David F. Greene's research while affiliated with Humboldt State University and other places
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Publications (89)
The reproductive ecology of the semi-serotinous species black spruce (Picea mariana (Mill.) BSP) in northern boreal forests remains poorly understood. There is a general lack of data on cone / seed production and viability as a function of biotic tree-level characteristics and abiotic variables. No studies currently exist to quantify these differen...
Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a dataset that collates reproductive time-series d...
Our overall objective is to synthesize mast-seeding data on North American Pinaceae to detect characteristic features of reproduction (i.e. development cycle length, serotiny, dispersal agents), and test for patterns in temporal variation based on weather variables. We use a large dataset ( n = 286 time series; mean length = 18.9 years) on crop siz...
Significance
Black spruce is the dominant tree species in boreal North America and has shaped forest flammability, carbon storage, and other landscape processes over the last several thousand years. However, climate warming and increases in wildfire activity may be undermining its ability to maintain dominance, shifting forests toward alternative f...
Understanding the dinamics of filtration of pollen and spores by plant canopies is crucial to the in the modelling of their dispersal, yet few studies have quantified filtration. Here, we examine the decline in the density of flour particles descending through a 40 m-tall tropical canopy on a windless day at Caxiuanã National Forest, Pará, Brazil....
Literature dating back to the early 20th century reveals a long-standing interest in the effects of freezing precipitation on forests. Early scientific studies of significant icing events were descriptive in nature, but through time, researchers have worked toward developing a better understanding of how loads interact with tree and forest characte...
Resource pulses are rare events with a short duration and high magnitude that drive the dynamics of both plant and animal populations and communities¹. Mast seeding is perhaps the most common type of resource pulse that occurs in terrestrial ecosystems², is characterized by the synchronous and highly variable production of seed crops by a populatio...
It has recently become clear that the regeneration density of serotinous species within a burned area declines with
local fire intensity. It is assumed that this occurs because variation in local fire intensity leads to variation in incident heat fluxes
and, ultimately, seed necrosis. We argue here that this same relationship between incident heat...
Early successional competition among boreal forest tree and shrub species and its effects on growth of commercial tree species have been a major source of uncertainty in establishing efficient precommercial thinning and brushing prescriptions. We examined the effect of prethinning competitor density, postthinning
competitor regrowth density, prethi...
We present a landscape-level operational natural regeneration assessment tool, created by linking a validated forest regeneration model with forest inventory maps. Using basal areas obtained from temporary plots and seedbed distributions from field data, seedling densities are simulated for pure Picea mariana (Mill.) and Pinus banksiana (Lamb.) sta...
Background and aims:
Despite a longstanding interest in variation in tree species vulnerability to ice storm damage, quantitative analyses of the influence of crown structure on within-crown variation in ice accretion are rare. In particular, the effect of prior interception by higher branches on lower branch accumulation remains unstudied. The ai...
A tool was developed to allow managers and foresters to quickly assess reforestation needs following forest fire and salvage logging at the stand level in both pure and mixed black spruce and jack pine stands. This on-site operational assessment tool was created using a forest regeneration model that simulates the natural regeneration densities of...
Disturbance plays an important role in the distributional range of species by affecting their colonization potential and persistence. Short disturbance intervals have been linked to reduced seedbank sizes of some species, but the effects of long intervals are largely unknown. To explore the potential existence of seedbank sizes that may also be lim...
In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind-stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical...
Trees which lack obvious fire-adaptive traits such as serotinous seed-bearing structures or vegetative resprouting are assumed to be at a dramatic disadvantage in recolonization via sexual recruitment after fire, because seed dispersal is invariably quite constrained. We propose an alternative strategy in masting tree species with woody cones or co...
Abstract: Understanding the dinamics of filtration of pollen and spores by plant canopies is crucial to the in the modelling of their
dispersal, yet few studies have quantified filtration. Here, we examine the decline in the density of flour particles descending
through a 40 m-tall tropical canopy on a windless day at Caxiuanã National Forest, Pará...
Premise of research. Angiosperms possess pollen dispersal units (PDUs) of varying size, from monads (single grains) to aggregates containing thousands of grains. It has been suggested that the degree of aggregation is related to the dispersal agent (in particular, animals vs. wind), but aggregation has rarely been measured, and its correlation with...
Precommercial thinning of jack pine (Pinus banksiana) stands is a common silvicultural method to control stand density and growth in managed boreal forest stands. If employed too early, vigorous conifer re-growth can reduce the radial growth and potential yield of residual trees, thus requiring additional costly thinning treatments and extended rot...
In this paper, we model the post-fire recruitment dynamics of two aerial seedbank species, Picea mariana and Pinus banksiana, in response to salvage logging. The model incorporates: (1) initial seed availability as a function of source tree basal area and proportion of stand salvaged; (2) seed abscission as a function of time; (3) seedling survivor...
In the eastern hardwood forests of North America ice storms are an important disturbance event. Ice storms strongly influence community dynamics as well as urban infrastructure via catastrophic branch failure; further, the severity and frequency of ice storms are likely to increase with climate change. However, despite a long-standing interest into...
The existence of non-serotinous, non-sprouting species in fire regimes
where serotiny confers an adaptive advantage is puzzling, particularly
when these species recruit poorly from soil seed banks or from burn
edges. In this paper, white spruce (Picea glauca (Moench) Voss) was used
to show how the timing of fire relative to seed development may per...
1. Diaspore abscission determines many aspects of seed dispersal by wind. While there is yet no complete mechanistic framework for understanding abscission by wind, empirical studies to date have suggested that abscission generally (i) occurs above some threshold wind speed and (ii) depends on the drag force generated by the wind.
2. We revisit the...
A table showing the technical specifications for Z+F imager 5006i.
(DOCX)
Registration reports for the alignment of the TLS scans from the Z+F laser scanner.
(DOCX)
Burned trees in the boreal forest are quickly colonized by wood-feeding beetles after fire. Roundheaded and flatheaded borers (Coleoptera: Cerambycidae, Buprestidae) are common wood-feeding beetles whose larvae feed on the phloem in the first instars before entering the xylem, where they excavate galleries several centimetres deep. These organisms...
The existence of non-serotinous, non-sprouting species in fire regimes
where serotiny confers an adaptive advantage is puzzling, particularly
when these species recruit poorly from soil seed banks or from burn
edges. In this paper, white spruce (Picea glauca (Moench) Voss) was used
to show that the timing of fire relative to seed development can co...
In the boreal forest, establishment of tree regeneration is tightly linked to both mast years and the availability of adequate germination beds for seedlings. We took advantage of a mast year (2006) in the eastern boreal mixedwood to compare seedling establishment in 2007 and seedling survival 2 and 4 years later on sections of fallen logs and equi...
Approximately 10 percent of plant species rely on wind for pollination
(anemophily). These include many taxa of economic importance: e.g.
cultigens such as wheat and maize; species like grasses and ragweed that
trigger allergies; and the conifers, our most important species for the
forest industry in the mid- latitudes. It has often been assumed th...
Seed dispersal distance-a key process in plant population dynamics-remains poorly understood because of the difficulty of finding a source plant so well isolated from conspecifics that seeds or seedlings can be unambiguously attributed to it. Inverse modeling (IM) of seed dispersal, a simple statistical technique for parameterizing dispersal kernel...
In this review, we focus on the biotic parameters that are crucial to an understanding of the recruitment dynamics of North American boreal tree species following natural (fire, budworm infestation, windthrow) or human-induced (clearcut, partial cut) disturbances. The parameters we emphasize are (i) the production of seeds and asexual stems (both o...
Many aspects of temporal variation in tree seed production (e.g., the proability distribution, periodicity, uni modality) are poorly understood. In this paper, we used 32 annual seed production records from 22 species to show that there are no discernible endogenous cycles, and there is a modest (but seldom significant) tendency for a high seed pro...
We examined the relationship between the post-fire regeneration density of Populus tremuloides Michx., Pinus banksiana Lamb., and Picea mariana (Mill.) BSP and their pre-fire basal area density at the spatial scale of 70 m (the width of the stands studied) in four fires in central Saskatchewan and one in Quebec. For these three species with mechani...
We studied the post-wildfire establishment of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) in the southern mixedwood boreal forest of Saskatchewan, Canada. The major objective of the study was to determine the influence of post-wildfire seedbed types on the juvenile survi...
We developed and tested a wind-dispersal model of tree recruitment into burns from living sources at the fire edge or from small unburned residual stands. The model was also tested on recruitment of serotinous Pinus banksiana Lamb. within a burn. The model assumed that source strength is proportional to basal area density and that an individual (po...
The response of four tree species, Acer saccharum Marsh., Acer rubrum L., Populus tremuloides Michx., and Betula populifolia Marsh., to ice storm damage was studied in the northern hardwood forest of southern Quebec. The focus of the study was the impact of ice accretion on trees as a function of damage type and species at the stand and regional sc...
We used a micrometeorological dispersal model to simulate seed and seedling distributions derived from subcanopy balsam fir (Abies balsamea (L.) Mill.) source trees in a trembling aspen (Populus tremuloides Michx.) dominated forest. Our first objective was to determine the effect of substituting basal area for cone production as a proxy for seed ou...
The application of micrometeorological models of heavy particle dispersal to winged diaspores (samaras) requires that the diaspores maintain stable flight and that descent velocity is constant with respect to vertical air motion. Others have argued that these assumptions may be invalid for autorotating samaras and that bilaterally symmetric samaras...
Long-distance seed dispersal figures prominently in most plant conservation biology arguments, yet we possess little more than anecdotes concerning the relationship among deposition (seeds/m2), source strength (seeds/m2), and distance. In this paper we derive two simple models for long-distance deposition. The models are tested at the scale of 100–...
1. While it is well known that many plant species enhance the dispersal of seeds by wind via traits such as lift-promoting wings and drag-producing fibres, we hypothesized that natural selection would also increase dispersal capacity through the evolution of mechanisms that promoted abscission by updrafts rather than downdrafts.
2. An experiment wi...
We studied the density of ascocarps (mushrooms) of morels (Morchella) and pixie cups (Geo-pyxis carbonaria) as a function of postfire duff (forest floor organic layer) depth in the first 4 y after a wildfire. The great majority of ascocarps of both species appeared in the first summer (2004) after an Aug 2003 fire in predominantly pine-spruce monta...
Trees growing in a seasonally tropical dry forest, with its characteristic 5-7-mo rainless interval, possess a variety of physiological adaptations to drought, the most common being leaf abscission. At the Estacion Biologia de Chamela in western Mexico, we experimentally examined the relationship between one-time experimental irrigation ranging as...
It is well known that post-fire duff layers that are thin or of lower porosity greatly enhance juvenile survivorship of sexually recruiting boreal plant species. Nonetheless, there has been no study on duff compaction by snow following charring. We examined post-fire duff depth for the first 3 years (two winters) after a 2006 wildfire in the boreal...
Well-combusted duff (<3 cm depth) is generally considered the best seedbed for small-seeded species on upland sites, but we ask here, What is the optimal, postfire residual duff thickness? We hypothesize that a duff thickness equal to (but not greater than) the length of the germinant will offer the best conditions, because at this thickness, the d...
In mixedwood boreal forests of western Canada, stands classified as “pure deciduous” by forest inventories sometimes contain a few large white spruce (Picea glauca (Moench) Voss) trees among or emerging from the canopy. These trees are important as regeneration seed sources and for habitat structure. Neither their abundance nor the characteristics...
Rates of decomposition were determined for the boles of Pinus contorta var. latifolia Engelm. and Picea engelmannii Parry ex. Engelm. in five lower subalpine forest stands in the Southern Canadian Rocky Mountains. Stands ranged in age from 58 to 222 yr since last fire. The date of death of standing dead and fallen boles was determined by cross-dati...
Summary • The role of collisions with vegetation elements in seed dispersal by wind has been examined only anecdotally. In particular, the idea that the effect of collisions in dispersal may depend on the aerodynamic class of the diaspore has not been broached. • We adapted a collision model for small particles to predict the probability of a winge...
Given the dependence of most wind-pollinated and wind-dispersed species on low relative humidity (RH) for abscission, and the minimization of RH in the early afternoon, there ought to be a marked directional bias in seed dispersal at sites with a strong local diurnal circulation. We filmed the abscission of seeds of five wind-dispersed tropical spe...
Although ice events also occur in the boreal forest and west of the prairies, little is written about the effect of freezing precipitation on forests in North America. The term "freezing precipitation" refers to both freezing rain with drop diameters of about 1 mm, and freezing drizzle with drop diameters of about 0.1 mm. The primary objective of t...
We compared prefire and postfire organic-layer depths in boreal forest types (14 fires) across Canada, and examined tree recruitment as a function of depth. There was extensive within-stand variation in depth, much of it due to clustering of thinner organic layers around boles. There were no significant differences in postfire organic-layer depth a...
In North America, Eurasia, and Australia, salvage logging is increasingly being used to mitigate economic losses due to fire, although the effects of this type of intervention are still essentially unknown. In a field experiment in a large recent boreal forest fire in central Quebec, we used 24 paired salvaged and non-salvaged stands to test the ef...
It has become clear that long-distance seed dispersal plays a crucial role in plant metapopulation persistence and response to rapid climate change. Recent studies of the role of convective vs. shear-generated updrafts in prompting long-distance dispersal using Taraxacum officinale as an example, suggest that (1) the probability of abscission is in...
Despite the importance of seedbeds in the life histories of many plant species, there has been little study of the seedbeds created by wildfire in fire-prone vegetation types such as the boreal forest. Both within the interior and at the edge of a very large (> 100 000 ha) 2001 wildfire in the mixedwood boreal region of Alberta, we examined the pos...
The aerodynamic constraints operating on the wind-dispersed, drag-producing diaspores of several species of the tropical family Bombacaceae were examined. Kapok (the drag-promoting appendage) was best characterized as a moderately flattened hemisphere impervious to air movement. The kapok shape was not isometric: kapok planform area was proportiona...
Spatial simulation models of long-term dynamics of forest landscapes are needed for investigating how different actual or potential disturbance regimes determine the structure and dynamics of forest landscapes. We propose a new approach to bridge the forest stand and landscape processes. Hence, while interested in the boreal forest dynamics at the...
1 We compared three commonly used empirical seed/seedling dispersal functions for trees (lognormal, 2Dt, and two-parameter Weibull) by analysis of published studies where the location of the source is known, as well as by inverse modelling within an old growth hardwood forest in southern Quebec. Almost all the species were wind-dispersed. 2 For the...
Most studies of postfire tree recruitment have occurred in severely burned portions, despite the fact that partial burning is common. In this study we examined regeneration following a 1997 fire in the boreal forest of Quebec. A model of postfire recruitment was elaborated using parameters such as the proportion of trees killed (severity), the prop...
The effects of different harvest intensities, including uncut, 1/3 and 2/3 partial cuts, clearcuts with and without slash, were investigated on the germination and cumulative survivorship of white spruce and balsam fir over 2 consecutive years. We also investigated the regenerative capacity of both species on three different seedbeds across all har...
The SAFE (sylviculture et aménagement forestiers écosystémique) project was set up in 1998 in the Lake Duparquet Research and Teaching Forest to test stand-level silvicultural treatments designed to reflect different aspects of natural forest dynamics. In the winter of 1998-1999, four levels of forest harvesting, including a no-harvest and a clearc...
Mean annual seed production is assumed to be proportional to basal area for canopy trees, but it is not known if subcanopy trees produce fewer seeds than expected (given their size) because of low light availability. Ovulate cone production was examined for balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss) in 1998...
We model and compare the biological and financial constraints of four prescriptions that serve as alternatives to conventional clearcutting followed by planting in eastern and western boreal mixedwood stands. These alternative prescriptions for full or partial conifer stocking are (1) reliance on advance regeneration with or without augmentation by...
The response of four tree species, Acer saccharum Marsh., Acer rubrum L., Populus tremuloides Michx., and Betula populifolia Marsh., to ice storm damage was studied in the northern hardwood forest of southern Quebec. The focus of the study was the impact of ice accretion on trees as a function of damage type and species at the stand and regional sc...
We developed and tested a wind-dispersal model of tree recruitment into burns from living sources at the fire edge or from small unburned residual stands. The model was also tested on recruitment of serotinous Pinus banksiana Lamb. within a burn. The model assumed that source strength is proportional to basal area density and that an individual (po...
We examined recommended sowing densities of 25 North American tree species (26 observations) to measure the relationship between juvenile survivorship and seed mass in large clearings and shelterwoods. Two models for expressing the relationship (simple power law or a cumulative negative exponential adjusted to account for rodent-repellent applicati...
1 We studied secondary seed dispersal on snow using a wind tunnel, experimental releases in clearings, and observations of the dispersal curve of an isolated Betula alleghaniensis in a large clearing. We derived a model for wind dispersal which couples the primary and secondary movement for a point source, and then used this to modify an area sourc...
Although there are many studies of wind dispersal of seeds from a forest into an adjacent clearing, no physical model has yet been advanced. The model constructed here calculates the trajectories of seeds from individual trees in the area source to a line of seed traps (in the clearing) oriented perpendicular to the forest edge. The model uses a lo...
Is there necessarily a trade-off between seed size (mass) and dispersal capacity for wind-dispersed diaspores? Within three families (Pinaceae, Aceraceae, and Leguminosae) with asymmetric samaras, shape is maintained (isometry) despite size change. Consequently, within these three families, equilibrium descent velocity is proportional to samara mas...
Winged fruits and seeds travel approximately twice as far as predicted by micrometeorological models of seed dispersal by the wind. The authors hypothesize that seeds preferentially abscise at higher velocities because the motive force for abscission is drag (proportional to the square of the wind velocity). In Acer saccharinum, separation layers d...
We examined the contribution of seed mass variation to (1) variation in terminal velocity and (2) variation in dispersal distances for species with winged seeds. Coefficients of variation of terminal velocity were usually on the order of 0.13. These values were too low to have a significant effect on distance variation because of the much larger ma...
The aerodynamics of plumed seeds are examined using 4 species of Compositae and Asclepias syriaca (Asclepiadaceae). The hairs comprising the plume of the seeds are modelled as a single long cylinder experiencing an ambient wind velocity equivalent to the measured terminal velocity in still air. The relevant measure of area is the total project area...
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We derived a micrometeorological model for the dispersal of winged or plumed seeds from a point source. The model is based on six measurable parameters: mean release height, mean and standard deviation of the terminal velocities of seeds, standard deviation of vertical wind velocities, and the mean and standard deviation of the natural logarithms o...
Salisbury has argued that anemochory is less efficient than zoochory. His evidence indicates that zoochores produce fewer seeds and that far dispersing anemochores produce more seeds than do near dispersing anemochores. Limiting our discussion to the anemochore's part of the hypothesis, we reformulate Salisbury's measure of dispersal capacity into...
The ideas of community structure and the expression of dominance, that of bio-logical succession, and finally that of climax, are based largely upon the assumption of long-term stability in the physical habitat. Remove this assump-tion and the entire theoretical structure becomes a shambles. . . . Disturbances have been so frequent and so generally...
Citations
... Our aim was to explore whether masting behaviours have wider implications for species and phenotypic diversification beyond their selective advantages for individual fitness [11]. We exploited a new database of 5057 population-level reproductive time series from 682 species-the largest synthesis of reproductive time-series data to date [25]. We first explored the utility of this database for evolutionary inference by comparing biases in the macroevolutionary characteristics of its species with the wider plant ToL. ...
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... The boreal forest has been changing in tree dominance from coniferous to broadleaf deciduous forests due to natural and anthropogenic disturbances (Baltzer et al. 2021;Laquerre et al. 2009;Marchais et al. 2020). These changes in turn affect understory composition and dynamics (Barbier et al. 2008). ...
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... Forests globally are increasingly vulnerable to ecological transformation due to changing climatic conditions that simultaneously increase wildfire activity (4-7) and alter key postfire demographic rates such as seedling establishment (8,9), a phenomenon broadly termed "interval squeeze" (10). Declines in tree recruitment have been observed globally, causing widespread concerns about forest loss following wildfires and other disturbances (1,3,(11)(12)(13). ...
... However, the emergence at two years after drought may potentially indicate associated masting investments. If cued by warm conditions [119] and with negative impacts on secondary growth due to internal resource competition [120], masting investment can theoretically also lead to single-year CSDs. However, species differ in reproduction strategies, cues, growth sensitivity and maturation times, and consequently are assumed to be averaged out within the groups in this study. ...