ABSTRACT
The process of vegetation restoration is often accompanied by significant changes in aboveground plant diversity. To explore the driving mechanism of litter nutrient-soil nutrient-enzyme activity stoichiometry on aboveground vegetation change is of great importance for maintaining regional biodiversity conservation and ecological stability. Taking typical abandoned farmland of different restoration years ï¼1ï¼ 8ï¼ 16ï¼ 31ï¼ and 50 aï¼ in the Qinling Mountains as the research objectï¼ the variation characteristics of plant community diversity during vegetation restoration were analyzed through field investigation. Litter nutrientsï¼ soil nutrientsï¼ and the activities of five extracellular enzymesï¼ including ß-1ï¼4-glucosidase ï¼BGï¼ï¼ cellobiohydrolase ï¼CBHï¼ï¼ ß-1ï¼4-N-acetylglucosaminidase ï¼NAGï¼ï¼ leucine aminopeptidase ï¼LAPï¼ï¼ and acid phosphatase ï¼APï¼ï¼ were determined. The characteristics of litter nutrientsï¼ soil nutrientsï¼ and enzyme stoichiometric ratios during vegetation restoration and the driving mechanism of plant diversity changes were discussed. The results showed that the plant community diversity index firstly decreased and then increased with the increase in vegetation restoration yearsï¼ and the minimum was reached at 16 years after restoration. The results of principal component analysis showed that there were significant differences between total plant community diversity index and litter-soil-enzyme stoichiometric characteristics in different years of vegetation restoration. The plant community diversity index had a strong positive correlation with litter Câ¶P ratio and litter Nâ¶P ratio but had a negative correlation with soil enzyme Câ¶P ratio ï¼EEA Câ¶Pï¼. The results of redundancy analysis showed that soil EEA Câ¶P had the highest explanation rate of plant diversity changes during vegetation restoration ï¼25.93%ï¼ï¼ followed by soil TP ï¼5.94%ï¼ï¼ which was the key factor regulating plant diversity changes. In conclusionï¼ plant species and quantity increased significantly in abandoned farmland in the middle part of the Qinling Mountains at the late stage of vegetation restoration. Changes in the soil environment affected microbial metabolic activities and thus changed enzyme activities. Litter-soil-soil extracellular enzymes affected the community environment and plant diversity through feedback and regulation. EEA Câ¶P and TP were the main driving factors of aboveground plant diversity change during vegetation restoration.
Subject(s)
Biodiversity , Plants , Soil , Soil Microbiology , Nutrients , Ecosystem , ChinaABSTRACT
Clarifying the characteristics of soil microbial nutrient limitation and its driving mechanisms during vegetation restoration after farmland abandonment has important implications for revealing soil nutrient cycling and maintaining ecosystem stability. To determine the limitation of soil microbial nutrients and its relationship with soil properties along a chronosequence of abandoned farmland in the middle of the Qinling Mountains, the soil physicochemical properties and five enzyme activities (ß-1,4-glucosidase (BG), cellobiohydrolase (CBH), ß-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphatase (AP)) were measured, and models of extracellular enzymatic activity were applied. The results showed that the activities of BG, CBH, NAG, LAP, and AP were significantly increased following farmland abandonment. With the increasing years of abandonment, the ratios of (BG+CBH)/(NAG+LAP) and (BG+CBH)/AP significantly decreased, whereas the ratio of (NAG+LAP)/AP increased. Correlation analysis showed that most soil physicochemical properties were significantly correlated with extracellular enzyme activities and extracellular enzymatic stoichiometry. The vector length of extracellular enzymatic stoichiometry decreased with the increase in abandonment years, indicating that the limitation of soil microorganisms on carbon (C) was reduced. Moreover, the vector angles (>45°) showed a decreasing trend, indicating that microbial metabolisms were limited by phosphorus (P) and gradually decreased. Regression analysis showed that the C and P limitations were significantly related to total nutrients, available nutrients, nutrient ratio, and soil physical properties. Partial least squares path modeling (PLS-PM) revealed that the C and P limitations were directly regulated by nutrient ratio. PLS-PM further showed that soil total nutrients indirectly affected soil microbial C and P limitations by affecting nutrient ratio, and nutrient ratio affected the soil metabolism limitation via available nutrients and pH. Our study suggests that the characteristics of microbial metabolism during the vegetation restoration process reflect the mechanism of microorganism-mediated soil nutrient cycling, which provides a theoretical basis for revealing the community dynamics and stability during the vegetation restoration process and maintaining the regional ecological environment security in the Qinling Mountains.
Subject(s)
Ecosystem , Soil Microbiology , Carbon/analysis , China , Nitrogen/analysis , Phosphorus/analysis , SoilABSTRACT
Disturbance is the driving force of forest succession, which can change forest structure and surface vegetation. Disturbance also affects rodent-mediated seed dispersal. In this study, numbered plastic tags were used to examine the responses of rodent dispersal behavior to the fates of Quercus aliena var. acuteserrata acorns at three habitats formed by different artificial disturbances in pine-oak mixed forests in the Qinling Mountains, i.e., unlogged stand, stand in the third year after tending thinning, and bare land. The results showed that seed removal rate from stands in the third year after tending was significantly higher than that in the other two habitats. The proportion of predation in bare land was significantly lower than that in the unlogged stand (25.0%) and in the stand in the third year after tending thinning (36.3%). In the third year after tending thinning, the seed predation rate after seed moving was significantly higher than those in the unlogged stand (17.3%) and bare land (5.0%). Moreover, the proportion of scatter hoarding after removal was also highest in the stand in the third year after tending thinning (4.3%). The longest average dispersal distance (26 m) occurred in the stand in the third year after tending thinning, which was significantly longer than those at the other two habitats. Therefore, the different habitat types significantly influenced the initial seed dispersal process by rodents, with consequences on the rates of seedling establishment. Habitat types affected the foraging strategies of rodents, thereby leading to different seed dispersal modes and natural regeneration patterns in the forest.