Station director

 Yiping Zhang             professor

Assistant station director

 Yuhong Liu                professor

Members

 Chuangsheng Wu    professor

 Zhiyun Lu                   Assist. professor

 Handong Wen          Assist. professor

NSFC-Yunnan Joint Fund programme

Response of Yunnan’s typical forests to climate Change        (Yiping Zhang   2013-2016)

CAS

Carbon, nitrogen and water from the subtropical forest.          (Yiping Zhang   2011-2015)

Carbon sequestration rate and its potential in the grassland in Yunnan provience.       (Liqing Sha   2011-2015 )

MPNNFC

The key processes of carbon-nitrogen-water coupling cycles and biological regulation mechanisms in terrestrial ecosystem.        (Yiping Zhang   2013-2017)

NSFY

Evaluation the carbon and water vapor exchange in four subtropical forests based on the canopy temerature.       (Qinghai Song    2013-2016 )

1

Rubber plantations act as water pumps in tropical China. Whether rubber plantations have the role of water pumps in tropical Southeast Asia is under active debate. Fifteen years (1994–2008) of paired catchments water observation data and one year paired eddy covariance water flux data in primary tropical rain forest and tropical rubber plantation was used to clarify how rubber plantation affects local water resources of Xishuangbanna, China. Both catchment water observations and direct eddy covariance estimates indicates that more water was evapotranspired from rubber plantation (1137 mm based on catchment water balance, 1125 mm based on eddy covariance) than from the rain forest (969 mm based on catchment water balance, 927 mm based on eddy covariance). Soil water storage during the rainy season is not sufficient to maintain such high evapotranspiration rates, resulting in zero flow and water shortages during the dry season in the rubber plantation. Therefore, this study supports the idea that rubber plantations act as water pumps as suggested by local inhabitants.

2

Carbon sequestration ability in the rubber forest. The regrowth of tropical secondary forests and plantations cannot offset the carbon release caused by tropical deforestation, consequently determining net carbon losses on tropical lands. However, large uncertainties remain in relation to this assumption. Here, we used a biometric method to estimate the net dry matter production and net ecosystem production in a rubber forest, the most widespread plantation type in tropical Southeast Asia. According to biometric estimates made during the study, the ecosystem was a carbon sink (790 gC m-2 yr-1). Net ecosystem carbon fluxes were measured by the eddy covariance method. The carbon budget estimated using the FluxNet procedure (904 gC m-2 yr-1) was closer to the biometric estimates in comparison to a method based on data measured during neutral atmospheric conditions. Overall, when considering the whole life cycle, including deforestation of the prior-existing tropical forest, the hypothesis of plantations serving as large carbon sinks is not supported by our study.

3

Influence of interactions between litter decomposition and rhizosphere activity on soil respiration and on the temperature sensitivity.The aims were to identify the effects of interactions between litter decomposition and rhizosphere activity on soil respiration and on the temperature sensitivity of soil respiration in a subtropical forest in SW China. Four treatments were established: control (CK), litter removal (NL), trenching (NR) and trenching together with litter removal (NRNL). Soil CO2 efflux, soil temperature, and soil water content were measured once a month over two years. Soil respiration was divided into four components: the decomposition of basic soil organic matter (SOM), litter respiration, root respiration, and the interaction effect between litter decomposition and rhizosphere activity. A two-factor regression equation was used to correct the value of soil CO2 efflux. We found a significant effect of the interaction between litter decomposition and rhizosphere activity (RINT) on total soil respiration, and RINT exhibited significant seasonal variation, accounting for 26 and 31%of total soil respiration in the dry and rainy seasons, respectively. However, we found no significant interaction effect on the temperature sensitivity of soil respiration. The temperature sensitivity was significantly increased by trenching compared with the control, but was unchanged by litter removal. Though the interaction between litter decomposition and rhizosphere activity had no effects on temperature sensitivity, it had a significant positive effect on soil respiration. Our results not only showed strong influence of rhizosphere activity on temperature sensitivity, but provided a viable way to identify the contribution of SOM to soil respiration, which could help researchers gain insights on the carbon cycle.

4

Soil respiration in an old-growth subtropical forest: Patterns, components, and controls .The patterns, components, and controls of soil respiration in an old-growth subtropical forest were investigated using an automatic chamber system. We measured soil respiration in three treatments (control, trenching, litter removal) over 15 months. The annual total soil respiration (1248 gC m–2 yr–1) showed considerable spatial variation (coefficient of variation = 27.8%) within the forest. Thirty samples were required to obtain results within 10% of the mean value at a 95% confidential level. A distinctive cosine-like diel pattern of soil respiration was observed; the time lag between gross primary production and soil respiration at this scale was calculated to be 4–5 h. Seasonality of soil respiration was strong (1 mmolm–2 s–1 near the end of winter; 6 mmol m–2 s–1 in midsummer). No time lag was discerned between gross primary production and soil respiration at the seasonal scale. Soil temperature at 5 cm below surface can explain most (>91%) of the observed annual variation in soil respiration. The apparent respiration temperature sensitivity index (Q10) was 3.05. The lowest Q10 value was observed in winter, when soil moisture was low. Soil respiration was overestimated by a Q10 function during both dry and wet periods. The relative contributions of soil organic matter (RSOM), litterfall decomposition (RL), and root respiration (RR) to total soil respiration are 65.25%, 18.73%, and 16.01%, respectively; the temperature sensitivity of these components differ: RL (Q10 = 7.22)>RSOM (2.73)>RR (1.65). This relationship between Q10 values for litter respiration, soil organic matter decomposition, and root respiration still holds after minimizing the confounding effect of moisture. A relatively constant substrate supply and/or thermal acclimation could account for the observed low-temperature sensitivity in root respiration. Given the high carbon stocks and fluxes, the old-growth subtropical forests of China seem important in the global carbon budget and climate change.