Edge effects and human disturbance influence soil physical and chemical properties in Sacred Church Forests in Ethiopia

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Edge effects and human disturbance influence soil physical and chemical properties in Sacred Church Forests in Ethiopia Catherine L. Cardelús & Amare Bitew Mekonnen & Kelsey H. Jensen & Carrie L. Woods & Mabel C. Baez & Martha Montufar & Kathryn Bazany & Berhanu Abraha Tsegay & Peter R. Scull & William H. Peck

Received: 24 September 2019 / Accepted: 5 June 2020 # The Author(s) 2020

Abstract Aims Tropical forests are increasingly threatened by edge effects as forest degradation and deforestation continues, compromising soil integrity, seedling regeneration capacity, and ecosystem services. Ninety-three percent of the last remaining forests of northern Ethiopia, which number 1022 in the South Gondar region of our study, are 50 km), the degree of disturbance (13–86%) (Cardelús et al. 2019) and the presence of a protective wall surrounding the forest (Cardelús et al. 2017; Woods et al. 2017). The degree

Plant Soil

of disturbance was quantified by Cardelús et al. (2019) as the percent of various disturbances across the forests (e.g. weedy taxa, native and exotic tree plantations, clearings/gathering areas, buildings, graves). These sacred church forests present a unique opportunity to study the effects of extreme tropical forest fragmentation on soil health with respect to both fragment size and degree of disturbance. On average, in forests 60 m from church interior wall to forest edge had plots arranged in sequence from the center to the edge, while forests 60 m between the church wall and forest edge; b. < 60 m between church wall and forest edge; and c. arrangement of soil cores within a plot. Edgeexterior soil cores were collected at three compass directions

around each forests. Eucalyptus plantations, when present adjacent to the forest, were collected in triplicate as per edge-exterior soil plots

interior wall to forest edge had plots that were established at 3 cardinal directions around church within 10 m of the edge (Fig. 2). Three volumetric soil cores were collected 4.5 m apart within each plot to 10 cm in depth. All litter was removed down to the O horizon before sampling. Soil samples were collected once for each forest between 2014 and 2017.

All soils collected during the dry season (forest n = 30) were further analyzed for gravimetric water content (GWC), available P (μg-P • g-1 oven dry equivalent (ode) soil, (Murphy and Riley 1962; Lajtha et al. 1999) and available N (dissolved inorganic N (DIN) in the form of ammonium (μg-N–NH4+ g−1 ode soil) (Sims, 1995; Mulvaney, 1996)). We only analyzed soils collected in the dry season for GWC and available nutrients because we were not able to collect all soils in both seasons and prioritized the dry season. All colorimetric analyses were performed in the Cardelús lab at Colgate University on a BioTEK Powerwave (Winooski, VT).

Soil properties and nutrient analyses Across 40 forests (n = 9 samples/forest), 15 Eucalyptus plantations (3 samples/plantation) and 38 edge-exterior sites (3 samples/site), we collected 519 soil samples (Table 1). S