Abstract

Semi-arid forests of the Aravalli hills are rich in tree diversity, but plant invasions during the last several decades, especially by Prosopis juliflora (Sw.) DC. have affected the vegetation structure and biogeochemical cycles of these forests. We compared carbon (C), and nitrogen (N) concentrations in the fine root, leaf, and soil physicochemical properties under the invasive tree species, P. juliflora, and native, Acacia nilotica (L.) Willd. ex Delile, to evaluate the effect of invasive tree species on total soil C, N concentrations, and C:N ratios. We also analyzed the soil samples for soil organic C (SOC), total N (TN), soil microbial biomass C (MBC), and soil microbial biomass N (MBN) and stocks. Soil physical and chemical properties under the invasive P. juliflora and native A. nilotica trees varied significantly (p < 0.05). The C and N concentrations in the fine root, leaf, soil SOC, TN and MBC, and MBN concentrations were significantly (p < 0.05) higher in P. juliflora than A. nilotica while C:N ratio, and bulk density, exhibited the opposite trends. The C concentrations followed the order fine root > leaf > soil > microbial biomass while for N concentration and C:N ratios, it was leaf > fine root > soil > microbial biomass. The invasive P. juliflora had a lower C:N ratio in leaf, fine root, and soil than the native A. nilotica. The average rhizosphere soil, fine root, and leaf C concentration for P. juliflora were 36.72 ± 0.84 g kg⁻¹, 547.84 ± 18.56 g kg⁻¹, and 534.77 ± 5.12 g kg⁻¹, respectively and were 1.42, 1.16 and 1.04 times higher than for A. nilotica. Similarly, P. juliflora average rhizosphere soil, fine root, and leaf N concentrations were 4.37 ± 0.11 g kg⁻¹, 19.96 ± 0.94 g kg⁻¹, and 23.18 ± 0.84 g kg⁻¹, respectively, and 2.0, 1.27, and 1.85 times, respectively, higher than for A. nilotica. Further, the MBC:SOC or MBN:TN ratios were higher in native A. nilotica, likely indicating higher efficiency of microbes in soil C decomposition. Together, our results indicate that invasive P. juliflora altered the ecosystem processes and increased the soil and microbial C, and N stocks compared to native A. nilotica in the semi-arid forests of the Aravalli hills.

摘要

阿拉瓦利山的半干旱森林拥有丰富的树木多样性，但在过去几十年中植物入侵，特别是Prosopis juliflora (Sw.) DC。影响了这些森林的植被结构和生物地球化学循环。我们比较了入侵树种P. juliflora和本地树种Acacia nilotica 的细根、叶子和土壤理化性质中的碳 (C) 和氮 (N) 浓度(L.)威尔德。ex Delile，评估入侵树种对土壤总碳、氮浓度和碳氮比的影响。我们还分析了土壤样品的土壤有机碳 (SOC)、总氮 (TN)、土壤微生物生物量碳 (MBC) 以及土壤微生物生物量氮 (MBN) 和储量。入侵的黑杨和本地尼罗罗树下的土壤理化性质差异显着（p  < 0.05）。细根、叶片、土壤 SOC、TN 和 MBC 中的 C 和 N 浓度以及 MBN 浓度，黑杨显着高于尼罗罗非鱼( p  < 0.05)而C:N比和堆积密度则表现出相反的趋势。C浓度的顺序为细根>叶片>土壤>微生物量，而N浓度和C:N比的顺序为叶片>细根>土壤>微生物量。入侵的P. juliflora在叶子、细根和土壤中的 C:N 比低于本地A. nilotica。黑杨的平均根际土壤、细根和叶片碳浓度分别为36.72±0.84 g kg ^-1、547.84±18.56 g kg ^-1和534.77±5.12 g kg ^-1，分别比尼罗罗高1.42、1.16和1.04倍。同样，P. juliflora根际土壤、细根和叶片的平均氮浓度分别为 4.37 ± 0.11 g kg ^-1、19.96 ± 0.94 g kg ^-1和 23.18 ± 0.84 g kg ^{-1 ，分别}比尼罗罗非鱼高 2.0、1.27 和 1.85 倍。此外，本地尼罗罗非鱼的 MBC:SOC 或 MBN:TN 比率较高，这可能表明微生物在土壤碳分解中的效率较高。总之，我们的结果表明，与阿拉瓦利山半干旱森林中的本地尼罗罗非鱼相比，入侵的朱丽花改变了生态系统过程，增加了土壤和微生物碳和氮的储量。