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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

The annual courses (2002 to 2011) of the mean ET (grey bars) and P (black bars) in the study area from 23 April (DOY 113) to 28 August (DOY 240).
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Fig4: The annual courses (2002 to 2011) of the mean ET (grey bars) and P (black bars) in the study area from 23 April (DOY 113) to 28 August (DOY 240).

Mentions: The characteristics of the annual courses of the mean ET in the study area are quite diverse (Figure 4), but ET is low (between 0.3 mm d-1 and 0.6 mm d-1) at the end of April (DOY 113–120) in every year. A substantial increase of ET occurs in every year, but with significant differences in the date and in the magnitude of the increase: in some years, spring and early summer ET increased gradually (e.g., in 2004, 2007 and 2011). In 2006 and 2008 a considerable increase of ET occurred late, at the beginning of June (between DOY 153 and DOY 160). The mean maximum ET of 8-day intervals in the grasslands ranged from very low 1.4 mm d-1 in 2009 up to 2.4 mm d-1 (in 2003 and 2011). However, the highest ET of a single pixel was 5.2 mm d-1 during an 8-day period in July of 2003 (DOY 185–192). The date of peak-ET was highly variable too; it occurred very early in 2010 (at the beginning of June, DOY 153–160) and very late in 2007 (in the mid of August, DOY 225–232). Also, the temporal distribution of ET showed a unimodal distribution in 2005 and 2006, a bimodal distribution in 2008 and a multimodal distribution, e.g., in 2002 and 2004. In general, ET declines in August and is between 0.6 mm d-1 and 1.3 mm d-1 during the last 8-day interval of the study period (DOY 233–240).Figure 4


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

Schaffrath D, Bernhofer C - Springerplus (2013)

The annual courses (2002 to 2011) of the mean ET (grey bars) and P (black bars) in the study area from 23 April (DOY 113) to 28 August (DOY 240).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig4: The annual courses (2002 to 2011) of the mean ET (grey bars) and P (black bars) in the study area from 23 April (DOY 113) to 28 August (DOY 240).
Mentions: The characteristics of the annual courses of the mean ET in the study area are quite diverse (Figure 4), but ET is low (between 0.3 mm d-1 and 0.6 mm d-1) at the end of April (DOY 113–120) in every year. A substantial increase of ET occurs in every year, but with significant differences in the date and in the magnitude of the increase: in some years, spring and early summer ET increased gradually (e.g., in 2004, 2007 and 2011). In 2006 and 2008 a considerable increase of ET occurred late, at the beginning of June (between DOY 153 and DOY 160). The mean maximum ET of 8-day intervals in the grasslands ranged from very low 1.4 mm d-1 in 2009 up to 2.4 mm d-1 (in 2003 and 2011). However, the highest ET of a single pixel was 5.2 mm d-1 during an 8-day period in July of 2003 (DOY 185–192). The date of peak-ET was highly variable too; it occurred very early in 2010 (at the beginning of June, DOY 153–160) and very late in 2007 (in the mid of August, DOY 225–232). Also, the temporal distribution of ET showed a unimodal distribution in 2005 and 2006, a bimodal distribution in 2008 and a multimodal distribution, e.g., in 2002 and 2004. In general, ET declines in August and is between 0.6 mm d-1 and 1.3 mm d-1 during the last 8-day interval of the study period (DOY 233–240).Figure 4

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