| Global warming is a global issue of common concern in the international community,increased warming and CO2 concentration are the two major features of climate change in the future,will be on the carbon cycle of terrestrial ecosystem plays a vital role.The subtropical evergreen broad-leaved forest is one of the important areas of forest carbon sequestration in China and the world,so the study of the future climate warming on tropical forest ecosystem carbon cycle effect has important significance,and will provide the theoretical basis for us to predict the future changes in the terrestrial ecosystem under climate change.This study plots based on forest ecology Fujian Sanming system and global change research station-Sanming Chenda state-owned forest observation point(26°19?N,117°36?E),with Cunninghamia lanceolata seedlings as the research object,setting the Above-ground temperature increase(AW),Below-ground warming(BW),Above-belowground temperature(ABW)and control(CK).We focused on the effects of soil warming and atmospheric warming on the leaf carbon metabolism.The Effects of different temperature treatments on the photosynthesis of the leaves,and the change of respiration of leaves;the response of photosynthesis to the increase of CO2 concentration in Cunninghamia lanceolata leaves under different temperature treatments;and further analysis of the blade under different matrix characteristics change and its coupling with the leaf carbon mtabolism.To better respond to global climate change,explore the impact of Climate warming on tropical forest ecosystem in the future.The main results are as follows:1.Response of Cunninghamia lanceolata leaves to different ways of increasing temperatureThere was a single peak curve between photosynthesis and temperature of Cunninghamia lanceolata.The photosynthesis of Cunninghamia lanceolata increased with the increase of temperature at the optimum temperature(the temperature below the maximum photosynthetic rate).But above the optimum temperature,the photosynthetic rate decreased with the increase of temperature.In winter(January),compared with CK,ABW?AW?BW increased by 58.66%?42.89%?35.23%,respectively?In spring(April),compared with CK;ABW?AW?BW increased by 15.56%?2.90%? 27.70%;In summer(July),the photosynthetic rate of ABW was the lowest,the photosynthetic rate of BW and CK increased by 21.29%?21.28%,respectively;in autumn(October),the photosynthetic rate of CK was the lowest,The photosynthetic rate of ABW?AW?BW increased by 13.42?9.43%?15.56%,respectively,But all decreased compared with that in summer.There was a positive correlation between respiration and temperature in Cunninghamia lanceolata leaves,and there was a positive correlation between respiration and temperature in Cunninghamia lanceolata leaves.The respiration was relatively slow with the increase of temperature at low temperature,but it would rise rapidly when the temperature was too high,but the long-term warming would make the respiration of leaves adapt to certain temperature and make the respiration value lower than that of the control.2.Response of Cunninghamia lanceolata leaves to different CO2 concentrationsThe photosynthesis of Current year birth Cunninghamia lanceolata needles was a significant positive correlation with the concentration of CO2.Compared to the control,warming significantly increased the photosynthetic capacity of the leaves of Cunninghamia lanceolata,while increasing temperature also increased the maximum rate of carboxylation and electron transfer rate,but there was little difference between seasons.3.Diurnal variation of photosynthesis in Cunninghamia lanceolata leavesCunninghamia lanceolata leaves the diurnal variation of photosynthesis has obvious seasonal variation.In the winter season,low temperature of Cunninghamia lanceolata leaves the diurnal variation of photosynthesis showed single peak curve pattern and did not appear the phenomenon of midday depression of photosynthesis,but in the summer season,when the temperature is higher in needles of the diurnal variation of photosynthesis and light curve in Shuangfeng mode with obvious "noon break"phenomenon,basically changes with time and the photosynthesis showed the first increase and then slowly increased and then decreased,the midday depression of photosynthesis occurred in the 14h.4.Changes of unstructured carbohydrates in Cunninghamia lanceolata leavesDifferent temperature treatment increased matrix leaves,on the Cunninghamia lanceolata leaf temperature increase soluble sugar and starch was the highest;in different seasons,the soluble sugar of Cunninghamia lanceolata is highest in winter,lowest in summer,but the starch content was the opposite.The starch content in leaves and photosynthesis were positively correlated(P<0.05),while soluble sugar and has no significant relationship;but the starch,soluble sugar and respiration has a negative correlation(P<0.05).5.Changes of the content of C?N?P in leaves of Cunninghamia lanceolataFound on the stoichiometry of different temperature treatments in leaves of Cunninghamia lanceolata,leaf photosynthesis and leaf N content was negatively correlated with C/N,but has a positive correlation;and for respiratory comparison,we found that the respiration correlated positively with the content of P,but with C/N and N/P was negatively correlated.To sum up,in the winter after the leaves of Cunninghamia lanceolata warming treatment of photosynthetic ability is far higher than that of the control,and the respiration is relative decline,but the warming treatment of Cunninghamia lanceolata leaf photosynthetic capacity was lower than contrast in the summer,the respiration declined.There was a significant positive correlation between photosynthetic rate and CO2 concentration in Cunninghamia lanceolata leaves under different temperature treatments(P<0.05).The study on diurnal variation of photosynthesis and photosynthetic depression found in cold winter there is no midday depression of photosynthesis in high summer.The research results will provide important reference for understanding of the comprehensive system under different warming treatment of Cunninghamia lanceolata leaf physiological substrates change it provides a reference for us to predict the change of ecosystem in the future with climate change. |
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