Soil Properties in CRUI Land Use Project at Harvard Forest 1995-1998

Soil properties and processes were evaluated on three types of colonial agricultural land-use - plowing, pasturing, and selective tree removal in a woodlot that ceased in the mid to late 1800s. Plowing, the most intensive type of agricultural disturbance, mixes soil to a depth of approximately 15cm, homogenizing the soil resources and likely reducing diversity in microenvironments. Removing trees and replacing them with grasses for pasture decreases the organic matter amount and types of inputs to the system, decreasing resource diversity. Woodlots, altered by selective and chronic tree removal, would have more limited decreases in resources and microenvironments. This study defines forest soil legacies using data from plots located at Harvard Forest in both amounts of soil resources and spatial heterogeneity of those soil resources. We found that for several soil parameters measured on previously cultivated and preciously pastured lands at the Harvard Forest, a legacy exists in the mineral soil, but the forest floor appears to have largely recovered from the agricultural disturbance. Parameters examined included soil mass, bulk density, organic matter content, pH, C, N, nitrogen mineralization and nitrification, Ca, Mg, K, and P.

本研究针对19世纪中后期停止利用的三类殖民时期农业土地利用方式——翻耕、放牧以及林分择伐——评估了土壤属性与土壤过程。翻耕作为强度最高的农业干扰方式，会将土壤翻搅至约15厘米深度，使土壤资源均质化，并可能降低微环境多样性。将树木移除并替换为牧草以发展放牧业，会减少输入至系统的有机质数量与种类，进而降低资源多样性。而经择伐与长期树木移除干扰的林分，其资源与微环境的退化程度则相对有限。本研究依托哈佛大学森林实验站（Harvard Forest）的样地数据，从土壤资源总量与土壤资源空间异质性两个维度定义了森林土壤遗留效应。研究发现，在该实验站此前经耕作与放牧的地块的矿质土壤中，仍存在农业活动遗留效应，但森林枯落物层似乎已基本摆脱农业干扰的影响。本研究测定的土壤参数包括：土壤质量、容重、有机质含量、pH值、碳（C）、氮（N）、氮矿化与硝化作用、钙（Ca）、镁（Mg）、钾（K）以及磷（P）。