Optimizing rangeland decision making by unraveling geographic variation in the timing of forage sensitivity to weather

OPTIMIZING RANGELAND DECISION MAKING BY UNRAVELING GEOGRAPHIC VARIATION IN THE TIMING OF FORAGE SENSITIVITY TO WEATHER

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

AFRI COMPETITIVE GRANT

Reporting Frequency

Annual

Accession No.

1030793

Grant No.

2021-67034-40252

Cumulative Award Amt.

$79,016.30

Proposal No.

2023-03643

Multistate No.

(N/A)

Project Start Date

Dec 15, 2022

Project End Date

Sep 14, 2024

Grant Year

2023

Program Code

[A7201]- AFRI Post Doctoral Fellowships

Project Director
Felton, A.

Recipient Organization
MONTANA STATE UNIVERSITY
(N/A)
BOZEMAN,MT 59717

Performing Department
(N/A)

Non Technical Summary
More variable and extreme weather patterns, such as droughts rivaling that of the dustbowl, are a prominent feature of climate change projections and pose a fundamental challenge to rain-fed rangeland production systems. Ranchers have the potential to mitigate the uncertainty posed by increasing climatic variability through pro-active decision making that can have profound economic implications, but this relies upon knowledge of when to implement such decisions. And while a growing body of research has shown that forage production is sensitive to weather variation during relatively narrow periods during the growing season, we lack an understanding of how this timing of forage sensitivity to weather varies at the spatial scales in which decision making occurs, from the landscape, county, and state all the way to the scale of the ecoregion. The goal of this proposal is to improve our understanding of rangeland responses to weather variability by focusing onwhenprecipitation most affects forage production among different ranges in the western United States. Understanding this timing will provide about critical decision dates: the dates during the growing season by which ranchers should initiate drought mitgation strategies should be initated if drought conditions have emerged.

Animal Health Component

25%

Research Effort Categories

Basic

75%

Applied

25%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0799	1070	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0799 - Rangelands and grasslands, general;

Field Of Science
1070 - Ecology;

Keywords

Goals / Objectives
Ranchers have the potential to mitigate the uncertainty posed by increasing climatic variability through pro-active decision making that can have profound economic implications, but this relies upon knowledge of when to implement such decisions. A growing body of research has shown that forage production is sensitive to weather variation during relatively narrow climatic windows during the growing season. However, we lack an understanding of how this timing of forage sensitivity to weather varies at the spatial scales in which decision making occurs, from the landscape, county, and state all the way to the scale of the ecoregion. The goal of this proposal is to improve our understanding of rangeland responses to weather variability by focusing onwhenprecipitation most affects forage production among different ranges in the western United States. To achieve this goal, we will focus on three objectives: 1) integrate novel, high resolution, and long-term remote sensing data products of intra-annual forage production with intra-annual climate data on the same spatial and temporal scales, 2) unravel geographic patterns and variation in the timing of forage sensitivity to precipitation, and 3) apply spatiotemporal analyses to reveal how this timing varies across climatic gradients within and across different rangeland ecoregion types. This research will optimize existing weather-based rangelandmanagement strategies by providing a broad geographic understanding of critical decision dates: the dates by which drought mitigation strategies should be executed to avoid further, unnecessary ecological degradation to ensure rangeland sustainability and maintain profitability. An emergent goal of this work now pertains to the training of a PhD student in rangeland ecology and remote sensing analysis of rangeland systems.

Project Methods
Our general approach is to combine novel high-resolution remote sensing data products of forage production and weather datato conduct spatiotemporal analyses that produce insights about geographic variation in the timing of forage sensitivity to rainfall.Thus, thegoal of the proposed research is to build of a geographic understanding ofwhenforage is most sensitive to climatic variation during the growing season. Emerging high-resolution remote sensing data on long-term primary productivity (i.e. plant growth) dynamics offers promise for 'scaling-up' our understanding of rangeland forage production to the spatial scales at which decision making actually occurs. Spatiotemporal statistical approaches can use these spatially explicit, remotely sensed data to produce robust inferences on geographic and temporal variation in rangeland sensitivity to climate variability. While wehave completed akey research objective of the initial proposal, which was to unravel spatial variation in the timing of rangeland sensitivity to climate variability,that analysisultimately deviated slightly from the proposal by focusing specifically on drought instead of both wet and dry precipitation pulses. Nevertheless, we have downloaded, formatted, and analyzed the geospatial datasets needed for this analysis. Thus, there is the data and code available for a graduate student to now look at the timing of rangeland responses to both positive and negative fluctuations in precipitation and to inform about ctual critical decision dates; the dates during the growing season by which ranchers should take action to avoid further harm to their production systems during drought.The proposed research will focus on two expansive ecoregions in the central and northern Great Plains: the semi-arid shortgrass steppe and the northern mixed-grass prairies.The proposed research will leverage novel remote sensing data products with over 30 years of coverage.Recent advances in estimating primary productivity from reflectance-based (e.g. greenness) satellite data have resulted in the ability to partition primary productivity into different functional groups. Wewill leverage a novel remote sensing data product that partitions primary productivity into herbaceous (both annual and perennial grasses and forbs) functional groups across US rangelands. Following this integration, we will specifically map out 1) critical decision dates and 2) the timing of the maximum sensitivity of forage production to precipitation variability druing the growing season.

Progress 12/15/22 to 09/14/24

Outputs
Target Audience:To date, our target audience has primarily focused on the scientific community. In January of 2023, a manuscript reporting the research results from this project was published in the journal Global Change Biology.This journal is a relatively broad scientific audience focused primarily on the environmental impacts of global environmental change. Therefore, the target audience for this reporting period primarily consisted of the broader scientific community. In July of 2024, a manuscript reporting the research results from a part of this project was submitted to and is currently in review in the journalOecologia.This journal is a relatively broad scientific audience focused all aspects of ecology. Therefore, the target audience for this reporting period primarily consisted of the broader scientific community of ecologists. In August of 2023, a trainee in PD Felton's lab presented on the preliminary findings of this work at the Ecological Society of America annual meeting in Portland, OR. This again targets a broad audience of ecologists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Both a post-graduate Research Assistant and PhD student in PD Felton's lab have gained valuable experience in rangeland, grassland, and ecosystem ecology as well as computer coding and spatiotemporal analyses. Important professional development experiences for the trainees include Research presented their research as a poster at the 2023 Ecological Society of America conference. The Research Assistant has also begun writing the manuscript for the project they are working on. How have the results been disseminated to communities of interest?There are two ways research results have been disseminated. The first is throughjournal publications; key research findings were published in early 2023in the journalGlobal Change Biologywith another mansucript submitted (and currently under review) toOecologia.The second is through an oral presentation at the 2022 Ecological Society of America conference and aposter presented at the 2023 Ecological Society of America conference. The results have been thoroughly communicated to the scientific communicated but not strongly to stakeholders such as ranchers. These efforts wil continue past the funding cycle of this grant. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have made two key advancements in our knowledge of the functioning of western US rangelands. First (and as mentioned in a previous report), we have made an important advancement in our understanding of when, throughout the year, extreme drought most impacts forage production in US rangelands. We have shown that, across rangelands spanning New Mexico to Montana, peak reductions in forage production tend to occur in mid- and late June during extreme drought and that spring forage production is generally not impacted during dry years. Therefore, reductions in forage production are restricted to the summer months (June-August), with peak reductions occurring in June. Furthermore, dry years tend to advance the days by which half of total forage production is reached, potentially shifting decision timelines by roughly two weeks. The magnitude of 'peak reductions' in forage production tends to increase from north to south, both on an absolute and percentage basis. Ranchers can expect the negative impacts of drought to be greatest in June generally, but that that the magnitude of impacts to forage during this time will be particularly strong for rangelands in the southern plains and southwest. This implies high vulnerability of southwestern rangelands to drought intensification. This work was published in the high-impact journalGlobal Change Biology. Second, we have made an important advancement in our understanding of "legacy effects" across western US rangelands and specifically how previous-year conditions shape current-year rangeland functioning. We have shown that legacy effects exert a widespread effect on interannual variability in primary productivity (NPP) (e.g., forage production) across rangelands spanning annual and perennial grasslands to hot and cold deserts. Previous-year NPP anomalies were the strongest predictor of current-year NPP anomalies, both across the entire time series and during specific extreme-to-average year transitions. The association between previous- and current-year NPP anomalies was consistently positive, indicating that a productive previous-year will tend to result in a productive current-year, and vice-versa, even after accounting for the effect of current-year PPT. The strength of legacy effects increased slightly with increasing mean annual precipitation and decreased slightly with an increase in the average fraction of herbaceous NPP. This implies that legacy effects consistently effect current-year NPP in rangelands and that consideration of these effects can improve predictions of temporal variation in rangeland NPP.This manuscript describing this work is currently in review at the long-standing journalOecologia, with a trainee in PD Felton's lab as the first author.

Publications

Progress 12/15/22 to 09/14/23

Outputs
Target Audience:In January of 2023, a manuscript reporting the research results from this project was published in the journal Global Change Biology.This journal is a relatively broad scientific audience focused primarily on the environmental impacts of global environmental change. Therefore, the target audience for this reporting period primarily consisted of the broader scientific community. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A post-graduate Research Assistant in PD Felton's lab has gained valuable experience in rangeland, grassland, and ecosystem ecology as well as computer coding and spatiotemporal analyses. This Research Assistant is leading a component of this research and even presented their research as a poster at the 2023 Ecological Society of America conference. The Research Assistant has also begun writing the manuscript for the project they are working on. How have the results been disseminated to communities of interest?There are two ways research results have been disseminated. The first is through a journal publication; key research findings were published in early 2021 in the journal Global Change Biology. The second is through a conference poster presented at the 2023 Ecological Society of America conference. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, we will continue working on analyses and manuscript development for the research component of this grant focusing on 'legacy effects' of previous-year conditions and how they mediate the sensitivity of forage production to current-year precipitation. In this time, we expect to finalize our analyses, complete a manuscript draft, and submit to a journal for publication. This publication will be led by a junior researcher. Thus, by the next reporting period we expect to have submitted, if not published, a manuscript to a journal communicating these research results.

Impacts
What was accomplished under these goals? We have made an importantadvancement in our understanding of when, throughout the year, extreme drought most impacts forage production in US rangelands. We have shown that, across rangelands spanning New Mexico to Montana, peak reductions in forage production tend to occur in mid- and late-June during extreme drought and that spring forage production is generally not impacted during dry years. Therefore, reductions in forage production are restricted to the summer months (June-August), with peak reductions occurring in June. Furthermore, dry years tend to advance the days by which half of total forage production is reached, potentially shifting decision timelines by roughly two weeks. The magnitude of 'peak reductions' in forage production tends to increase from north to south, both on an absolute and percentage basis. Ranchers can expect the negative impacts of drought to be greatest in June generally, but that that the magnitude of impacts to forage during this time will be particularly strong for rangelands in the southern plains and southwest. This implies high vulnerability of southwestern rangelands to drought intensification.

Publications

Type: Journal Articles Status: Published Year Published: 2023 Citation: Felton, Andrew J., and Gregory R. Goldsmith. "Timing and magnitude of drought impacts on carbon uptake across a grassland biome." Global Change Biology 29.10 (2023): 2790-2803.