DOI: 10.5683/sp3/kbype7
title: Emerging stability of forest productivity by mixing two species buffers temperature destabilizing effect

description: &lt;b&gt;Abstract&lt;/b&gt;&lt;br/&gt;&lt;p&gt;&lt;span lang="EN-US"&gt;The increasing disturbances in monocultures around the world &lt;/span&gt;&lt;span lang="EN-US"&gt;are&lt;/span&gt;&lt;span lang="EN-US"&gt; testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increase with species richness, although the ecological fundaments have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which this it is influenced by climate conditions across large geographical areas. &lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span lang="EN-US"&gt;Here, we &lt;/span&gt;&lt;span lang="EN-GB"&gt;used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. &lt;/span&gt;&lt;span lang="EN-US"&gt;Structural equation modelling was employed to further explore the direct and&lt;/span&gt; &lt;span lang="EN-US"&gt;indirect influence of&lt;/span&gt;&lt;span lang="EN-US"&gt; climate&lt;/span&gt;&lt;span lang="EN-US"&gt;, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. &lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span lang="EN-US"&gt;We showed that by adding only one tree species to monocultures&lt;/span&gt;&lt;span lang="EN-US"&gt;,&lt;/span&gt;&lt;span lang="EN-US"&gt; the level (overyielding: +6%) &lt;/span&gt;&lt;span lang="EN-US"&gt;and &lt;/span&gt;&lt;span lang="EN-US"&gt;stability (temporal stability: +12%) of stand growth increased significantly. We &lt;/span&gt;&lt;span lang="EN-US"&gt;identified &lt;/span&gt;&lt;span lang="EN-US"&gt;the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further &lt;/span&gt;&lt;span lang="EN-US"&gt;confirmed&lt;/span&gt;&lt;span lang="EN-US"&gt; asynchrony as &lt;/span&gt;&lt;span lang="EN-US"&gt;the &lt;/span&gt;&lt;span lang="EN-US"&gt;main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. &lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span lang="EN-GB"&gt;Synthesis and applications&lt;/span&gt;&lt;span lang="EN-US"&gt;.&lt;/span&gt; &lt;span lang="EN-GB"&gt;This study highlights the emergent properties associated with mixing two-species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance this impact. &lt;/span&gt;&lt;span lang="EN-US"&gt;The overyielding and temporal stability of growth addressed in this paper are essential for ecosystem services closely linked with the level and rhythm of forest growth. &lt;/span&gt;&lt;span lang="EN-US"&gt;Our results underline that mixing two species can be a realistic and effective nature-based climate solution, which could contribute towards meeting EU climate target policies. &lt;/span&gt;&lt;/p&gt;
description: &lt;b&gt;Methods&lt;/b&gt;&lt;br /&gt;&lt;p&gt;&lt;span lang="EN-US"&gt;The research unit is the forest stand. We used data from a total of 261 forest stands belonging to three triplet-transects across Europe. Each triplet consists of a plot established in a two species mixed stands, and two plots on the respective monospecific stands; the three stands are located close to each other under similar environmental conditions. The species composition of the mixtures changes in the three triplet-transects. The first transect covers monospecific and mixed stands of &lt;em&gt;Fagus sylvatica&lt;/em&gt; and Pinus sylvestris (32 sites, 96 stands), the second of &lt;em&gt;Quercus petraea&lt;/em&gt; and &lt;em&gt;Pinus sylvestris&lt;/em&gt; (35 sites, 105 stands), and the third of &lt;em&gt;Picea abies&lt;/em&gt; and &lt;em&gt;Pinus sylvestris&lt;/em&gt; (20 sites, 60 stands). Plot sizes varies from 0-02 to 0.15 ha depending on stand density a local site characteristics&lt;/span&gt;.&lt;/p&gt;
&lt;p&gt;&lt;span lang="EN-US"&gt;In each plot the diameter of all trees was measured, and two increment cores per tree were taken at a 1.3 m stem height in a sample of approximately 20 trees per species and plot. Annual ring widths were measured and cross-dated using standardized dendrochronological techniques. The studied period was 2000-2013 for the beech-pine transect and 2004-2017 for the oak-pine and spruce-pine transects (except in five triplets where the period was 2000-2013), the last year corresponding to triplet establishment. Using data from cored trees, tree diameter increment-diameter models were fitted by year, species and plot to estimate diameter increments of noncored trees for the studied period. Dead trees during the last 14 years were estimated using stumps, standing and lying dead trees, and their decomposition status. Based on measured tree diameters and annual diameter increments we estimated species and stand annual basal area (BA) and basal area growth (BAI), which conforms the dataset. &lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span lang="EN-US"&gt;Annual climate data were obtained from meteorological weather stations located in the proximity of each triplet (50 triplets). When local station data were not available, national digital climatic atlas data (24 triplets) or more general gridded data (13 triplets) were used (mostly CRU gridded database). For each triplet mean and standard deviation of annual precipitation (P) and mean annual temperature (T) for the studied period were calculated. &lt;/span&gt;&lt;/p&gt;
description: &lt;b&gt;Usage notes&lt;/b&gt;&lt;br /&gt;&lt;p&gt;The are presented in an excel-table which can be open freely in different ways (open office, google docs, etc.) &lt;/p&gt;
description: <b>Dryad version number:</b> 3
<b>Version status:</b> submitted
<b>Dryad curation status:</b> Published
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