Patterns Of Plant Invasions In China: Role Of Species Traits, Environment And Human Activities

Alien plant invasions cause serious damages to native biodiversity, environment, economy and human health. To better prevent and manage invasive plants, it's important to understand patterns of plant invasions, including aspects of distribution, spread, and impacts. There are 270 invasive plants in China, and most of the studies on invasion patterns mainly focused on their composition and distribution. China is a vast country with various climates and environmental conditions, and the invasive plants are also very diverse. In such cases the invasion patterns may be determined by multiple factors. Using data of the 270 invasive plants currently known in China, this study explores the following three questions: (1) Which invaders are most noxious? (2) Distribution of invaders at provincial scale in relation to species traits. (3) Which factors determine number of provinces occupied by an invader?Based on how many times an invader was studied, this study identified the most noxious plant invaders currently known in China. The most notorious invasive plants are 13 species with a perennial life cycle, clonal growth ability and from the American continent. They often form monocultural populations in land and water, replacing almost all other plants, and are mainly distributed in Central and South China. Following are 18 accidentally introduced annuals. Annuals from the American continent are often common, dominant or in monocultural populations in ruderal and agricultural habitats whereas those from Eurasia are highly noxious only in agricultural habitats. Annuals are not restricted in distribution and could spread fast to all of the country. There are also two perennial grasses from Europe and Mediterranean area and four intentionally introduced annuals from South America that were identified in this study. Factors that may account for these patterns include relatedness between invasives and natives, vegetative propagation, and plant strategies. The invasive plants identified in this study have caused significant negative impacts to native biodiversity, environment, economics and agriculture, with different groups being different in their extent and nature of impacts.Recently, lots of interests have been paid to examine distribution of invasive plants at provincial scale in China, and almost all of these studies suggest that distribution of invasive plants is associated with both socioeconomic and biogeographical factors. However, a fact lies in these literature is that they all studied invasive plants as a whole. By dividing invaders according to geographical origin and life cycle, here we show that distribution of invaders from Central and South America is mainly determined by biogeographical factors whereas distribution of invaders from North America and non-American continents is mainly determined by socioeconomic factors. Socioeconomic factors are also important for annuals from Central and South America, while biogeographical factors are also important for perennials from North America and non-American continents. The predictive power of biogeographical factors in invaders from Central and South America is stronger than socioeconomic factors in invaders from North America and non-American continents. Factors that may account for these patterns include habitat requirements of invaders, adaptation ability, and the nature of socioeconomic and biogeographical factors in China. Role of socioeconomic and biogeographical factors are not entangled, instead, their relative importance is dependent on the intrinsic traits of species such as their geographical origin and life cycle. As plant invasions in China are an ideal natural experiment to examine how both intrinsic and extrinsic factors operate independently and interactively to determine distribution, the results of this study also have broad implications for other countries and regions.The extensive area and diverse climates in China make the plant invasions an ideal natural experiment to examine how multiple factors operate independently and interactively to determine the geographical extent. Data on provincial distribution of invasive plants in China were collected, and species attributes such as biogeographical origin, life cycle, time since introduction and impacts were gathered. While annuals may eventually occupy the whole country, perennials are unlikely to do so, especially those from Central and South America. Time since introduction is related to number of provinces occupied by an invader, and after control of residence time, annuals don't occupy a larger number of provinces than the perennial herbs do. High-impact invaders spread faster than other invaders, but only when life cycle was taken into account. Species in a single life cycle group may differ greatly in invasive success, and further studies need to explore how other traits, along with human activities and environment, determine invasive spread and distribution.China's booming economy will accelerate plant invasions, and we should understand patterns of plant invasions. Previous studies tend to explain invasion patterns from a single factor, and our results suggest that it may be difficult to understand invasion patterns deeply. To study each aspect of invasion patterns, we need to include multi-factors and their possible interactions. Determinants of different aspects of invasions patterns are also different. To better prevent and manage invasive plants, further studies are needed to explore more points associated impacts and mechanisms of invasion.