Spatio-temporal variation of climate productivity of vegetation and its responses to climate change in three provinces of Northeast China.

Climate productivity is a key indicator reflecting carbon exchange of plant communities. Clarifying changes in climate productivity is of great significance for assessing the carbon sink function of ecosystems. We used the Miami and Thornthwaite-Memorial models to simulate temperature-, precipitation- and evapotranspiration-producti-vity in the three northeastern provinces based on temperature and precipitation data from 1971 to 2020. We used trend analysis, wavelet analysis, M-K test and regression analysis to explicitly analyze the spatial and temporal variations of climate productivity, and model the changing characteristics of evapotranspiration productivity under future climate change scenarios. We further explored the accuracy of the test for climate productivity in conjunction with data from <i>Pinus sylvestris</i> var. <i>mongolica</i> tree-ring data at 11 sampling sites in the three northeastern provinces. Results showed that the annual averages of temperature productivity (<i>Y</i>_T), precipitation productivity (<i>Y</i>_P) and evapotranspiration productivity (<i>Y</i>_E) in the three northeastern provinces during 1971-2020 were 777.84, 946.08, and 930.4 g·m^-2·a^-1, respectively. All the three types of climate productivity generally showed increasing trends. The increasing trend of temperature productivity was the most significant, increasing at a rate of 1.91 g·m^-2·a^-1, existence of 6, 10, 22 years major periodic, and had abrupt change in 1988. There were significant differences in the spatial distribution of climate productivity. Temperature productivity decreased from south to north, with overall increasing trend in climate tendency rates. Precipitation productivity and evapotranspiration productivity decreased from southeast to northwest, which was higher in the east than in the west. Their climate tendency rates showed a decreasing trend in most areas, with an increasing trend occurred in western Heilongjiang and northwestern Jilin. The water-heat ratios of climate productivity in the three northeastern provinces were generally banded with significant spatial variations, with the ratios ranging from 0.58 to 2.42. From north to south, it could be divided into areas that were more affected by precipitation (<i>Y</i>_P/<i>Y</i>_T>1.2), water-heat balance (<i>Y</i>_P/<i>Y</i>_T≈1), and more affected by temperature (<i>Y</i>_P/<i>Y</i>_T<0.8), respectively. The three climate productivities were generally consistent with change in the mean annual tree-ring width index of <i>P. sylvestris</i> var. <i>mongolica</i> at the 11 sampling sites, which was positively correlated, indicating that the modelled climate productivity was reliable. The correlation coefficients between temperature productivity and the width of the annual tree-ring of <i>P. sylvestris</i> var. <i>mongolica</i> decreased significantly with increasing latitude. Our results could improve the understanding of carbon sequestration capacity of vegetation associated with climate productivity in the three northeastern provinces, which would provide a scientific basis for the adaptation of vegetation to climate change and the prediction of future vegetation dynamics.