Nicholas B. Comerford

Soil ecosystem services are diverse, valuable, and underappreciated. They are classified as provisioning, regulating, supporting, and cultural services. This paper is the product of a Soil Science Society of America task force convened to define and value ecosystem services derived from soil for the benefit of scientists, elected officials, and practitioners with the hope that a better understanding of soil ecosystem services will result in informed decisions in the use of soils. Soil provides medicines, building materials, and nutrients. Soil controls nutrient and water cycles. Soil is capable of degrading wastes and detoxifying compounds. Soil is a habitat for diverse microorganisms and fauna, which in turn supports valuable ecosystem services. Soil also supports recreational activities and is part of our cultural heritage evident in legend, religion, song, and art. The value of soil's ecosystem services exceeds that of other parts of an ecosystem, yet the scope and value of soil‐derived ecosystem services remains poorly understood. Three of the greatest challenges that remain are to develop (i) a better understanding and documentation of soil biodiversity, (ii) more comprehensive economic valuation of soil services, and (iii) an understanding of how to manage soil to maximize its benefits to humankind.

Physical protection of C by aggregates and their response to forest management are important components of soil C management. This study was conducted to examine the morphology and strength of aggregates, to quantify C held by aggregates, and to study the effects of forest management intensity on aggregation. Surface horizon soil (0–5‐ and 5–10‐cm depths) was collected from a 4‐yr‐old loblolly pine ( Pinus taeda L.) plantation in North Florida under two contrasting management regimes (intensive vs. operational fertilization and chemical weed control, called high‐ and low‐intensity treatments, respectively). Samples were dry sieved into four size classes: 2000 to 250, 250 to 150, 150 to 53, and −1 for the least stable macroaggregates in the 2000‐ to 250‐μm fraction to 113 J mL ⁻¹ for the most stable microaggregates in the 150‐ to 53‐μm fraction. Aggregate organic matter (AOM) was an important C pool in these soils, accounting for nearly half of the total soil organic matter. The high‐intensity management treatment had lower AOM in the 2000‐ to 250‐μm fraction, probably due to lower biomass input of understory roots caused by chemical understory control. Modification of the sonication technique proved useful for studying different aspects of aggregation and gave indications of an aggregate hierarchy even in these extremely sandy soils.