Sequoia Sempervirens Research Articles

Madison Grant and the Dark Side of the Conservation Movement

James B. Wheeler, a career Park Ranger/Interpreter with the National Park Service and interpreter in North Coast Redwoods State Parks, wrote a letter before retiring in 2017 to his superiors and other Parks employees about Madison Grant’s history, positive and negative. He asked for an adjustment to the stories told by the Prairie Creek memorial to Grant and the Founders Tree monument. His plea went unheard at the time, but it is central to the victory for historical truth and human decency that was achieved in more recent years. It is included here in its entirety as a necessary historical document (lightly edited for clarity and grammatical consistency).

The Ghost Forest: Racists, Radicals, and Real Estate in the California Redwoods

The Ghost Forest: Racists, Radicals, and Real Estate in the California Redwoods

The Metasequoia genome and evolutionary relationships among redwoods

Redwood trees (Sequoioideae), including Metasequoia glyptostroboides (dawn redwood), Sequoiadendron giganteum (giant sequoia), and Sequoia sempervirens (coast redwood), are threatened and widely recognized iconic tree species. Genomic resources for redwood trees could provide clues to their evolutionary relationships. Here, we report the 8-Gb reference genome of M. glyptostroboides and a comparative analysis with two related species. More than 62% of the M. glyptostroboides genome is composed of repetitive sequences. Clade-specific bursts of long terminal repeat retrotransposons may have contributed to genomic differentiation in the three species. The chromosomal synteny between M. glyptostroboides and S. giganteum is extremely high, whereas there has been significant chromosome reorganization in S. sempervirens. Phylogenetic analysis of marker genes indicates that S. sempervirens is an autopolyploid, and more than 48% of the gene trees are incongruent with the species tree. Results of multiple analyses suggest that incomplete lineage sorting (ILS) rather than hybridization explains the inconsistent phylogeny, indicating that genetic variation among redwoods may be due to random retention of polymorphisms in ancestral populations. Functional analysis of ortholog groups indicates that gene families of ion channels, tannin biosynthesis enzymes, and transcription factors for meristem maintenance have expanded in S. giganteum and S. sempervirens, which is consistent with their extreme height. As a wetland-tolerant species, M. glyptostroboides shows a transcriptional response to flooding stress that is conserved with that of analyzed angiosperm species. Our study offers insights into redwood evolution and adaptation and provides genomic resources to aid in their conservation and management.

Summer reading 2023In a Flight of Starlings: The Wonders of Complex Systems, Giorgio Parisi, Penguin Press, 2023, 144 pp.I Feel Love: MDMA and the Quest for Connection in a Fractured World, Rachel Nuwer, Bloomsbury, 2023, 384 pp.Many Things Under a Rock: The Mysteries of Octopuses, David Scheel, Norton, 2023, 320 pp.The Hidden History of Code-Breaking: The Secret World of Cyphers,

Summer reading 2023In a Flight of Starlings: The Wonders of Complex Systems, Giorgio Parisi, Penguin Press, 2023, 144 pp.I Feel Love: MDMA and the Quest for Connection in a Fractured World, Rachel Nuwer, Bloomsbury, 2023, 384 pp.Many Things Under a Rock: The Mysteries of Octopuses, David Scheel, Norton, 2023, 320 pp.The Hidden History of Code-Breaking: The Secret World of Cyphers,

Using terrestrial laser scanning to evaluate non-destructive aboveground biomass allometries in diverse Northern California forests

A crucial part of carbon accounting is quantifying a tree’s aboveground biomass (AGB) using allometric equations, but species-specific equations are limited because data to inform these equations requires destructive harvesting of many trees which is difficult and time-consuming. Here, we used terrestrial laser scanning (TLS) to non-destructively estimate AGB for 282 trees from 5 species at 3 locations in Northern California using stem and branch volume estimates from quantitative structure models (QSMs) and wood density from the literature. We then compared TLS QSM estimates of AGB with published allometric equations and used TLS-based AGB, diameter at breast height (DBH), and height to derive new species-specific allometric AGB equations for our study species. To validate the use of TLS, we used traditional forestry approaches to collect DBH (n = 550) and height (n = 291) data on individual trees. TLS-based DBH and height were not significantly different from field inventory data (R2 = 0.98 for DBH, R2 = 0.95 for height). Across all species, AGB calculated from TLS QSM volumes were approximately 30% greater than AGB estimates using published Forest Service’s Forest Inventory and Analysis Program equations, and TLS QSM AGB estimates were 10% greater than AGB calculated with existing equations, although this variation was species-dependent. In particular, TLS AGB estimates for Quercus agrifolia and Sequoia sempervirens differed the most from AGB estimates calculated using published equations. New allometric equations created using TLS data with DBH and height performed better than equations that only included DBH and matched most closely with AGB estimates generated from QSMs. Our results support the use of TLS as a method to rapidly estimate height, DBH, and AGB of multiple trees at a plot-level when species are identified and wood density is known. In addition, the creation of new TLS-based non-destructive allometric equations for our 5 study species may have important applications and implications for carbon quantification over larger spatial scales, especially since our equations estimated greater AGB than previous approaches.

Northern spotted owl nesting habitat under high potential wildfire threats along the California Coastal Redwood Forest

Large and severe wildfires, exacerbated by climate change and human behavior, are occurring more frequently in many forests across the western United States. While wildfire is a natural part of most terrestrial ecosystems, rapidly changing fire regimes have the potential to alter habitat beyond the adaptive capabilities of species. Spatial assessments of wildfire risks to species habitat may allow managers to pinpoint locations for management activities. To illustrate this, we spatially assessed wildfire risk within habitat that supports the nesting activity of the federally threatened northern spotted owl (Strix occidentalis caurina) in the California redwood coast ecoregion. To accomplish this, we built a scale-optimized ensemble nesting habitat suitability model and identified habitat with the highest wildfire hazard potential. Percent canopy cover at 100-m scale, slope at 400-m scale, and January precipitation at 800-m scale were the most influential environmental covariates for predicting northern spotted owl nesting habitat. Nearly 60% of nesting habitat was predicted to be at high or very high (>1986 index value) wildfire risks. We identified three areas in the Maple Creek Area of Humboldt County, Jackson State Demonstration Forest in Mendocino County, and Point Reyes National Seashore in Marin County, California with a high concentration of nesting habitat that are at a very high risk of experiencing high severity wildfires. We recommend these areas be targeted for future research to understand the impact of wildfire on northern spotted owl as well as management attention.

Characterizing lift, drag, and pressure differences across wandering salamanders (Aneides vagrans) with computational fluid dynamics to investigate aerodynamics.

Wandering salamanders (Aneides vagrans), known to occupy the crowns of old growth coast redwood trees, have recently been found to decelerate and engage in controlled, nonvertical descent while falling. Closely related, nonarboreal species with seemingly minor morphological differences exhibit far less behavioral control while falling; however, the influence of salamander morphology on aerodynamics remains to be tested. Here, we examine differences in morphology and aerodynamics of two salamander species, A. vagrans and the nonarboreal ensatina salamander (Ensatina eschscholtzii), using a combination of traditional and contemporary techniques. Specifically, we compare morphometrics statistically, then use computational fluid dynamics (CFD) to characterize predicted airflow and pressure over digitally reconstructed models of the salamanders. While similar in body and tail lengths, A. vagrans are more dorsoventrally flattened with longer limbs and greater surface area of the foot relative to body size than the nonarboreal E. eschscholtzii. CFD results show dorsoventral pressure gradients differ between the two digitally reconstructed salamanders resulting in lift coefficients of approximately 0.02 and 0.00, and lift:drag ratios of approximately 0.40 and 0.00 for A. vagrans and E. eschscholtzii, respectively. We conclude that the morphology of A. vagrans is better suited for controlled descent than that of the closely related E. eschscholtzii and highlight the importance of subtle morphological features, such as dorsoventral flatness, foot size, and limb length, for aerial control. That our simulation reports align with real-world performance data underscores the benefits of CFD for studying the link between morphology and aerodynamics in other taxa.

Overcoming crossdating challenges to generate ring-width chronologies for Sequoia sempervirens across its native range

We utilize a large dendrochronological dataset for Sequoia sempervirens of 1.29 million rings from 5952 series for 278 trees to generate location and regional ring-width chronologies and to investigate constraints on crossdating. Increment cores were collected at regular height intervals along the trunk via free-hanging ropes with some terrestrial deadwood sampled. Inter-annual chronologies span 86–1687 yr for 47 locations in primary and secondary forests across the native Sequoia range. Shared signals based on declining strength of paired correlations with distance, strong correlations within regions, and groupings of principal components guide chronology creation for northern (1032 yr, 108 trees) and southern (865 yr, 52 trees) regions and four sub-regions. The suite of chronologies provides location-specific references as well as more robust regional indices that reflect distinct signals along a climatically-integrative latitudinal gradient. Secondary forests date to near completion, and we use a subset of data to assess crossdating for trees in primary forests. Among tree and landscape attributes, old age is the most important predictor of undated and missing rings, and undated rings align with periods of reduced biomass production distributed across centuries-long lifespans. Crossdating metrics vary by height above the ground with breast height (BH) and 10 m samples having more undated rings than upper samples. At 10 m, samples have the most missing rings. Buttressing affects the lower trunk as BH series have higher ring widths and lower interseries correlations compared to those up to 70 m. Whole-trunk sampling maximizes success for crossdating old, structurally-complex Sequoia and enables dating of crown damage and assessment of biomass dynamics related to environmental change. Reference chronologies, regional assessments, and crossdating insights collectively guide future study of Sequoia for applications including climatology, fire ecology, and seismology.

Heavy crown thinning in redwood/Douglas-fir gave superior forest restoration outcomes after 10 years

Forest restoration thinning has the potential to enhance the structural complexity and accelerate the development of large trees important to wildlife, aesthetics, and wildfire resistance. These are key objectives for the restoration of even-aged secondary forests within Redwood National Park in Humboldt County, CA, USA. We evaluated the tree growth and stand structure 10 years after two thinning methods were applied at two intensities in a 40-year-old mixed redwood ( Sequoia sempervirens (Lamb. ex D. Don) Endl.)/Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stand. Heavy thinning enhanced the diameter growth of redwood and Douglas-fir trees more than light thinning. Crown thinning generally enhanced the structural diversity more than low thinning, and structural diversity increased progressively over the 10 years following thinning. Understory plant richness fluctuated between measurement years. Heavy thinning enhanced the understory shrub cover. The fastest-growing trees in heavily thinned stands were much more likely to sustain bear damage, especially redwood trees. Overall, different thinning methods and intensities induced a different suite of outcomes, yet none restored redwood dominance, but all treatments enhanced some other ecosystem values important for old-growth restoration such as large overstory trees, understory plant and shrubs, and elements of structural complexity, including tree-size variability, snags, down logs, and trees exhibiting stem or top damage.

THE INFLUENCE OF ENDOGENOUS POLYPHENOLS, PHOTOPERIOD AND MINERAL COMPOSITION OF THE NUTRIENT MEDIUM ON THE FORMATION OF CALLUS TISSUE OF RELIC GYMNOSPERMS SEQUOIA SEMPERVIRENS (D.DON) ENDL.

Relrvance. Sequoia sempervirens (D.Don) Endl. are the tallest relict long–lived plants characterized by a limited range of growth. Valuable sequoia wood is able to accumulate unique secondary metabolites that do not have synthetic analogues. Sequoia plants grow in specialized microecological niches that limit their natural distribution area. It is known that biotic stress is one of the main environmental factors limiting the introduction of valua-ble plant species – possible sources of production of unique metabolites. Limiting environmental factors have a direct impact on the growth, develop-ment and productivity of secondary plant metabolism. Stress-resistant and highly productive plants can be created using cell biotechnology methods, in particular, in vitro cell selection, which is carried out on a callus culture. Therefore, at the first stage, it is necessary to develop in vitro technology for the rapid production of well-proliferating callus tissue. Purpose of the study. To study the effect of the mineral composition of the nutrient medium, photoperiod and endogenous polyphenols on the for-mation of the callus tissue of sequoia (Sequoia sempervirens (D.Don) Endl.) in vitro. Material and methods. The object of the study was Sequoia sempervirens (D.Don) Endl. plants. Callus tissue was obtained from segments of leaf blades and stem internodes, which were isolated from intact plants. Explants were cultured on MS and WPM nutrient medium containing BAP 2.5 mg/l and 2.5 mg/L 2,4-D. The localization of phenolic compounds was studied in the leaves, stems, apical buds of sequoia plants, as well as in callus tis-sue obtained on a nutrient medium with different mineral composition and under different lighting conditions. To do this, histochemical methods were used: for the sum of phenolic compounds, the material was stained with 0.08% Fast Blue reagent raster, a reaction with vanillin reagent in hydrochloric acid vapor was used to study the localization of flavans (catechins and proanthocyanidins). Results. It was found that the applied lighting mode had a significant effect on the intensity of callus tissue formation, its consistency and color. A well-proliferating callus tissue of light yellow color was obtained on two types of nutrient media with no light source. At a 16–hour photoperiod, a dark brown callus tissue was formed, which died during cultivation. As a rule, callus tissue was formed in those places where the localization of phenolic compounds was insignificant. It was found that in the initiated callus cultures grown on the studied nutrient media with no illumination, the content of cells with phenolic compounds was less than that of callus obtained on the same nutrient media, but with the presence of illumination. Conclusion. Sequoia plants have the ability to synthesize polyphenols, including the flavan series, which is preserved under in vitro conditions. The mineral composition of the studied nutrient media does not significantly affect the biosynthetic ability to form polyphenols in vitro cultures and their growth characteristics.

GC/MS Analysis and Secondary Metabolites Determination with Antioxidant and Anticancer Evaluation of Sequoia sempervirens (D. Don) Endl. through Micropropagated Cultures

GC/MS Analysis and Secondary Metabolites Determination with Antioxidant and Anticancer Evaluation of Sequoia sempervirens (D. Don) Endl. through Micropropagated Cultures

Using heat plumes to simulate post-fire effects on cambial viability and hydraulic performance in Sequoia sempervirens stems.

Injury to the xylem and vascular cambium is proposed to explain mortality following low severity fires. These tissues have been assessed independently, but the relative significance of the xylem and cambium is still uncertain. The goal of this study is to evaluate the xylem dysfunction hypothesis and cambium necrosis hypothesis simultaneously. The hot dry conditions of a low severity fire were simulated in a drying oven, exposing Sequoia sempervirens (Lamb. ex D. Don) shoots to 70 and 100 °C for 6-60min. Cambial viability was measured with Neutral Red stain and water transport capacity was assessed by calculating the loss of hydraulic conductivity. Vulnerability curves were also constructed to determine susceptibility to drought-induced embolism following heat exposure. The vascular cambium died completely at 100 °C after only 6min of heat exposure, while cells remained viable at 70 °C temperatures for up to 15min. Sixty minutes of exposure to 70 °C reduced stem hydraulic conductivity by 40%, while 45min at 100 °C caused complete loss of conductivity. The heat treatments dropped hydraulic conductivity irrecoverably but did not significantly impact post-fire vulnerability to embolism. Overall, the damaging effects of high temperature occurred more rapidly in the vascular cambium than xylem following heat exposure. Importantly, the xylem remained functional until the most extreme treatments, long after the vascular cambium had died. Our results suggest that the viability of the vascular cambium may be more critical to post-fire survival than xylem function in S. sempervirens. Given the complexity of fire, we recommend ground-truthing the cambial and xylem post-fire response on a diverse range of species.

A FLORISTIC STUDY OF SWANTON PACIFIC RANCH, SANTA CRUZ COUNTY, CALIFORNIA

The Swanton Pacific Ranch (SPR) is located north of the town of Davenport, in Santa Cruz County, California, and is owned by California Polytechnic State University, San Luis Obispo. SPR is approximately 1295 ha and contains areas of salt marsh, coastal prairie, coastal bluff scrub, northern coastal scrub, riparian forest, redwood forest, mixed evergreen forest, and chaparral. The property extends over an elevational gradient from 0 m to 420 m. In this study, we conducted a floristic inventory at SPR and documented 636 taxa. Between 2017 and 2019 we vouchered 547 taxa with 974 specimens. We were unable to locate 63 taxa that had been previously reported, 27 represented from historic collections and 36 represented by personal observations, but lacking vouchers. We relocated, but did not collect, 26 taxa known from previous collections. Overall, we documented 93 families at SPR, with Asteraceae, Poaceae, and Fabaceae having the most species, respectively. California rare taxa, listed by the California Native Plant Society, made up 2.5% of the flora (n = 18). Locally rare taxa made up 10% of the flora (n = 65). Non-native taxa made up 26% of the flora (n = 169). We vouchered one new taxon for Santa Cruz County, Senecio aphanactis Greene, which has a California Rare Plant Rank of 2B.2; documented a new occurrence of Hesperocyparis abramsiana (C.B.Wolf) Bartel var. abramsiana, a Federally Threatened conifer; and collected a form of Sanicula crassicaulis Poepp. Ex DC that we have published as a distinct variety. Overall, this relatively small coastal ranch contained approximately 10% of the flora of California. The 2020 CZU Lightning Complex Fire burned ca. 90% of SPR within a year of this study being completed. This opens the possibility for this study to be used as a baseline for future studies examining post-fire shifts in plant diversity at a landscape scale.

Predicting timber theft based on environmental features – Insights from Humboldt Redwoods State Park, US

ObjectiveThere's a small but growing body of evidence that wildlife crime mirrors the spatial concentrations we see with traditional, high-volume urban crimes. Yet, the majority of this literature has focused on the poaching of fauna, not flora. Therefore, it is unclear whether poaching of flora—both plants and trees—is spatially concentrated and can be explained by both the natural and built landscape. This study set out to empirically examine this question as it relates to the illicit removal of downed redwood trees in Humboldt Redwoods State Park (HRSP)—home to the largest contiguous area of old-growth redwood forest on Earth. MethodsGeo-coordinate data of redwood theft was recorded and mapped along with environmental features such as roads, trails, parking points, campgrounds, and redwood old-growth distribution. A spatial econometric model was used to measure the presence or absence of each variable in 499 grid cells (1 sq. km each) that make up HRSP on the outcome of redwood theft. ResultsA Firth's penalized likelihood logistic regression model found that poaching was more likely to occur in areas with closer proximity to roads, presence of parking spots or trails, in areas with old growth redwoods, and that was more distant from campground sites. ImplicationsSeveral spatially explicit interventions are proposed to reduce natural resource theft in HRSP using situational crime prevention as a guide.

Bat Use of Hollows in California's Old-Growth Redwood Forests: From DNA to Ecology.

The loss of roosting resources, either through disturbance or removal, negatively affects bats. Identifying sensitive species and determining roost requirements are critical components in conserving their habitat. Cavity-roosting bats on the North Coast of California are known to use hollows in large redwood trees. In this study, we examined the factors determining the use of basal tree hollows by different bat species at eight redwood forest sites in Del Norte, Humboldt, and Mendocino Counties, California. Bat guano was collected from 179 basal hollow roosts from 2017 to 2018, and guano mass was used as an index of roosting activity. Nine bat species and one species group were identified by analysis of DNA in guano. We made a total of 253 identifications from 83 hollows into the 10 species categories. The most prevalent species were Myotis californicus (California myotis; 28.5% of all identifications), the Myotis evotis-Myotis thysanodes group (17.4%), Corynorhinus townsendii (17.0%), and Myotis volans (15.0%). We evaluated the extent to which habitat variables at the scales of the hollow, vicinity, and site influenced the level of roost use. The correlations between guano mass and habitat variables were examined using generalized additive mixed models. At the hollow scale, guano mass increased with ceiling height above the opening. At the vicinity scale, guano mass increased with less cover of small trees. At the site scale, there was no association between guano mass and distance to foraging areas, elevation, or the number of nearby hollows. These tree hollow roost preferences can inform land managers when planning the management and conservation of redwood forests.

Rangewide climatic sensitivities and non-timber values of tall Sequoia sempervirens forests

Heavily exploited for its reddish, decay-resistant heartwood, the tallest conifer, Sequoia sempervirens, is a major component of coastal forests from extreme southwestern Oregon to California’s Santa Lucia Mountains. Primary Sequoia forests are now restricted to < 5 % of their former distribution, and mature secondary forests with trees over 60 m tall are even scarcer due to repeated logging. Leveraging allometric equations recently derived from intensive work in both forest types, we climbed, measured, and core-sampled 235 trees in 45 locations distributed across the species range to examine growth trends and understand how tall Sequoia are responding to recent environmental changes. Paired samples of sapwood and heartwood collected along the height gradient were used to quantify Sequoia investment in decay resistance. During the 20th century, trees in most locations began producing more wood than expected for their size with this growth surge becoming pronounced after 1970 and ending around 2000. Radial increments—ring widths—correlate with climatic variables related to water availability, and these relationships are strengthening as temperatures rise. Sensitivity to drought increased from north to south along a 6° latitudinal gradient of decreasing precipitation and summer fog frequency. Sequoia trees north of 40° were least sensitive to drought, producing similar biomass annually during dry and wet years, whereas trees farther south produced less biomass during individual drought years. Hotter 21st century drought barely affected Sequoia growth efficiency (biomass increment per unit leaf mass) north of 40° until the fourth consecutive year (2015), when growth efficiency dropped precipitously, recovering within two years. South of 40°, Sequoia trees exhibited steadily declining growth efficiency during the multi-year drought followed by recovery, but recovery did not occur south of 37° despite ample precipitation in 2017. Sequoia growth efficiency is currently highest in secondary forests north of 40°, where trees produce relatively small amounts of heartwood with the lowest decay resistance (least fungicide) while receiving the most nocturnal summer fog. Increasing sink limitations, whereby rising temperatures, drier air at night, and extreme tree height collectively lower turgor pressure to inhibit cambial activity, may reduce Sequoia growth efficiency while contributing to more durable biomass production. Heartwood and fungicide increments are higher in primary than secondary forests across the species range. Crown structural complexity promotes development of vascular epiphytes and arboreal soil habitats in Sequoia forests with sufficient moisture availability. These habitats are lacking in secondary forests and rare in primary forests south of 40°. After logging, restoration of tall Sequoia forests can be achieved via silviculture that maximizes height increments during early stand development and then retains some dominant trees in perpetuity, allowing them to gain full stature, produce increasingly decay-resistant heartwood, and support significant arboreal biodiversity.

Acclimation of interacting leaf surface traits affects foliar water uptake.

Absorption of water across the surfaces of leaves is an ecologically important aspect of tree physiology. Variation in foliar water uptake capacity depends on environmental conditions when traits associated with the uptake pathway respond to climatic signals. Using a series of experiments, we verify that water enters Sequoia sempervirens (D. Don) Endl. leaves by crossing the cuticle, and show that surface-trait acclimation alters the kinetic parameters of foliar water uptake. Under our experimental conditions, the cuticle was the primary pathway for water entry into the leaf. Exposure to climatic variation may induce surface acclimations, such as increased waxiness, that reduce water-film formation over stomata at the expense of dry-season foliar uptake rates. We found that water uptake is negatively associated with the interaction of leaf-surface wax coverage and stomatal density, and provide an accessible protocol to measure these key traits in Sequoia. Linking absorptive pathways and trait acclimation to physiological performance can provide a foundation for range-wide or genomic investigations of forest interactions with water and a mechanism-centered means to monitor canopy hydraulic parameters over time.

Relationships between Xylem Transport, Anatomical, and Mechanical Traits at Organ Level of Two Cupressaceae Species

Compared to arid regions, forests in humid regions can be more vulnerable to drought as they are not used to, and thus not adapted to, water stress. Therefore, it is vital to understand the drought responses of woodland species in humid areas. Xylem structures and functions of species growing in the humid regions are the key to their drought responses. Two Cupressaceae species (including three taxa: Sequoia sempervirens, Taxodium distichum and its variety Taxodium distichum var. imbricatum) grown in a mesic common garden were targeted, and their xylem hydraulic function (hydraulic conductivity, Ks; cavitation resistance, P50), anatomical structure (tracheid and pit structure), and mechanical support (wood density, WD; tracheid thickness-to-span ratio, Ttob) were measured. Likewise, we analyzed the differences in hydraulic function and anatomical structure of xylem in branches and roots, and the quantitative relationship between xylem water transport, anatomical structure, and mechanical support. Our results showed that roots had a higher hydraulic conductivity and a weaker cavitation resistance than branches. There was no safety–efficiency trade-off in the branches and roots within species. Tracheid mechanical support had a trade-off relationship with Ks or P50 (negative correlation appeared in branch Ks ~ WD and root Ks ~ Ttob of S. sempervirens, root P50 ~ Ttob of T. distichum var. imbricatum, and branch P50 ~ WD). There was no trade-off in anatomical structure, which led to no safety–efficiency trade-off in xylem function. Our results suggest that the two species exhibit both low efficiency and low safety in xylem, and that there is no safety–efficiency trade-off in branches and roots. The reason behind this is that the structural demand for high safety and high efficiency differs (i.e., the root Ks of S. sempervirens was strongly controlled by Dh; in contrast, the root P50 of S. sempervirens was strongly determined by tracheid density, N). Namely, the structural basis for a safety–efficiency trade-off does not exist and therefore trade-offs cannot be achieved.

Modelling tree diameter of less commonly planted tree species in New Zealand using a machine learning approach

Abstract A better understanding of forest growth and dynamics in a changing environment can aid sustainable forest management. Forest growth and dynamics data are typically captured by inventorying a large network of sample plots. Analysing these forest inventory datasets to make precise forecasts on growth can be challenging as they often consist of unbalanced, repeated measures data collected across large geographic areas with corresponding environmental gradients. In addition, such datasets are rarely available for less commonly planted tree species, and are often incomplete and even more unbalanced. Conventional statistical approaches are not able to deal with such datasets and identify the different factors that interactively affect forest growth. Machine learning approaches offer the potential to overcome some of the challenges with modelling complex forest dynamics in response to environmental and climatic factors, even with unbalanced inventory data. In this study, we employed a widely used machine learning algorithm (random forests) to model individual tree diameter at breast height (DBH, 1.4 m) in response to age, stocking, site and climatic factors for the following five less commonly planted tree species groups in New Zealand: Cupressus lusitanica (North Island); Cupressus macrocarpa (South Island); Eucalyptus nitens; Sequoia sempervirens; Podocarpus totara; and Leptospermum scoparium. Data to build machine learning models were extracted and combined from three national level databases, and included stand variables, information about sites and climate features. The random forest models were able to predict tree DBH with high precision for the five-tree species (R2 &amp;gt; 0.72 and root-mean-square error ranged from 2.79–11.42 cm). Furthermore, the random forest models were interpretable and allowed us to explore the effects of site, environmental and climate factors on forest growth. To our knowledge, this is the first attempt to utilize machine learning approaches to model tree diameter of less common planted forest tree species in New Zealand. This approach can be used to forecast more precise forest growth and carbon sequestration to help us understand how different forest types and species are affected by the changing climate.

MODIS sensors can monitor spatiotemporal trends in fog and low cloud cover at 1 km spatial resolution along the U.S. Pacific Coast

Fog and low cloud cover (FLCC) provide critical moisture for ecosystems along the Pacific Coast during the summer months and it is currently unclear how climate change has affected FLCC occurrence. Additionally, FLCC impacts visibility and transportation safety for both road and air traffic. As such, a method for the monitoring of FLCC is necessary to inform land management decisions for fog-obligate species and to improve transportation safety, among other applications. Several gaps exist in current FLCC detection methodologies and while the Moderate Resolution Spectroradiometer (MODIS) sensor has previously been used to detect fog, its utility has not been validated. In this study, we create a 20 year (2000–2020) FLCC dataset using the Terra MODIS cloud flags and examine its effectiveness in detecting daily and monthly FLCC presence along the California and southern Oregon coast for the summer months (June–September). We validate the accuracy of this method using an existing FLCC dataset derived from Geostationary Operational Environmental Satellite (GOES) observations collected at 15 min intervals from 2000 to 2009. The two FLCC datasets have a strong linear relationship for FLCC frequency for each summer month, with an average r2 of 0.82 and p-value of <0.01. This strong relationship demonstrates the ability of Terra MODIS to reliably and accurately detect FLCC. Finally, we demonstrate a case study application of our FLCC dataset in a time series analysis over five coast redwood (Sequoia sempervirens) state parks in the Big Sur region of coastal California. This case study highlights the benefits provided by a 1 km resolution FLCC dataset for ecological applications and for monitoring spatiotemporal FLCC patterns across summer months over two decades. Our case study results showed that the number of foggy days fluctuates considerably year-to-year with no discernible positive or negative trend occurring between 2000 and 2020. Finally, we present a freely-accessible Google Earth Engine application to view and download the monthly FLCC data for all summer months for the years 2000–2020. The methods and dataset presented in this paper provide a means for efficient, daily FLCC monitoring at 1 km2 resolution, as well as the capacity for historical FLCC analyses.