Robert Van Pelt

University of Washington Seattle | UW · School of Environmental and Forest Sciences

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 t...

The tallest conifers—Picea sitchensis, Pseudotsuga menziesii, Sequoia sempervirens, Sequoiadendron giganteum—are widely distributed in western North America, forming forests > 90 m tall with aboveground biomass ≥ 2000 Mg ha⁻¹. Here we combine intensive measurements of 169 trees with dendrochronology and allometry to examine tree and stand developme...

Mature second-growth coast redwood (Sequoia sempervirens) forests—logged over 100 yr ago—are an important resource in the redwood region, but development of regenerating forests beyond rotation age (~50 yr) is not well understood. Continuous long-term data are especially lacking, considering that the maximum possible age of second-growth stands is...

The tallest species, Sequoia sempervirens, inhabits old-growth forests with global maximum biomass and leaf area. Here we determine if these forests also have maximum productivity. Intensive measurements of 114 trees 18–116 m tall and 115–2340 yr old were used to improve allometric equations for Sequoia. Applying the best available allometry to all...

The largest tree species, Sequoiadendron giganteum has a small native range restricted to California’s Sierra Nevada. Awe-inspiring stature contributed to its protection from logging, but anthropogenic climate change—particularly hotter drought—and over a century of fire suppression are possible threats. We measured 60 trees in seven forests to imp...

Large trees are critically important for structuring ecosystems and providing habitat, and trees with complex crowns provide more of these services than comparably sized trees with simple crowns. Forest managers are increasingly emulating old-growth structure by retaining various densities of aggregated and dispersed trees. This study explores how...

Mature second-growth forests dominated by Sequoia sempervirens occupy only two percent of the species’ current distribution yet represent an important benchmark for restoration management. Here we develop new allometric equations for these forests based on 44 trees 23–84 m tall, which can be used to estimate leaf, bark, cambium, sapwood, and heartw...

One of the five tallest tree species, Pseudotsuga menziesii has enormous economic and ecological importance, but rainforests dominated by this species are not as well understood as their drier montane counterparts. We climbed and measured 30 trees up to 97 m tall growing in coastal forests of the Olympic Peninsula and northern California to quantif...

Tree biomass is one of the most important variables for studying and managing forest ecosystems. With emphasis shifting from young forests grown for timber production to forests with old-growth characteristics, the need to quantify various components of individual trees in natural settings is increasing. Destructive methods are inherently limited b...

Fires that burn through forests cause changes in wood anatomy and growth that can be used to reconstruct fire histories. Fire is important in Sequoia sempervirens (D. Don) Endl. (coast redwood) forests, but fire histories are limited due to difficulties crossdating annual rings of this species. Here we investigated three fires (1985, 1999, 2008) in...

The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of Sagole Big tree, a giant African baobab from Limpopo, South Africa. Several wood samples were collected from the walls of its inner cavity and dated by radiocarbon. The age values along the cavity samples increase with the distance into the wood. This anomaly...

Forests >80 m tall have the highest biomass, and individual trees in these forests are Earth’s largest with deep crowns emerging above neighboring vegetation, but it is unclear to what degree these maxima depend on the emergent trees themselves or a broader-scale forest structure. Here we advance the concept of _emergent facilitation_, whereby emer...

Predicting tree biomass and growth increments via allometric equations is routine in forestry, but this approach is problematic in old-growth forests unless equations are derived from trees spanning the full size range. Using intensive measurements of 27 standing Eucalyptus regnans trees 61.1–99.8 m tall and 80–430 years old in Tasmania, Victoria,...

As the only species exceeding 90 m in height and 2000 years of age, Sequoia sempervirens and Sequoiadendron giganteum provide the optimal platform upon which to examine interactions among tree structure, age, and growth. We climbed 140 trees in oldgrowth redwood forests across California, USA, spanning a broad range of sizes and including the talle...

Background/Question/Methods As part of a larger study addressing the response of Sequoia sempervirens to changing environmental conditions throughout its range, three 1-hectare plots (plot dimensions were 10:1, 316.23 m x 31.623 m) were installed in upland portions of old-growth rain forests at the northern end of the species range. In these rain...

Background/Question/Methods Among unsuppressed trees in the world’s tallest forest (i.e., along Bull Creek in Humboldt Redwoods State Park, California), the annual rate of aboveground growth increases with tree size through old age such that the tallest and largest trees produce the most wood annually. Here we extend whole-crown measurements of S...

Introduction For large trees without a continuous sequence of growth rings in their trunk, such as the African baobab (Adansonia digitata L.), the only accurate method for age determination is radiocarbon dating. As of today, this method was limited to dating samples collected from the remains of dead specimens. • Methods Our research extends signi...

The effect of the spatial distribution of trees and foliage on understory conditions was examined in six tall old-growth forests along the Pacific Coast: two sites each in Washington, Oregon, and California. Detailed field measurements of crown parameters were collected on over 9000 trees encompassing over 14.5 ha in the stands. Crown parameters we...

Treetops become increasingly constrained by gravity-induced water stress as they approach maximum height. Here we examine the effects of height on seasonal and diurnal sap flow dynamics at the tops of 12 unsuppressed Sequoia sempervirens (D. Don) Endl. (coast redwood) trees 68-113 m tall during one growing season. Average treetop sap velocity (V(S)...

The article reports the first radiocarbon dating of a live African baobab (Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15–20 cm in the wood, we...

How long forest trees can sustain wood production with increasing age remains an open question, primarily because whole-crown structure and growth cannot be readily measured from the ground or on felled trees. We climbed and directly measured crown structures and growth rates of 43 un-suppressed individuals (site trees) of the two tallest species –...

Floodplains in the Pacific Coastal Ecoregion (PCE) stem from steep eroding mountain landscapes in a rain forest environment, and sustain a rich array of natural resources. Like floodplains elsewhere, many of the approximately 200 coastal river valleys are profoundly altered by flow regulation and land conversion for agriculture and urban developmen...

Background/Question/Methods While the importance of old trees and ancient forests as reservoirs of carbon is well established, their capacity to respond to changing climate and rising atmospheric carbon dioxide is poorly understood. We used a combined dendrochronological and tree mapping approach to reconstruct whole-tree wood production for the p...

Background/Question/Methods Forest stands undergo long-term changes in composition, structure, and function as a consequence of: internal processes related to demography and competitive interactions; disturbances at a variety of scales, frequencies and causes, and changes in basic environmental conditions, such as climate. The long time periods inv...

Background/Question/Methods Late-successional and old-growth forests have been studied in many moist temperate regions of the world, but only recently have researchers begun to collaborate on global assessments of old-growth ecosystem structure and function. Our research goal was to explore ecological characteristics shared by and diverging among...

Seventy trees from seven stands 50-650 years old were selected for this investigation of crown structural development in Pseudotsuga menziesuii All branches, limbs, and trunks were nondestructively measured for size, structure, and location while climbing the trees with ropes. These data were used to generate a computer model of each tree's crown t...

Sequoia sempervirens (redwood) is a long-lived, shade-tolerant tree capable of regeneration without disturbances and thus often present in all sizes within a single forest. In order to evaluate functional linkages among structures, plant distribution, and biodiversity in the canopy, we quantified all vascular plants from ground level to the treetop...

We examined how composition and structure of old-growth and mature forests at Mount Rainier National Park changed between the mid-1970s and mid-1990s. We assessed whether the patterns of forest dynamics observed in lower elevation old-growth forests in the Pacific Northwest held true for the higher-elevation forests of the Park. We used measurement...

A vegetation chronosequence spanning over 300 years was established in unconstrained reaches of the lower Queets River in Olympic National Park, Washington, USA, for an examination of riparian successional patterns. The Queets is an unconstrained, dynamic, mountain river located within a temperate rain forest environment. Ongoing chan- nel movement...

1. River valleys resemble dynamic mosaics, composed of patches which are natural, transient features of the land surface produced by the joint action of a river and successional processes over years to centuries. They simultaneously regulate and reflect the distribution of stream energy and exchanges of sediment, wood and particulate organic matter...

Currently, there are techniques that enable safe and repeated access to the forest canopy to study the 3-D structure of forest ecosystems and ecological processes occurring in the canopy. The 3-D distribution of tree crowns reflects how trees occupy space in the canopy to capture light resources and drives critical ecological processes such as stan...

Many aspects of tree physiology, epiphyte ecology, and stand-level forest dynamics can greatly benefit from whole-tree estimates of surface area, wood volume, and biomass. Surface area estimates are needed to determine carbon production for trees with photosynthetic bark and to estimate epiphyte habitat with tree crowns. Although most conifers carr...

We describe the three-dimensional structure of an old-growth Douglas-fir/western hemlock forest in the central Cascades of southern Washington, USA. We concentrate on the vertical distribution of foli-age, crowns, external surface area, wood biomass, and several components of canopy volume. In ad-dition, we estimate the spatial variation of some as...

We quantified stand-level structural diversity in eight stands of temperate coniferous forests that ranged in age from 50 to 950 years in the southern Washington Cascade Range. Stands were chosen based on the dominance, or former dominance in the case of the oldest stands, of Pseudotsuga menziesii. In addition, to avoid confusing patterns of struct...

Old-growth forests typically have complex structures, including heterogeneous spatial arrangements as well as a diversity of individual structures. Two aspects of this spatial complexity are discussed and illustrated: (1) vertical distribution of foliage, often apparent as multiple layers; and (2) horizontal heterogeneity, often evident as canopy g...

Forest managers need a comprehensive scientific understanding of natural stand development processes when designing silvicultural systems that integrate ecological and economic objectives, including a better appreciation of the nature of disturbance regimes and the biological legacies, such as live trees, snags, and logs, that they leave behind. Mo...

Ancient redwood trees (Sequoia sempervirens) often have complex crowns consisting of multiple, resprouted trunks. This study focuses on a single redwood tree, which is known as the Redwood Creek Giant, growing in Tall Trees Grove of Redwood National Park, CA. It is the sixteenth tallest (109.8 m) known living tree and the twentieth largest (744.7 m...

The effect of the spatial distribution of trees and foliage on understory conditions was examined in six tall old-growth forests along the Pacific Coast: two sites each in Washington, Oregon, and California. Detailed field measurements of crown parameters were collected on over 9000 trees encompassing over 14.5 ha in the stands. Crown parameters we...

In the coastal forests of northern California, redwood (Sequoia sempervirens) reigns supreme. Individual trees can exceed 112 m in height, and individual forest stands can have a biomass over 3,000 metric tons per hectare. Ancient redwoods often have complex crowns consisting of many reiterated trunks, some of which are larger than full-size trees...

Two 0.2-ha circular openings were created during fall 1990 in an old-growth Douglas-fir forest in the southern Washington Cascade Mountains. All trees >2 m tall were removed with care to minimize the disturbance to the understory and soil. A total of 1250 understory trees were monitored for growth and mortality over the next four years. Four main b...

In forests, the canopy is the locale of critical ecosystem processes such as photosynthesis and evapotranspiration, and it provides essential habitat for a highly diverse array of animals, plants, and other organisms. Despite its importance, the structure of the canopy as a whole has had little quantitative study because limited access makes quanti...

We describe the three-dimensional structure of an old-growth Douglas-fir/western hemlock forest in the central Cascades of southern Washington, USA. We concentrate on the vertical distribution of foliage, crowns, external surface area, wood biomass, and several components of canopy volume. In addition, we estimate the spatial variation of some aspe...