北亚热带马尾松净生产力对气候变化的响应

掌握马尾松生产力与气候变化的关系,特别是在马尾松自然分布的北界研究生产力对气候变化的响应具有重要意义,以马尾松自然分布北界的河南鸡公山国家级自然保护区内的老龄马尾松林作为研究对象,根据河南信阳的马尾松生物量与树高胸径的关系,利用样地调查和年轮宽度推算出过去的30a中的生物量和生产力动态,并用当地的温度、湿度、降水、光照以及帕尔默干旱度指数5项气候因子与生产力做相关分析,在此基础上用多元逐步回归得到了气候因子与生产力的回归方程。结果显示:鸡公山马尾松林生物量从1980年的59.00 t/hm²逐步增加到2009年的254.75 t/hm²,30a中平均年净生产力为6.64 t/hm²;气候分析表明年净生产力与气候因子关系较为密切:上年8月降水、当年2月温度、3月湿度以及10月的光照和温度与生产力正相关,当年5月光照、10月的降水和湿度与生产力负相关,当年2月到9月的PDSI都与生产力正相关,并且在6月的相关系数最高。研究表明,北亚热带的马尾松生产力的年际变化主要是气候因素引起的,受当年生长季的长短和生长季的土壤水分可用性限制,在未来该地区升温增湿的条件下马尾松林的生产力可能会升高。

Response of net productivity of masson pine plantation to climate change in North Subtropical Region

Masson pine is one of the main native plantation species in South China due to its fast and easy growing characteristics. Plantation area of the species increased dramatically and its growth was significantly impacted by climate change in past decades. The relationship between net productivity of masson pine plantation and climatic factors, especially for the plantation in its northern natural distribution boundary where masson pine growth is more sensitive to changes of climatic factors, is important to understand the response of its growth to climate change. We set six 20m×20m plots in 30 years old masson pine plantation in Jigongshan National Nature Reserve of Henan Province for doing this study. Both height and diameter at breast height (DBH) of all trees were measured and six cross increment cores at breast height of three sample trees were got in each plot. Tree ring widths of the dried and burnished cores were measured with Lintab tree ring analysis system. Annul diameters and heights of the sample trees were calculated using the annul tree ring widths. Biomass and net productivity of the old masson pine stands in the past 30 years were calculated based on the regressive equations between biomass and height and DBH in this area. After that, correlations between productivity and climate factors, including monthly and seasonal temperature, humidity, precipitation, sunshine and the Palmer Drought Severity Index (PDSI), were analyzed. The regressive equation between net productivity and climatic factors of the plantation in the area was established finally. The results indicated that biomass of the plantation increased more than three times in the past 30 years, from 59.00 t/hm² in 1980 to 254.75 t/hm² in 2009, and mean net productivity of the stand was 6.64 t · hm^-2 · a^-1. Net productivity was closely correlated with climatic factors. The effects of temperature, sunlight, precipitation and humidity on net productivity were different. There were positive correlations between productivity and precipitation in last August, mean temperature in February, precipitation in March, mean humidity in May, and mean temperature and total sunlight in October. There were negative correlations between productivity and total sunlight in May, precipitation and mean humidity in October. Productivity was correlative positively with PDSI from February to September. Seventy one percent of the changes of productivity could be interpreted by climatic factors. Generally, biomass of masson pine plantation in North Subtropical Region could accumulate as high as that in low-latitude region but net productivity in the region was much less than that in low-latitude region. Annual changes of net productivity were mainly caused by climatic factors, especially the length of growing season and soil water availability in growing season. It is implied that both biomass and mean net productivity of the plantations could increase in the future due to possible increase of temperature and precipitation in the North Subtropical Region.