Predicting the distribution of Stipa purpurea across the Tibetan Plateau via the MaxEnt model

Abstract

Background: The ecosystems across Tibetan Plateau are changing rapidly under the influence of climate warming, which has caused substantial changes in spatial and temporal environmental patterns. Stipa purpurea, as a dominant herbsage resource in alpine steppe, has a great influence on animal husbandry in the Tibetan Plateau. Global warming has been forecasted to continue in the future (2050s, 2070s), questioning the future distribution of S. purpurea and its response to climate change. The maximum entropy (MaxEnt) modeling, due to its multiple advantages (e.g. uses presence-only data, performs well with incomplete data, and requires small sample sizes and gaps), has been used to understand species environment relationships and predict species distributions across locations that have not been sampled.

Results: Annual mean temperature, annual precipitation, temperature seasonality, altitude, and precipitation during the driest month, significantly affected the distribution of S. purpurea. Only 0.70% of the Tibetan Plateau area included a very highly suitable habitat (habitat suitability [HS] = 0.8-1.0). Highly suitable habitat (HS = 0.6-0.8), moderately suitable habitat (HS = 0.4-0.6), and unsuitable habitat (HS = 0.2-0.4) occupied 6.20, 14.30 and 22.40% of the Tibetan Plateau area, respectively, and the majority (56.40%) of the Tibetan Plateau area constituted a highly unsuitable habitat (HS = 0-0.2). In addition, the response curves of species ecological suitability simulated by generalized additive model nearly corresponded with the response curves generated by the MaxEnt model.

Conclusions: At a temporal scale, the habitat suitability of S. purpurea tends to increase from the 1990s to 2050s, but decline from the 2050s to 2070s. At a spatial scale, the future distribution of S. purpurea will not exhibit sweeping changes and will remain in the central and southeastern regions of the Tibetan Plateau. These results benefit the local animal husbandry and provide evidence for establishing reasonable management practices.

Keywords: MaxEnt; Model simulation; Species distribution; Stipa purpurea; Tibetan Plateau.

Fig. 1

The vegetation types of grasslands in Tibetan Plateau. The distribution point and source of S. purpurea in Tibetan Plateau.(S. purpurea I represents field survey sample; S. purpurea II represents Herbarium of Botany Institute, CAS; The Sample collection route stands for field survey roadmap in Tibetan Plateau) (a). Habitat suitability distribution of S. purpurea (b)

Fig. 2

The principal component analysis (PCA) of environmental variables (a). Correlation analysis of the independent variables (b), and the colored solid circles represent the significant correlation (P < 0.05)

Fig. 3

a Shows the value of AUC_test in different MaxEnt model settings (L = linear, Q = quadratic, H = hinge, P = product and T = threshold). b Represents the results of the AUC (area under ROC) curves in developing S. purpurea habitat suitability model. c Represents the results of the jackknife test of variables’ contribution in modeling S. purpurea habitat suitability distribution

Fig. 4

a Describes the response curves of 11 environmental variables in S. purpurea habitat distribution model. b Describes the MaxEnt verification results based on Generalized Additive Model (GAM)

Fig. 5

Based on MaxEnt forecast the spatial potential distribution of S. purpurea in 2050 s and 2070 s.(Based on RCP2.6 in 2050 s (a), Based on RCP2.6 in 2070 s (b), Based on RCP2.6 in 2050 s (c), Based on RCP8.5 in 2070 s (d). The area alteration of S. purpurea in current period, 2050 s and 2070 s Based on RCP2.6 (e); Based on RCP 8.5 (f)