Effects of soil warming,precipitation exclusion,and their interaction on fine root respiration and its relationship with fine root morphology in Chinese fir
Plant root respiration,especially fine root respiration,indicates the level of root tissue metabolism,supplying energy,such as ATP,crucial for root nutrient uptake and contributing significantly to the carbon balance of forest ecosystems.Despite its pivotal role,the response of root respiration to the combined effects of global warming and reduced precipitation remains unclear.This study conducted a two-factor manipulative experiment involving soil warming and precipitation exclusion.The treatments included control(CT),soil warming by 5 ℃(W),precipitation exclusion by 50％(P),and soil warming+precipitation exclusion(WP).We utilized Chinese fir(Cunninghamia lanceolata)seedlings at Sanming Forest Ecosystem National Field Scientific Observation and Research Station in Sanming,Fujian,China.The specific respiration rate of fine roots(0-1 mm and 1-2 mm diameter class)of Chinese fir seedlings was measured using Oxytherm liquid-phase oxygen electrodes,with the morphological characteristics of fine roots determined simultaneously.The effects of soil warming,precipitation exclusion,and their interactions on specific respiration rate and its correlation with root morphological characteristics were analyzed.The results showed that:(1)the interaction between soil warming and precipitation exclusion had a significant effect on the specific surface area and tissue density of fine roots,with the average specific surface area of fine roots in the WP treatment being 31.2％lower than that in the W treatment and the average tissue density of fine roots in the WP treatment being 26.4％higher than that in the CT treatment.The average tissue density of fine roots in the WP treatment was 60.9％higher than that in the W treatment.In addition,the tissue density of the 1-2 mm roots under the P treatment was significantly higher than that under the non-P treatment.(2)No interaction was observed between increased temperature and reduced precipitation on the specific respiration rate of fine roots.The specific respiration rate of 1-2 mm roots under P treatment was significantly lower than that under non-P treatment;however,P treatment had no significant effect on the specific respiration rate of 0-1 mm fine roots.This could be attributed to the precipitation exclusion treatment,increased tissue density of transported roots,and improved water security.(3)A significant positive correlation was found between fine root specific respiration rate and specific root length,which was not affected by soil warming,precipitation exclusion,or their interaction.Notably,the specific root respiration rate of 1-2 mm fine roots was mainly reduced by precipitation exclusion.This reduction was attributable to the increase in the tissue density of 1-2 mm fine roots,a response to decreased precipitation aimed at improving water transport capacity.In addition,soil warming,precipitation exclusion,and their interactions did not change the relationship between specific root respiration rates and the morphological characteristics of fine roots.The stable correlation between fine root respiration rate and fine root morphological characteristics can be used to predict changes in root respiration rate under climate change.
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