Temperate Oak Forest Research Articles

Microbe-mediated attenuation of soil respiration in response to soil warming in a temperate oak forest

Soil respiration (Rs) in response to climate warming received a wide concern due to its important role in terrestrial ecosystem carbon (C) cycling, but the warming-induced effects of soil microbes on soil respiration are still less understood, especially over time. Our study aims to understand the long-term warming induced effects of soil microbes on Rs. A field soil warming experiment using a completely randomized design was conducted in a naturally regenerated oak forest (Quercus aliena) in central China. Soil warming was executed by infrared heater throughout the period from 2011 to 2015. Our results showed that soil temperature was a main factor in regulating Rs in a temperate oak forest throughout the experiment, while soil water content determined Rs only when a naturally dry year occurred. The positive effect of soil warming on Rs that was observed (i.e., 37.5 to 42.0% in the first two years) gradually diminished in the following three years (i.e., 0.9 to 15.4%). Significant positive warming effects on the temperature sensitivity of Rs (Q10) only occurred in the second year. Continuous soil warming caused the decline in nitrogen (N) availability, with a significant increase in microbial biomass-specific enzyme activities for N-acquisition. The attenuation of microbial biomass increment and the decreased ratio of enzymatic C:N acquisition contributed to the diminished warming effect on Rs over time. Our study suggests that microbe-mediated attenuation of Rs, accompanied by the concomitant decline in soil N availability in response to warming, should be taken into consideration in global C cycle modeling.

Effect of biochar addition on leaf-litter decomposition at soil surface during three years in a warm-temperate secondary deciduous forest, Japan

The addition of biochar to the forest floor should facilitate efficient carbon sequestration. However, little is known about how biochar addition effects litter decomposition, which is related to carbon and nutrient dynamics in forest ecosystems. This study evaluated the effect of biochar addition on leaf litter decomposition in a forest ecosystem. To examine whether leaf litter decomposition was stimulated above and below biochar, litterbag experiments were carried out for about 3 years in a field site where biochar was added at the rate of 0, 5 and 10 t ha−¹ (C0, C5 and C10 plots) to the forest floor in a temperate oak forest, Japan. Biochar addition at C10 significantly enhanced litter decomposition below biochar for 2 years after treatment and above biochar for 1 year after treatment. Litter water content in biochar plots tended to increase under dry conditions. Biochar addition enhanced litter decomposition because of increased microbial activity with increased moisture content and accelerated the decomposition progress rather than changing the decomposition pattern. However, the carbon emission through changing leaf litter decomposition was small when compared with the carbon addition by biochar, indicating that biochar could be an effective material for carbon sequestration in forest ecosystems.

Sprouts of shoot-clipped oak (Quercus alba and Q. robur) germinants show morphological and photosynthetic acclimation to contrasting light environments

Sprouting by woody plants can increase species resilience to disturbance and foster regeneration during periods with little recruitment from seed. Though sprouting often plays a critical role in oak forest regeneration, there is little information available on sprouting capacity and sprout physiology at the seedling stage, particularly for new germinants. This study compared sprouting capacity and sprout photosynthesis of shoot-clipped germinants of two temperate oaks established in contrasting light environments. We studied the North American Quercus alba and the European Q. robur, both are in the section Quercus and appear to share similar biological and ecological requirements. Sprouting capacity for both species was enhanced under high light availability (29% more sprouts per plant), a response not previously noted for oak germinants. Seedling sprouts acclimated to high light with a 34% decrease in leaf area ratio, a 56% increase in leaf mass per area, and a 49% increase in the light-saturated maximum photosynthetic rate. Though both species appeared similarly adapted to shoot loss, a greater sprouting capacity (29% more sprouts per plant) and plant-level net photosynthesis (73% higher) was observed for Q. robur, regardless of light environment. As naturally regenerated oak seedlings in forest understories often experience disturbance or stress resulting in shoot loss or die-back, our results highlight the importance of the light environment during early plant development. Our comparison of temperate oaks from different continents should facilitate exchange of successful stand regeneration practices within the range of temperate oak forests.

Interactive effects of past land use and recent forest management on the understorey community in temperate oak forests in South Sweden

AbstractQuestionsPast agricultural land use and forest management have shaped and influenced the understorey composition in European forests for centuries. We investigated whether understorey vegetation assemblages are affected by (a) legacies from a historical infield/outland agricultural system (i.e., a system with nutrient‐enriched vs nutrient‐depleted areas), (b) recent management intensity (i.e., thinning/felling activities), and (c) the interaction of recent management and potential legacies.LocationOak forests in Skåne, south Sweden.MethodsWe use three vegetation surveys (1983, 1993/94 and 2014) and notes on management and land‐use history, available for 62 permanent 500 m² plots. We conducted linear mixed effect modelling to detect both main and interactive effects of past land use and recent management on understorey diversity measures and vegetation indicator values for light and fertility. We combined nonmetric multidimensional scaling with permutational multivariate analysis of variance and indicator species analysis to detect compositional differences caused by past land use and/or recent management.ResultsUnderstorey diversity was mainly affected by management activities, but the former infield/outland agricultural system was an important determinant of understorey composition. Understorey composition of former infields reflected higher nutrient availability and lower light availability compared to former outland. Past land use and recent management had interactive effects on light‐related understorey variables: for the less intensively managed plots, the outland plots contained more light‐demanding species than the infield plots, while for the more intensively managed plots, the light‐demanding signature of the understorey was similar for infield and outland plots.ConclusionsDifferent intensities of past land use as well as recent forest management influenced the composition of the forest understorey, and interactions were present. Therefore, careful consideration of both the long‐term land‐use history and the more recent disturbances due to forest management are necessary when making future predictions of understorey composition and diversity.

Seasonal variations in the response of soil CO2 efflux to precipitation pulse under mild drought in a temperate oak (Quercus variabilis) forest

Extreme precipitation events are predicted to increase in intensity and duration, with uncertain implications for terrestrial carbon (C) cycling. However, knowledge on the responses of soil CO2 efflux to precipitation pulses in different seasons remains limited. Here we assessed the impacts of episodic precipitation pulses on soil respiration (SR) and its components [heterotrophic respiration (HR) and autotrophic respiration (AR)] under mild drought in different seasons in a temperate oak forest, Central China. Results showed that SR (24 h) increased with elevated precipitation levels, and the estimated precipitation-induced increases in the total amount of SR (3 months) in summer (17.86 g C m−2) and autumn (13.57 g C m−2) were greater than that in spring (9.73 g C m−2) and winter (3.71 g C m−2). Effects of precipitation pulse on HR and AR (24 h) varied with seasons, showing significant positive effects on HR in winter and AR in summer. Precipitation events significantly reduced the proportion of HR in SR in summer and autumn, but not in winter. Across all treatments, post-precipitation soil temperature, pre-precipitation soil moisture, and soil inorganic nitrogen are primarily responsible for the precipitation-induced increases in SR, whereas the stimulated HR after precipitation is largely depended on soil total porosity, pre-precipitation soil moisture, and microbial biomass C. Our study suggests that sporadic precipitation events have differential influences on SR and its components in different seasons. Our findings also emphasize that the importance of incorporating episodic extreme precipitation events and its influence on soil CO2 efflux into the future predictions of forest C cycling under climate change.

Responses of soil respiration to spring drought and precipitation pulse in a temperate oak forest

As a consequence of climate change, a higher frequency of spring drought periods followed by episodic precipitation events is predicted for Central China. Little is known about the effect of drought intensity on the response of soil CO2 efflux to discrete precipitation events in forest ecosystems. A field experiment was conducted to assess the responses of soil CO2 efflux to spring drought and precipitation pulse in an oak forest located at climatic transitional zone in Central China. Soil respiration (SR) and heterotrophic respiration (HR) under 30-day drought showed higher responses to precipitation pulse than those under control and 20- day drought treatments. Regardless of drought intensity, precipitation events of 5, 10, and 20 mm levels significantly increased SR by 86.0, 103.4, and 175.2%, and HR by 108.4, 129.5, and 161.5% when compared with non-water addition plots, respectively. Severe drought treatment (30-day drought) amplified the contribution of HR to SR in response to precipitation pulse (84.5% vs 78.3% for the control). Drought intensity rather than precipitation amount showed substantial influence on total carbon loss through SR and HR. These findings highlight the importance of incorporating both drought intensity and precipitation events and their impacts on soil carbon cycling into future predictions of forest ecosystems under climate change.

Effect of agricultural land-use change on ant dominance hierarchy and food preferences in a temperate oak forest.

BackgroundThe discovery-dominance trade-off is the inverse relationship between the ability of a species to discover resources and the species’ dominance of those resources; a paradigm used to explain species coexistence in ant communities dependent on similar resources. However, factors such as stress (e.g., temperature) or disturbance (e.g., removal of biomass) associated with the change in land use, can modify this trade-off. Here, we aimed to determine the potential effects of land use change on dominance hierarchy, food preferences and on the discovery-dominance trade-off.MethodsAn experiment with baits was used to investigate the dominance hierarchies of ant communities in a temperate mountain habitat in central Mexico. We evaluated the dominance index (DI), food preferences and discovery-dominance trade-offs of ants inhabiting two types of vegetation: a native oak forest and agricultural land resulting from agricultural land use and grazing.ResultsThe ant communities in both environments were comprised of three species of ants (Monomorium minimum, Myrmica mexicana, and Camponotus picipes pilosulus), four morphospecies (Pheidole sp.1 and Pheidole sp.2, Temnothorax sp. and Lasius sp.) and one genus (Formica spp.). All Formicidae showed values of intermediate to low DI, and this factor did not seem to be influenced by the change in land use. Ants in the modified vegetation (i.e., agricultural land) were found to be numerically greater. Overall, a higher number of visits were registered to the tuna bait, although the duration of foraging events to the honey baits was longer. However, foraging times were dependent on the species considered: the generalized Myrmicinae, M. minimum, the ant species with highest DI, foraged for longer periods of time in the agricultural land and on the tuna bait. Meanwhile, the cold-climate specialist Formica spp., with a lower DI, foraged for longer periods of time in the oak (although not significant) and on the honey bait. We found little evidence of the discovery-dominance trade-off; instead, we found considerable diversity in the strategies used by the different species to access resources. This range of strategies is well represented by the generalized Myrmicinae M. minimum, the cold-climate specialists Formica spp. and Temnothorax sp., and the rare species, as the cold climate specialist Lasius sp. (insinuators).ConclusionsOur evaluation shows that transformation of the original habitat does not appear to affect the hierarchical dominance of the ant communities, but it does affect their food preferences. Species with higher DI values such as the generalized Myrmicinae are more skilled at resource acquisition in modified habitats. Our results suggest that change in land use promotes an increase in the diversity of foraging strategies used by different ant species. This diversity may contribute to resource partitioning which favors coexistence.

Plasticity in leaf litter traits partly mitigates the impact of thinning on forest floor carbon cycling

Abstract Reducing stand density by thinning intensification has been emphasized as an efficient strategy of forest adaptation to climate change as it improves stand resistance to drought. Yet, it is still unclear how it could affect litter carbon (C) cycling processes. Recent evidence indicates that the plasticity of an oak tree species can lead to a decline in its leaf litter quality and decomposability following thinning. The consequences for litter decomposition and forest floor C storage at the ecosystem scale remain largely unexplored. In this study, we took advantage of a regional‐scale, multi‐site network of long‐term thinning experiments in temperate oak (Quercus petraea) forests to address this issue. We measured ecosystem properties related to forest floor C cycling in 19 plots across eight experimental sites covering a large gradient of stand density and age. Though we expected thinning to affect in situ litter decomposition by altering oak leaf litter quality, we conducted complementary experiments exploring additional mechanisms, that is alterations of microenvironmental conditions and soil faunal activity. Thinning intensification induced a strong decline in tree canopy leaf area index, above‐ground tree litter production and forest floor decomposition rate in early “aggradation” stage of forest development. This slower litter decomposition was mainly driven by plasticity of oak trees that produced leaf litter of poorer quality and decomposability following thinning, for example, litter richer in secondary metabolites such as condensed tannins. Change in microenvironmental conditions also contributed to the slowdown of litter decomposition, likely as a result of the less buffered microclimate associated with larger tree canopy opening. No change in soil faunal effect induced by thinning was observed. Thinning intensification resulted in a limited decrease in forest floor C stock. Indeed, the slower litter decomposition offset nearly half of the forest floor C loss associated to the reduced litterfall in “aggradation” stage. Our study demonstrated that phenotypic plasticity in leaf litter traits of a dominant tree species can strongly affect ecosystem functioning by slowing forest floor decomposition following thinning intensification, in turn partly mitigating the negative effect of thinning on forest floor C storage.

The ground plot counting method: A valid and reliable assessment tool for quantifying seed production in temperate oak forests?

Masting, or mast-seeding, defined as a synchronized and highly variable seed production from year-to-year within a population of plants, is one of the most common example of pulsed resources in terrestrial ecosystems. In oaks, the dramatic fluctuations of acorn production impact its reproductive success and regeneration, the dynamics of a large diversity of seed consumers that rely on it, and, by cascade effects, the dynamics of the entire forest community. However, reproductive effort is difficult to quantify and there is therefore an urgent need of a reliable assessment of the dynamic of acorn production based on a low-cost, unbiased, and robust tool. One of the most commonly used method, the “visual on-tree” method, is very easy and quick to carry out, but is biased under high seed production or when branches are difficult to see. We here assessed the robustness of an alternative method, the “ground plot” (GP), based on a unique annual ground survey after peak of acorn fall, which has not been tested so far. We compared this method at tree and site levels (10 forests throughout France) with the costly and time-consuming trap acorn collection (TNR) method (used here as a reference method). We show that results from the GP method closely matched with those obtained using the TNR method, which demonstrates the efficiency and robustness of the GP method at both tree and forest site levels. Despite some limitations in specific environmental contexts we review, this GP method offers a powerful tool to quantify acorn production and should be deployed to understand mechanisms underlying oak masting and/or to assess its ecological or economic consequences.

Invasive plants in Minnesota are “joining the locals”: A trait‐based analysis

AbstractQuestionsPredicting which newly arrived species will establish and become invasive is a problem that has long vexed researchers. In a study of cold temperate oak forest stands, we examined two contrasting hypotheses regarding plant functional traits to explain the success of certain non‐native species. Under the “join the locals” hypothesis, successful invaders are expected to share traits with resident species because they employ successful growth strategies under light‐limited understorey conditions. Instead, under the “try harder” hypothesis, successful invaders are expected to have traits different from native species in order to take advantage of unused niche space.LocationMinnesota, USA.MethodsWe examined these two theories using 109 native and 11 non‐native plants in 68 oak forest stands. We focused on traits related to plant establishment and growth, including specific leaf area (SLA), leaf carbon‐to‐nitrogen ratio (C:N), wood density, plant maximum height, mycorrhizal type, seed mass and growth form. We compared traits of native and non‐native species using ordinations in multidimensional trait space and compared community‐weighted mean (CWM) trait values across sites.ResultsWe found few differences between trait spaces occupied by native and non‐native species. Non‐native species occupied smaller areas of trait space than natives, yet were within that of the native species, indicating similar growth strategies. We observed a higher proportion of non‐native species in sites with higher native woody species CWM SLA and lower CWM C:N. Higher woody CWM SLA was observed in sites with higher soil pH, while lower CWM C:N was found in sites with higher light levels.ConclusionsNon‐native plants in this system have functional traits similar to natives and are therefore “joining the locals.” However, non‐native plants may possess traits toward the acquisitive end of the native plant trait range, as evidenced by higher non‐native plant abundance in high‐resource environments.

Temporal Variations in Soil Profile Carbon and Nitrogen during Three Consecutive Years of 15N Deposition in Temperate Oak and Pine Forest Stands

Experiments using 15N–labeled urea were conducted for three years to assess the effect of N-deposition on soil C and N dynamics under oak (Qa) and pine (Pk) forest stands in natural field conditions. Throughout the experiment, an increase in total C, mineral N, and total N due to N deposition was greater in coniferous forest soils than in deciduous forest soils, while decreasing the pH of both soils as a result of nitrification. Natural 13C abundance of soil samples was interpreted to reveal the physical mixing of new C substrates from leaf-litter with old C substrates. The δ13C of the upper soil layers became more negative, with greater decreases in the Pk soil. However, with time, the lowering of δ13C was better maintained in the Pk soil than in the Qa soil, indicating greater incorporation of new C substrates from leaf-litter decomposition into old SOC pools in the Pk soil compared to the Qa soil. We revealed that an increase in total C and N contents due to N deposition was greater under coniferous forest stands than under deciduous forest stands as a result of greater mixing of new C substrates into the soil profile in this temperate forest.

The larger, the better? Effects of delayed diameter-limit cutting on old-growth attributes and saproxylic beetle diversity in temperate oak forests

Intensive management implies harvesting large, old trees, which reduces the old-growth attributes. This negatively affects biodiversity, especially saproxylic beetles. In managed temperate oak forests, rotation extension induced by increasing the diameter threshold of final harvest by about 10 cm compared to conventional practices (i.e. DBH around 70 cm) might mitigate this negative effect. Here, we used a gradient of the proportion of overmature trees (DBH ≥ 80 cm) among mature trees (DBH ≥ 70 cm) across plots of high oak French forests to test the potential effect of increasing diameter threshold on (1) structural features and (2) species composition and diversity of saproxylic beetles communities. We assessed deadwood and microhabitats availability (i.e. volume/density and diversity) and canopy openness in 81 1-ha plots across eleven French forests. Results highlighted that a larger proportion of overmature trees, for a given density of mature trees, had limited effects on structural features: only cavities density showed a significant positive response, with no cascading effect on cavicolous beetles. Moreover, the proportion of overmature trees had no significant effect on the composition of saproxylic beetles communities (and ecological variables altogether explained only 17% of the composition inertia). By contrast, mature tree density enhanced microhabitat density and indirectly increased the abundance of rare species. Thus, shifting DBH from 70 to 80 cm in high oak forest could have no or limited effect on saproxylic beetles conservation. Improved strategies might rather stem from combining (1) longer rotation extension and (2) less intensive management practices in extended rotation stands.

Habitat suitability prediction for Salamandra infraimmaculata (Caudata: Amphibia) in western Iran based on species distribution modeling

Salamandra infraimmaculata is a member of family Salamandridae that is distributed in Iran, Turkey, and Lebanon. We surveyed habitat suitability predictions for the species in Kurdistan province, Western Iran. Distribution prediction showed excellent performance (area under the curve = 0.962), with temperature seasonality (47.8%) and precipitation of coldest quarter (38.4%) being two main bioclimatic variables predicting species presence. Temperature and precipitation are two dependent variables on which vegetation and habitat type depend. Slopes of the western Zagros Mountains have moist and temperate oak forests that contain many springs. The presence of both oak forests and water resources may allow the establishment of populations of fire salamanders in the region. As the forests are decreasing because of human activities, the amount of suitable habitats for this species is also decreasing. It is necessary to develop and implement conservation programs to protect the oak forests on the western slopes of the Zagros.

A stand-scale paleoecological perspective on temperate oak forest dynamics: Implications for understanding contemporary oak decline

A stand-scale paleoecological perspective on temperate oak forest dynamics: Implications for understanding contemporary oak decline

Plant Diversity, Tree Regeneration, Biomass Production and Carbon Storage in Different Oak Forests on Ridge Tops of Garhwal Himalaya

The present study was conducted on ridge tops of moist temperate Oak forests in Garhwal Himalaya to assess the plant diversity, regeneration, biomass production and carbon assimilation in different Oak forests. For this purpose, three Oak forest types viz., (a) Quercus leucotrichophora or Banj Oak (FT1; between 1,428-2,578 m asl), (b) Quercus floribunda or Moru Oak (FT2; between 2,430-2,697 m asl) and (c) Quercus semecarpifolia or Kharsu Oak (FT3; between 2,418-3,540 m asl) were selected on different ridge tops in Bhagirathi catchment area of Garhwal Himalaya. A total of 91 plant species including 23 trees (8 gymnosperms and 15 angiosperms), 21 shrubs and 47 herbs species belonging to 46 families were recorded from all the ridge top Oak forests. The highest mean tree density (607±33.60 trees ha-1) was observed in Q. floribunda forest with lower mean total basal cover (TBC) value (48.02± 3.67 m2ha-1), whereas highest TBC value (80.16±3.30 m2ha-1) was recorded for Q. semecarpifolia forest, with lowest mean stem density (594±23.43 stems ha-1). The total biomass density (TBD) across three Oak forests ranged between 497.32±83.70 (FT1) and 663.16±93.85 t ha-1 (FT3), while the total carbon density (TCD) values ranged between 228.75±22.27 (FT1) and 304.31±18.12 t ha-1 (FT3). Most of the tree species were found with good regeneration (GR) status (average 45%) in all the forest types whereas, few species were found not regenerating (NR) (average 17%) however, few new recruitments were also recorded. ANOVA (Post-Hoc Tukey’s test at 5% significance level) indicated significant forest-wise differences in TBC, TBD and TCD (in tree layer); family and evenness (in shrub layer only) values, while insignificant differences were noticed in density values of tree, seedling and herb layer.

Nonlinear height–diameter models for three woody, understory species in a temperate oak forest in Hungary

Information about the diameter and the height of woody species is fundamental to developing growth and yield models in forest stands. Ten nonlinear height–diameter functions were fitted and evaluat...

Effects of experimental throughfall reduction and soil warming on fine root biomass and its decomposition in a warm temperate oak forest

Fine root dynamics play a critical role in regulating carbon (C) cycling in terrestrial ecosystems. Examining responses of fine root biomass and its decomposition to altered precipitation pattern and climate warming is crucial to understand terrestrial C dynamics and its feedback to climate change. Fine root biomass and its decomposition rate were investigated in a warm temperate oak forest through a field manipulation experiment with throughfall reduction and soil warming conducted. Throughfall reduction significantly interacted with soil warming in affecting fine root biomass and its decomposition. Throughfall reduction substantially increased fine root biomass and its decomposition in unheated plots, but negative effects occurred in warmed plots. Soil warming significantly enhanced fine root biomass and its decomposition under ambient precipitation, but the opposite effects exhibited under throughfall reduction. Different responses in fine root biomass among different treatments could be largely attributed to soil total nitrogen (N), while fine root decomposition rate was more depended on microbial biomass C and N. Our observations indicate that decreased precipitation may offset the positive effect of soil warming on fine root biomass and decomposition.

Does tree canopy closure moderate the effect of climate warming on plant species composition of temperate Himalayan oak forest?

AbstractQuestionWe ask if there are significant changes in plant species composition after 20 yr of documented temperature increase (~1 °C), and if the temporal changes are different in closed temperate oak forest compared to semi‐open canopy. Answers to these questions may indicate if climate warming and/or canopy closure, controlled by land‐use regime, is the main driver of any documented compositional changes in the forest between 1993 and 2013.LocationPhulchoki Mountain, central Himalaya (Nepal).MethodsWe resampled 64 plots of 100 m2 after 20 yr and recorded all terrestrial vascular plants and percentage canopy cover in each sample plot. We analysed the compositional changes in terms of species abundance, frequency and spatial translocation in relation to atmospheric temperature and canopy cover using univariate and multivariate statistics.ResultsWe find clear changes in the species composition, with abundance of almost half of the studied species having increased and one‐quarter of the species having decreased over the past two decades. The changes vary among life forms: trees increased, whereas decreasing species were mainly herbaceous or shrubs. Similarly, shade‐tolerant species increased, whereas those adapted to open habitat decreased. The compositional changes are mainly explained through the increased regional temperature, with a significant buffering effect of tree canopy cover. A significant increase in low‐elevation (warm‐adapted) species is detected, but this thermophilization is only found in the semi‐open forest.ConclusionsFine‐scale temporal changes in the temperate oak forests are mainly driven by macroclimate warming, although change in land‐use regime also has a profound direct effect by governing canopy closure that, in turn, moderates the effect of climate warming. Tree canopy cover governs the relative abundances of different species based on their adaptive characteristics, such as shade tolerance and life‐form traits. The magnitude of the temporal vegetation change would therefore be dependent on both the degree of regional climate warming and forest canopy closure.

Cellulose and hemicellulose decomposition by forest soil bacteria proceeds by the action of structurally variable enzymatic systems.

Evidence shows that bacteria contribute actively to the decomposition of cellulose and hemicellulose in forest soil; however, their role in this process is still unclear. Here we performed the screening and identification of bacteria showing potential cellulolytic activity from litter and organic soil of a temperate oak forest. The genomes of three cellulolytic isolates previously described as abundant in this ecosystem were sequenced and their proteomes were characterized during the growth on plant biomass and on microcrystalline cellulose. Pedobacter and Mucilaginibacter showed complex enzymatic systems containing highly diverse carbohydrate-active enzymes for the degradation of cellulose and hemicellulose, which were functionally redundant for endoglucanases, β-glucosidases, endoxylanases, β-xylosidases, mannosidases and carbohydrate-binding modules. Luteibacter did not express any glycosyl hydrolases traditionally recognized as cellulases. Instead, cellulose decomposition was likely performed by an expressed GH23 family protein containing a cellulose-binding domain. Interestingly, the presence of plant lignocellulose as well as crystalline cellulose both trigger the production of a wide set of hydrolytic proteins including cellulases, hemicellulases and other glycosyl hydrolases. Our findings highlight the extensive and unexplored structural diversity of enzymatic systems in cellulolytic soil bacteria and indicate the roles of multiple abundant bacterial taxa in the decomposition of cellulose and other plant polysaccharides.

Wood phenology, not carbon input, controls the interannual variability of wood growth in a temperate oak forest

Although the analysis of flux data has increased our understanding of the interannual variability of carbon inputs into forest ecosystems, we still know little about the determinants of wood growth. Here, we aimed to identify which drivers control the interannual variability of wood growth in a mesic temperate deciduous forest. We analysed a 9-yr time series of carbon fluxes and aboveground wood growth (AWG), reconstructed at a weekly time-scale through the combination of dendrometer and wood density data. Carbon inputs and AWG anomalies appeared to be uncorrelated from the seasonal to interannual scales. More than 90% of the interannual variability of AWG was explained by a combination of the growth intensity during a first 'critical period' of the wood growing season, occurring close to the seasonal maximum, and the timing of the first summer growth halt. Both atmospheric and soil water stress exerted a strong control on the interannual variability of AWG at the study site, despite its mesic conditions, whilst not affecting carbon inputs. Carbon sink activity, not carbon inputs, determined the interannual variations in wood growth at the study site. Our results provide a functional understanding of the dependence of radial growth on precipitation observed in dendrological studies.