Alpine Hummocks Drive Plant Diversity and Soil Fertile Islands on the Tibetan Plateau
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GENERAL WETLAND SCIENCE
Alpine Hummocks Drive Plant Diversity and Soil Fertile Islands on the Tibetan Plateau Hui Zhao 1 & Da Wei 1 & Yan Yan 1 & Jianbo Wu 1 & Xiaodan Wang 1 Received: 14 September 2019 / Accepted: 6 February 2020 # Society of Wetland Scientists 2020
Abstract Earth hummocks are widely distributed in arctic, sub-Arctic and alpine regions and have important roles in determining plant diversity and the nutrient content of soils. We investigated the impact of the spatial heterogeneity on soil properties and plant communities caused by the hummocks on the Tibetan Plateau. The results indicated alpine hummocks created higher plant diversity and soil fertile island patterns under Kobresia Genus communities. Vegetation height, cover, above-ground and underground biomass, species richness and diversity at the top of well-developed hummocks were the significantly higher than those in the inter-hummocks and surrounding flat ground. The soil organic carbon content in surface soil layer (0-50 cm) at the hummock top was 154.6% and 172.3% higher than those in inter-hummock area and the flat ground, respectively. From the developing to well-developed stage, K. littledalei became the dominant population at hummock top instead of K. humilis, and fertile islands gradually formed with higher soil organic carbon and total nitrogen, lower soil moisture and wider soil temperature variation. RDA analysis further indicated the interactions of plant community succession and soil fertile island could create positive feedbacks to nutrient-rich patches. Keywords Alpine hummock . Plant community diversity . Soil fertile island . Micro-topographic heterogeneity
Introduction In Arctic, sub-Arctic and alpine wetlands, one of the most widespread landform indicative of cryoturbation is earth hummock (Grab 1994, 2005; Scott et al. 2008; Peterson and Johnson 2018; Milošević et al. 2015; Li et al. 2017). Hummocks are small cryogenic mounds, generally domeshaped (Sharp 1942) and covered by grass. They are usually closely spaced on flat or gentle slopes ( TH_D > IH > FG (Fig. 5e, f). The micro-topography fluctuations of the hummocks favored the accumulation of soil carbon and nitrogen. In the 0-10 cm soil layer, the SOC at the TH_WD site was 17.1 g/kg higher than that at the IH site, and 15.8 g/kg higher than at the FG site. In the 40-50 cm soil layer, the SOC at the TH_WD site was only 4.5 g/kg higher than that at the IH site, and 3.1 g/kg higher than at the FG site (Fig. 5c, d). The closer
Importance value Top of Well-developed hummock
Top of developing hummock
Inter-hummock (IH)
Flat ground (FG)
0.464
0.176
0.212 0.128 0.006
0.160 0.248 0.064
0.449 0.277
0.409 0.222 0.047
0.006 0.026
0.037 0.042
0.274
0.031
0.037
0.067
0.071
0.020
0.039
0.070
0.065
0.115
0.150
0.034
0.051
50 40
a
a
30
a
20
a
10
b
100
Vegetation cover(%)
a
90
0 TH_D
IH
a
600 500
a
400
b
300
TH_WD
Shannon–Wiener diversity
TH_D
IH
Underground biomass (g m-2)
700
b
IH
FG
a 10,000
a 8,000
a a
1.80
a
1.60
1.4
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