Species richness: a pivotal factor mediating the effects of land use intensification and climate on grassland multifunctionality

Temperate semi-natural grasslands harbour unique biodiversity, support livestock farming through forage production, and deliver many essential ecosystem services (ESs) to human society; they are highly multifunctional. However, temperate grassland ecosystems are also among the most threatened ecosystems on earth due to land use and climate change. Understanding how biodiversity, climate, and land use intensification impact grassland multifunctionality through complex direct and indirect pathways is critical to better anticipate the future of these fragile ecosystems. 

Here, we evaluate how local plant species richness (SR) modulates the effect of land use intensification and climate on grassland multifunctionality (using six key ESs: biomass productivity and stability, forage quality, carbon storage, pollination, and local plant rarity) in the French Massif Central, the largest grassland in Western-Europe. We sampled 100 grassland fields with contrasted fertilisation rates, and SR over large elevational and latitudinal gradients related to variation in mean annual temperature (MAT), and drought severity (DS), two key climate change drivers that are predicted to increase in the future.

Using a confirmatory path analysis, we found that SR was the main driver of multifunctionality. We also found significant SR × MAT and SR × fertilization interactions suggesting that warm climate and high fertilization rates may alter the biodiversity-ecosystem multifunctionality relationships. Furthermore, increasing temperature and fertilization indirectly influenced multifunctionality by decreasing SR and consequent multifunctionality in warm low-land and highly fertilized grasslands compared to colder montane grasslands or less fertilised ones. DS only impacted some ES individually (e.g. forage quality).

Synthesis and applications: we identified SR as a pivotal factor mediating the effects of land use intensification and climate on multifunctionality through both direct and indirect pathways. Failing to account for changes in SR could thus bias any prediction of – or aggravate – the effects of land use intensification and climate change on ESs delivery in temperate grassland ecosystems. Considering that SR, MAT, and fertilization are major proxies of three main global change drivers (biodiversity loss, climate change, and land use intensification) our study may help to better anticipate the effect of multiple interacting global change drivers on grassland ecosystems.

Methods
This dataset of 100 grasslands in Massif Central displays different characteristics of these ecosystems regarding topo-edaphic context, climate, species richness, and management practices. A variable named "multifunctionality" was also calculated, as the average of centered and scaled values of six ecosystem services: biomass productivity, fodder quality, carbon stock in the soil, stability, and local rarity.

This survey across Massif Central took place during three sampling campaigns: 2008 & 2009 for the Prairies AOP project, 2014 & 2015 for the ATOUS project, and 2016-2017 for the AEOLE project. A total number of 143 grasslands were sampled and led to the "Typologie des prairies du Massif Central" or "Typology of the grasslands of Massif Central".

The present dataset shows a subsample of the original database that was completed by climatic data from the SAFRAN database, as well as topographic data from the Copernicus dataset. It was used to study the complex relationships between management, species richness, climate, and multifunctionality in an article currently in revision. All variables of the present dataset, except for the year corresponding to the sampling campaign, were centered and scaled.

To respect the anonymity of the farmers who participated in the survey, the longitude and latitude of the fields are absent from the dataset.

温带半天然草原孕育了独特的生物多样性，通过饲草生产支撑畜牧产业，并为人类社会提供诸多关键生态系统服务（ecosystem services, ESs），具备高度的多功能性。然而，受土地利用变化与气候变化影响，温带草原生态系统已成为全球受威胁最严重的生态系统之一。明晰生物多样性、气候与土地利用集约化如何通过复杂的直接与间接路径影响草原多功能性，对于精准预判这类脆弱生态系统的未来至关重要。

本研究以西欧最大的草原——法国中央高原（French Massif Central）为研究区域，评估本地植物物种丰富度（plant species richness, SR）如何调控土地利用集约化与气候对草原多功能性的影响。本次研究选取的六项关键生态系统服务包括：生物量生产力与稳定性、饲草品质、碳储存、传粉服务以及本地植物稀有度。我们在覆盖年平均气温（mean annual temperature, MAT）与干旱强度（drought severity, DS）两大未来预计加剧的气候变化驱动因子的大海拔、纬度梯度范围内，对100个施肥水平与植物物种丰富度存在显著差异的草原样地开展了采样。

通过验证性路径分析（confirmatory path analysis），我们发现植物物种丰富度是影响草原多功能性的核心驱动因子。同时，我们还检测到SR与MAT、SR与施肥水平的显著交互效应，表明温暖气候与高施肥水平可能改变生物多样性-生态系统多功能性关系。此外，相较于寒冷山地草原或低施肥水平草原，温暖低地与高施肥水平草原中，气温上升与施肥加剧会通过降低植物物种丰富度，进而间接削弱草原多功能性。干旱强度仅对部分生态系统服务产生独立影响（如饲草品质）。

综合与应用：我们明确了植物物种丰富度是通过直接与间接路径介导土地利用集约化与气候对多功能性影响的关键因子。若忽视植物物种丰富度的变化，可能会误导预测结果，甚至加剧土地利用集约化与气候变化对温带草原生态系统生态系统服务供给的负面影响。鉴于植物物种丰富度、年平均气温与施肥水平分别是生物多样性丧失、气候变化与土地利用集约化三大全球变化驱动因子的核心替代指标，本研究有助于更好地预判多交互全球变化驱动因子对草原生态系统的影响。

数据集说明
本数据集涵盖法国中央高原的100个草原样地，包含这些生态系统的地形-土壤背景、气候、物种丰富度与管理措施等多项特征。此外，我们还计算了名为‘多功能性’的变量，其取值为六项生态系统服务（生物量生产力、饲草品质、土壤碳储量、稳定性与本地植物稀有度）经中心化与标准化后的平均值。

本次横跨中央高原的野外调查共开展三次采样工作：2008年与2009年对应Prairies AOP项目，2014年与2015年对应ATOUS项目，2016年至2017年对应AEOLE项目。本次采样共涉及143个草原样地，最终形成《中央高原草原分类》（*Typologie des prairies du Massif Central* / *Typology of the grasslands of Massif Central*）。

本数据集为原始数据库的子集，补充了来自SAFRAN数据库的气候数据以及来自哥白尼（Copernicus）数据集的地形数据。本数据集曾用于一篇正在审稿中的学术论文，以探讨管理措施、物种丰富度、气候与多功能性之间的复杂关联。除采样年份外，本数据集的所有变量均经过中心化与标准化处理。

为保护参与调查的农户匿名权益，本数据集未包含样地的经纬度坐标。