Winter is an understudied but key period for the socioecological systems of northeastern North American forests. A growing awareness of the importance of the winter season to forest ecosystems and surrounding communities has inspired several decades of research, both across the northern forest and at other mid- and high-latitude ecosystems around the globe. Despite these efforts, we lack a synthetic understanding of how winter climate change may impact hydrological and biogeochemical processes and the social and economic activities they support. Here, we take advantage of 100 years of meteorological observations across the northern forest region of the northeastern United States and eastern Canada to develop a suite of indicators that enable a cross-cutting understanding of (1) how winter temperatures and snow cover have been changing and (2) how these shifts may impact both ecosystems and surrounding human communities. We show that cold and snow covered conditions have generally decreased over the past 100 years. These trends suggest positive outcomes for tree health as related to reduced fine root mortality and nutrient loss associated with winter frost but negative outcomes as related to the northward advancement and proliferation of forest insect pests. In addition to effects on vegetation, reductions in cold temperatures and snow cover are likely to have negative impacts on the ecology of the northern forest through impacts on water, soils, and wildlife. The overall loss of coldness and snow cover may also have negative consequences for logging and forest products, vector-borne diseases, and human health, recreation, and tourism, and cultural practices, which together represent important social and economic dimensions for the northern forest region. These findings advance our understanding of how our changing winters may transform the socioecological system of a region that has been defined by the contrasting rhythm of the seasons. Our research also identifies a trajectory of change that informs our expectations for the future as the climate continues to warm.

Spatial pattern in the distribution and abundance of organisms is an emergent property of collective rates of reproduction, survival and movement of individuals in a heterogeneous environment. The form, intensity and scale of spatial patterning can be used to test hypotheses regarding the relative importance of candidate processes to population dynamics. Using 84 plots across eastern North America, we studied populations of two associated plant parasites, the invasive felted beech scale Cryptococcus fagisuga Lind. and the native Neonectria fungi, which together cause beech bark disease (BBD). We evaluated spatial patterns at the scales of trees within stands, stands within the forest and forests within the landscape to examine four hypothetically important factors in the ecology of the disease: (i) local contagion within stands; (ii) regional contagion, or among patch infection–reinfection dynamics; (iii) variation in host susceptibility linked to genetic and/or environmental heterogeneity; and (iv) climate effects on population growth of BBD organisms. Analyses revealed an unexpected lack of spatial aggregation in BBD populations among trees, stands and forests. This implies that propagule pressure is generally sufficiently high throughout the infested region of North America such that neither trees nor stands are spared from the disease by dispersal limitations of the disease agents. Furthermore, variation in tree and stand level susceptibility has minimal impact on BBD dynamics and climate is not a conspicuous driver of abundance within the core range of BBD.

Biotic threats to trees often arise from interactions among two or more species, frequently insects and fungi, that function together to defeat host defenses, secure resources and colonize new hosts. Feedbacks among plant enemies can have large effects on host population and disease dynamics, either by promoting stabilizing negative feedbacks or contributing to positive feedbacks that can destabilize populations and permit outbreaks. Feedbacks can be rapid and direct (e.g. within trees or among years) or can arise from slowly developing changes in host resource quantity or quality at the scale of forest stands or landscapes. Climate may also influence system dynamics by altering feedbacks within or among species or through density independent effects. We evaluated major drivers of population dynamics of beech bark disease (BBD), an important forest disease in eastern deciduous forests of North America, using data from 28 study sites in the eastern United States monitored for up to 14 yr between 1979 and 1992. Both primary causal agents of BBD – the introduced felted beech scale Cryptococcus fagisuga and native fungi Neonectria spp. – showed strong simple density dependence in all study populations. Surprisingly, densities of scale insects and fungi had little or no effects on population growth rates of the other, despite their habit of living in close physical relationships. For both insects and fungi, ecologically important features of the density dependent functions (slope, carrying capacity and density independent variance) were variable across sites. Climatic effects on density‐dependent functions (and scatter around them) were evident but generally weak and variable. The most striking predictor of patterns in density dependence was duration since establishment of BBD in the region. Apparently BBD alters forests over decades in ways that strengthen self‐regulation among causal agents without eliminating or even dramatically reducing host populations.

Summary 1. Introduced pests and pathogens are a major source of disturbance to ecosystems world‐wide. The famous examples have produced dramatic reductions in host abundance, including virtual extirpation, but most introductions have more subtle impacts that are hard to quantify but are potentially at least as important due to the pathogens’ effects on host reproduction, competitive ability and stress tolerance. A general outcome could be reduced host abundance with concomitant increases in the abundance of competitors. 2. Beech bark disease (BBD) is a widespread, fatal affliction of American beech ( Fagus grandifolia ), currently present in c. 50% of beech’s distribution in eastern North America. Despite high adult mortality, beech remains a dominant component of the forest community. 3. Employing spatially extensive data from the national Forest Inventory and Analysis program of the United States Forest Service, we show that forests have changed dramatically in the presence of BBD. Within the 2.3 million km 2 range of beech, size‐specific mortality was 65% higher in the longest‐infected regions, and large beech (>90 cm diameter at breast height) have declined from c. 79 individuals km −2 to being virtually absent. Small stem beech density was dramatically higher (>350%) such that infested forests contain a roughly equivalent cross‐sectional (basal) area of beech as before BBD. 4. There was no evidence for compensation by sugar maple or other co‐occurring tree species via increased recruitment or adult survivorship at the landscape scale. Overall, community composition remained roughly unchanged as a result of BBD. 5. Surprisingly, trajectory of stand dynamics (shifts in stem density and mean tree size reflecting normal stand maturation (self‐thinning) or retrogression (more abundant, smaller trees over time)) did not differ between affected and unaffected regions. Variance in stand dynamics was greater in afflicted forests, however, indicating that predictability of forest structure has been diminished by BBD. 6. Synthesis. Forests of eastern North America have shifted to increased density and dramatically smaller stature – without notable change in tree species composition – following the invasion of a novel forest disease. Our results reinforce the conclusion that introduced diseases alter fundamental properties of ecosystems, but indicate that the spectrum of potential effects is broader than generally appreciated.

In recent years the Forest Service has reemphasized the need for increased environmental literacy among the Nation's citizens and has recognized the benefits of addressing that need among school-age children. This publication is a product of an Adirondack Curriculum Project workshop sponsored by the USDA Forest Service, Northeastern Research Station, and Paul Smith's College. The workshop was held at Great Camp Sagamore in Raquette Lake, NY, in June 2005. Great Camp Sagamore is operated by the Sagamore Institute, which is dedicated to the stewardship of the camp and to its use for educational and interpretive purposes. For 2 days, 22 teachers met with resource professionals with expertise in either the Northern Forest or in teaching methods and techniques, or both, and developed the lesson plans in this publication.

of mean diameter and stem density at the first measured cycle, limiting our dataset to all plots containing >1% beech basal area that were sampled two or more times in the past 25 years. We used the regression line estimate for the 95th quantile as the thinning curve boundary (slope = -0.33 ± 0.04; Cade and Guo 2000, Cade and Noon 2003, The spread of beech bark disease (BBD) through eastern North America has had a strong impact on the structure and function of the forest ecosystem, beginning some time after the introduction of the beech scale, Cryptococcus fagisuga Lind. (Homoptera:Eriococcidae), in 1890. Stands infected by beech scale and by one or more associated species of the ascomycete genus

Relatively few models have been developed to predict changes in forest structure as a result of BBD. A lack of understanding of the critical factors that control the severity of the disease in forests, and at what spatial scale these factors act, continues to limit our ability to predict changes in forest structure and composition following the establishment of BBD. However, historical data sets combined with new measurements across a spectrum of northeastern forest stands may allow us to model the characteristics of uninfected forests that put them at risk of a significant state change of descending into the undesirable condition that has been characterized as 'beech hell'. We propose to test for hypothesized drivers of this state change by combining measurements of forest structure and dynamics with historical patterns of abundance in the scale insects and fungus that cause BBD. Forest management could benefit from models that identify (1) stands that are at risk of undesirable state change, and (2) key factors that drive the transition. Models may suggest strategies for directing the transition toward more desirable outcomes in aftermath forests. In particular, we hope that empirically based models can be developed to predict the location and attributes of forests that will retain beechnut production in the presence of BBD.

In a preliminary study of beech bark disease in the 'aftermath' forests of northern Adirondack watersheds, we collected data on disease status in relation to tree diameter and the relationship between soil moisture and bark thickness in 11 plots across 6 northern Adirondack watersheds. Sixty-two percent of trees sampled were <= 13 cm in diameter and no trees over 29.4 cm were recorded, even though at least two watersheds sampled are considered old growth. As predicted, larger trees were more diseased than smaller trees and the percent dead also increased dramatically with size class. We noted that some number of trees <= 10 cm had unexpectedly high disease ratings suggesting the need in future studies to collect data on smaller diameter trees so as to be able to predict how the disease will impact the large number of trees coming up in these size classes. Trees grown in plots that had medium soil moisture (as opposed to low) had significantly thicker bark, regardless of diameter, but this had no effect on disease status of trees.

O NE goal of science education reforms has been to improve approaches to learning that not only teach specific concepts but provide students with life-long problem solving skills (AAAS 1989; NRC 1996). Attaining this goal involves having students who are active participants in project-based classroom activities (Krajicik et al. 1994), rather than passive recipients of teacher disseminated knowledge. When students are provided a realistic context within which to solve problems and construct knowledge, learning is enhanced (Abrams 1998; Mullis & Jenkins 1988). Student/Scientist Partnerships (SSPs) are a type of project-based instruction, wherein students are active participants in a scientific research collaboration between students, teachers and research scientists (Barstow 1997; Tinker 1997; Lawless & Rock 1998). SSPs provide context-rich, integrated, hands-on approaches to teaching the scientific enterprise as well as subject-specific content to K-12 students (Barstow 1997; Tinker 1997). They also provide the potential for scientific data collection from a broad geographical range that would not be feasible without such partnerships (Berkowitz 1997). To optimize the outcomes of both of these objectives, critical program components must be in place and the trade-offs between educational activities and accurate data collection for research must be clearly delineated. In this article, we draw on our experience with an established SSP, the Forest Watch (FW) program, to describe several critical components of these partnerships. We hope this guide will be useful for interested teachers considering participation in an SSP. We also present the trade-offs between educational and scientific objectives that must be made explicit by SSP administrators so that these partnerships can be successful from the point-of-view of both educators and scientists. This information is derived from several years of classroom observations, individual discussions with teachers and students, interviews with program scientists, responses to teacher surveys, and feedback from participating teachers at a recent FW workshop. Throughout the article we use examples from the FW program to support and clarify some of the points we make. An overview of the program will help readers put the upcoming examples in context. The program, initiated in 1992, involves students from more than 100 schools across New England collecting annual data on the growth and health of five permanently tagged white pine trees in marked study plots near their schools. White pine is considered to be a bioindicator species because it is more sensitive to ozone exposure than some other tree species (Treshow 1986; Treshow & Anderson 1991; Theisen et al. 1994). Forest Watch scientists are testing the hypothesis that tropospheric ozone concentrations correlate with white pine needle damage and, eventually, growth. Students describe their forest site, make tree measurements, collect needle samples to analyze in the lab, and send to the University of New Hampshire (UNH) for spectral analysis. In the classroom, students measure needle retention and needle length, and quantify needle damage, looking specifically for symptoms of ozone pollution. Forest Watch materials also include protocols for making and examining needle-thin sections and doing an acetone-based chlorophyll extraction. Each year UNH compiles a data book containing all schools' measurements, UNH measured spectra, and some analysis of data using student measures from all over New England.

We grew seedlings of two co-occurring high elevation tree species in controlled light and nitrogen (N) environments to examine the effect on foliar N and P concentrations and the resulting correlation with photosynthesis and growth. Foliar N concentrations in both heart-leaf paper birch (Betula cordifolia) and balsam fir (Abies balsamea) seedlings were greater in low light treatments than in high light treatments. P concentrations, however, were lower in birch and fir foliage grown in low light than in high light. N-availability had no effect on foliar N in birch but tended to increase N concentration in fir needles at all but 100% ambient light. N-availability had no effect on P concentration in fir seedlings, but high N decreased foliar P in birch. There was a positive relationship between foliar N-concentration (mg g−1) and mass-based maximum photosynthetic rate (Asat) in birch seedlings and a corresponding growth response to increased N-availability (suggesting N-limitation). Fir photosynthesis exhibited a positive correlation up to 22 mg g−1 – N and a negative correlation above that point, suggesting that high N concentrations may be detrimental to photosynthesis in the fir seedlings. There was no significant effect of N-treatment on growth.

We examined net nitrogen mineralization rates in forest floor beneath birch-dominated or fir-dominated canopy plots in a high-elevation mixed-species forest in New Hampshire during the 1995 and 1996 growing seasons. Soil moisture was significantly greater in 1996 than in 1995 (season averages were 2.1 times and 1.4 times dry soil mass, respectively). Net mineralization was significantly greater in both plot types in 1996 than in 1995. The magnitude of difference, however, was much greater in fir plots. Nitrification increased in birch plots and significantly decreased in fir plots from 1995 to 1996. Results of a three-way ANOVA showed significant year and species main effects for net mineralization and a significant species × year interaction for nitrification. There were no significant correlations between net N mineralization and measured soil chemistry variables in 1995. In 1996 there were significant positive correlations between total N, and net mineralization and nitrification in birch plots and between soil moisture and net mineralization in fir plots. These results support a growing body of research suggesting that species feedbacks influence rates of net N mineralization in mixed species forests. Further, this study provides novel evidence that rates of net N mineralization may respond differently to changing abiotic conditions depending on the local canopy species in a mixed-species forest.

Mercury deposition was monitored at two mountain sites in Quebec using transplanted lichens and moss. The terricolous lichen species Cladina rangiferina, the epiphytic lichen species Hypogymnia physodes, and the feather moss Pleurozium schreberi were transplanted from a northern Ontario boreal site to the bases and summits of Roundtop Mountain and Mt. Tremblant in southern Quebec. After 12 months, transplants of C. rangiferina sited at the base and summit of Roundtop mountain and the summit of Mt. Tremblant showed a significant increase in mercury concentration over controls (p < 0.05). The largest difference occurred at the summit of Roundtop mountain where mercury concentration was 81.4 ± 10.9 ppb as compared to 45.6 + 10.6 ppb at the control site. No significant increases in mercury concentration in P. schreberi were seen after 12 months at any site althought trends of increase were apparent. After 20 months, further significant increases in Hg content were observed in both the terricolous lichen and the feather moss at both the Roundtop Mountain base and summit sites. A significant increase in Hg content of P. schreberi was also noted at the Mt. Tremblant summit site. Over the length of the study the greatest mercury concentration increases were observed in the feather moss at the Roundtop Mountain summit site (with a 248.3 ± 30.0 ppb mercury concentration as compared to 108.3 ± 30.0 ppb in controls). No significant change in mercury concentration in the epiphyte H. physodes was found during the study. These data indicate that mercury deposition is occurring, especially to higher elevation sites. While mercury inputs at the summits may be increased by the effects of fog, increases in mercury at the base sites cannot be accounted for the same way, but may represent the importance of dry deposition processes.

Biotic threats to tree growth, survival, or reproduction often arise from interactions among a suite of species, primarily insects and fungi, that function together to varying degrees to defeat host defenses, secure resources, and infect new hosts. Where two or more organisms interact, there is strong potential for positive or negative feedbacks that can have large effects on host population and disease dynamics.