Effects of the type of forest alteration on gross nitrogen mineralization in soils of southern India

• 作者: Niharika Sharma Sanjeev Kumar
• 来源期刊: 林业研究（英文版）
• 年，卷（期）: 2021,（4）
• 所属期刊栏目: ORIGINAL PAPERS
• 页码范围: 1689-1697
• 页数: 9页
• 语种: 英文

摘要

Change in land-use practices can result in major shifts in the cycling of various elements, particularly nitro-gen (N), which is prone to anthropogenic perturbations. For quantifying these shifts, accurate measurements of rates of biogeochemical transformations of N are needed. We used the ( 15 N) isotope dilution technique to understand the effects of the types of forest alteration on (N) trans-formation rates by comparing gross N mineralization and ammonium (NH 4 + ) consumption rates in soils of a man-aged forest, an unmanaged forest, and a rubber plantation in Kerala, India. Overall, nitrate (NO 3 ? ) dominated soils of the managed and unmanaged forests, whereas soils in the rubber plantation showed relatively higher NH 4 + concen-tration. Total N (TN) and total organic carbon (TOC) con-centrations were the highest under the rubber canopy (TN: 1.49 ± 0.02 mg N g ?1 ; TOC: 7.96 ± 0.86 mg C g ?1 ). In soils of all three forest types, gross N mineralization rates were higher compared to NH 4 + consumption rates. Despite high TN and TOC concentrations, the rates of gross N mineraliza-tion and NH 4 + consumption were considerably lower in the rubber plantation (mineralization: 1.08 ± 0.08 mg N kg ?1 d ?1 ; consumption: 0.85 ± 0.09 mg N kg ?1 d ? ) compared to the managed (mineralization: 3.71 ± 0.35 mg N kg ?1 d ?1 ; consumption: 2.20 ± 1.41 mg N kg ?1 d ?1 ) and unmanaged (mineralization: 2.20 ± 1.07 mg N kg ?1 d ?1 ; consumption: 1.39 ± 0.27 mg N kg ?1 d ?1 ) forests. The lower NH 4 + con-sumption rates in the rubber plantation led to significantly higher ( p < 0.05) residence time of NH 4 + (～ 4 days) com-pared to the managed and unmanaged forests (< 2 days), pos-sibly contributing to acidification of rubber soils (pH ～ 4.8). These results together suggest that replacement of naturally grown forests with a mono-cropped plantation such as rub-ber negatively impact rates of N transformation processes in tropical soils and imply that change in tree species com-position of naturally grown forests can adversely affect soil microbial activity. We recommend intercropping these plan-tations with commercial crops to maintain soil microbial diversity and biogeochemical cycling for sustainable forest management.