Disentangling the effects of legacies from those of current land use on soil properties in Los Tuxtlas Biosphere Reserve, Mexico

Abstract

Soil properties are the product of current land use as well as legacies of historic use. Disentangling these effects is particularly challenging in tropical landscapes where plot-level land use history consists of varied sequences of uses punctuated by periods of abandonment. Here, we studied the soils of 63 plots in three sites of the Los Tuxtlas Biosphere Reserve, Mexico, and used detailed landowner accounts of land use history to model the effects of land use and its legacies. Electrical conductivity, N-NO3− and ant species richness were higher in current land uses featuring developed canopies (forests, secondary growth and palm and coffee plantations) compared to intensive land uses (livestock pastures and maize-slash and burn). Land uses aimed at soil restoration (maize-mucuna and tree plantations on degraded soils) improved soil bulk density only with respect to intensive land uses. The most frequent effects of historical land use variables (time since forest felling and cumulative times under each land use type) on soil properties occurred in interaction with each other and independently of the current land use. Beta glucosidase activity, pH and nematode richness were explained exclusively by historical use. In general, the duration of use dictated soil deterioration; however, the accumulation of time under intensive land uses had stronger legacies, in terms of soil physical and chemical properties, compared to that under agroforestry (coffee and palm cultivation). The richness of four taxa was sensitive to the land use history variables. Surprisingly, Nematoda and plant symbionts (nitrogen fixing bacteria and arbuscular mycorrhizal fungi) richness, but not that of Coleoptera, increased with accumulated time (20–40 yr) under maize cultivation. We suggest that the long history of traditional maize cultivation in polycultures has permitted the development of a rich soil biota.