Current methods that utilize simple data or models to evaluate soil restoration under ecological restoration are not sufficiently rigorous.Soil restoration under ecological restoration measures was evaluated in the red soil hilly region of China by applying the catastrophe model.Among 89 soil sites selected,26(29.21%) were in the middle lobe,10(11.24%) in the upper lobe,and 53(70.79%)in the lower lobe of the process surface in the Cusp catastrophe model.The catastrophic direction of the 26 unstable soil sites was to the upper lobe of the process surface according to vegetation cover change and fieldwork.There was a significant negative correlation of the variation in bifurcation set(? value) with vegetation cover increase,and a higher vegetation cover increase was related to higher unstable probability.The four ecological restoration measures were listed in the order:low-quality forest improvement(LQFI)>arbor-bush-herb mixed plantation(ABHMP)>orchard improvement(OI)>closing measures(CM) according to the proportions of unstable soil sites,which were all higher than no restoration measure,while they were in the order:LQFI
Declining soil fertility has become an increasingly urgent problem and gathering firewood is one of the important contributing factors.Due to the excessive exploitation of natural resources especially for firewood,the red soil hilly region has become one of the most vulnerable eco-environment regions in China.The pressure of gathering firewood on forestland soil fertility in forestland has been generally estimated by geographical information system and questionnaire method in this paper in the Zhuxi watershed of Changting County,Fujian Province,China,a typical representative in the red soil hilly region of China.The results of this study show that:i) Forestland soil fertility is negatively affected by gathering firewood,which is more intensive in the integrated buffer zone than out of zone.The forestland soil fertility grade,OM,total N,available N,total P,available P,total K,available K,pH and <2μm clay content are lower and bulk density is higher in the integrated buffer zone than those out.ii) The forestland soil fertility grade,OM,total N,available N,total P,available P,total K,available K,pH and <2μm clay content tend to be lower and bulk density tends to be higher in the village buffer zones than those out in Datian,Chenguang and Youfang respectively.iii) The population density,economic development and terrain might be the key driving forces contributing to the relationship between gathering firewood and forestland soil fertility.Higher population density leads to more massive firewood collection and imposes more pressure on forestland soil fertility.Decreasing the use of firewood stove may reduce firewood consumption and thus release the pressure of gathering firewood on forestland soil fertility.Terrain affects the accessibility to gathering firewood thus affects forestland soil fertility.Other driving forces influencing the relationship between gathering firewood and forestland soil fertility should also be taken into account in the further study.
