DOI: 10.5061/dryad.5dv41ns5z
title: Foliar fungal pathogens along an elevation gradient in Tibetan alpine meadow

description: Foliar fungal diseases have a great influence on both photosynthesis and
 ecosystem function. However, information on how the elevation
 gradient (which is one of the most important biogeographic
 factors) affects foliar fungal diseases is scarce. Here, we did
 an investigation along 3200 m ~ 4000 m in an alpine meadow and arranged 30
 quadrats collecting data of foliar fungal diseases, plant
 composition and soil properties to study the plant community-mediated
 (through changes in plant biomass, diversity, phylogenetic structure and
 community composition) and soil-mediated (through changes in soil
 properties) effects of elevation on community-level foliar fungal
 diseases. Based on linear models, we found that elevation did not
 significantly affect most of the individual plant species disease severity
 and community pathogen load. Meanwhile, a combination of community
 proneness and Pielou’s evenness index was the best model in predicting
 pathogen load. The structural equation model further confirmed that
 although elevation significantly changed both the plant community indices
 and soil properties, elevation mainly drove pathogen load via plant
 community-mediated effects, rather than soil-mediated effects. Hence, we
 provided new empirical evidence of the plant community-mediated effects on
 plant diseases by changing the composition and the evenness of plant
 community along elevation. Our study will improve the predictability of
 plant diseases, especially under the background of global climate change.
description: Our experiment was conducted along
 an elevation gradient ranging from 3200 m a.s.l. (
 37°36'39'' N, 101°18'16'' E) to
 4000 m a.s.l. (37°42'29'' N, 101°22'27'' E)
 on the south slope of Qilian Mountains in Menyuan County, located in the
 northeastern Qinghai-Tibetan Plateau. We established thirty 0.5 × 0.5 m
 plots along the elevation gradient. Specifically, we established 6 plots
 (replicants) on flat ground at each of five elevations: 3200 m a.s.l.
 (37°36'39'' N, 101°18'16'' E), 3400 m a.s.l.
 (37°39'58'' N, 101°20'20'' E), 3600 m a.s.l.
 (37°41'47'' N, 101°21'34'' E), 3800 m a.s.l.
 (37°42'13'' N, 101°22'14'' E) and 4000 m
 a.s.l. (37°42'29'' N, 101°22'27'' E). The
 plots were randomly selected with at least 10 m buffer zone between two
 adjacent plots at each elevation. In early
 August 2020, we harvested all the plant aboveground parts at ground level
 and sorted them into plant species for each plot. Then we dried them at
 65℃ for 48 hours to constant mass and weighed to 0.01 g as the species
 aboveground biomass. We also collected four soil cores (5 cm in diameter
 and 10 cm in depth) from each plot and pooled them as one sample. Soil
 moisture content (W; %) was measured gravimetrically after 5 h of
 desiccation at 120℃. A pH analyzer and a conductivity analyzer were used
 to measure the soil pH (pH) and soil conductivity (C; ms/s), respectively.
 5 grams of fresh soil were extracted with 50 ml 0.2 M KCl for 1 h at 60
 rev s<sup>-1</sup> using a shaker, then nitrate-nitrogen
 (NO<sub>3</sub><sup>-</sup>;<i>
 </i>mg/kg) and ammonium-nitrogen
 (NH<sub>4</sub><sup>+</sup>;<i>
 </i>mg/kg) were measured using an auto-analyzer (AA3, Bran-Luebbe,
 Germany). We recorded disease severity
 (i.e<i>.</i> % leaf area covered by fungal lesion;
 <i>V<sub>i</sub></i>) from five leaves randomly
 selected from five individuals for each plant species in each plot. And we
 recorded all available leaves for species with less than 25 leaves.
 Pathogen identification mainly followed identification manuals including
 Fungal Identification Manual.