scholarly journals Spatiotemporal distribution of grassland NPP in Gansu province, China from 1982 to 2011 and its impact factors

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242609
Author(s):  
Meiling Zhang ◽  
Xiaoni Liu ◽  
Stephen Nazieh ◽  
Xingyu Wang ◽  
Teddy Nkrumah ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Classification System ◽  
Net Primary Production ◽  
Gansu Province ◽  
Impact Factors ◽  
Moisture Index ◽  
K Value ◽  
Major Controlling Factor ◽  
Development And Utilization ◽  
Spatio Temporal

The modified Carnegie–Ames–Stanford Approach (CASA) model based on the comprehensive and sequential classification system of grasslands (CSCS, a unique vegetation classification system) was used to determine grassland net primary production (NPP) in Gansu province from 1982 to 2011 and its spatio-temporal variability. The relationship between NPP and climate drivers was analyzed. The results showed that annual NPP of grasslands in Gansu province averaged 139.30 gC m-2 yr -1 during the study period. NPP decreased from southeast to northwest across the province. Grassland NPP showed an increasing trend during the period 1982–2011, and the increase rate over the whole period was 92.91%. The highest NPP appeared in summer with more precipitation and higher cumulative temperature conditions; while the lowest values existed in winter. The largest correlation coefficient was found between the average annual NPP and the average annual precipitation (r = 0.77), followed by annual NPP and solar radiation (r = 0.70) or NDVI (r = 0.69), Annual NPP had no significant correlation with annual cumulative temperature (>0°C) or moisture index (K-value). Thus, precipitation is the major controlling factor on the average annual NPP in Gansu grassland. Solar radiation and NDVI also have important effects on grassland NPP in Gansu. These results may provide basic information for sustainable development and utilization of grassland and for the improvement and protection of the ecological environment as well.

scholarly journals Habitat-mediated population limitation in a colonial central-place forager: the sky is not the limit for the black-browed albatross

2014 ◽  
Vol 281 (1778) ◽  
pp. 20132883 ◽  
Author(s):  
Ewan D. Wakefield ◽  
Richard A. Phillips ◽  
Jason Matthiopoulos
Keyword(s):  
Resource Availability ◽  
Net Primary Production ◽  
Strong Dependence ◽  
Resource Limitation ◽  
Central Place ◽  
Population Limitation ◽  
Animal Populations ◽  
Temporal Predictability ◽  
Spatio Temporal ◽  
The Cost

Animal populations are frequently limited by the availability of food or of habitat. In central-place foragers, the cost of accessing these resources is distance-dependent rather than uniform in space. However, in seabirds, a widely studied exemplar of this paradigm, empirical population models have hitherto ignored this cost. In part, this is because non-independence among colonies makes it difficult to define population units. Here, we model the effects of both resource availability and accessibility on populations of a wide-ranging, pelagic seabird, the black-browed albatross Thalassarche melanophris . Adopting a multi-scale approach, we define regional populations objectively as spatial clusters of colonies. We consider two readily quantifiable proxies of resource availability: the extent of neritic waters (the preferred foraging habitat) and net primary production (NPP). We show that the size of regional albatross populations has a strong dependence, after weighting for accessibility, on habitat availability and to a lesser extent, NPP. Our results provide indirect support for the hypothesis that seabird populations are regulated from the bottom-up by food availability during the breeding season, and also suggest that the spatio-temporal predictability of food may be limiting. Moreover, we demonstrate a straightforward, widely applicable method for estimating resource limitation in populations of central-place foragers.

scholarly journals AN EFFICIENT CLUSTERING METHOD FOR DBSCAN GEOGRAPHIC SPATIO-TEMPORAL LARGE DATA WITH IMPROVED PARAMETER OPTIMIZATION

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 581-584
Author(s):  
J. W. Li ◽  
X. Q. Han ◽  
J. W. Jiang ◽  
Y. Hu ◽  
L. Liu
Keyword(s):  
Parameter Optimization ◽  
Clustering Algorithm ◽  
Optimal Solution ◽  
Large Data ◽  
Parameter Selection ◽  
Physical Analysis ◽  
Clustering Method ◽  
K Value ◽  
Dbscan Clustering ◽  
Spatio Temporal

Abstract. How to establish an effective method of large data analysis of geographic space-time and quickly and accurately find the hidden value behind geographic information has become a current research focus. Researchers have found that clustering analysis methods in data mining field can well mine knowledge and information hidden in complex and massive spatio-temporal data, and density-based clustering is one of the most important clustering methods.However, the traditional DBSCAN clustering algorithm has some drawbacks which are difficult to overcome in parameter selection. For example, the two important parameters of Eps neighborhood and MinPts density need to be set artificially. If the clustering results are reasonable, the more suitable parameters can not be selected according to the guiding principles of parameter setting of traditional DBSCAN clustering algorithm. It can not produce accurate clustering results.To solve the problem of misclassification and density sparsity caused by unreasonable parameter selection in DBSCAN clustering algorithm. In this paper, a DBSCAN-based data efficient density clustering method with improved parameter optimization is proposed. Its evaluation index function (Optimal Distance) is obtained by cycling k-clustering in turn, and the optimal solution is selected. The optimal k-value in k-clustering is used to cluster samples. Through mathematical and physical analysis, we can determine the appropriate parameters of Eps and MinPts. Finally, we can get clustering results by DBSCAN clustering. Experiments show that this method can select parameters reasonably for DBSCAN clustering, which proves the superiority of the method described in this paper.

Effect of environmental factors on the spatio-temporal patterns of influenza spread

2009 ◽  
Vol 137 (10) ◽  
pp. 1377-1387 ◽  
Author(s):  
K. M. L. CHARLAND ◽  
D. L. BUCKERIDGE ◽  
J. L. STURTEVANT ◽  
F. MELTON ◽  
B. Y. REIS ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Solar Radiation ◽  
Temporal Patterns ◽  
Dew Point ◽  
Bayesian Hierarchical ◽  
Influenza Activity ◽  
The Usa ◽  
Geographical Position ◽  
Spatio Temporal ◽  
Epidemic Timing

SUMMARYAlthough spatio-temporal patterns of influenza spread often suggest that environmental factors play a role, their effect on the geographical variation in the timing of annual epidemics has not been assessed. We examined the effect of solar radiation, dew point, temperature and geographical position on the city-specific timing of epidemics in the USA. Using paediatric in-patient data from hospitals in 35 cities for each influenza season in the study period 2000–2005, we determined ‘epidemic timing’ by identifying the week of peak influenza activity. For each city we calculated averages of daily climate measurements for 1 October to 31 December. Bayesian hierarchical models were used to assess the strength of association between each variable and epidemic timing. Of the climate variables only solar radiation was significantly related to epidemic timing (95% CI −0·027 to −0·0032). Future studies may elucidate biological mechanisms intrinsically linked to solar radiation that contribute to epidemic timing in temperate regions.

Structure Analysis and Performance Simulation on the Walking Mechanism of the Transportation Machine Providing Disaster Relief

2011 ◽  
Vol 183-185 ◽  
pp. 2237-2241
Author(s):  
Hui Wang ◽  
Yan Ma ◽  
Chang Qing Ren ◽  
Ning Li
Keyword(s):  
Disaster Relief ◽  
Impact Factors ◽  
Design Parameters ◽  
Theoretical Derivation ◽  
Component Size ◽  
Development And Utilization ◽  
The New Period ◽  
And Performance ◽  
Walking Mechanism ◽  
The Impact

It makes a brief description of the transportation machine providing disaster relief. The paper makes a deep analysis and founds a scheme on the walking mechanism of the transportation machine sending relief to a disaster area, illustrates the relationship among the mechanism structure, component size, tracks and kinematic parameters of the foot. It makes an experimental prototype design which through the analysis before, embeds the scheme into the design parameters, and conducts an actual verification about the results of theoretical derivation. The results proved the feasibility of the design, and reflected the impact factors. It will lay the theoretical foundation for the walking mechanism’s design and research of the transportation machine providing disaster relief, and will be in favor of the development and utilization of the transportation machine providing disaster relief in the new period.

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