Temperate Forest Sites Research Articles

Vertical Variations in Biogenic Organic Nitrates at Two Temperate Forest Sites

Vertical Variations in Biogenic Organic Nitrates at Two Temperate Forest Sites

How to Find Accurate Terrain and Canopy Height GEDI Footprints in Temperate Forests and Grasslands?

AbstractFiltering approaches on Global Ecosystem Dynamics Investigation (GEDI) data differ considerably across existing studies and it is yet unclear which method is the most effective. We conducted an in‐depth analysis of GEDI's vertical accuracy in mapping terrain and canopy heights across three study sites in temperate forests and grasslands in Spain, California, and New Zealand. We started with unfiltered data (2,081,108 footprints) and describe a workflow for data filtering using Level 2A parameters and for geolocation error mitigation. We found that retaining observations with at least one detected mode eliminates noise more effectively than sensitivity. The accuracy of terrain and canopy height observations depended considerably on the number of modes, beam sensitivity, landcover, and terrain slope. In dense forests, a minimum sensitivity of 0.9 was required, while in areas with sparse vegetation, sensitivity of 0.5 sufficed. Sensitivity greater than 0.9 resulted in an overestimation of canopy height in grasslands, especially on steep slopes, where high sensitivity led to the detection of multiple modes. We suggest excluding observations with more than five modes in grasslands. We found that the most effective strategy for filtering low‐quality observations was to combine the quality flag and difference from TanDEM‐X, striking an optimal balance between eliminating poor‐quality data and preserving a maximum number of high‐quality observations. Positional shifts improved the accuracy of GEDI terrain estimates but not of vegetation height estimates. Our findings guide users to an easy way of processing of GEDI footprints, enabling the use of the most accurate data and leading to more reliable applications.

Plants, fungi, and carabid beetles in temperate forests: both observed and dark diversity depend on habitat availability in space and time

ContextThe loss of ancient forests threatens many species. Effective nature conservation needs information on how forest availability in the surrounding landscape in space and time determines the diversity of multiple taxa.ObjectivesWe explored the relationship between forest availability at different spatiotemporal scales and the diversity of various groups: vascular plants (woody species, ground layer), epiphytes (bryophytes and lichens), fungi (ectomycorrhizal, arbuscular mycorrhizal, pathogenic, saprotrophic), and carabid beetles. Besides the observed diversity, we also estimated dark diversity, i.e. suitable but absent species. Dark diversity is theoretically a sensitive metric in detecting ecosystem conditions as it is typically relatively large and contains susceptible species.MethodsWe recorded the observed diversity by field sampling and soil DNA in 100 temperate ancient old-growth forest sites in southern Estonia; dark diversity was estimated for the same sites using species co-occurrence data. Forest availability estimates were obtained from four topographic maps (1900s-2010s) at the 0.5–5 km radius.ResultsThe biodiversity of forest specialists was higher at larger historical forest availability at the spatial scale of 2–5 km radius. The diversity of light-demanding forest ecotone taxa mainly had negative relationships with young forests on previous agricultural lands (at 0.5–2 km radius). Dark diversity models were often more strongly associated with forest availability than observed diversity models.ConclusionsDark diversity enhances our understanding of how current and historical forest availability affects local biodiversity. As young forests cannot provide suitable habitats for many forest-dwelling species, stable forest habitats must be preserved as source areas to enhance biodiversity.

Arbuscular mycorrhizal fungi affect early phenological stages of three secondary vegetation species in a temperate forest

The relationship between arbuscular mycorrhizal fungi (AMF) and secondary vegetation (SV) species at early phenological stages is critical for the successful establishment of these plants on disturbance sites in temperate forests. The main objective of this research is to evaluate the effect of AMF colonization on the early phenological stages (germination and early growth) of three shrub species present in the SV of a temperate forest in central Mexico. We collected soil from different sites in the Abies religiosa forest in central Mexico. We collected seeds of Acaena elongata, Ageratina glabrata, and Solanum pubigerum. We used a controlled experimental design with pasteurized soil (-AMF treatments) and unpasteurized soil (+ AMF treatments). We monitored germination percentage, growth (shoot and root weight and total biomass), AMF root colonization, and the mycorrhizal response index (MRI) for each plant species. All three species tested benefited by AMF, showing higher germination rates. Shoot and root weight and total biomass were significantly higher in the + AMF treatment. Solanum pubigerum showed greater stem length and Ageratina glabrata showed greater root development due to AMF. Ageratina glabrata and Acaena elongata were the most responsive to AMF as indicated by MRI. This research underscores the critical role of AMF in the early phenological stages of SV and highlights the potential ecological benefits of AMF in supporting plant germination and plant growth. These results suggest that AMF enhance germination and early growth of secondary vegetation species, which can be considered in management plans for forest ecosystems.

General reversal of N-decomposition relationship during long-term decomposition in boreal and temperate forests

Decomposition of dead organic matter is fundamental to carbon (C) and nutrient cycling in terrestrial ecosystems, influencing C fluxes from the biosphere to the atmosphere. Theory predicts and evidence strongly supports that the availability of nitrogen (N) limits litter decomposition. Positive relationships between substrate N concentrations and decomposition have been embedded into ecosystem models. This decomposition paradigm, however, relies on data mostly from short-term studies analyzing controls on early-stage decomposition. We present evidence from three independent long-term decomposition investigations demonstrating that the positive N-decomposition relationship is reversed and becomes negative during later stages of decomposition. First, in a 10-y decomposition experiment across 62 woody species in a temperate forest, leaf litter with higher N concentrations exhibited faster initial decomposition rates but ended up a larger recalcitrant fraction decomposing at a near-zero rate. Second, in a 5-y N-enrichment experiment of two tree species, leaves with experimentally enriched N concentrations had faster decomposition initial rates but ultimately accumulated large slowly decomposing fractions. Measures of amino sugars on harvested litter in two experiments indicated that greater accumulation of microbial residues in N-rich substrates likely contributed to larger slowly decomposing fractions. Finally, a database of 437 measurements from 120 species in 45 boreal and temperate forest sites confirmed that higher N concentrations were associated with a larger slowly decomposing fraction. These results challenge the current treatment of interactions between N and decomposition in many ecosystems and Earth system models and suggest that even the best-supported short-term controls of biogeochemical processes might not predict long-term controls.

Temporal and spatial variability of phloem structure in Picea abies and Fagus sylvatica and its link to climate.

Using a unique 8-year data set (2010-2017) of phloem data, we studied the effect of temperature and precipitation on the phloem anatomy (conduit area, widths of ring, early and late phloem) and xylem-ring width in two coexisting temperate tree species, Picea abies and Fagus sylvatica, from three contrasting European temperate forest sites. Histometric analyses were performed on microcores taken from tree stems in autumn. We found high interannual variability and sensitivity of phloem anatomy and xylem-ring widths to precipitation and temperature; however, the responses were species- and site-specific. The contrasting response of xylem and phloem-ring widths of the same tree species to weather conditions was found at the two Slovenian sites generally well supplied with precipitation, while at the driest Czech site, the influence of weather factors on xylem and phloem ring widths was synchronised. Since widths of mean annual xylem and phloem increments were narrowest at the Czech site, this site is suggested to be most restrictive for the radial growth of both species. By influencing the seasonal patterns of xylem and phloem development, water availability appears to be the most important determinant of tissue- and species-specific responses to local weather conditions.

Evergreen gymnosperm tree abundance drives ground beetle density and community composition in eastern US temperate forests

PurposeSoil invertebrates are abundant and diverse members of forest ecosystems, contributing in large parts to ecosystem functioning. Understanding drivers of soil invertebrate diversity, density, and community composition is critical to inform management practices as forests face rapid changes in land use and climate. Tree community metrics may help predict invertebrate communities due to their large role in shaping microhabitat and soil conditions. Ground beetles are a large family of soil-dwelling invertebrates comprised of multiple functional groups ideal for tying tree communities to invertebrate communities broadly. Methods Here, we evaluated the effects of tree diversity, density, and functional groups on ground beetle (Carabidae) diversity, density, and community composition in four eastern US temperate forest sites in the National Ecological Observatory Network. Results We found little evidence to support our hypothesis that higher tree diversity and density would, respectively, lead to higher diversity and density ground beetle communities. Instead, evergreen tree abundance strongly shaped ground beetle density and community composition. Specifically, evergreen stands contained a lower density of ground beetles than deciduous stands. Similarly, the relative abundance of predatory ground beetles increased as the relative abundance of evergreen trees increased. Conclusions Our results show that the resource environments created by trees with varying leaf habits are a dominant force driving ground beetle community diversity and density patterns and suggest that future research exploring mechanisms driving this pattern could improve our understanding of plant-soil interactions.

Biological nitrogen fixation, diversity and community structure of diazotrophs in two mosses in 25 temperate forests.

Many moss species are associated with nitrogen (N)-fixing bacteria (diazotrophs) that support the N supply of mosses. Our knowledge relates primarily to pristine ecosystems with low atmospheric N input, but knowledge of biological N fixation (BNF) and diazotrophic communities in mosses in temperate forests with high N deposition is limited. We measured BNF rates using the direct stable isotope method and studied the total and potentially active diazotrophic communities in two abundant mosses, Brachythecium rutabulum and Hypnum cupressiforme, both growing on lying deadwood trunks in 25 temperate forest sites. BNF rates in both mosses were similar to those observed in moss species of pristine ecosystems. H. cupressiforme fixed three times more N2 and exhibited lower diazotrophic richness than B. rutabulum. Frankia was the most prominent diazotroph followed by cyanobacteria Nostoc. Manganese, iron, and molybdenum contents in mosses were positively correlated with BNF and diazotrophic communities. Frankia maintained high BNF rates in H. cupressiforme and B. rutabulum even under high chronic N deposition in Central European forests. Moss N concentration and 15 N abundance indicate a rather minor contribution of BNF to the N nutrition of these mosses.

Effects of Urbanization and Forest Fragmentation on Atmospheric Nitrogen Inputs and Ambient Nitrogen Oxide and Ozone Concentrations in Mixed Temperate Forests

AbstractUrban ecosystems around the globe experience greater atmospheric nitrogen (N) deposition compared to rural areas and are particularly vulnerable to fragmentation due to land use change. However, while the influences of urbanization and forest fragmentation on atmospheric inputs to temperate forests have been determined separately, the combined effects of the two changes on temperate forest ecosystems have yet to be assessed. To investigate these combined effects, we deployed throughfall collectors to measure atmospheric N inputs and passive samplers to measure nitrogen oxides (NOx) and ozone (O3) throughout the 2018 and 2019 growing seasons in seven temperate forest sites along an urbanization gradient from Boston to central Massachusetts. We found a positive relationship between the amount of impervious surface area (% ISA) surrounding each site and throughfall nitrate () inputs at the forest edge, with urban edge inputs nearly double the rate at rural edge sites. There were higher rates of inputs in the rural forest interior than edge sites, while urban sites experienced significantly higher concentrations of NOx and O3 both in the interior and at the edge compared to rural sites. Atmospheric N inputs were significantly elevated in the early (May–July) compared to the late (August–November) growing season and concentrations of NOx and O3 were also elevated in the midgrowing season (June–September). Our results demonstrate that together, urbanization and forest fragmentation lead to greater rates of atmospheric N inputs and ambient pollutant concentrations of NOx and O3 in temperate forests of the northeastern U.S.

Higher soil moisture increases microclimate temperature buffering in temperate broadleaf forests

Forest canopies can buffer the understory against temperature extremes, often creating cooler microclimates during warm summer days compared to temperatures outside the forest. The buffering of maximum temperatures in the understory results from a combination of canopy shading and air cooling through soil water evaporation and plant transpiration. Therefore, buffering capacity of forests depends on canopy cover and soil moisture content, which are increasingly affected by more frequent and severe canopy disturbances and soil droughts. The extent to which this buffering will be maintained in future conditions is unclear due to the lack of understanding about the relationship between soil moisture and air temperature buffering in interaction with canopy cover and topographic settings. We explored how soil moisture variability affects temperature offsets between outside and inside the forest on a daily basis, using temperature and soil moisture data from 54 sites in temperate broadleaf forests in Central Europe over four climatically different summer seasons. Daily maximum temperatures in forest understories were on average 2 °C cooler than outside temperatures. The buffering of understory temperatures was more effective when soil moisture was higher, and the offsets were more sensitive to soil moisture on sites with drier soils and on sun-exposed slopes with high topographic heat load. Based on these results, the soil–water limitation to forest temperature buffering will become more prevalent under future warmer conditions and will likely lead to changes in understory communities. Thus, our results highlight the urgent need to include soil moisture in models and predictions of forest microclimate, understory biodiversity and tree regeneration, to provide a more precise estimate of the effects of climate change.

Depth-dependent effects of ericoid mycorrhizal shrubs on soil carbon and nitrogen pools are accentuated under arbuscular mycorrhizal trees.

Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.

Effects of tree density and herbaceous plants on tree seedling survival across the growing and non-growing season in a temperate forest

Tree seedling survival is critical for estimating forest recruitment, but it remain elusive about how neighboring tree’s density and herbaceous plants affect it. To assess the relative importance of tree density and herbaceous plants on tree seedling survival during the growing season and non-growing season, we established a two-year experiment with seedling census and removal of herbaceous plants in both secondary and old-growth temperate forest sites in the temperate forests of northeastern China. A total of 3,443 seedlings in 17 tree species were surveyed in this study. We found that both tree density and herbaceous plants significantly affected tree seedling survival, but the specific effects depended on shade tolerance, seedling growth stage and growing season. Conspecific adult neighbors had significant negative effects on the survival of shade-tolerant seedlings during the growing season, while conspecific seedling densities positively correlated with shade-intolerant seedlings. Herb removal significantly improved the survival of newly germinated and shade-intolerant seedlings during the growing season. Furthermore, we found that the survivals of both newly germinated and established seedlings differed seasonally in response to adult, seedling neighbors and herb removal. Herb removal enhances seedling survival during the non-growing season by offsetting the negative effects of conspecific adult neighbors during the growing season. Our findings provide new evidence for seedlings’ shade tolerance, growth stage and seasonal dependence of density dependence in temperate forests, and highlight the significance of herbaceous plants for seedling survival, an important factor that has been neglected in many previous studies.

Forest Tent Caterpillar Outbreaks Drive Change in Ant Communities in Boreal Forests

Insect outbreaks are major drivers of natural disturbances in forest ecosystems. Outbreaks can have both direct and indirect effects on the composition of soil arthropod communities through canopy opening, nutrient addition and predator-prey interactions. In this study, we aimed to understand the effects of forest tent caterpillar (Malacosoma disstria; FTC) outbreaks through cascading effects on ant communities in both temperate and boreal forests in Canada. Pitfall traps and Berlese funnels were used to compare the ant communities, as well as the surrounding arthropod communities, between control and outbreak sites in boreal and temperate forests (in Quebec, Canada). Using the Sørensen dissimilarity index, we determined the alpha and beta diversity of the ant community. Other arthropods collected in the traps were counted to evaluate the richness and abundance of potential prey for the ants and other potential predators of the FTC. We used an indicator species analysis to examine the species associated with sites defoliated by the outbreak. In the boreal forest, we found that FTC outbreaks caused decreases in species richness and increases in the evenness of ant communities in defoliated sites. In the boreal forest sites, species composition varied significantly between control and outbreak sites. This pattern was driven in part by the presence of other predators. A similar, but weaker pattern was observed in the temperate forest. We saw no changes in the beta diversity in the boreal forest, but did see a significant decrease in the temperate forest between the outbreak sites and the control sites. Ant species in the boreal forest tended to exhibit a more marked preference for either control or previously defoliated sites than species in the temperate forest. Our study showed that disturbances such as insect outbreaks can drive changes in the ant community. While we saw small effects of outbreaks, manipulation experiments using resource addition could help us validate the mechanisms behind these relationships.

Functional variability in specific root respiration translates to autotrophic differences in soil respiration in a temperate deciduous forest

CO2 release from forest soils (Rs) is a prominent flux in the global carbon cycle. Rs is derived from roots (autotrophic respiration, Ra) and microbial (heterotrophic) respiration and is highly dynamic, as it depends on edaphic and environmental conditions as well as root functional traits and microbial community composition. It is unclear how root functional traits affect root and microbial respiration rates; however, their consideration may help parse out the relative contributions of root and microbial respiration to Rs. At a temperate forest site, root systems of 3–4 functional root orders and their surrounding surface soil were carefully excavated and placed into custom trays designed to repeatedly measure Rs in situ on eight temperate tree species that varied in their root functional strategies and mycorrhizal affinity. Rs was measured bi-weekly to monthly for nearly one year using a custom chamber attached to a gas exchange system. Rs varied over time, ranging from 0.3 to 12 µmol m−2 s−1. Comparable root systems of the same species were excised from the soil and specific root respiration rates (Rr) were measured. Rr ranged from 2.5 to 9.0 nmol g−1 s−1 and was negatively correlated with root tissue density and positively related to root tissue nitrogen concentration. Using Rr to estimate Ra, we estimate that Ra accounts for <10%, on average 2–3%, of Rs for individual root systems (averaging 1.2 g dry biomass) housed in surrounding soil (average 1.3 kg dry mass) in situ; thus, Ra was roughly 20 times greater than Rh per unit mass. The contribution of Ra peaked in the fall and coincided with leaf senescence of the forest canopy. A soil-sterilizing experimental treatment designed to help isolate Ra in situ reduced bacterial biomass and shifted fungal community composition, but there was no reduction in Rs of the in-situ root-soil tray systems. The relative Ra to Rs ratio increased with root functional strategies characterized by greater specific root length and tip abundance, but also to greater root tissue density. The ratio of Ra to Rs also increased with warmer soil temperatures and decreased slightly with increasing soil moisture. We discuss how incorporating root functional traits as modulators of the autotrophic contribution to Rs could be considered when modeling total soil CO2 efflux from forests.

Forest Structure and Fine Root Biomass Influence Soil CO2 Efflux in Temperate Forests under Drought

Soil respiration is rarely studied at the landscape scale where forest and soil properties can be important drivers. We performed forest and soil inventories in 150 temperate forest sites in three German landscapes and measured in situ soil CO2 efflux with the soda-lime method in early summer 2018 and 2019. Both years were affected by naturally occurring summer droughts. Our aim was to investigate the impact of forest structural and compositional properties, soil properties and climate on soil CO2 efflux at the landscape. Forest properties explained a large portion of soil CO2 efflux variance (i.e., 14% in 2018 and 20% in 2019), which was comparable or larger than the portion explained by soil properties (i.e., 15% in 2018 and 6% in 2019), and much larger than that of climate. Using Structural Equation Modeling, we found that forest structural properties, i.e., tree density and basal area, were negatively linked to soil CO2 efflux, while forest composition, i.e., conifer share and tree species richness, was not important. Forest structure effects on soil CO2 efflux were either direct or mediated by fine root biomass under dry summer conditions. Summer soil CO2 efflux was positively linked to fine root biomass but not related to total soil organic carbon stocks or climate. Forest structural properties influence soil CO2 efflux under drought events and should be considered when predicting soil respiration at the landscape scale.

Beyond beaver wetlands: The engineering activities of a semi-aquatic mammal mediate the species richness and abundance of terrestrial birds wintering in a temperate forest

The engineering activities of the Eurasian beaver Castor fiber have far-reaching effects on the components of an environment and therefore modify the functioning of the ecosystem. The wetlands thereby created are the most conspicuous effect of beaver activity and attract water-related species. However, there is some evidence suggesting that beavers influence not only aquatic ecosystems but also the terrestrial habitats adjacent to these wetlands and the organisms occurring there. Because the impact of beavers on terrestrial birds is still poorly understood, this study evaluates the assemblage of birds wintering on beaver sites (N = 65) and paired reference sites (N = 65) in temperate forests of central Europe. We investigated the correlations between beaver presence, parameters of wetland areas, terrestrial vegetation characteristics, distance from the water’s edge and bird species richness and abundance. We found a greater species richness and abundance of wintering birds on beaver sites than on watercourses unmodified by this ecosystem engineer (by 38% and 61%, respectively). Species richness and abundance were higher in the terrestrial habitats near the edges of beaver ponds, but for some species this tendency also held in forests growing at some distance from beaver wetlands. Greater species richness was related to beaver presence, but also increased with a more open canopy and greater forest floor diversity, whereas bird abundance was correlated only with canopy openness. The beaver sites attracted primary cavity nesters, secondary cavity nesters and frugivorous species. This study provides evidence that the engineering activities of beavers during the growing season have a delayed cascading effect on the richness and abundance of the bird assemblage in terrestrial habitats in winter. This indicates that beaver ecosystem engineering should be seen as having a potential for carry-over effects, in which the consequences of beaver activity become apparent in subsequent seasons. Birds are considered to be ecological indicators, so our results highlight the importance of beavers for the distribution of terrestrial organisms at the local scale, and therefore the functioning of ecosystems beyond the immediate wetland area.

Import and release of nutrients during the first five years of plant litter decomposition

During the initial stages of leaf and needle litter decomposition, microorganisms face nitrogen (N) and phosphorus (P) scarcity since plant litter is very N- and P-poor compared to microbial biomass. The processes that microorganisms use to cope with the unfavorable stoichiometry, such as transport of nutrients into decomposing litter, are still not fully understood.The aim of the study was to explore the import and release of nutrients (N, P, K, Mn, Ca, and Mg) into and from decomposing Norway spruce (Picea abies Karst) and Scots pine (Pinus silvestris L.) needle litter. For this purpose, we conducted a paired-stand litterbag study at eight temperate and boreal forest sites in Sweden that each have a spruce and a pine stand, over a period of five years.The mass of N in decomposing spruce and pine needle litter increased during the first 172 and 356 days, on average by 19% and 30%, respectively, compared to the initial masses of the element in the litter. The mass of P in pine litter increased during the first 526 days of decomposition, on average by 48%. Net release of N from spruce litter, relative to the initial N amount, only began after 895 days of decomposition. Net release of N and P from pine litter, relative to the initial amounts of the elements, started only after 1097 days. In contrast, K, Mn, Ca, and Mg were released right from the beginning of the decomposition process.The results show that N and P import into decomposing plant litter is a quantitatively important process in temperate and boreal coniferous forests during the first stage of litter decomposition when N and P concentrations are low. Nutrient import alleviates stoichiometric imbalance between the microbial biomass and the litter and likely contributes to microbial nutrient acquisition.

Wood-decay type and fungal guild dominance across a North American log transplant experiment

We incubated 196 large-diameter aspen ( Populus tremuloides ), birch ( Betula papyrifera ), and pine ( Pinus taeda ) logs on the FACE Wood Decomposition Experiment encompassing eight climatically-distinct forest sites in the United States. We sampled dead wood from these large-diameter logs after 2 to 6 y of decomposition and determined wood rot type as a continuous variable using the lignin loss/density loss ratio (L/D) and assessed wood-rotting fungal guilds using high-throughput amplicon sequencing (HTAS) of the ITS-2 marker. We found L/D values in line with a white rot dominance in all three tree species, with pine having lower L/D values than aspen and birch. Based on HTAS data, white rot fungi were the most abundant and diverse wood-rotting fungal guild, and soft rot fungi were more abundant and diverse than brown rot fungi in logs with low L/D values. For aspen and birch logs, decay type was related to the wood density at sampling. For the pine logs, decay type was associated with the balance between white and brown/soft rot fungi abundance and OTU richness. Our results demonstrate that decay type is governed by biotic and abiotic factors, which vary by tree species. • Wood-decay types and wood-rotting fungal guilds were measured in large-diameter decayed logs. • White-rot processes dominated among a wide-range of temperate forest sites. • Decay type was related to the wood decomposition rate for aspen and birch dead wood. • Decay type was associated with wood-rotting fungal guild balance in pine dead wood.

Improved modeling of canopy transpiration for temperate forests by incorporating a LAI-based dynamic parametrization scheme of stomatal slope

The ecosystem-level conductance-photosynthesis models, which represent a linearly coupled relationship between canopy stomatal conductance (Gs) and CO2 assimilation, have been increasingly used for modeling transpiration (Tc). As a key parameter in these models, the slope parameter (G1) has been observed to vary considerably over the seasons in the field, but is often parametrized with a biome-specific temporally constant G1, resulting in large potential uncertainty. Here we hypothesized that G1 varies with leaf area index (LAI) phenology and soil water content (SWC) seasonality, and accurate characterization of G1 seasonality offers an avenue to improve Tc modelling. To test these hypotheses, we first investigated the seasonality of Eddy flux-derived G1 and then explored its relationship with satellite-derived LAI and field-observed SWC seasonality at 12 temperate forest FLUXNET sites across the Northern Hemisphere. Last, we cross-compared the two schemes of model parameterization of G1 for modeling Tc: (1) a constant G1 (FIX) and (2) a dynamic G1 parameterized using the selected variables (DYN). Our results show G1 displays considerable seasonal variations across all sites, with a minimum value in mid-summer. Further variance partitioning analysis demonstrates that the seasonal variations in G1 show direct linkages with LAI phenology rather than SWC seasonality likely associated with leaf aging and ontogeny development. Last, we found relative to the FIX model, the DYN model (using LAI for G1 parameterization) significantly reduced the model uncertainty in terms of RMSE by 24.6 ± 11.8% and 32.0 ± 8.7%, respectively for Gs and Tc at a daily scale. These results collectively improve our understanding of the dynamic pattern and proximate controls of G1 seasonality, and highlight the effectiveness of using remote sensing-derived LAI phenology for improved characterization of G1 seasonality that ultimately contributes to the improved process model simulations of the seasonal dynamics of Gs and Tc across temperate forest landscapes.

Collembola (Hexapoda) of Malaise traps from two localities in Tlaxcala, Mexico

Springtails (Collembola) from two temperate forest sites, “Ejido Los Búfalos” (LB) and “Bosque Mágico de Piedra Canteada, Santuario de la Luciérnaga” (PC), in Tlaxcala state, central Mexico, were sampled monthly with Malaise traps. More than 38,000 specimens from 10 species were collected and studied. Although abundance values between both study sites were highly different, no significant effect of locality and sampling date was found according to a two-way ANOVA unbalanced test because of the high variance between recorded data. Shannon’s diversity index for LB was H’=0.61 and for PC was H’=1.08, with a significant difference in diversity between both sites. Most abundant springtails were Entomobryidae: Seira sp. (n=21,091 individuals in LB and n=6,424 in PC), Americabrya arida (6,214 and 2,860), and Willowsia mexicana (19 and 852); few Neanuridae: Pseudachorutes (241 and 169); Isotomidae: Isotoma (2 and 3); Katiannidae: Polykatianna (45 and 22); and Tomoceridae: Pogonognathellus flavescens (45 and 93). Two genera were only found at PC, Dicyrtomidae: Ptenothrix (31) and Entomobryidae: Lepidocyrtus (4). This is the first study to record abundance values of these high magnitudes for springtails captured with Malaise traps. Results are compared with previous studies at Mexican and French localities, respectively; Entomobryidae was the most abundant family captured with this method