An introduction to the Special Issue on Global Change and Plant Reproduction

MechanismMajor consequences 1. CO 2 enrichment in atmosphere and oceans a) Accelerated growth of plants by rising CO 2 perturbs competitive balances, consumption patterns, and disturbance regimes.Biome switches are facilitated, for example, through accelerated succession of woody plants into grasslands.b) Ocean acidification with depletion of calcium carbonate shells.Negative impacts are amplified by algal competitors who displace corals and other shelled organisms.c) Altered sensing of CO 2 gradients, used by insects and fungi to detect food and reproductive opportunities. Key effect on plant reproduction:Accelerated photosynthesis and plant growth can enhance inflorescence size and flower number, fruit size and number, enrich nectar, reduce ovule abortion, and promote seedling establishment.High CO 2 can also promote heat sterility by warming crop canopies through reduced evapotranspiration.2. Climate warming, precipitation change a) Altered competitive dynamics, disturbance regimes and consumption patterns, especially following relaxation of lethal cold that suppresses cold-intolerant species.b) Increased heat and drought stress, and variability in temperature and precipitation, leading to higher mortality and growth inhibition.Increased fire frequency and intensity is a direct consequence of warmer, drier conditions.c) Disrupted timing of development and migration, with consequences for mutualistic and trophic interactions. Key effect on plant reproduction:Highly context dependent, can increase reproduction where warming reduces cold stress and increases growing season length, but can decrease reproduction at the upper end of the thermal range, for example by promoting heat sterility and inhibiting pollen germination.Increased drought probability generally reduces fecundity and pollinator numbers, nectar production and seedling establishment.Heat and drought can decrease plant resources for pollinators leading to pollen limitation and lower reproduction.Increased fire activity reduces both plant and pollinator populations of fire sensitive species, while potentially enhancing fecundity in fire resistant species, causing community shifts.In particular, fire can alter vegetation cover if propagules or juveniles are killed before reproductive maturity by accelerated fire activity. Stratospheric ozone reductionEnhances UV-B exposure but effects are subtle, largely occurring as altered growth and competitive success that are amplified by biotic interactions.Limited impacts worldwide, plus controls on chlorofluorocarbon emission reduces the priority of this driver. Key effects on plant reproduction:Potentially pollen injury, but main effects are on pigmentation of flowers and fruits; insect pollinators and herbivores may be vulnerable but apparently not at the modest levels of the predicted changes.B. Drivers that are Regional in Nature but so Widespread as to Scale to Global Significance.4. Land transformation a) Widespread loss of habitat for wild plants and animals due to direct land conversion to agriculture, pasture, managed timberlands, roads and human habitatation (intensive land use change).b) Longer-term and often cryptic loss of habitat due to alteration of ecological controls by low-intensity human management (extensive land use change).c) Increase in fragmentation, disturbance, exotic species invasions, and human development, often originating following road construction.d) Decrease in biodiversity.Land transformation is considered the most damaging to biodiversity up to the present time.