Quantifying Optimal Rates of Litter Retention to Maximize Annual Net Primary Productivity on Mixed-Grass Prairie

doi:10.1016/j.rama.2016.08.009

Rangeland Ecology & Management

Volume 70, Issue 2, March 2017, Pages 219-224

https://doi.org/10.1016/j.rama.2016.08.009 Get rights and content

Abstract

Optimal rates of litter retention for maximizing annual aboveground net primary productivity (ANPP) were investigated in native mixed-grass rangelands in Saskatchewan, Canada. The study was conducted on 18 independent study sites on brown and dark brown Chernozem (Mollisol) soils during the 2011 and 2012 growing seasons. Each site contained 30 treatment plots with two control plots and 28 treatment plots receiving between 1 and 2 290 g/m² of added plant litter sourced from a reference site. Soil moisture values were recorded for each plot in May, June, and July, while forb, graminoid, and total ANPP were harvested at the end of the growing season. Soil moisture-litter relationships were driven by weather patterns with significant differences between years. Graminoid ANPP-litter relationships were nonlinear with peaks in productivity between 54 and 412 g/m² of litter mass in the brown soil zone and between 27 and 157 g/m² of litter mass in the dark brown soil zone. Forb ANPP was highest at the lowest litter masses and was not significantly influenced by study year or soil zone. The recommended litter retention rates in provincial range health assessment guidelines are accurate for the dark brown soil zone but are lower than the levels identified here for the more arid brown soil zone.

Introduction

A key element of sustainable rangeland management is to retain a portion of aboveground plant biomass at the end of the growing season to improve moisture retention and productivity in the following season (Bartolome et al., 1980, Knapp and Seastedt, 1986, Abouguendia, 1990, Willms et al., 1993, Willms et al., 2002, Pylypec and Romo, 2003, Bartolome et al., 2007, PCAP, 2008, Wang et al., 2011, Bork and Irving, 2015). Rangeland management guides developed for Saskatchewan, Canada, suggest the standard rate of carryover should be 45% of plant material at the end of the grazing season (Abouguendia, 1990), or an average of 67 g/m² for a Loamy Range Site in the mixed-grass prairie (PCAP, 2008). Litter biomass, depth, and distribution are important drivers of grassland species diversity and species composition through mechanisms including physical interference, nutrient availability, shading, altering cues necessary for seed germination and hosting seed predators and pathogens, and wildlife habitat (Knapp and Seastedt, 1986, Facelli and Pickett, 1991, Bosy and Reader, 1995, Xiong and Nilsson, 1999, Jensen and Gutekunst, 2003, Fisher and Davis, 2010, Lamb, 2008, Letts et al., 2015).

Litter effects on soil moisture and temperature are thought to be a key driver of grassland productivity. Soil moisture is tightly linked to nutrient availability and grassland productivity, particularly in semiarid regions (Jong and MacDonald, 1975, Facelli and Pickett, 1991, Deutsch et al., 2010a, Gao et al., 2011). Soil moisture retention is important under most climatic conditions, including dry periods, which are predicted to occur more frequently due to global climate change along with an average increase in air temperature (Shepherd and McGinn, 2003, IPCC, 2007, Kulshreshtha, 2011). Shading of the soil surface by litter lowers soil temperature and reduces evaporation, resulting in more soil water available to microbes involved in nutrient cycling and for transpiration (Weaver and Rowland, 1952, Hopkins, 1954, Facelli and Pickett, 1991, Booth et al., 2005, Deutsch et al., 2010a, Deutsch et al., 2010b, Wang et al., 2011). Litter can promote infiltration of water into the soil profile (Weaver and Rowland, 1952, Hopkins, 1954, Naeth et al., 1991, Dormaar and Carefoot, 1996), though high loads of litter can have negative effects on soil moisture through interception above the soil surface (Weaver and Rowland, 1952, Knapp and Seastedt, 1986, Facelli and Pickett, 1991). Litter can also prevent soil erosion via raindrop impacts and the associated disaggregation of soil particles (Dyksterhuis and Schmutz, 1947, Facelli and Pickett, 1991, Dormaar and Carefoot, 1996).

While recommendations for litter retention are common in range health guidelines, aspects of the relationships among litter, soil moisture, and annual net primary productivity (ANPP) remain poorly understood. In particular, the effects of very heavy litter accumulations on productivity appear to be negative in some communities (Pylypec and Romo, 2003) but have not been extensively documented. The objectives of the study were 1) to address the relationship between litter mass and ANPP to quantify the optimal amount of litter retention to maximize ANPP on native Saskatchewan mixed-grass rangelands and 2) to examine the relationships between litter mass and soil water content, as soil moisture is a common mechanism linking litter and ANPP.

Section snippets

Study Area

The experiments were conducted in 2010 − 2011 and 2011 − 2012 on three large pastures representative of native mixed-grass prairie in Saskatchewan, Canada (Romo et al., 2013). The three locations chosen were the Matador and Monet Community Pastures in the brown soil zone and King George Grazing Co-Op in the dark brown soil zone (Fig. 1a). Matador is a 26 000-ha provincially managed pasture, Monet is an 18 000-ha federally managed pasture, and King George is a 2 000-ha privately managed pasture. All

Litter and ANPP

Graminoid ANPP peaked at a moderate level of litter mass in both the brown and dark brown soil zones. The best graminoid model included separate relationships between litter and ANPP in each soil zone with ANPP peaking at 181.2 g/m² (5% range 54.0 − 411.6 g/m²) in the brown soil zone and 67.2 g/m² (5% range 27.3 − 156.6 g/m²) in the dark brown soil zone (Table 1; see Fig. 2a and b). Forb ANPP was highest at the lowest level of litter mass, with ANPP within 5% of maximum when litter ranged between 0

Discussion

Here we investigate the optimal levels of litter retention needed to maximize productivity on native Saskatchewan mixed-grass rangelands. Graminoid ANPP peaked in the brown soil zone between 54 and 412 g/m² of litter and between 27 and 157 g/m² of litter in the moister dark brown soil zone. Cool-season graminoids account for the majority of production in this system, and thus the total ANPP-litter relationship mirrored the graminoid ANPP pattern. The general pattern of improved productivity

Implications

In this study, forb ANPP was highest without a litter layer, while graminoid ANPP peaked between 54 and 412 g/m² in the brown soil zone and 27 and 157 g/m² in the dark brown soil zone. The guideline of 67.2 g/m² of litter retention for a healthy mixed-grass rangeland on a Loamy Range Site (PCAP, 2008) is within the range of litter needed to maximize ANPP in the brown soil zone; however, given the variability in litter-ANPP responses between sites, 67.2 g/m² of litter is likely insufficient on

Acknowledgments

Jim Romo initiated this project and implemented the experiments. Jeremy Simpson (Matador Community Pasture), Luke Ellingson (Monet Community Pasture), and patrons of the King George Grazing Co-Op provided site access. Peggy Ryan led fieldwork with assistance from A. Johnson, B. Lardner, Y. Wei, X. Tian, J. Li, K. Aikens, J. Spencer, L. Wang, K. Fink, N. Poulin, Y. Abu, B. Letts, R. Bibi, X. Zhang, K. Sultana, M. Tabsim, and K. Ellingson.

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^☆: Funding came from a Saskatchewan Agriculture Development Fund grant (20090262) to Jim Romo, Eric Lamb, and Yuguang Bai and a NSERC Discovery Grant to Eric Lamb.

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Quantifying Optimal Rates of Litter Retention to Maximize Annual Net Primary Productivity on Mixed-Grass Prairie☆

Abstract

Introduction

Section snippets

Study Area

Litter and ANPP

Discussion

Implications

Acknowledgments

Rangelands

Agriculture, Ecosystems & Environment

Basic and Applied Ecology

Geoderma

A practical guide to planning for management and improvement of Saskatchewan rangeland

Responses of a California annual grassland to litter manipulation

Journal of Vegetation Science

Effects of residual dry matter on net primary production and plant functional groups in Californian annual grasslands

Grass and Forage Science

Influence of natural mulch on forage production on differing California annual range sites

Journal of Range Management

Controls on nitrogen cycling in terrestrial ecosystems: a synthetic analysis of literature data

Ecological Monographs

Mechanisms underlying the suppression of forb seedling emergence by grass (Poa pratensis) litter

Functional Ecology

Multimodel inference: understanding AIC and BIC in model slection

Sociological Methods & Research

Separation of grassland litter and ecosite influences on seasonal soil moisture and plant growth dynamics

Plant Ecology

Implications of crop residue management and conservation tillage on soil organic matter

Canadian Journal of Plant Science

Natural mulches or "litter" of grasslands: with kinds and amounts on a Southern prairie

Ecology

Plant litter: its dynamics and effects on plant community structure

Botanical Review

From Wiens to Robel: A review of grassland-bird habitat selection

The Journal of Wildlife Management

Resource manipulation effects on net primary production, biomass allocation and rain-use efficiency of two semiarid grassland sites in Inner Mongolia, China

Oecologia

Effects of fire, topography and year-to-year climatic variation on species composition in tallgrass prairie

Vegetatio

Effects of mulch upon certain factors of the grassland environment

Journal of Range Management

Climate change 2007-the physical science basis: Working group I contribution to the fourth assessment report of the IPCC

Detritus accumulation limits productivity of tallgrass prairie

BioScience