Erythroxylum is a perennial herb of the genus Sage in the family Poaceae native to the Atlantic coast of the Americas, where it grows mainly on vast beaches and estuarine bays between mean sea level and average high tide. In 1979, in order to replace the short plant and low biomass of rice grass, China introduced this species, after that, the mutual flower rice grass formed a population along the coast of China and spread widely through natural forces such as artificial promotion and introduction and trend. Nowadays, erythroxylum has become the salt marsh plant with the widest distribution area in China's coastal tidal flats.
Melee is listed as an invasive species
Why is it that the rice grass has expanded so rapidly in our country? This is related to the strong adaptability and tolerance of matinee to different environmental climates.
Melee is a widely salinized plant that grows widely in subtropical to temperate intertidal zones. Erythroxylum grows best on silt beaches in the estuary area. The highly developed ventilation tissue of melaleuca alternifolia can help it adapt well to the environmental conditions of long-term flooding.
Reciprocal rice grass has a strong reproductive ability, its sexual reproduction has a very high reproductive coefficient, and it can bear millions of seeds per square meter of mutually flowered rice grass. The vegetative propagation of interfluidic rice grass is to expand the population through its rhizomes, and a single plant of interfluidic rice grass can be expanded to up to 222 plants in a 9-month period.
It is also a highly competitive carbon tetrafluorite plant with high photosynthetic efficiency, rapid growth, population density and community biomass, and a single plant can grow up to 3 meters. So far, China has not found indigenous predators and other constraints that can control the growth and spread of the erythrophyllum population.
Reciprocal rice grass not only occupies a large area of silt-quality light beaches in China, squeezing the ecological space of local beach vegetation, but also threatens the coastal aquaculture industry and the maritime industry. Therefore, as early as 2003, melaleuca has been included in the first 16 alien invasive species blacklist in China, and is also recognized as one of the 100 most dangerous invasive species in the world.
Positive ecological effects of corrugated rice grass
After nearly 30 years of research and debate in the scientific community, the current cognition and positioning of mutually flowered rice grass is more rational, which can not simply notorietize this alien species, but also needs to fully understand its positive and negative ecological effects.
From the perspective of positive ecological effects, the root system of interfluidic rice grass is developed, the plant is thick, and a good "biological soft embankment" can be formed after continuous filming, which can play a very good role in eliminating waves and revetment. Field test studies have shown that when a 5-meter-high wind wave passes through a 100-meter-wide interflower rice grass belt, the wave suppression capacity of the grass belt is as high as 97%, which is more than 10 times the wave suppression capacity of mangroves.
Interfluilleine rice grass also has a strong siltation promotion function. When the tide carrying sediment enters the interfluille rice grass beach, the flow rate is significantly reduced, and a large amount of sediment is deposited in the grass beach, making the beach surface gradually silt up. Experiments in the Dongtai beach area of Jiangsu Province showed that the silt height of the beach surface of the interfluille rice grass was 48.5 cm to 52.1 cm in four years, while the silt length speed of the guangtan in the same period was 10.5 cm to 16.9 cm. Jiangsu coastal rice grass salt marsh accumulates nearly 9 million cubic meters of silt every year than Guangtan, and adds more than 1,000 hectares of land every year, which has considerable benefits in promoting dredging.
Erythroxylum has a longer growing season, a larger leaf area index, a higher rate of net photosynthesis, and a large aboveground and subsurface biomass, which makes its carbon sequestration and nitrogen fixation significantly higher than that of native plants reed and sea triangular cane grass. Moreover, the amount of litter in the lower part of the meadow and its degradation rate are much lower than those of reeds and sea cane grass, which makes the carbon sequestration ability of the meadow stronger.
Reciprocal rice grass can also absorb and enrich nutrients such as organic matter, nitrogen, phosphorus and other nutrients in sewage, carry out metabolic transformation in the body, and convert pollutants in water into nutrients in plants, thereby eliminating pollution caused by aquaculture and oil production and reducing the possibility of red tide. In addition, the body of interfluille is also rich in bioactive substances and essential trace elements, which have good health value, and proper development can produce good economic benefits.
Negative ecological effects of alternating rice grass
From the perspective of negative ecological effects, the tall and dense monoculture of interfluillet rice grass expands with tenacious vitality and strong fertility, seriously encroaching on the habitat of other native vegetation, resulting in a significant decline in the diversity of wetland vegetation species. In many parts of The Yangtze River Estuary Bay in Jiangsu Province, Jiuduansha Wetland in Shanghai, alternating rice grass invaded the community of indigenous plants sea triangular cane grass, causing the sea triangular cane grass to eventually disappear, forming a large single alternate flower rice grass community.
By rapidly promoting sediment accumulation and beach silting, the erythropocea can quickly change the hydrological pattern of the estuary, accelerate the siltation speed of the tidal flats and port areas, and then affect the navigation and flood discharge of ships, forcing the port area to move down in advance, causing huge economic losses.
After the mutual flower rice grass seizes the light beach, it will also change the topography and soil physical and chemical properties of the original light beach area, so that the mud snails, four-horned clams, clams and other beach shellfish organisms that originally lived here will disappear or migrate, on the one hand, it directly threatens the shellfish breeding industry along the beach, on the other hand, it will also affect the survival of birds with the light beach habitat as the main habitat and foraging place, resulting in a decrease in the number of bird populations, especially the impact on wading birds is more obvious. In the Red-crowned Crane Nature Reserve in Yancheng, Jiangsu Province, the good growth and high density of the Erythrum rice grass belt make it difficult for the red-crowned crane to move, thereby reducing its value as a red-crowned crane habitat. In addition, patches of interfluille rice grass have reduced the number of geese, wild ducks, cygnets and white-naped cranes that feed on bulbs, small nuts and rhizomes of reeds, and also affected the survival of birds such as egrets that feed on benthic animals.
In view of the current development trend of interfluillet rice grass in China, it is the general trend to control the crazy expansion of the erythrophyte population. However, most of the control methods currently in use, including physical harvesting, chemical weeding, biological control and species substitution, are limited in effectiveness and costly. Therefore, under the current situation, how to manage the mutual flower rice grass, implement ecological control, inhibit its negative ecological effect, give full play to its positive ecological effect, and maximize its ecological benefits are problems that need serious consideration and urgent need to be solved.
(Author Affilications:Qingdao Institute of Marine Geology, China Geological Survey)
Source: China Natural Resources Daily
Editor-in-Charge: Song Xi