Abstract
Forests in low-latitude (0° N–30° N) regions are important for greenhouse gas sequestration. They harbor around 25% of vegetation carbon stocks. The productivity of these forests is expected to change as the global climate changes. They may absorb less greenhouse gasses, with negative effects on the global climate. However, little is known about how exactly these forests will respond to climate change. Here, we focus on the largest pine forests in low-latitude forests areas in southwest China. These forests have experienced rapid climate warming over the past 60 years. We collected tree-ring cores from two naturally occurring key afforestation pine tree species: Pinus yunnanensis Franch. and Pinus armandii Franch. in Baoshan and Lijiang of Yunnan. We used basal area increment (BAI) to examine the productivity trends of these two species over long-time scales, and Partial Least Squares regression analysis together with Pearson correlation analysis to identify the critical climate periods for the growth of these two species. We found that: (1) regional pine tree productivity began to decline at the beginning of this century. (2) The radial growth of both species had the strongest positive correlation with the spring Palmer Drought Severity Index (PDSI) and precipitation and the strongest negative correlation with spring temperatures. (3) Climate responses differ by species with higher positive correlations between tree-ring width, PDSI, and precipitation in P. armandii than in P. yunnanensis at similar locations. (4) Climate responses differ by location with higher positive correlations between tree-ring width and PDSI in Lijiang than in Baoshan for P. yunnanensis. Our results suggest that spring moisture availability is the main limiting factor for pine tree growth, especially for P. yunnanensis in Lijiang and P. armandii in Baoshan. Future regional warming and warm-induced drought conditions may have negative effects on the growth of pine trees. These results provide reference data for the sustainable management of pine forests in low-latitude regions of southwest China and may be useful in assessing the sustainable carbon sink ability of pine forests in this region under climate change.
Highlights
Future climate change is likely to influence the productivity of the world’s forests [1]
Those results suggest that the growth of P. yunnanensis in Lijiang is more sensitive to environmental changes, followed by the growth of P. armandii in Baoshan
We found that the basal area increment (BAI) value of pine trees significantly increased until the beginning of this century and displayed a significantly decreasing trend (Figure 4)
Summary
Future climate change is likely to influence the productivity of the world’s forests [1]. Forests 2020, 11, 446 as forests play an important role in the global carbon cycle by absorbing atmospheric CO2 and storing it as carbon sinks [3]. Forests in low-latitude regions (0◦ N to 30◦ N) should be studied, since they account for only about 10% of total global forested area but contain about 25% of the vegetation carbon stocks [1]. Considering the critical role played by low-latitude forests in the global carbon cycle, it is necessary that we gain a better understanding of their growth trends and how these respond to climate change [1]
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