Long-term spatial dynamics in an old-growth deciduous forest

In 1926, 1976, and 1986 stems (≥ 10 cm diameter at 1.37 m (dbh)) were measured and mapped in a 4 ha interior study area on the Davis-Purdue Research Forest in east-central Indiana. Spatial pattern type was determined using the Clark and Evans's index, and Ripley's L function. The G function was used to examine spatial dispersion at intertree distances (< 20 m). Spatial pattern of combined size classes shifted from weakly non-random in 1926 to uniform in 1976 and 1986. Neighborhood density was depressed for 2 m in 1976 and 5 m in 1986. Peak in neighborhood density at 6 m suggested trees were spaced 6 m apart. Subcanopy (10–25 cm dbh) tree spatial pattern shifted from aggregated in 1926 to uniform in 1976. The spatial pattern of canopy (> 25 dbh) trees was uniform between 1926 and 1986. Density-dependent mortality and ingrowth processes are maintaining uniform spatial distributions. Initial neighborhood tree distribution was higher around trees which died in the periods 1926–1976 and 1976–1986 than for contemporary survivors, i.e. trees which survived this period had fewer neighboring trees within 6 m at the beginning of the period than did trees which died. The higher initial neighborhood densities around mortality trees than survivors supports density-dependent mortality. Ingrowth was inhibited in a 6 m zone proximite to established trees for both the 1926–1976 and 1976–1986 periods.     

Twenty-three years of stand dynamics in an old-growth Chamaecyparis forest in central Japan

Structures and dynamics of old-growth coniferous stands are affected by several types of disturbances including typhoons. We report the forest dynamics of four old-growth Chamaecyparis stands in central Japan that differ in the disturbance history of typhoons over a period of 23 years. The stem number, basal area and mortality were examined. In a predominant stand of C. obtusa (Sieb. et Zucc.) Endl., 24 % of the C. obtusa canopy trees died, mainly as a result of the severe damage of a strong typhoon that caused a single tree-fall gap and the following gap enlargements. In this stand, the total basal area decreased to 76.5 % of the initial value, although the mortality declined in recent years. In contrast, the other three stands decreased only slightly in the stem numbers (0.0–5.6 %) and increased in the basal areas of C. obtusa canopy trees. It is confirmed that the stand-level ingrowths of 300-year-old C. obtusa canopy trees could contribute to the increase in the stock of each stand. Our results support an idea that the dynamics of old-growth Chamaecyparis forests were greatly affected by typhoons. The stand structures will be gradually changed (with the processes of gap dynamics) and C. obtusa will continue to be dominant, potentially over hundreds of years.     

Flux partitioning in an old-growth forest: seasonal and interannual dynamics

Turbulent fluxes of carbon, water and energy were measured at the Wind River Canopy Crane, Washington, USA from 1999 to 2004 with eddy-covariance instrumentation above (67 m) and below (2.5 m) the forest canopy. Here we present the decomposition of net ecosystem exchange of carbon (NEE) into gross primary productivity (GPP), ecosystem respiration (R(eco)) and tree canopy net CO(2) exchange (DeltaC) for an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)-western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest. Significant amounts of carbon were recycled within the canopy because carbon flux measured at the below-canopy level was always upward. Maximum fluxes reached 4-6 micromol m(-2) s(-1) of CO(2) into the canopy air space during the summer months, often equaling the net downward fluxes measured at the above-canopy level. Ecosystem respiration rates deviated from the expected exponential relationship with temperature during the summer months. An empirical ecosystem stress term was derived from soil water content and understory flux data and was added to the R(eco) model to account for attenuated respiration during the summer drought. This attenuation term was not needed in 1999, a wet La Ni?a year. Years in which climate approximated the historical mean, were within the normal range in both NEE and R(eco), but enhanced or suppressed R(eco) had a significant influence on the carbon balance of the entire stand. In years with low respiration the forest acts as a strong carbon sink (-217 g C m(-2) year(-1)), whereas years in which respiration is high can turn the ecosystem into a weak to moderate carbon source (+100 g C m(-2) year(-1)).     

Long-term spatial dynamics of Acer saccharum during a population explosion in an old-growth remnant forest in Illinois

Species richness and evenness have greatly declined in oak–hickory forests in the central hardwood region in the U.S.A. in the past 100 years due to the rapid population growth of Acer saccharum. This study used a 50-year record of spatial dynamics to examine how demographic processes, particularly recruitment, may have contributed to this increase in an old-growth forest remnant, Brownfield Woods, Urbana, Illinois, U.S.A. The impact of canopy disturbance, including the outbreak of Dutch elm disease, on this increase was also evaluated. Historical maps of trees (≥7.6 cm DBH) from 1951, 1988, and 2001 in a 180 m × 280 m area were used to develop a series of univariate Ripley's L(d) functions to study changes in spatial patterns of three size classes of A. saccharum over time. Bivariate Ripley's L(d) functions were also utilized to evaluate spatial associations between recruitment and canopy disturbance. Our results indicated that A. saccharum was aggregated at most spatial scales up to 80 m during 1951–2001. Such aggregation arose mainly from small individuals. Furthermore, newly recruited individuals were aggregated at multiple spatial scales, and were significantly associated with canopy disturbance in general, as well as gaps created by Ulmus trees killed by Dutch elm disease. The aggregation of the 1951 initial group of small individuals changed via mortality to a random distribution over time. The results indicate that tree deaths caused by disturbances of different scales and types were the main cause of increased recruitment of A. saccharum in Brownfield Woods. The occurrence of Dutch elm disease further accelerated its population increase. This study demonstrated a direct spatial link between recruitment of A. saccharum and disturbance, and provided a long-term case study of a population explosion.     

Spatial patterns in different forest development stages of an intact old-growth Oriental beech forest in the Caspian region of Iran

Spatial patterns of trees are important structural characteristics that can provide insights into forest dynamics and may be related to the development stages of forests. The spatial patterns of three development stages (i.e., initial, optimal, and decay) of an intact old-growth beech (Fagus orientalis Lipsky) forest in the Caspian region of Iran were quantified within one-hectare permanent plots. All trees with a diameter at breast height of more than 7.5?cm were measured, stem-mapped, and then assigned to one of four diameter size classes (small, medium, large, and extra-large timbers). Spatial patterns of all trees and spatial associations among tree size classes were analyzed using Ripley’s K-function, and the spatial dependence of tree diameters was analyzed using variograms. Results showed that trees in the small size class exhibited an aggregated distribution in every development stage, which matched the overall spatial pattern of all trees in each stage. However, the degree of aggregation of all trees as well as association patterns among the size classes differed among the three development stages. Further, the average spatial dependence of tree diameters was 24, 14, and 19?m in the initial, optimal, and decay stages, respectively. Differences in spatial patterns among the development stages in this beech old-growth forest are consistent with the gap-dynamics paradigm and likely reflect different canopy disturbance events coupled with associated regeneration, release, and competition processes (e.g., shade-tolerance characteristics, seed dispersal limitation, and intraspecific competition).     

Crown plasticity and neighborhood interactions of European beech (Fagus sylvatica L.) in an old-growth forest

Competition for canopy space is a process of major importance in forest dynamics. Although virgin and old-growth European beech (Fagus sylvatica L.) forests in Europe have been studied for many years, there are to date no studies of individual-tree crown plasticity and the way this is influenced by local neighborhood interactions in these forests. In this study, we analyzed crown plasticity and local neighborhood interactions of individual trees in the upper canopy of the old-growth beech forests of Serrahn, northeast Germany. In a 2.8-ha sample plot, we measured crown radii of all upper canopy trees and analyzed the direction and extent of crown asymmetry. Size, relative position, and distance of neighboring trees were used to construct vectors of neighborhood asymmetry within different distances from target trees. The crowns of beech trees showed strong morphological plasticity. Mean absolute and relative displacement of crown centers from the stem base were 1.95 m and 0.37, respectively. Circular–circular rank correlation coefficients between the direction of crown displacement and the direction of neighborhood pressure showed that trees strongly positioned their crowns away from local neighbors. Highest correlation coefficients were obtained when basal area and relative position of neighboring trees within a radial distance of 12 m were considered. Clark and Evans index and Ripley’s K-function showed that crowns were more regularly distributed than stems. Projected canopy cover was about 10% higher than canopy cover with simulated circular crowns. We conclude that the crowns of older beech trees have a high ability to plastically respond to changes in the local canopy conditions, enabling very effective exploitation of canopy space.     

Disturbance history and dynamics of an old-growth mixed species mountain forest in the Slovenian Alps

A long history of human presence in the Alps has made studies of natural forest structure, composition, and disturbance processes difficult. In the Slovenian Alps, we identified a mixed European beech (Fagus sylvatica L.)-silver fir (Abies alba Mill.)-Norway spruce (Picea abies (L.) Karst.) stand with old-growth characteristics that escaped past cutting. We reconstructed the dynamics of the stand using a combination of stand and age structure analyses, dendroecological evidence of past canopy disturbance, and historical evidence of past human activities. The disturbance reconstruction revealed a stand-scale disturbance in the 1850s. Based on the presence of pit-and-mound topography throughout much of the stand and the absence of logging activities found in historical records, we assume this event was caused by strong winds. The current structure and composition of the stand are largely a result of this event. Post-disturbance forest development was dominated by the release of shade tolerant regeneration, especially F. sylvatica. The windthrow also created appropriate conditions (i.e. increased light and exposed mineral soil) for recruitment of less shade tolerant species, including larch (Larix decidua Mill.) and maple (Acer pseudoplatanus L.). The results suggest that periodic, intermediate severity wind disturbances, similar to the event documented here, may have had an important influence on pre-settlement forest dynamics in mixed mountain forests of the Alps, and add to the limited available information regarding the historic range of natural variability of disturbance processes. This information may be useful for forest management that attempts to emulate natural processes.     

Local spatial pattern in the occurrence of two congeneric wood-decaying fungi in an old-growth boreal forest

Abstract

This paper characterizes spatial patterns in the occurrence of two congeneric wood-decaying fungi (Aphyllophorales: Polyporaceae) in an old-growth boreal forest in eastern Finland. The spatial patterns are used to evaluate indirectly the short-distance dispersal ability of the species. Fomitopsis rosea is a specialist on Picea abies occurring mainly in forests with large amounts of dead wood, whereas Fomitopsis pinicola is a substrate generalist and also abundant in managed forests. Within a forest reserve, a 25 ha study area was divided into 25 m×25 m grid (n=400), and all dead trees and fruiting bodies of the two polypore species were recorded. Spatial patterns were analysed with Spatial Analysis by Distance IndicEs methodology (SADIE). Downed spruce logs were highly aggregated within the study area. After this distribution was accounted for, the spatial pattern of F. pinicola and F. rosea on logs was random. The lack of spatial aggregation suggests that within old-growth forest stands dispersal of the two fungal species is not a limiting factor for their occurrence.     

Temporal dynamics and spatial variations of forest vegetation carbon stock in Liaoning Province,China

There are many uncertainties in the estimation of forest car- bon sequestration in China, especially in Liaoning Province where vari- ous forest inventory data have not been fully utilized. By using forest inventory data, we estimated forest vegetation carbon stock of Liaoning Province between 1993 and 2005. Results showed that forest biomass carbon stock increased from 68.91 Tg C in 1993 to 97.51 Tg C in 2005, whereas mean carbon density increased from 18.48 Mg·ha -1 C to 22.33 Mg·ha -1 C. The carbon stora...     

Effects of undisturbed canopy structure on population structure and species coexistence in an old-growth subalpine forest in central Japan

We investigated structural and compositional characteristics of an old-growth subalpine forest in central Japan, to ascertain forest dynamics and species coexistence. The forest appeared to have been fairly-undisturbed, at least during several recent decades, judging from the maximum occupancy of space by living canopy trees and an unchanged canopy structure between pre- and post-mortality phase. This stable forest showed minimum-scale dynamics that occurred primarily at a single-tree scale. Within this forest, the dominant species were Abies mariesii, A. veitchii and Picea jezoensis var. hondoensis. The two Abies species were abundant and showed advance regeneration, resulting from their high shade-tolerance. On the other hand, Picea showed the greatest basal area, in spite of its lower density. Picea showed steeper initial height-diameter allometric slopes, suggesting that its understorey saplings could increase height more rapidly under sunny conditions. Picea regenerates, given the opportunity of larger disturbances, as approximately even-aged cohorts, and then escapes competition from other shade-tolerant species by attaining the uppermost part of the canopy, resulting from rapid height growth of sapling, longer longevity and emergent attainable height. However, beneath the undisturbed canopy of this forest, in spite of its many seedlings, Picea entirely lacked regenerating individuals, suggesting that its regeneration is in a fairly-limited stage. This suggests that within the undisturbed forest, a demographic trait of Picea, in which the lower mortality of its canopy trees can compensate for its lower recruitment, is not enough to explain its stable coexistence with shade-tolerant Abies spp. Thus, not only the demographic trait, but also the spatial/temporal disturbance magnitude is important for an explanation of the coexistence of Picea with Abies. Consequently, it seems that not only equilibrium process, such as species differences in life-history traits, but also non-equilibrium process, such as disturbances, is crucial for their coexistence in this subalpine forest in central Japan.     

Windthrow and salvage logging in an old-growth hemlock-northern hardwoods forest

Although the initial response to salvage (also known as, post-disturbance or sanitary) logging is known to vary among system components, little is known about longer term forest recovery. We examine forest overstory, understory, soil, and microtopographic response 25 years after a 1977 severe wind disturbance on the Flambeau River State Forest in Wisconsin, USA, a portion of which was salvage logged. Within this former old-growth hemlock-northern hardwoods forest, tree dominance has shifted from Eastern hemlock (Tsuga canadensis) to broad-leaf deciduous species (Ulmus americana, Acer saccharum, Tilia americana, Populus tremuloides, and Betula alleghaniensis) in both the salvaged and unsalvaged areas. While the biological legacies of pre-disturbance seedlings, saplings, and mature trees were initially more abundant in the unsalvaged area, regeneration through root suckers and stump sprouts was common in both areas. After 25 years, tree basal area, sapling density, shrub layer density, and seedling cover had converged between unsalvaged and salvaged areas. In contrast, understory herb communities differed between salvaged and unsalvaged forest, with salvaged forest containing significantly higher understory herb richness and cover, and greater dominance of species benefiting from disturbance, especially Solidago species. Soil bulk density, pH, organic carbon content, and organic nitrogen content were also significantly higher in the salvaged area. The structural legacy of tip-up microtopography remains more pronounced in the unsalvaged area, with significantly taller tip-up mounds and deeper pits. Mosses and some forest herbs, including Athyrium filix-femina and Hydrophyllum virginianum, showed strong positive responses to this tip-up microrelief, highlighting the importance of these structural legacies for understory biodiversity. In sum, although the pathways of recovery differed, this forest appeared to be as resilient to the compound disturbances of windthrow plus salvage logging as to wind disturbance alone, by most vegetative measures.     

Fine-scale species co-occurrence patterns in an old-growth temperate forest

The pattern of species co-occurrence is instrumental for understanding community assembly rules. In this paper, we analyzed the co-occurrence of tree species in a 25-ha old-growth temperate forest plot in Northeastern China. The analysis was conducted at seven scales from 5 m × 5 m up to 100 m × 100 m in order to determine the patterns of co-occurrence at different spatial scales. Our analyses were conducted for all species, species with larger abundances, species with larger sizes, and five phylogenetic-based species groups. Our results showed that at smaller scales, the co-occurrence patterns of all species, species with larger abundances, and species with larger sizes were significantly higher than expected by chance, suggesting that strong interspecies competition exists in the community. At larger scales, there was no significant difference compared to randomized matrices. The result indicated that plant assembly rules are only found at small spatial scales. However, when co-occurrence metrics were restricted to phylogenetic groups, we could not find any clear evidence of interspecific competition within these groups. In conclusion, we found that competition is an important assembly rule at small scales in governing tree communities of our temperate forest, although it is not the only process involved. The importance of other processes should also be taken into account to explain species co-occurrence patterns.     

Composition, structure and dynamics of Dysart Woods, an old-growth mixed mesophytic forest of southeastern Ohio

Dysart Woods is a 23 ha old-growth remnant of mixed mesophytic vegetation located in southeastern Ohio, USA. A designation of mixed mesophytic for this forest has historically been difficult, in part due to the abundance of white oak (Quercus alba); however, the dominance of a variety of other hardwoods prevents a simple oak forest designation. Using two 0.35 ha plots on opposing north- and south-facing slopes, we describe the structure and composition of the overstory, understory, and soils, 30 years after their first examination. In 1970, the woods was dominated by beech (Fagus grandifolia), white oak, and sugar maple (Acer saccharum) — historically, the three most abundant species in this region. At that time, white oak was only present in the largest size classes, was not regenerating, and was predicted to decline in importance through succession. These patterns continue today suggesting that inferences made via overstory–understory relations in regards to forest succession are relatively robust over this time period. Beech and maple have increased in importance; white oak has decreased in importance due to mortality in the larger size classes and decreasing density due to regeneration failure. Coarse woody debris distributions correlated strongly with living stem species’ composition and structure implying an equilibrium balance. CWD volume and frequency were dominated by Quercus spp. A detailed analysis of forest health showed that all oak species were in severe decline. The oaks are in a disease decline spiral affiliated with a variety of pre-disposing and inciting factors which include their advanced age (>300 years), their large size (> 100 cm DBH), topography, chronic air pollution, drought, and Armillaria root rot fungus. Ca:Al molar ratios in the soil are also extremely low (<1.0) and may be having an additional detrimental effect. All other canopy species appear to be healthy. One of the unusual features of this woods is its relatively diverse and high coverage (up to 90%) understory layer. The herbaceous community was sampled throughout the growing season and found to be markedly dissimilar among sample times and habitat productivity (aspect, soil quality, and light). The role of these factors has not been as well studied for herb communities as it has for tree communities. There appears to be a relatively strong linkage between the overstory regeneration and understory coverage. While a variety of woody seedlings were discovered, most were of shade tolerant species. Only a few small seedlings of white oak were discovered, with none advancing past 30 cm in height, indicating strong competition in the understory. Furthermore, this small remnant forest patch is surrounded by an agricultural and second-growth forest matrix with many non-indigenous plants — none of which have been able to enter the woods, suggesting strong equilibrium stability of these old-growth patches. The hardwood forests of the hills region has been heavily impacted by various human cultures for thousands of years. Dendrochronological analysis of a full basal slab cut from a wind-thrown white oak revealed a fairly active period of fire following European settlement. A lack of fire during the early 1600s to mid 1700s suggests that pre-Anglo fire frequency may have been negligible. There is clearly a continued role for the preservation and study of these old-growth remnants. They remain integrally important as we attempt to understand and better manage our remaining anthropogenically disturbed landscape.     

Gap dynamics in the Western Carpathian mixed beech old-growth forests affected by spruce bark beetle outbreak

Understanding how species-specific disturbances affect the dynamics of mixed forests is becoming increasingly important due to rapidly changing disturbance regimes. This study estimated the effect of Norway spruce (Picea abies (L.) Karst.) mortality on the disturbance processes in two mixed beech stands of the Western Carpathians that were affected by a bark beetle outbreak. We evaluated the size distribution, fraction of canopy and expanded gaps, the characteristics of gapmakers and the contribution of different species to gap size. The measured canopy gap fraction was <5%, and most canopy gaps were small (<100 m²). Spruce was the most abundant gapmaker, and its share among gapmakers was 3–6 times higher than its share in the canopy. We found that the increase in spruce mortality due to the outbreak resulted in a fine-scale mortality pattern. However, spruce gapmakers did not contribute much to gap area size, as shown by a weak correlation between the number of spruce gapmakers and the area of expanded gaps. Diameter distribution of living versus recently dead trees showed that beech mortality occurred disproportionately in large size classes. However, dead spruce trees were equally frequent in all diameter classes, which means beetles did not exclusively attack larger trees in these stands during the outbreak. We conclude that spruce mortality may have influenced successional processes by giving a competitive advantage to two other species that were not affected by the outbreak, provided that a high deer browsing intensity does not hinder the regeneration of new seedlings.

     

Age structure and spatial pattern of old-growth korean pine forest in Xiaoxing’anling Mountain

Spatial pattern of trees, basal stem increment and height were examined in a 5.0 ha mixed deciduous/Pinus koraiensis forest from October in 1984 to May in 1987. Conclusions are as following: 1. Analysis of the age-structure of the korcan pine forest shows that it is different from general steady-state forest type. The lack of saplings and individuals in small-diameter class clearly indicates that regeneration is not continuous. Continuous regeneration depends on thinning of the canopy to form a gap. Similar-aged korcan pine sccdings grow in these gaps. 2. The horizontal structure of the korcan pine is a mosaic of more or less even-aged groups of trees. The mosaic is a result of korcan pine by regeneration strategy. The aggregations of korcan pine of different ages overlaps to form a continuous population generation. As a results, the population is maintained in steady state.     

Canopy gaps in an old-growth fir-beech forest remnant of Western Carpathians

The old-growth forest remnants of Western Carpathians provide a unique possibility to study the disturbance regimes of forest ecosystems without human influence. This study investigated the gap dynamics in beech-dominated old-growth forest Badínsky prales in Central Slovakia. Considering the decline of silver fir in last decades, the study analyzed the main characteristics of disturbance regime with the emphasis on the role of fir. On a 5-ha research plot, the dominant tree species was beech, the proportion of fir reached about 10%. However, a significantly higher proportion of fir (>30%) was observed in the coarse woody debris. In total, 45 canopy openings were recorded. Canopy gaps and expanded gaps covered 11.3 and 37.9% of the forest area, respectively. Despite the highest frequency of small gaps <100 m², their proportion of the overall gap area reached only 20%, what suggests the important role of intermediate and large gaps in the gap dynamics as well. The analysis of gapmakers’ crown projections confirmed a rather low contribution of fir (14.6%) to the gap formation despite its relatively intensive mortality. A high variability of the next generation age between the gaps (6–44 years) was recorded what suggests a large temporal variation of the disturbance events. The lateral expansion of adjacent trees was found to be the determining process for the closure of small canopy openings. The intermediate and large gaps are more likely closed by the height growth of natural regeneration and understory trees that are present on the majority of the area.     

Thirty years of gap dynamics in a central european beech forest reserve

Investigation of gap characteristics and tree regeneration patternsis central for our understanding of forest dynamics. By integratingaerial photograph analyses and ground surveys, we provide astudy of long-term canopy gap dynamics and tree regenerationpatterns in a Hungarian beech forest reserve. We found (1) thatin spite of the overall increase of gap area during the investigated30-years (from 2.5 to 7.7 per cent), total gap area and averagegap size (40–93 m²) were remarkably similar to those foundin other temperate and tropical forests, (2) if the fate ofindividual gaps was followed, two to three times more intensivecanopy dynamics (gap creation, closure and expansion) couldbe recognized than simple change of gap area indicated, and(3) average seedling density was considered to be sufficientfor natural regeneration. However, it was apparent that recentincreased deer browsing had prevented establishment of youngertrees of 1–2 m in height, as taller saplings were recordedonly in old gaps. Our results not only provide useful informationon forest dynamics but can also contribute to understandingthe potential roles that small forest reserves can play in providingessential reference data for nature-based forest managementof this forest type.     

A dendroecological reconstruction of disturbance in an old-growth Fagus-Abies forest in Slovenia

The scarcity of large old-growth forests has made it challenging to quantify disturbance regimes in Central Europe. The objective of this study was to reconstruct the history of disturbance in an old-growth Fagus-Abies forest reserve in Slovenia using a dendroecological approach. We extracted cores from canopy trees blown down during a recent windthrow event and identified growth releases in the tree-ring series using boundary-line release criteria to infer past disturbances. A total of 216 release events were identified from 88 trees. Between 1790 and 1990, moderate, asynchronous release events were present in nearly every decade of the disturbance chronology, suggesting a history of frequent, low severity disturbance. However, there were also peaks in the chronology corresponding to synchronous release events in a large proportion of the trees, suggesting that less frequent, intermediate severity disturbance events played an important role in forest development. These events are likely caused from wind damage associated with local thunderstorms, which seem to occur at intervals between 20–80 years on the study site. Thus, in addition to the small-scale gap phase processes operating in the forest, the results indicate that periodic intermediate severity disturbance events are an important component of the disturbance regime in mountain forests of Central Europe.     

Species-specific partitioning of soil water resources in an old-growth Douglas-fir-western hemlock forest

Although tree- and stand-level estimates of forest water use are increasingly common, relatively little is known about partitioning of soil water resources among co-occurring tree species. We studied seasonal courses of soil water utilization in a 450-year-old Pseudotsuga menziesii (Mirb.) Franco-Tsuga heterophylla (Raf.) Sarg. forest in southwestern Washington State. Soil volumetric water content (theta) was continuously monitored with frequency domain capacitance sensors installed at eight depths from 0.2 to 2 m at four locations in the vicinity of each species. Vertical profiles of root distribution and seasonal and daily courses of hydraulic redistribution (HR), sap flow and tree water status were also measured. Mean root area in the upper 60 cm of soil was significantly greater in the vicinity of T. heterophylla trees. However, seasonal water extraction on a root area basis was significantly greater near P. menziesii trees at all depths between 15 and 65 cm, leading to significantly lower water storage in the upper 65 cm of soil near P. menziesii trees at the end of the summer dry season. Greater apparent efficiency of P. menziesii roots at extracting soil water was attributable to a greater driving force for water uptake rather than to differences in root hydraulic properties between the species. The dependence of HR on theta was similar in soil near individuals of both species, but seasonal maximum rates of HR were greater in soil near P. menziesii because minimum values of theta were lower, implying a steeper water potential gradient between the upper and lower soil that acted as a driving force for water efflux from shallow roots. The results provide information on functional traits relevant for understanding the ecological distributions of these species and have implications for spatial variability of processes such as soil respiration and nutrient cycling.