针叶形质特征与马尾松对松突圆蚧抗性的关系

通过对松突圆蚧不同抗性程度的马尾松未受害针叶和受害针叶的针叶长度、叶鞘长、叶鞘松紧度、含水率、相对含水率和容重的测定，研究发现：马尾松针叶长度与其对松突圆蚧的抗性成反比，马尾松针叶的容重与其对松突圆蚧的抗性成正比，叶鞘长、叶鞘松紧度与抗虫性不相关。

干旱和遮荫对马尾松幼苗生长和光合特性的影响

为探究马尾松对干旱和遮荫胁迫的生理响应规律和适应机制,以2年生马尾松幼苗为对象,设置对照(CK)、模拟干旱(DR)、遮荫(LL)以及干旱与遮荫的交互处理(DRLL)4种环境,研究干旱和遮荫对马尾松幼苗的生长和光合生理特性的影响。结果表明:(1)在干旱、遮荫和二者的交互处理下,马尾松幼苗的基径和株高增长量均显著减小,且二者的交互处理加重了干旱和遮荫单一处理下的减小趋势,二者交互作用的影响符合"相互作用理论"。(2)在干旱处理下,针叶长度和比叶面积减小,净光合速率、蒸腾速率、气孔导度和细胞间隙CO2浓度显著降低,水分利用效率显著增加,光合色素含量基本不变。(3)在遮荫处理下,针叶长度和比叶面积增大,净光合速率、蒸腾速率、气孔导度显著降低,光合色素含量显著增加,水分利用效率和细胞间隙CO2浓度基本未发生改变。(4)二者的交互处理下,针叶长度、比叶面积减小,净光合速率、蒸腾速率和气孔导度显著降低,且降低程度大于干旱单一处理,光合色素含量显著增加,但其增加程度小于遮荫单一处理。说明干旱和遮荫均能抑制马尾松植株的生长,但其光合生理特性在干旱和遮荫胁迫下分别表现出不同的响应特征。在干旱处理下,通过牺牲针叶长度和比叶面积、调节气孔导度达到保水目的来适应干旱环境;在遮荫处理下,通过增大针叶长度、比叶面积和光合色素含量来响应遮荫环境。在二者的交互处理下,干旱胁迫导致马尾松针叶长度、比叶面积和气孔导度的减小趋势不仅未因遮荫环境而得到缓解,而且还削弱了对光合色素的合成能力,因此,二者的交互作用会进一步加重对马尾松生长的抑制。

Vegetation-based bioindication of humus forms in coniferous mountain forests

Humus forms, especially the occurrence and the thickness of the horizon of humified residues （OH）, provide valuable information on site conditions. In mountain forest soils, humus forms show a high spatial variability and data on their spatial patterns is often scarce. Our aim was to test the applicability of various vegetation features as proxy for OH thickness. Subalpine coniferous forests dominated by Picea abies （L.） H. Karst. and Larix decidua Mill. were studied in the Province of Trento, Italian Alps, between ca. 900 and 22o0 m a.s.1. Braun-Blanquet vegetation relevds and OH thickness were recorded at 152 plots. The vegetation parameters, tested for their suitability as indicators of OH thickness, encompassed mean Landolt indicator values of the herb layer （both unweighted and cover-weighted means） as well as parameters of vegetation structure （cover values of plant species groups） calculated from the releves. To our knowledge, the predictive power of Landolt indicator values （LIVs） for humus forms had not been tested before. Correlations between OHthickness and mean LIVs were strongest for the soil reaction value, but indicator values for humus, nutrients, temperature and light were also significantly correlated with OH thickness. Generally, weighting with species cover reduced the indicator quality of mean LIVs for OH thickness. The strongest relationships between OH thickness and vegetation structure existed in the following indicators： the cover of forbs （excluding graminoids and ferns） and the cover of Erieaeeae in the herb layer. Regression models predicting OH thickness based on vegetation structure had almost as much predictive power as models based on LIVs. We conclude that LIVs analysis can produce fairly reliable information regarding the thickness of the OH horizon and, thus, the humus form. If no releve data are readily available, a field estimation of the cover values of certain easily distinguishable herb layer species groups is much faster than a vegetation survey with consecutive indicator value analysis, and might be a feasible way of quickly indicating the humus form.