腐烂等级、径级对典型阔叶红松林红松倒木物理化学性质的影响

Effects of decay classes and diameter classes on physico-chemical properties of Pinus koraiensis log in a typical mixed broadleaved-Korean pine forest

倒木是森林生态系统的重要组成部分,在地力维护、生物多样性保持以及碳(C)和养分循环等方面具有重要意义,但倒木物理化学性质随其腐烂等级和径级而变化。为了深入理解腐烂等级和径级对倒木物理化学性质的影响,该研究以典型阔叶红松林的建群种——红松(Pinus koraiensis)的倒木为研究对象,将其每个腐烂等级(I–V)下的倒木分为4个径级(径级i≤10.0 cm、径级ii 10.1–30.0 cm、径级iii 30.1–50.0 cm、径级iv>50.0 cm),研究了不同腐烂等级、径级及两者交互作用对倒木心材和边材物理化学性质的影响。结果表明:心材和边材具有相似的变化规律。倒木心材和边材含水率随着腐烂等级增加而增加,而木材密度随腐烂等级和径级的增加均呈下降趋势;边材C含量以及心材和边材的氮(N)、磷(P)含量随腐烂等级增加呈上升趋势,心材N、P含量随径级增加呈先增加后减少的趋势;纤维素含量随腐烂等级增加呈下降趋势,而木质素含量呈上升趋势,纤维素和木质素含量随径级增加没有明显变化规律。倒木含水率与C、N、P、木质素含量(除心材P含量)显著正相关,与纤维素含量显著负相关;木材密度与C、N、P、木质素含量显著负相关,与纤维素含量显著正相关。由此可见,倒木物理化学性质受不同腐烂等级和径级的影响有各自的变化规律,且倒木的物理性质(含水率和木材密度)是影响化学含量变化的重要因素。

Aims Log is an important component for most of forest ecosystems. It plays crucial roles in maintaining soil fertility, sustaining biodiversity and cycling of carbon （C） and nutrient. However, physico-chemical properties of logs vary with decay classes and diameter classes. Our objective was to study effects of decay classes and diameter classes on physico-chemical properties of logs in a typical mixed broadleaved-Korean pine forest in northern China.Methods In this study, logs of Pinus koraiensis were chosen as it was the constructive species in the typical mixed broadleaved-Korean pine forest. Logs of P. koraiensis at each decay classes （I-V） were divided into four diameter classes, including diameter class i ≤ 10.0 cm, diameter class ii： 10.1-30.0 cm, diameter class iii： 30.1-50.0 cm, and diameter class iv 〉 50.0 cm. Then, we explored effects of different decay classes, diameter classes and their interactions on the physico-chemical properties of logs for both the heartwood and sapwood.Important findings The results showed that the physico-chemical properties of heartwood and sapwood generally exhibited similar variations. Their moisture content both increased with an increasing decay class, whereas wood density both decreased with an increased decay class and diameter class. The carbon concentrations of the sapwood showed a trend of gradual increasing during decomposition, and there was an accumulation in nitrogen （N） and phosphorus （P） concentrations of the heartwood and sapwood with an increased decay class, simultaneously. Only N and P concentrations of the heartwood increased and then decreased with an increasing diameter class. The cellulose content decreased with an increasing decay class. In contrast to the cellulose, the lignin content increased with an increased decay class. However, cellulose and lignin contents exhibited no dis- tinct trend among diameter classes. The moisture content of logs had a significant positive correlation with C, N, P concentrations and lignin content （except P concentrations of the heartwood）, but had a significant negative correlation with the cellulose content （p 〈 0.05）. The wood density was negatively correlated with C, N, P concentrations and the lignin content, but it was positively correlated with the cellulose content （p 〈 0.05）. Therefore, physico-chemical properties of logs had unique patterns along both decay classes and diameter classes, and the physical properties of logs （the moisture content and wood density） were important factor affecting the variations of their chemical contents.