Chin J Plan Ecolo ›› 2016, Vol. 40 ›› Issue (12): 1245-1256.doi: 10.17521/cjpe.2015.0389

• Research Articles • Previous Articles     Next Articles

Changes in normalized difference vegetation index of deserts and dunes with precipitation in the middle Heihe River Basin

Fang LI1,2, Wen-Zhi ZHAO2,*   

  1. 1Research Institute of Grassland Science, Chinese Academy of Agricultural Sciences, Hohhot 010010, China
    2Institute of Northwestern Eco-environment and Resource, Chinese Academy of Sciences, Linze Inland River Basin Research Station, Chinese Ecosystem Research Network, Lanzhou 730000, China
  • Online:2016-12-30 Published:2016-12-31
  • Contact: Wen-Zhi ZHAO

Abstract: AimsPrecipitation is the major water source for desert ecosystems, with its temporal dynamics significantly driving the changes of ecosystem structure and function in desert regions. The objectives of this study are to evaluate the changes in normalized difference vegetation index (NDVI) with seasonal precipitation and different climate years in two cover types (desert and dune).MethodsBased on the daily rainfall dataset of 2000-2012 in the middle Heihe River Basin in Northwest China and the NDVI extracted from the moderate resolution imaging spectroradiometer (MODIS) images, we performed linear regression analysis to examine the correlation of NDVIINT (accumulated NDVI) with precipitation in two cover types (desert and dune). Two measures of the precipitation are Pc (cool-season precipitation from last September to late February) and Pw (warm-season precipitation in between March and August), while NDVI was characterized with NDVIINT-pys (previous-year during the different climate years (dry: 2001-2003, wet: 2004-2007)) and the different periods of a growing season (i.e. whole growing season from May through September, early growing season in between May and June, and late growing season in between July and September).Important findings We found that: (1) the determinants of growing season NDVIINT and their order were NDVIINT-pys > Pc > Pw for the deserts, while the order was Pw > NDVIINT-pys for the dunes. The determinants and their order of NDVIINT in early growing season were NDVIINT-pys > Pc for the desert, while they were NDVIINT-pys > Pc = Pw for the late growing season. However, for the dunes, NDVIINT of the early and late growing season appeared determined by NDVIINT-pys and Pw, respectively. (2) During the dry and wet periods, precipitation was not a significant factor influencing NDVIINT for the desert and dune. However, significant increases in NDVIINTwere observed at dune under wet condition. With the wet years continued, the length of the wet years become an important determinant of NDVIINT at both cove types, particularly at dune. In addition, it appeared that different changes in NDVI with precipitation existed between the two cover types, but with very similar effects of time-lag. These findings provide useful references for further understanding the mechanisms of NDVI changes with precipitation.

Key words: accumulated normalized difference vegetation index (NDVIINT), precipitation of cold season, precipitation of warm season, dry and wet climate period, lag time, ecohydrology

Fig. 1

The locations of study area."

Table 1

Vegetation and soil characteristics of desert and dune ecosystem located in study area (mean ± SE)"

特征 Characteristics 沙质荒漠 Dune 砾质荒漠 Desert
Vegetation properties
灌木盖度 Shrub cover (%) 12.2 ± 2.8 11.2 ± 1.4
草本盖度 Grass cover (%) 17.5 ± 2.1 2.4 ± 0.3
植被高度 Vegetation height (cm) 67 ± 23 19 ± 9
Average normalized difference vegetation index (NDVI)1)
0.132 ± 0.014 0.075 ± 0.008
物种丰富度 Species richness 18 11
建群种 Dominant species 泡泡刺 Nitraria sphaerocarpa,
沙拐枣 Calligonum mongolicum
红砂 Reaumurta soongorica,
泡泡刺 Nitraria sphaerocarpa
Soil properties
砂粒-粉粒-黏粒 Sandy-silt-clay (0-20 cm) (%) 90-7-32) 73-23-43)
容重 Bulk density (0-20 cm) (g·m-3) 1.57 ± 0.104) 1.63 ± 0.193)
总孔隙度 Pore space (0-20 cm) (%) >39 39 ± 73)
土壤水分 Soil water content5) (0-20 cm)(%) 1.78 ± 0.46 2.10 ± 0.68
土壤水分 Soil water content5) (20-40 cm)(%) 2.09 ± 0.42 2.81 ± 0.62
土壤水分 Soil water content5) (40-60 cm)(%) 2.13 ± 0.60 2.27 ± 0.31
土壤水分 Soil water content5) (60-180 cm)(%) 2.02 ± 2.23 1.79 ± 0.33

Table 2

Major characteristics of precipitation in the study area during the different hydrological years in the study basin"

年份 Years 降水 Precipitation (mm) 气候期 Climate period 年份 Year 降水 Precipitation (mm) 气候期 Climate period
1999 75.8 非干旱或湿润期
No dry or wet period
2008 111.6 非干旱或湿润期
No dry or wet period
2000 118.4 2009 87.3
2001 55.7 干旱期
Dry period
2010 143.5
2002 106.4 2011 188.1
2003 62.5 2012 105.8
2004 134.3 湿润期
Wet period
2013 113.2
2005 116.2 平均值* 109.7
2006 122.2 Mean*
2007 140.2

Fig. 2

Distribution of precipitation in Linze County. “a”, the precipitation data from 1968 to 2000; “b”, the precipitation data from 2001 to 2012."

Table 3

F-statistical analysis of frequency and precipitation of small (<5 mm) and large rainfall (>10 mm) events during 1968-2000 and 2001-2012 in different seasons (spring, summer, fall and winter)"

降水 Precipitation 因素 Factor 自由度 df F p
<5 mm降水 precipitation 发生次数 Frequency 季节 Season 3 18.433 <0.001
时间段 Period of time 1 6.223 0.014
季节×时间段 Season × Period of time 3 3.206 0.025
降水量 Precipitation 季节 Season 3 30.218 <0.001
时间段 Period of time 1 3.305 0.071
季节×时间段 Season × Period of time 3 2.950 0.034
>10 mm降水 precipitation 发生次数 Frequency 季节 Season 3 27.355 <0.001
时间段 Period of time 1 0.477 0.491
季节×时间段 Season × Period of time 3 0.606 0.612
降水量 Precipitation 季节 Season 3 25.799 <0.001
时间段 Period of time 1 0.147 0.702
季节×时间段 Season × Period of time 3 1.150 0.331

Fig. 3

Relationships between the growing season accumulated normalized difference vegetation index (NDVIINT) (early growing season, late growing season) and precipitation during the wet and dry years in dune and desert ecosystems. Triangles, rectangles and circles indicated NDVIINT in dry years (2001-2003), wet years (2004-2007), and normal years (2000, 2008-2012), respectively. R2, Rd2, Rw2 and p, pd, pw indicated the adjusted coefficient of determination and the probability values of significance test at dry and wet climate period (2001-2007), dry years, wet years."

Fig. 4

Changes of precipitation during the wet and dry years at dune and desert."

Fig. 5

Changes of accumulated normalized difference vegetation index (NDVIINT) during the wet and dry years at dune and desert. Triangles, rectangles and circles indicated NDVIINT in dry years (2001-2003), wet years (2004-2007) and no-trend years (2000, 2008-2012), respectively. The number of consecutive wet years is indicated in the quadratic function of the independent variable (x)."

Table 4

Linear regression models for the relationships between the accumulated normalized difference vegetation index (NDVIINT) of the entire- (May to September), early- (May to June), and late-growing-season (July to September) precipitation for different periods of the year at dunes and deserts"

研究区 Sites 线性回归方程 Linear regression formula R2 r2
Growing season
砾质荒漠 Desert pt = 1.037 + 0.003xc + 0.003xw R2 = 0.46* rc2 = 0.29*; rw2 = 0.17*
沙质荒漠 Dune pt = 1.480 + 0.005xc + 0.007xw R2 = 0.33* rc2 = 0.03; rw2 = 0.29*
早期 Early 砾质荒漠 Desert pt = 0.492 + 0.001xc + 0.001xs R2 = 0.26* rc2 = 0.23*; rs2 = 0.04
沙质荒漠 Dune pt = 0.734 + 0.001xc + 0.002xs R2 = 0.08 rc2 = 0.02; rs2 = 0.06
晚期 Late 砾质荒漠 Desert pt = 0.604 + 0.002xc + 0.002xw R2 = 0.42* rc2 = 0.22*; rw2 = 0.20*
沙质荒漠 Dune pt = 0.822 + 0.003xc + 0.002xw R2 = 0.35* rc2 = 0.01; rw2 = 0.34*

Table 5

Linear regression models for the relationships between the accumulated normalized difference vegetation index (NDVIINT) of the entire- (May to September), early- (May to June), and late-growing-season (July to September) precipitation and hydrological year precipitation (Ph) and the previous normalized difference vegetation index (NDVIINT-pys) at dune and desert"

研究区 Sites 线性回归方程 Linear regression formula R2 r2
生长季 Growing season 砾质荒漠 Desert pt = 0.384 + 0.003xh + 0.527pt-1 R2 = 0.73* rh2 = 0.40*; rt-12 = 0.34*
沙质荒漠 Dune pt = 0.659 + 0.005xh + 0.466pt-1 R2 = 0.60* rh2 = 0.35*; rt-12 = 0.24*
早期 Early 砾质荒漠 Desert pt = 0.245 + 0.001xc + 0.192pt-1 R2 = 0.47* rc2 = 0.20*; rt-12 = 0.27*
沙质荒漠 Dune pt = 0.427 + 0.001xc + 0.170pt-1 R2 = 0.49* rc2 = 0.01; rt-12 = 0.48*
晚期 Late 砾质荒漠 Desert pt = 0.140 + 0.002xh + 0.378pt-1 R2 = 0.70* rh2 = 0.34*; rt-12 = 0.36*
沙质荒漠 Dune pt = 0.262 + 0.004xh + 0.325pt-1 R2 = 0.50* rh2 = 0.33*; rt-12 = 0.17
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