INTRODUCTION

Insect pests are globally important drivers of forest landscape dynamics due to their impact on key forest components, including vegetation structure and composition, water and nutrient cycling, and wildlife habitat (Adams et al., 2009; Boon, 2012; Dale et al., 2001; Hicke et al., 2012; Mcshea et al., 2007; Veblen et al., 1991). Given the importance of climate to the physiological and ecological determinants of pest distribution and dynamics, climate change is indirectly affecting forests by altering the range, frequency, or severity of pest outbreaks (Ayres & Lombardero, 2000; Deutsch et al., 2008; Dukes et al., 2009; Jactel et al., 2019; Logan et al., 2003; Pureswaran et al., 2018). Such climate change-induced alterations to historic disturbance regimes can present novel ecological effects and management challenges.

As temperatures rise, there are a growing number of examples of phytophagous insect populations expanding their ranges (Carroll et al., 2003; Dale et al., 2001; Jepsen et al., 2008; Niemelä et al., 2001; Parmesan, 2006; Pureswaran et al., 2018). One of the most well-understood examples has occurred among bark beetles (Coleoptera: Curculionidae: Scolytinae) in North America. Southern pine beetle [Dendroctonus frontalis Zimmermann (SPB)] is a bark beetle whose wide-scale ecologic, economic, and social impacts have deemed it one of most destructive pests of pine forests (Clarke & Nowak, 2009; Coulson & Klepzig, 2011; Dodds et al., 2018; Payne, 1980; Price et al., 2006). Despite its short generation time, high dispersal capabilities, and wide host distribution, SPB's lower lethal air temperature (−16°C) has historically limited it to the south-eastern United States, Mexico, and Central America, with northern populations reaching Ohio, Pennsylvania, and Maryland (Payne, 1980; Price et al., 2006; Ungerer et al., 1999). However, warming minimum winter air temperatures in the last two decades have enhanced beetle fitness at northern distributions and allowed for damaging populations to expand (Lesk et al., 2017; Ungerer et al., 1999; Weed et al., 2013).

The ongoing northward expansion of SPB threatens ecosystems dominated by potential host species with limited historical exposure to the beetle, including the globally rare north-eastern pitch pine barrens (Lesk et al., 2017; Tran et al., 2007; Ungerer et al., 1999; Williams & Liebhold, 2002). In SPB-infested pine barrens, high levels of mortality in canopy pitch pine (Pinus rigida Mill.) are accelerating the ongoing transition of open-canopy, fire-dependent pitch pine barrens to forests dominated by less pyrophilic species like oaks (genus Quercus), red maple (Acer rubrum L.), and white pine (Pinus strobus L.;(Heuss et al., 2019; Howard et al., 2011; Nowacki & Abrams, 2008). SPB damage may extend to more northern pine barrens as SPB-suitable climates are expected to reach 78% of pitch pine forests by 2050 (Lesk et al., 2017).

SPB populations follow a pulse eruptive cycle in which favourable environmental conditions lead to irregular explosive population growth and the death of a large portion of host species (Berryman, 1986). During these outbreaks, semiochemical communication between SPB organizes mass attacks that can overwhelm resin defence systems of healthy trees and cause host death in a matter of days to weeks (Hain et al., 2011; Hassett et al., 2017; Sullivan, 2011). Incidences of SPB infestation in the south-eastern United States have been reduced in some stands through the application of forest management treatments such as stand thinning and prescribed burning that promote stand vigour and disrupt SPB pheromonal communication (Brown et al., 1987; Burkhart et al., 1986; Nebeker & Hodges, 1983; Nowak et al., 2015; Showalter & Turchin, 1993). With the exception of relatively small-scale applications, these silvicultural treatments have not been widely implemented in pitch pine-dominated communities in the north-eastern United States (Dodds et al., 2018). This is attributed to many obstacles, including the high cost of thinning operations stemming from an absence of local markets and the low value of harvested materials relative to south-eastern pine systems (Dodds et al., 2018), the lack of pitch pine-specific stocking guides and other management tools, and public resistance to management in a rapidly expanding wildlife–urban interface (Blanchard & Ryan, 2007; Radeloff et al., 2005; Ryan, 2012). Together, these obstacles, the looming threat of SPB, and the disturbance requirements of pine barrens ecosystems make it important for management decisions to be ecologically and economically effective.

Hazard rating is a powerful tool for understanding the relationships between pest activity and forest conditions. Based on factors that predispose stands to pest infestation, its purpose is not to predict when or if damage will occur, but to identify conditions where infestations are most likely to occur and areas where damage (e.g., tree mortality) is expected to be greatest (Mason et al., 1985). Hazard rating models thus provide land managers with information useful in identifying areas that may require preventative management, increased surveillance, accelerated suppression action, or post-damage appraisal (Hicks et al., 1987). Hazard models have successfully been applied in the south-eastern United States to determine stand-level SPB susceptibility using various predictors based on stand and site conditions, including host species abundance, site quality, age structure, density, landform, and SPB abundance (Billings & Upton, 2010; Dodds et al., 2018; Hicks et al., 1980, 1987; Mason et al., 1985). As part of the National Insect and Disease Risk Map (NIDRM) effort in 2012, a GIS-based multi-criteria/weighted modelling framework was utilized to classify SPB hazard (based on weighted inputs of pine basal area, quadratic mean diameter of pines, stem density index, and history of past SPB outbreaks) at 240-meter resolution across all lands/ownerships in the south-eastern United States (Krist Jr. et al., 2014). The results were subsequently ‘rolled up’ to classify SPB hazard at the county scale across the south-eastern United States, for use by federal and state partners in targeting prevention and surveillance activities (https://www.fs.fed.us/foresthealth/applied-sciences/mapping-reporting/spb-hazard-rating-maps.shtml). Due to the comparatively small and isolated distribution of north-eastern pine-dominated forests and the unique species composition, SPB hazard models developed for south-eastern forests have limited applicability to the north-east (Dodds et al., 2018). Even so, one preliminary hazard rating model was successfully used to help prioritize at-risk areas in state-owned pitch pine stands on Long Island, New York (NY) for thinning and suppression (Dodds et al., 2018). Expansion of this work to a more comprehensive model developed specifically for pitch pine forests would be an important component of adaption to SPB in the northeast (Dodds et al., 2018).

We aimed to expand hazard rating capabilities to inform adaptation strategies to this novel pest dynamic across a broader landscape. We developed a regionally-calibrated hazard rating model that uses (1) site characteristics, (2) stand conditions, and (3) previous SPB activity to predict stand-level susceptibility of north-eastern pitch pine-dominated communities to SPB. This tool can be applied to reduce landscape-scale vulnerability to SPB by supporting the identification and prioritization of highly susceptible stands for prevention management.

中文翻译：

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为适应性森林管理提供信息：松树贫瘠地区南方松甲虫 Dendroctonus frontalis 的危害评估工具

介绍

Insect pests are globally important drivers of forest landscape dynamics due to their impact on key forest components, including vegetation structure and composition, water and nutrient cycling, and wildlife habitat (Adams et al., 2009; Boon, 2012; Dale et al., 2001; Hicke et al., 2012; Mcshea et al., 2007; Veblen et al., 1991). Given the importance of climate to the physiological and ecological determinants of pest distribution and dynamics, climate change is indirectly affecting forests by altering the range, frequency, or severity of pest outbreaks (Ayres & Lombardero, 2000; Deutsch et al., 2008; Dukes et al., 2009; Jactel et al., 2019; Logan et al., 2003; Pureswaran et al., 2018). Such climate change-induced alterations to historic disturbance regimes can present novel ecological effects and management challenges.

As temperatures rise, there are a growing number of examples of phytophagous insect populations expanding their ranges (Carroll et al., 2003; Dale et al., 2001; Jepsen et al., 2008; Niemelä et al., 2001; Parmesan, 2006; Pureswaran et al., 2018). One of the most well-understood examples has occurred among bark beetles (Coleoptera: Curculionidae: Scolytinae) in North America. Southern pine beetle [Dendroctonus frontalis Zimmermann (SPB)] is a bark beetle whose wide-scale ecologic, economic, and social impacts have deemed it one of most destructive pests of pine forests (Clarke & Nowak, 2009; Coulson & Klepzig, 2011; Dodds et al., 2018; Payne, 1980; Price et al., 2006). Despite its short generation time, high dispersal capabilities, and wide host distribution, SPB's lower lethal air temperature (−16°C) has historically limited it to the south-eastern United States, Mexico, and Central America, with northern populations reaching Ohio, Pennsylvania, and Maryland (Payne, 1980; Price et al., 2006; Ungerer et al., 1999). However, warming minimum winter air temperatures in the last two decades have enhanced beetle fitness at northern distributions and allowed for damaging populations to expand (Lesk et al., 2017; Ungerer et al., 1999; Weed et al., 2013 年）。

SPB 的持续向北扩张威胁着以潜在宿主物种为主的生态系统，这些物种在历史上对甲虫的接触有限，包括全球罕见的东北松林 (Lesk et al.,  2017 ; Tran et al.,  2007 ; Ungerer et al., 2017)。 ，  1999 年；威廉姆斯和利布霍尔德，  2002 年）。在受 SPB 侵染的松树贫瘠地区，树冠松树（ Pinus rida Mill.）的高死亡率正在加速开放树冠、依赖火的松树贫瘠地区向以橡树（栎属）等嗜热性较低的物种为主的森林的持续过渡、红枫 ( Acer rubrum L.) 和白松 ( Pinus strobus L.;(Heuss 等人， 2019 年；霍华德等人，  2011 年；诺瓦基和艾布拉姆斯，  2008 年）。到 2050 年，由于适合 SPB 的气候预计将覆盖 78% 的松树林，SPB 的损害可能会扩展到更多的北部松树贫瘠地区（Lesk 等人，  2017 年）。

SPB 种群遵循脉冲喷发周期，其中有利的环境条件导致不规则的爆炸性种群增长和大部分宿主物种的死亡（Berryman，  1986 年）。在这些爆发期间，SPB 之间的信息化学通讯组织了大规模攻击，这些攻击可以压倒健康树木的树脂防御系统，并在几天到几周内导致宿主死亡（Hain 等人，  2011；Hassett 等人，  2017；Sullivan，  2011） . 美国东南部的 SPB 侵染发生率已通过应用森林管理处理措施（例如林分疏伐和规定的焚烧）减少了一些林分，这些措施可促进林分活力并破坏 SPB 信息素通讯（Brown 等人， 1987 ; Burkhart 等人，  1986 年；内贝克和霍奇斯，  1983 年；诺瓦克等人，  2015 年；Showalter 和 Turchin，  1993 年）。除了相对小规模的应用外，这些造林处理尚未在美国东北部以松树为主的社区广泛实施（Dodds 等人，  2018 年）。这归因于许多障碍，包括由于缺乏当地市场而导致的间伐作业成本高，以及相对于东南松树系统而言，收获材料的价值较低（Dodds 等人，  2018 年）)、缺乏针对松树的放养指南和其他管理工具，以及在快速扩张的野生动物与城市界面中公众对管理的抵制（Blanchard & Ryan,  2007 ; Radeloff et al.,  2005 ; Ryan,  2012）。总之，这些障碍、SPB 迫在眉睫的威胁以及松树贫瘠生态系统的干扰要求使得管理决策在生态和经济上有效变得很重要。

危害等级是了解害虫活动与森林状况之间关系的有力工具。基于易受害虫侵扰的因素，其目的不是预测损害何时或是否会发生，而是确定最有可能发生侵扰的条件以及预计损害（例如树木死亡率）最大的区域（梅森等人，  1985 年）。因此，危害评级模型为土地管理者提供了有用的信息，可用于确定可能需要预防性管理、加强监督、加速抑制行动或损害后评估的区域（Hicks 等，  1987）。危害模型已成功应用于美国东南部，使用基于林分和场地条件的各种预测因子确定林分水平的 SPB 易感性，包括宿主物种丰度、场地质量、年龄结构、密度、地形和 SPB 丰度（Billings & Upton，  2010 年；Dodds 等人，  2018 年；Hicks 等人，  1980 年，1987 年；Mason 等人，  1985 年）。作为 2012 年国家昆虫和疾病风险地图 (NIDRM) 工作的一部分，使用基于 GIS 的多标准/加权建模框架对 SPB 危害进行分类（基于松树基面积的加权输入、松树的二次平均直径、美国东南部所有土地/所有权的 240 米分辨率下的茎密度指数和过去 SPB 爆发的历史（Krist Jr. et al.,  2014）。随后将结果“汇总”以在美国东南部的县级范围内对 SPB 危害进行分类，供联邦和州合作伙伴用于针对预防和监测活动（https://www.fs.fed.us/ Foresthealth/applied-sciences/mapping-reporting/spb-hazard-rating-maps.shtml）。由于东北部以松树为主的森林分布相对较小且孤立，且物种组成独特，针对东南部森林开发的 SPB 危害模型对东北部的适用性有限（Dodds et al.,  2018）。即便如此，一种初步的危害评级模型已成功用于帮助优先考虑纽约长岛（NY）国有松树林中的风险区域，以进行疏伐和抑制（Dodds et al.,  2018）。将这项工作扩展到专门为松林开发的更全面的模型将是适应东北地区 SPB 的重要组成部分（Dodds 等人，  2018 年）。

我们的目标是扩大危害评级能力，以便在更广泛的环境中为这种新型害虫动态提供适应策略。我们开发了一个区域校准的危害评级模型，该模型使用 (1) 场地特征、(2) 林分条件和 (3) 先前的 SPB 活动来预测东北松树为主的社区对 SPB 的林分水平敏感性。该工具可用于通过支持识别和优先确定高度易感的林分以进行预防管理，从而减少景观规模对 SPB 的脆弱性。