the study. This may be due to the longer time since the disturbance at the storm disturbed plots. The shift from tree biomass to necromass C stocks was not reflected in differences in SOC stocks or humus layer extractable C concentrations between undisturbed and disturbed plot types, but the amount of litter detritus on forest floor was similar (storm) or higher (beetle) in disturbed plots in comparison to undisturbed ones. Humus layer microbial biomass C and ergosterol concentrations and ECM fungal abundance were lower on disturbed plots in comparison to undisturbed plots. The disturbed plots were also indicated to have a slightly higher abundance of some saprotrophic fungi. Differences in the effects of the two disturbance types may occur when studied at differing spatial scales and at different times after disturbance. To understand the full impact of such disturbances on forest functioning and C balance, long-term monitoring studies will be required.Peer reviewe

Impacts of natural enemies and stand characteristics on cocoon mortality of the pine sawfly Diprion pini in a Fennoscandian boreal forest.

Peer reviewe

Classification of Defoliated Trees Using Tree-Level Airborne Laser Scanning Data Combined with Aerial Images

Climate change and rising temperatures have been observed to be related to the increase of forest insect damage in the boreal zone. The common pine sawfly (Diprion pini L.) (Hymenoptera, Diprionidae) is regarded as a significant threat to boreal pine forests. Defoliation by D. pini can cause severe growth loss and tree mortality in Scots pine (Pinus sylvestris L.) (Pinaceae). In this study, logistic LASSO regression, Random Forest (RF) and Most Similar Neighbor method (MSN) were investigated for predicting the defoliation level of individual Scots pines using the features derived from airborne laser scanning (ALS) data and aerial images. Classification accuracies from 83.7% (kappa 0.67) to 88.1% (kappa 0.76) were obtained depending on the method. The most accurate result was produced using RF with a combination of data from the two sensors, while the accuracies when using ALS and image features separately were 80.7% and 87.4%, respectively. Evidently, the combination of ALS and aerial images in detecting needle losses is capable of providing satisfactory estimates for individual trees.Peer reviewe

Classification of Needle Loss of Individual Scots Pine Trees by Means of Airborne Laser Scanning

Forest disturbances caused by pest insects are threatening ecosystem stability, sustainable forest management and economic return in boreal forests. Climate change and increased extreme weather patterns can magnify the intensity of forest disturbances, particularly at higher latitudes. Due to rapid responses to elevating temperatures, forest insect pests can flexibly change their survival, dispersal and geographic distributions. The outbreak pattern of forest pests in Finland has evidently changed during the last decade. Projection of shifts in distributions of insect-caused forest damages has become a critical issue in the field of forest research. The Common pine sawfly (Diprion pini L.) (Hymenoptera, Diprionidae) is regarded as a significant threat to boreal pine forests. Defoliation by D. pini has resulted in severe growth loss and mortality of Scots pine (Pinus sylvestris L.) (Pinaceae) in eastern Finland. In this study, tree-wise defoliation was estimated for five different needle loss category classification schemes and for 10 different simulated airborne laser scanning (ALS) pulse densities. The nearest neighbor (NN) approach, a nonparametric estimation method, was used for estimating needle loss of 701 Scots pines, using the means of individual tree features derived from ALS data. The Random Forest (RF) method was applied in NN-search. For the full dense data (~20 pulses/m2), the overall estimation accuracies for tree-wise defoliation level varied between 71.0% and 86.5% (kappa-values of 0.56 and 0.57, respectively), depending on the classification scheme. The overall classification accuracies for two class estimation with different ALS pulse densities varied between 82.8% and 83.7% (kappa-values of 0.62 and 0.67, respectively). We conclude that ALS-based estimation of needle losses may be of acceptable accuracy for individual trees. Our method did not appear sensitive to the applied pulse densities.Peer reviewe