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Variability and distribution of spatial evapotranspiration in semi arid Inner Mongolian grasslands from 2002 to 2011.

Schaffrath D, Bernhofer C - Springerplus (2013)

Bottom Line: Modelled ET was also compared with the ET provided by the MODIS MOD16 ET data.Despite the high interannual and innerannual variations of spatial ET, the study also showed the existence of an intrinsic long-term spatial pattern of ET distribution, which can be explained partly by altitude and longitude (R(2) = 0.49).In conclusion, the results of this research suggest the development of dynamic and productive rangeland management systems according to the inherent variability of rainfall, productivity and ET in order to restore and protect Inner Mongolian grasslands.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hydrology and Meteorology, Technische Universität Dresden, Dresden, Germany ; Professur für Meteorologie, TU Dresden, Fakultät Umweltwissenschaften, PF 1117, 01735 Tharandt, Germany.

ABSTRACT
Grasslands in Inner Mongolia are important for livestock farming while ecosystem functioning and water consumption are dominated by evapotranspiration (ET). In this paper we studied the spatiotemporal distribution and variability of ET and its components in Inner Mongolian grasslands over a period of 10 years, from 2002 to 2011. ET was modelled pixel-wise for more than 3000 1 km(2) pixels with the physically-based hydrological model BROOK90. The model was parameterised from eddy-covariance measurements and daily input was generated from MODIS leaf area index and surface temperatures. Modelled ET was also compared with the ET provided by the MODIS MOD16 ET data. The study showed ET to be highly variable in both time and space in Inner Mongolian grasslands. The mean coefficient of variation of 8-day ET in the study area varied between 25% and 40% and was up to 75% for individual pixels indicating a high innerannual variability of ET. Generally, ET equals or exceeds P during the vegetation period, but high precipitation in 2003 clearly exceeded ET in this year indicating a recharge of soil moisture and groundwater. Despite the high interannual and innerannual variations of spatial ET, the study also showed the existence of an intrinsic long-term spatial pattern of ET distribution, which can be explained partly by altitude and longitude (R(2) = 0.49). In conclusion, the results of this research suggest the development of dynamic and productive rangeland management systems according to the inherent variability of rainfall, productivity and ET in order to restore and protect Inner Mongolian grasslands.

No MeSH data available.


Related in: MedlinePlus

Spatiotemporal variability of T in 8-day intervals in the study area from 2002 to 2011.
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Fig9: Spatiotemporal variability of T in 8-day intervals in the study area from 2002 to 2011.

Mentions: The differentiated courses of E and T are shown as the probability density functions (PDF) and the courses of the components of ET (E, T and Ei) for a very wet (2003) and very dry year (2009) in Figure 8: here, the left side in the beanplots shows the PDF of all pixels for E (red colour) and the right side shows the PDF of T (green colour). While E and T as well as their spatial differences are small during the first three 8-day intervals (DOY 113–136) in both years, the stretched PDFs of E and T show a substantial increase and also the more pronounced spatial differences in 2003 afterwards. A slight increase of T occurs in 2009, but compared to the 2003 data, E and T stay on a very low level throughout the whole study period. Ei, which is visible from the difference between the + and the ▲in the figure, is also very small in 2009. In 2003 there are several 8-day intervals (e.g., from DOY 169–176 and DOY 185–192) with considerable amounts of Ei, up to 0.4 mm d-1 or approx. 15% of ET indicating high LAI and P. The spatiotemporal distribution of the variability of T is displayed in Figure 9. Here, the calculated CV of T is shown analogously to Figure 6 every 8 days, from 2002 to 2011. However, the spatial distribution of the CV of T is distinct from the spatial variability of ET in Figure 6. The spatial patterns of the CV in Figure 9 are different for each 8-day interval, but there are similarities, e.g., the CV is lower in the western and south-western part of the study area in spring and early summer (until approx. DOY 184) than the CV in the northern part. Afterwards, the difference between these areas is less pronounced, e.g., due to a decrease of the CV of T in the northern areas. Table 2 shows the T, E and Ei sums (23 April-28 August) as well as the T/ET ratios from 2002 to 2011. T was higher than E throughout the study period and the ratio between T and ET was relatively balanced (between 0.53 and 0.59) regardless of the amount of P. Ei accounts for 4% to 8% of ET.Figure 8


Variability and distribution of spatial evapotranspiration in semi arid Inner Mongolian grasslands from 2002 to 2011.

Schaffrath D, Bernhofer C - Springerplus (2013)

Spatiotemporal variability of T in 8-day intervals in the study area from 2002 to 2011.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4320196&req=5

Fig9: Spatiotemporal variability of T in 8-day intervals in the study area from 2002 to 2011.
Mentions: The differentiated courses of E and T are shown as the probability density functions (PDF) and the courses of the components of ET (E, T and Ei) for a very wet (2003) and very dry year (2009) in Figure 8: here, the left side in the beanplots shows the PDF of all pixels for E (red colour) and the right side shows the PDF of T (green colour). While E and T as well as their spatial differences are small during the first three 8-day intervals (DOY 113–136) in both years, the stretched PDFs of E and T show a substantial increase and also the more pronounced spatial differences in 2003 afterwards. A slight increase of T occurs in 2009, but compared to the 2003 data, E and T stay on a very low level throughout the whole study period. Ei, which is visible from the difference between the + and the ▲in the figure, is also very small in 2009. In 2003 there are several 8-day intervals (e.g., from DOY 169–176 and DOY 185–192) with considerable amounts of Ei, up to 0.4 mm d-1 or approx. 15% of ET indicating high LAI and P. The spatiotemporal distribution of the variability of T is displayed in Figure 9. Here, the calculated CV of T is shown analogously to Figure 6 every 8 days, from 2002 to 2011. However, the spatial distribution of the CV of T is distinct from the spatial variability of ET in Figure 6. The spatial patterns of the CV in Figure 9 are different for each 8-day interval, but there are similarities, e.g., the CV is lower in the western and south-western part of the study area in spring and early summer (until approx. DOY 184) than the CV in the northern part. Afterwards, the difference between these areas is less pronounced, e.g., due to a decrease of the CV of T in the northern areas. Table 2 shows the T, E and Ei sums (23 April-28 August) as well as the T/ET ratios from 2002 to 2011. T was higher than E throughout the study period and the ratio between T and ET was relatively balanced (between 0.53 and 0.59) regardless of the amount of P. Ei accounts for 4% to 8% of ET.Figure 8

Bottom Line: Modelled ET was also compared with the ET provided by the MODIS MOD16 ET data.Despite the high interannual and innerannual variations of spatial ET, the study also showed the existence of an intrinsic long-term spatial pattern of ET distribution, which can be explained partly by altitude and longitude (R(2) = 0.49).In conclusion, the results of this research suggest the development of dynamic and productive rangeland management systems according to the inherent variability of rainfall, productivity and ET in order to restore and protect Inner Mongolian grasslands.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hydrology and Meteorology, Technische Universität Dresden, Dresden, Germany ; Professur für Meteorologie, TU Dresden, Fakultät Umweltwissenschaften, PF 1117, 01735 Tharandt, Germany.

ABSTRACT
Grasslands in Inner Mongolia are important for livestock farming while ecosystem functioning and water consumption are dominated by evapotranspiration (ET). In this paper we studied the spatiotemporal distribution and variability of ET and its components in Inner Mongolian grasslands over a period of 10 years, from 2002 to 2011. ET was modelled pixel-wise for more than 3000 1 km(2) pixels with the physically-based hydrological model BROOK90. The model was parameterised from eddy-covariance measurements and daily input was generated from MODIS leaf area index and surface temperatures. Modelled ET was also compared with the ET provided by the MODIS MOD16 ET data. The study showed ET to be highly variable in both time and space in Inner Mongolian grasslands. The mean coefficient of variation of 8-day ET in the study area varied between 25% and 40% and was up to 75% for individual pixels indicating a high innerannual variability of ET. Generally, ET equals or exceeds P during the vegetation period, but high precipitation in 2003 clearly exceeded ET in this year indicating a recharge of soil moisture and groundwater. Despite the high interannual and innerannual variations of spatial ET, the study also showed the existence of an intrinsic long-term spatial pattern of ET distribution, which can be explained partly by altitude and longitude (R(2) = 0.49). In conclusion, the results of this research suggest the development of dynamic and productive rangeland management systems according to the inherent variability of rainfall, productivity and ET in order to restore and protect Inner Mongolian grasslands.

No MeSH data available.


Related in: MedlinePlus