28 research outputs found
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Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage
Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity
An estimate of the number of tropical tree species
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisherâs alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between âŒ40,000 and âŒ53,000, i.e. at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of âŒ19,000â25,000 tree species. Continental Africa is relatively depauperate with a minimum of âŒ4,500â6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa
Carbon-sensitive pedotransfer functions for plant available water
Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (ΞAWHC), while some studies show the ability to substantially increase ΞAWHC through management. The Soil Health Institute\u27s North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (ΞFC) and permanent wilting point (ΞPWP). New pedotransfer functions had predictions of ΞAWHC that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on ΞAWHC. For an increase in SOC of 10 g kgâ1 (1%) in noncalcareous soils, an average increase in ΞAWHC of 3.0 mm 100 mmâ1 soil (0.03 m3 mâ3) on average across all soil texture classes was found. This SOC related increase in ΞAWHC is about double previous estimates. Calcareous soils had an increase in ΞAWHC of 1.2 mm 100 mmâ1 soil associated with a 10 g kgâ1 increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience
The global abundance of tree palms
Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., â„10 cm diameter at breast height) abundance relative to coâoccurring nonâpalm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of longâterm climate stability. Lifeâform diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many nonâtree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of aboveâground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests
Wheat yield and soil properties reveal legacy effects of artificial erosion and amendments on a dryland Dark Brown Chernozem
Erosion leads to substantial loss of soil productivity. To abate such decline, amendments such as manure or fertilizer have been successfully employed. However the longevities of erosion and soil amendment legacy effects are not well quantified. In 1957, a Dark Brown Chernozem soil at Lethbridge, AB was land-levelled, creating three degrees of topsoil removal or erosion: non-eroded, moderate erosion, or severe erosion. Two amendment studies (1980â85, 1987â91) were superimposed on the erosion treatments. Both studies were cropped to spring wheat (Triticum aestivum L.) from 1993â2010 to examine legacy effects of erosion and soil amendments on wheat yield and soil properties. Without amendment, mean wheat yield with moderate erosion was 40% of the non-eroded treatment, while severe erosion was 34% of the non-eroded treatment, 36â42 yr (1993â99) after erosion. With moderate or severe erosion, the restorative power of manure diminished substantially in the first 10â15 yr following cessation of addition, but then levelled off resulting in wheat yields up to 35% higher than equivalent non-amended treatments. Legacy effects of erosion (54 yr) and amendment (27â31 yr) on soil organic C and total N were also observed.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
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Vegetation Response to a One-Time Spent Drilling Mud Application to Semiarid, Mixed-Grass Prairie
Landspraying while drilling (LWD) is an approved disposal method for water-based drilling mud (WBM) systems in western Canada. The mud is applied either on cultivated land, where it is incorporated by cultivation, or on vegetated land where it is not incorporated. This study examined the effects of summer WBM application (0, 15, 20, 40, and 80 m3 ha-1) on native vegetation properties. Our results indicated that LWD increased bare ground but decreased lichen cover at the 80 m3 ha-1 rate relative to the untreated control. Nitrogen (N), sulfur (S), and magnesium (Mg) concentrations in aboveground plant tissue increased with increasing LWD rate in samples taken 45 d after WBM application, but these differences disappeared 1 yr after treatment. Increase in tissue concentration of phosphorus (P) with LWD rate, however, was only detected 3 yr after LWD. Nonetheless, these changes in tissue chemistry were not associated with significant changes in biomass yield or species composition. Overall, our results suggest that single WBM applications at rates (< 20 m3 ha-1) commonly used in western Canada, if properly managed, are unlikely to adversely affect native prairie vegetation.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
Soil Organic Matter Dynamics in Long-term Temperate Agroecosystems: Rotation and Nutrient Addition Effects
Soil organic matter (SOM) is a major driver of key agroecosystem functions. Our objective was to examine the dynamics of organic matter in whole soil, particulate (POM; > 53 mu m size), and mineral-associated (MAOM) fractions under varying crop rotations and nutrient managements at two long-term experimental sites (Breton and Lethbridge). Soil samples were collected from simple (2 yr) and complex (5 or 6 yr) crop rotations at the 5 - 10 cm depth. We found associations between SOM pools versus microbial community and soil aggregation. Compared to cropped soils, an adjacent forest exhibited a significantly higher soil total organic carbon (TOC) and a shift in SOM fractions with substantially higher POM. However, the forest soil had the lowest microbial biomass C among all the assessed land use systems (P <0 .05), suggesting that other factors than the amount of labile SOM (i.e., POM-C) were controlling the microbial community. When contrasted to simple 2 yr rotations, the complex rotations including perennials and legumes significantly raised TOC and soil total nitrogen as well as the stable SOM fraction (i.e., MAOM-C and -N)consistently for both Breton and Lethbridge sites. Our findings highlight that varying land managements have profound feedbacks on soil quality as mediated by alterations in long-term SOM dynamics.Peer reviewe
Assessing legacy effects of a 12âyear irrigated cropping systems study with a postâhoc bioassay
Abstract A healthy soil resource is vital to the continued success of irrigated agriculture in southern Alberta. A 12âyr (2000â2011) irrigated cropping systems study was followed with a dry bean (Phaseolus vulgaris L.) field bioassay in 2012, to assess legacy effects of preceding management. Specifically, a comparison of conventional (CONV) and conservation (CONS) management (reduced tillage, cover crops, compost addition, narrowârow dry bean) legacies was sought. However, rotational legacies such as preceding phase, length, preceding crop, and interval since previous dry bean were also assessed by the fully phased experimental setup. Only 1 of 18 possible soil management contrasts (CONV vs. CONS, 2000â2011) was significant for the dry bean bioassay in 2012, despite overwhelming evidence of improved soil health (microbial biomass C and ÎČâglucosidase activity) under CONS management. Monoculture wheat (Triticum aestivum L.) from 2000 to 2011 led to 2Â d earlier maturity and higher disease incidence in bioassay dry bean. With wheat as a preceding crop, bioassay dry bean was significantly shorter (4Â cm), earlier maturing (2Â d), and lower yielding (by 21â35%) than with dry bean, potato (Solanum tuberosum L.), or sugar beet (Beta vulgaris L.) as preceding crops, largely due to volunteer wheat competition. Significantly enhanced bioassay yields (9â13%) with shorter intervals since previous dry bean demonstrated a âlegume effect.â Overall, the dry bean bioassay was less effective at assessing soil management legacies (CONV vs. CONS) than rotational legacies such as preceding crop or interval since previous dry bean