Land Leveling with Modern Machinery for the Implementation of Agricultural Activities in Greece

Incorporating modem and advanced technology （various electronic devices） to excavational machinery led to become more efficient, better quality and cost effective. The continuous development of equipment is also very important in the earth moving procedures which require significant time and expense to achieve the so-called ＂precision agriculture＂ or rather ＂precise management of agricultural inputs＂. One of the ＂precision agricultural＂ works is the land leveling. In recent years, land leveling is done with the use of a scraper （blade） mounted on the agricultural tractor. An electronic system controls the height of the blade automatically, without any operator intervention. In this paper, the field efficiency of the tractor MF6290, of 135 Hp horsepower, is calculated with a leveling blade of 4 m width, in the land leveling of rice cultivation, and in the rotation of different crops in different land preparation conditions （initial and final slope） in the area of Thessaloniki, northern Greece. The raw data revealed that the performance of the tractor ranged from 0.402 to 0.82 lha/h, on a slope 0%, while for surfaces with different initial and final slope, it ranged from 0.107 to 0.118 ha/h.

Land subsidence monitoring by D-InSAR technique

Nowadays, the researches of using Differential Interferometric Synthetic Aperture Radar (D-InSAR) tech- nique to monitor the land subsidence are mainly on how to qualitatively analyze the subsidence areas and values, but the analysis of subsidence process and mechanism are insufficient. In order to resolve these problems, 6 scenes of ERS1/2 images captured during 1995 and 2000 in a certain place of Jiangsu province were selected to obtain the subsidence and velocities in three time segments by ''two-pass'' D- InSAR method. Then the relationships among distributions of pumping wells, exploitation quantity of groundwater, and confined water levels were studied and the subsidence mechanism was systematically analyzed. The results show that using D-InSAR technique to monitor the deformation of large area can obtain high accuracies, the disadvantages of classical observation methods can be remedied and there is a linear relationship among the velocities of land subsidence, the water level and the exploitation quantity.

The monitoring and analysis of the coastal lowland subsidence in the southern Hangzhou Bay with an advanced time-series InSAR method

Time-series InSAR analysis（e.g., permanent scatterers（PSInSAR）） has been proven as an effective technology in monitoring ground deformation over urban areas. However, it is a big challenge to apply this technology in coastal regions due to the lack of man-made targets. An distributed scatterers interferometric synthetic aperture radar（DSInSAR） is developed to solve the problem of insufficient samples and low reliability in monitoring coastal lowland subsidence, by applying a spatially adaptive filter and an eigendecomposition algorithm to estimating the optimal phase of statistically homogeneous distributed scatterers（DSs）. Twenty-four scenes of COSMO-Sky Med images acquired between 2013 and 2015 are used to retrieve the land subsidence over the Shangyu District on south coast of the Hangzhou Bay, Zhejiang Province, China. The spatial pattern of the land subsidence obtained by the PS-InSAR and the DSInSAR coincides with each other, but the density of the DSs is three point five times higher than the permanent scatterers（PSs）. Validated by precise levelling data over the same period, the DSInSAR method achieves an accuracy of ±5.0 mm/a which is superior to the PS-InSAR with±5.5 mm/a. The land subsidence in the Shangyu District is mainly distributed in the urban areas, industrial towns and land reclamation zones, with a maximum subsidence rate -30.2 mm/a. The analysis of geological data, field investigation and historical reclamation data indicates that human activities and natural compaction of reclamation material are major causes of the detected land subsidence. The results demonstrate that the DSInSAR method has a great potential in monitoring the coastal lowland subsidence and can be used to further investigate subsidence-related environmental issues in coastal regions.

A Study of the Driving Force Model Revealing Changes in Land Utilization Level Based on 3S Technologies ——The Example of Yuanmou, Yunnan, China

This paper introduced the theory and approaches of building driving forcemodels revealing the changes in land utilization level by integrating RS, GPS, and GIS technologiesbased on the example of Yuanmou County of Yunnan Province. We first created the land utilizationtype database, natural driving forces for land utilization database, and human driving forces forland utilization database. Then we obtained the dependent and the independent variables of changesin land utilization level by exploring various data. Lastly we screened major factors affectingchanges in land utilization level by using the powerful spatial correlation analysis and maincomponent analysis module of GIS and obtained a multivariable linear regression model of thechangesin land utilization level by using GIS spatial regression analysis module.

STUDY ON METHODS OF LAND USE DYNAMIC MONITORING AT COUNTY LEVEL──Taking Dehui County, Jilin Province for Example

Remote sensing technique has played an important role in land use dynamic monitoring, but as for the land use dynamic monitoring at county level, traditional remote sensing methods such as satellite imagery visual interpretation and computer classification can not meet its demand for accuracy. The result of 1:10 000 land use investigation map has high accuracy, but this method can not be used to dynamically monitor the land use because of its big expenses, long period and difficulty in updating data. In this paper, the characteristics of physiognomy, climate and the status of land use in Dehui County are taken into consideration and a set of method, which takes use of 3S techniques and applies to Northeast China Plain, is come up with. When the land use type of a land parcel changed as a whole, the date updating can be make by changing its land type ID in the attribute table in a GIS. When the land use type of an irregular area changed, GPS receivers are used to position its border. This set of method is characteristic of high accuracy and low expenses. It gets the information of land use change timely and can be used to dynamically monitor the land use. .

Effect and economic benefit of precision seeding and laser land leveling for winter wheat in the middle of China

Rapid socio-economic changes in China,such as land conversion and urbanization,are creating new scopes for the application of precision agriculture(PA).An experiment to assess the economic benefits of two precision agriculture methods was applied for one year–precision seeding and precision seeding with land leveling.Whilst the results for this were positive,of itself it did not provide evidence of longer terms gains.The costs of land leveling are accrued in a single year but the benefits could carry over into subsequent years.Thus,in this case if the PA method provides carry over benefits to future years,the economic assessment would incorrectly assign all the costs to a single year of benefits i.e.the benefit-cost ratio would be underestimated.To gauge whether there was carry over benefits in future years we looked at NDVI and GUI as proxies for future year benefits.For the single year experiment,our results showed that:(1)Winter wheat yield was increased 23.2%through the integration of precision seeding and laser leveling technologies.(2)Both the single technology and the integrated technologies significant reduced the concentration of soil ammonium nitrogen at the depths of 60 cm;(3)The benefit/cost ratio's of the treatments exceeded that of the baseline by approximately 10%which translated to an increase of several hundred US$per hectare.The NDVI analysis showed that the effect of laser land leveling could last to the next two years.When considering the multi-year impact of land leveling,the benefit/cost ratio of PSLL will increase to 23.5%and 22.9%with and without laser land leveling subsidies.Making clear the eco-nomic benefits of using PA technologies will likely promote application of the technologies in the region.

An assessment of “fishing down marine food webs” in coastal states during 1950–2010

Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined with trophic information of relevant species in Fish Base, we evaluated the status of marine fisheries from 1950 to 2010 for different coastal states in Pacific, Atlantic and Indian Oceans. We found that the phenomenon of ＂fishing down marine food webs＂ occurred in 43 states. Specifically, 27 states belonged to ＂fishing-through＂ pattern, and 16 states resulted from ＂fishing-down＂ scenario. The sign of recovery in MTL was common in the Pacific, Atlantic and Indian Oceans（occurred in 20 states）, but was generally accompanied by significantly decreased catches of traditional low trophic level species. In particular, 11 states showed significant declining catches of lower trophic levels. The MTL-based assessment of ＂fishing down marine food webs＂ needs to be interpreted cautiously.

An evaluation of underlying mechanisms for“fishing down marine food webs”

Since the concept of ＂fishing down marine food webs＂ was first proposed in 1998, mean trophic level of fisheries landings（MTL） has become one of the most widely used indicators to assess the impacts of fishing on the integrity of marine ecosystem and guide the policy development by many management agencies. Recent studies suggest that understanding underlying causes for changes in MTL is vital for an appropriate use of MTL as an indicator of fishery sustainability. Based on the landing data compiled by Food and Agriculture Organization（FAO） and trophic information of relevant species in Fishbase, we evaluated MTL trends in 14 FAO fishing areas and analyzed catches of upper and lower trophic level groups under different trends of MTL and found that both the cases of a recovered MTL trend and a generally increasing MTL trend could be accompanied by decreasing catches of lower trophic level species. Further, community structure and exploitation history should be considered in using MTL after excluding species with trophic levels lower than 3.25 to distinguish ＂fishingthrough＂ from ＂fishing-down＂. We conclude that MTL used as an indicator to measure fishery sustainability can benefit from a full consideration of both upper and lower trophic level species and masking effects of community structure and exploitation history.