Abstract
Invasion of western juniper (Juniperus occidentalis Hook.) into big sagebrush (Artemisia tridentata Nutt.) communities of eastern Oregon implies redistribution of nutrients among ecosystem components, with management implications as stands mature. To assess these effects, we measured biomass and nutrients in juniper trees of five size classes ranging in average age from 36 to 161 yr, and in understory vegetation. Understory was measured at 0.0, 0.5, 1, 2, and 4 canopy radii from the bole and in areas devoid of juniper ("no juniper"). Tree size and distance from boles had no effect on biomass or concentrations and amounts of nutrients in understory vegetation. Above-ground tree biomass increased with maturity from 18.4 kg for size class 1 to 741.4 g for class 5. Biomass accumulated rapidly (22.3 kg/tree/yr) between classes 2 and 3. Foliage comprised 41% of tree biomass in class 1 trees, but decreased to 15% for class 5 trees. Concomitantly, percentage of tree biomass in boles and live branches increased from 29 to 47%. From class 1 to class 5, amounts of nutrients increased as follows: nitrogen (N) from 89 to 2117 kg/tree; phosphorus (P) from 12 to 283 g/tree; and sulfur (S) from 10 to 294 g/tree. In open systems (intercanopy and "no juniper" areas), soil contained 89.9 to 99.8% of the organic carbon (Corg), N, P, and S of entire systems. For tree systems (areas occupied by juniper canopies), Corg, N, and S in aboveground biomass increased with increasing tree maturity, while P did not change. For the most mature trees, proportions of total system N, S and P allocated to the organic layer and trees was 30, 78, and 5%, respectively. Considering the N and S limited nature of these sites, a conservative harvest management approach that emphasizes retention of organic layers and tree foliage appears prudent
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Claims 16
Claim · model-written summary
Tree size and distance from boles had no effect on biomass or nutrient concentrations and amounts in understory vegetation.
Verbatim
t0“western juniper”
e1“Tree size and distance from boles had no effect on biomass or concentrations and amounts of nutrients in understory vegetation”
Claim · model-written summary
Above-ground tree biomass of western juniper increased with maturity.
Verbatim
t0“western juniper”
e2“Above-ground tree biomass increased with maturity from 18.4 kg for size class 1 to 741.4 g for class 5”
Claim · model-written summary
Biomass of western juniper accumulated rapidly, 22.3 kg per tree per year, between size classes 2 and 3.
Verbatim
t0“western juniper”
e3“Biomass accumulated rapidly (22.3 kg/tree/yr) between classes 2 and 3”
Claim · model-written summary
Foliage comprised 41% of tree biomass in class 1 western juniper trees.
Verbatim
t0“western juniper”
e4“Foliage comprised 41% of tree biomass in class 1 trees”
Claim · model-written summary
Foliage decreased to 15% of tree biomass in class 5 western juniper trees.
Verbatim
t0“western juniper”
e4“Foliage comprised 41% of tree biomass in class 1 trees”
e5“but decreased to 15% for class 5 trees”
Claim · model-written summary
Percentage of tree biomass in boles and live branches of western juniper increased from 29 to 47%.
Verbatim
t0“western juniper”
e6“percentage of tree biomass in boles and live branches increased from 29 to 47%”
Claim · model-written summary
Nitrogen (N) amounts in western juniper trees increased from size class 1 to class 5.
Verbatim
t0“western juniper”
e7“From class 1 to class 5, amounts of nutrients increased as follows: nitrogen (N) from 89 to 2117 kg/tree; phosphorus (P) from 12 to 283 g/tree; and sulfur (S) from 10 to 294 g/tree”
Claim · model-written summary
Phosphorus (P) amounts in western juniper trees increased from size class 1 to class 5.
Verbatim
t0“western juniper”
e7“From class 1 to class 5, amounts of nutrients increased as follows: nitrogen (N) from 89 to 2117 kg/tree; phosphorus (P) from 12 to 283 g/tree; and sulfur (S) from 10 to 294 g/tree”
Claim · model-written summary
Sulfur (S) amounts in western juniper trees increased from size class 1 to class 5.
Verbatim
t0“western juniper”
e7“From class 1 to class 5, amounts of nutrients increased as follows: nitrogen (N) from 89 to 2117 kg/tree; phosphorus (P) from 12 to 283 g/tree; and sulfur (S) from 10 to 294 g/tree”
Claim · model-written summary
In open systems, soil held 89.9 to 99.8% of entire-system organic carbon.
Verbatim
t0“western juniper”
e1“soil contained 89.9 to 99.8% of the organic carbon (Corg), N, P, and S of entire systems”
Claim · model-written summary
In open systems, soil held 89.9 to 99.8% of entire-system N, P and S.
Verbatim
t0“western juniper”
e1“soil contained 89.9 to 99.8% of the organic carbon (Corg), N, P, and S of entire systems”
Claim · model-written summary
Corg, N and S in aboveground biomass of tree systems increased with increasing tree maturity.
Verbatim
t0“western juniper”
e1“Corg, N, and S in aboveground biomass increased with increasing tree maturity, while P did not change”
Claim · model-written summary
P in aboveground biomass of tree systems did not change with increasing tree maturity.
Verbatim
t0“western juniper”
e1“Corg, N, and S in aboveground biomass increased with increasing tree maturity, while P did not change”
Claim · model-written summary
For the most mature trees, 30% of total system N was allocated to the organic layer and trees.
Verbatim
t0“western juniper”
e1“For the most mature trees, proportions of total system N, S and P allocated to the organic layer and trees was 30, 78, and 5%, respectively”
Claim · model-written summary
For the most mature trees, 78% of total system S was allocated to the organic layer and trees.
Verbatim
t0“western juniper”
e1“For the most mature trees, proportions of total system N, S and P allocated to the organic layer and trees was 30, 78, and 5%, respectively”
Claim · model-written summary
For the most mature trees, 5% of total system P was allocated to the organic layer and trees.
Verbatim
t0“western juniper”
e1“For the most mature trees, proportions of total system N, S and P allocated to the organic layer and trees was 30, 78, and 5%, respectively”