Responses of soil microbial communities and enzyme activities to nitrogen and phosphorus additions in Chinese fir plantations of subtropical China

W Y Dong,X Y Liu,X L Fu,H M Wang,X F Wen,X Y Zhang,X M Sun,F S Chen

doi:10.5194/bg-12-5537-2015

Abstract

Abstract. Nitrogen (N) and phosphorus (P) additions to forest ecosystems are known to influence various above-ground properties, such as plant productivity and composition, and below-ground properties, such as soil nutrient cycling. However, our understanding of how soil microbial communities and their functions respond to nutrient additions in subtropical plantations is still not complete. In this study, we added N and P to Chinese fir plantations in subtropical China to examine how nutrient additions influenced soil microbial community composition and enzyme activities. The results showed that most soil microbial properties were responsive to N and/or P additions, but responses often varied depending on the nutrient added and the quantity added. For instance, there were more than 30 % greater increases in the activities of β-glucosidase (βG) and N-acetyl-β-D-glucosaminidase (NAG) in the treatments that received nutrient additions compared to the control plot, whereas acid phosphatase (aP) activity was always higher (57 and 71 %, respectively) in the P treatment. N and P additions greatly enhanced the phospholipid fatty acids (PLFAs) abundance especially in the N2P (100 kg ha−1 yr−1 of N +50 kg ha−1 yr−1 of P) treatment; the bacterial PLFAs (bacPLFAs), fungal PLFAs (funPLFAs) and actinomycic PLFAs (actPLFAs) were about 2.5, 3 and 4 times higher, respectively, than in the CK (control). Soil enzyme activities were noticeably higher in November than in July, mainly due to seasonal differences in soil moisture content (SMC). βG or NAG activities were significantly and positively correlated with microbial PLFAs. These findings indicate that βG and NAG would be useful tools for assessing the biogeochemical transformation and metabolic activity of soil microbes. We recommend combined additions of N and P fertilizer to promote soil fertility and microbial activity in this kind of plantation.

Highlights

Nutrient availability, one of the most important factors controlling tree growth in forest plantations, can be significantly modified by fertilizer applications (Tumer and Lambert, 2008)
Further comparison with the CK treatment shows that N and P fertilizer applications resulted in improvements in soil organic carbon (SOC), total N and total P contents compared with the CK (P < 0.05)
We found that soil moisture content (SMC) was significantly and positively correlated with bacterial phospholipid fatty acids (PLFAs) signatures, and the abundance of soil bacteria biomass was higher in November compared to July

Summary

Introduction

One of the most important factors controlling tree growth in forest plantations, can be significantly modified by fertilizer applications (Tumer and Lambert, 2008). Nitrogen (N) is generally believed to be the key growth-limiting element that controls the species composition, diversity, and productivity of forest ecosystems (Weand et al, 2010). N inputs into forest ecosystems from atmospheric deposition have increased at both regional and global scales, especially in Asia (Lu et al, 2009; Zechmeister-Boltenstern et al, 2011). Dong et al.: Responses of soil microbial communities and enzyme activities be at threat from imbalanced nutrition inputs (Vesterdal and Raulund-Rasmussen, 2002; Weand et al, 2010)

Methods

Results

Discussion

Conclusion