2294 N kg/ha (Figure 9).
The most efficient herbaceous layer for nutrient uptake of was the wheat crop (A). This agriculture land is the most productive and registering the highest productivity (4.741 g/m2/year) (Figure 11). Although the most productive is farmland, the highest value of standing crop was
Loss of biomass (g)
wetland, because in agriculture land most of the biomass was removed with threshing. Also the wheat straw is being removed by the local population as they use this for bedding in stables.
The least efficient in nutrient uptake and storage was herbaceous layer in mixed forest F1. This layer is very low productive due to competition for light, space and nutrients. Also, the pedo- climatic conditions in the forest (high humidity, organic matter in sufficient quantities, good oxygenation conditions) creates optimal conditions for litter decomposition, and recorded the highest rate of decomposition (5.327 x 10-2 g/m2 day-1).
FIG. 9. Nutrients balance in trees layer wood
In tree layer amount of nutrients (C and N) stored in the wood, only in 2011, was 10 times greater than that stored in the leaves. In wood, the amount of nutrients taken as productivity, accumulate from year to year and only the leaves supplies the litter, which decomposes. In the two forest types (F1 and F2), about 80% of litter is decomposed, and 20% accumulates at the soil surface and supplies the top soil with organic matter (Figure 10). Organic matter plays a fundamental role in soil processes; this is an energy source of microorganisms and precursor in soil humic acids.
Although part of N is lost in the process of denitrification, like a final stage of decomposition, a large amount of N returned to soil as nutrients from which is taken by plants. The analyses of Figure 9 show that the temperate forests are very important ecosystems in terms of the amount of carbon storage and fertility of the soils.
FIG. 10. Nutrients balance in trees layer leafs
FIG. 11. Nutrients balance in herbaceous layer
Making a unilateral analysis regarding takeover efficiency and nutrient use by plants in crops we take the risk of leaving the role of other types of ecosystem in nutrients cycling. A holistic approach, with simultaneous analysis for all function of different types of ecosystem (reducing pollution, creating local microclimates, etc.) outside the production can give an overview and help making the best decisions in different types of land. Natural and semi-natural ecosystems are the main sources in the production of resources and energy generation and play an important role in reducing pollution. With resources and energy required are greater with both human pressures exerted on ecosystems and biodiversity is higher, which implies the need for preservation of these species and ecosystems. Residues arising from the use of resources that emphasize forms of pollution accentuate the anthropogenic pressure on natural resources. Keeping a mosaic structure is an ideal solution to harmonize the development of society with nature conservation. A green infrastructure with lacks and rivers, wetland, different types of forest, pastures, shrubs including different types of crops, it represent the ideal structure provide both energy and resources needs.
3.5.2. Water balance compensate the water losses by evapo-transpiration. The area is cultivated with various crops (corn, wheat, sunflower) without the need for irrigation. Higher values of precipitation are recorded in July, August and September. The phenomenon is manifested by frequent droughts, some lasting. The average intervals of drought, is 15 to 19 days and maximum of 50 days.
4. CONCLUSIONS
Green infrastructure in Glavacioc catchment is very heterogeneous land use. The catchment has the following ecosystems that include: rivers and lakes, wetland with Carex sp. Lythrum sp.
Scyrpus sp., wetland with Salix sp. and Typha sp., Phragmites sp., pastures for animal grazing, nine types of forest that include mixed forests, 25 types of crops, and urban development. This mosaic of land use provides species diversity, a source of natural resources (wood, biomass, food) and great areas to reduce diffuse pollution from agriculture (riparian areas that function as buffer zones). The number of species in the vegetation mosaic was 74 and that of ecosystems types was 41 of which the most numerous were the semi-natural and anthropogenic. Forested area in Glavacioc basin occupies an area of 540 ha, and mean annual wood production is approximately 3 240 m3/ha/year. The catchment inhabits population in the basin approximately 10 652 human being grouped in nearly 3 200 households and uses about 16 000 m3 of firewood and 20% of which is obtained from local forests. Biomass production capacity of herbaceous layers at basin level is 15 656 tons (1 319.4 by wetland, 468 by herbaceous plant in mixed forests, 2 173 by herbaceous plant in querceta forests, 241 pasture and 11,453 by straw and debris from agricultural crops), providing a daily diet for 521 885 cows and annual food for 1 430. About one in two households obtained their food from animals. In Romania, grazing in forest is prohibited by law thus 13.4% of biomass available cannot be used.
The fixing capacity of C from carbon dioxide by photosynthesis at basin level is 4 712 tons (52 wetland, 1 269 mixed forest, 1 073 by querceta forest, 5.5 by pasture and 2 309 by crops), which is 0.000075‰ of total emissions of C estimated at global level (0.63 x 109 t) annually. The percentage seems insignificant but the vegetation covers a total area of only 3 896 ha, with is 0.000029% the global land surface (13 400 x 106 ha) [13]. Nitrogen uptake capacity of green infrastructure at basin level is 104 072 kg (2 661 by wetlands, 5 546 by mixed forests, 6 230 by querceta forests, 292 by pastures and 89 341 by agriculture land). The amounts of N coming from
fertilizers to the catchment is 15 483 kg/year and from untreated sewage is 8 577 kg/year and represent 23% of the uptake capacity of the vegetation in the basin, less than one quarter. Al though in the 2008 report of Ministries of Environment and Forests it says that is an area with high potential for N pollution originating from agriculture, in 2010 was observed that the mosaic of vegetation used as a buffer zone was benefit at a rate of 23% [13]. At present, in Glavacioc basin is sufficient as a natural buffer area. Such natural areas can to be used to retain the pollution with N coming from agricultural diffuse sources. In the future it should be noted that small amount of natural fertilizers can be applied to agricultural farms in the Glavocioc catchment to preserve this mosaic structure.
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