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Abstract Delineation of microbial habitats within the soil matrix and characterization of their environments and metabolic processes are crucial to understand soil functioning, yet their experimental identification remains persistently limited. We combined single- and triple-energy X-ray computed microtomography with pore specific allocation of¹³C labeled glucose and subsequent stable isotope probing to demonstrate how long-term disparities in vegetation history modify spatial distribution patterns of soil pore and particulate organic matter drivers of microbial habitats, and to probe bacterial communities populating such habitats. Here we show striking differences between large (30-150 µm Ø) and small (4-10 µm Ø) soil pores in (i) microbial diversity, composition, and life-strategies, (ii) responses to added substrate, (iii) metabolic pathways, and (iv) the processing and fate of labile C. We propose a microbial habitat classification concept based on biogeochemical mechanisms and localization of soil processes and also suggests interventions to mitigate the environmental consequences of agricultural management. 

Abstract Understanding the impact of altitude on leaf hydraulic, gas exchange, and economic traits is crucial for comprehending vegetation properties and ecosystem functioning. This knowledge also helps to elucidate species' functional strategies regarding their vulnerability or resilience to global change effects in alpine environments. Here, we conducted a global study of dataset encompassing leaf hydraulic, gas exchange, and economic traits for 3391 woody species. The results showed that high‐altitude species possessed greater hydraulic safety (K_leafP₅₀), higher water use efficiency (WUE_i) and conservative resource use strategy such as higher leaf mass per area, longer leaf lifespan, lower area‐based leaf nitrogen and phosphorus contents, and lower rates of photosynthesis and dark respiration. Conversely, species at lower altitudes exhibited lower hydraulic safety (K_leafP₅₀), lower water use efficiency (WUE_i) and an acquisitive resource use strategy. These global patterns of leaf traits in relation to altitude reveal the strategies that alpine plants employ for hydraulic safety, water use efficiency, and resource, which have important implications for predicting forest productivity and acclimation to rapid climate change. 

Abstract Microbial carbon (C) use efficiency (CUE) delineates the proportion of organic C used by microorganisms for anabolism and ultimately influences the amount of C sequestered in soils. However, the key factors controlling CUE remain enigmatic, leading to considerable uncertainty in understanding soil C retention and predicting its responses to global change factors. Here, we investigate the global patterns of CUE estimate by stoichiometric modeling in surface soils of natural ecosystems, and examine its associations with temperature, precipitation, plant‐derived C and soil nutrient availability. We found that CUE is determined by the most limiting resource among these four basic environmental resources within specific climate zones (i.e., tropical, temperate, arid, and cold zones). Higher CUE is common in arid and cold zones and corresponds to limitations in temperature, water, and plant‐derived C input, while lower CUE is observed in tropical and temperate zones with widespread limitation of nutrients (e.g., nitrogen or phosphorus) in soil. The contrasting resource limitations among climate zones led to an apparent increase in CUE with increasing latitude. The resource‐specific dependence of CUE implies that soils in high latitudes with arid and cold environments may retain less organic C in the future, as warming and increased precipitation can reduce CUE. In contrast, oligotrophic soils in low latitudes may increase organic C retention, as CUE could be increased with concurrent anthropogenic nutrient inputs. The findings underscore the importance of resource limitations for CUE and suggest asymmetric responses of organic C retention in soils across latitudes to global change factors. 

Abstract Delineation of microbial habitats within the soil matrix and characterization of their environments are crucial to understand soil functioning and carbon (C) cycling. Yet, experimental identification of microbial communities populating specific micro-habitats and assessments of their biochemical properties have been persistently limited. Here we demonstrate how long-term disparities in vegetation history modify spatial distribution patterns and properties of soil pores and particulate organic matter (POM), and show striking differences in bacterial communities populating pores of contrasting sizes in soils from three vegetation systems on the same soil type: an intensive corn (Zea mays L.) rotation, monoculture switchgrass (Panicum virgatum L.), and restored North American prairie. We combined single- and triple-energy X-ray computed microtomography (µCT) with pore specific allocation of 13 C labeled glucose and subsequent stable isotope probing (¹³C-DNA/RNA-SIP) to show that large (30-150 µm Ø) and small (4-10 µm Ø) soil pores differed in (i) microbial diversity, composition, and life-strategies, (ii) responses to added substrate, (iii) metabolic pathways, and (iv) the processing and fate of labile C. Results demonstrate that soil pores created by different plant communities differ in ways that strongly influence microbial composition and activity, and thus impact ecosystem processes such as decomposition, nitrogen processing, and carbon sequestration. A proposed classification scheme may improve biogeochemical models of soil processes and as well suggest interventions to mitigate the environmental consequences of agricultural management. 

Deforestation poses a global threat to biodiversity and its capacity to deliver ecosystem services. Yet, the impacts of deforestation on soil biodiversity and its associated ecosystem services remain virtually unknown. We generated a global dataset including 696 paired-site observations to investigate how native forest conversion to other land uses affects soil properties, biodiversity, and functions associated with the delivery of multiple ecosystem services. The conversion of native forests to plantations, grasslands, and croplands resulted in higher bacterial diversity and more homogeneous fungal communities dominated by pathogens and with a lower abundance of symbionts. Such conversions also resulted in significant reductions in carbon storage, nutrient cycling, and soil functional rates related to organic matter decomposition. Responses of the microbial community to deforestation, including bacterial and fungal diversity and fungal guilds, were predominantly regulated by changes in soil pH and total phosphorus. Moreover, we found that soil fungal diversity and functioning in warmer and wetter native forests is especially vulnerable to deforestation. Our work highlights that the loss of native forests to managed ecosystems poses a major global threat to the biodiversity and functioning of soils and their capacity to deliver ecosystem services. 

Abstract Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phenomenon known as the ‘priming effect’. Despite its global importance, the relationship of the priming effect to mineral weathering and nutrient release remains unclear. Here we show close linkages between mineral weathering in the critical zone and primed decomposition of SOM. Intensified mineral weathering and rock-derived nutrient release are generally coupled with primed SOM decomposition resulting from “triggered” microbial activity. Fluxes of organic matter products decomposed via priming are linearly correlated with weathering congruency. Weathering congruency influences the formation of organo-mineral associations, thereby modulating the accessibility of organic matter to microbial decomposers and, thus, the priming effect. Our study links weathering with primed SOM decomposition, which plays a key role in controlling soil C dynamics in space and time. These connections represent fundamental links between long-term lithogenic element cycling (= weathering) and rapid turnover of carbon and nutrients (= priming) in soil.