A Preliminary Study On The Biological And Environmental Characteristics Of Integrated Rice-carp Farming In Hani Terraced Fields

As a world intangible cultural heritage,Hani terraces are gradually concerned by people because of its spectacular sight.However,Hani terraces have high labor intensity and low income,resulting in many terraces gradually abandoned and damaged.Therefore,the protection of Hani terraces is extremely urgent.In recent years,the integrated rice fields aquaculture in China has developed rapidly,with significant social and ecological benefits.The ecological characteristics of Hani terraced integrated rice fields aquaculture system are not clear,which is not conducive to the scientific and rational development of terraced integrated rice fields aquaculture production.However,the altitude difference of Hani terraced fields is nearly 2000m,and the environmental characteristics of high and low altitude are very different,so the comprehensive cultivation of integrated rice fields aquaculture needs to be treated differently.In this study,water environment characteristics,macrozoobenthos community structure,food composition and characteristic odor of rice carp were studied in integrated rice-carp farming terraces with different altitudes(570m and 1840m)from May to August 2019 in Honghe County,Yunnan Province.The changing trends of density,biomass and dominant species of macrobenthos in different months and altitudes were determined.The food source and composition of Cyprinus carpio in integrated rice-carp farming system and the feeding demand of main food in different growth stages or seasons were determined.The differences of characteristic odor substances between Cyprinus carpio comprehensively cultivated in Hani terraced integrated rice-carp farming and conventional pond cultured Cyprinus carpio were clarified,and the characteristic odor substances and peculiar smell substances of Cyprinus carpio were found.the process and mechanism of safety,health and green ecology under the comprehensive cultivation mode of integrated rice-carp farming in Hani terrace were revealed.The main research results of this paper are as follows:1.Water environment characteristics of integrated rice-carp farming in Hani terraced fieldThere is a great difference in water environment between high altitude and low altitude integrated rice-carp farming terraces.The water temperature in low altitude terraces is nearly 5℃higher than that in high altitude terraces,the difference of dissolved oxygen is not significant,and the contents of total nitrogen and total phosphorus in low altitude terraces are higher than those in high altitude terraces.The integrated rice-carp farming at high and low altitudes showed significant nutrient retention effect.The actual retention rate of RET_f(P)>RET_f(N)in high altitude terraces,RET_f(P)>RET_f(N)in low altitude terraces,RET_f(N)>RET_f(N)in high altitude terraces,but RET_f(P)<RET_f(P)in low altitude terraces.The water quality at high altitude is better than that at lower altitude.2.Community structure characteristics of macrobenthos in integrated rice-carp farming system in Hani terraced fieldThe results of the study on the community structure of macrobenthos in the terraced fields of integrated rice-carp farming at high and low altitudes showed that Oligochaeta and Insecta are the main macrobenthic groups in high and low altitude terraces,and the species composition was significantly different(P<0.05).Rice pests of Chironominae and Tanytarsus were found in terraces at both high and low altitudes.In addition,the rice pest Pomacea canaliculata was also found at low altitudes.The present study showed that altitude and month were the key factors affecting the macrobenthic community structure of the Hani terraced integrated rice-carp farming system at different altitudes.At the same time,the feeding pressure of carp was also an important factor inducing the changes of the macrobenthic community structure,which reduced the pests biomass in the Hani terraced integrated rice-carp farming system.3.Food composition and characteristic odor of Cyprinus carpio in the integrated rice-carp farming in Hani terraced FieldThe results of food composition of Hani terraced integrated rice-carp farming and Cyprinus carpio showed that the food source of Cyprinus carpio was mainly composed of 6 phyla and 10 genera,and the relative abundance of food sources in gut samples varied with month and altitude.The relative abundance of Arthropod and Streptophyta in the gut contents of Cyprinus carpio in low altitude terraces was significantly higher than that in high altitude terraces(P<0.05).The relative abundance of Nematode and Chlorophyta at high altitude was significantly higher than that at low altitude(P<0.05).Cyprinus carpio in high altitude terraced fields mainly feed on Chlorella,nematodes,chlamydomonas,rice and Scenedesmus.In June,they mainly feed on nematodes and sheathed algae,and in August,they mainly feed on Chlorella and Oryza.Cyprinus carpio in high altitude terraced fields mainly feed on Chlorella,Necator,Oedogonium,Oryza and Scenedesmus.In June,they mainly feed on Necator and Scenedesmus,and in August,they mainly feed on Chlorella and Oryza.Cyprinus carpio in low altitude terraced fields mainly feed on Chironomus,Gieysztoria,Scenedesmus,Oryza and Lemna,while in June,they mainly feed on Chironomus and Lemna,and in August,they mainly feed on Oryza.Aldehydes,hydrocarbons,ketones,alcohols,acids,esters,amides,furans and other compounds were found in the meat of Cyprinus carpio cultured in terraced fields at high and low altitude.There are some differences in the number and types of odor substances among the samples from different locations.The differences of environment and food composition between high altitude and low altitude are the reasons that affect the meat volatile smell of Cyprinus carpio.The odor of volatile substances in terraced fields is better than that in ponds,and the water quality in high altitude is better than that in low altitudes.The odor of volatile substances in high altitude terraced fields is better than that in low altitude terraced fields.The study in this paper shows that the flavor of Cyprinus carpio produced by high altitude terrace is better than that at low altitude,and the Cyprinus carpio cultured in Hani terrace integrated rice-carp farming system has the characteristics of no pollution,no pollution and good quality.and the quality of Cyprinus carpio produced at high altitude is better.