Summary1. Plant functional traits have revealed trade-offs related to life-history adaptations, geographical distributions, and ecosystem processes. Fine roots are essential in plant resource acquisition and play an important role in soil carbon cycling. Nonetheless, root trait variation is still poorly quantified and rarely related to the rest of the plant. 2. We examined chemical and morphological traits of 34 temperate arbuscular mycorrhizal tree species, representing three main angiosperm clades (super-orders asterid, magnoliid and rosid). We tested to what extent fine root chemical and morphological traits were correlated similarly to the leaf economical spectrum (LES) or were structured by ancestral affiliations among species. 3. Root traits did not display the same trade-offs as leaves (e.g. specific root length was not correlated with root N, whereas specific leaf area was correlated with leaf N). Moreover, 75% of below-ground traits were phylogenetically structured according to Pagel's k and Abouheif's C mean autocorrelation tests, as opposed to 28% of above-ground traits. Magnoliids showed thicker, less branched roots than asterids or rosids, but rosid roots exhibited lower N and higher non-acid-hydrolysable (e.g. lignin) content than other species. In contrast, leaf traits did not differ significantly among super-orders. At the whole-tree level, chemical traits such as nitrogen tissue content and lignin content were correlated between above and below-ground organs. 4. The distribution of root traits in woody temperate trees was better explained by shared ancestry than by the nutrient content and structural trade-offs expected by the LES hypothesis. Root chemistry and morphology differed substantially among species belonging to different super-orders, suggesting deep divergences in resource acquisition strategies among major angiosperm groups. Although we found partial support for the idea of whole-plant integration based on corresponding nitrogen content across all organs (i.e. a plant economics spectrum), our study stresses phylogenetic affiliation as the primary driver of root trait distributions among angiosperms, a pattern that could be easily overlooked based solely on above-ground observations.

Although northern temperate forests are generally not considered phosphorus (P) limited, ecosystem P limitation may occur on highly weathered or strongly acidic soils where bioavailable inorganic P is low. In such environments, soil organisms may compensate by increasing the utilization of organic P via the production of extracellular enzymes to prevent limitation. In this study, we experimentally increased available P and/or pH in several acidic eastern deciduous forests underlain by glaciated and unglaciated soils in eastern Ohio, USA. We hypothesized that where inorganic P is low; soil microbes are able to access organic P by increasing production of phosphatase enzymes, thereby overcoming biogeochemical P limitations. We measured surface soil for: available P pools, N mineralization and nitrification rates, total C and N, enzymes responsible for C, N, and P hydrolysis, and microbial community composition (PLFA). Increasing surface soil pH a whole unit had little effect on microbial community composition, but increased N cycling rates in unglaciated soils. Phosphorus additions suppressed phosphatase activities over 60% in the unglaciated soils but were unchanged in the glaciated soils. All treatments had minimal influence on microbial biomass, but available pools of P strongly correlated with microbial composition. Microbes may be dependent on sources of organic P in some forest ecosystems and from a microbial perspective soil pH might be less important overall than P availability. Although our sampling was conducted less than 1 year after treatment initiation, microbial community composition was strongly influenced by available P pools and these effects may be greater than shortterm increases in soil pH.

This study involved in vitro assays of peat soil to investigate the occurrence, importance and potential mechanism(s) of anaerobic methane oxidation (AOM) in several northern peatlands ranging from ombrotrophic bog to minerotrophic fen. Although strong evidence suggests that AOM is linked to sulfate reduction in marine sediments, very little is known about AOM in freshwater systems such as northern peatlands, which have large methane (CH 4 ) production and are a significant source of atmospheric CH 4 . Our results showed a mean net AOM rate of 17 ± 2.6 nmol kg −1 s −1 with a maximum rate of 176 nmol kg −1 s −1 for a minerotrophic fen in central New York. AOM was demonstrated with three independent methods to verify our results: (a) additions of methanogenic inhibitors, (b) stable isotope enrichment ( 13 C-CH 4 ), and (c) natural abundance stable isotope analysis ( 13 C-CH 4 ). These experiments confirmed that AOM occurs simultaneously with methanogenesis, consumes a significant portion of gross CH 4 production, and significantly fractionates C isotopes (∼ −12‰). Experiments using a variety of potential electron acceptors demonstrated that Fe(III) and SO 2− 4 are not quantitatively important, while the role of NO − 3 is uncertain and deserves more attention. The exact mechanism(s) for AOM in peat soils remains unclear; however the AOM rates reported in this study are similar to those reported for CH 4 production and aerobic CH 4 oxidation in northern peatlands, suggesting that AOM may be an important control on CH 4 fluxes in northern peatland ecosystems.

Abstract.Despite a large body of literature on microbial anaerobic oxidation of methane (AOM) in marine sediments and saline waters and its importance to the global methane (CH 4 ) cycle, until recently little work has addressed the potential occurrence and importance of AOM in non-marine systems. This is particularly true for peatlands, which represent both a massive sink for atmospheric CO 2 and a significant source of atmospheric CH 4 . Our knowledge of this process in peatlands is inherently limited by the methods used to study CH 4 dynamics in soil and sediment and the assumption that there are no anaerobic sinks for CH 4 in these systems. Studies suggest that AOM is CH 4 -limited and difficult to detect in potential CH 4 production assays against a background of CH 4 production. In situ rates also might be elusive due to background rates of aerobic CH 4 oxidation and the difficulty in separating net and gross process rates. Conclusive evidence for the electron acceptor in this process has not been presented. Nitrate and sulfate are both plausible and favorable electron acceptors, as seen in other systems, but there exist theoretical issues related to the availability of these ions in peatlands and only circumstantial evidence suggests that these pathways are important. Iron cycling is important in many wetland systems, but recent evidence does not support the notion of CH 4 oxidation via dissimilatory Fe(III) reduction or a CH 4 oxidizing archaea in consortium with an Fe(III) reducer. Calculations based on published rates demonstrate that AOM might be a significant and underappreciated constraint on the global CH 4 cycle, although much about the process is unknown, in vitro rates may not relate well to in situ rates, and projections based on those rates are fraught with uncertainty. We suggest electron transfer mechanisms, C flow and pathways, and quantifying in situ peatland AOM rates as the highest priority topics for future research.