Agricultural Legacies in Forest Environments: Tree Communities, Soil Properties, and Light Availability

Abstract

Temperate deciduous forests across much of Europe and eastern North America reflect legacies of past land use, particularly in the diversity and composition of plant communities. Intense disturbances, such as clearing forests for agriculture, may cause persistent environmental changes that continue to shape vegetation patterns as landscapes recover. We assessed the long-term consequences of agriculture for environmental conditions in central New York forests, including tree community structure and composition, soil physical and chemical properties, and light availability. To isolate the effects of agriculture, we compared 20 adjacent pairs of forests that were never cleared for agriculture (primary forests) and forests that established 85-100 years ago on plowed fields (secondary forests). Tree communities in primary and secondary forests had similar stem density, though secondary forests had 14% greater basal area. Species composition differed dramatically between the two forest types, with primary forests dominated by Acer saccharum and Fagus grandifolia and secondary forests by Acer rubrum and Pinus strobus. Primary and secondary forests showed no consistent differences in soil physical properties or in the principal gradient of soil fertility associated with soil pH. Within stands, however, soil water content and pH were more variable in primary forests. Secondary forest soils had 15% less organic matter, 16% less total carbon, and 29% less extractable phosphorus in the top 10 cm than adjacent primary stands, though the ranges of the forest types mostly overlapped. Understory light availability in primary and secondary forests was similar. These results suggest that, within 100 years, post-agricultural stands have recovered conditions comparable to less disturbed forests in many attributes, including tree size and number, soil physical properties, soil chemical properties associated with pH, and understory light availability. The principal legacies of agriculture that remain in these forests are the reduced levels of soil organic matter, carbon, and phosphorus; the spatial homogenization of soil properties; and the altered species composition of the vegetation.

Historical land use and stand age effects on forest soil properties in the Mid-Atlantic US

“…Forests were cleared for agricultural use, and after abandonment, succession led to the establishment of secondary forests. Consistent with results from this study, others have demonstrated that during succession from abandonment of agricultural fields to forests, carbon increases (Brunet et al, 2012;DeGryze et al, 2004;Falkengren-Grerup et al, 2006;Flinn and Marks, 2007), pH decreases (Falkengren-Grerup et al, 2006;Schrijver et al, 2012) and the C:N ratio increases (Compton and Boone, 2000). The young soils at the SERC stands were less acidic and contained less Al compared to the old forest soils in both the surface and lower depths.…”

Testing heterogeneity–diversity relationships in tropical forest restoration

“…Intensive anthropogenic disturbances, such as agriculture, often strongly reduce resource heterogeneity and b-diversity of plants and animals (Robertson et al 1993;Flinn and Marks 2007;Karp et al 2012). In turn, studies documenting natural forest recovery show that heterogeneity of habitat structure and species distributions increase over time (Denslow and Guzman 2000;Guariguata and Ostertag 2001;Cook et al 2005), but still are often lower in older secondary forests than in primary forests (Nicotra et al 1999;Flinn and Marks 2007). Restoration efforts across a range of systems have often failed to restore heterogeneity of abiotic conditions and community composition approaching that of more intact systems (Holl 2002b;Polley et al 2005).…”

Plasticity in response to phosphorus and light availability in four forest herbs

“…There is ample evidence of persistent (a)biotic differences between post-agricultural stands and forest stands for which there is no historical record of alternative land use ('ancient forest'). The abiotic legacies of former land use are expressed in soil nutrient availability (e.g., Koerner et al 1997;Verheyen et al 1999;Falkengren-Grerup et al 2006) and spatial heterogeneity of soil properties (Fraterrigo et al 2005;Flinn and Marks 2007). Among other nutrients, phosphorus (P) has specifically drawn the attention.…”