基于MaxEnt模型的重庆市茶树适生区预测及锗富集转运特性分析

Prediction of suitable tea growth area and analysis of germanium enrichment and transport characteristics in Chongqing based on MaxEnt model

  • 摘要: 【目的】预测重庆市茶树适生区,分析茶树对锗的富集转运特性,为重庆市优质富锗茶叶的生产提供参考。【方法】收集重庆市307个茶树分布位置(包括295个人工种植茶园和12株古茶树)和19个环境变量数据,通过MaxEnt模型对茶树适生区进行等级划分,并分析各环境变量的贡献率和置换率,采用刀切法检验影响茶树分布的主要环境变量。采集重庆市南川区茶树的幼叶、老叶、枝干和根系,测定锗含量并计算富集系数和转运系数,分析富锗茶叶生产潜力。【结果】19个环境变量对重庆市茶树适生区预测均有影响,其中最冷月份最低气温的贡献率最高,降水量季节变化的置换率最高;刀切法检验结果表明,影响重庆市茶树分布的环境变量主要为年平均气温、最冷季度平均气温、最冷月份最低气温、最湿季度平均气温、最干燥季度平均气温。重庆市茶树适生区可划分为4种等级,高适生区和非适生区面积较小,而中适生区和低适生区面积较大,其中南川区大部分地区属于中适生区,少部分属于低适生区和非适生区,极少部分属于高适生区。在南川区随机采集古茶树幼叶和人工种植茶园的茶树幼叶、老叶、枝干、根系,经测定发现人工种植茶园的茶树幼叶锗含量(平均值0.0058 mg/kg)高于古茶树幼叶(平均值0.0047 mg/kg),人工种植茶园的茶树老叶锗含量(平均值0.0119 mg/kg)高于幼叶。茶树对锗的富集系数仅为1.41,从根系到枝干、从根系到老叶、从根系到幼叶的转运系数分别为0.32、0.30、0.14。在南川区茶树中适生区选取土壤锗含量较高的5个地点人工种植茶园,采集茶树叶片测定锗含量,结果发现茶树老叶锗含量(0.0292~0.2840 mg/kg)高于随机采集样品。虽然茶树对锗的富集能力较弱,但以位于茶树适生区和富锗土壤分布区的人工种植茶园茶树老叶为材料较易制成富锗茶叶。【建议】合理规划重庆市茶树种植区,在高适生区、中适生区发展茶树种植;充分利用富锗土壤资源,加快富锗茶叶生产。

     

    Abstract: 【Objective】To predict the suitable areas for tea tree growth in Chongqing,and investigate the accumulation and translocation characteristics of germanium(Ge)in tea trees,which could provide reference for the production of high-quality and Ge-rich tea in Chongqing.【Method】Data on the distribution of 307 tea tree locations(including 295 artificially planted tea gardens and 12 ancient tea trees)and 19 environmental variables in Chongqing were collected. The MaxEnt model was used to classify the suitability levels of tea tree growth areas,and the contribution rate and replacement rate of each environmental variable were analyzed. The Jackknife method was employed to identify the main environmental variables affecting tea tree distribution. Young leaves,old leaves,branches and roots were collected from Nanchuan District,Chongqing. The germanium content was measured,and the accumulation coefficient and translocation coefficient were calculated to analyze the potential for germanium-rich tea production.【Result】All 19 environmental variables had an impact on the prediction of suitable tea tree growth areas in Chongqing,the lowest temperature in the coldest month owned the highest contribution rate,the seasonal variation in precipitation owned the highest replacement rate. The Jackknife detection indicated that the main environmental factors affecting the distribution of tea trees in Chongqing were annual average temperature,average temperature in the coldest quarter,the lowest temperature in the coldest month, average temperature in the wettest quarter,and the average temperature in the driest quarter. The tea tree suitable growth areas in Chongqing could be divided into 4 grades. Highly suitable areas and non-suitable areas were relatively small, while medium suitable areas and low suitable areas were larger. In Nanchuan District,most areas were classified as medium suitable areas,with a small part belonging to low suitable areas and non-suitable areas,and only a very small part belonging to highly suitable areas. In Nanchuan District,young leaves of ancient tea trees and young leaves,old leaves, branches,and roots of tea trees from artificially planted tea gardens were randomly collected. The measurements revealed that the germanium content in young leaves from the artificially planted tea gardens(0.0058 mg/kg on average)was higher than that from ancient tea trees(0.0047 mg/kg on average),and the germanium content in the old leaves from tea gardens(0.0119 mg/kg on average)was higher than that in the young leaves. The enrichment coefficient of germanium in tea trees was only 1.41,while the transport coefficients of germanium from the roots to the branches,from the roots to the old leaves,and from the roots to the young leaves were 0.32,0.30,0.14 respectively. Five artificial tea garden locations with relatively high soil germanium content in the suitable growth area of tea trees in Nanchuan District were selected to collect tea tree leaves for the determination of germanium content. The results showed that the germanium content in the old leaves of tea trees(0.0292-0.2840 mg/kg)was higher than that of randomly collected samples. Although tea plants had relatively weak ability to accumulate germanium,germanium-rich tea could be easily made from the old leaves of artificially planted tea gardens located in the suitable growth areas of tea trees and the distribution areas of germanium-rich soil.【Suggestion】Reasonably plan the tea planting areas in Chongqing,and develop tea tree cultivation in the highly suitable areas and medium suitable areas;fully utilize the germanium-rich soil resources to accelerate the production of germanium-rich tea.

     

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