Regional Scale In China Research Articles

Human disturbance, climate and biodiversity determine biological invasion at a regional scale

Many factors may affect biological invasion, but their effects have not been quantitatively calculated. Recent studies on the relationship between biodiversity and biological invasion are still controversial. Native biodiversity and alien species diversity are often positively correlated in large-scale observation studies, but negatively correlated in small-scale experimental studies. By using partial correlation and principal component regression methods, we found that human disturbance, climate, native biodiversity and their interactions explained, respectively, 30.3, 34.6, 26.4 and 4.4% of the variation in alien species diversity (ASD) and 50.3, 22.2, 10.8 and 5.5% of the variation in the relative invasibility of alien species (RIA = ASD/native biodiversity) at the regional scale in China. The correlation between ASD and native biodiversity is positive, but the correlation between RIA and native biodiversity is negative. Island and coastal provinces have suffered heavier biological invasions than inland provinces. These findings indicate that biological invasion is mostly determined by human disturbance and favorable climate, but less determined by native biodiversity. A disturbance-dependent niche-vacancy hypothesis is proposed to explain the contradictory observations in large-and small-scale studies.

Acid rain and acidification in China: the importance of base cation deposition

Acid deposition has been recognized as a serious environmental problem in China. Most acid deposition studies have focused on sulfur deposition and the pH of precipitation. However, as high concentration of alkaline dust is an important feature of the atmosphere in large parts of China, base cation deposition must be taken into account when discussing possible effects on soils and vegetation from acid deposition. We estimate the deposition of sulfur as well as calcium, i.e. the dominating anion and cation, on a regional scale in China using data both from measurements and modeling. The ratio of sulfur/calcium in deposition is then used as an indicator for identifying areas where deposition acidity exceeds alkalinity, and where soils may be at risk to acidification. The dynamic soil acidification model MAGIC is applied with data from two sites receiving high deposition loads in southwest China. The model predictions indicate that considerable soil acidification has been going on for the last decades due to acid deposition inputs. Effects on the spatial distribution of acidic deposition in China, using different future deposition scenarios, are illustrated. As the size of the anthropogenic fraction of the base cation deposition is unknown, different possible future trends in calcium deposition were used. Soil response, according to the model, using different combinations of sulfur and calcium deposition scenarios is shown. Applying the most strict measures to reduce sulfur emission will almost eliminate the acid deposition problem; however, such a scenario is not economically feasible in the short term. A strict, but possibly realistic, future scenario for sulfur may be enough to keep the situation at the present level, assuming only moderate reductions in calcium deposition. With large decreases in base cation deposition, increased soil acidification can be expected even with considerable sulfur emission reductions.