Growing season

About: Growing season is a research topic. Over the lifetime, 11214 publications have been published within this topic receiving 331886 citations.

Elevated atmospheric CO2 and feedback between carbon and nitrogen cycles

Abstract: We tested a conceptual model describing the influence of elevated atmospheric CO2 on plant production, soil microorganisms, and the cycling of C and N in the plant-soil system. Our model is based on the observation that in nutrient-poor soils, plants (C3) grown in an elevated CO2 atmosphere often increase production and allocation to belowground structures. We predicted that greater belowground C inputs at elevated CO2 should elicit an increase in soil microbial biomass and increased rates of organic matter turnover and nitrogen availability. We measured photosynthesis, biomass production, and C allocation of Populus grandidentata Michx. grown in nutrient-poor soil for one field season at ambient and twice-ambient (i.e., elevated) atmospheric CO2 concentrations. Plants were grown in a sandy subsurface soil i) at ambient CO2 with no open top chamber, ii) at ambient CO2 in an open top chamber, and iii) at twice-ambient CO2 in an open top chamber. Plants were fertilized with 4.5 g N m−2 over a 47 d period midway through the growing season. Following 152 d of growth, we quantified microbial biomass and the availabilities of C and N in rhizosphere and bulk soil. We tested for a significant CO2 effect on plant growth and soil C and N dynamics by comparing the means of the chambered ambient and chambered elevated CO2 treatments.

Climate change is affecting altitudinal migrants and hibernating species.

Abstract: Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years. This result differs from growing evidence from low altitudes that climate change is resulting in a longer growing season, earlier migrations, and earlier reproduction in a variety of taxa. At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, perhaps because of the trend for increased winter precipitation. This disjunction between phenology at low and high altitudes may create problems for species, such as many birds, that migrate over altitudinal gradients. We present data indicating that this already may be true for American robins, which are arriving 14 days earlier than they did in 1981; the interval between arrival date and the first date of bare ground has grown by 18 days. We also report evidence for an effect of climate change on hibernation behavior; yellow-bellied marmots are emerging 38 days earlier than 23 years ago, apparently in response to warmer spring air temperatures. Migrants and hibernators may experience problems as a consequence of these changes in phenology, which may be exacerbated if climate models are correct in their predictions of increased winter snowfall in our study area. The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover also have implications for hibernating species.

UK birds are laying eggs earlier

Abstract: The evidence for global climate change and for its underlying anthropogenic causes is gathering rapidly. Over the past 11 years the active growing season of plants has advanced by roughly 8 days in northern latitudes1. This evidence for increased photosynthetic activity is supported by the positive trend in the amplitude of the seasonal cycle in atmospheric CO2 (ref. 2). The phenology of animal populations should also be affected by climate change, but to date there has been little evidence of this. Here we report that long-term trends in the seasonal distributions of laying dates of birds in the United Kingdom show a tendency towards earlier laying, consistent with the changes reported in growing season.

Soil-surface CO2 efflux and its spatial and temporal variations in a young ponderosa pine plantation in northern California

Abstract: Soil-surface CO2 efflux and its spatial and temporal variations were examined in an 8-y-old ponderosa pine plantation in the Sierra Nevada Mountains in California from June 1998 to August 1999. Continuous measurements of soil CO2 efflux, soil temperatures and moisture were conducted on two 20 3 20 m sampling plots. Microbial biomass, fine root biomass, and the physical and chemical properties of the soil were also measured at each of the 18 sampling locations on the plots. It was found that the mean soil CO2 efflux in the plantation was 4.43 mmol m ‐2 s ‐1 in the growing season and 3.12 mmol m ‐2 s ‐1 in the nongrowing season. These values are in the upper part of the range of published soil-surface CO2 efflux data. The annual maximum and minimum CO2 efflux were 5.87 and 1.67 mmol m ‐2 s ‐1 , respectively, with the maximum occurring between the end of May and early June and the minimum in December. The diurnal fluctuation of CO2 efflux was relatively small ( 14%. Understanding the spatial and temporal variations is essential to accurately assessment of carbon budget at whole ecosystem and landscape scales. Thus, this study bears important implications for the study of large-scale ecosystem dynamics, particularly in response to climatic variations and management regimes.

Countergradient variation in growth rate: compensation for length of the growing season among Atlantic silversides from different latitudes.

Abstract: How do organisms adapt to the differences in temperature and length of the growing season that occur with latitude? Among Atlantic silversides (Menidia menidia) along the east coast of North America, the length of the first growing season declines by a factor of about 2.5 with increasing latitude. Yet body size at the end of the first growing season does not decline. High-latitude fish must, therefore, grow faster within the growing season than do low-latitude fish. This geographical pattern has a genetic basis. Laboratory experiments on fish from six different locations revealed a latitudinal gradient in the capacity for growth (i.e., maximum growth potential). In two subsequent experiments using fish from Nova Scotia (NS), New York (NY) and South Carolina (SC) that had been separately reared in a common environment for several generations, differences in growth rate among populations were highly significant. The rank order was NS>NY>SC, but the difference among populations depended on temperature. High-latitude fish outperformed those from low latitudes primarily at the high temperatures that low-latitude fish would be expected to experience most often in nature. These results suggest that instead of being adapted for growth at low temperatures, fish from high latitudes are adapted for rapid elevation of growth rate during the brief interval of the year when high temperatures occur. Selection on growth rate results from sizedependent winter mortality: the importance to winter survival of being large increases with latitude but the length of the growing season simultaneously decreases. The end result is countergradient variation in growth rate, a phenomenon that may be much more widespread than currently recognized.