GR | 气候和人类活动驱动了蒙古高原草地一年生和多年生C4植物多度的变化

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Table 1. Frequency of occurrence and life forms of C4 species across the 280 sampling sites

Figure 1: Isolines of 15% and 30% for the regional relative biomass of C4 annuals (P_A4); the mean krige standard deviation for the study area is 9%. The blue color denotes the regional relative biomass of C4 plants (P_C4). P_C4 estimated for recent vegetation is taken from Auerswald et al. (2009); the mean krige standard deviation is 9%. Towns are A, Abag Qi; B, Baochang; BS, Bayan Sum; D, Dong Ujimqin Qi; E, Erenhot; HQ, Xianghuang Qi; SW, Siziwang Qi; SY, Sonid Youqi; SZ, Sonid Zuoqi; XH, Xilinhot; XU, Xi Ujimqin Qi.

Figure 2: Variations in the relative biomass of C4 (P_C4) and C3 (P_C3) plants during 2001–2009. P_C4 is further divided into C4 annuals (P_A4) and C4 perennials (P_P4), and P_C3 is divided into C3 annuals (P_A3) and C3 perennials (P_P3). Each filled circle is the average of all field sites within each year. The number of sites is 15 in 2001, 75 in 2002, 45 in 2003, 33 in 2004, 12 in 2006, 20 in 2007, 65 in 2008, and 15 in 2009. The open circles denote a small area (see text) sampled in most years (the number of sites varies between 8 in 2001 and 60 in 2008). Error bars denote standard errors (SEs). Regression lines are for the open circles (P_A4: R²= 0.84, p = 0.010; P_P4: R²= 0.73, p = 0.032). For clarity, SEs are only given for the entire study area. For the small area, they are slightly larger (overall mean SE = 1.2%).

Figure 3: Density distribution of the relative biomass of C4 annuals in C4 plants. The integral density is 1.

Figure 4: Responses of the relative biomass of all C4 plants, C4 annuals, and C4 perennials to wetness of the growing season. Dry, normal, and wet years were classified by the SPEI-4 values for August in the sampling year. Error bars denote SE. For each group, different letters indicate significant differences at p < 0.05.

Figure 5: Structural equation modeling (SEM) analysis examining the effect of temperature, precipitation, and C4 perennials (P_P4) on the relative biomass of C4 annuals (P_A4). The initial constructed model of the SEM is explained in the Supporting Information: Figure S1). Square boxes indicate the variables included in the model. Results of model fitting: χ2 = 5.483, p = 0.241, df = 4, N = 267. (Note that high p values associated with χ2 tests indicate good model fit to data, that is, no significant discrepancies). Solid arrows connecting the boxes indicate significant positive and negative effects (p < 0.05), respectively; the pathways without significant effects are indicated by broken lines (p > 0.05). r² values associated with response variables indicate the proportion of variation explained by relationships with other variables. Values associated with solid arrows represent standardized path coefficients. JulP, current year July precipitation; JulT, current year July temperature; MJulP, mean July precipitation; MJulT, mean July temperature; P_A4, C4 annuals; P_P4, C4 perennials.

Figure 6：Responses of the relative biomass of all C4 plants, C4 annuals, and C4 perennials to grazing. Each value is the average of the relative biomass of recently grazed (N = 32) or ungrazed sites (N = 32). Error bars denote SE. NS represents no significant difference within a group (p > 0.05).

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 Grassland Research是我国草业科学领域第一本国际学术期刊，季刊，由中国草学会和兰州大学共同主办。该刊受中国科技期刊卓越计划高起点新刊项目支持，由国际出版集团John Wiley & Sons Australia, Ltd.提供出版及宣传服务，于2022年正式创刊。

 Grassland Research论文刊发范围广，综合性强。从分子到全球变化层面，全维度聚焦草业科学及其在人类可持续发展中的作用。期刊将刊登天然草原，栽培草地、草坪和生物能源作物，以及草地生态系统三大板块的基础性和应用性研究成果、综述、论点等类型的文章。优先考虑发表青年学者优秀研究成果，期待成为青年科学家喜爱的国际学术交流主阵地。

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