Center for Subtropical Agroforestry, School of Forest Resources and Conservation, University of Florida, Gainesville, FL 32611, USA.
J Environ Qual. 2011 May-Jun;40(3):784-90. doi: 10.2134/jeq2011.0076.
Investments in agroforestry research during the past three decades-albeit modest-have yielded significant gains in understanding the role of trees on farmlands, and the ecological and economic advantages of integrated farming systems. While early research focused mostly on farm or local levels, broader-level ecosystem services of agroforestry systems (AFS) have raised high expectations in recent years. The nine papers included in this special collection deal with three of such environmental benefits of AFS: water-quality enhancement, carbon sequestration, and soil improvement. These benefits are based on the perceived ability of (i) vegetative buffer strips (VBS) to reduce surface transport of agrochemical pollutants, (ii) large volumes of aboveground and belowground biomass of trees to store high amounts of C deeper in the soil profile, and (iii) trees to enhance soil productivity through biological nitrogen fixation, efficient nutrient cycling, and deep capture of nutrients. The papers included have, in general, substantiated these premises and provided new insights. For example, the riparian VBS are reported to increase the reservoir life, in addition to reducing transport of agrochemicals; the variations in C storage in different soil-fraction sizes suggest that microaggregate (250-53 μm) dynamics in the soil could be a good indicator of its C-storage potential; and the use of vector analysis technique is recommended in AFS to avoid consequences of inaccurate and overuse of fertilizers. The papers also identified significant knowledge gaps in these areas. A common theme across all three environmental quality issues covered is that more and varied research datasets across a broad spectrum of conditions need to be generated and integrated with powerful statistical tools to ensure wide applicability of the results. Furthermore, appropriate management practices that are acceptable to the targeted land users and agroforestry practitioners need to be designed to exploit these environmental benefits. The relative newness of research in environmental quality of AFS will pose some additional challenges as well. These include the lack of allometric equations for tree-biomass determination, absence of standardized norms on soil sampling depth, and limitations of fixed-effect models arising from issues such as pseudo-replication and repeated measures that are common in studies on preexisting field plots. Overall, this special collection is a timely effort in highlighting the promise of AFS in addressing some of the environmental quality issues, and the challenges in realizing that potential.
过去三十年的农业林业研究投资虽然规模不大，但在了解树木在农田中的作用以及综合农业系统的生态和经济优势方面取得了重大进展。虽然早期的研究主要集中在农场或地方层面，但近年来，农业林业系统（AFS）的更广泛的生态系统服务提高了人们的期望。本特刊收录的九篇论文涉及 AFS 的三种环境效益：水质改善、碳固存和土壤改良。这些效益基于（i）植被缓冲带（VBS）减少农业化学污染物地表运输的能力、（ii）树木地上和地下生物量大量储存土壤剖面深处的大量 C 以及（iii）树木通过生物固氮、有效养分循环和养分的深层吸收来提高土壤生产力的能力。总的来说，这些论文证实了这些前提，并提供了新的见解。例如，报告称河岸 VBS 除了减少农用化学品的运输外，还延长了水库的寿命；不同土壤分馏大小的碳储存变化表明，土壤微团聚体（250-53 μm）的动态可能是其碳储存潜力的良好指标；并且建议在 AFS 中使用向量分析技术，以避免因不准确和过度使用肥料而产生的后果。这些论文还确定了这些领域的重大知识差距。涵盖的所有三个环境质量问题的一个共同主题是，需要在广泛的条件下生成更多和更多样化的研究数据集，并与强大的统计工具相结合，以确保结果的广泛适用性。此外，需要设计可接受的目标土地使用者和农业林业从业者的适当管理实践，以利用这些环境效益。AFS 环境质量研究的相对新颖性也将带来一些额外的挑战。这些挑战包括缺乏树木生物量测定的异速方程、缺乏土壤采样深度的标准化规范以及由于伪重复和重复测量等问题导致固定效应模型的限制，这些问题在现有田间试验研究中很常见。总的来说，本特刊及时强调了 AFS 在解决一些环境质量问题方面的潜力，以及在实现这一潜力方面面临的挑战。
