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Cool flowers : how to grow and enjoy long-blooming hardy annual flowers using cool weather techniques
\"In Cool Flowers, cut-flower farmer Lisa Ziegler presents simple, tried-and-true techniques for today's gardener and profiles 30 of her favorite hardy annual flowers. Your reward? A cutting garden that keeps on blooming when the \"tender annuals\" are dead and gone.\"-- Provided by publisher.
Book
Intra‐annual growing season climate variability drives the community intra‐annual stability of a temperate grassland by altering intra‐annual species asynchrony and richness in Inner Mongolia, China
Understanding the factors that regulate the functioning of our ecosystems in response to environmental changes can help to maintain the stable provisioning of ecosystem services to mankind. This is especially relevant given the increased variability of environmental conditions due to human activities. In particular, maintaining a stable production and plant biomass during the growing season (intra‐annual stability) despite pervasive and directional changes in temperature and precipitation through time can help to secure food supply to wild animals, livestock, and humans. Here, we conducted a 29‐year field observational study in a temperate grassland to explore how the intra‐annual stability of primary productivity is influenced by biotic and abiotic variables through time. We found that intra‐annual precipitation variability in the growing season indirectly influenced the community intra‐annual biomass stability by its negative effect on intra‐annual species asynchrony. While the intra‐annual temperature variability in the growing season indirectly altered community intra‐annual biomass stability through affecting the intra‐annual species richness. At the same time, although the intra‐annual biomass stability of the dominant species and the dominant functional group were insensitive to climate variability, they also promoted the stable community biomass to a certain extent. Our results indicate that ongoing intra‐annual climate variability affects community intra‐annual biomass stability in the temperate grassland, which has important theoretical significance for us to take active measures to deal with climate change. Intra‐annual growing season precipitation variability and temperature variability indirectly influenced the community intra‐annual biomass stability by negative effect on intra‐annual species asynchrony and intra‐annual species richness, respectively. ; Intra‐annual biomass stability of dominant species and dominant functional group were insensitive to climate variability, they also promoted the stable community biomass to a certain extent.
Journal Article
Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation
Climate gradients shape spatial variation in the richness and composition of plant communities. Given future predicted changes in climate means and variability, and likely regional variation in the magnitudes of these changes, it is important to determine how temporal variation in climate influences temporal variation in plant community structure. Here, we evaluated how species richness, turnover, and composition of grassland plant communities responded to interannual variation in precipitation by synthesizing long-term data from grasslands across the United States. We found that mean annual precipitation (MAP) was a positive predictor of species richness across sites, but a positive temporal relationship between annual precipitation and richness was only evident within two sites with low MAP. We also found higher average rates of species turnover in dry sites that in turn had a high proportion of annual species, although interannual rates of species turnover were surprisingly high across all locations. Annual species were less abundant than perennial species at nearly all sites, and our analysis showed that the probability of a species being lost or gained from one year to the next increased with decreasing species abundance. Bray-Curtis dissimilarity from one year to the next, a measure of species composition change that is influenced mainly by abundant species, was insensitive to precipitation at all sites. These results suggest that the richness and turnover patterns we observed were driven primarily by rare species, which comprise the majority of the local species pools at these grassland sites. These findings are consistent with the idea that short-lived and less abundant species are more sensitive to interannual climate variability than longer-lived and more abundant species. We conclude that, among grassland ecosystems, xeric grasslands are likely to exhibit the greatest responsiveness of community composition (richness and turnover) to predicted future increases in interannual precipitation variability. Over the long term, species composition may shift to reflect spatial patterns of mean precipitation; however, perennial-dominated systems will be buffered against rising interannual variation, while systems that have a large number of rare, annual species will show the greatest temporal variability in species composition in response to rising interannual variability in precipitation.
Journal Article
Climate Impacts on Forest and Grassland Resilience in China: The Role of Climate Inter‐Annual Variability
Understanding how vegetation resilience responds to climate change is crucial for maintaining ecosystem functions. This study focuses on forest and grassland ecosystems and uses theoretical recovery rate as a measure to assess climate impacts on their resilience over China. Our findings reveal that vegetation resilience varies across aridity‐dependent climate zones, with each zone showing different resilience–aridity relationships. Particularly, semi‐arid zones exhibit the lowest vegetation resilience, where the forest resilience declines as inter‐annual temperature and precipitation variability increases. In zones with sufficient water, the forest resilience remains stable. Grassland resilience decreases with increasing precipitation variability, but is insensitive to inter‐annual temperature variability. Future projections highlight the potential threat of climate change to regions encompassing more than 20% of vegetated areas, particularly in the forest‐grassland ecotones of North China. These findings enhance our understanding of climate‐ecosystem interactions and support the anticipation and management of ecosystem risks under climate change.
Journal Article
Long‐term effects of seeding after wildfire on vegetation in Great Basin shrubland ecosystems
Invasive annual grasses alter fire regimes in shrubland ecosystems of the western USA, threatening ecosystem function and fragmenting habitats necessary for shrub‐obligate species such as greater sage‐grouse. Post‐fire stabilization and rehabilitation treatments have been administered to stabilize soils, reduce invasive species spread and restore or establish sustainable ecosystems in which native species are well represented. Long‐term effectiveness of these treatments has rarely been evaluated. We studied vegetation at 88 sites where aerial or drill seeding was implemented following fires between 1990 and 2003 in Great Basin (USA) shrublands. We examined sites on loamy soils that burned only once since 1970 to eliminate confounding effects of recurrent fire and to assess soils most conducive to establishment of seeded species. We evaluated whether seeding provided greater cover of perennial seeded species than burned–unseeded and unburned–unseeded sites, while also accounting for environmental variation. Post‐fire seeding of native perennial grasses generally did not increase cover relative to burned–unseeded areas. Native perennial grass cover did, however, increase after drill seeding when competitive non‐natives were not included in mixes. Seeding non‐native perennial grasses and the shrub Bassia prostrata resulted in more vegetative cover in aerial and drill seeding, with non‐native perennial grass cover increasing with annual precipitation. Seeding native shrubs, particularly Artemisia tridentata, did not increase shrub cover or density in burned areas. Cover of undesirable, non‐native annual grasses was lower in drill seeded relative to unseeded areas, but only at higher elevations. Synthesis and applications. Management objectives are more likely to be met in high‐elevation or precipitation locations where establishment of perennial grasses occurred. On lower and drier sites, management objectives are unlikely to be met with seeding alone. Intensive restoration methods such as invasive plant control and/or repeated sowings after establishment failures due to weather may be required in subsequent years. Managers might consider using native‐only seed mixtures when establishment of native perennial grasses is the goal. Post‐fire rehabilitation provides a land treatment example where long‐term monitoring can inform adaptive management decisions to meet future objectives, particularly in arid landscapes where recovery is slow.
Journal Article
Global patterns of terrestrial nitrogen and phosphorus limitation
Nitrogen (N) and phosphorus (P) limitation constrains the magnitude of terrestrial carbon uptake in response to elevated carbon dioxide and climate change. However, global maps of nutrient limitation are still lacking. Here we examined global N and P limitation using the ratio of site-averaged leaf N and P resorption efficiencies of the dominant species across 171 sites. We evaluated our predictions using a global database of N- and P-limitation experiments based on nutrient additions at 106 and 53 sites, respectively. Globally, we found a shift from relative P to N limitation for both higher latitudes and precipitation seasonality and lower mean annual temperature, temperature seasonality, mean annual precipitation and soil clay fraction. Excluding cropland, urban and glacial areas, we estimate that 18% of the natural terrestrial land area is significantly limited by N, whereas 43% is relatively P limited. The remaining 39% of the natural terrestrial land area could be co-limited by N and P or weakly limited by either nutrient alone. This work provides both a new framework for testing nutrient limitation and a benchmark of N and P limitation for models to constrain predictions of the terrestrial carbon sink.Spatial patterns in the phosphorus and nitrogen limitation in natural terrestrial ecosystems are reported from analysis of a global database of the resorption efficiency of nutrients by leaves.
Journal Article
