This chapter on nutrients is based on a series of Indian Central Himalayan (ICH) forests along an elevation gradient from foothills (300 m) to the treeline (>3300 m). In general soil properties changed monotonically (e.g. soil bulk density decreased) with elevation, but for subtropical chir pine forest patterns differ. Generally nutrient concentration in tree components was found in the following order: leaves >twigs >branches/bark>coarse roots >bole (stem) wood. Bark was 1.3 times (Ca) to 1.59 times (P) richer in nutrient concentration than stem wood. Nitrogen concentrations in stem wood of Himalayan forests are generally on higher side of the range given in the literature, making it a large nutrient reservoir. The prevalence of significant positive correlations in nutrient concentrations among the tree components across species suggests a great deal of functional coordination of nutrient allocations across disparate types of tissues. Thus, a species having high Ca concentration in leaf is likely to have high concentration of Ca in stem wood. The average N:P ratio in tree components across the ICH species ranged between 16.7 in coarse roots and 24.9 in twigs. Across the ICH forests total N mass in the ecosystem (vegetation + forest floor litter +30 cm deep soil) varied about two-fold from 5,079 kg ha−1 in chir pine to 11,768 kg ha−1 in tilonj oak forest, located at 2000 m. The percentage of total nitrogen mass in a forest ecosystem that occurs in vegetation,'decreases rapidly above 2600 m, from about 34.5% in kharsu oak forest to 7.6% in treeline birch forest and 2.71% in krummholz of R. campanulatum. Phosphorus (P) mass in vegetation ranged about 3.5-fold from 13.2 kg ha−1 in the treeline forest of R. campanulatum to 462 kg ha−1 in tilonj oak-dominated forest. Generally, herbs accounted for significantly higher percentage of nutrient uptake than shrubs, largely because of the greater production and nutrient concentration of herbs than shrubs. If we exclude the values of treeline forests and some exceptionally high values of old-growth oak forests, the N return through litterfall ranges between 56.1 and 83.3 kg ha−1 yr−1. Canopy interception of precipitation is higher in conifer forests (e.g. 34.1% is Cedrus deodara forest) than broad-leaved evergreen forests (e.g. 24.8% in Q. leucotrichophora forest. In the ICH forests, the nutrient input through precipitation is in the following order: Ca > K > Mg > N > P. The nutrient turnover time in these forests is short, closer to that of tropical forests than temperate forests: it ranged between 1.22 and 4.35 years across all forests and nutrients. The average resorption of N in the Himalayan species was 50.3%, based on 71 species. To conclude, holding large amount of nutrients the Himalayan forests is of great conservation value.

Tree Nutrient Concentration and Forest Nutrient Cycling

章节
发表日期：

2025年

查看全文

S. P. Singh

摘要

This chapter on nutrients is based on a series of Indian Central Himalayan (ICH) forests along an elevation gradient from foothills (300 m) to the treeline (>3300 m). In general soil properties changed monotonically (e.g. soil bulk density decreased) with elevation, but for subtropical chir pine forest patterns differ. Generally nutrient concentration in tree components was found in the following order: leaves >twigs >branches/bark>coarse roots >bole (stem) wood. Bark was 1.3 times (Ca) to 1.59 times (P) richer in nutrient concentration than stem wood. Nitrogen concentrations in stem wood of Himalayan forests are generally on higher side of the range given in the literature, making it a large nutrient reservoir. The prevalence of significant positive correlations in nutrient concentrations among the tree components across species suggests a great deal of functional coordination of nutrient allocations across disparate types of tissues. Thus, a species having high Ca concentration in leaf is likely to have high concentration of Ca in stem wood. The average N:P ratio in tree components across the ICH species ranged between 16.7 in coarse roots and 24.9 in twigs. Across the ICH forests total N mass in the ecosystem (vegetation + forest floor litter +30 cm deep soil) varied about two-fold from 5,079 kg ha−1 in chir pine to 11,768 kg ha−1 in tilonj oak forest, located at 2000 m. The percentage of total nitrogen mass in a forest ecosystem that occurs in vegetation,'decreases rapidly above 2600 m, from about 34.5% in kharsu oak forest to 7.6% in treeline birch forest and 2.71% in krummholz of R. campanulatum. Phosphorus (P) mass in vegetation ranged about 3.5-fold from 13.2 kg ha−1 in the treeline forest of R. campanulatum to 462 kg ha−1 in tilonj oak-dominated forest. Generally, herbs accounted for significantly higher percentage of nutrient uptake than shrubs, largely because of the greater production and nutrient concentration of herbs than shrubs. If we exclude the values of treeline forests and some exceptionally high values of old-growth oak forests, the N return through litterfall ranges between 56.1 and 83.3 kg ha−1 yr−1. Canopy interception of precipitation is higher in conifer forests (e.g. 34.1% is Cedrus deodara forest) than broad-leaved evergreen forests (e.g. 24.8% in Q. leucotrichophora forest. In the ICH forests, the nutrient input through precipitation is in the following order: Ca > K > Mg > N > P. The nutrient turnover time in these forests is short, closer to that of tropical forests than temperate forests: it ranged between 1.22 and 4.35 years across all forests and nutrients. The average resorption of N in the Himalayan species was 50.3%, based on 71 species. To conclude, holding large amount of nutrients the Himalayan forests is of great conservation value.