Natalie L. Cleavitt

Verified

Natalie verified their affiliation via an institutional email.

Learn more

Verified

Natalie verified their affiliation via an institutional email.

Learn more

• PhD, University of Alberta, 2001
• Sr. Research Associate at Cornell University

Mast seeding, the synchronous and highly variable production of seed crops by perennial plants, is a population‐level phenomenon and has cascading effects in ecosystems. Mast seeding studies are typically conducted at the population/species level. Much less is known about synchrony in mast seeding between species because the necessary long‐term dat...

Plants display a range of temporal patterns of inter‐annual reproduction, from relatively constant seed production to “mast seeding,” the synchronized and highly variable interannual seed production of plants within a population. Previous efforts have compiled global records of seed production in long‐lived plants to gain insight into seed producti...

Global change has created less stable forest systems and given urgency to understanding limitations to the establishment of tree seedlings beyond current range boundaries. We quantified trends in 13 years of annual northern red oak (QURU) seedling survival data for 1733 marked individuals at a local species distribution boundary within the northern...

Aim Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whethe...

Upslope shifts in plant distributions are often attributed to warming climate and lengthening of the growing season; however, biotic interactions may also contribute. The impacts of pests and pathogens are often sensitive to climate change and can vary along the climatic gradient associated with elevation. American beech (Fagus grandifolia) has mov...

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundat...

Leaf abundance of trees plays a dominant role in energy, water and nutrient flux of forest ecosystems, in defining the habitat structure of entrained biota and in mediating interspecific competition among tree species. We quantified leaf abundance of three dominant tree species (Acer saccharum Marsh.; Fagus grandifolia Ehrh.; Betula alleghaniensis...

Significance Suitable habitats for forest trees may be shifting fast with recent climate change. Studies tracking the shift in suitable habitat for forests have been inconclusive, in part because responses in tree fecundity and seedling establishment can diverge. Analysis of both components at a continental scale reveals a poleward migration of nor...

Orchids (Orchidaceae) are a family of flowering plants with a high proportion of threatened taxa making them an important focus of plant conservation. Orchid conservation efforts are most effective when informed by reliable demographic research. We utilized transition matrix models to examine the population dynamics and demography within sympatric...

The complex effects of global environmental changes on ecosystems result from the interaction of multiple stressors, their direct impacts on species and their indirect impacts on species interactions. Air pollution (and resulting depletion of soil base cations) and biotic invasion (e.g. beech bark disease [BBD] complex) are two stressors that are a...

Ecosystems are changing in complex and unpredictable ways, and analysis of these changes is facilitated by coordinated, long‐term research. Meeting diverse societal needs requires an understanding of what populations and communities will be dominant in 20, 50, and 100 yr. This paper is a product of a synthesis effort of the U.S. National Science Fo...

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here...

Sugar maple decline in eastern North America is caused by a complex combination of factors, with soil nutrition being one of several important determinants. Given the complexity of sugar maple population dynamics and the geographic extent of the species, we support Bailey et al.’s (2019, Can. J. For. Res. 49(7), doi:10.1139/cjfr-2018-0207) argument...

The integrated forest ecosystem model ForSAFE-Veg was used to simulate soil processes and understory vegetation composition at three—sugar maple, beech, yellow birch—hardwood forest sites in the Northeastern United States (one at Hubbard Brook, NH, and two at Bear Brook, ME). Input data were pooled from a variety of sources and proved coherent and...

We quantified damage by a microburst windstorm to a northern hardwood forest (Hubbard Brook Experimental Forest, New Hampshire). These storms may be important in regulating the structure and composition of forests of the northeastern United States, but few studies of damage patterns from microbursts have been reported. In the 600 ha area most heavi...

Forest harvesting can impact site quality by removing essential nutrients, exacerbating the effects of historic base cation losses associated with acid deposition. We studied the 30-year trajectory of forest recovery from clearcutting (whole-tree harvest (WTH)) in a forest originally dominated by sugar maple (Acer saccharum Marsh.). At both the wat...

Mast seeding is the synchronous production of large seed crops in plant populations and for many tree species is known to be determined by the interaction between weather cues and internal plant resources. We use a 24-year record of seedfall for sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.) across a northern hardw...

Terrestrial orchids are especially susceptible to population declines, and hence are the focus of plant conservation efforts worldwide, but the life history and demography of heterotrophic orchids is not well understood. Our objective was to quantify life stage transition rates for a species pair of rare round-leaved orchids (Platanthera spp.) in a...

Atmospheric deposition of sulfur (S) and nitrogen (N) has decreased steadily in the northeastern U.S. since the federal 1970 Clean Air Act was passed, yet deposition remains elevated above natural background levels throughout the region. Epiphytic macrolichens are highly sensitive to air pollution and their status is a good indicator of ecological...

The regeneration ecology of sugar maple (Acer saccharum Marsh.) has been impacted by acid rain leaching of base cations from the soils throughout much of its range. We tracked the survival and causes of death for a natural cohort of sugar maple seedlings across 22 sites in the Hubbard Brook Valley in New Hampshire, USA, where soil acidification has...

We examined plot-level interactions among nitrogen and sulfur deposition, tree type, and epiphytic diversity, biomass, and abundance in Acadia National Park (ACAD), Maine, that receives pollutant deposition and is of particular concern for biological conservation. Spruce appeared to acidify incoming deposition resulting in more concentrated inputs...

Alkaline cupric oxide oxidation and proximate analysis were used to investigate the sources and diagenetic state of organic matter in six Sphagnum-dominated peatlands located between Alberta, Canada, and Ohio, U.S.A. Cupric oxide oxidation was also used to characterize vascular and nonvascular wetland plant species to provide a specific biological...

The possible regeneration failure of sugar maple (Acer saccharum Marsh.) as part of their decline has been not well explored using field studies. We sought to clarify the roles of maternal effects and dynamics of early-season survival in contributing to the previously documented pattern of larger seedlings and higher seedling densities on a Ca-trea...

Increases in soil freezing associated with decreases in snow cover have been identified as a significant disturbance to nitrogen (N) cycling in northern hardwood forests. We created a range of soil freezing intensity through snow manipulation experiments along an elevation gradient at the Hubbard Brook Experimental Forest (HBEF) in the White Mounta...

To better understand associations between epiphytes and old forests, lichens and bryophytes that grow on tree bark were quantified in relatively undisturbed stands of Acadia National Park (ACAD). Four plots were dominated by hardwoods and eight by spruce. To obtain data from upper boles, we climbed four maple trees per plot (eight plots) and four s...

Bryophytes are often noted for their growth on specific rock types and their value as indicator species. However, some evidence suggests that restriction of a species to specific rock types may be less rigid and could vary under different environmental conditions. We assessed richness and distribution patterns of bryophytes at 22 rock outcrop locat...

Dominant patterns and processes in rare bryophyte ecology are presented within the framework of current rarity theory. Available evidence suggests that bryophyte conservation should primarily consider the importance of establishment and habitat requirements for rare species. Preservation of rare and high quality habitats is essential. Future unders...

Substrate specificity has been pinpointed as key to understanding plant species distributions and to differentiating types of plant rarity. Substrate specific distribution patterns (e.g., calcicole and calcifuge) are particularly prevalent among bryophytes. Many authors have suggested that the effects of substrate chemistry might be most important...

Desiccation-tolerance (DT), the ability to lose virtually all free intracellular water and then recover normal function upon rehydration, is one of the most remarkable features of bryophytes. The physiology of bryophytes differs in major respects from that of vascular plants by virtue of their smaller size; unlike vascular plants, the leafy shoots...

Bryophyte growth is most often cited as being primarily water-limited; however, experimental manipulation of water availability in the field has not previously been employed to test this hypothesis. Here we follow the growth responses of a leafy liverwort, Bazzania trilobata, to field water addition treatments. Our study system was an eastern hemlo...

The understory conditions of eastern hemlock stands in the Delaware Water Gap National Recreation Area have been altered by canopy decline caused by an exotic insect pest, the hemlock woolly adelgid. We consider the response of bryophytes to these changes, particularly increased availability of understory light and coarse woody debris (CWD). Pre-ad...

Despite the recognized importance of root sprout production in northern populations of American beech (Fagus grandifolia Ehrh.), further consideration of the relative role of regeneration from seed in this species appears warranted and timely. A careful examination of the literature revealed that seed- and sprouts-origin individuals co-occurred wit...

Forest canopies are often stratified by species little is known about the depth distribution of tree roots in mixed stands because they are not readily identified by species. We used diagnostic characteristics of wood anatomy and gross morphology to distinguish roots by species and applied these methods to test for differences in the rooting depth...

Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither abovegrou...

We reduced early winter snowpack in four experimental plots at the Hubbard Brook Experimental Forest in New Hamphire for 2 years to examine the mechanisms of root injury associated with soil freezing. Three lines of evidence suggested that direct cellular damage, rather than physical damage associated with frost heaving, was the principal mechanism...

Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carriere) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area....

Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca...

Factors that set the altitudinal limits of plants have been relatively well explored for many land plant groups, but not for bryophytes. Bryophytes typically represent a significant portion of alpine floras with many species specific to highland systems. Differences between highland and lowland bryophytes have been underinvestigated. In the present...

Mnium arizonicum is a moss endemic to North America and in the northern Rocky Mountains it occurs most abundantly in the understory of subalpine tree islands formed by Abies lasiocarpa and Picea engelmannii. This species reproduces almost entirely through apical fragment regeneration and its expansion into lower elevation sites may be dispersal lim...

Species rarity in mosses may be linked to narrow physiological tolerance and habitat specificity of established colonies and gametophyte fragments (i.e. fragments of stem apices). Stress tolerance and habitat light and moisture were compared for three rare and three common moss species. Observed habitat specificity was more likely to correspond to...

The rare moss, Didymodon johansenii, occurs only on substrata with a fine layer of calcareous silt. In Alberta, these substrata are mainly logs and tree bases. Such substratum specificity patterns may relate to species interactions with the substratum itself, with other species, or a combination. Direct species–substratum interactions are most cruc...

Forty-three species and two subspecies of Sphagnum are reported for New Hampshire, including fifteen species and one subspecies documented from herbarium records and recent collections. Diversity at county and biophysical subsection (ecoregion) levels is presented and areas that remain undercollected in the state are highlighted. New Hampshire has...

Alkaline cupric oxide oxidation and proximate analysis were used to investigate the sources and diagenetic state of organic matter in six Sphagnum-dominated peatlands located between Alberta, Canada, and Ohio, U.S.A. Cupric oxide oxidation was also used to characterize vascular and nonvascular wetland plant species to provide a specific biological...

Thesis (Ph. D.)--University of Alberta, 2002. Includes bibliographical references.