Continentality Research Articles

Patterns of tree species diversity in relation to climatic factors on the Sierra Madre Occidental, Mexico.

Biological diversity can be defined as variability among living organisms from all sources, including terrestrial organisms, marine and other aquatic ecosystems, and the ecological complexes which they are part of. This includes diversity within species, between species, and of ecosystems. Numerous diversity indices combine richness and evenness in a single expression, and several climate-based explanations have been proposed to explain broad-scale diversity patterns. However, climate-based water-energy dynamics appears to be an essential factor that determines patterns of diversity. The Mexican Sierra Madre Occidental occupies an area of about 29 million hectares and is located between the Neotropical and Holarctic ecozones. It shelters a high diversity of flora, including 24 different species of Pinus (ca. 22% on the whole), 54 species of Quercus (ca. 9–14%), 7 species of Arbutus (ca. 50%) and many other trees species. The objectives of this study were to model how tree species diversity is related to climatic and geographic factors and stand density and to test the Metabolic Theory, Productivity-Diversity Hypothesis, Physiological Tolerance Hypothesis, Mid-Domain Effect, and the Water-Energy Dynamic Theory on the Sierra Madre Occidental, Durango. The results supported the Productivity-Diversity Hypothesis, Physiological Tolerance Hypothesis and Water-Energy Dynamic Theory, but not the Mid-Domain Effect or Metabolic Theory. The annual aridity index was the variable most closely related to the diversity indices analyzed. Contemporary climate was found to have moderate to strong effects on the minimum, median and maximum tree species diversity. Because water-energy dynamics provided a satisfactory explanation for the patterns of minimum, median and maximum diversity, an understanding of this factor is critical to future biodiversity research. Quantile regression of the data showed that the three diversity parameters of tree species are generally higher in cold, humid temperate climates than in dry, hot climates.

Production of strawberry (Fragaria x Ananassa Duch.) in the mother plantation in a sand substrate

In the fruit growing of humid and humid continental climate, strawberry represents an important fruit species in the group of berry fruit cultures. Permanent efforts of science and practice for improvement in production of strawberries, with a special emphasis on improving the quality of its fruits, gave special attention to the production of rosettes. The aim of this study is to examine the possibility of producing fresh rosettes of strawberries in the mother plantation in a sand substrate. Planting material, suitable for planting in summer, is provided by direct rooting of rosettes in the sand substrate. Vegetative growth and the quality of rosettes were examined in six cultivars of the June-bearing garden strawberry (Fragaria ananassa Duch.): ‘Honeoye’, ‘Chandler’, ‘Cortina’, ‘Marmolada’, ‘Idea’ and ‘Senga Sengana’. The highest number of runners and rosettes per plant was recorded by ‘Honeoye’. The lowest vigor and the lowest number of rosettes per plant were recorded by ‘Senga Sengana’. The highest quality of primary and secondary rosettes was recorded by ‘Senga Sengana’. The 3rd node rosettes are not used for summer planting of fresh strawberries due to low quality. This way of production, by direct rooting in the mother plantation in a sand substrate, allows obtaining seedlings with developed root system, prepared for planting during the summer months. Therewith, it is more economical and less expensive way of production in comparison with others.

Improved snow-cover model for multi-annual simulations with the STICS crop model under cold, humid continental climates

The objective of this study was to evaluate and improve existing simple snow-cover models to pre-process weather data for improving simulations of soil temperature, soil moisture content, and crop growth under cold, humid continental climates using a crop model. Three snow-cover models were calibrated using readily available input data (minimum and maximum daily air temperature and precipitation) and were evaluated using several data sets from across eastern Canada. The snow-cover model providing the best validation results (model efficiency=0.89) was then used to pre-process climate data used to run the STICS crop model over 3 yr at two sites (Quebec City, QC, and Ottawa, ON). Three output variables (shoot biomass, soil temperature at two depths, and soil moisture content at two depths) were compared with field measurements when the STICS model was used with and without pre-processing of the weather data with the snow-cover model. When climate data were pre-processed with the snow-cover model, the performance of STICS in simulating soil temperature was significantly improved during the non-growing season (November–April). Model performance during the growing season (May–October) was thus similar to the model performance during the non-growing season, with a small bias (<0.5°C), a root mean square error (RMSE) of about 2°C, and a model efficiency higher than 0.93. The simulation of soil moisture with STICS also improved slightly with the use of the snow-cover model, but model performance was better in the 15-to-30-cm soil layer than in the 0-to-15-cm layer (RMSE of about 2vol.% in the 15-to-30-cm layer versus 3.5vol.% in the 0-to-15-cm layer). The prediction of plant shoot dry biomass (spring wheat and corn) with STICS was affected little by the use of the snow-cover model and was good with and without the snow-cover model (RMSE of 1.1tha−1). This study showed that STICS can run over several years in the eastern Canada pedo-climatic context without affecting model performance in predicting crop biomass and the two main soil variables. This result opens new opportunities for using STICS or other crop models under a northern climate characterized by a short growing season and significant snow cover during the non-growing season. This result also offers a foundation for future studies aimed at simulating the winter survival of perennial crops as well as annual water and nitrogen cycling in agricultural soils.

Modeling Subsurface Hillslope Runoff Dominated by Preferential Flow: One‐ vs. Two‐Dimensional Approximation

Shallow saturated subsurface flow, frequently observed on hillslopes of headwater catchments in humid temperate climates, often dominates hydrologic responses of the catchments to major rainfall events. Typically, these responses are significantly affected by the presence of preferential flow. Reliable prediction of runoff from hillslope soils under such conditions remains a challenge. In this study, two approaches to modeling hillslope responses to rainstorms, which differ in dimensionality and thus also in the complexity of geometric, material, and boundary conditions, were tested and used on the hillslope discharge data observed in an experimental trench. In the one‐dimensional (1D) approach, 1D variably saturated vertical soil water flow is combined with 1D lateral saturated flow above the soil–bedrock interface. In this approach, vertical flow is modeled by means of a dual‐continuum concept involving two coupled Richards' equations (representing flow in the soil matrix and in the preferential pathways), while lateral flow is described by the diffusion wave equation. In the two‐dimensional (2D) approach, the movement of water in a variably saturated hillslope segment is modeled as vertical planar flow (i.e., the vertical and lateral flow components are fully integrated into one flow system). Similar to the 1D approach, the preferential flow effects are implemented in the 2D model by means of the dual‐continuum concept. The two model approaches (1D and 2D) resulted in similar hillslope discharge hydrographs, characterized by short‐term runoff peaks followed by zero‐discharge periods, but the 2D model showed closer agreement between observed and simulated soil water pressure heads near the trench. The sensitivity analysis of soil and bedrock properties confirmed a significant influence of the bedrock saturated hydraulic conductivity on simulated hillslope discharge. The simpler 1D approach, based on the combination of 1D vertical flow and 1D lateral flow, was found to provide a useful approximation of the more complex and flexible 2D system and to be far more efficient in terms of computing time.

Influence of sky view factor on outdoor thermal environment and physiological equivalent temperature.

Sky view factor (SVF), which is an indicator of urban canyon geometry, affects the surface energy balance, local air circulation, and outdoor thermal comfort. This study focused on a continuous and long-term meteorological observation system to investigate the effects of SVF on outdoor thermal conditions and physiological equivalent temperature (PET) in the central business district (CBD) of Beijing (which is located within Chaoyang District), specifically addressed current knowledge gaps for SVF-PET relationships in cities with typical continental/microthermal climates. An urban sub-domain scale model and the RayMan model were used to diagnose wind fields and to calculate SVF and long-term PET, respectively. Analytical results show that the extent of shading contributes to variations in thermal perception distribution. Highly shaded areas (SVF <0.3) typically exhibit less frequent hot conditions during summer, while enduring longer periods of cold discomfort in winter than moderately shaded areas (0.3< SVF <0.5) and slightly shaded areas (SVF >0.5), and vice versa. Because Beijing has a monsoon-influenced humid continental climate with hot summers and long, cold, windy, and dry winters, a design project that ideally provides moderate shading should be planned to balance hot discomfort in summer and cold discomfort in winter, which effectively prolongs the comfort periods in outdoor spaces throughout the entire year. This research indicate that climate zone characteristics, urban environmental conditions, and thermal comfort requirements of residents must be accounted for in local-scale scientific planning and design, i.e., for urban canyon streets and residential estates.

Late cretaceous Arman’ flora of Magadan oblast: Paleoclimatic interpretation

The Arman’ flora belongs to the formation of the same name in the Arman’ River basin and Nel’khandzha-Khasyn interfluve. It includes about 80 fossil plant species. The similarity of this flora to the reliably dated fossil floras of northwestern Kamchatka and the Pekul’nei Range dates it to being Turonian and Coniacian in age, which is corroborated by isotopic (U-Pb and 40Ar/39Ar) dating of the plant-bearing layers. The CLAMP method is used to estimate quantitative climatic variables, according to which the Arman’ flora existed in a temperate humid climate with warm summers and mild winters. This climate is especially similar to the conditions reconstructed from fossil plants of the Turonian Penzhina flora and the Coniacian Kaivayam and Tylpegyrgynai floras of Northeast Asia.

Safely Coupling Livestock and Crop Production Systems: How Rapidly Do Antibiotic Resistance Genes Dissipate in Soil following a Commercial Application of Swine or Dairy Manure?

Animal manures recycled onto crop production land carry antibiotic-resistant bacteria. The present study evaluated the fate in soil of selected genes associated with antibiotic resistance or genetic mobility in field plots cropped to vegetables and managed according to normal farming practice. Referenced to unmanured soil, fertilization with swine or dairy manure increased the relative abundance of the gene targets sul1, erm(B), str(B), int1, and IncW repA. Following manure application in the spring of 2012, gene copy number decayed exponentially, reaching background levels by the fall of 2012. In contrast, gene copy number following manure application in the fall of 2012 or spring of 2013 increased significantly in the weeks following application and then declined. In both cases, the relative abundance of gene copy numbers had not returned to background levels by the fall of 2013. Overall, these results suggest that under conditions characteristic of agriculture in a humid continental climate, a 1-year period following a commercial application of raw manure is sufficient to ensure that an additional soil burden of antibiotic resistance genes approaches background. The relative abundance of several gene targets exceeded background during the growing season following a spring application or an application done the previous fall. Results from the present study reinforce the advisability of treating manure prior to use in crop production systems.

Spatial analysis of annual runoff ratios and their variability across the contiguous U.S.

Summary This study examines the spatial patterns of annual runoff ratios and their variability and identifies the determinants of runoff indices for 238 reference basins with low levels of anthropogenic influence and 1352 non-reference basins with substantial levels of anthropogenic influence. Runoff ratios are high and runoff ratio coefficients of variation (CV) are low in coastal Pacific Northwest and Northeast basins, both humid temperate climates. The most significant variable that influences annual runoff ratio for both basin types is the average annual days of measurable precipitation. Snow percent of total precipitation and minimum watershed elevation are common predictors of runoff ratio for both types of basins. Slope percent and Horton overland flow are significant predictors for reference basin runoff ratio, while average annual precipitation, basin compactness, and dam storage are significant predictors for non-reference basin runoff ratio. The variables most significantly influencing runoff ratio CV in both types of basins are the average annual days of measurable precipitation, the precipitation seasonality index, and the base flow index. Horton overland flow is a significant predictor for reference basins, while minimum watershed elevation is a significant predictor for non-reference basins. Spatial autocorrelation of ordinary least squares estimated residuals are reduced by geographically weighted regression (GWR) for all models in both basin types. This study shows that GWR modeling, which takes into account spatial non-stationarity, can create more accurate representations of runoff ratio variability in both basin types. The spatially-varying coefficient values in GWR models also show local specific relationships between runoff indices and various climatic and landscape factors.

Biodiversidad de Mecoptera en México

Mecoptera are small holometabolous insects with elongate and slender bodies, superficially resembling primitive true flies. They posses a characteristic head and mouthparts structure pronounced to form a rostrum. They are commonly called scorpionflies, because in Panorpidae males the terminal part of the abdomen bears genital structures resembling a hook or scorpion sting. Their active season is brief through the year. Although distributed worldwide, especially in humid temperate and subtropical climates, they are only moderately to scarcely represented in scientific collections. The order comprises about 600 species in 9 families worldwide. In Mexico, 47 species have been recorded. They are comprised mainly in the genera Panorpa (32 species) and Bittacus (9 species) with a widespread distribution, with the rest of species in Kalobittacus, Eremobittacus and Hylobittacus. A brief account of their life cycle and distribution in Mexico are included.

跨地带土壤置换的实验研究

When people did ecological restoration,it was very difficult to achieve the trans-regional soil replacement. Basalt platform is distributed around the Changbai Mountain Nature Reserve. The intrazonality soil( i. e. baijiang soil,peat soil and meadow soil) in the temperate humid climate zone is developed widely on basalt platform,howerer,the zonality soil such as dark brown earth is rare. The mountain brown coniferous forest soil,baijiang soil,peat soil and meadow soil are not in the same physical geographic zone,and there are significant differences in their physical and chemical properties,thus, it is not easy to complete soil replacement directly. In this zone,we could use the synthesis soil which is artificially synthesized with baijiang soil,peat soil and meadow soil to instead of the mountain brown coniferous forest soil. In this study,the baijiang soil,peat soil and meadow soil in the dark brown soil zone in the temperate broadleaved-coniferous mixed forest were used as raw materials,and the mountain brown coniferous forest soil in cold temperate zone in Changbai Mountain Nature Reserve was used as replacement object. Firstly,we completed soil synthesis taking the imitates the natural prototype principle,and then,conducted the experimental research on trans-regional soil replacement and plant growth. The results showed that the differences of soils were significant in the distribution of the content of every soil grain size group( %),humus layer thickness( 10—20 cm),pH( 5. 9—7. 5),and the available nitrogen( N) content( 57. 8—100. 7 g / kg) in the mountain brown coniferous forest soil zone. The limited factors of plant growth were humus layer thickness,pH,and available N content of mountain brown coniferous forest soil. Plant growth condition was better as the humus layer thickness was 40cm,pH was 7. 0 and available N content was 80 mg / kg which were the inflection point value of the mountain brown coniferous forest soil limited factors. Therefore,the inflection point value of the mountain brown coniferous forest soil limited factor was a key to synthesis soil,and it was the basis for physical and chemical indicators of synthesis soil. There were more gravel but less silt and clay on surface soil of the mountain brown coniferous forest soil,the soil texture is gravelly sandy loam. Soil texture of meadow soil was sandy loam soil. There were less gravel but more silt and clay on surface soil of soil texture of baijiang soil,and peat soil was loam. The mountain brown coniferous forest soil and the peat soil were more abundant in organic matter content,however,the baijiang soil and the meadow soil were low. The pH of the mountain brown coniferous forest soil was higher than that of baijiang soil,peat soil and meadow soil. Total N was more abundant in the mountain brown coniferous forest soil than that of other types of soils,but the available N was lower in surface soil of the mountain brown coniferous forest soil. The total and available potassium was the most abundant nutrient in the mountain brown coniferous forest soil. There was no significant different in the total and available phosphorus for the four types of soils. In Changbai Mountain,the mixed soil was made of a quarter of peat soil,a quarter of meadow soil and a half of baijiang soil and the its soil layer thickness was kept about 40 cm,then the pH of the mixed soil was adjusted to neutral by lime. It was the most reasonable solution for replacing the mountain brown coniferous forest soil since the vegetation restoration effect was best and the cost was the lowest to produce the mixed soil.

Testing a new method for sequential silicon extraction on soils of a temperate–humid climate

The importance of silicon (Si) compounds in agriculture and geochemical cycles has received increasing attention over the last decade; however, quantitative data on non-crystalline pedogenic Si phases in soils are still rare. Recently, the authors developed a method for sequential Si extraction from soils, in order to improve the quantification of different Si compounds in soils. The method has been tested on samples of known composition. Here, the method is applied for the first time to complete soil profiles. Six different soil types from south-west Germany that have developed since the end of the last glacial period were selected. Most of the Si in these soils was bound in primary and secondary silicates. In mineral soil horizons, the second-highest proportion of Si was in precipitates of amorphous silica (minerogenic amorphous silica), whereas in some O horizons, the second-most important Si fraction was in biogenic amorphous silica. Topsoil horizons and clayey subsoil horizons of a Luvisol and a Stagnosol especially accumulate amorphous silica. Silicon from bio-opal contributed up to 14% to the total Si in Oa horizons of the studied soils. The smallest amounts of Si were found in the mobile and adsorbed Si fractions. Some methodological limitations are identified and discussed; however, the new sequential method of Si extraction enabled separation of different Si fractions in typical soils of a temperate–humid climate.

Enhancing the regeneration of compacted forest soils by planting black alder in skid lane tracks

Soil compaction due to the use of heavy machinery for timber harvesting has become a widespread problem in forestry. However, only few studies deal with the regeneration of compacted forest soils. In the present study, we examined the potential of accelerating soil regeneration by planting black alder trees (Alnus glutinosa (L.) Gaertn.) in skid lane tracks. In 2003, seedlings were planted into the rut beds of severely compacted skid lanes in two Swiss forest sites. In addition, some of the ruts were filled with compost. In 2009 and 2010, we assessed the success of these measures by analysing physical parameters of soil structure (bulk density, total and coarse porosity and air permeability), root densities and tree growth. Tree growth was exceptionally strong on the skid lanes. Total and coarse soil porosity and air permeability showed significant increase in planted skid lanes as compared to untreated control subplots, approaching values found for untrafficked soil in the immediate vicinity. All soil physical parameters were closely correlated to root mass density. Compost application enhanced tree growth and soil structure regeneration on one site, but had a retarding effect on the other site. Planting black alders has great potential as an environmentally friendly measure to accelerate the structural regeneration of compacted forest soils in temperate humid climates.

Revealing the relative influence of soil and topographic properties on soil water content distribution at the watershed scale in two sites

Summary Soil and topographic properties are two important factors controlling soil water content (SWC) distribution in a horizontal dimension. The objective of this study was to use structural equation modeling (SEM) to reveal the relative influence of soil and topographic properties on SWC distribution at the watershed scale. Experiments were conducted in two representative sites: St. Denis National Wildlife Area (SDNWA) in the Canadian prairie landscape with a humid continental climate, and LaoYeManQu (LYMQ) watershed on the Chinese Loess Plateau with a cold semi-arid environment. Soil water contents were measured along a 576 m long transect at the SDNWA and over an area of 20 ha at the LYMQ. The influences of soil and topographic properties on SWC were determined at various soil layers and under various antecedent soil water conditions. Results showed that soil and topographic properties jointly controlled SWC distribution at the SDNWA, but soil properties contributed more to SWC variability than topographic properties. At the LYMQ, only soil properties dominated SWC distribution. The influences of soil and topographic properties at the SDNWA were stronger under wetter conditions, whereas the influence of soil properties at the LYMQ presented slight differences between different antecedent soil water conditions. The influence of soil properties decreased and then increased with depth from 0–20 cm to 120–140 cm at the SDNWA, whereas the influence of topographic properties at the SDNWA and the influence of soil properties at the LYMQ decreased with depth. This study implied that SWC was a local and nonlocal control in the humid continental climate, whereas only a local control operated in the cold semi-arid environment.

Environmental consequences of rehabilitation of residential buildings in Turkey: A case study of Istanbul

This paper explains a method developed to assess environmental performance achieved by rehabilitation of residential buildings in Turkey. Several measures focussing on a reduction in the heating demand were investigated such as replacement of window and insulation of different elements of building skin. The influence of several building characteristics was moreover examined such as window to wall ratio (WWR), orientation and building age. Another important aspect which affects environmental performance is climate. In the context of this method, rehabilitations were proposed for temperate-humid climates like Istanbul. According to the assessment results, an environmental performance is obtained for all proposed rehabilitations. When proposed rehabilitations are analysed separately, the environmental performance ratios resulting from the rehabilitations of exterior walls and projected floors, roof, window system, and floors above unheated spaces reduce respectively. WWR has the highest effect on the environmental performance ratios obtained by rehabilitations. The effects of building age and orientation are in negligible amounts when compared to that of WWR. In the future, these assessments should be carried out for different climatic regions of Turkey as well. This method can be used to assess existing and new buildings in terms of environmental impacts by architects, contractors, building owners or municipal authorities.

Pedotransfer functions to estimate retention and availability of water in soils of the state of Santa Catarina, Brazil

Studies on water retention and availability are scarce for subtropical or humid temperate climate regions of the southern hemisphere. The aims of this study were to evaluate the relations of the soil physical, chemical, and mineralogical properties with water retention and availability for the generation and validation of continuous point pedotransfer functions (PTFs) for soils of the State of Santa Catarina (SC) in the South of Brazil. Horizons of 44 profiles were sampled in areas under different cover crops and regions of SC, to determine: field capacity (FC, 10 kPa), permanent wilting point (PWP, 1,500 kPa), available water content (AW, by difference), saturated hydraulic conductivity, bulk density, aggregate stability, particle size distribution (seven classes), organic matter content, and particle density. Chemical and mineralogical properties were obtained from the literature. Spearman's rank correlation analysis and path analysis were used in the statistical analyses. The point PTFs for estimation of FC, PWP and AW were generated for the soil surface and subsurface through multiple regression analysis, followed by robust regression analysis, using two sets of predictive variables. Soils with finer texture and/or greater organic matter content retain more moisture, and organic matter is the property that mainly controls the water availability to plants in soil surface horizons. Path analysis was useful in understanding the relationships between soil properties for FC, PWP and AW. The predictive power of the generated PTFs to estimate FC and PWP was good for all horizons, while AW was best estimated by more complex models with better prediction for the surface horizons of soils in Santa Catarina.

Impact of activated charcoal and tannin amendments on microbial biomass and residues in an irrigated sandy soil under arid subtropical conditions

Effects of goat manure application combined with charcoal and tannins, added as feed additives or mixed directly, on microbial biomass, microbial residues and soil organic matter were tested in a 2-year field trial on a sandy soil under Omani irrigated subtropical conditions. Soil microbial biomass C revealed the fastest response to manure application, followed by microbial residue C, estimated on the basis of fungal glucosamine and bacterial muramic acid, and finally soil organic C (SOC), showing the slowest, but still significant response. At the end of the trial, microbial biomass C reached 220 μg g−1 soil, i.e. contents similar to sandy soils in temperate humid climate, and showed a relatively high contribution of saprotrophic fungi, as indicated by an average ergosterol to microbial biomass C ratio of 0.35 % in the manure treatments. The mean fungal C to bacterial C ratio was 0.55, indicating bacterial dominance of microbial residues. This fraction contributed relatively low concentrations of between 20 and 35 % to SOC. Charcoal added to manure increased the SOC content and the soil C/N ratio, but did not affect any of the soil microbial properties analysed. Tannins added to manure reduce the 0.5 M K2SO4-extractable N to N total ratio compared to manure control. These effects occurred regardless of whether charcoal or tannins were supplied as feed additive or directly mixed to the manure.

Problematic urn-shaped fossils from a Paleoproterozoic (2.2 Ga) paleosol in South Africa

Small (0.3–1.8mm long), locally abundant, urn-shaped fossils within surface horizons of a paleosol in the 2.2Ga Hekpoort Formation near Waterval Onder, South Africa, are here described and named Diskagma buttonii Retallack gen. et sp. nov. The fossils are from fresh rock of a deep highway cutting, and have been metamorphosed to upper greenschist facies like their matrix. Despite metamorphic alteration, total organic carbon of the samples was 0.04% and its isotopic composition (δ13C) was −25.6±0.08‰ (two standard deviations) versus Vienna Pee Dee belemnite standard. Organic outlines of the fossils are also accentuated by recystallized berthierine and opaque oxides. The fossils are locally clumped within surface swales of a Vertisol paleosol, identified from characteristic penecontemporaneous deformation (clastic dikes between swales of mukkara structure) and from pronounced geochemical differentiation (phosphorus and copper strain-corrected mass-depletion characteristic of an oxidized biologically active soil). This paleosol's chemical composition is evidence of temperate humid climate (mean annual temperature 11.3±4.4°C, and mean annual precipitation 1489±182mm). Associated paleosols indicate atmospheric CO2 of 6640 (+12,880/−4293)ppm (0.6%) and 0.9–5% atmospheric O2. The best preserved examples of Diskagma are shaped like an urn with a flared rim, and closed below the flare. Observation of hundreds of specimens in thin section reveals substantial variation in growth (elongation) and decay (shredding and deflation). They had a hollow ellipsoidal interior that is unusually devoid of opaque debris, unlike the matrix. Diskagma is superficially comparable with lichens such as Cladonia (Ascomycota) and Geosiphon (Glomeromycota). Definitive reproductive structures remain unknown. They predate the oldest other likely fossil eukaryotes (1.9Ga) and fungi (1.5Ga), and current molecular clock estimates for eukaryotes (1.6Ga) and fungi (1.1Ga). Lichenized actinobacteria are plausible prokaryotic alternatives permitted by molecular clocks. Although biological affinities of Diskagma are uncertain, these fossils reveal the general appearance of Paleoproterozoic life on land.

Weather effects on corn response to in-season nitrogen rates

Xie, M., Tremblay, N., Tremblay, G., Bourgeois, G., Bouroubi, M. Y. and Wei, Z. 2013. Weather effects on corn response to in-season nitrogen rates. Can. J. Plant Sci. 93: 407–417. The response of corn yield to in-season nitrogen rate (ISNR) fertilizer applications in a temperate humid climate is conditioned to a great extent by prevailing weather conditions, which affect nitrogen use efficiency and raise the level of uncertainty for making management decisions. A better understanding of the effects of temperature, expressed as accumulated corn heat units (CHU), and precipitation would help to ensure that a “closer-to-optimal” nitrogen rate is supplied at side-dressing. A meta-analysis was performed using a database of nitrogen response trials conducted from 1997 to 2008 in 60 locations in the corn grain production area of Québec, in conjunction with a weather database. Meta-analysis is a statistical procedure for combining results from a series of studies that is used in many fields of research. It is used to assess treatment effect (also called effect size) in a group of studies or experiments. Corn yield response to ISNR was negatively correlated with overall CHU accumulation, but positively correlated with CHU accumulation before side-dressing. Responses also showed a stronger relationship with cumulative precipitation (PPT) before side-dressing than after side-dressing. High and evenly distributed precipitation before side-dressing tended to increase responses to ISNR. It can be concluded that low CHU, low precipitation and low precipitation evenness before side-dressing reduce the impact of ISNR on corn yield.

Evaluating controls on coupled hydrologic and vegetation dynamics in a humid continental climate watershed using a subsurface‐land surface processes model

Key Points Evaluated relative controls on hydrologic and vegetation fluxes and states Evaluated the coupling strengths between biogeochemical and hydrologic cycles Elucidated patterns of hydrology and vegetation dynamics in a Great Lakes basin

Incorporating weather sensitivity in inventory-based estimates of boreal forest productivity: A meta-analysis of process model results

Weather effects on forest productivity are not normally represented in inventory-based models for carbon accounting. To represent these effects, a meta-analysis was conducted on modeling results of five process models (ecosys, CN-CLASS, Can-IBIS, InTEC and TRIPLEX) as applied to a 6275ha boreal forest landscape in Eastern Canada. Process model results showed that higher air temperature (Ta) caused gains in CO2 uptake in spring, but losses in summer, both of which were corroborated by CO2 fluxes measured by eddy covariance (EC). Seasonal changes in simulated CO2 fluxes and resulting inter-annual variability in NEP corresponded to those derived from EC measurements. Simulated long-term changes in above-ground carbon (AGC) resulting from modeled NEP and disturbance responses were close to those estimated from inventory data. A meta-analysis of model results indicates a robust positive correlation between simulated annual NPP and mean maximum daily air temperature (Tamax) during May–June in four of the process models. We therefore, derived a function to impart climate sensitivity to inventory-based models of NPP: NPP′i=NPPi+9.5 (Tamax −16.5) where NPPi and NPP′i; are the current and temperature-adjusted NPP, 16.5 is the long-term mean Tamax during May–June, and Tamax is that for the current year. The sensitivity of net CO2 exchange to Ta is nonlinear. Although, caution should be exercised while extrapolating this algorithm to regions beyond the conditions studied in this landscape, results of our study are scalable to other regions with a humid continental boreal climate dominated by black spruce. Collectively, such regions comprise one of the largest climatic zones in the 450Mha North American boreal forest ecosystems.