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Journal of Arid Land  2020, Vol. 12 Issue (4): 618-629    DOI: 10.1007/s40333-020-0055-0
Research article     
Relationship of species diversity between overstory trees and understory herbs along the environmental gradients in the Tianshan Wild Fruit Forests, Northwest China
Junhui CHENG1, Xiaojun SHI1, Pengrui FAN1, Xiaobing ZHOU2, Jiandong SHENG1, Yuanming ZHANG2,*()
1 Xinjiang Key Laboratory of Soil and Plant Ecological Processes, College of Grassland and Environmental Sciences, Xinjiang Agricultural University, Urumqi 830052, China
2 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
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In forest ecosystems, interactions between overstory trees and understory herbs play an important role in driving plant species diversity. However, reported links between overstory tree and understory herb species diversity have been inconsistent, due to variations in forest types and environmental conditions. Here, we measured species richness (SR) and diversity (Shannon-Wiener (H') and Simpson's (D) indices) of overstory trees and understory herbs in the protected Tianshan Wild Fruit Forest (TWFF), Northwest China, to explore their relationships along the latitudinal, longitudinal, elevational, and climatic (current climate and paleoclimate) gradients in 2018. We found that SR, and H' and D diversity indices of overstory trees and understory herbs exhibited a unimodal pattern with increasing latitude and elevation (P<0.05) and negative associations with longitude (P<0.01). Along the climatic gradients, there were U-shaped patterns in SR, and H' and D diversity indices between trees and herbs (P<0.05). SR, and H' and D diversity indices for overstory tree species were positively associated with those for understory herbs (P<0.01). These findings indicate that overstory trees and understory herbs should be protected concurrently in the TWFF to increase effectiveness of species diversity conservation programs.

Key wordsdiversity indices      overstory trees      understory herbs      paleoclimate      current climate      elevation     
Received: 20 December 2019      Published: 10 July 2020
Corresponding Authors: Yuanming ZHANG     E-mail:
About author: *Corresponding author: ZHANG Yuanming (E-mail:
Cite this article:

CHENG Junhui, SHI Xiaojun, FAN Pengrui, ZHOU Xiaobing, SHENG Jiandong, ZHANG Yuanming. Relationship of species diversity between overstory trees and understory herbs along the environmental gradients in the Tianshan Wild Fruit Forests, Northwest China. Journal of Arid Land, 2020, 12(4): 618-629.

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Fig. 1 Distribution of the study sites
Sites Latitude (°N) Longitude (°E) Elevation (m) MAT (°C) MAP (mm)
Emin 46.37 83.99 1255.0 3.2 266
Tuoli 46.15 83.55 843.8 5.7 235
Huocheng 44.43 80.79 1173.2 7.0 196
Gongliu 43.24 82.72 1261.0 6.4 196
Xinyuan 43.38 83.60 1406.0 5.6 225
Table 1 Geographic location, elevation, mean annual temperature (MAT) and mean annual precipitation (MAP) of the study sites
Fig. 2 Principal component analysis (PCA) of variation in environmental variables along the latitudinal gradient. MAP, mean annual precipitation; MAT, mean annual temperature; MTCQ, mean temperature of coldest quarter; PCQ, precipitation of coldest quarter. MAPano, MATano, MTCQano, and PCQano are anomaly values of MAP, MAT, MTCQ, and PCQ since the Last Glacial Maximum, respectively. PC1 and PC2 represent the first and second principal components, respectively.
Fig. 3 Trends in species richness (SR), and Shannon-Wiener (H′) and Simpson′s (D) diversity indices for tree and herb species along the latitudinal (a-f) and longitudinal (g-l) gradients. Estimated relationship (solid line) was fitted with confidence intervals (dashed lines) at P=0.05 level.
Fig. 4 Trends in SR, and H′ and D diversity indices for tree and herb species along the PC1 (a-f) and PC2 (g-l) environmental gradients. Estimated relationship (solid lines) was fitted with confidence intervals (dashed lines) at P=0.05 level. NS, no significant relationship. Positive (+) and negative (-) signs indicated change in direction of environmental variables along the PC1 and PC2 environmental gradients.
Fig. 5 Relationships of SR, and H′ and D diversity indices of trees with herbs (a-c), forbs (d-f), and graminoids (g-i). Estimated relationship (solid line) was fitted with confidence intervals (dashed lines) at P=0.05 level. NS, no significant relationship.
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