Effects of altitude, land use and microsites on early-life performance of a high mountain tree: insights from an insitu sowing experiment.

LACHMUTH, SUSANE; RENISON, DANIEL; CÁCERES YOLANDA; AUGE, HARALD; HENSEN, ISABEL; SCHRIEBER, KARIN; ARGIBAY, DAIHANA SOLEDAD

DIVERSITY AND DISTRIBUTIONS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 25 p. 1537 - 1550

1366-9516

Aim. Understanding the forces that drive range shifts in forest landscapes is imperative for 9 predicting species distributions under anthropogenic climate and land use change. However,empirical studies exploring how these components jointly influence critical early-life stagesof mountain tree species across environmental gradients are scarce. We used the high12 mountain tree Polylepis australis as model species to investigate the relative importance ofaltitude and associated climatic conditions, land use for livestock and micrositecharacteristics on early-life performance.Location. Córdoba Sierras, central Argentina.Methods. We set up an extensive in situ sowing experiment with a robust split-plot designthat integrated spatial scales ranging from 0.4 mubplots at the microsite level (associatedwith vegetative and micro-topographic structures), to livestock exclosure and enclosureplots of several hectares, to an altitudinal gradient of 1000 m. Components of early-lifeperformance were monitored across two subsequent growing seasons.Results. Microsite characteristics played a fundamental role in P. australis establishment,whereby interactions with altitude and/or land use suggested alternate mechanisms:facilitation (likely reduced desiccation) dominated at low altitude while at high altitudeabiotic stress (likely intensive frost and radiation) overruled any microsite effects. At midaltitude benefits of competition release prevailed over facilitation and microsite effectsgained importance under livestock presence. Inconsistencies between pre- and post27 emergence responses illustrated potential tradeoffs between beneficial and detrimentaleffects of microsite conditions upon performance throughout early life: a favorable locationfor seeds may abruptly turn adverse for seedlings.Main conclusions. We unravel how changes in altitude, anthropogenic disturbances andmicrosite characteristics jointly modulate P. australis performance across stages of earlyestablishment. Such information is fundamental when categorizing specific microhabitats as?safe sites? for tree regeneration especially in mountain environments with highspatiotemporal heterogeneity