森林生态系统叶片暗呼吸时空动态及其影响因子

作为森林生态系统一个重要的呼吸通量,叶片呼吸在森林碳循环中扮演着重要的角色。开展叶片呼吸的机理及其影响因子研究,有助于构建大气和植被之间的呼吸通量模型,预测分析气候变化对森林生态系统生产力和碳源汇功能的影响。通常采用Li - 6400光合测定系统和LAI - 2000树冠分析仪测定森林生态系统叶片呼吸速率。叶片呼吸是一个复杂的生物化学过程,受到大气温度、CO₂浓度、土壤水分、叶片寿命、叶龄、比叶面积、叶片氮含量等多种因子的影响。叶片呼吸的日变化通常呈单峰曲线,与温度变化大体一致; 生长季早期和晚期的呼吸速率通常高于中期; 叶片在冠层着生位置影响其呼吸速率,冠层上部叶片的呼吸速率要高于冠层下部叶片。今后叶片呼吸研究应围绕以下4个关键问题:1) 模型构建时需要考虑叶片呼吸的温度驯化;2) 叶片呼吸在昼夜交替时内在调节机制;3) 从叶片呼吸到冠层呼吸的尺度转化;4) 加强和完善叶片呼吸影响因子研究。     

松潘生态修复模式区生物多样性与稳定性研究

九寨-黄龙世界自然遗产地位于我国西部典型的山地生态脆弱区,自2001年以来松潘县在退耕还林工程进行了不同树种配制模式的实践,共计营造了12个生态经济林模式.它们分别为:1.枸杞,2.沙棘,3.山桃+云杉,4.山杏+云杉,5.云杉,6.西蜀丁香+陇东海棠,7.云杉+阿根廷柳,8.云杉+青杨,9.阿根廷柳,10.阿根廷柳+青杨,11.青杨,12.山杏+阿根廷柳模式.通过对这12个模式群落与各层次物种多样性的分析比较,发现绝大多数模式木本层多样性并不高,而草本层则物种数多为20种左右,香农威纳指数都达到2.0以上,因而,群落总体多样性很可观.运用Godron M稳定性测定方法检验其生态稳定性表明:各模式的生态稳定性与理论上20/80的稳定点尚有相当距离;其大小依次为:1.枸杞,2.沙棘,4.山杏+云杉,6.西蜀丁香+陇东海棠,10.阿根廷柳+青杨,12.山杏+阿根廷柳,5.云杉,8.云杉+青杨,7.云杉+阿根廷柳,11.青杨,9.阿根廷柳,3.山桃+云杉,这表明模式构建后仍处在较脆弱的状态.稳定性与其多样性之间的拟合也表明稳定性与多样性并无多少明显相关,甚至还有呈现负相关的趋势.这预示着多样性与稳定性之间不存在简单的线性关系,而是可能存在一个多样性阈值.

Abstract：

The World Natural Heritage-Jiuzaigou & Huanglong-is located in the eco-vulnerablele areas of West China. Since 2001, a total of 12 reconstruction models of the degraded landscape in the eco-vulnerable areas have been implemented in Songpan County, i. e. 1) Lycium chinense; 2) Hippophae rhamnoides;3) Amygdalus davidiana + Picea asperata ; 4) Armeniaca sibirica + P. asperata; 5) P. asperata; 6)Syringa komarowii +Maluskansuensis; 7) P. asperata + Salix argentinensis; 8) P. asperata+ Populus cathayana; 9) S. argentinensis; 10) S. argentinensis + P. cathayana; 11) P. cathayanaand 12) A.sibirica+ S. argentinensis. An analysis of both horizontal and vertical species diversity in these 12 models showed that there were generally poor species richness and diversity in the woody layer. In contrast, the herb layer of most models possessed considerable diversity, with about 20 species and a Shannon-Weiner index of over 2.0. In addition, most models possessed sound species diversity, contributed by diversity in the herb layers. Estimation of bio-stability with M. Godron stability method demonstrated that the ecostability of each model fell quite apart from the theoretic stable point (20/80), being in the sequence of L.chinense > H. rhamnoides > A. sibirica+ P. asperata > S. komarowii + M. kansuensis> S. argentinensis + P. cathayana> A. sibirica + S. argentinensis > P. asperata > P. asperata + Populus cathayana > P. asperata + S. argentinensis > P. cathayana > S. argentinensis > Amygdalus davidiana + P. asperata, indicating that these models remained in their fragile status. Simulation between their species diversity and ecological stability also indicated that little, if any, simple linear correlation existed between them and, sometimes, even a negative correlation was shown, suggesting that there may be a threshold of biodiversity other than a simple linear relationship between diversity and stability.