DOI: 10.5061/dryad.5mkkwh71z
title: Data from: Removal of cattle accelerates tropical dry forests succession in Northwestern Mexico

description: Domestic livestock influence patterns of secondary succession across
 forest ecosystems. However, the effects of cattle on the regeneration of
 tropical dry forests (TDF) in Mexico are poorly understood, largely
 because it is difficult to locate forests that are not grazed by cattle or
 other livestock. We describe changes in forest composition and structure
 along a successional chronosequence of TDF stands with and without cattle
 (chronic grazing or exclusion from grazing for ~8 yr). Forest stands were
 grouped into five successional stages, ranging from recently abandoned to
 mature forest, for a total of 2.7 ha of sampled area. The absence of
 cattle increased woody plant (tree and shrub) density and species
 richness, particularly in mid-successional and mature forest stands.
 Species diversity and evenness were generally greater in sites where
 cattle were removed and cattle grazing in early successional stands
 reduced establishment and/or recruitment of new individuals and species.
 Removal of cattle from forest stands undergoing succession appears to
 facilitate a progressive and non-linear change of forest structure and
 compositional attributes associated with rapid recovery, while cattle
 browsing acts as a chronic disturbance factor that compromises the
 resilience and structural and functional integrity of the TDF in
 northwestern Mexico. These results are important for the conservation,
 management, and restoration of Neotropical dry forests.
description: We
 stratified observation sites across two types of land use: (1) privately
 owned, active ranches within APFF-SARC where cattle production has been
 ongoing for at least 50 years (chronic grazing), and (2) sites in the ReMM
 where cattle have been permanently excluded (grazing exclusion) since
 2008. In both the active ranches and the ReMM, we identified secondary
 forest stands across a successional gradient, representing different times
 since agricultural abandonment. We grouped forest stands into five
 successional stages: i) 2-5 years since abandonment (Recent), ii) 5-10
 years (Young), iii) 10-20 years (Intermediate), iv) 30-35 years (Late) and
 v) mature old-growth forest not  cleared for at least ~100 years (OGF).
 Combined with the two cattle management regimes (cattle grazing and
 grazing exclusion), we evaluated 10 combinations of management and
 successional stage. Information on stand age and cattle production was
 obtained through interviews with ranch owners and forest rangers. Each
 treatment combination had three replicates, except for Recent and Young
 forests excluded from cattle. The availability of sites recently excluded
 from cattle in the ReMM was limited (Table S1). We conducted
 vegetation sampling during the rainy season (July-October) of 2015 (~8
 years after the exclusion of cattle). In each of the 27 sampling stands,
 we established ten 50 x 2 m (0.1-ha) transects (Gentry, 1982), for a total
 of 2.7 ha sampled. All woody species (trees and shrubs) of height ≥ 1.30 m
 and diameter at breast height (dbh) ≥ 1 cm were recorded and
 identified. We calculated
 aboveground biomass and carbon storage for each stand using the general
 model developed by Chave et al. (2005) for tropical dry forests. This
 model converts biometric measurements of trees (dbh, height, wood density)
 into biomass values using empirical allometric equations (Chave et al.,
 2014). We obtained wood density estimates for the 38 most abundant species
 from Quisehuatl-Medina (2019) and García-Ramírez (2017). For the rest of
 the species, we obtained wood density values from the world wood density
 database (Chave et al., 2009) and Ordóñez et al.<i>
 </i>(2015). We imputed an average value (0.589 g
 cm<sup>3</sup>) for six species missing density data. We
 estimated carbon mass in the woody vegetation using a conversion factor of
 0.47 g C / g dry wood (Chave et al., 2005). <b>2.3 Physical and chemical
 soil variables</b> To identify the effects of cattle
 removal and successional state on soil nutrients, we collected five soil
 samples in each of the 27 plots between 0-10 cm depth. The five soil
 samples were combined to make a single homogeneous sample per plot. Half
 of each sample was dried and was used to measure i) total C by coulometric
 detection (Nelson & Sommers, 1996), ii) total N using the micro
 Kjeldahl method (Bremmer, 1996) and, and iii) P using the molybdate
 colorimetric method following ascorbic acid reduction (Murphy &
 Riley, 1962). The portion of the soil samples that remained were used to
 extract NH<sub>4</sub> and NO<sub>3</sub> by the
 phenol-hypochlorite method. Soil compaction was measured following
 protocols developed by Blake (1965) (For details see Appendix S1). 
 Samples were analyzed at the Soil Laboratory of the Instituto nacional de
 Investigaciones Forestales, Agricolas y Pecuarias (INIFAP,
 Mexico).