Attributes of private yards along a rural-urban gradient in China highlight opportunities and limits to increase trees to benefit biodiversity and climate

Private residential yards are an important component of urban green space and a major contributor to the urban environment. Trees in private yards provide physical and psychological benefits, but little research has been done, for example, in China. This study examined the characteristics of 143 private residential yards and 955 yard trees across a range of villages and communities along a gradient from rural to peri-urban to urban in Zhoukou city, central China. Overall, 65% of dwellings had yards, and of these yard dwellings, 57% had trees. Yard size was the most significant constraint on the number of trees and the species planted. Trees in private yards were typically small as constrained by yard size. Available space, tree counts, species counts, and species diversity were all lowest in urban yards. Species composition was homogeneous across villages and communities, with a preference for edible species like persimmon and pomegranate in rural areas. Although small, private yards contributed significantly to the urban ecosystems. Three features of private yards, i.e. small trees, a small area available for trees, and homogenous species suggest the need for large trees, more trees, and richer biodiversity, e.g. in public spaces, to achieve the targets of urban green infrastructure. These insights into the attributes of private yard trees can improve greening strategies for sustainable urban and rural developments.