| Forest litter is a key link in the process of energy flow and nutrient cycling of for est ecosystem, and has played an important role in the effect of regulating ecosystem energy flow and nutrient cycling and utilization, on primary productivity and maintain ing soil nutrient pools and other aspects. Litter decomposition is the main way of for est ecosystem material cycle and energy conversion. Different kinds of plant litter will not only affect the decomposition rate but also affect the dynamic change of nutrient elements in the process of decomposition while they mix. This study takes the Pinus massoniana and Cinnamomum camphora in Hunan Forest Botanical Garden as the research objects, mixing the litter in the ratio of 25%,50%,75% and 100% (masson pine litter accounted for 25%, ratio 3/4; masson pine, camphor tree litter occupied 50% each, ratio 1/2; masson pine litter took up 25%, camphor tree litter took the rest, ratio 1/4), and loaded the litter branch, leaf in litter decomposition bags, then retrieved the litter samples in different time intervals to measure the weightlessness rate, decomposition rate and nutrient elements release quantity during the decomposition process. The results showed that:(1) Masson pine year’s litter content (3.83 t-hm-2-a"1) is larger than camphor year’s litter content (3.70 t-hm-2·a-1), the dynamics of a month in Masson pine and camphor showed the characteristic of irregular variation. The maximum litter content of Masson pine appeared in November (0.85t-hm"2), and the camphor’s was in August (0.68t·hm-2). As for litter branch, the maximum litter content of Masson pine was appeared in August (64.23kg·hm-2), camphor’s was in November (102.66kg·hm-2); as for litter leaf, the maximum litter content of Masson pine was appeared in November (653.22kg-hm"2), and the camphor’s was in August (428.04kg·hm-2); as for litter fruit, the maximum litter content of Masson pine was appeared in January (75.92kg-hm"2), and the camphor’s was in April (42.55kg·hm-2); as for other litter, the maximum litter content of Masson pine was appeared in April (51.51 kg·hm-2), and the camphor’s was in May (136.05kg·hm-2). This two kinds of forests have clear rhythm while littering, the content is maximum in autumn, higher than other seasons significantly.(2) After 1 year decomposition, litter weightlessness rate of Masson pine and camphor was respectively:camphor litter leaf (61.97%)> camphor litter branch (61.23%)>masson pine litter leaf (51.18%)>masson pine litter branch (50.91%). Decomposition rate:camphor litter leaf (1.051g·g-1-a-1)>camphor litter branch (0.964g·g-1·a-1)>masson pine litter leaf (0.756g-g-1·a-1)>masson pine litter branch (0.709g·g-1·a-1). It takes 0.66-0.98 year to decompose 50% of litter of Masson pine and camphor, and 2.85～4.22 years for the decomposition of 95% of that.(3) During the decompositions of masson pine and camphor litter, the release range of C is 53.52%～112.47%; N’s release range is 40.40%～20.84%; P’s release range is 3.9%～140.85%; K’s release range is 28.47%～119.28%; Ca’s release range is 22.42%～148.64%; Mg’s release range is 11.88%～134.49%. C/N’s release range is 17.51-91.16, N/P’s release range is 5.63～27.80. After 360 days since the decomposition began, the C/N ratio of masson pine’s litter branch and leaf is down to 55.70% and 124.83%, while camphor’s is 95.96% and 176.70%; the N/P ratio of masson pine’s litter branch and leaf is down to 120.99% and 71.66%, while camphor’s is 94.25% and 175.13%.(4) During the decompositions of litter branch and leaf mixed with different ratios, the decrement is:masson pine’s litter (78.77%,73.03%)>3/4 proportion (76.27%,65.08%)> 1/2 proportion (67.42%,60.30%)> 1/4 proportion (58.63%, 59.80%)>camphor’s litter (48.82%,53.09%). The measured values of mixed litter branch in 3/4 proportion,1/2 proportion and 1/4 proportion are 7.44%,3.3%,6.67% lower than expectations values of that. The measured values of mixed litter leaf in 1/4 proportion is 5.9%lower than its expectations values. The four kinds of combinations have promotion effect, the decomposition speed is faster when mixed than separated.(5) After 360 days’decomposition, element C, the measured value of litter leaf in ratio 3/4, litter leaves in ratio 1/2 and litter branch and leaf in ratio 1/4 are larger than expectations values,6.12%,14.92%,0.39%,1.35% respectively; element P, the measured value of litter branch in ratio 1/2 is 16.88% larger than the expectations value; element K, the measured values of litter leaf in ratio 3/4, litter leaf in ratio 1/2 are 3.21% and 15.04% larger than expectations values; element Ca, the measured values of litter branch in ratio 1/4, litter leaf in ratio 3/4 are larger than expectations values,16.42% and 25.67% respectively, element Mg, the measured value of litter branch in ratio 3/4, litter leaf in ration 3/4, litter branch in ratio 1/4 and litter leaf in ratio 1/4 are larger than the expectations values,46.17%,42.19%, 44.43% and 35.39% respectively, all of these are positive influence, the measured values of rest types of mixtures are less than the expectations values, the measured values of element N in different mixed proportions are less than the expected value, and it is an negative effect. |
PDF Full Text Request