Dozens of China's endangered plants have seen stable growth in their numbers over several decades thanks to improved conservation efforts, a survey on protected species said.

The survey began in 2012, and its major findings on 283 key plant species were posted on the website of the National Forestry Administration on Feb 10.

Thousands of staff members from the forestry departments of 31 provinces, autonomous regions and municipalities on the Chinese mainland were involved in the survey. The previous large-scale flora survey in China was conducted between 1997 and 2003.

Of the 54 plant species with extremely small populations investigated in both surveys, 36 have seen stable population growth.

Holding more than a half of the country's wildlife species, Yunnan province has in recent decades adopted several conservation methods, such as plant cultivation, seed storage and even plant tissue culture techniques, to protect those endangered plants from extinction.

Sun Weibang, director of the Kunming Botanical Garden, said the concept of plant species with extremely small populations was developed by Chinese conservationists and first practiced in Yunnan province. "It was all started by a bag of seeds," Sun said in an earlier interview with China Daily.

Yunnan has invested 140 million yuan ($21.7 million) to safeguard flora over the past 15 years. By the end of 2019, the province had launched more than 120 projects and established 30 conservation areas for 61 plant species.

Through its conservation efforts, Sun's team saved a critically endangered Yangbi maple tree. In 2008, only five such trees were distributed across Yunnan, but today there are at least 4,000 growing in the wild. Similar efforts have been also made to save the Qiaojia five-needled pine, which is native to Yunnan's Qiaojia county.

When the species was discovered in 1990, only 34 trees were found growing wild. After years of conservation efforts, nearly 7,000 saplings or seedlings have been artificially propagated and cultivated.

While some species still maintain the ability to propagate in the wild, others remain on the edge of extinction, the survey said.

The surveyors could not find any examples growing wild of three plants: Panax stipuleanatus (a medicinally important plant endemic to China); Camellia micrantha (an endangered Camellia species); and Amomum petaloideum (an Amomum species endemic to China).

Another 98 species, accounting for 34.6 percent of the total number of plants in the survey, had populations of less than 5,000, according to the National Forestry Administration.

Of those, only one plant was found of the Carpinus putoensis Cheng, a species in the family Betulaceae, which is native to the Zhoushan archipelago in Zhejiang province.

"In general, plants with more than 5,000 sexually mature individuals in the wild can survive and maintain a stable population," the administration said in a statement. "Those 98 species are currently endangered, not only due to the limited population, but also the sparse distribution areas."

The survey also revealed that 115 plants have habitats of less than 100 hectares. This sees slow natural regeneration, fragile conditions for reproduction and a high risk of extinction.

The administration said the survey will help guide local forestry departments to develop future protection plans. "Either on-site or off-site, conservation is encouraged to be conducted under the regional construction plans of nature reserves or national parks," it said.

In January, the State Council announced plans to establish the country's first national botanical garden in Beijing. Development of the garden will focus on the protection of plants and scientific research.

The national botanical garden will also promote off-site conservation of plants and the systematic collection, preservation, high-level research into and sustainable utilization of plants.