Temperate Rainforest Ecosystem Research Articles

Long-Term Patterns in Forest Soil CO2 Flux in a Pacific Northwest Temperate Rainforest

Soil CO2 efflux (Fs) plays an important role in forest carbon cycling yet estimates of Fs can remain unconstrained in many systems due to the difficulty in measuring Fs over long time scales in natural systems. It is important to quantify seasonal patterns in Fs through long-term datasets because individual years may show patterns that are not reflective of long-term averages. Additionally, determining predictability of net patterns in soil carbon flux based on environmental factors, such as moisture and temperature, is critical for appropriately modeling forest carbon flux. Ecosystems in moderate climates may have strong CO2 efflux even during winter, and so continuous quantification of annual variability is especially important. Here, we used a 2008–2023 dataset in a lowland temperate forest ecosystem to address two main questions: (1) What are the seasonal patterns in Fs in a highly productive temperate rainforest? (2) How is average Fs across our study area predicted by average coincident temperature, soil moisture and precipitation totals? Data showed clear seasonality where Fs values are higher in summer. We also find Fs across our measurement network was predicted by variation in abiotic factors, but the interaction between precipitation/moisture and temperature resulted in greater complexity. Specifically, in spring a relatively strong relationship between air temperature and Fs was present, while in summer the relationship between temperature and Fs was flat. Winter and autumn seasons showed weak positive relationships. Meanwhile, a negative relationship between precipitation and Fs was present in only some seasons because most precipitation falls outside the normal growing season in our study system. Our data help constrain estimates of soil CO2 fluxes in a temperate rainforest ecosystem at ~14–20 kg C ha−1 day−1 in summer and autumn, and 6.5–10.5 kg C ha−1 day−1 in winter and spring seasons. Together, estimates suggest this highly productive temperate rainforest has annual soil-to-atmosphere fluxes of CO2 that amount to greater than 4.5 Mg C ha−1 year−1. Sensitivity of such fluxes to regional climate change will depend on the balance of Fs determined by autotrophic phenological responses versus heterotrophic temperature and moisture sensitivity. Relatively strong seasonal variation coupled with comparatively weak responses to abiotic variables suggest Fs may be driven largely by seasonal trends in autotrophic respiration. Accordingly, plant and tree responses to climate may have a stronger effect on Fs in the context of climate change than temperature or moisture changes alone.

Oomycetes along a 120,000 year temperate rainforest ecosystem development chronosequence

Abstract The occurrence of plant-associated oomycetes in natural ecosystems and particularly during long-term ecosystem development is largely unknown. Using DNA sequencing, we investigated the frequency and host relationships of plant-root-associated oomycete communities along a 120 000 y glacial chronosequence, comprising site ages with rapid compositional change (“early succession”; 5–70 y old soil); relatively stable higher-diversity sites (“mature”, 280–12000 y); and ancient, nutrient-limited soils with declining plant biomass and stature (“retrogression”, 60 000, 120 000 y). Plant-associated oomycetes were frequent in early successional sites, occurring in 38–65% of plant roots, but rare (mean 3%) in all older ecosystems. Oomycete OTUs occurred non-randomly with plant host species, and were more frequent on those plant species that declined most strongly in abundance between ecosystem ages. While oomycetes were common in early succession, their absence in older sites suggests a limited role in later stages of ecosystem development.

The cascade impacts of climate change could threaten key ecological interactions

AbstractClimate change is triggering ecological responses all over the world as a result of frequent, prolonged droughts. It could also affect ecological interactions, particularly pollination and seed dispersal, which play a key role in plant reproduction. We used a tripartite interaction with a mistletoe, its pollinator and its disperser animals to gain insight into this issue. We studied flower and fruit production, and visitation rates during average (2012) and dry (2015) austral summers. Drought in our study area affected precipitation and soil water availability. Although pollinator visits did not significantly differ in these summers, during the dry summer flower and fruit production experienced an important decline, as did seed disperser visits. Also, mistletoe mortality increased from 12% in 2012 to 23% in 2015. This empirical evidence suggests that the cascade effects of climate change may indirectly be hindering ecological interactions in the Valdivian temperate rainforest ecosystem we studied. Long‐term research is essential to provide the knowledge necessary to understand how key ecological processes may be affected in a changing world.

Ecological legacies of fire detected using plot-level measurements and LiDAR in an old growth coastal temperate rainforest

Vegetation succession following fire disturbances has long been of interest in ecology, but the evolution of landscape pattern and structure following low-severity ground fires is poorly understood. In coastal temperate rainforest ecosystems historic fire disturbances are not well documented and time since the most recent fire is largely unknown. We sampled 6000 tree cores from 27 forest plots that burned 124 years ago and 11 plots with no recent history of fire (within the last 1000 years) to understand the legacies of fire on forest stand structure in a British Columbia high-latitude coastal temperate rainforest. We assessed the timing and spatial extent of historic fires with a 700 year fire history reconstruction built from fire scars, and applied light detection and ranging (LiDAR) to ground-truth plot-level measurements. We sampled an additional 32 plots with known fire histories to validate the ability of LiDAR to detect and characterize historic fire legacies. In total, we sampled 70 plots for stem density, stand structure, and stand composition. Trees in burned plots were significantly taller, and the mean stem density was less than half that of unburned plots despite 124 years since the most recent fire. LiDAR analyses had similar results and also showed that burned plots had lower canopy cover and greater canopy complexity. Field-based measurements are still required to resolve differences in community structure and composition in our temperate rainforest study area. However, LiDAR may be an important tool to bridge the spatial information offered by plot-level measurements to larger area characterizations in the future. Our comparative analyses provide an improved understanding of fire legacies and temperate rainforest structure, which increases our ability to detect fire disturbances in heterogeneous forests and is important for forest resource management and conservation.

The changing role of fire in conifer-dominated temperate rainforest through the last 14,000 years

Climate, fire and vegetation dynamics are often tightly coupled through time. Here, we use a 14 kyr sedimentary charcoal and pollen record from Lake Osborne, Tasmania, Australia, to explore how this relationship changes under varying climatic regimes within a temperate rainforest ecosystem. Superposed epoch analysis reveals a significant relationship between fire and vegetation change throughout the Holocene at our site. Our data indicates an initial resilience of the rainforest system to fire under a stable cool and humid climate regime between ca. 12–6 ka. In contrast, fires that occurred after 6 ka, under an increasingly variable climate regime wrought by the onset of the El Niño-Southern Oscillation (ENSO), resulted in a series of changes within the local rainforest vegetation that culminated in the replacement of rainforest by fire-promoted Eucalypt forest. We suggest that an increasingly variable ENSO-influenced climate regime inhibited rainforest recovery from fire because of slower growth, reduced fecundity and increased fire frequency, thus contributing to the eventual collapse of the rainforest system.

Ecological legacies of anthropogenic burning in a British Columbia coastal temperate rain forest

AbstractAimFew long‐term fire histories have been reconstructed in coastal temperate rain forests, and little is known regarding the spatial and temporal characteristics of lightning and human ignitions. We use a multidisciplinary approach to assess the impact, scale and ecological legacies of historic fires.LocationWe focus on perhumid temperate rain forests located on the central coast of British Columbia, Canada.MethodsWe reconstructed 700 years of temporal and spatial aspects of fire activity with 30 plots on Hecate Island using fire scars and forest‐stand establishment. We then conducted a paired study of 20 former indigenous habitation and control sites on 15 islands to relate fire activity to patterns of human settlement. We mapped 15 years of lightning strike densities and use mixed‐effects modelling to assess whether fire activity predicted the distribution and abundance of traditional plants.ResultsSixteen low‐ and mixed‐severity fires were recorded from 1376 to 1893. The abundance of traditional plants and the density of western redcedar trees were best predicted by the location of former habitation sites and shorter mean fire intervals. Lightning is too rare to explain the pattern of fire activity in the study area. No fire activity was detected after 1893, coinciding with the relocation of indigenous groups from the study area.Main conclusionsFire was strongly associated with former indigenous habitation sites during the periods of occupation. People likely utilized fire as a tool for resource management to influence the densities of specific plants by creating mosaics of vegetation in different stages of succession. By assessing the ecological impacts of historic fire events, we gain a better understanding of the abrupt changes that occurred in the 20th century. Our ability to understand present‐day temperate rain forest ecosystems may be compromised if we underestimate the role of humans in driving historic fire activity.

Geochemical and tectonic uplift controls on rock nitrogen inputs across terrestrial ecosystems

AbstractRock contains > 99% of Earth's reactive nitrogen (N), but questions remain over the direct importance of rock N weathering inputs to terrestrial biogeochemical cycling. Here we investigate the factors that regulate rock N abundance and develop a new model for quantifying rock N mobilization fluxes across desert to temperate rainforest ecosystems in California, USA. We analyzed the N content of 968 rock samples from 531 locations and compiled 178 cosmogenically derived denudation estimates from across the region to identify landscapes and ecosystems where rocks account for a significant fraction of terrestrial N inputs. Strong coherence between rock N content and geophysical factors, such as protolith, (i.e. parent rock), grain size, and thermal history, are observed. A spatial model that combines rock geochemistry with lithology and topography demonstrates that average rock N reservoirs range from 0.18 to 1.2 kg N m−3 (80 to 534 mg N kg−1) across the nine geomorphic provinces of California and estimates a rock N denudation flux of 20–92 Gg yr−1 across the entire study area (natural atmospheric inputs ~ 140 Gg yr−1). The model highlights regional differences in rock N mobilization and points to the Coast Ranges, Transverse Ranges, and the Klamath Mountains as regions where rock N could contribute meaningfully to ecosystem N cycling. Contrasting these data to global compilations suggests that our findings are broadly applicable beyond California and that the N abundance and variability in rock are well constrained across most of the Earth system.

Functional and environmental determinants of bark thickness in fire-free temperate rain forest communities.

In fire-prone ecosystems, variation in bark thickness among species and communities has been explained by fire frequency; thick bark is necessary to protect cambium from lethal temperatures. Elsewhere this investment is deemed unnecessary, and thin bark is thought to prevail. However, in rain forest ecosystems where fire is rare, bark thickness varies widely among species and communities, and the causes of this variation remain enigmatic. We tested for functional explanations of bark thickness variation in temperate rain forest species and communities. We measured bark thickness in 82 tree species throughout New Zealand temperate rain forests that historically have experienced little fire and applied two complementary analyses. First, we examined correlations between bark traits and leaf habit, and leaf and stem traits. Second, we calculated community-weighted mean (CWM) bark thickness for 272 plots distributed throughout New Zealand to identify the environments in which thicker-barked communities occur. Conifers had higher size-independent bark thickness than evergreen angiosperms. Species with thicker bark or higher bark allocation coefficients were not associated with "slow economic" plant traits. Across 272 forest plots, communities with thicker bark occurred on infertile soils, and communities with thicker bark and higher bark allocation coefficients occurred in cooler, drier climates. In non-fire-prone temperate rain forest ecosystems, investment in bark is driven by soil resources, cool minimum temperatures, and seasonal moisture stress. The role of these factors in fire-prone ecosystems warrants testing.

Icefield-to-Ocean Linkages across the Northern Pacific Coastal Temperate Rainforest Ecosystem

Icefield-to-Ocean Linkages across the Northern Pacific Coastal Temperate Rainforest Ecosystem

Fuel flammability and fire responses of juvenile canopy species in a temperate rainforest ecosystem

Historically, rainforests have been considered vulnerable to fire. Recent research, however, has shown that many rainforest species can survive fire by resisting burning and by resprouting and seeding post-fire. We investigated the response of a warm temperate rainforest community to fire by burning juveniles of the dominant canopy tree species (Doryphora sassafras, Syzygium smithii and Wollemia nobilis) and examining litter flammability in a controlled environment. The three species resprouted after the experimental burn, predominantly from buds on the stem that were below the soil surface. Higher fire temperatures resulted in reduced overall plant height and resprouting from buds lower on the stem. Increasing proportions of W. nobilis litter generated fires with higher intensities and fuel consumption compared with rainforest angiosperm litter. Moreover, fuel moisture content decreased with increasing W. nobilis litter proportions. Higher litter flammability may result in increased likelihood of fire ignition and fire severity near W. nobilis trees, which would negatively impact the juveniles of all three rainforest species. Alternatively, after lower-temperature fires (e.g. in rainforest angiosperm litter), W. nobilis may have an advantage over the other species because of faster-growing resprouts occurring higher on the stem.

Feral pigs in a temperate rainforest ecosystem: disturbance and ecological impacts

Feral pigs (Sus scrofa) are a widespread invasive species, and cause biotic disturbance. This study evaluated the impacts associated with ground disturbance by feral pigs in the North Island of New Zealand. Exclosure cages were erected over feral pig-disturbed ground and visually undisturbed ground (the latter as controls). Buried resin bags and litter bags were located in these plots to examine differences in soil nutrients and decomposition rates and seedling/sapling recruitment (abundance, species composition and richness) was monitored over 21 months. No difference was found in the litter decomposition between the disturbed and visually undisturbed plots. Significantly more nitrate (NO3-N/NO2-N) was found in the disturbed exclosures. Seedling density was not significantly affected by feral pig disturbance. However, seedling/sapling species richness was lower in disturbed areas. Species composition changes occurred at disturbed sites with species increasing and decreasing in density after feral pig disturbance. However, no pattern was observed between species that were negatively affected by feral pig disturbance. This study shows that feral pig disturbance affects vegetation through direct removal, but also indirectly through increased nitrate, potentially leading to seedling and sapling species composition changes. Feral pigs are known to return to previously disturbed areas to re-disturb. These areas may remain in a re-disturbed state if not protected, and through continued disturbance and increased nitrate, ecosystem changes may occur, especially in characteristically nutrient poor environments.

Response of an ecological indicator to landscape composition and structure: Implications for functional units of temperate rainforest ecosystems

We evaluated the northern flying squirrel (Glaucomys sabrinus griseifrons), a known associate of key habitat features and processes of old-growth forest, for its capacity as a broad-scale ecological indicator of temperate rainforest ecosystem condition in southeastern Alaska, USA. We utilized a spatially explicit, resource-selection function to evaluate its distribution relative to landscape composition and structure at local (within home-range) and broad (home-range selection) spatial scales, followed by a moving-window analysis to model patch occupancy across this landscape. We found strong support for the influence of type, size, and compositional elements: large, old-growth patches were selected at both spatial scales, and regenerating forest patches ≤40yrs old were selected against at the broader scale. More importantly, we found that occupancy was related to critical thresholds in composition: patches required ≥73% old-growth forest cover or a minimum total area of 73ha of old-growth forest to be occupied by flying squirrels. A non-uniform pattern of selection for patches with higher structural connectivity at the local scale, but not at the broader scale, was likely a result of the “empty forest” phenomenon, in which remnant patches were inaccessible in this fragmented landscape. These results are consistent with recent studies of this and related species and suggest that occurrence of northern flying squirrels in southeastern Alaska is influenced by a number of landscape structure and compositional variables that relate critically to late-seral forest conditions. These findings shed new light on the utility of this species as an ecological indicator and its functional relevance to the resilience of fragmented forest ecosystems.

Variability in the Southern Annular Mode determines wildfire activity in Patagonia

[1] Under the current global warming trend, wildfire activity is expected to decrease in biomass-limited fire regimes but increase in drought-limited fire regimes with abundant biomass. We examined the effects of the Southern Annular Mode (SAM) on interannual variability in wildfire activity in xeric woodland and temperate rainforest ecosystems across a latitudinal range of 10° in temperate southwestern South America (SSA). Based on 42 fire history sites based on nearly 600 fire-scarred trees (the largest available dataset of annually resolved tree-ring records of fire activity in the Southern Hemisphere), we show that years of widespread fire in both xeric woodland and rainforest ecosystems are associated with positive departures of SAM. The association of positive SAM with increased fire activity is explained by the teleconnection of SAM to spring drought across most of SSA. During the late 20th century, only the rainforest ecosystem shows a strong increase in fire activity, which is consistent both with upward trends in SAM and with warming conditions. We attribute the lack of increased burning in the xeric woodland environment to socioeconomic factors and fire behavior (low severity) that facilitate more effective fire suppression in the xeric woodland habitat. Given projected future increases in SAM and the associated warm-dry trend, wildfire activity in much of SSA is likely to increase during the 21st century.

Seasonal and annual throughfall and stemflow in Andean temperate rainforests

AbstractThe partitioning of gross rainfall into throughfall, stemflow, and interception loss and their relationships with forest structure was studied for a period of four years (October 2002–September 2006) and two years (October 2005–September 2007) in seven experimental catchments of temperate rainforest ecosystems located in the Andes of south‐central Chile (39°37′S, 600–925 m a.s.l.). The amount of throughfall, stemflow, and interception loss was correlated with forest structure characteristics such as basal area, canopy cover, mean quadratic diameter (MQD), and tree species characteristics in evergreen and deciduous forests. Annual rainfall ranged from 4061 to 5308 mm at 815 m a.s.l. and from 3453 to 4660 mm at 714 m a.s.l. Throughfall ranged from 64 to 89% of gross rainfall. Stemflow contributed 0·3–3·4% of net precipitation. Interception losses ranged from 11 to 36% of gross rainfall and depended on the amount of rainfall and characteristics as well as on forest structure, particularly the MQD. For evergreen forests, strong correlations were found between stemflow per tree and tree characteristics such as diameter at breast height (R2 = 0·92, P < 0·01) and crown projection area (R2 = 0·65, P < 0·01). Stemflow per tree was also significantly correlated with epiphyte cover of trunks in the old‐growth evergreen forests (R2 = 0·29, P < 0·05). The difference in the proportion of throughfall and interception loss among stands was significant only during winter. The reported relationships between rainfall partitioning and forest structure and composition provide valuable information for management practices, which aimed at producing other ecosystem services in addition to timber in native rainforests of southern Chile. Copyright © 2010 John Wiley & Sons, Ltd.

GIS analysis of spatial and temporal patterns of human-caused wildfires in the temperate rain forest of Vancouver Island, Canada

This study examines the spatial and temporal pattern of human-caused wildfires (HCWs) in the temperate rainforest of Vancouver Island (VI). A Geographic Information System was used to locate HCWs that occurred on VI from 1950 through 1992, to divide VI into 1 km×1 km grid cells, and to determine for each grid cell the climate and distances to various human-built infrastructures. Logistic regression was used to build a predictive model of the probability of HCW occurrence in each of the grid cells, using climate and distances as predictor variables. A total of 6329 wildfires occurred on VI over the 43 years study period, and 2747 of the grid cells contained at least one fire. The probability of a grid cell burning was positively correlated with summer temperature, and negatively correlated with precipitation and distances to municipalities, campgrounds, dirt roads, railroads and paved roads. Grid cells were grouped into five classes of HCW probability: <20, 20–39, 40–59, 60–79, >80%. The lower the probability of HCW occurrence, the lower the number of fires per km 2 per year, the longer the fire cycle in years, and the larger the mean fire size. The unexpected larger mean fire size in areas with low HCW probability is due to logging fires being the most common type there, and logging fires being significantly larger than other types on all portions of VI. Where the HCW probability was highest, recreation and miscellaneous fires were most common, and these types of fires tended to be significantly smaller. The annual number and annual area burned by HCWs on VI has been decreasing. These decreases have occurred primarily in the areas that have a high HCW probability, while increases have occurred where the HCW probability is low. These results indicate that HCWs are a significant part of the temperate rainforest ecosystem and that the spatial variation in their occurrence could be used to delimit fire management zones.

Plant SuccessionPlant Succession; An Analysis of the Development of Vegetation.F. E. Clements

Previous articleNext article FreeCurrent LiteraturePlant Succession Plant Succession; An Analysis of the Development of Vegetation. F. E. Clements Henry C. CowlesHenry C. Cowles Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 68, Number 6Dec., 1919 Article DOIhttps://doi.org/10.1086/332587 Views: 173 Citations: 5Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Ian A. Dickie, Angela M. Wakelin, Laura B. Martínez-García, Sarah J. Richardson, Andreas Makiola, Jason M. Tylianakis Oomycetes along a 120,000 year temperate rainforest ecosystem development chronosequence, Fungal Ecology 39 (Jun 2019): 192–200.https://doi.org/10.1016/j.funeco.2019.02.007Frank N. Egerton History of Ecological Sciences, Part 54: Succession, Community, and Continuum, Bulletin of the Ecological Society of America 96, no.33 (Jul 2015): 426–474.https://doi.org/10.1890/0012-9623-96.3.426Frank N. Egerton History of Ecological Sciences, Part 48: Formalizing Plant Ecology, about 1870 to mid-1920s, Bulletin of the Ecological Society of America 94, no.44 (Oct 2013): 341–378.https://doi.org/10.1890/0012-9623-94.4.341 References, (Jul 2012): 195–205.https://doi.org/10.1002/9781118290927.refsEthan D. Churchill, Herbert C. Hanson The concept of climax in arctic and alpine vegetation, The Botanical Review 24, no.2-32-3 (Feb 1958): 127–191.https://doi.org/10.1007/BF02872544