Decomposition of organic matter strongly influences ecosystem carbon storage 1 . In Earth-system models, climate is a predominant control on the decomposition rates of organic matter [2][3][4][5] . This assumption is based on the mean response of decomposition to climate, yet there is a growing appreciation in other areas of global change science that projections based on mean responses can be irrelevant and misleading 6,7 . We test whether climate controls on the decomposition rate of dead wood-a carbon stock estimated to represent 73 ± 6 Pg carbon globally 8 -are sensitive to the spatial scale from which they are inferred. We show that the common assumption that climate is a predominant control on decomposition is supported only when local-scale variation is aggregated into mean values. Disaggregated data instead reveal that local-scale factors explain 73% of the variation in wood decomposition, and climate only 28%. Further, the temperature sensitivity of decomposition estimated from local versus mean analyses is 1.3-times greater. Fundamental issues with mean correlations were highlighted decades ago 9,10 , yet mean climate-decomposition relationships are used to generate simulations that inform management and adaptation under environmental change. Our results suggest that to predict accurately how decomposition will respond to climate change, models must account for local-scale factors that control regional dynamics.Climate is traditionally thought to be the predominant control on decomposition rates at global and regional scales, with biotic factors controlling only local rates 2,4 . Biotic factors are divided into decomposer organisms, such as soil microbes, and the quality (for example, chemical composition) of the plant litter they decompose. Recent work suggests that litter quality may be more important than climate in controlling decomposition rates across biomes worldwide 3,11 , but the influence of decomposer organisms is still assumed limited across broad climate gradients 12 . A core reason for this assumption is that climate is considered a primary control on the activity of decomposers. As such, across climate gradients, mean temperature and moisture availability are assumed to explain much of the variation in the activity of decomposer organisms and hence decomposition rates of organic matter. These climate-decomposition relationships are used to parameterize and evaluate Earth-system models 13 . It is therefore important to test the assumption that climate drives decomposer activities because proper understanding of these activities is needed to inform model projections such as carbon cycle-climate feedbacks 1,14 .Climate-decomposition relationships are typically developed from regional to global studies that use the mean response of decomposition to climate and litter quality drivers [2][3][4][5] . There is growing awareness in other areas of global change science that using mean responses masks the fine-scale variation required to understand effects of environmental change 6,7 , although the...

Soil biota play key roles in the functioning of terrestrial ecosystems, however, compared to our knowledge of above-ground plant and animal diversity, the biodiversity found in soils remains largely uncharacterized. Here, we present an assessment of soil biodiversity and biogeographic patterns across Central Park in New York City that spanned all three domains of life, demonstrating that even an urban, managed system harbours large amounts of undescribed soil biodiversity. Despite high variability across the Park, below-ground diversity patterns were predictable based on soil characteristics, with prokaryotic and eukaryotic communities exhibiting overlapping biogeographic patterns. Further, Central Park soils harboured nearly as many distinct soil microbial phylotypes and types of soil communities as we found in biomes across the globe (including arctic, tropical and desert soils). This integrated cross-domain investigation highlights that the amount and patterning of novel and uncharacterized diversity at a single urban location matches that observed across natural ecosystems spanning multiple biomes and continents.

Abstract. Resilient, productive soils are necessary to sustainably intensify agriculture to increase yields while minimizing environmental harm. To conserve and regenerate productive soils, the need to maintain and build soil organic matter (SOM) has received considerable attention. Although SOM is considered key to soil health, its relationship with yield is contested because of local-scale differences in soils, climate, and farming systems. There is a need to quantify this relationship to set a general framework for how soil management could potentially contribute to the goals of sustainable intensification. We developed a quantitative model exploring how SOM relates to crop yield potential of maize and wheat in light of co-varying factors of management, soil type, and climate. We found that yields of these two crops are on average greater with higher concentrations of SOC (soil organic carbon). However, yield increases level off at ∼2 % SOC. Nevertheless, approximately two-thirds of the world's cultivated maize and wheat lands currently have SOC contents of less than 2 %. Using this regression relationship developed from published empirical data, we then estimated how an increase in SOC concentrations up to regionally specific targets could potentially help reduce reliance on nitrogen (N) fertilizer and help close global yield gaps. Potential N fertilizer reductions associated with increasing SOC amount to 7 % and 5 % of global N fertilizer inputs across maize and wheat fields, respectively. Potential yield increases of 10±11 % (mean ± SD) for maize and 23±37 % for wheat amount to 32 % of the projected yield gap for maize and 60 % of that for wheat. Our analysis provides a global-level prediction for relating SOC to crop yields. Further work employing similar approaches to regional and local data, coupled with experimental work to disentangle causative effects of SOC on yield and vice versa, is needed to provide practical prescriptions to incentivize soil management for sustainable intensification.

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Abstract. Resilient, productive soils are necessary to sustainably intensify agriculture to increase yields while minimizing environmental harm. To conserve and regenerate productive soils, the need to build and maintain soil organic matter (SOM) has received considerable attention. Although SOM is considered key to soil health, its relationship with yield is contested because of local-scale differences in soils, climate, and farming systems. There is a need to quantify this relationship to set a general framework for how soil management could potentially contribute to the goals of sustainable intensification. We developed a quantitative model exploring how SOM relates to crop yield potential of maize and wheat in light of co-varying factors of management, soil type, and climate. We found that yields of these two crops are on average greater with higher concentrations of SOC. However, yield increases level off at ~ 2 % SOC. Nevertheless, approximately two thirds of the world's cultivated maize and wheat lands currently have SOC contents of less than 2 %. Using this regression relationship developed from published empirical data, we then estimated how an increase in SOC concentrations up to regionally-specific targets could potentially help reduce reliance on nitrogen (N) fertilizer and help close global yield gaps. Potential N fertilizer reductions associated with increasing SOC amount to 7 % and 5 % of global N fertilizer inputs across maize and wheat fields, respectively. Potential yield increases of 10 ± 11 % (mean ± SD) for maize and 23 ± 37 % for wheat amount to 32 % of the projected yield gap for maize and 60 % of that for wheat. Our analysis provides a global-level prediction for relating SOC to crop yields. Further work employing similar approaches to regional and local data, coupled with experimental work to disentangle causative effects of SOC on yield and vice-versa, are needed to provide practical prescriptions to incentivize soil management for sustainable intensification.

The consequences of deforestation for aboveground biodiversity have been a scientific and political concern for decades. In contrast, despite being a dominant component of biodiversity that is essential to the functioning of ecosystems, the responses of belowground biodiversity to forest removal have received less attention. Single-site studies suggest that soil microbes can be highly responsive to forest removal, but responses are highly variable, with negligible effects in some regions. Using high throughput sequencing, we characterize the effects of deforestation on microbial communities across multiple biomes and explore what determines the vulnerability of microbial communities to this vegetative change. We reveal consistent directional trends in the microbial community response, yet the magnitude of this vegetation effect varied between sites, and was explained strongly by soil texture. In sandy sites, the difference in vegetation type caused shifts in a suite of edaphic characteristics, driving substantial differences in microbial community composition. In contrast, fine-textured soil buffered microbes against these effects and there were minimal differences between communities in forest and grassland soil. These microbial community changes were associated with distinct changes in the microbial catabolic profile, placing community changes in an ecosystem functioning context. The universal nature of these patterns allows us to predict where deforestation will have the strongest effects on soil biodiversity, and how these effects could be mitigated.

Summary1. Mature urban trees improve air quality, reduce storm water run-off and sequester carbon. Municipal agencies establish forests of native juvenile trees to enhance these and other ecosystem services to cities. Little data exist, however, regarding whether these trees will form mature, native forests. 2. We review urban forestry research that deals specifically with the growth, survival and recruitment of new native urban forests and use these data to identify knowledge gaps and propose research needed to create and maintain native urban forests. 3. Experimental urban forestry studies are few and most are of durations ≤5 years, shorter than the 10-25 year time frame required to understand forest stand dynamics. Studies capturing initial dynamics of urban afforestation (≤5 years) identify invasive species as the primary threat to native tree establishment. Data exploring longer-term dynamics are needed to evaluate whether early-stage afforestation dynamics can be used to infer the composition and function of mature urban forests. 4. Synthesis and applications. Urban afforestation approaches -from natural colonization to large-scale plantings -represent a trade-off in cost vs. efficacy for establishing native forests. A major cost-saving strategy would be to determine whether exotics and natives can co-exist and provide the intended ecosystem services.

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