Temporal Variations in Soil Enzyme Activities and Responses to Land-Use Change in the Loess Plateau, China

Zhang Zhang,Han Han,Deng Deng,Zhao Zhao,Yang Yang,Ren Ren,Chong Chong

doi:10.3390/app9153129

Abstract

Variability in soil enzyme activity may have important implications for the knowledge of underground ecosystem functions driven by soil extracellular enzymes. To illustrate the temporal variation in soil enzyme activity after afforestation, we collected soil samples during different vegetative growth periods in three Caragana korshinskii Kom. stands of different ages (20, 30, and 40 years) and in a slope cropland in the Loess Plateau. These samples were used to analyze the catalase, sucrase, urease and alkaline phosphatase activities, the soil water content and the available soil nutrients (i.e., dissolved organic carbon, dissolved organic nitrogen, and available phosphorus). The results illustrated that the soil enzyme activities significantly increased following afforestation and varied with temporal variation. Overall, soil enzyme activities were higher in June and August, particularly, and both alkaline phosphatase and sucrase were more sensitive to temporal variation than the other two enzymes. In addition, redundancy analysis showed that soil enzyme activities were greatly correlated with soil nutrients, especially for dissolved organic carbon and dissolved organic nitrogen. Therefore, the results highlighted the importance of soil enzyme activities to soil nutrients under temporal variation following afforestation in the Loess Plateau, which may have practical significance for forest managers’ fertilization management of plantation in different seasons and different stand ages.

Highlights

Afforestation is an efficient measure to repair destroyed natural ecosystems, which occurs by converting cropland into perennial vegetation land, has great impacts on plant primary productivity and soil physicochemical properties [1,2,3] and in turn, influences soil biological activity, such as soil enzyme activity and microbial biomass [4,5]
Available soil nutrients (DOC, dissolved organic nitrogen (DON), and Available phosphorus (AP)) and Soil water content (SWC) differed with plant growing season and stand age (p < 0.01) (Figure 2, Table 2)
The dissolved organic carbon (DOC) and DON were highest in August, but the AP and SWC were highest in June and April, respectively

Summary

Introduction

Afforestation is an efficient measure to repair destroyed natural ecosystems, which occurs by converting cropland into perennial vegetation land, has great impacts on plant primary productivity and soil physicochemical properties (i.e., soil bulk density, aggregation, soil nutrient pools, and biodiversity) [1,2,3] and in turn, influences soil biological activity, such as soil enzyme activity and microbial biomass [4,5]. Soil enzyme activities in changing land-use types have attracted special attention for this topic’s relevance in soil ecosystem dynamics and ecosystem sustainability [6,7]. Due to diverse ecological communities, environmental factors and regional variation, knowledge of soil enzymatic metabolism, such as the temporal variation in soil enzymes after afforestation, is still ambiguous [8,9]. This poses a challenge to our understanding of underground ecosystem functions that are driven by soil extracellular enzymes.

Methods

Results

Discussion

Conclusion