Climate change could reshape the future of Chinese milk vetch in southern rice paddies

Machine learning reveals critical temperature and rainfall thresholds for one of China’s most important winter green manure crops

Shenyang Agricultural University Collaborative Journals

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Spatial patterns and climate-driven factors of Chinese milk vetch biomass in southern China's rice paddies

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Credit: Xiaoyue Wu, Hao Liang, Ruidong Chen & Songjuan Gao

Chinese milk vetch, a leguminous crop widely planted in rice paddies during winter, plays an important role in supplying nitrogen, building soil carbon, and reducing reliance on synthetic fertilizers. A new study has now mapped how its biomass varies across southern China and identified where future climate change may place this valuable green manure crop under the greatest pressure.

Using 572 field measurements from 111 monitoring sites across 13 provinces, researchers combined a Random Forest machine learning model with SHAP, an interpretable artificial intelligence method, to determine how geography, soil properties, temperature, rainfall, humidity, and sunshine influence Chinese milk vetch biomass.

“Chinese milk vetch is more than a winter cover crop. Its biomass directly affects how much biologically fixed nitrogen and organic carbon can be returned to rice fields,” said corresponding author Hao Liang of Hohai University. “Our results show that climate does not affect this crop in a simple linear way. There are clear temperature and precipitation ranges within which milk vetch performs best, and these thresholds can help guide more precise regional management under a changing climate.”

The researchers found that the average dry biomass of Chinese milk vetch was 3.23 metric tons per hectare. At the regional scale, the highest biomass was concentrated in the middle and lower reaches of the Yangtze River, particularly in areas such as Hunan, Hubei, and Jiangxi. Lower biomass was found in parts of southern and southwestern China.

The machine learning model explained 68% of the observed spatial variation. Importantly, climatic factors accounted for 40.5% of biomass variation, compared with 31.7% for geographic factors and 27.8% for soil factors.

The analysis also uncovered strong nonlinear climate thresholds. Growing-season precipitation between approximately 533 and 877 millimeters was associated with favorable biomass accumulation, while rainfall below or above this range was linked to reduced growth. Mean growing-season temperatures of about 10.7 to 13.7°C formed a broad thermal buffer, while temperatures above 13.7°C were increasingly associated with heat stress and lower biomass.

To explore what these relationships could mean in the future, the team combined its biomass model with projections from three CMIP6 climate models under four Shared Socioeconomic Pathway scenarios. Across southern China as a whole, milk vetch biomass was projected to decline by roughly 2% to 4% by 2098, but the regional picture was far more uneven.

The Huang Huai Hai single-cropping rice region was projected to experience some of the largest losses, reaching about 13% to 14% under higher-emission scenarios. In contrast, the middle and lower Yangtze River double-cropping region remained comparatively stable and could see biomass increases of approximately 1.9% to 5.9% under some scenarios.

These contrasting responses suggest that a single management strategy will not be suitable everywhere. The authors propose region-specific approaches, including adjusting sowing dates, developing stress-tolerant varieties in vulnerable areas, conserving soil moisture, and optimizing the integration of milk vetch with rice straw and nitrogen management.

The findings provide a climate-informed framework for deciding where Chinese milk vetch cultivation can remain resilient and where additional adaptation measures may be needed. They also provide field-based benchmark data that could support crop modeling and remote sensing studies aimed at improving green manure management across southern China.

 

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Journal Reference: Wu X, Liang H, Chen R, Gao S. 2026. Spatial patterns and climate-driven factors of Chinese milk vetch biomass in southern China's rice paddies. Agricultural Ecology and Environment 2: e024 doi: 10.48130/aee-0026-0022  

https://www.maxapress.com/article/doi/10.48130/aee-0026-0022 

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About Agricultural Ecology and Environment: 

Agricultural Ecology and Environment (e-ISSN 3070-0639) is a multidisciplinary platform for communicating advances in fundamental and applied research on the agroecological environment, focusing on the interactions between agroecosystems and the environment. It is dedicated to advancing the understanding of the complex interactions between agricultural practices and ecological systems. The journal aims to provide a comprehensive and cutting-edge forum for researchers, practitioners, policymakers, and stakeholders from diverse fields such as agronomy, ecology, environmental science, soil science, and sustainable development. 

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Journal

Agricultural Ecology and Environment

DOI

10.48130/aee-0026-0022

Method of Research

Experimental study

Article Title

Spatial patterns and climate-driven factors of Chinese milk vetch biomass in southern China's rice paddies

Article Publication Date

28-Sep-2026

Study shows wolverine populations affected by recreation, roads

UCalgary scientists work with partners to research density across western Alberta and eastern British Columbia

University of Calgary

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A skier comes across a wolverine track in the backcountry near Golden, B.C.

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Credit: Mirjam Barrueto/University of Calgary

Wildlife researchers have found that both recreation and roads affect wolverine populations in Canada's Rocky Mountains and Columbia Mountains.

It’s believed to be the first time that a study has shown, at a landscape scale, that recreation is linked to lower population density in a carnivore.

The study, led by Dr. Mirjam Barrueto as part of her PhD research at UCalgary, was published on Sept. 29 in Biological Conservation, a peer-reviewed international journal in conservation and environmental science. Co-authors include her supervisor, Dr. Marco Musiani, PhD, an adjunct professor in the Faculty of Science, as well as scientists from Parks Canada, the Nature Conservancy of Canada (NCC) and Montana State University.

“We wanted to figure out how the population is doing and what kind of impacts there are,” Barrueto says in an interview. “We found that there were very few wolverines in the Upper Columbia region” in southeastern British Columbia.

The paper, which covers one of the largest areas examined for wolverines, shows that there are fewer than 300 wolverines across 81,800 square kilometres in western Alberta and eastern British Columbia.

Barrueto says it could be about 30 per cent higher without current recreation and road levels.

“I was a bit surprised by the impact of recreation, to be honest,” she says. “Unsurprisingly, we found that road density is the other main predictor for density of the population — and, also for females. Road density was also a finding in previous studies.”

Recreation data, she notes, is based on publicly available heat maps from recreational apps. It represents backcountry skiing, including heliskiing and cat skiing, cross-country skiing and hiking in both winter and summer.

Barrueto says it doesn’t include snowmobiling, but notes that activity is likely captured in the road density data.

“Both human disturbances affected wolverine density,” explains Barrueto. “In areas with more disturbances, either road density or recreation, there were fewer individuals than in areas with less.

“That’s on a population scale, it’s not that they just avoided a small area, there were actually fewer individuals living there.”

Barrueto says researchers knew wolverines avoid busy areas, but they learned new information through the latest study — including that the impact of disturbances on wolverine numbers is sex specific.

Road density, as an example, affects females the most. That’s important because females are key for population recovery, particularly because wolverines are slow to reproduce and only have one to three babies every few years.

“They’re pretty small carnivores,” says Barrueto. “It generally seems stressful for most of these animals to be interacting with a human.”

She says the research is important for anyone who works or plays in wolverine habitat, herself included, to be aware of our impact.

“Do we want to have a landscape with just deer and coyotes? Or do we want to have a landscape that has space for wild things?”

The research makes five recommendations that include maintaining roadless and low road density areas; protecting low-disturbance, high-quality wolverine habitat; and limiting recreation in reproductive areas.

“Now that we understand some of the impacts, we can opt to start making management and planning decisions, so that wolverines will thrive in these places we all love,” says Barrueto.

That’s the part that co-author Dr. Aerin Jacob, director of science and research and Weston Family senior scientist at the Nature Conservancy of Canada, zeros in on.

"Our findings are stark," says Jacob. "What gives me hope is that this gives us something to act on, at every level. Whether that’s deciding about building trails, protecting and restoring habitat, or working to prevent and reduce impacts.

“That kind of collaboration is what effective conservation actually looks like,” she adds.

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Journal

Biological Conservation

DOI

10.1016/j.biocon.2026.112108

Method of Research

Observational study

Subject of Research

Animals

Article Title

Sharing the snow – outdoor recreation and roads reduce the density of a rare carnivore

Article Publication Date

29-Sep-2026

 

Coast redwoods slow their ‘breathing’ and ‘eating’ when temperatures spike

Study links high temperatures to physiological changes in the world’s tallest trees

University of California - Davis

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Sun peeks through the redwood tree canopy in the UC Davis Arboretum. 

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Credit: Gregory Urquiaga/UC Davis

California’s iconic coast redwoods are used to growing in cool, coastal areas where the average temperature is around 59 degrees F. But as average yearly temperatures rise and heatwaves push to 100-degree-plus spikes, the trees are responding by slowing the very operation that nourishes them, according to a study from the University of California, Davis.

When under heat stress, the world’s tallest trees slow photosynthesis, the chemical reaction that turns sunlight, water and carbon dioxide from the air into carbon the trees use to grow and perform other essential processes. It’s as if the trees slow their “breathing” and, as a result, their “eating.” The findings raise alarm about the fate of the redwood forests, especially in their already vulnerable central, southern and eastern habitats in the state.

The study, published in JGR Biogeosciences, marks the first time anyone has studied the effects of heat on coast redwood photosynthesis, said lead author Lily Klinek, a Ph.D. candidate with the Plant Optics Lab in the UC Davis Department of Plant Sciences. The team used an array of measurements taken over three summers in a redwood forest in Mendocino County.

When temperatures topped 86 degrees, as they did during the summers of 2022 and 2024, the temperatures of some leaves were nearly 20 degrees F higher than the temperature of the air. It’s a sign of stress. 

“The leaves aren’t able to cool down,” Klinek said, which means they probably closed their stomata – the tiny, mouth-like pores that “breathe” in the air’s carbon dioxide. Further tests in the lab at temperatures ranging up to 110 degrees F confirmed photosynthesis was reduced, even when their “mouths” were open and taking in plenty of carbon dioxide.

“We don’t know what the upper temperature thresholds are for redwood photosynthesis and mortality,” Klinek said. “With this work, we see there’s a significant impact of heat on photosynthesis and physiology. That’s an important start for figuring out what parts of the redwood range are at risk, knowing what to expect and trying to intervene for the health of redwood ecosystems.”

Redwoods sweat, too – unless they’re thirsty

Under the right circumstances, trees can regulate their temperature through a process called evapotranspiration. They use those tiny mouths, or stomata, to “sweat” out some of the moisture they hold inside to cool off.

“It’s similar to the way we sweat to stay cool,” Klinek said. 

Heat spikes not only raise air temperatures, but also burn off the coastal fog that redwoods depend on for much of their water. The huge gap found between air and leaf temperatures indicated that the leaves likely closed their stomata to avoid losing precious water and overheated as a result, Klinek explained.

In the lab, the researchers put their leaf samples in jars of water, so they had access to plenty of water and could sweat all they pleased. Still, photosynthesis was reduced, even as the leaves kept their stomata open. 

“This means that, even if the redwood trees have more water to sweat with, the heat might still impair their breathing and functioning,” Klinek said.

Additional authors include Troy Magney, Jessie Au and Milagros Rodriguez-Caton of UC Davis; Mukund Palat Rao of Columbia University; Lauren Fety of The Conservation Fund; and George Koch of Northern Arizona University.

The study was funded by the National Science Foundation and California Forestry and Fire Protection, and it was conducted in cooperation with The Conservation Fund.

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DOI

10.1029/2026JG010052

Article Title

Summer Heat Stress Downregulates Photochemistry in Coast Redwoods

Article Publication Date

22-Sep-2026

Redwood branches rest in jars of water in the lab at UC Davis to keep their leaves wet and stomata open. This helped researchers measure rates of photosynthesis at different temperatures. 

UC Davis researchers covered small redwood branches in aluminum foil for 20 minutes to impose darkness, removed the foil, then measured their responses to light to assess their capacity for photosynthesis. They learned the trees slow their metabolism during heat spikes. 

Credit

Lily Klinek/UC Davis

The UC Davis Plant Optics Laboratory team pauses their field work in Mendocino, California to pose for a group selfie in 2022. From left, they are Associate Professor Troy Magney, and researchers Lauren Fety, Jessie Au and first author Lily Klinek. 

Credit

Troy Magney/UC Davis

 

Cutting ultra-processed food from school menus will be tricky, Stanford Medicine study finds

Challenges to healthier school menus

Stanford Medicine

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Starting in July 2029, public schools are required to start phasing out ultra-processed foods under a new California law that prohibits schools from serving foods high in sugar, fat, salt and certain artificial food additives.

The changes should benefit kids’ health, but may be challenging for schools to implement, according to a Stanford Medicine study.

“It’s easy to say, ‘Let’s remove ultra-processed foods from school meals,’ but school districts will likely face many challenges in implementing this policy,” said the study’s senior author, Anisha Patel, MD, professor of pediatrics at Stanford Medicine.

The research team’s work, to be published Sept. 28 in Public Health Nutrition, identified the top challenges that school food service directors expect to face. Budget constraints, limited staff, difficulty with food procurement and inadequate kitchen infrastructure were their biggest concerns, the study reports.

Lawmakers will likely need to direct more funding to school food budgets to help put the new legislation into practice, said lead study author Andrea Pedroza-Tobias, PhD. She was an instructor in pediatrics at Stanford Medicine when the study was conducted and is now an assistant professor in residence at the University of California, Irvine. “It’s an investment in the future of these kids. For many California children, two of the three meals they eat per day come from their schools.”

Evaluating barriers

The new California statute, AB 1264, aka the Real Food, Healthy Kids Act, requires elimination of certain ultra-processed foods considered harmful to children’s health from school menus by July 1, 2035. Several other states are considering similar legislation to reduce kids’ risk for obesity and related health problems, and the latest version of the Dietary Guidelines for Americans encourages people to consume fewer ultra-processed foods. The U.S. Department of Health and Human Services also recently announced a $32.5 million initiative to help school districts test how to deliver healthier food to students.

Ultra-processed foods can be defined in several ways. Researchers typically use the Nova classification: industrially created food with additives that enhance the item’s taste or convenience. The new California law uses a more specific definition, with more details about which food additives are prohibited and the balance of nutrients required. Heat-and-serve foods, flavored yogurt, frozen pizza and breakfast cereals are common examples of ultra-processed foods that currently appear on school menus.

The Stanford Medicine team, along with their colleagues, interviewed food service directors from 20 school districts in California’s San Joaquin Valley, an agricultural region with many low-income families whose students depend on school meals. In the interviews, the researchers asked participants to rate how much of a barrier they anticipated certain factors would be in eliminating ultra-processed menu items. The research team also asked open-ended questions to allow detailed responses about various challenges.

Fiscal and logistical challenges

One major category of challenge was fiscal. Eliminating ultra-processed foods — which are cheap and easy to heat and serve with minimal kitchen equipment — will strain budgets, food service directors said.

In 2021, California began providing meals to all K-12 public school students for free, regardless of families’ incomes. Federal and state funding reimburse districts around $4.60 per lunch served, and with more kids eating the meals, schools can now offer more and better menu choices.

“That has been something positive for school districts: Universal school meals increased participation, which brought more money to districts’ food service programs,” Pedroza-Tobias said.

But less-processed items will increase costs, likely outpacing existing budgets, and will make some foods harder to procure.

Amanda Harvey, director of nutrition services for the Fresno Unified School District, who was a member of the community advisory board for study, encountered these problems when her team eliminated products containing food dye from their menus.

For instance, it was difficult for her school district to purchase pickles made without green dye No. 5. “They’re pricey for pickles, and it can be quite challenging for our vendor to get them,” Harvey said. “So sometimes we have a shortage of pickles because of this food dye.”

Measures that reduce food costs may become harder for schools to use, the researchers noted. For instance, districts can purchase inexpensive commodity foods through the U.S. Department of Agriculture — such as raw chicken — which they may send to a food processor in exchange for easier-to-serve items such as chicken nuggets. “While this practice helps schools that don’t have the kitchen infrastructure for anything but ready-to-eat foods,” Pedroza-Tobias said, “it can inadvertently increase the amount of ultra-processed food on the menu.” 

Food service directors also identified challenges related to school staffing and infrastructure. Many schools employ part-time staff to heat and serve foods; these individuals may not be trained to cook similar foods from scratch. Scratch cooking also takes more time, and moving staff from part-time to full-time jobs would require larger budgets for staff salaries and benefits.

Many schools lack fully equipped kitchens, and retrofits are difficult. Harvey’s team explored whether they could make sandwiches from scratch in some of the elementary schools in her district that have kitchens designed only for heat-and-serve meals. The local health department denied the request because the kitchens did not meet permitting standards for scratch cooking, she said.

“They said, ‘In order to get these 50 schools permitted, you would need to add new sinks, drains and hoods,’” Harvey said. This would have cost millions of dollars, which would have had to come from district infrastructure funds, not the cafeteria budget, she added. The Fresno school district has a central kitchen facility equipped for scratch cooking, so Harvey’s team opted to make sandwiches there instead, but smaller school districts may lack that option.

Student preferences may also be a challenge, although some food service directors reported that students like certain fresh menu items. Harvey’s district works with chefs in developing scratch-made items they can add to their menus. Students also appreciate having more options on the menu, she said, adding that when her district began offering menu choices at elementary schools, “We definitely saw a huge decrease in parent and student complaints.”

Strategies for change

The research team also heard about how some districts have addressed these concerns. Some have bridged fiscal gaps with grant funding, although participants said that “if they get this funding for one year, and are not sure they’ll have the same money next year, they don’t feel like they can make sustainable changes,” Pedroza-Tobias said. Applying for grants also requires staff time, putting smaller districts with fewer support staff members at a disadvantage.

One district succeeded in making most of its food from scratch, in part because the food service director was a chef who also had a background in nutrition. “They also did a lot of engagement with families and students to increase the acceptance of scratch-cooked meals,” Pedroza-Tobias said. “For instance, they had a junior chef competition where students submitted a recipe, and they selected some of these recipes to cook in the school kitchen.”

The researchers hope their findings will help legislators and school districts navigate the challenges of serving healthier school meals, she said. Patel added, “Moving from ultra-processed food to scratch cooking requires an upfront investment, but healthier school meals can pay off in the long term by preventing health care costs associated with diseases such as obesity, Type 2 diabetes and cardiovascular disease.”

Researchers from the Dolores Huerta Foundation, Cultiva la Salud, and the Nutrition Policy Institute of the University of California Agriculture and Natural Resources contributed to the study.

The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (grant P30DK092924); the National Heart, Lung, and Blood Institute (grant K24HL169841); Stanford’s Maternal and Child Health Research Institute; the William and Nancy Thompson Family Foundation; and Stanford Impact Labs.

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About Stanford Medicine

Stanford Medicine is an integrated academic health system comprising the Stanford School of Medicine and adult and pediatric health care delivery systems. Together, they harness the full potential of biomedicine through collaborative research, education and clinical care for patients. For more information, please visit med.stanford.edu.

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Journal

Public Health Nutrition

DOI

10.1017/S1368980026103139

Article Title

Reducing ultra-processed and increasing scratch-cooked school meals: perceived barriers and facilitators from food service directors

Article Publication Date

27-Sep-2026