A simple model of yield was used along with climate scenarios to assess the impact of climate change on grain maize productivity
and associated economic risk in Switzerland. In a first application, changes in the precipitation regime alone were shown
to affect the distribution of yield considerably, with shifts not only in the mean but also in the standard deviation and
the skewness. Production risk was found to respond more markedly to changes in the long-term mean than in the inter-annual
variability of seasonal precipitation amounts. In a further application, yield projections were generated with respect to
a full climate scenario, with the emission pathway as specified in the IPCC A2 scenario. Anticipation of the sowing date was
found to reduce the negative impact of climate change on yield stability, but was not sufficient to ensure average productivity
levels comparable to those observed at present. We argued that this was caused by the reduction in the duration of the growing
season, which had a stronger impact than suggested by previous studies. Assuming no change in price relations, the results
also revealed a strong increase in production risk with climate change, with more than a doubling in the probability of yield
falling short of a critical threshold as compared to today’s situation. 相似文献
Despite its strong advantages in resource, technology and human resource, China's Northeast Industrial Area is also experiencing problems of unreasonable industrial structure, environmental pollution, and the degradation of ecological condition, etc., which prevent this area from achieving a sustainable devel- opment. Through analyzing the resource problem, the present paper proposed a strategy of circular economy for the prosperity of this are, discussed the theories of circular economy and resource recycling, and finally concluded that improving resource productivity is at the core of circular economy. 相似文献
The impact of 2 × CO2 driven climate change on radial growth of boreal tree species Pinus banksiana Lamb., Populus tremuloides Michx. and Picea mariana (Mill.) BSP growing in the Duck Mountain Provincial Forest of Manitoba (DMPF), Canada, is simulated using empirical and process-based model approaches. First, empirical relationships between growth and climate are developed. Stepwise multiple-regression models are conducted between tree-ring growth increments (TRGI) and monthly drought, precipitation and temperature series. Predictive skills are tested using a calibration–verification scheme. The established relationships are then transferred to climates driven by 1× and 2 × CO2 scenarios using outputs from the Canadian second-generation coupled global climate model. Second, empirical results are contrasted with process-based projections of net primary productivity allocated to stem development (NPPs). At the finest scale, a leaf-level model of photosynthesis is used to simulate canopy properties per species and their interaction with the variability in radiation, temperature and vapour pressure deficit. Then, a top-down plot-level model of forest productivity is used to simulate landscape-level productivity by capturing the between-stand variability in forest cover. Results show that the predicted TRGI from the empirical models account for up to 56.3% of the variance in the observed TRGI over the period 1912–1999. Under a 2 × CO2 scenario, the predicted impact of climate change is a radial growth decline for all three species under study. However, projections obtained from the process-based model suggest that an increasing growing season length in a changing climate could counteract and potentially overwhelm the negative influence of increased drought stress. The divergence between TRGI and NPPs simulations likely resulted, among others, from assumptions about soil water holding capacity and from calibration of variables affecting gross primary productivity. An attempt was therefore made to bridge the gap between the two modelling approaches by using physiological variables as TRGI predictors. Results obtained in this manner are similar to those obtained using climate variables, and suggest that the positive effect of increasing growing season length would be counteracted by increasing summer temperatures. Notwithstanding uncertainties in these simulations (CO2 fertilization effect, feedback from disturbance regimes, phenology of species, and uncertainties in future CO2 emissions), a decrease in forest productivity with climate change should be considered as a plausible scenario in sustainable forest management planning of the DMPF. 相似文献
Gap filling of flux data is necessary to assist with periodic interruptions in the measurement data stream. The gap-filling model (GFM), first described in Xing et al. [Xing, Z., Bourque, C.P.-A., Meng, F.-R., Zha, T.-S., Cox, R.M., Swift, E., 2007. A simple net ecosystem productivity model for gap filling of tower-based fluxes: an extension of Landsberg's equation with modifications to the light interception term. Ecol. Model. 206, 250–262], was modified to account for the day-to-day control of net ecosystem productivity (NEP) by incorporating air and soil temperature as new controlling variables in the calculation of NEP. To account for the multiple-phase influences of air and soil temperature on plant growth we model ecosystem respiration as a function of soil and canopy respiration. The paper presents model development in an incremental fashion in order to quantify the contribution of individual model enhancements to the prediction of NEP during periods when air and soil temperature variations are important. 相似文献
Honeybee colonies are highly integrated functional units characterized by a pronounced division of labor. Division of labor
among workers is mainly age-based, with younger individuals focusing on in-hive tasks and older workers performing the more
hazardous foraging activities. Thus, experimental disruption of the age composition of the worker hive population is expected
to have profound consequences for colony function. Adaptive demography theory predicts that the natural hive age composition
represents a colony-level adaptation and thus results in optimal hive performance. Alternatively, the hive age composition
may be an epiphenomenon, resulting from individual life history optimization. We addressed these predictions by comparing
individual worker longevity and brood production in hives that were composed of a single-age cohort, two distinct age cohorts,
and hives that had a continuous, natural age distribution. Four experimental replicates showed that colonies with a natural
age composition did not consistently have a higher life expectancy and/or brood production than the single-cohort or double-cohort
hives. Instead, a complex interplay of age structure, environmental conditions, colony size, brood production, and individual
mortality emerged. A general tradeoff between worker life expectancy and colony productivity was apparent, and the transition
from in-hive tasks to foraging was the most significant predictor of worker lifespan irrespective of the colony age structure.
We conclude that the natural age structure of honeybee hives is not a colony-level adaptation. Furthermore, our results show
that honeybees exhibit pronounced demographic plasticity in addition to behavioral plasticity to react to demographic disturbances
of their societies. 相似文献
The dynamics of agricultural and forestry biomass are highly sensitive to climate change, particularly in high latitude regions. Heilongjiang Province was selected as research area in North-east China. We explored the trend of regional climate warming and distribution feature of biomass resources, and then analyzed on the spatial relationship between climate factors and biomass resources. Net primary productivity (NPP) is one of the key indicators of vegetation productivity, and was simulated as base data to calculate the distribution of agricultural and forestry biomass. The results show that temperatures rose by up to 0.37°C/10a from 1961 to 2013. Spatially, the variation of agricultural biomass per unit area changed from -1.93 to 5.85 t·km–2·a–1 during 2000–2013. More than 85% of farmland areas showed a positive relationship between agricultural biomass and precipitation. The results suggest that precipitation exerts an overwhelming climate influence on agricultural biomass. The mean density of forestry biomass varied from 10 to 30 t·km–2. Temperature had a significant negative effect on forestry biomass in Lesser Khingan and northern Changbai Mountain, because increased temperature leads to decreased Rubisco activity and increased respiration in these areas. Precipitation had a significant positive relationship with forestry biomass in south-western Changbai Mountain, because this area had a warmer climate and stress from insufficient precipitation may induce xylem cavitation. Understanding the effects of climate factors on regional biomass resources is of great significance in improving environmental management and promoting sustainable development of further biomass resource use.