Valuing the Impact of Forest Disturbances on the Climate Regulation Service of Western U.S. Forests

The protection and expansion of forest carbon sinks are critical to achieving climate-change mitigation targets. Yet, the increasing frequency and severity of forest disturbances challenge the sustainable provision of forest services. We investigated patterns of forest disturbances’ impacts on carbon sinks by combining spatial datasets of forest carbon sequestration from biomass growth and emissions from fire and bark beetle damage in the western United States (U.S.) and valued the social costs of forest carbon losses. We also examined potential future trends of forest carbon sinks under two climate-change projections using a global vegetation model. We found that forest carbon losses from bark-beetle damage were larger than emissions from fires between 2003 and 2012. The cumulative social costs of forest carbon losses ranged from USD 7 billion to USD 72 billion, depending on the severity of global warming and the discount rate. Forest carbon stocks could increase around 5% under Representative Concentration Pathway (RCP) 4.5 or 7% under RCP 8.5 by 2091 relative to 2011 levels, mostly in forests with high net primary productivity. These results indicate that spatially explicit management of forest disturbances may increase forest carbon sinks, thereby improving opportunities to achieve critical climate-change mitigation goals.

Estimation of Yield Loss of Jatropha Curcas Due to Aphthona Whitfieldi in Burkina Faso

In Burkina Faso, the leaf beetle Aphthona whitfieldi is the main insect pest of the biofuel plant Jatropha curcas. The beetle affects plant growth and seed yield, but the impact on yield has never been properly quantified. This study was conducted on-station and on-farm in the district of Léo, southern Burkina Faso, in 2015. It aimed at evaluating the yield losses that A. whitfieldi inflicts to J. curcas. The first experiment used 25 caged trees in their first year of fruit production, on which various amounts of beetles were released. When 200 beetles were released, the defoliation level reached 55% and caused 61% of yield loss. Releases of 400 or more beetles caused a defoliation level of at least 74% and seed losses of 98%. On-farm observations were made on attack levels and seed yields in three different types of plantations, i.e. pure plantations, plantations intercropped with food crops and hedges. These observations showed that defoliation levels over 50% were common in the three types of plantations, resulting in very low yields. This study shows the importance of beetle damage in the cultivation of J. curcas. This is likely one of the reasons for the very low yields, which, among other causes, led to the abandonment of J. curcas plantations in the region.

The Effects of Landscape Structure and Stand-Scale Factors on Dendroctonus Valens Damage Under Disturbance Conditions in North China

Background In recent years, the red turpentine beetle (Dendroctonus valens, RTB), an invasive pest species has spread northward along the distribution of pine forests, forming a potential threat to healthy pine forests in North China. Previous studies have shown that natural (e.g., fire) and human (e.g., felling) disturbances can significantly promote bark beetle damage. However, few studies have considered the effect of multi-scale factors on bark beetle damage under disturbance conditions. Here, we investigated RTB damage (entrance holes) in 98 forest stands with and without disturbance (fire or stolen felling) in the Heilihe National Nature Reserve, Inner Mongolia, which is considered to be in the early stage of RTB outbreak. We assessed the effects of forest landscape structure (forest proportion and host connectivity) and stand-scale characteristics on RTB damage under different disturbance conditions (presence or absence). In addition, we also explored the effects of fire and stolen felling disturbance on RTB damage and the significant differences between them. Result Disturbance (i.e., fire and stolen felling) could significantly promote the occurrence of RTB and there was no significant difference between the two types of disturbance. In the absence of disturbance, small stand-scale factors (i.e., aspect and canopy cover) played important roles in the prediction of RTB damage. In the presence of disturbance, forest proportion within a radius of 250 m was the main factor affecting RTB invasion. Higher forest coverage could reduce the migration of RTB from the surrounding environment to the disturbance area, thus reducing RTB damage. In addition, we observed a positive relationship between elevation and RTB invasion. Conclusion Landscape structure and stand-scale factors had different effects on RTB invasion under different disturbance conditions. This study not only provides new insights into understanding the roles played by multi-scale factors in RTB damage but also assists in the implementation of pest management programs.

The First Record of Tortoise Beetle Damage to Sugar Beet in the UK: Is Global Warming Responsible?

The authors thought they had experienced everything that the sugar beet crop could throw at them from a pest point of view after almost 40 years of working with the sugar beet industry. It was therefore very exciting to be confronted with a highly unusual pest this summer, so unusual that its presence in high numbers causing significant damage to a sugar beet crop in Norfolk in August 2021, is the first record of such damage in the UK. The pest was the exotic tortoise beetle, Cassida nebulosa, which the sugar beet bible, Pests, Diseases and Disorders of Sugar Beet, published by the International Institute de la Recherches Betteraves (IIRB), describes as rare, and never important in northern Europe. Indeed, this species has never, in our memory, been recorded before as a pest in sugar beet in the UK, only a very rare presence. Dewar and Cooke (2006) stated in their review of pest problems in sugar beet the UK, that crop damage by tortoise beetles never occurs in western Europe, but can be severe in warmer Mediterranean regions and in Russia.

Effects of Forest Structure On Dendroctonus Valens Damage Under Natural and Human Disturbances

Background In recent years, the red turpentine beetle (Dendroctonus valens, RTB), an invasive pest species has spread northward along the distribution of pine forests, forming a potential threat to healthy pine forests in North China. Previous studies have shown that natural (e.g., fire) and human (e.g., felling) disturbances can significantly promote bark beetle damage. However, few studies have considered the effect of forest landscape structure on bark beetle damage under disturbance conditions. Here we used generalized linear models and generalized linear mixed models to explore the effects of multi-scale factors on RTB damage under different disturbance conditions (presence or absence) in 109 forest stands in the Heilihe National Nature Reserve, Inner Mongolia. Result Disturbance (i.e., fire and stolen felling) could significantly promote the occurrence of RTB. In the absence of disturbance, small-scale stand factors (i.e., aspect and canopy density) played important roles in the prediction of RTB damage. In the presence of disturbance, forest landscape structure (i.e., forest isolation) was the main factor affecting RTB invasion. Conclusion In the presence of disturbance, the forest structure played an important role in the process of the diffusion of RTB from the surrounding habitat to the disturbance. This study, which emphasizes the potential importance of forest landscape structure on RTB spread, not only provides new insights into understanding the roles of large-scale factors but also assists in the implementation of pest management programs.

Productivity and Profitability of Poplars on Fertile and Marginal Sandy Soils under Different Density and Fertilization Treatments

We evaluated the productivity and profitability of four highly productive poplars including Populus deltoides × P. deltoides (DD ‘140’ and ‘356’), P. deltoides × P. maximowiczii (DM ‘230’), and P. trichocarpa × P. deltoides (TD ‘185’) under two densities (2500 and 5000 trees ha−1), and three fertilization treatments (0, 113, 225 kg nitrogen ha−1) at three sandy coastal sites varying in soil quality. Green stem biomass (GSB) was estimated from the sixth-year stem diameter. Leaf-rust (Melampsora castagne) and beetle damage (by Chrysomela scripta Fabricius), the leaf area index (LAI) and foliar nitrogen, were measured in year two. At all sites, DD and DM had higher survival (>93%) than TD (62–83%). DD produced greater GSB (92.5–219.1 Mg ha−1) than DM (54–60.2 Mg ha−1) and TD (16.5–48.9 Mg ha−1), and this was greater under the higher density (85.9–148.6 Mg ha−1 vs. 55.9–124.9 Mg ha−1). Fertilization significantly increased GSB on fertile soil but not marginal soils; a higher rate did not significantly enhance GSB. Leaf rust was higher for fertile soil (82%) than marginal soils (20–22%), and TD ‘185’ (51% vs. others 34%). C. scripta damage was higher for the higher density (+42%) than lower density, and TD ‘185’ (50% vs. others >38%). LAI was higher on fertile soil (1.85 m2 m−2) than marginal soils (1.35–1.64 m2 m−2), and under the lower density (1.67 m2 m−2 vs. 1.56 m2 m−2). The high GSB producer DD ‘356’ had the lowest LAI (1.39 m2 m−2 vs. 1.80 m2 m−2). Foliar nitrogen varied among genomic groups (DD ‘140’ 1.95%; TD ‘185’ 1.80%). Our plots were unprofitable at a 27 USD Mg−1 delivered price; the biggest profitability barriers were the high costs of higher density establishment and weed control. The best-case treatment combinations of DD (‘140’, ‘356’) would be cost-effective if the price increased by 50% (USD 37.54 Mg−1) or rotations were 12 years (fertile-soil) and longer (marginal soils). The requirement for cost-effectiveness of poplars includes stringent and site-specific weed control which are more important than fertilizer applications.

Long-Term Trends of Hazel Grouse (Tetrastes bonasia) in the Bohemian Forest (Šumava), Czech Republic, 1972–2019

The population dynamics of Hazel Grouse were studied by presence/absence recording at stationary sites along fixed routes (110 km) in the central part of Šumava (Bohemian Forest, Czech Republic) from 1972 to 2019. The 100 km2 study area covered altitudes between 600 m (Rejštejn) and 1253 m above sea level (Mt. Sokol). Our database contained indices of Hazel Grouse occupancy: positive sites/visited sites for a yearly increasing number of Hazel Grouse occurrence sites (n = 134) for 48 years. We used a loglinear Poisson regression method to analyze the long-term population trend for Hazel Grouse in the study area. In the period from 1972 to 2006 we found a stable Hazel Grouse population (p = 0.83). From 2006–2007 to 2019, the population index dropped (−3.8% per year, p < 0.05). This decline is assumed to be influenced by habitat loss due to succession, resulting in older, more open forest stands, by strongly increasing forestry and windstorm “Kyrill”, followed by clear cutting, bark beetle damage, and the removal of pioneer trees in spruce plantations, which diminished buds and catkins, the dominant winter food of Hazel Grouse. The influence of disturbance by increasing tourist activities and/or predation is also discussed. Our results could help to optimize the conservation efforts for Hazel Grouse in the Bohemian Forest.

Long-Term Trends of Hazel Grouse (Tetrastes bonasia) in the Bohemian Forest (Šumava), Czech Republic, 1972-2019

The population dynamics of Hazel Grouse was studied by presence/ absence recording at stationary sites along fixed routes (110 km) during 1972-2019 in the central part of the Bohemian Forest (&Scaron;umava, Czech Republic). The 100-km&sup2; study area covered altitudes between 600 m (Rejstejn) and 1,253 m a.s.l., (mount Sokol). Our data base contained indices of Hazel Grouse occupancy: positive sites/ controlled sites for a yearly increasing number of Hazel Grouse occurrence sites (N = 134) for 48 years. We used a loglinear Poisson-regression method to analyze the long-term population trend for Hazel Grouse in the study area. In the period 1972 to 2006 we found a stable Hazel Grouse population (p = 0.83). From 2006-2007 to 2019, the population index dropped (-3.8% per year, p &amp;lt; 0.05) for the last 13 years. This decline is assumed to be influenced by habitat loss due to succession resulting in older, more open forest stands, by strongly increasing forestry and windstorm &ldquo;Kyrill&rdquo; followed by clear cutting, bark-beetle damage, and removal of pioneer trees in spruce plantations, which diminished buds and catkins, the dominant winter food. The influence of disturbance by increasing touristic activities and/or predation is discussed. Our results could help to optimize conservation efforts for Hazel Grouse in the Bohemian Forest.