Northern Sites Research Articles

Reproductive phenology calendar and its correlation with air temperature in five Mediterranean almond [Prunus dulcis (Mill.) D.A. Webb] cultivars grown in Morocco

Agro-climatic requirements are of crucial importance for establishment and management of nut tree orchards. In this work, we investigated timing and duration of key reproductive phenology events and their chilling units (CU) and heat requirements namely growing degree-days (GDD) and degree-hours (GDH) in five Mediterranean almond cultivars of early (‘Marcona’), intermediate (‘Fournat de Brézenaud’), and late flowering time (‘Ferraduel’, ‘Ferragnès’, and ‘Tuono’). Field phenological observations were performed during three growing seasons (2016–2018) across five contrasting sites in northern and eastern Morocco. Phenological records consisted of timing of initial inflorescence (Inf), inflorescence duration (Inf D), initial flowering (Ini F), full flowering (Ful F), final flowering (Fin F), flowering duration (FD), ripening (Rip), fruit development period (FDP). Our outcomes reveal that ‘Marcona’ and ‘Fournat de Brézenaud’ presented low CUs. ‘Tuono’, ‘Ferraduel’, and ‘Ferragnès’ required higher GDD and GDH to reach flowering time. Additionally, ‘Marcona’ had the highest FDP and GDD and GDH for ripening. Sites of northern Morocco exhibited a delayed timing of inflorescence and flowering and longer Inf D, FD, and FDP and high GDD and GDH for different phenological events. 2016 had low CU resulting in delayed timing of inflorescence and flowering but shortened Inf D and FD. Important correlations were outlined among phenological events and agro-climatic requirements. Principal component analysis explains data variation through first principal component (PC, genotypic), the second and the third PC discriminated sites and growing seasons, respectively (environmental components). In conclusions, owing to their early flowering and fruit set, ‘Fournat de Brézenaud’ and ‘Marcona’ should be grown in areas with low frost risks. ‘Marcona’ is not recommended for warmer environments because of its longer FDP. Chill decline induced by global warming may threaten production of high chilling requirement cultivars (‘Ferraduel’, ‘Ferragnès’, and ‘Tuono’).

Quantifying an Overlooked Deciduous‐Needleleaf Carbon Sink at the Southern Margin of the Central‐Siberian Permafrost Zone

AbstractWith over 700 million km2 Siberia is the largest expanse of the northern boreal forest—deciduous‐needleleaf larch. Temperatures are increasing across this region, but the consequences to carbon balances are not well understood for larch forests. We present flux measurements from a larch forest near the southern edge of Central‐Siberia where permafrost degradation and ecosystem shifts are already observed. Results indicate net carbon exchanges are influenced by the seasonality of permafrost active layers, temperature and humidity, and soil water availability. During periods when surface soils are fully thawed, larch forest is a significant carbon sink. During the spring‐thaw and fall‐freeze transition, there is a weak signal of carbon uptake at mid‐day. Net carbon exchanges are near‐zero when the soil is fully frozen from the surface down to the permafrost. We fit an empirical ecosystem functional model to quantify the dependence of larch‐forest carbon balance on climatic drivers. The model provides a basis for ecosystem carbon budgets over time and space. Larch differs from boreal evergreens by having higher maximum productivity and lower respiration, leading to an increased carbon sink. Comparison to previous measurements from another northern larch site suggests climate change will result in an increased forest carbon sink if the southern larch subtype replaces the northern subtype. Observations of carbon fluxes in Siberian larch are still too sparse to adequately determine age dependence, inter‐annual variability, and spatial heterogeneity though they suggest that boreal larch accounts for a larger fraction of global carbon uptake than has been previously recognized.

Sulfide oxidation during the simulated weathering of pyrrhotite-rich tailings: Impacts of freeze-thaw cycles and chloride salinity

Kinetic leached columns (KLCs) were used to simulate the weathering of pyrrhotite-rich tailings from Raglan Mine (QC, Canada) and evaluate the effects of freeze-thaw cycles and salinity on long-term trends in sulfide oxidation. This study focuses on the results of a series of oxygen consumption tests (OCTs) with additional observations from the dismantlement of the KLCs. Four treatments were evaluated in duplicate in the KLCs: (1) room-temperature and deionized water; (2) room-temperature and saline water; (3) freeze-thaw cycles and deionized water; and (4) freeze-thaw cycles and saline water. Oxygen fluxes showed no reproducible differences over the course of the study when comparing between deionized and saline water columns within each thermal regime. However, fluxes may have differed slightly at several timepoints. The room-temperature and freeze-thaw columns displayed somewhat different oxidative behaviors. Notably, all columns stabilized at similar oxygen fluxes, though the amount of time until stability differed for the two thermal regimes. Visual observations made upon dismantlement of the columns revealed extensive oxidation and cementation throughout the entire depth of the columns with no significant differences noted between the room-temperature and freeze-thaw columns. This study provides novel insights into the long-term evolution of sulfide oxidation in mine tailings weathering under conditions relevant to northern mine sites.

Population-size history inferences from the coho salmon (Oncorhynchus kisutch) genome.

Coho salmon (Oncorhynchus kisutch) are a culturally and economically important species that return from multiyear ocean migrations to spawn in rivers that flow to the Northern Pacific Ocean. Southern stocks of coho salmon in Canada and the United States have significantly declined over the past quarter century, and unfortunately, conservation efforts have not reversed this trend. To assist in stock management and conservation efforts, we generated a chromosome-level genome assembly. We also resequenced the genomes of 83 coho salmon across the North American range to identify nucleotide variants and understand the demographic histories of these salmon by modeling effective population size from genome-wide data. From demographic history modeling, we observed reductions in effective population sizes between 3,750 and 8,000 years ago for several northern sampling sites, which may correspond to bottleneck events during recolonization after glacial retreat.

Potential drivers and consequences of regional phosphate depletion in the western subtropical North Pacific

AbstractIn regions of the nitrogen limited low latitude ocean, phosphate can also be depleted to levels initiating stress responses in marine microbes. Here, we associate a broad region of phosphate depletion in the subtropical North Pacific with different levels of phosphorus stress. Nutrient and aerosol addition experiments demonstrated primary nitrogen limitation of the bulk phytoplankton community, with supply of aerosols relieving this limitation. At northern sites with depleted phosphate, alkaline phosphatase activities were enhanced, indicating elevated phosphorus stress. Analysis of satellite‐ and model‐derived aerosol loading showed that aerosol deposition was elevated in these regions. Surface rate measurements suggested that the regional enhancement in phosphate depletion was predominantly driven by elevated nitrogen fixation, likely stimulated by the coincident supply of aerosol iron. Such observations are important for predicting future biogeochemical responses in the subtropical North Pacific to changing aerosol supply.

Temporal partitioning of Bullacris unicolor (Orthoptera: Pneumoridae) calling activity to avoid predation

ABSTRACT Ecological interactions, including competition, predation, and environmental conditions, may significantly impact acoustic signalling behaviour. Here we characterise nocturnal signalling patterns in the bladder grasshopper Bullacris unicolor and relate this to biotic and abiotic factors, thus providing insights into ecological drivers of acoustic signalling behaviour. Passive acoustic recorders monitored nocturnal calling activity of the focal species, competitors, and predatory bats across the distribution of B. unicolor. Results indicate that B. unicolor calls preferentially at certain times of the night, but that peak activity period varies across the geographic range. There was a strong relationship between B. unicolor activity and bat activity. Bullacris unicolor populations further north showed an overall avoidance of bat echolocation call period, whereas further south an overlapping of call periods between B. unicolor and bat echolocation was observed. Bats at northern sites showed a distinct activity period early in the night and B. unicolor may thus reduce predation risk by shifting signalling activity to later in the night. In contrast, bats were active throughout the night at southern sites and B. unicolor did not delay calling activity in this region of its distribution, although the species did shift signalling slightly to reduce peak overlap with co-existing pneumorid species.

A widely-used eddy covariance gap-filling method creates systematic bias in carbon balance estimates

Climate change mitigation requires, besides reductions in greenhouse gas emissions, actions to increase carbon sinks in terrestrial ecosystems. A key measurement method for quantifying such sinks and calibrating models is the eddy covariance technique, but it requires imputation, or gap-filling, of missing data for determination of annual carbon balances of ecosystems. Previous comparisons of gap-filling methods have concluded that commonly used methods, such as marginal distribution sampling (MDS), do not have a significant impact on the carbon balance estimate. By analyzing an extensive, global data set, we show that MDS causes significant carbon balance errors for northern (latitude >60^circ) sites. MDS systematically overestimates the carbon dioxide (CO_2) emissions of carbon sources and underestimates the CO_2 sequestration of carbon sinks. We also reveal reasons for these biases and show how a machine learning method called extreme gradient boosting or a modified implementation of MDS can be used to substantially reduce the northern site bias.

Statistical Analysis for Understanding PM2.5 Air Quality and the Impacts of COVID-19 Social Distancing in Several Provinces and Cities in Vietnam.

Air pollution, especially in urban regions, is receiving increasing attention in Vietnam. Consequently, this work aimed to study and analyze the air quality in several provinces and cities in the country focusing on PM2.5. Moreover, the impacts of COVID-19 social distancing on the PM2.5 level were investigated. For this purpose, descriptive statistic, Box and Whisker plot, correlation matrix, temporal variation, and trend analysis were conducted. R-based program and the R package "openair" were employed for the calculations. Hourly PM2.5 data were obtained from 8 national air quality monitoring sites. The study results indicated that provinces and cities in the North experienced more PM2.5 pollution compared to the Central and South. PM2.5 concentrations at each monitoring site varied significantly. Among monitoring sites, the northern sites showed high PM2.5 correlations with each other than the other sites. Seasonal variation was observed with high PM2.5 concentration in the dry season and low PM2.5 concentration in the wet season. PM2.5 concentration variation during the week was not so different. Diurnal variation showed that PM2.5 concentration rose at peak traffic hours and dropped in the afternoon. There was mainly a decreasing trend in PM2.5 concentration over the studied period. The COVID-19 pandemic has contributed to PM2.5 reduction. In the months implemented social distancing for preventing the epidemic, PM2.5 concentration declined but it would mostly increase in the following months. This study provided updated and valuable assessments of recent PM2.5 air quality in Vietnam.

Enhanced loss but limited mobility of pyrogenic and organic matter in continuous permafrost-affected forest soils

Pyrogenic organic matter (PyOM) is a product of incomplete combustion during wildfires and an important pool of soil organic carbon (SOC). The dynamics of PyOM and SOC in boreal and permafrost-affected soils are largely unknown, while storing large amounts of global carbon and being vulnerable to climate change. Here, we traced the vertical mobility, allocation in soil fractions and decomposition losses of highly 13C-labeled PyOM and its precursor ryegrass organic matter (grass OM) after two years of in-situ incubation in soil cores installed in the upper 10 cm of continuous (northern sites) and discontinuous to sporadic (southern sites) permafrost-affected forest soils in Northern Canada. At the northern sites, up to three times more PyOM was lost by decomposition (39% of initial) compared to the southern sites (11% of initial). Losses of grass OM were substantial (69–84% of initial) and larger in southern soils. The vertical incorporation was limited and >90% of recovered PyOM and grass OM were found at the applied depth (0–3 cm). The PyOM strongly interacted with mineral surfaces, as indicated by around 40% recovered in the mineral-associated heavy density fractions (<63 μm). Microscale analyses by SEM and NanoSIMS showed that PyOM was mainly allocated towards the fine fraction in a particulate and aggregated form, highlighting the importance of abiotic processes for the incorporation of PyOM in permafrost-affected soils. The grass OM was mainly recovered in the mineral fractions at southern soils with enhanced allocation towards mineral surfaces as well as increased distribution at the microscale after initial decomposition, while it remained as particulate OM in northern soils. Our results highlight that permafrost-affected boreal forest soils are sensitive to fresh PyOM and OM inputs with substantial losses. Especially PyOM persistence depended on site and soil specific properties and not solely on its physico-chemical persistence. The responses are decoupled for PyOM and non-pyrolyzed OM and require a better understanding to evaluate carbon feedbacks of high-latitude soils with global warming and associated shifts in vegetation and wildfire regimes.

Characteristics and Source Apportionment of Atmospheric Fine Particles in Langfang in Autumn and Winter

In this study, we report observations of various chemical species in PM2.5 samples that were collected between November 25, 2019 and March 31, 2020 in the northern, urban, and southern areas of Langfang, among which the concentrations of PM2.5 followed the order of southern>urban>northern. The abundance and chemical compositions of the particles in this study were temporally and spatially variable, with major contributions from organic matter (25.4%), nitrate (21.5%), sulfate (11.0%), ammonium (13.5%), and crustal matter (13.7%). The contributions of nitrate, sulfate, and ammonium were higher in the urban site compared with that in the southern and northern sites. On the contrary, organic matter and crustal matter exhibited much higher values in the southern and northern sites. In addition, the contributions of organic matter to the particle mass decreased from 27.3% to 23.0%, and the total contributions of sulfate, nitrate, and ammonium ions increased from 38.7% to 51.3% between clean and haze days, respectively. Source apportionment using positive matrix factorization showed five PM2.5 sources: secondary inorganic aerosol (41.9%), traffic emissions (19.9%), coal combustion (12.7%), industrial pollution (9.1%), and mineral dust (9.3%). The contributions of the first two factors followed the order of urban>northern>southern, whereas the contributions of the last three factors followed the order of southern>northern>urban. Further, the contributions of secondary inorganic aerosol, traffic emissions, and coal combustion were higher on haze days, whereas the contributions of industrial pollution and mineral dust were higher on clean days.

Dieback of stringybark eucalypt forests in the Mount Lofty Ranges

ABSTRACT Canopy dieback and tree mortality are occurring in forests of the Mount Lofty Ranges (MLR), South Australia, dominated by Eucalyptus baxteri (Brown Stringybark) and E. obliqua (Messmate Stringybark). The extent and causes of decline are not fully understood, prohibiting evidence-based management. We explored the geographic and climatic distributions of MLR stringybark populations relative to eastern populations. We conducted field assessments of dieback aetiology, and analysed existing monitoring data. The MLR stringybarks are disjunct from eastern populations and occupy a more summer-arid niche. The species are susceptible to water stress and Phytophthora. Droughts during 2006–2009 and 2018–2019 may have contributed to dieback. However, field assessments suggest a complex landscape syndrome involving borer infestations and fire impacts among other factors, rather than solely hydraulic failure. Messmate Stringybark has suffered widespread, patchy stand collapse with no obvious common pattern with respect to topography or water availability, although northern range-edge sites are heavily affected. Brown Stringybark is less affected but has notable collapse sites. Further investigations should include regional surveys to record spatial and temporal patterns of tree mortality combined with remote sensing. Our findings confirm the susceptibility of stringybark forests to ecosystem collapse and highlight the need to better understand underlying causes.

Transitioning operational satellite grassland curing from MODIS to VIIRS

Background In Australia, grassland curing (senescence) is an essential component in fire danger calculations. In seven (out of eight) states/territories in Australia, operational curing data are derived from the MapVictoria satellite model. From 2013 to 2023, MapVictoria data have been calculated using MODerate resolution Imaging Spectroradiometer (MODIS) data from the Terra satellite. Terra has exceeded its designed mission lifetime, but the continuation of satellite curing data is crucial for fire agencies to continue fire danger calculations. Aims The aim of this study was to adjust the MapVictoria model so it could be calculated using a newer satellite sensor system: Visible Infrared Imaging Radiometer Suite (VIIRS). Methods Data from the VIIRS bands were adjusted to match those of MODIS using timeseries from 2013 to 2020. The adjusted VIIRS bands were used to derive a VIIRS curing model: ‘viirs-mvcuring’. Key results The viirs–mvcuring model exhibited lower curing estimates than MODIS by up to 2.6% in Northern sites and 1.4% in Southern sites and exhibited lower curing estimates than ground-based curing by 0.1% in Northern sites and 3.5% in Southern sites. Conclusions The development of the viirs–mvcuring model has ensured continued availability of satellite curing data. Implications The transition to VIIRS will provide continued input of curing into fire danger calculations across Australia.

Canadian high arctic ice core records of organophosphate flame retardants and plasticizers.

Organophosphate esters (OPEs) have been used as flame retardants, plasticizers, and anti-foaming agents over the past several decades. Of particular interest is the long range transport potential of OPEs given their ubiquitous detection in Arctic marine air. Here we report 19 OPE congeners in ice cores drilled on remote icefields and ice caps in the Canadian high Arctic. A multi-decadal temporal profile was constructed in the sectioned ice cores representing a time scale spanning the 1970s to 2014-16. In the Devon Ice Cap record, the annual total OPE (∑OPEs) depositional flux for all of 2014 was 81 μg m-2, with the profile dominated by triphenylphosphate (TPP, 9.4 μg m-2) and tris(2-chloroisopropyl) phosphate (TCPP, 42 μg m-2). Here, many OPEs displayed an exponentially increasing depositional flux including TCPP which had a doubling time of 4.1 ± 0.44 years. At the more northern site on Mt. Oxford icefield, the OPE fluxes were lower. Here, the annual ∑OPEs flux in 2016 was 5.3 μg m-2, dominated by TCPP (1.5 μg m-2) but also tris(2-butoxyethyl) phosphate (1.5 μg m-2 TBOEP). The temporal trend for halogenated OPEs in the Mt. Oxford icefield is bell-shaped, peaking in the mid-2000s. The observation of OPEs in remote Arctic ice cores demonstrates the cryosphere as a repository for these substances, and supports the potential for long-range transport of OPEs, likely associated with aerosol transport.

Influence of gypsum and cover crop on greenhouse gas emissions in soybean cropping systems

Agriculture has the opportunity to mitigate anthropogenic contributions to global change by increasing soil sequestration of greenhouse gases (GHG) and by reducing efflux through management. Common agricultural management practices include crop rotation and use of cover crops. Interest in the use of gypsum in agricultural systems has also increased in recent years. However, little is known regarding how combining gypsum with other management practices impact GHG emissions in soybean (<i>Glycine max</i> [L.] Merr.)-based cropping systems. A study was implemented at three locations (i.e., east-central Indiana, northwest Ohio, and east-central Alabama) to evaluate the influence of gypsum and cover cropping within a continuous soybean and a corn (<i>Zea mays</i> L.)–soybean rotation on crop yield and soil properties. Within this study, carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) were also monitored periodically following soybean seeding through harvest from 2012 to 2016. The combined gas data were then used to calculate a global warming potential (GWP). Overall, few differences in GHG emissions were observed across sites and years, and no consistent patterns were noted, likely due to large variabilities in gas efflux measurements and limited influence of treatments on trace gases. However, treatment differences were observed for one or more GHG within specific years and at specific sites. Comparison across sites revealed the warmer/wetter climate in Alabama resulted in greater CO₂ efflux, while climate and soil factors at the northern sites led to greater N₂O efflux. At all locations, CH₄ emissions were generally low and sites tended to be small net sinks. Given that GHG emissions drive GWP, it also showed few treatment responses and no consistent patterns. It can be concluded from this study that contributions of gypsum and cover crop to GHG emissions from soil in soybean cropping systems will likely have little influence on contributions to global climate change.

Distribution of soil physical and hydraulic properties between erosion and deposition topographies in five small catchments from north to south on the Loess Plateau of China

Soil erosion, the most widespread form of soil degradation worldwide, has been acknowledged to cause onsite soil physical deterioration. However, the off-site impact of erosion on the soil physical and hydraulic properties of deposited sediments remains unclear, especially at catchment or larger scales. Here, we measured soil physical and hydraulic properties in erosion topography (hillslopes) and deposition topography (check dams) at 0–2 m depth in five eroding catchments across China's Loess Plateau. Results indicated that the deposition zone exhibited a higher clay content (+13%) at the southern sites with a finer texture and a higher erosion modulus, while the same zone exhibited a higher sand content (+25%) at the northern sites with a coarser texture and a higher extreme rainfall erosivity. The deposition zone exhibited a higher bulk density (+9%) and a lower saturated hydraulic conductivity (-13%), field capacity (−9%), and porosity (-5%) than those of the erosion zone, which was strengthened by a higher mean annual precipitation. Soil macroaggregate proportion and mean weight diameter of aggregates were significantly lower in the deposition zone (14.36% and 0.69 mm, respectively) than those in the erosion zone (15.71% and 0.75 mm, respectively), and the differences were larger at sites with higher rainfall erosivity levels and in surface 20 cm soils. However, sediment reaggregation occurred due to the accumulation of binding agents such as clay and organic carbon at sites with lower rainfall erosivity levels. The spatial heterogeneities of sediment physical and hydraulic properties were greater than or similar to those of soils in the erosion zone. Results of our study highlight the dependence of variations in soil physical and hydraulic properties driven by erosion and deposition on erosion factors, which contributes to a better understanding of the hydrology cycle and carbon stability in erosion and deposition topographies.

Evidence of lithic blade technology in southwest Madagascar

This rapid communication describes a lithic blade that was recently recovered during excavations in the Velondriake Marine Protected Area in southwest Madagascar. This represents the only recorded archaeological lithic blade recovered from southwest Madagascar. The blade was recovered in situ at a depth of 1.66 m, a deposit dating to between 750 and 1200 BP at site G134, adjacent to the modern village of Antsaragnasoa. While similar in material choice (translucent-brown chert) and morphology (parallel-sided blade) to other lithics recovered at the northern sites of Ambohiposa and Lakaton’i Anja, it is significantly larger than other recorded lithics on Madagascar. More research is required but this finding suggests that lithic technology may have been more widespread on the island, particularly among coastal communities, than previously thought.

Biocrust-linked changes in soil aggregate stability along a climatic gradient in the Chilean Coastal Range

Abstract. Biological soil crusts (biocrusts) composed of cyanobacteria, bacteria, algae, fungi, lichens, and bryophytes stabilize the soil surface. This effect has mainly been studied in arid climates, where biocrusts constitute the main biological agent to stabilize and connect soil aggregates. Besides, biocrusts are an integral part of the soil surface under Mediterranean and humid climate conditions, mainly covering open spaces in forests and on denuded lands. They often develop after vegetation disturbances, when their ability to compete with vascular plants increases, acting as pioneer communities and affecting the stability of soil aggregates. To better understand how biocrusts mediate changes in soil aggregate stability under different climate conditions, we analyzed soil aggregate samples collected under biocrust communities from four national parks in Chile along a large climatic gradient ranging from (north to south) arid (Pan de Azúcar, PA), semi-arid (Santa Gracia, SG), Mediterranean (La Campana, LC) to humid (Nahuelbuta, NA). Biocrust communities showed a stabilizing effect on the soil aggregates in dry fractions for the three northern sites and the wet aggregates for the southernmost site. Here, permanent vascular plants and higher contents of organic carbon and nitrogen in the soil control aggregate stability more than biocrusts, which are in intense competition with higher plant communities. Moreover, we found an increase in stability for aggregate size classes &lt; 2.0 and 9.5–30.0 mm. The geometric mean diameter of the soil aggregates showed a clear effect due to the climatic gradient, indicating that the aggregate stability presents a log-normal instead of a normal distribution, with a trend of low change between aggregate size fractions. Based on our results, we assume that biocrusts affect the soil structure in all climates. Their role in aggregate stability is masked under humid conditions by higher vegetation and organic matter contents in the topsoil.

Influence of habitat quality and diversity on two populations of Eurasian curlew (Numenius arquata) with contrasting dynamics in Western France

Like most shorebirds in Europe, breeding populations of Eurasian curlew (Numenius arquata) are suffering from habitat loss and degradation mainly caused by changes in agricultural practices. In Deux-Sèvres (France), the number of pairs has gradually declined since the early 2000s in the main, historical breeding site, while a new breeding site has appeared recently 80 kilometres further north with increasing number of pairs through the survey period. Many wheat fields and rare dry grasslands are found in the north, whereas the landscape in the south is mainly composed of tillage plots, hay meadows, and pastures. This study aims to highlight differences in food availability and quality between the two areas. Sample series of ground-dwelling and vegetation-dwelling invertebrates were carried out during three key stages of the species breeding cycle with pitfall traps and sweep nets. Dry grasslands in the north were found to be the most favourable habitat in terms of prey availability for adults and for chicks during the brood-rearing period. Moreover, hay meadows and pastures in the south seemed to be resource-abundant feeding habitats. Therefore, the habitats of the northern site seem to offer a greater abundance of invertebrates and thus a potentially larger food resource than the southern one. It follows that the northern site likely offers better breeding conditions, especially for the growth of chicks. An increase in the area of dry grasslands in the north and the establishment of adapted agricultural management in the south would be favourable for the conservation of local curlew populations.

Development of a universal height response model for transfer of Norway spruce (Picea abies L. Karst) in Fennoscandia

Norway spruce is a major industrial tree species in Fennoscandia and future productivity of the species must be secured by matching the variation in adaptation of the species with suitable sites for optimized performance. An appropriate transfer model for forest reproductive material (FRM) is crucial for regeneration of productive forests in the changing climatic conditions that are predicted to occur in Fennoscandia. We have developed a transfer model for prediction of height of Norway spruce in Norway, Sweden, and Finland, using data acquired from 438 progeny and provenance trials with 1919 genetic entries of local and transferred origins. Transfer of genetic material at a given site was expressed in terms of the difference in daylength (photoperiod) between the site and its origin. This variable best reflected the nonlinear response to transfer that has been commonly reported in previous studies. Apart from the transfer variable, the height prediction model included the age of material when height measurements were acquired, annual temperature sum over 5 °C, precipitation during the vegetation period, and interaction terms between test site and transfer variables. The results show that long northward transfers (4-5° latitude) seem to be optimal for relatively mild sites in southern parts of the countries where growing season is longer, and shorter northward transfers (2-4° latitude) for harsher northern sites with shorter growing seasons. The transfer model also predicts that southward transfers of Norway spruce would result in height growth reductions. The developed model provides foundations for development of common or national recommendations for genetically improving Norway spruce material in Fennoscandia.

Enhanced terrestrial nutrient release during the Devonian emergence and expansion of forests: Evidence from lacustrine phosphorus and geochemical records

The evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, we report geochemical records from a survey of Middle and Late Devonian lacustrine and near-lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery, and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites in Greenland and northern Scotland/Orkney reveal a near-identical net loss of P. Additionally, all sites are temporally proximal to one or more Devonian extinction events, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian/Famennian mass extinction. For all sites, weathering, climate, and redox proxy data, coupled with nutrient input variability, reveal similar geochemical responses as seen in extant lacustrine systems. Orbitally forced climatic cyclicity appears to be the catalyst for all significant terrestrial nutrient pulses, which suggests that expansion of terrestrial plants may be tied to variations in regional and global climate.