Invasive Plant Species Distribution

Diversity 2022, 14, 167 2 of 16 and increase invasibility, depending on traffic volume, road density, road and other features of transportation corridors [20,21,25]. age, road type, China is one of the countries most vulnerable to invasive species (e.g., Eichhornia crassipes (Mart.) Solms, Ageratina adenophora (Spreng.) R.King & H.Rob., and Solenopsis invicta Bu- ren, 1972) [21,26-29]. Currently, it contains more than 500 invasive plant species (e.g., Solidago Canadensis L., Bidens pilosa L., and Spartina alterniflora Loisel.), including more than 30 malignant invasive species [30-32] (http://www.iplant.cn/ias/, accessed on 1 January 2022). Chinese grasslands contain more than 200 invasive plant species (e.g., Alternanthera philoxeroides (Mart.) Griseb., Chromolaena odorata (L.) R.King & H.Rob., and Erigeron sumatrensis Retz.) [32]. Southwest China is an important route for invasive species from Southeast Asia to inland China [30,33,34]. For example, Ageratina adenophora, native to Central Amer- ica, has been spreading into Southern China since the 1940s through Burma and Viet- nam [21]. The species is dispersing northwards and eastwards at an average speed of 20 km year¹ from the Yunnan-Guizhou Plateau to inland China [35]. Chromolaena odorata, also native to Central America, has spread to Southern China since the 1930s through Thailand [21]. Guizhou Province, located in Southwest China and a typical karst moun- tainous region, has one of the highest invasion risks in the country [36]. According to a previous study, the province hosts 30 invasive plant species [37], and subsequent studies mainly explored invasive plants in different regions of Guizhou Province and in some nature reserves (including Hongfeng Lake, Dashahe Nature Reserve, and Zhaozishan Nature Reserve, among others). For example, one study found 67 invasive plant species in Tongren City in the northeast [38], whereas other authors found 52 invasive plant species in Hongfeng Lake, Baihua Lake, and the Aha reservoir of Guiyang City in Central Guizhou [39]. Guo et al. determined 46 invasive plant species using 380 plots in the four nature reserves Chishui Alsophila, Xishui, Fanjingshan, and Mayanghe [40]. Other authors found 29, 16, 19, and 112 invasive plant species in Dashahe Nature Reserve [41], Zhaozishan Nature Reserve [42], Bijiang National Wetland Park [43], and Leigong Moun- tain National Nature Reserve [44]. Other studies focused on the histories, physiologi- cal and ecological characteristics, and potential distributions of specific invasive plants, including Ageratina adenophora [35,45-47], Chromolaena odorata [48,49], Soliva anthemifolia R.Br. [50], Xanthium mongolicum Kitag. [50,51], Alternanthera philoxeroides [52,53], Eichhornia crassipes [47], Solanum aculeatissimum Jacq. [47], Ambrosia trifida L. [54], Ageratum conyzoides L. [55], Cyclospermum leptophyllum (Pers.) Sprague ex Britton & P.Wilson [56], and Mikania micrantha Kunth [49,57]. Despite these efforts, there is no complete list, and the distribution patterns of invasive plant species in the grasslands of Guizhou Province, Southwest China, as well as the factors affecting their growth, are largely unclear. In this context, the objectives of this paper were to (1) provide a catalogue of invasive plants in the grasslands of Guizhou Province, (2) quantify the spatial distribution patterns of these plants, (3) quantify the factors affecting the distribution patterns, and (4) explore ap- propriate invasive plant management strategies in the grasslands of the Guizhou Province of China. 2. Materials and Methods This study was conducted in Guizhou Province, Southwest China (24°37'-29°13' N, 103°36'-109°35' E; 150-2900 m elevation; Figure 1). The climate is a humid subtropical monsoon climate, with a mean (1981-2010) annual temperature of 14.2 °C and a mean annual precipitation of 1069.9 mm. The mean daily temperatures of the coldest (January) and warmest (July) months are 4.4 and 22.2 °C, respectively (data from the China Meteo- rological Data Center; https://data.cma.cn/, accessed on 11 July 2021). Although forest is the main vegetation type, there are about 200,000 hectares of grassland including nat- ural grasslands, artificial grasslands, and abandoned fields in Guizhou Province (data from the third national land survey of China). According to the FAO 90 taxonomy [58], the main soils are Haplic Alisols, Haplic Luvisols, and Dystric Regosols. The terrain is a

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