九龙江口红树林研究Ⅳ.秋茄群落的氮、磷的累积和循环

本文是福建九龙江口红树林生态系统研究的一个部分,主要讨论20年生秋茄群落的氮、磷含量及其生物循环。试验结果表明:秋茄群落现存量中,含有氮、磷总量分别为935.47和112.02公斤/公顷。其中地上部分别为582.26和70.47公斤/公顷;地下部分别为353.21和41.55公斤/公顷。该群落氮、磷元素生物循环中,年吸收量分别为213.31和21.75公斤/公顷;存留量分别为83.75和10.91公斤/公顷;归还量分别为129.52和10.84公斤/公顷。它们的氮含量均大于磷含量,周转期氮需7年比磷需10年为快。     

九龙江口红树林研究V.秋茄群落的氯的累积和循环

本文是福建省九龙江口红树林研究的一部分,主要讨论20年生秋茄(Kandelia candel) 群落氯元素的累积及其生物循环。试验结果表明,秋茄群落现存量中含有氯总量3864.13公斤／公顷：其中地上部为1287.75公斤／公顷,地下部为2576.38公斤／公顷。该群落氯元素生物循环中年吸收量为626.57公斤／公顷,归还量为271.31公斤／公顷,存留量为355.26公斤／公顷,周转期需14年。     

福建九龙江口秋茄红树林的生物量和六元素的累积与循环

本文讨论了20年生人工秋茄群落的生物量和氮、磷、钾、钠、钙、镁6种元素的累积及生物循环。结果表明,秋茄现存量为162.63吨/公顷,其中地上部为93.37吨/公顷,地下部为69.26吨/公顷;地下部占总量的42.59%。该群落含有氮、磷、钾、钠、钙、镁元素,总量分别为935.47、112.02、531.97、2100.35、772.91和526.57公斤/公顷;其中6元素生物循环中,年吸收量分别为213.31、21.75、109.15、353.50、174.86和89.30公斤/公顷,年归还量分别为129.15、10.84、59.37、160.18、103.28和40.42公斤/公顷,年存留量分别为83.79、10.91、49.78、193.32、71.58和48.88公斤/公顷;群落中6元素的周转期分别为7、10、9、13、8和13年。元素的周转期较陆生森林为短,是红树林的一个特点。     

九龙江口红树林研究Ⅱ.秋茄群落的钾、钠累积和循环

本文是福建九龙江口红树林生态系统研究的一个部分,主要讨论20年生秋茄群落的钾、钠的含量及其生物循环。试验结果表明:秋茄群落现存量中,含有钾、钠总量分别为531.97和2100.36公斤/公顷;其中地上部分分别为296.49和742.91公斤/公顷;地下部分分别为235.48和1357.45公斤/公顷。该群落钾、钠生物循环中年吸收量分別为109.15和353.50公斤/公顷·年,归还量分别为59.37和160.18公斤/公顷·年。存留量为49.78和193.32公斤/公顷·年。它的钠含量比钾含量大,周转期钾需9年比钠需13年为快。     

九龙江口红树林研究Ⅴ.秋茄群落的氯的累积和循环

本文是福建省九龙江口红树林研究的一部分,主要讨论20年生秋茄(Kandelia candel)群落氯元素的累积及其生物循环。试验结果表明,秋茄群落现存量中含有氯总量3864.13公斤/公顷:其中地上部为1287.75公斤/公顷,地下部为2576.38公斤/公顷。该群落氯元素生物循环中年吸收最为626.57公斤/公顷,归还量为271.31公斤/公顷,存留量为355.26公斤/公顷,周转期需14年。     

红海榄红树林的氮、磷积累和生物循环

本文讨论广西山口英罗湾中红海榄群落的氮、磷含量及其生物循环。结果表明,红海榄群落现存量中,含氮、磷总量分别为221.15和13.27g/m~2。其中地上部分别为134.90和8.73g/m~2;地下部分别为86.25和4.54g/m~2。该群落的氮、磷元素生物循环中,年吸收量分别为12.91和1.27g/m~2,年存留量分别为7.04和0.65g/m~2;年归还量分别为5.86和0.61g/m~2。富集率分别为1.11和1.60。群落各组分的氮含量均大干磷含量;周转期氮需38a,比磷(22a)慢。     

海南岛海莲红树林的钾钠元素的累积和循环

本文是海南东寨港红树林研究的一部分,主要讨沦55年生海莲林的K、Na元素的累积和生物循环。试验结果表明：在海莲群落现存量中,含有K、Na总量分别为669.9和2951.3kg／ha;其中地上部分别为425.6和908.9kg／ha,地下部分别为244.3和2042.4kg／ha。该群落的k、Na元素的生物循环中,年吸收量分别为89.6和204.4kg／ha,归还量为49.0和99.8kg／ha,存留量为40.6和104.6kg／ha。K的周转期为14年比Na30年为快。     

福建武夷山黄山松群落的氮、磷累积和循环

本文是福建武夷山森林生态系统研究的一部分,主要讨论黄山松（Pinustaiwanensis）群落的氮磷累积和循环。测定结果表明：（1）群落现存量中氮（N）、磷（P）的库量分别为925．844kghm-2和45．981kghm-2,其中地上部分别为719．438kghm-2（占总库量的77．706%）和35．534kghm-2占77.280％）,地下部分别为206．406kghm-2（占22．294％）和10．447kghm-2（占22.720％）;（2）N、P的生物循环中,年吸收量分别为65．344kghm-2和2627kghm-2,年存留量分别为37．019kghm-2和1．695kghm-2,年归还量分别为28．325kghm-2和0.932kghm-2;（3）氮、磷的富集率分别为1．324和1．083两者均大于1,说明该群落对N、P仍在不断累积。     

深圳福田红树林无瓣海桑+海桑群落N、P、K累积和循环

研究了深圳福田红树林无瓣海桑 +海桑群落的 N、P、K元素的累积和循环。结果表明 ,该群落 N、P、K元素的现存累积量分别为 :3 8694.92、 5 848.62、 5 0 861 .47mg/m2 ,其中地下部分分别占 2 8.5 9%、41 .77%、 42 .0 8%。该群落氮、磷、钾元素生物循环中 ,年吸收量分别为 :1 3 2 40 .0 95、 1 887.70 5、 2 0 73 6.1 1mg/m2 ;年归还量分别为 :62 70 .5 85、 979.1 75、 63 5 3 .948mg/m2 ;年存留量分别为 :6969.5 1、 90 8.5 3、 1 43 82 .1 62 mg/m2 ;周转期分别为 :7a、6a、9a。群落各组分的氮含量最高 ,磷含量最低。     

哀牢山北部木果石栎林的元素积累及循环

根据对哀牢山北部徐家坝地区木果石栎林化学元素的吸收、分布及其生物循环的研究结果表明,碳素在树干中含量最高,而其它元素的含量均以叶片最高,枝和根其次,树干最低。该森林群落中碳、氮、磷、钾、钙、镁、锰、钠、铝和铁元素的积累量达２６０３４６ｋｇ／ｈｍ＾２,其中乔木层的元素积累量占该群落元素总积累量的９８．５％,灌木层和草本层的元素积累量仅分别占１．３％和０．２％。在该群落中各元素的积累量以碳＞钙＞氮＞钾     

Bioproductivity and nutrient cycling in bamboo and acacia plantation forests

This study mainly aimed to investigate the bioproductivity and nutrient cycling processes in plantation forests of bamboo and acacia. In India, multipurpose tree (MPT) species are extensively planted to meet the increasing demand for fuel and industrial wood. The bioproductivity studies of bamboo showed that the total biomass increased with age (2.2 t/ha/year 1) up to six years (297.8 t/ha/year 6) and then decreased (15.6 t/ha/year 10). With acacia, the total biomass increased from 1.8 t/ha/(year 1) to 5.0 t/ha/ (year 3) and 10.9 t/ha/(year 5). In general the biomass increased with increase of diameter and height. Nutrient cycling in the plantation on an annual basis was worked out. A complete harvest of bamboo in 6 years removes 2341 kg/ha of nitrogen, 22 kg/ha of phosphorus, 2,653 kg/ha, of potassium, 1,211 kg/ha of calcium and 1,356 kg/ha of magnesium. A total harvest of above ground biomass of acacia in 3 years removes (kg/ha) 91.74 N, 2.53 P, 73.41 K, 110.45 Ca, 14.06 Mg, and in 4 years removes (kg/ha) 227.47 N, 7.34 P, 181.04 K, 284.15 Ca, and 38.89 Mg.     

模拟氮沉降对北京东灵山辽东栎群落林下植物物种多样性的影响

氮沉降是驱动生物多样性变化的重要因素之一。一般认为氮沉降会改变物种多样性, 而且在外源氮添加条件下, 禾草类植物和落叶灌木比杂类草和常绿灌木更具竞争优势。不过该结论更多是从高寒草甸和荒漠草原等生态系统中得到, 主要是针对同一生活型内植物之间的竞争关系, 不涉及不同生活型植物之间的相互作用, 并且由于草原和草甸等生态系统没有明显的垂直结构, 同一层次中植物的高度差异较小, 有可能高估了光照因素对植物的作用。因此从森林生态系统入手, 可以进一步阐述不同生活型植物对氮沉降的响应。本文以我国北方典型的落叶阔叶林——辽东栎(Quercus wutaishanica)林为研究对象, 设置CK (0 kg N·ha ^-1·yr ^-1)、N50 (50 kg N·ha ^-1·yr ^-1)和N100 (100 kg N·ha ^-1·yr ^-1) 3个梯度氮添加实验, 模拟氮沉降对温带森林生物多样性的影响。8年连续的氮添加实验结果显示: (1)氮添加显著降低了林下植物的物种丰富度和多样性, 改变了群落的物种组成; (2)氮添加提高了灌木植物的物种丰富度和多样性; 降低了草本植物的丰富度; (3)氮添加降低了禾草类植物的重要值, 提高了杂类草的重要值。该研究表明, 长期氮添加会显著改变林下植物的物种组成, 不同生活型植物对氮添加的响应亦有所差别。造成该现象的原因可能是由土壤环境变化(如养分含量提高, pH值下降)和植物获取光照能力强弱(如灌木植物获取光资源要多于草本植物)导致。     

Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments

Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.     

Retention of Inorganic Nitrogen by Epiphytic Bryophytes in a Tropical Montane Forest1

We developed and evaluated a model of the canopy of a tropical montane forest at Monteverde, Costa Rica, to estimate inorganic nitrogen (N) retention by epiphytes from atmospheric deposition. We first estimated net retention of inorganic N by samples of epiphytic bryophytes, epiphyte assemblages, vascular epiphyte foliage, and host tree foliage that we exposed to cloud water and precipitation solutions. Results were then scaled up to the ecosystem level using a multilayered model of the canopy derived from measurements of forest structure and epiphyte mass. The model was driven with hourly meteorological and event‐based atmospheric deposition data, and model predictions were evaluated against measurements of throughfall collected at the site. Model predictions were similar to field measurements for both event‐based and annual hydrologic and inorganic N fluxes in throughfall. Simulation of individual events indicated that epiphytic bryophytes and epiphyte assemblages retained 33–67 percent of the inorganic N deposited in cloud water and precipitation. On an annual basis, the model predicted that epiphytic components retained 3.4 kg N ha/yr, equivalent to 50 percent of the inorganic N in atmospheric deposition (6.8 kg N ha/yr). Our results indicate that epiphytic bryophytes play a major role in N retention and cycling in this canopy by transforming highly mobile inorganic N (ca. 50% of atmospheric deposition is NO^?₃) to less mobile (exchangeable NH⁺₄) and recalcitrant forms in biomass and remaining litter and humus.     

Woody Debris in the Mangrove Forests of South Florida1

Woody debris is abundant in hurricane‐impacted forests. With a major hurricane affecting South Florida mangroves approximately every 20 yr, carbon storage and nutrient retention may be influenced greatly by woody debris dynamics. In addition, woody debris can influence seedling regeneration in mangrove swamps by trapping propagules and enhancing seedling growth potential. Here, we report on line‐intercept woody debris surveys conducted in mangrove wetlands of South Florida 9–10 yr after the passage of Hurricane Andrew. The total volume of woody debris for all sites combined was estimated at 67 m³/ha and varied from 13 to 181 m³/ha depending upon differences in forest height, proximity to the storm, and maximum estimated wind velocities. Large volumes of woody debris were found in the eyewall region of the hurricane, with a volume of 132 m³/ha and a projected woody debris biomass of approximately 36 t/ha. Approximately half of the woody debris biomass averaged across all sites was associated as small twigs and branches (fine woody debris), since coarse woody debris >7.5 cm felled during Hurricane Andrew was fairly well decomposed. Much of the small debris is likely to be associated with post‐hurricane forest dynamics. Hurricanes are responsible for large amounts of damage to mangrove ecosystems, and components of associated downed wood may provide a relative index of disturbance for mangrove forests. Here, we suggest that a fine:coarse woody debris ratio ≤0.5 is suggestive of a recent disturbance in mangrove wetlands, although additional research is needed to corroborate such findings.     

Soil nitrogen dynamics in a holm oak forest

Soil nitrogen (N) dynamics were studied in a dense, holm oak (Quercus ilex ssp. ilex) stand in the Montseny mountains to determine annual and seasonal patterns of N availability and uptake in an undisturbed Mediterranean forest on acidic soil. Soil mineral N content, net N mineralization (NNM), and net nitrification (NN) were determined by monthly sampling at two soil depths followed by in situ incubation in polyethylene bags. NNM per unit of soil mass was much higher at 0–5 cm than at 5–20 cm (annual means 24 and 2.5 mg N/kg, respectively) but on an area basis NNM was similar at both depths. A total of 80 kg N/ha/yr were mineralized from the first 20 cm of soil. NN amounted to only 9% of the annual NNM (7.5 kg N/ha/yr) and it occurred only in the upper 5 cm. NNM was maximum in June and July, while the NN peaked in May. Despite favourable soil temperature and moisture, NNM was negative in autumn because of microbial immobilization. Seasonal and depth variations of NNM appeared to be controlled more by substrate quality than by organic matter quantity, temperature or moisture. NN was not limited by ammonium availability. Calculated N uptake amounted to 91 kg/ha yr, peaking in June and July. The investigated stand showed a moderately high N availability, but ammonium was the major form of mineral N supply for holm oak.     

Landslides significantly alter land cover and the distribution of biomass: an example from the Ninole ridges of Hawai'i

In the Ninole ridges of Hawai'i we investigated how landslides influence ecosystem development and modify land cover and the distribution of biomass. We estimated above and below-ground biomass, and N and P concentration in leaves (Metrosideros polymorpha) and very fine roots (all species), for vegetation developing on landslides of three age classes (young, < 18 yr; intermediate, 42 yr; and old ca. 124 yr) and on undisturbed soils (ca. 430 yr). The undisturbed soils were derived from ash underlain by basalt. To quantify changes in land cover and the distribution of biomass we combined our estimates of biomass with estimates of the area covered by each vegetation class. The latter estimates were obtained from the analysis and classification of color-infrared aerial photographs. Average above- and below-ground biomass for the herbaceous vegetation (young landslides) was 10.4 and 3.2 t/ha, whereas for the ohia-non ash forest (intermediate and old landslides) was 37.5 and 5.2 t/ha, respectively. For the ohia-ash forest (undisturbed sites), average above and below-ground biomass was 354.6 and 9.5 t/ha, respectively. Average foliar N for the herbaceous and ohia-non ash forest ranged between 0.80–0.84%, whereas root P between 0.056–0.040%, respectively. For the ohia-ash forest, average foliar and root P was 0.918% and 0.036%, respectively. Based on changes in vegetation cover during the last 430 yr, we estimated rate of disturbance at 15% per century or equivalently that 53 t/ha biomass per century exited through the system. The removal of ash-derived soils by landslides significantly alters successional trajectories and by doing so may be transforming the Ninole ecosystems in irreversible ways.