Effects of acid rain on plant growth: A meta-analysis.

Anthropogenic driven acid gases emission has caused acid rain in many regions globally. Although efforts have been made to assess the effects of acid rain on terrestrial ecosystems, a systematic assessment of growth-related traits across plant aboveground and belowground is lacking. Hence, we performed a phylogenetically controlled meta-analysis of 755 observations from 69 independent studies to quantify the effects of acid rain on six growth-related traits of plant. We estimated the inhibitory effects of acid rain on plant growth in general and found that aboveground and belowground plant parts responded differently. The acidity of acid rain and acid rain interval had direct modulation effects on plant growth. We also found that there were interactions between acid rain pH and other acid rain characteristics (i.e., acid rain interval, mole ratio of S:N, and acid rain rate) and experimental characteristics (i.e., initial soil pH and plant exposure part), indicating that there were pH-dependent interaction patterns. Thus, an effective approach to evaluate and predict the effects of acid rain on plant growth is to fully consider the direct effects of acid rain pH and the interactions between acid rain pH and other factors.