Coastal Temperate Rainforest Research Articles

Advancing an integrated understanding of land–ocean connections in shaping the marine ecosystems of coastal temperate rainforest ecoregions

AbstractLand and ocean ecosystems are strongly connected and mutually interactive. As climate changes and other anthropogenic stressors intensify, the complex pathways that link these systems will strengthen or weaken in ways that are currently beyond reliable prediction. In this review we offer a framework of land–ocean couplings and their role in shaping marine ecosystems in coastal temperate rainforest (CTR) ecoregions, where high freshwater and materials flux result in particularly strong land–ocean connections. Using the largest contiguous expanse of CTR on Earth—the Northeast Pacific CTR (NPCTR)—as a case study, we integrate current understanding of the spatial and temporal scales of interacting processes across the land–ocean continuum, and examine how these processes structure and are defining features of marine ecosystems from nearshore to offshore domains. We look ahead to the potential effects of climate and other anthropogenic changes on the coupled land–ocean meta‐ecosystem. Finally, we review key data gaps and provide research recommendations for an integrated, transdisciplinary approach with the intent to guide future evaluations of and management recommendations for ongoing impacts to marine ecosystems of the NPCTR and other CTRs globally. In the light of extreme events including heatwaves, fire, and flooding, which are occurring almost annually, this integrative agenda is not only necessary but urgent.

Mapping forest-based natural climate solutions

Natural climate solutions are critical actions of ecosystem stewardship to mitigate climate change. However, prioritizing locations and possible actions is challenging. We demonstrate a generalizable approach for identifying potential opportunities for natural climate solutions by creating a spatial hierarchy of land management restrictions. Global forest carbon stocks and flux models were then used to explore forest-based natural climate solutions in the high-carbon density coastal temperate rainforests of western North America. Our results show 13 million hectares are available for action, an area that holds 4,900 ± 640 megatonnes of carbon dioxide equivalent and represents 45% of regional and 0.5% of global aboveground forest carbon stocks. Based on historical trends, a 10% reduction in average annual forest carbon loss through improved forest management and conservation could reduce forest carbon emissions by 9.1 megatonnes of carbon dioxide equivalent per year, corresponding to 5.2% of the 2030 land-based climate commitments made by the United States and Canada. Large-scale implementation of natural climate solutions will require collaborative planning with forest-dependent communities, industry, governments, and Indigenous peoples.

Spodosol development and soil organic carbon distribution along a lithosequence in perhumid coastal temperate rainforest

AbstractA dense concentration of old‐growth forest and a wet, cold climate promote mineral weathering and leaching in coastal temperate rainforest soils. Our objective was to assess soil development and soil organic carbon (SOC) distribution across 18 soil profiles in remote, upland terrain of southeast Alaska where pedon data are sparse. We made soil morphological observations, collected samples, and completed laboratory analyses to measure SOC content, pH, and particle size distribution. The survey of upland backslope soils included north‐ and south‐facing hillslopes derived from three lithologies (slate, metavolcanic, and phyllite). The soils across all sites were very gravelly (51.8 ± 20.4% coarse fragments), acidic (mineral soil pH 4.85 ± 0.45), and moderately deep (96.56 ± 37.80 cm); thin, broken E horizons were underlain by thick, carbon‐rich spodic horizons. Soil development was relatively consistent as demonstrated by the Profile Development Index with values from 15 to 26 and Podzolization Index values spanning 8 to 14. A mean pedon SOC stock of 198.02 ± 81.42 Mg C ha−1 (n = 18) was calculated using data collected for all upland organic and mineral soils from our work. The accumulation of SOC was similar among soils formed from contrasting lithologies with averages of 182 ± 15.70 Mg C ha−1 for slate, 188 ± 53.80 Mg C ha−1 for metavolcanic, and 218 ± 124 Mg C ha−1 for phyllite. Our work contributes to soil morphological observations, laboratory data, and SOC stock estimates required to better constrain and model pedogenic processes and SOC stock in remote forests where data sets are limited.

Assessing decadal soil redistribution rates using 239+240Pu across diverse lithologies in Southeast Alaska

AbstractQuantifying soil redistribution rates, including both erosion and deposition, is critical for understanding erosion processes, landscape evolution, land management strategies, and the carbon cycle. In the Northeast Pacific coastal temperate rainforest, the interaction of perhumid climate and dense coniferous forest tends to form Spodosols which are soils characterized by a subsurface accumulation of organic matter and iron and aluminum oxides, across a range of contrasting lithologies. Deep Spodosols are frequently found on steep backslopes (up to 60%) of colluvial deposits, where shallower soils would typically be expected. We hypothesized that deep Spodosols in Southeast Alaska indicate slope stability, exhibiting negligible soil redistribution rates and stable surfaces regardless of the lithology. Our objective was to quantify soil redistribution rates for Spodosols formed on steep slopes across a range of lithologies in hilly and mountainous areas of Juneau, AK. We used 239+240Pu isotopes to quantify soil erosion and deposition rates in Spodosols formed on colluvial deposits from tonalite, slate, metavolcanic rock, and phyllite. 239+240Pu measurements revealed negligible soil redistribution rates for all studied pedons, ranging from erosion rates of 0.51 t/ha/year to deposition rates up to 0.43 t/ha/year. No difference was detected between the hill and mountain landforms, further supporting the idea that Spodosols could indicate slope stability over decadal timescales across the region. Understanding the resilience of Spodosols to erosion processes in varied lithologies and landforms on steep slopes is paramount for making informed decisions regarding sustainable land use, landslide risk mitigation, and effective carbon sequestration strategies.

Defoliator outbreaks track with warming across the Pacific coastal temperate rainforest of North America

The biogeography of irruptive insect herbivores is determined by host availability and climate conditions. As such, outbreak distributions are sensitive to climatic change, especially across large latitudinal gradients. Here, we investigate the outbreak distributions of two understudied defoliators, hemlock sawfly Neodiprion tsugae (Hymenoptera) and western blackheaded budworm Acleris gloverana (Lepidoptera), that have both recently impacted the greatest land area recorded across the Pacific coastal temperate rainforest since the establishment of aerial survey programs. We compiled polygon‐based estimates of insect damage collected by aerial observers, forest inventory, and downscaled climatic data to develop gridded estimates of bioclimatic conditions across the extent of the Pacific coastal temperate rainforest, including the continental United States, British Columbia and Alaska. We leveraged these data to develop ensemble machine learning models with the goal of predicting the outbreak distribution of each insect. In this manuscript we: 1) describe the historical patterns of defoliator outbreaks, 2) identify and describe climatic conditions associated with outbreaks in both species and 3) assess whether historic outbreaks have tracked geographic shifts in climate conditions across the region. We demonstrate that outbreaks of hemlock sawfly and western blackheaded budworm have been observed across the Pacific coastal temperature rainforests of North America in each decade since the establishment of the Canadian and United States aerial survey programs. The distribution of outbreaks by both insects were best explained by host availability, a limited range of spring, summer, and winter temperatures, and minimum precipitation. Finally, we demonstrate that outbreaks have tracked the poleward shift in suitable climate over the last century. This study establishes a baseline understanding of the climatic constraints and biogeographic patterns of historic sawfly and budworm outbreaks across the Pacific coastal temperate rainforest and emphasizes the overarching importance of climate in driving the irruptive dynamics of these defoliator species.Keywords: climate envelope, defoliators, hemlock sawfly, Pacific coastal temperate rainforest, population dynamics, western blackheaded budworm

The distribution of tree biomass carbon within the Pacific Coastal Temperate Rainforest, a disproportionally carbon dense forest

Spatially explicit global estimates of forest carbon storage are typically coarsely scaled. While useful, these estimates do not account for the variability and distribution of carbon at management scales. We asked how climate, topography, and disturbance regimes interact across and within geopolitical boundaries to influence tree biomass carbon, using the perhumid region of the Pacific Coastal Temperate Rainforest, an infrequently disturbed carbon dense landscape, as a test case. We leveraged permanent sample plots in southeast Alaska and coastal British Columbia and used multiple quantile regression forests and generalized linear models to estimate tree biomass carbon stocks and the effects of topography, climate, and disturbance regimes. We estimate tree biomass carbon stocks are either 211 (SD = 163) Mg C ha−1 or 218 (SD = 169) Mg C ha−1. Natural disturbance regimes had no correlation with tree biomass but logging decreased tree biomass carbon and the effect diminished with increasing time since logging. Despite accounting for 0.3% of global forest area, this forest stores between 0.63% and 1.07% of global aboveground forest carbon as aboveground live tree biomass. The disparate impact of logging and natural disturbance regimes on tree biomass carbon suggests a mismatch between current forest management and disturbance history.

Ideas and perspectives: Sensing energy and matter fluxes in a biota-dominated Patagonian landscape through environmental seismology – introducing the Pumalín Critical Zone Observatory

Abstract. The coastal temperate rainforests (CTRs) of Chilean Patagonia are a valuable forest biome on Earth given their prominent role in biogeochemical cycling and the ecological value and dynamics of surface processes. The Patagonian CTRs are amongst the most carbon-rich biomes on Earth. Together with frequent landscape disturbances, these forests potentially allow for episodic and massive release or sequestration of carbon into and from the atmosphere. We argue that, despite their particular biogeographic, geochemical, and ecological roles, the Patagonian CTRs in particular and the global CTRs in general are not adequately represented in the current catalog listing critical zone observatories (CZOs). Here, we present the Pumalín CZO as the first of its kind, located in Pumalín National Park in northern Chilean Patagonia. We consider our CZO a representative end-member of undisturbed ecosystem functioning of the Patagonian CTRs. We have identified four core research themes for the Pumalín CZO around which our activities circle in an integrative, quantitative, and generic approach using a range of emerging techniques. Our methodological blend includes an environmental seismology that also fills a critical spatiotemporal scale in terms of monitoring critical zone and surface processes with a minimum intervention in those pristine forests. We aim to gain quantitative understanding of these topics: (1) carbon sink functioning; (2) biota-driven landscape evolution; (3) water, biogeological, and energy fluxes; and (4) disturbance regime understanding. Our findings highlight the multitude of active functions that trees in particular and forests in general may have on the entire cascade of surface processes and the concomitant carbon cycling. This highlights the importance of an integrated approach, i.e., “one physical system”, as proposed by Richter and Billings (2015), and accounts for the recent advances in pushing nature conservation along the Chilean coast.

Abundance of microbial community genes encoding terminal proteins of the aerobic and denitrification respiratory chains as indicators of ecohydrologic gradients in a coastal temperate rainforest

The persistence of soil organic carbon (SOC) is closely linked to the capacity of the soil microbial community to catalyze oxidative degradation of organic matter. This study uses a landscape-scale metagenomics approach to examine the relative abundances of genes encoding different terminal electron acceptors used for aerobic respiration and denitrification between soil microbial communities across an ecohydrologic gradient. The perhumid zone of the North Pacific coastal temperate rainforest serves as a template to test the associations between these differing respiratory pathways, soil conditions, and tree species biomass. We used the occurrence of reads in soil metagenomes as a proxy for the relative abundance of genes across the ecohydrologic gradient and identified distinct microbial fingerprints differentiating the driest (upland forest) and wettest (palustrine scrub-shrub and palustrine emergent wetland) ecosystem types. There was little gene-based differentiation between the ecosystem types at the wettest end of the ecohydrologic gradient - scrub-shrub wetland and emergent wetlands – while forested wetlands, which occur as gradient sites between upland forests and emergent wetlands on the landscape, were characterized by substantial metagenomic variability and, consequently, overlapped in their soil metagenome with the other ecosystem classes. Hydrology, as measured by groundwater depth was a predictor of O2 and N-oxide reductase abundances. High affinity O2 reductase genes were associated with wetter topographic positions, which has not been shown at the ecosystem scale, or in soils in-situ previously. N-oxide reductase genes were more associated with plant communities found at wetland sites but were not related to soil inorganic nitrogen, suggesting that nitrate supply may be limiting to denitrifiers ubiquitously across this gradient. Two plant species, Tsuga heterophylla (TSHE) and Pinus contorta spp. contorta (PICO), were more strongly correlated with O2-reductase and N-oxide reductase genes than site hydrology, respectively. This research represents a step toward fingerprinting the ecosystem microbiome using genes coding for specific terminal electron acceptors that control the fate of SOC and their ecohydrologic controls.

Small, Coastal Temperate Rainforest Watersheds Dominate Dissolved Organic Carbon Transport to the Northeast Pacific Ocean

AbstractThe northeast Pacific Coastal Temperate Rainforest (NPCTR) extending from southeast Alaska to northern California is characterized by high precipitation and large stores of recently fixed biological carbon. We show that 3.5 Tg‐C yr−1 as dissolved organic carbon (DOC) is exported from the NPCTR drainage basin to the coastal ocean. More than 56% of this riverine DOC flux originates from thousands of small (mean = 118 km2), coastal watersheds comprising 22% of the NPCTR drainage basin. The average DOC yield from NPCTR coastal watersheds (6.20 g‐C m−2 yr−1) exceeds that from Earth's tropical regions by roughly a factor of three. The highest yields occur in small, coastal watersheds in the central NPCTR due to the balance of moderate temperature, high precipitation, and high soil organic carbon stocks. These findings indicate DOC export from NPCTR watersheds may play an important role in regional‐scale heterotrophy within near‐shore marine ecosystems in the northeast Pacific.

Wildlife studies on the Tongass National Forest challenge essential assumptions of its wildlife conservation strategy

AbstractThe Tongass National Forest in southeast Alaska, USA, includes the Alexander Archipelago and narrow North American mainland, comprising one of the largest remaining, largely pristine, coastal temperate rainforest in the world. Management of the Tongass has become increasingly challenging because of expectations of a conservation framework designed to maintain viable populations of native wildlife species while decades of extensive clearcut logging of old‐growth forests has continued. We used the findings of multiple published studies conducted on the Tongass from 1998 to 2017 to examine 4 assumptions of its wildlife conservation strategy (WCS): forest planning assessments of wildlife viability were realistic, forest management and conservation policies are implemented at appropriate ecological scales, old‐growth reserves are effective habitat conservation areas and ensure functional connectivity, and forest‐wide standards and guidelines ensure sufficient habitat for sensitive species in managed landscapes. Several ecological field studies, population and spatial analyses and modeling, and statistical analyses revealed that wildlife viability assessments to evaluate forest plan alternatives underestimated the risk of extinction by only examining individual vulnerable species rather than considering joint probabilities across multiple species; the ecological scale of management and conservation policies do not adequately consider area‐sensitive vulnerabilities of island communities as evidenced by the increasing risk of extirpation of island endemics whose populations have become isolated and reduced; old‐growth reserves are unlikely to maintain viable populations of endemic small mammals in isolation or as functionally connected metapopulations; and a spatially explicit analysis of individual home ranges demonstrated that forest‐wide standards and guidelines provide about half the breeding habitat needed by a federally listed endemic raptor, the Queen Charlotte goshawk (Accipiter gentilis laingi), of which only half of that is secure. Thus, assertions that the WCS is properly functioning as designed are dubious because a comprehensive monitoring plan has not been implemented and vital underlying assumptions are not supported by available science. We recommend 3 forest management and conservation policy adjustments: limit size and location old‐growth forest harvests, restore forests through intermediate stand management of second growth, and conduct a formal review of WCS elements and assumptions.

Geo-archaeology and Haíɫzaqv oral history: Long-term human investment and resource use at EkTb-9, Triquet Island, N̓úláw̓itxˇv Tribal Area, Central Coast, British Columbia, Canada

Archaeological site EkTb-9 is located on Triquet Island in the N̓úláw̓itxˇv Tribal area of Haíɫzaqv (Heiltsuk) Nation territory, on the Central Coast of British Columbia, Canada. The results of radiometric dating and the analysis of palaeoenvironmental correlates indicate that the site was a persistent place of repeated human occupation spanning the early post-glacial period to the present day. This paper focuses on the paleogeographic and geomorphic setting of EkTb-9. Stratigraphic records show a complex array of site formation processes. Marine beach sediments are elevated above modern sea level, an extensive sand sheet consistent with a possible palaeotsunami event is present, as well as organic soils and peat deposits. Cultural strata are interbedded with these and include both shell-less and preserved shell accumulations. Results from our geo-archaeological and palaeoenvironmental assessments indicate that the outer coastal island changed from what was likely an open landscape during the early post-glacial period to the hypermaritime coastal temperate rainforest environs of the present day. Our interpretations are combined with Haíɫzaqv oral history and discussions are organized by Haíɫzaqv temporal phases identified for the N̓úláw̓itxˇv Tribal area. Combining Indigenous knowledge with our archaeological interpretations enhances our collective understanding of the long-term record of human occupation and investment at EkTb-9.

A Record-Setting 2021 Heat Wave in Western Canada Had a Significant Temporary Impact on Greenness of the World’s Largest Protected Temperate Rainforest

Extreme climate anomalies are expected to become more frequent under climate change, and rare extreme events, such as the 2021 western North American heat wave, provide an opportunity for comparative empirical analysis of ecosystem resilience. This study evaluates anomalies in a remotely sensed enhanced vegetation index (EVI) in the aftermath of the record-setting western North American heat wave in 2021, with temperatures approaching 50 °C in coastal and interior regions of the Pacific Northwest. The results show that the forest ecosystems most affected were not necessarily those that experienced the highest absolute temperature values. Instead, the greatest reductions in greenness were observed across northern coastal temperate rainforests. Most affected were the cooler, very wet, hyper-maritime ecosystems that are normally buffered from large temperature fluctuation by a strong oceanic influence. In contrast, moisture-limited forests of the interior plateau of British Columbia, where most of the all-time record temperatures occurred, generally showed normal or even increased productivity during and after the heat wave. A putative explanation for this heat resistance of interior forests was normal or above average precipitation leading up to the heat event, allowing for transpirational cooling. Nevertheless, the data suggest that the largest protected coastal temperate rainforest in the world, with 6.4 million hectares, is comparatively more vulnerable to extreme heat waves, which are expected to become more frequent under climate warming, than other ecosystems of the Pacific Northwest.

Trees in the Stream: Determining Patterns of Terrestrial Dissolved Organic Matter Contributions to the Northeast Pacific Coastal Temperate Rainforest

AbstractDissolved organic matter (DOM) composition in small watersheds depends on complex antecedent conditions that ultimately influence DOM generation, processing, and stability downstream. Here, we used ultrahigh resolution Fourier‐transform ion cyclotron resonance mass spectrometry and total dissolved nitrogen and dissolved organic carbon concentrations to investigate how DOM is produced in distinct sub‐catchment types (poor fen, forested wetland, and upland forest) and transported through a watershed in the northeast Pacific coastal temperate rainforest (NPCTR). We traced a suite of previously identified source‐specific marker formulae from vegetation and soil downstream and used them to test models of terrestrial DOM inputs. Marker formulae escaped microbial degradation and were exported from the watershed, demonstrating strong land‐to‐ocean connectivity through the transfer of unmodified tree DOM from specific tree species into the marine environment. Simple hydrologic and temperature variables were better able to predict inputs of soil‐sourced DOM into the stream network than tree‐sourced DOM, highlighting the role of antecedent conditions (e.g., plant growth stage) in DOM source availability and hydrologic flow connectivity, particularly for plant‐derived material. Forested wetland pore waters featured thousands of nitrogen‐containing molecular formulae that potentially provide a path of direct organic nitrogen uptake to organisms. The modified aromaticity index peaked in midsummer (up to 0.55 for fen headwaters) suggesting DOM inputs from freshly produced vegetation provide a strong summertime terrestrial signal. As the climate changes, new watershed‐scale conditions may further complicate predictions of DOM source availability, flow connectivity, and downstream fate in NPCTR watersheds.

Glacier runoff influences biogeochemistry and resource availability in coastal temperate rainforest streams: Implications for juvenile salmon growth

AbstractMeltwater contributions to watersheds are shrinking as glaciers disappear, altering the flow, temperature, and biogeochemistry of freshwaters. A potential consequence of this landscape change is that streamflow patterns within glacierized watersheds will become more homogenous, potentially altering the capacity of watersheds to support Pacific salmon. To assess heterogeneity in stream habitat quality for juvenile salmon in a watershed in the Alaska Coast Mountains, we collected organic matter and invertebrate drift and measured streamwater physical and biogeochemical properties over the main runoff season in two adjacent tributaries, one fed mainly by rain and the other partially by glacier ice/snowmelt. We then used bioenergetic modeling to evaluate how temporal patterns in water temperature and invertebrate drift in each tributary influence juvenile salmon growth potential. Across the study period, average invertebrate drift concentrations were similar in non‐glacierized Montana (0.33 mg m−3) and glacier‐influenced McGinnis Creeks (0.38 mg m−3). However, seasonal patterns of invertebrate drift were temporally asynchronous between the two streams. Invertebrate drift and modeled fish growth were generally higher in McGinnis Creek in the spring and Montana Creek in the Summer. For juvenile salmon, tracking these resource asynchronies by moving between tributaries resulted in 20% greater growth than could be obtained within either stream alone. These results suggest that hydrologic heterogeneity within watersheds may enhance the diversity of foraging and growth opportunities for mobile aquatic organisms, which may be essential for supporting productive and resilient natural salmon runs.

Lithological controls on soil geochemistry and clay mineralogy across Spodosols in the coastal temperate rainforest of southeast Alaska

The interaction of similar soil forming factors with different parent materials determines soil chemical weathering, influencing soil processes and properties. In the coastal temperate rainforests of southeast Alaska, Spodosols is the dominant soil order in well-drained parent materials regardless of the lithology. Yet, the role of lithology on chemical weathering, base cation depletion, and mineral transformation during pedogenesis remains elusive. Here, we established a lithosequence comprised of soils derived from tonalite, phyllite, slate, and metavolcanic rocks to test the hypothesis that despite the soils in southeast Alaska presenting similar taxonomy and morphology, the influence of lithology in chemical weathering intensity and mineralogy can be detected. We evaluated physicochemical properties, clay mineralogy, Fe-Al oxides, chemical weathering, and elemental mass balance on eleven Spodosols sampled along the lithosequence. We also propose a new weathering index, the Weathering Index for Spodosols (WISP), suitable to evaluate the weathering degree of soils with Al mobility and base-rich parent materials. This index fills a gap in traditional weathering indices that uses Al as an immobile element and/or does not evaluate the leaching of main base cations. We found the pedons across the lithosequence expressed similar physicochemical properties, with predominantly thick profiles, presenting andic properties, relatively thick spodic horizons, and thin E horizons. Podzolization imposed similar mineral transformation trends, mainly dissolution of chlorite, mica alteration to interstratified mica-vermiculite, and formation of smectite in E horizons. Kaolinite was detected in the soils from all lithologies, but only in trace amounts in phyllite soils. Fe oxides depth distribution was similar but with a higher concentration in the slate (44.5 ± 4.2 g/kg), followed by metavolcanic (31.6 ± 4.0 g/kg), phyllite (27.9 ± 3.8 g/kg), and tonalite soils (19.9 ± 5.7 g/kg) and predominantly as organometallic complexes (extracted by Na-pyrophosphate). The stronger weathering of chlorite and mica in the E horizons was reflected in larger losses of Mg and K, while Ca and Na were more depleted in the spodic horizons, suggesting plagioclase weathering. Slate soils were the most depleted in base cations, followed by phyllite, tonalite, and metavolcanic soils. The more depleted status of slate soils was supported by the higher WISP values (WISP = 62), followed by phyllite (WISP = 55), tonalite (WISP = 53), and metavolcanic soils (WISP = 45). Our results demonstrated that lithology controlled elemental depletion intensities, Fe oxide concentrations, and partially the clay fraction mineralogy in addition to podzolization acting as a dominant pedogenic process across all sites. These findings advance our understanding of the role of lithology on soil mineralogy/geochemistry that impacts critical soil functions, such as the soil carbon cycle, elemental fluxes, organo-mineral interactions, and solid-solution reactions.

High-resolution streamflow and weather data (2013–2019) for seven small coastal watersheds in the northeast Pacific coastal temperate rainforest, Canada

Abstract. Hydrometeorological observations of small watersheds of the northeast Pacific coastal temperate rainforest (NPCTR) of North America are important to understand land to ocean ecological connections and to provide the scientific basis for regional environmental management decisions. The Hakai Institute operates a densely networked and long-term hydrometeorological monitoring observatory that fills a spatial data gap in the remote and sparsely gauged outer coast of the NPCTR. Here we present the first 5 water years (October 2013–October 2019) of high-resolution streamflow and weather data from seven small (< 13 km2) coastal watersheds. Measuring rainfall and streamflow in remote and topographically complex rainforest environments is challenging; hence, advanced and novel automated measurement methods were used. These methods, specifically for streamflow measurement, allowed us to quantify uncertainty and identify key sources of error, which varied by gauging location. Average yearly rainfall was 3267 mm, resulting in 2317 mm of runoff and 0.1087 km3 of freshwater exports from all seven watersheds per year. However, rainfall and runoff were highly variable, depending on the location and elevation. The seven watersheds have rainfall-dominated (pluvial) streamflow regimes, streamflow responses are rapid, and most water exports are driven by high-intensity fall and winter storm events. The complete hourly and 5 min interval datasets can be accessed at https://doi.org/10.21966/J99C-9C14 (Korver et al., 2021), and accompanying watershed delineations with metrics can be found at https://doi.org/10.21966/1.15311 (Gonzalez Arriola et al., 2015).

Edificios históricos de madera, restaurados con fines públicos en el Sur de Chile. Un análisis crítico y un enfoque hacia el paisaje cultural

The objective of this paper is to update and summarize the arguments behind the Integrated Heritage Rehabilitation (IHR) for Wooden Cities methodology. Building in the Coastal Temperate Rainforest ecoregion relied on native species, and is still characteristic of the towns in southern Chile, including the city of Valdivia. However, the historic town’s urban fabric is vulnerable to natural disasters and neoliberal market practices. Regulations and instruments for architectural restoration hinder IHR since their primary focus lies in social sciences, excluding the fundamental architectonic technical aspects, as well as a broader understanding of the context. Through an analysis of a set of historic buildings restored with public funds, the relationship between social sciences, engineering, architecture, and the theories of public use and landscape is patent. It is evident that there is a need to establish effective practices to extend the service life of buildings through cultural heritage management. Eight key points were identified, that connect history with the material conditions, which today are lacking in the Chilean Public Service. For the restoration processes to be integrated, evaluations must include new dimensions, such as the economic relationship and the material or tangible management, as well as the integration with the surrounding original architectural identity and the ease with which it can be culturally associated. From the harmonization of these eight points within the heritage regulatory framework, an improvement of the integrated rehabilitation of heritage buildings in the southern Chilean towns is expected, with priority given to timber conservation and public contribution.

Seasonally and Spatially Variable Organic Matter Contributions From Watershed, Marine Macrophyte, and Pelagic Sources to the Northeast Pacific Coastal Ocean Margin

Globally, coastal waters are considered biogeochemical hotspots because they receive, transform, and integrate materials and waters from both land and the open ocean. Extending from northern California to southeast Alaska, the Northeast Pacific Coastal Temperate Rainforest (NPCTR) region is no exception to this, and hosts a diversity of watershed types (old-growth rainforest, bog forest, glaciers), and tidal (sheltered, exposed) and pelagic marine (deep fjord, shallow estuary, well-mixed channel) environments. With large freshwater fluxes to the coastal ocean, cross-ecosystem connectivity in the NPCTR is expected to be high, but seasonally variable, with pulses in runoff from rainfall, snowmelt and glacial melt, and primary production associated with changes in ocean upwelling and incident light. However, the relative contribution of each ecosystem to surface ocean organic matter pools over time and space remains poorly constrained, despite their importance for the structure and function of coastal marine ecosystems. Here, we use a four-year dataset of particulate organic matter (POM) chemical composition (δ13C, δ15N, C:N ratio) to quantify the relative contributions of watershed materials via riverine inputs, marine phytoplankton, and macrophytes (macroalgae and seagrass) to surface waters (0-10 m) at 11 stations representing fjord, shallow non-fjord estuary, sheltered channel and well-mixed coastal environments at the heart of the NPCTR in British Columbia, Canada. Watershed, marine phytoplankton, and macrophyte contributions to surficial POM ranged between 5-78%, 22-88%, and 0.1-18%, respectively, and varied by season and station. Watershed inputs were the primary source of POM across all stations in winter and were important throughout the year within the fjord. Marine phytoplankton were the principal source of POM in spring and at all stations outside of the fjord through summer and autumn, while macrophyte contributions were greatest in summer. These results demonstrated high, but seasonally and spatially variable, connectivity between ecosystems that are often considered in isolation of one another and highlight the need to consider coastal waters as integrated land-ocean meta-ecosystems. Future work should investigate how heterogeneity in POM sources determines its fate in coastal ecosystems,and the relative importance of different basal organic matter sources for the marine food web.

Watershed Classification Predicts Streamflow Regime and Organic Carbon Dynamics in the Northeast Pacific Coastal Temperate Rainforest

AbstractWatershed classification has long been a key tool in the hydrological sciences, but few studies have been extended to biogeochemistry. We developed a combined hydro‐biogeochemical classification for watersheds draining to the coastal margin of the Northeast Pacific coastal temperate rainforest (1,443,062 km2), including 2,695 small coastal rivers (SCR) and 10 large continental watersheds. We used cluster analysis to group SCR watersheds into 12 types, based on watershed properties. The most important variables for distinguishing SCR watershed types were evapotranspiration, slope, snowfall, and total precipitation. We used both streamflow and dissolved organic carbon (DOC) measurements from rivers (n = 104 and 90 watersheds respectively) to validate the classification. Watershed types corresponded with broad differences in streamflow regime, mean annual runoff, DOC seasonality, and mean DOC concentration. These links between watershed type and river conditions enabled the first region‐wide empirical characterization of river hydro‐biogeochemistry at the land‐sea margin, spanning extensive ungauged and unsampled areas. We found very high annual runoff (mean > 3,000 mm, n = 10) in three watershed types totaling 59,024 km2 and ranging from heavily glacierized mountain watersheds with high flow in summer to a rain‐fed mountain watershed type with high flow in fall‐winter. DOC hotspots (mean > 4 mg L−1, n = 14) were found in three other watershed types (48,557 km2) with perhumid rainforest climates and less‐mountainous topography. We described four patterns of DOC seasonality linked to watershed hydrology, with fall‐flushing being widespread. Hydro‐biogeochemical watershed classification may be useful for other complex regions with sparse observation networks.

Contrasting Impacts of Climate Warming on Coastal Old-Growth Tree Species Reveal an Early Warning of Forest Decline

Old-growth forests in the Pacific Northwest are being fundamentally altered by climate change. A primary example of this is yellow-cedar (Callitropsis nootkatensis), a culturally and economically important species, which has suffered widespread decline across its range since the beginning of the twentieth century. We used tree rings to compare the climate-growth response of yellow-cedar to two co-occurring species; western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis), in an old-growth forest on Haida Gwaii, Canada, to better understand the unique climatic drivers of a species that is declining across its range. We developed three species-specific chronologies spanning 560–770 years, reconstructing a long-term record of species growth and dynamics over time. The climate is strongly influenced by the Pacific Decadal Oscillation (PDO), a multi-decadal pattern of ocean-atmospheric climate variability. Climate varied across three time periods that have coincided with major shifts in the PDO during the twentieth century [1901–1945 (neutral/positive), 1946–1976 (negative) and 1977–2015 (positive)]. Conditions were significantly warmer and wetter during positive phases, with the greatest maximum temperatures in the most recent period. We used complimentary methods of comparison, including Morlet wavelet analysis, Pearson correlations, and linear-mixed effects modeling to investigate the relations between climate and species growth. All three species exhibited multi-decadal frequency variation, strongest for yellow-cedar, suggesting the influence of the PDO. Consistent with this, the strength and direction of climate-growth correlations varied among PDO phases. Growing season temperature in the year of ring formation was strongly positively correlated to yellow-cedar and western hemlock growth, most significantly in the latter two time periods, representing a release from a temperature limitation. Sitka spruce growth was only weakly associated with climate. Yellow-cedar responded negatively to winter temperature from 1977 to 2015, consistent with the decline mechanism. Increased yellow-cedar mortality has been linked to warmer winters and snow loss. This study provides new insights into yellow-cedar decline, finding the first evidence of decline-related growth patterns in an apparently healthy, productive coastal temperate rainforest.