Effects of agricultural land-use intensity on multiple ecosystem services in subtropical grasslands

Yuxi Guo, School of Forest Resources and Conservation, University of Florida, Fort Lauderdale, FL, Elizabeth H. Boughton and Gene Lollis, Buck Island Ranch, Archbold Biological Station, Venus, FL, Hilary Swain and Grégory Sonnier, Archbold Biological Station, Venus, FL, Carl J Bernacchi, Department of Plant Biology, University of Illinois, Urbana, IL, Patrick J. Bohlen, Arboretum, University of Central Florida, Orlando, FL, Evan DeLucia, DOE Center for Advanced Bioenergy and Bioproducts Innovation, University of Illinois at Urbana-Champaign, Urbana, IL, Nuria Gomez-Casanovas, Institute for Sustainability, Energy and Environment; Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, Jed P. Sparks, Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, Jiangxiao Qiu, School of Forest Resources & Conservation, University of Florida, Gainesville, FL

Background/Question/Methods
Grasslands provide diverse ecosystem services at local to regional scales. In addition to food production, grasslands sustain many critical regulating and supporting services that are often underappreciated, primarily due to limited understanding of their quantitative and economic-value estimates. Sustainable management of grasslands requires comprehensive assessment of multiple ecosystem services and their relationships resulting from different management strategies. Much research has focused on temperate or arid/semi-arid grasslands, whereas subtropical grasslands, unique with humid climate and distinctive biophysical characteristics and management practices, have received less attention. Hence, in this research we aim to: (1) assess effects of land-use intensity on six major ecosystem services in subtropical grasslands, including soil fertility, water quality maintenance, carbon storage, biodiversity maintenance, invasion resistance, and forage and livestock production; and (2) investigate if tradeoffs and/or synergies among ecosystem services exist and how their relationships are altered by land-use intensity. We synthesized a large dataset encompassing 27 indicators of ecosystem functions and services from 2003 to 2019 in an extensively-studied long-term research site at the Archbold Biological Station’s Buck Island Ranch (Florida, USA) that is managed under two land-use intensities exemplary of the region. Effects of land-use intensity were quantified using linear mixed-effects models and standardized effect size.
Results/Conclusions
Our results demonstrated that compared to low-intensity land use, high-intensity land use resulted in: higher soil fertility with higher plant-available phosphorus (p<0.05); favored carbon stock with greater above- and below-ground primary productivity; improved forage quality with higher phosphorus content and in vitro organic matter digestibility; served higher cattle stocking density; and had mixed effects on water quality of adjacent ditches (i.e., less ammonia and total nitrogen, but more phosphate and total phosphorus). However, high-intensity land use also: negatively affected grasslands biodiversity (as reflected in lower plant richness, ⍺- and β-diversity); reduced invasion resistance (indicated by presence of more invasive plant species); and emitted more greenhouse gases (i.e., CO2 and CH4). Land-use intensity also altered relationships among grassland ecosystem services. For example, the relationship between plant diversity and invasion resistance was negative in high-intensity grasslands but turned positive in low-intensity grasslands. We also found stronger positive relationships between soil nutrients and forage quality in low-intensity grasslands than those in high-intensity grasslands. Collectively, our results suggest land-use intensity significantly alters the amount, composition and relationships of multiple ecosystem services supply. Enhanced knowledge of tradeoffs and synergies from land-use intensification will help inform regional sustainability priorities and management in subtropical grasslands.