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1. Soil disturbance by animals affects the availability of water, nutrients, sediment and seeds, which are critical for the maintenance of functional ecosystems. We examined long-lived faunal structures across six vegetation communities in the northern Chihuahuan desert of New Mexico, USA, testing the proposition that disturbances in undesertified grassland differ in magnitude and effect from those in desertified grassland. 2. Vertebrate and invertebrate disturbances totalled 18.9 structures ha−1 across 18 sites. The most common were pits and mounds of American badgers (Taxidea taxus, 32%), nests of the ant Aphaenogaster cockerelli (18.8%) and mounds of kangaroo rats (Dipodomys spectabilis, 31%). 3. Desertification...
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1 We assess the use of simple, size-based matrix population models for projecting population trends for six coniferous tree species in the Sierra Nevada, California. We used demographic data from 16 673 trees in 15 permanent plots to create 17 separate time-invariant, density-independent population projection models, and determined differences between trends projected from initial surveys with a 5-year interval and observed data during two subsequent 5-year time steps. 2 We detected departures from the assumptions of the matrix modelling approach in terms of strong growth autocorrelations. We also found evidence of observation errors for measurements of tree growth and, to a more limited degree, recruitment. Loglinear...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
1. Plant carbon (C) and nitrogen (N) inputs to soil interact with microbes and abiotic factors like climate and pH to influence soil fertility and plant productivity. Although root exudates and root litter are important factors affecting the cycling of nutrients critical to plant growth, many studies remain focused on effects of above-ground litter inputs. 2. Using two species that co-dominate alpine moist meadows as a model system (the phenolic-rich forb Geum rossii, and the fast-growing grass Deschampsia caespitosa), we asked whether C from G. rossii fine roots could reduce D. caespitosa growth. We hypothesized that root C would indirectly reduce D. caespitosa growth by stimulating soil microbes, thus restricting...
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1 Univariate, multivariate, and geostatistical techniques were used to quantify the scale and degree of soil variability around individual perennial sagebrush (Artemisia tridentata ssp. vaseyana) and bluebunch wheatgrass (Pseudoroegneria spicata ssp. spicata) plants. This variability was then compared to that found across the larger sagebrush-steppe site. Samples were taken every metre in a 10-m $\times$ 12-m grid and every 12.5 cm in nine nested 0.5-m $\times$ 0.5-m grids containing at least one Artemisia shrub or Pseudoroegneria tussock (362 total samples). The 11 soil properties measured were organic matter, pH, water content, live root mass, microbial respiration, net N mineralization, nitrification potential,...
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1. Macrofaunal leaf consumption and degradation of leaves, woody twigs and roots were studied in mangrove island forests on a Belizean island. Factors influencing accumulation of organic matter deposited both above and below ground in this oligotrophic, autochothonous system were assessed. 2. Leaf degradation rates of Rhizophora mangle (red mangrove), Avicennia germinans (black mangrove) and Laguncularia racemosa (white mangrove) measured in mesh bags, were much faster in the lower than the upper intertidal zone. Mass loss was most rapid in A. germinans but zonal effects were much larger than species differences. 3. Exposure to invertebrates such as crabs and amphipods tripled overall rates of leaf litter breakdown....
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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1. Recent studies have suggested that the simultaneous maintenance of multiple ecosystem functions (multifunctionality) is positively supported by species richness. However, little is known regarding the relative importance of other community attributes (e.g. spatial pattern, species evenness) as drivers of multifunctionality. 2. We conducted two microcosm experiments using model biological soil crust communities dominated by lichens to: (i) evaluate the joint effects and relative importance of changes in species composition, spatial pattern (clumped and random distribution of lichens), evenness (maximal and low evenness) and richness (from two to eight species) on soil functions related to nutrient cycling (β-glucosidase,...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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1. The structure and functioning of riverine ecosystems is dependent upon regional setting and the interplay of hydrologic regime and geomorphologic processes. We used a retrospective analysis to study recruitment along broad, alluvial valley segments (parks) and canyon segments of the unregulated Yampa River and the regulated Green River in the upper Colorado River basin, USA. We precisely aged 811 individuals of Populus deltoides ssp. wislizenii (native) and Tamarix ramosissima (exotic) from 182 wooded patches and determined the elevation and character of the germination surface for each. We used logistic regression to relate recruitment events (presence or absence of cohort) to five flow and two weather parameters.2....
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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We measured sediment elevation and accretion dynamics in mangrove forests on the islands of Guanaja and Roatan, Honduras, impacted by Hurricane Mitch in 1998 to determine if collapse of underlying peat was occurring as a result of mass tree mortality. Little is known about the balance between production and decomposition of soil organic matter in the maintenance of sediment elevation of mangrove forests with biogenic soils. Sediment elevation change measured with the rod surface elevation table from 18 months to 33 months after the storm differed significantly among low, medium and high wind impact sites. Mangrove forests suffering minimal to partial mortality gained elevation at a rate (5 mm yeara??1) greater than...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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A framework that summarizes the direct and indirect effects of past land use on forest herb recolonization is proposed, and used to analyse the colonization patterns of forest understorey herbaceous species in a 360-ha mixed forest, grassland and arable landscape in the Dijle river valley (central Belgium).Fine-scale distribution maps were constructed for 14 species. The species were mapped in 15 946 forest plots and outside forests (along parcel margins) in 5188 plots. Forest stands varied in age between 1 and more than 224 years. Detailed land-use history data were combined with the species distribution maps to identify species-specific colonization sources and to calculate colonization distances.The six most...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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Changing winter climate extremes are expected to result in the poleward migration of mangrove forests at the expense of salt marshes. Although mangroves and marshes are both highly valued ecosystems, the ecological implications of mangrove expansion have not been fully investigated. Here, we examined the effects of mangrove expansion on below-ground properties related to peat development and carbon storage. We investigated plant–soil interactions in marshes and across mangrove forest structural gradients in three locations in the northern Gulf of Mexico (USA). We compared our results to those from terrestrial grasslands where the effects of woody plant encroachment are often influenced by rainfall and plant traits....
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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The timing and extent of root growth and development were studied under field conditions in root observation chambers. These chambers were located near small groups of established perennial shrubs. Each of the shrub species, Atriplex confertifolia, Ceratoides lanata, and Artemisia tridentata occur in nearly monospecific stands. The presence of the observation chambers was shown to cause minimal disruption of the soil environment since soil temperatures and water potentials immediately proximate to the observation window were the same as those in the undisturbed soil profile. The season of root growth activity was initiated a few days before active shoot growth in the spring and extended for several months after...
Six study areas along an aridity gradient in Utah were investigated for effects of individual plants on modification of soil chemistry. Measurements were made of the contents of C, N and P and of pH and salinity. In one study area an ungrazed salt desert shrub site was compared with a comparable site with known grazing history. In two study areas, sites that had been tilled and converted from shrub steppe to introduced grass were compared with adjacent untilled soils. At all locations distinct soil chemical patterning was evident in both vertical and horizontal planes. Vertical concentration gradients with surface maxima are greater for C, N and P than for pH or salinity. Horizontal changes in chemical concentrations,...
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No. 2 fuel oil was fed to mallard (Anas platyrhynchos) ducklings in concentrations of 0.5 and 5.0% of the diet from hatching to 18 wk of age to assess the effects of chronic oil ingestion during early development. Five growth parameters (body weight, wing length, ninth primary length, tarsal length, and bill length) were depressed in birds receiving a diet containing 5% fuel oil. There was no oil-related mortality. The 5% fuel oil diet impaired avoidance behavior of 9-d-old mallard ducklings compared with controls or ducklings fed 0.5% oil. Open-field activity was greatly increased in 16-wk-old ducklings fed 5.0% oil. Liver hypertrophy and splenic atrophy were gross evidences of pathological effects in birds on...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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Species distribution shifts in response to climate change require that recruitment increase beyond current range boundaries. For trees with long life spans, the importance of climate-sensitive seedling establishment to the pace of range shifts has not been demonstrated quantitatively.Using spatially explicit, stochastic population models combined with data from long-term forest surveys, we explored whether the climate-sensitivity of recruitment observed in climate manipulation experiments was sufficient to alter populations and elevation ranges of two widely distributed, high-elevation North American conifers.Empirically observed, warming-driven declines in recruitment led to rapid modelled population declines at...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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Despite a large body of research documenting invasive plant impacts, few studies have followed individual invaded sites over decades to observe how they change, and none have contrasted how compositional impacts from invasion compare to ecosystem-process impacts over a multi-decadal time-scale. Using direct measurements of plant density and composition and of ecosystems processes, we evaluate how ecosystem structure, above-ground net primary production (ANPP), and above-ground and soil nutrient pools compare over 25 years since fire and C4 grass invasions disrupted seasonally dry Hawaiian woodlands. We compare structure and function between primary woodland that has never burned and is largely native species-dominated,...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
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1. The physiological tolerance hypothesis proposes that plant species richness is highest in warm and/or wet climates because a wider range of functional strategies can persist under such conditions. Functional diversity metrics, combined with statistical modeling, offer new ways to test whether diversity-environment relationships are consistent with this hypothesis. 2. In a classic study by R. H. Whittaker (1960), herb species richness declined from mesic (cool, moist, northerly) slopes to xeric (hot, dry, southerly) slopes. Building on this dataset, we measured four plant functional traits (plant height, specific leaf area, leaf water content and foliar C:N) and used them to calculate three functional diversity...
Categories: Publication; Types: Citation; Tags: Journal of Ecology
1 Recent research has demonstrated important linkages between above- and below-ground components of terrestrial ecosystems, but the relationships between aerial parasitic plants, such as dwarf mistletoes, and below-ground organisms, such as mycorrhizal fungi, have not been examined in detail. 2 We examined the relationship between dwarf mistletoe infection, host vigour and the ectomycorrhizal colonization and fungal community composition of pinyon pine (Pinus edulis) using a combination of field observations and glasshouse studies. 3 High levels of dwarf mistletoe infection were not associated with increased mortality or needle loss of infected pinyons, but infected trees had lower shoot growth. 4 Ectomycorrhizal...
1 Although drought frequency and severity are predicted to increase across numerous continental interiors, the consequences of these changes for dominant plants are largely unknown. Over the last decade, the south-western US has experienced six drought years, including the extreme droughts of 1996 and 2002, which led to widespread tree mortality across northern Arizona. 2 We examined the impact of these droughts on the co-dominant tree species of the pinyon?juniper woodland (Pinus edulis and Juniperus monosperma), a major vegetation type in the US. 3 Pinyon mortality following both droughts was 6.5-fold higher than juniper mortality. In addition, large pinyons suffered 2?6-fold greater mortality than small pinyons,...


map background search result map search result map Geostatistical Patterns of Soil Heterogeneity Around Individual Perennial Plants Phenology and Dynamics of Root Growth of Three Cool Semi-Desert Shrubs Under Field Conditions Functional diversity supports the physiological tolerance hypothesis for plant species richness along climatic gradients Geostatistical Patterns of Soil Heterogeneity Around Individual Perennial Plants Phenology and Dynamics of Root Growth of Three Cool Semi-Desert Shrubs Under Field Conditions Functional diversity supports the physiological tolerance hypothesis for plant species richness along climatic gradients