【歡迎您關注--農業環境科學】
中國科學院西雙版納熱帶植物園生態水文研究組博士後Singh Ashutosh Kumar團隊測定了乾旱熱帶環境下土壤微生物指數隨土地利用變化（自然林、輪歇地、農田）、季節更替、土壤資源（C、N、P）可利用性的響應特徵。相關成果發表於Ecological Indicators（IF=4.49）。
閱讀論文全文請點擊文末閱讀原文。
Highlights
Forest conversion to fallow and agriculture altered soil biological responses.
Response of oxidative enzymes and specific enzyme activities were distinct from other variables.
Seasonal differences in biological responses were consistent irrespective of LUC.
Soil resources (C, N and P) were coupled with the majority of biological responses.
Oxidative enzymes showed weaker coupling with these soil resources.
Abstract
Land use change (LUC) in tropics, explicitly from forest to conventional agriculture, is negatively affecting soil health and productivity. However, effect of such LUC on soil biological properties are poorly known in dry tropical environment. This study aimed to determine the impact of such LUC and climate seasonality on soil biological properties (microbial and enzyme activities), and to also explore the role of soil resources (C, N and P) in driving soil biological properties during this environmental change. Soil biological indicators of topsoil (0–15 cm) were measured on a seasonal basis in the natural forest, fallow and agricultural land. Soil microbial biomass C (Cmic), CO2 efflux (Cefflux) and hydrolytic enzyme activities (acid phosphatase, alkaline phosphatase, β-glucosidase, dehydrogenase, fluorescein diacetate) were generally higher in the forest followed agriculture and fallow. The lower level of these biological variables in agriculture soils were possibly due to lower total soil organic carbon (SOC), labile SOC (particulate OC; POC), total N and P, and cropping disturbance (i.e., fertilization) induced higher inorganic N and P. Whereas, lower biological activities in fallow soils were mainly attributed lower plant activity (i.e. litter production and root activity). In contrast, oxidative enzyme (particularly peroxidase) activities were higher in agriculture followed by the forest and fallow, which might be attributed to higher soil oxygenation from tillage in agriculture and higher persistent SOC (non-particulate OC; NPOC). Seasonal variation in soil biological properties was identical among land uses, though its extent was greater in the forest than fallow and agriculture, indicating LUC can alter the degree of seasonality in biological properties. In addition, the higher specific enzyme activities (i.e., enzyme activities per unit of Cmic) and microbial metabolic quotient (qCO2) in the fallow followed by agriculture and forest, indicating the higher degree of stress on soil microbes after the deforestation than cropping. Whereas, the higher specific enzyme activities and qCO2 in agriculture possibly attributed to higher microbial nutrients demand and lower SOC accumulation. Collectively, our results reveal the significant effects of deforestation and agriculture on soil biological activities and improve our understanding of the potential mechanism driving these effects.
土壤是陸地生態系統的重要組成部分，它直接貢獻了諸多生態服務功能，包括淨初級生產力、氣候和水分調節、養分循環與碳封存等，這種服務功能從根本上取決於地上植物群落、地下土壤微生物的多功能性發揮程度。因此，對地下土壤微生物過程的深入認知，將有助於制定合理有效的土地利用和管理措施、充分發揮生態系統的服務功能。然而，對乾旱熱帶環境下土地利用變化導致的土壤生物響應尚不明確。
為此，中國科學院西雙版納熱帶植物園生態水文研究組博士後Singh Ashutosh Kumar測定了乾旱熱帶環境下土壤微生物指數隨土地利用變化（自然林、輪歇地、農田）、季節更替、土壤資源（C、N、P）可利用性的響應特徵。研究結果表明：土壤微生物生物量碳、二氧化碳釋放量（Cefflux）、水解酶活性（磷酸酶、β-葡萄糖苷酶、脫氫酶、螢光素二乙酸酯）對土地利用變化的反應非常敏感，敏感順序是自然林> 農田> 輪歇地，這與農田較低的有機碳（SOC、OC、POC）、總氮和磷及耕作施肥引起的高無機氮和磷有關，而輪歇地較低的土壤微生物活動則與其較低的枯落物量和根系有關。氧化酶活性（酚氧化酶、過氧化物酶）則是農田>自然林>輪歇地，這與農田耕作導致的土壤高氧化、高持續有機碳（NPOC）有關。季節變化對不同土地利用類型土壤微生物指數的影響大致相似，其中以自然林的變化最大，表明土壤微生物對多年生植物響應的重要性。在不同土地利用類型中，輪歇地的單位土壤微生物指數和微生物代謝率（qCO2）最高。以上結果表明，森林砍伐后土壤微生物受到的脅迫壓力最大，而農業活動對土壤微生物活性的影響最顯著。